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TITLE 35: ENVIRONMENTAL PROTECTION
SUBTITLE C: WATER POLLUTION
CHAPTER II: ENVIRONMENTAL PROTECTION AGENCY
PART 370
ILLINOIS RECOMMENDED STANDARDS FOR SEWAGE WORKS
SUBPART A: INTRODUCTION
Section
370.100 Purpose
370.110 Scope and Applicability
370.115 Incorporations by Reference
SUBPART B: ENGINEERING REPORTS, PLANS AND SPECIFICATIONS
Section
370.200 General
370.210 Engineering Report
370.211 Design Flows
370.220 Detailed Engineering Plan Drawings Format
370.230 Specifications to Accompany Detailed Engineering Plan Drawings
370.240 Revisions to Approved Plans and Specifications
370.250 Operation During Construction
370.260 Engineers Seal
SUBPART C: DESIGN OF SEWERS
Section
370.300 General Considerations
370.310 Design Basis
370.320 Details of Design and Construction
370.330 Manholes
370.340 Sewers in Relation to Streams
370.350 Protection of Water Supplies
SUBPART D: SEWAGE PUMPING STATIONS
Section
370.400 General
370.410 Design
370.420 Suction-Lift Pump Stations
370.430 Submersible Pump Stations - Special Considerations
370.440 Alarm Systems
370.450 Emergency Operation
370.460 Instructions and Equipment
370.470 Force Mains
SUBPART E: SEWAGE TREATMENT WORKS
Section
370.500 Plant Location
370.510 Quality of Effluent
370.520 Design
370.530 Plant Details
370.540 Plant Outfalls
370.550 Essential Facilities
370.560 Safety
370.570 Laboratory
SUBPART F: PRELIMINARY TREATMENT
Section
370.600 General Considerations
370.610 Screening Devices
370.620 Grit Removal Facilities
370.630 Pre-Aeration
SUBPART G: SETTLING
Section
370.700 General Considerations
370.710 Design Considerations
370.720 Sludge and Scum Removal
370.730 Protection and Service Facilities
370.740 Imhoff Tanks
370.750 Septic Tank - Tile System
SUBPART H: SLUDGE PROCESSING, STORAGE AND DISPOSAL
Section
370.800 General
370.810 Process Selection
370.820 Sludge Thickening
370.830 Anaerobic Sludge Digestion
370.840 Aerobic Sludge Digestion
370.845 High pH Stabilization
370.850 Sludge Pumps and Piping
370.860 Sludge Dewatering
370.870 Sludge Storage and Disposal
SUBPART I: BIOLOGICAL TREATMENT
Section
370.900 Trickling Filters
370.910 Rotating Biological Contactors (Repealed)
370.915 Rotating Biological Contactors
370.920 Activated Sludge
370.930 Waste Stabilization Ponds and Aerated Lagoons
370.940 Intermittent Sand Filtration for Secondary Treatment
SUBPART J: DISINFECTION
Section
370.1000 General
370.1010 Disinfection Process Selection
370.1020 Chlorine Disinfection
370.1021 Dechlorination
370.1022 Ultraviolet Disinfection
370.1030 Chlorine Gas Supply (Repealed)
370.1040 Piping and Connections (Repealed)
370.1050 Housing (Repealed)
370.1060 Respiratory Protection Equipment (Repealed)
370.1070 Application of Chlorine (Repealed)
370.1080 Sampling and Testing
SUBPART K: TERTIARY FILTRATION
Section
370.1100 Applicability
370.1110 Type
370.1120 High Rate Filtration
370.1130 Low Rate Intermittent or Periodically Dosed Sand Filters
SUBPART L: NUTRIENT REMOVAL
Section
370.1200 Phosphorus Removal by Chemical Treatment
370.1210 Ammonia Control
APPENDIX A Table No. 1 - Resident Occupancy Criteria
APPENDIX B Table No. 2 - Commonly Used Quantities of Sewage Flows From
Miscellaneous Type Facilities
APPENDIX C Table No. 3 - Air Test Table for Sanitary Sewer Leakage
Testing*
APPENDIX D Figure No. 1 - Design of Sewers - Ratio of Peak Flow to
Daily Average Flow
APPENDIX E Figure No. 2 - Primary Settling
APPENDIX F Figure No. 3 - B.O.D. Removal Single Stage Trickling Filter
Units Including Post Settling - No Recirculation Included
APPENDIX G Figure No. 4 - Break Tank Sketch for Potable Water Supply
Protection
APPENDIX H Old Section Numbers Referenced (Repealed)
AUTHORITY: Implementing Sections 4 and 39 and authorized by Section 39 of
the Environmental Protection Act [415 ILCS 5/4 and 39].
SOURCE: Adopted at 4 Ill. Reg. 14, p. 224, effective March 31, 1980;
codified at 8 Ill. Reg. 19430; recodified at 18 Ill. Reg. 6375; amended at
21 Ill. Reg. 12444, effective August 28, 1997.
NOTE: In this Part, superscript numbers or letters are denoted by
parentheses; subscript are denoted by brackets.
SUBPART A: INTRODUCTION
<BSection 370.100 Purpose>>
The purpose of this Part is to establish criteria for the design and
preparation of plans and specifications for wastewater collection and
treatment systems.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.110 Scope and Applicability>>
a) These design criteria apply to conventional design concepts for
wastewater collection and treatment systems. Where
non-conventional concepts or approaches to collection and
treatment, particularly for very small systems, are being
considered, the Agency should be contacted for any design guidance
that may be available.
b) In evaluating plans and specifications for new processes, the
Agency will consider the specific information submitted with the
design in accordance with the provisions of Section 370.520(b) for
situations involving new process evaluation.
c) These criteria are intended to establish limiting values for those
aspects of plans and specifications which the Agency evaluates and
to promote, as far as practicable, uniformity of practice
throughout the State. For projects with a design flow average of
over 100 million gallons per day (mgd), the application of
specific design parameters in these criteria should be evaluated
on a unit-by-unit basis to insure optimum design performance and
cost effective construction. In applying these criteria,
consideration must be given to the characteristics (including
current water quality) and uses of the receiving stream in order
to insure compliance with the applicable regulations of the
Illinois Pollution Control Board (hereinafter "IPCB"). Users
should also be cognizant of Federal requirements.
d) The word "shall" is used where practice is sufficiently
standardized to warrant compliance with specific requirements, or
where safeguarding the public health or protecting water quality
justifies such definite action. Words such as "should",
"recommended" or "preferred" indicate desirable procedures or
methods with deviations subject to individual project
consideration.
e) Definitions of terms and their use are intended to be in
accordance with the GLOSSARY - WATER AND WASTEWATER CONTROL
ENGINEERING, jointly prepared by the American Public Health
Association (APHA), American Water Works Association (AWWA),
American Society of Civil Engineers (ASCE), and Water Environment
Federation (WEF). The units of expression are in accordance with
the WEF Manual of Practice Number 6, Units of Expression for
Wastewater Treatment.
(Source: Added at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.115 Incoporations by Reference>>
a) The following materials are incorporated by reference:
1) "Glossary: Water and Wastewater Control Engineering", Joint
Editorial Board of the American Public Health Association,
American Society of Civil Engineers, American Wasteworks
Association, American Pollution Control Federation (1969).
2) ASTM Standards - American Society for Testing and Materials,
100 Bar Harbor Drive, West Conshohoken PA:
ASTM C12-95 -- "Standard Practice for Installing Vitrified
Clay Pipe Lines", Vol. 04.05, Chemical Resistant Materials,
Vitrified Clay, Concrete, Fiber-Cement Products; Mortars;
Masonry (1996).
ASTM C969-94 -- "Standard Practice for Infiltration and
Exfiltration Acceptance Testing of Installed Precast Concrete
Pipe Sewer Lines", Vol. 04.05, Chemical Resistant Materials,
Vitrified Clay, Concrete, Fiber-Cement Products; Mortars;
Masonry (1996).
ASTM C124 -- "Standard Test Method for Concrete Sewer
Manholes by the Negative Pressure (Vacuum) Test", Vol. 04.05,
Chemical Resistant Materials, Vitrified Clay, Concrete,
Fiber-Cement Products; Mortars; Masonry (1996).
ASTM D2321 -- "Standard Practice for Underground Installation
of Themoplastic Pipe for Sewers and Other Gravity-Flow
Applications", Vol. 08.04, Plastic Pipe and Building Products
(1996).
3) "AWWA Standard for Installation of Ductile-Iron Mains and
their Appurtenances", ANSI/AWWA C600-93 (1994) American
Wasteworks Association, 6666 Quincy Avenue, Denver CO 80235.
4) "National Electrical Code Handbook", 7th ed. (1996), National
Fire Protection Association, 1 Batterymarch Park, P.O. Box
9101, Quincy MA 02269-9101.
5) "Standard Specifications for Water and Sewer Main
Construction in Illinois", 5th ed. (1996), Illinois Society
of Professional Engineers, Illinois Municipal League, the
Association General Contractors of Illinois, Underground
Contractors Association.
6) "Standard Specifications for Road and Bridge Construction"
(1997), Illinois Department of Transportation.
7) Manuals of Practice, Joint Task Force of the Water
Environment Federation (WEF) (formerly Water Pollution
Control Federation), 601 Wythe Street, Alexandria VA
22314-1994 and the American Society of Civil Engineers
(ASCE), 345 East 47th Street, New York NY 10017-2398:
"Gravity Sanitary Sewer Design and Construction", WPCF Manual
of Practice (MOP) No. FD-5 (1982).
"Units of Expression for Wastewater Management", WEF Manual
of Practice (MOP) No. 6 (1982).
"Design of Municipal Wastewater Treatment Plants", vol. 1,
WEF Manual of Practice (MOP) No. 8 (1992).
b) The incorporations cited in this Section include no further
editions or amendments.
(Source: Added at 21 Ill. Reg. 12444, effective August 28, 1997)
SUBPART B: ENGINEERING REPORTS, PLANS AND SPECIFICATIONS
<BSection 370.200 General>>
The criteria in this Subpart B are intended to be the technical basis for
the preparation of the engineering reports and plans and specifications for
waste collection and treatment works. For project planning requirements,
applicable State and Federal guidance, regulations and statutes shall be
consulted.
a) Grant Projects
For projects that will be funded by Stateor Federal grants,
applicable regulations, policy and guidance documents will govern
the non-technical requirements and shall be used in the facility
planning process.
b) Non Grant Projects
For those projects which are not covered by applicable State or
Federal project planning requirements or for those other projects
in which there is no project planning guidance in the applicable
State or Federal regulations or statutes, the project planning
guidance set forth in Section 370.112 shall be utilized.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.210 Engineering Report>>
a) General
1) The engineering report assembles basic information; presents
design criteria and assumptions; examines alternate projects
including preliminary layouts and cost estimates; describes
financing methods, user charges and operation and maintenance
costs; reviews organizational and staffing requirements;
offers a conclusion with a proposed project for client
consideration; and outlines official actions and procedures
to implement the project.
2) The concept, factual data and controlling assumptions and
considerations for the functional planning of sewerage
facilities are presented for each process unit and for the
whole system. These data form the continuing technical basis
for the detailed design and preparation of construction plans
and specifications.
3) Architectural, structural, mechanical and electrical designs
are usually excluded. Sketches may be used to aid in
presentation of a project. Outline specifications of process
units, special equipment, etc., may be included.
4) Engineering reports are not required for sewer extensions or
sewer connections, but shall be required for the following
projects:
A) New treatment plants.
B) Expansion or major modification of existing plants.
C) New collection systems.
D) Major upgrading of existing collection systems.
b) Content
The engineering report shall:
1) Prescribe design period and projected population.
2) Describe the specific service area for immediate
consideration and indicate possible extensions and ultimate
use.
3) Present data and information on anticipated quantities of
flow and wastewater constituents. Data from comparable
existing installations may be used to develop the design
basis of the proposed facilities if data for the project
under design cannot be obtained in accordance with procedures
set forth in Subparts C, D and E of these standards.
4) Specify the scope and nature of collection system including
pump stations and force mains for immediate and ultimate
service areas.
5) Discuss various treatment alternatives with reference to
optimum treatability and other relevant factors.
6) Develop a detailed basis of design for the recommended
treatment process.
7) Indicate compliance with applicable effluent limitations and
discuss the impact of the project on receiving waters.
8) Indicate compliance with the requirements of the Illinois
Groundwater Protection Act [415 ILCS 55].
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.211 Design Flows>>
The following flows shall be identified in the basis of design for sewers,
lift stations, sewage treatment plants, treatment units and other
wastewater handling facilities.
a) Design Average Flow
The design average flow is the average of the daily volumes to be
received for a continuous 12-month period of the design year,
expressed as a volume per unit of time.
b) Design Maximum Flow
The design maximum flow is the largest volume of flow to be
received during a continuous 24-hour period, expressed as a volume
per unit of time.
c) Design Peak Hourly Flow
The design peak hourly flow is the largest volume of flow to be
received during a one hour period, expressed as a volume per unit
of time.
d) Design Peak Flow
The design peak flow is the instantaneous maximum flowrate to be
received.
(Source: Added at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.220 Detailed Engineering Plan Drawings Format>>
a) General
Detail plans shall contain as necessary, the following:
1) Plan views.
2) Elevations.
3) Sections and supplementary views which, together with the
specifications and general layouts, facilitate construction
of the works.
4) Dimensions and relative elevations of structures.
5) Location and outline form of equipment.
6) Location and sizing of piping.
7) Water levels.
8) Ground elevations.
9) Location and identification of all private and public water
supply wells (refer to Section 370.210(b)(8)), structures and
facilities (refer to Section 370.350(b)(1)(A)).
10) Descriptive notations as necessary for clarity.
b) Plans of Sewers
1) General Plan
Except as provided in subsection (b)(1)(C) below, a
comprehensive plan of the existing and proposed sewers shall
be submitted for projects involving new sewer systems or
substantial additions to existing systems. This plan shall
show the following:
A) Geographical Features
i) Topography and elevations: Existing or proposed
streets and all streams or water surfaces shall be
clearly shown. Contour lines at suitable intervals
should be included.
ii) Streams: The direction of flow in all streams, and
high and low water elevations of all water surfaces
at sewer outlets and overflows shall be shown.
iii) Boundaries: The boundary lines of the
municipality and the sewer district or area to be
sewered shall be shown.
B) Sewers
The plan shall show the location, size and direction of
flow of all existing and proposed sanitary and combined
sewers draining to the treatment works concerned.
C) Sewer Atlas
The comprehensive plan of the existing sewers described
above need not be submitted in each case if the system
owner has furnished the Agency a copy of its sewer atlas
showing the information required by subsection (b)(1).
The project submittal, however, must include all the
proposed work, and must be accompanied by a location map
showing the proposed project and the route of the outlet
sewer to the receiving plant, where necessary.
2) Detail Plans
Detail plans shall be submitted. Profiles should have a
horizontal scale of not more than 100 feet to the inch and a
vertical scale of not more than 10 feet to the inch. Plan
views should be drawn to a corresponding horizontal scale.
Plans and profiles shall show:
A) Location of streets and sewers.
B) Line of ground surface, size, material and type of pipe,
length between manholes, invert and surface elevation at
each manhole, and grade of sewer between each two
adjacent manholes. All manholes shall be numbered on
the plan and correspondingly numbered on the profile.
C) Except where overhead sewers are required by local
ordinance, if there is any question of the sewer being
sufficiently deep to serve any residence, the elevation
and location of the basement floor shall be plotted on
the profile of the sewer which is to serve the house in
question. The engineer shall state that all sewers are
sufficiently deep to serve adjacent basements except
where otherwise noted on the plans.
D) Locations of all special features such as inverted
siphons, concrete encasements, elevated sewers, etc.
E) All known existing structures both above and below
ground which might interfere with the proposed
construction, particularly water mains, gas mains,
storm drains, etc.
F) Special detail drawings, made to a scale to clearly show
the nature of the design, shall be furnished to show the
following particulars:
i) All stream crossings and sewer outlets, with
elevations of the stream bed and of normal and
extreme high and low water levels.
ii) Cross sections and details of all special or non
standard joints.
iii) Details of all sewer appurtenances such as
manholes, lampholes, inspection chambers, inverted
siphons, regulators, tide gates and elevated
sewers.
c) Plans of Sewage Pumping Stations
1) Location Plan
A plan shall be submitted for projects involving construction
or revision of pumping stations. This plan shall show the
following:
A) The location and extent of the tributary area.
B) Any municipal boundaries within the tributary area.
C) The location of the pumping station and force main.
2) Detail Plan
Detail plans shall be submitted showing the following where
applicable:
A) Grading plan of the station site.
B) Location of existing pumping station.
C) Proposed pumping station, including provisions for
installation of future pumps or ejectors.
D) Elevation of high flood water at the site, and maximum
elevation of sewage in the collection system upon
occasion of power failure, and the pumping station
elevations.
E) Test borings and groundwater elevations.
F) Force main routing and profile.
d) Plans of Sewage Treatment Plants
1) Location Plan
A) A plan shall be submitted showing the sewage treatment
plant in relation to the remainder of the system.
B) Sufficient topographic features shall be included to
indicate its location with relation to streams and the
point of discharge of treated effluent.
C) All residences within one-half mile of the site shall be
shown.
2) General Layout
Layouts of the proposed sewage treatment plant shall be
submitted, showing:
A) Topography of the site.
B) Size and location of plant structures.
C) Schematic flow diagram showing the flow through various
plant units.
D) Piping, including any arrangements for by-passing
individual units. Materials handled and direction of
flow through pipes shall be shown.
E) Test borings and expected range of ground water
elevations.
3) Detail Plans
Detail plans shall show the following:
A) Location, dimensions and elevations of all existing and
proposed plant facilities, including flood protection
structures where applicable.
B) Elevations of high and low water levels of the body of
water to which the plant effluent is to be discharged.
C) Type, size, pertinent features, and manufacturer's rated
capacity of all pumps, blowers, motors and other
mechanical devices.
D) Hydraulic profiles of the treatment plant at design peak
flow including recirculated flows at the 25-year flood
elevation in the receiving watercourse. To ensure their
proper functioning, the hydraulic profile at measuring
devices at minimum flow shall be shown.
E) Hydraulic profiles shall be shown for supernatant liquor
lines, recirculating flow piping and sludge transfer
lines at the design peak flows carried by each system.
F) Adequate description of any features not otherwise
covered by specifications or engineer's report.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.230 Specifications to Accompany Detailed Engineering Plan
Drawings>>
a) Complete technical specifications for the construction of sewers,
sewage pumping stations, sewage treatment plants, and all
appurtenances, shall accompany the plans.
b) The specifications accompanying construction drawings shall
include, but not be limited to, the following:
1) All construction information, not shown on the drawings,
which is necessary to inform the builder in detail of the
design requirements as to the quality of materials and
workmanship and fabrication of the project.
2) The type, size, strength, operating characteristics and
rating of equipment.
3) Allowable infiltration.
4) The complete requirements for all mechanical and electrical
equipment, including machinery, valves, piping and jointing
of pipe.
5) Electrical apparatus, wiring and meters.
6) Laboratory fixtures and equipment.
7) Operating tools.
8) Construction materials.
9) Special filter materials such as stone, sand, gravel or slag.
10) Chemicals when used.
11) Miscellaneous appurtenances.
12) Instruction for testing materials and equipment as necessary.
13) Availability of soil boring information.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.240 Revisions to Approved Plans and Specifications>>
a) Any deviations from approved plans or specifications for
structural configuration, appurtenances or manufactured equipment,
affecting capacity, flow, operation of units or operational
safety, and for substitution of the manufactured equipment
specified and depicted in the plan documents shall be approved in
writing by the Agency before such installation of equipment or
construction changes are made.
b) Plans and specifications requiring Agency approval under
subsection (a) should be submitted well in advance of the ordering
and delivery of equipment or any construction work which will be
affected by such changes, to allow sufficient time for review and
approval. Record drawings of the project as completed shall be
submitted to the Agency.
<BSection 370.250 Operation During Construction>>
Specifications shall contain a time schedule describing the plant and
collection system operational modes during construction. Where units
essential to effluent quality are involved, temporary measures, such as wet
hauling, sludge storage lagoons and portable pumping facilities shall be
included in the specifications so as to ensure continuity of operation as
required and approved by the Agency.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.260 Engineers Seal>>
Plans and specifications, prepared by an Illinois Registered Professional
Engineer when required by Section 14 of the Illinois Professional
Engineering Act [225 ILCS 325/14], fully describing the design, nature,
function and interrelationship of each individual component of the facility
or source, shall be submitted, except that the Agency may waive this
requirement for plans and specifications when the application is for a
routine renewal.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
SUBPART C: DESIGN OF SEWERS
<BSection 370.300 General Considerations>>
a) Type of Sewers
The Agency will approve plans for new sewer systems and extensions
only when designed as the separate sanitary type in which
precipitation runoff and ground water from foundation drains are
excluded. The Agency will not approve the installation of new
combined sewers, except as provided in 35 Ill. Adm. Code 306.302.
b) Design Period
Sewer systems should be designed for the estimated ultimate
tributary population, except in considering parts of the systems
that can be readily increased in capacity. Similarly,
consideration should be given to the maximum anticipated capacity
of institutions, industrial parks, etc.
c) Design Factors
In determining the required capacities of sanitary sewers, the
following factors should be considered:
1) Design peak flow.
2) Additional design peak flow from industrial plants.
3) Ground water infiltration.
4) Topography of area.
5) Location of waste treatment plant.
6) Depth of excavation.
7) Pumping requirements.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.310 Design Basis>>
a) Per Capita Flow
1) New Sewers for Undeveloped Areas
New sewer systems to serve currently undeveloped areas shall
be designed on the basis of a design average flow of not
less than 100 gallons per capita per day which is assumed to
cover normal infiltration, but an additional allowance
should be made where conditions are unfavorable.
2) New Sewers for Existing Developed Areas
For new sewers designed to serve existing developed areas,
the design average flow per capita (100 gpd) shall be
appropriately increased to allow for inflow/infiltration
contributions from the existing buildings other than roof and
foundation drains which shall be excluded in accordance with
Section 370.121(a).
b) Design Peak Flow
1) The design peak flow for sanitary sewers shall be selected
based on one of the following methods:
A) The ratio of peak to average daily flow as determined
from Appendix D, Figure No. 1.
B) Values established from an infiltration/inflow study
acceptable to the Agency.
2) Use of other values for the design peak flow will be
considered if justified on the basis of extensive
documentation.
3) Combined Sewer Interceptors
Intercepting sewers, in the case of combined sewer systems,
should fulfill the above requirements for sewers and have
sufficient additional capacity to transport the increment of
combined sewage required by the IPCB Regulations.
c) Alternate Methods
When deviations from subsections (a) and (b) are proposed, a
description of the procedure used for sewer design shall be
included in the submission of plan documents.
d) Basis of Design and Calculations
The basis of design for all sewer projects shall accompany the
plan documents. Calculations shall be submitted to show that
sewers will have sufficient hydraulic capacity to transport the
design peak flows.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.320 Details of Design and Construction>>
a) Minimum Size
No public gravity sewer conveying raw sewage shall be less than 8
inches in diameter.
b) Depth
Sewers shall be sufficiently deep to prevent freezing. Sewers
should be sufficiently deep to serve basements except where
overhead sewers are required by local ordinances or will be
provided.
1) Minimum Cover
The minimum cover of sewers shall be no less than 3 feet
unless special structural protection is provided.
2) Buoyancy
Where high ground water conditions are anticipated, buoyancy
of sewers shall be considered and, if necessary, adequate
provisions should be made for protection.
c) Slope
1) All sewers shall be designed and constructed to give mean
velocities, when flowing full, of not less than 2.0 feet per
second, based on Manning's formula using an "n" value of
0.013. The following minimum slopes shall be provided;
however, slopes greater than these are desirable:
Minimum Slope in Feet
Sewer Size Per 100 Feet Flow (mgd)
8 inch 0.40 0.49
10 inch 0.28 0.75
12 inch 0.22 1.07
14 inch 0.17 1.43
15 inch 0.15 1.61
16 inch 0.14 1.85
18 inch 0.12 2.35
21 inch 0.10 3.23
24 inch 0.08 4.13
27 inch 0.067 5.17
30 inch 0.058 6.37
33 inch 0.050 7.66
36 inch 0.046 9.23
42 inch 0.036 12.41
2) Under special conditions, if detailed justifiable reasons are
given, slopes slightly less than those required for the 2.0
feet per second velocity when flowing full may be permitted.
Such decreased slopes will only be considered where the depth
of flow will be 0.3 of the diameter or greater for design
average flow. Whenever such decreased slopes are selected,
the design engineer must furnish with his report his
computations of the depths of flow in such pipes at minimum,
design average, and design peak rates of flow. It must be
recognized that decreased slopes may cause additional sewer
maintenance expense and special linings or materials should
be considered for corrosion protection.
3) Uniform Slope
Sewers shall be laid with uniform slope between manholes.
4) Steep Slope Protection
Sewers on 20 percent slope or greater shall be anchored
securely with concrete anchors or equal, spaced as follows:
A) Not over 36 feet center to center on grades 20 percent
and up to 35 percent.
B) Not over 24 feet center to center on grades 35 percent
and up to 50 percent.
C) Not over 16 feet center to center on grades 50 percent
and over.
d) Alignments
1) Straight Alignments
Except as noted in subsection (d)(2), all sewers shall be
laid with straight alignments between manholes.
2) Curvilinear Alignments
Curvilinear sewers are permitted in special cases provided
the following minimum requirements are met:
A) Curvilinear Sewers 24 Inches in Diameter and Smaller
i) Location: Curvilinear alignments should follow the
general alignment of streets.
ii) Type Curve: Only simple curve design is
acceptable.
iii) Radius of Curvature: The minimum allowable radius
of curvature is 300 feet.
iv) Manholes: Manholes are required at the beginning
and end of all curves.
v) Joints: Compression joints are required. The ASTM
or AWWA maximum allowable deflection of the pipe
joints shall not be exceeded.
vi) Velocity: In order to maintain a minimum velocity
of 2 feet per second in curvilinear sewers,
hydraulics of the curvilinear alignment shall be
taken into account and the minimum slopes indicated
in subsection (c)(1) must be increased accordingly.
B) Curvilinear Sewers 24 Inches Through 48 Inches in
Diameter
Curvilinear sewers larger than 24 inches in diameter up
to 48 inches in diameter constructed with pressure pipe
meeting AWWA standards may be used. Other curvilinear
sewers larger than 24 inches in diameter up to 48 inches
in diameter shall meet the requirements of subsection
(d)(2)(A) except that the joints must be manufactured so
that they fit together squarely without deflection at
the design curvature and the radius of curvature may be
less than 300 feet.
C) Curvilinear Sewers Larger Than 48 Inches in Diameter
Curvilinear sewers larger than 48 inches in diameter
shall be provided with square fitting compression joints
and shall meet the requirements of subsection
(d)(2)(A)(vi). The remaining design requirements under
subsection (d)(2)(A) for these sewers will be reviewed
by the Agency on a case by case basis.
e) Increasing Size
When a smaller sewer joins a larger one, the invert of the larger
sewer should be sufficiently lower to maintain the energy
gradient. An approximate method for securing these results is to
place the 0.8 depth point of both sewers at the same elevation.
f) High Velocity Protection
Where velocities greater than 15 feet per second are attained, the
special provisions described in subsection (c)(4) shall be made to
protect against displacement by erosion and shock.
g) Materials and Installation
1) Materials
A) Any generally accepted material for sewers will be given
consideration, but the material selected should be
suitable for local conditions, such as character of
industrial wastes, possibility of septicity, soil
characteristics, exceptionally heavy external loadings,
abrasion, structural considerations and similar
problems.
B) All sewers shall be designed and installed to prevent
damage from superimposed loads. Proper allowance for
loads on the sewer shall be made because of the width
and depth of trench. When the bearing strength of the
pipe is not adequate to withstand the superimposed
loading, other pipe material, special handling, concrete
cradle or special construction shall be used.
C) For new pipe materials for which ASTM standards have not
been established (see subsection (g)(2)), the designing
engineer shall provide complete installation
specifications developed on the basis of criteria
adequately documented and certified in writing by the
pipe manufacturer to be satisfactory for the design
conditions for the specific project. Such documentation
and manufacturers' certification shall be submitted as a
part of the project plan documents.
2) Installation
A) Standards
i) Installation specifications shall contain
appropriate requirements based on the criteria,
standards and requirements established by ASTM.
Requirements shall be set forth in the
specifications for the pipe and methods of bedding
and backfilling thereof so as not to damage the
pipe or its joints, impede cleaning operations and
future tapping, nor create excessive side fill
pressures or ovalation of the pipe, nor seriously
impair flow capacity.
ii) For new pipe material, the installation
specifications shall meet the provisions of
subsection (g)(1).
B) Trenching
i) The width of the trench shall be ample to allow the
pipe to be laid and jointed properly and to allow
the backfill to be placed and compacted as needed.
The trench sides shall be kept as nearly vertical
as possible. When wider trenches are dug,
appropriate bedding class and pipe strength shall
be used.
ii) Ledge rock, boulders, and large stones shall be
removed to provide a minimum clearance of 4 inches
below and on each side of all pipe and joints.
C) Bedding
i) Bedding classes A, B, or C, as described in ASTM
Cl2-95, "Standard Practice for Installing Vitrified
Clay Pipe Lines" (1996) or "Standard Specifications
for Water and Sewer Main Construction in Illinois",
5th ed. (1996) (no later additions or amendments)
or WPCF Manual of Practice (MOP) No. FD-5 (1982)
(no later additions or amendments) shall be used
for all rigid pipe provided the proper strength
pipe is used with the specified bedding to support
the anticipated load.
ii) Bedding class I, II, or III, as described in ASTM
D2321-89, "Standard Practice for Underground
Installation of Thermoplastic Pipe for Sewers and
Other Gravity-Flow Applications" (1996) (no later
editions or amendments) or Standard Specifications
for Water and Sewer Main Construction in Illinois,
5th ed. (1996) (no later additions or amendments),
or WPCF MOP No. FD-5 (1982)(no later additions or
amendments) shall be used for all flexible pipe
provided the proper strength pipe is used with the
specified bedding to support the anticipated load.
D) Backfill
i) Backfill shall be of a suitable material removed
from excavation except where other material is
specified. Debris, frozen material, large clods or
stones, organic matter, or other unstable materials
shall not be used for backfill within 2 feet of the
top of the pipe.
ii) Backfill shall be placed in such a manner as not to
disturb the alignment of the pipe.
iii) For flexible pipe, as a minimum, backfill material
shall be placed and carefully compacted in
accordance with ASTM D2321-89 (1996) to provide the
necessary support for the pipe.
3) Deflection Testing of Flexible Pipe.
A) The design specifications shall provide that the first
1200 feet of sewer and at least 10% of the remainder of
the sewer project shall be deflection tested. The
entire length of a sewer of less than 1200 feet shall be
deflection tested.
B) If the deflection test is to be run using a rigid ball
or mandrel, it shall have a diameter equal to 95% of the
inside or base diameter of the pipe as established in
the ASTM standard to which the pipe is manufactured.
The test shall be performed without mechanical pulling
devices.
C) The individual lines to be tested shall be tested for
final acceptance no sooner than 30 days after they have
been installed.
D) Whenever possible and practical, the testing shall
initiate at the downstream lines and proceed towards the
upstream lines.
E) No pipe shall exceed a deflection of 5%.
F) In the event that the deflection exceeds the 5% limit in
10% or more of the manhole intervals tested, the total
sewer project shall be tested.
h) Joints and Infiltration
1) Joints
The type and method of making joints and the materials used
shall be included in the specifications and also shall be
shown on the plans. Sewer joints shall be specified to
minimize infiltration and to prevent the entrance of roots.
Joint material shall conform to ASTM standards. Cement grout
joints shall not be used for pipe to pipe joints.
2) Leakage Testing
Leakage tests shall be specified.
A) Test Sections
The design specifications shall provide that the first
1200 feet and at least 10% of the remainder of the sewer
project shall be tested for leakage. The entire length
of a sewer of less than 1200 feet shall be tested for
leakage. In the event that 10% or more of the manhole
intervals tested do not pass the leakage test, the
entire sewer project shall be tested.
B) Testing Methods
Testing methods may include appropriate water or low
pressure air testing. The use of television cameras or
other visual methods for inspection prior to placing the
sewer in service and prior to acceptance is
recommended.
C) Water Testing
i) The leakage outward or inward (exfiltration or
infiltration) shall not exceed the following limits
in gallons per inch of pipe diameter per mile per
day for any section of the system:
Exfiltration: 240
Infiltration: 200
ii) An exfiltration or infiltration test shall be
performed with a minimum positive head of 2 feet.
D) Air Testing
If used, the air test shall, as a minimum, conform to
the test procedure described in Section 31-1.11B of
Standard Specifications for Water and Sewer Main
Construction in Illinois, 5th ed. (1996)(no later
additions or amendments). The specifications shall
require that the time required for a pressure drop from
3.5 to 2.5 PSIG not be less than the time specified in
the Air Test Table in Appendix C. The testing methods
selected should take into consideration the range in
groundwater elevations projected and the situation
during the test.
i) Service Connections
Sewer service connections shall meet the same criteria as public
sanitary sewers described elsewhere in this Subpart C except as
noted in this subsection (i). Roof and foundation drain
connections to the sewer service connection are prohibited except
as provided for in 35 Ill. Adm. Code 306.302. The service
connection tap into the public sewer shall be watertight and shall
not protrude into the public sewer. If a saddle type connection
is used, it shall be a commercially available device designed to
join with the types of pipe that are to be connected. All
materials used to make service connections shall be compatible
with one another and with the pipe materials to be joined, and
shall be corrosion-proof.
1) Size
Service sewers and fittings shall be a minimum of 4 inches in
diameter, but shall not be less than the diameter of the
plumbing pipe from the building.
2) Slope
Service sewers shall have a minimum slope of 1%.
3) Alignment
When straight line alignment is not maintained on service
connections, cleanouts or manholes shall be provided at
points of changes in alignment.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.330 Manholes>>
a) Location
Except as noted in Section 370.123(d)(2), manholes shall be
installed at the end of each line; at all changes in grade, size
or alignment; at all sewer intersections; and at distances not
greater than 400 feet for sewers 15 inches or less, and 500 feet
for sewers 18 inches through 30 inches. Distances up to 600 feet
may be approved in cases where adequate modern cleaning equipment
for such spacing is provided. Greater spacing may be permitted in
larger sewers and in those carrying a settled effluent. Lampholes
may be used only for special conditions and shall not be
substituted for manholes nor installed at the end of laterals
greater than 150 feet in length.
b) Type
1) Drop Type
A pipe shall be provided for a sewer entering a manhole where
its invert elevation is more than 24 inches above the manhole
invert. If an inside drop pipe is used, the manhole diameter
shall be large enough to provide a minimum clearance of 48
inches between the pipe and the opposite side of the manhole.
Inside drip pipes shall be anchored to the manhole wall with
corrosion-proof fasteners and bands. For sewers 36 inches in
diameter or greater, the requirements for a drop pipe do not
apply if the spring line of the incoming pipe is at or below
the spring line of the main sewer. As a minimum, the
diameter of the drop pipe shall be at least 2/3 as large as
the diameter of the sewer tributary to the drop pipe.
2) Non Drop Type
Where the difference in elevation between the incoming sewer
invert and the manhole invert is less than 24 inches, the
manhole invert should be filleted to prevent solids
deposition.
c) Diameter
1) For sewers 36 inches in diameter and smaller, the minimum
diameter of manholes shall be 48 inches. For sewers larger
than 36 inches in diameter, the manhole diameter at the
invert shall be sufficiently large to accommodate the
incoming pipes; and the riser barrel diameter shall be a
minimum of 48 inches.
2) A minimum access lid diameter of 24 inches shall be provided.
d) Flow Channel
The flow channel through manholes should be made to conform in
shape and slope to that of the sewers. A bench shall be provided
which should have a minimum slope of 2 inches per foot.
e) Watertightness
1) Construction Requirements
Watertight manhole covers shall be used wherever the manhole
tops may be flooded by surface runoff or high water or are
below cover. Pickholes shall not be larger than 1 inch in
diameter or shall be of the concealed type. Construction
lifting holes on manhole rings shall be plugged from the
outside and the exterior and joints of the manhole elements
shall be waterproofed. Precast inlet and outlet connections
fitted with "0" rings or other equally watertight connections
shall be provided.
2) Inspection
The specifications shall include a requirement for inspection
and leakage testing of all manholes for watertightness in
accordance with ASTM C969-94--"Standard Practice for
Infiltration and Exfiltration Acceptance Testing of Installed
Precast Concrete Pipe Sewer Lines", Vol. 04.05, Chemical
Resistant Materials, Vitrified Clay, Concrete, Fiber-Cement
Products; Mortars; Masonry (1996) (no later editions or
amendments) or ASTM C1244-93 "Standard Test Method for
Concrete Sewer Manholes by the Negative Pressure (Vacuum)
Test", Vol. 04.05, Chemical Resistant Materials, Vitrified
Clay, Concrete, Fiber-Cement Products; Mortars; Masonry
(1996) (no later editions or amendments) prior to placing
into service.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.340 Sewers in Relation to Streams>>
a) Location of Sewers on Streams
1) Cover Depth
A) The top of all sewers entering or crossing streams shall
be at a sufficient depth below the natural bottom of the
stream bed to protect the sewer line. In general the
following cover requirements must be met:
i) One foot of cover is required where the sewer is
located in rock.
ii) Three feet of cover is required in other material.
In major streams, more than three feet of cover may
be required.
iii) In paved stream channels, the top of the sewer
line should be placed below the bottom of the
channel pavement.
B) Less cover will be approved only if the proposed sewer
crossing will not interfere with the future improvements
to the stream channel. Reasons for requesting less
cover should be given in the project proposal.
2) Horizontal Location
Sewers located along streams shall be located outside of the
stream bed and sufficiently removed therefrom to provide for
future possible stream widening and to prevent pollution by
siltation during construction.
3) Structures
The sewer outfalls, headwalls, manholes, gate boxes, or other
structures shall be located so they do not interfere with the
free discharge of flood flows of the stream.
4) Alignment
Sewers crossing streams should be designed to cross the
stream as nearly perpendicular to the stream flow as possible
and shall be designed without change in grade. Sewer
systems shall be designed to minimize the number of stream
crossings.
b) Construction
1) Materials and Backfill
A) Sewers entering or crossing streams shall be constructed
of cast or ductile iron pipe with mechanical joints and
shall be capable of absorbing pipe movement and
joint-deflection while remaining intact and watertight.
B) The backfill used in the trench shall be coarse
aggregate, gravel, or other materials which will not
cause siltation, pipe damage during placement or
chemical corrosion in place.
2) Siltation and Erosion
Construction methods that will minimize siltation and erosion
shall be employed. The design engineer shall include in the
project specifications the methods to be employed in the
construction of sewers in or near streams to provide
adequate control of siltation and erosion. Specifications
shall require that cleanup, grading, seeding, and planting
or restoration of all work areas shall begin immediately.
Exposed areas shall not remain unprotected for more than
seven days.
c) Aerial Crossings
1) Structural Support
Support shall be provided for all joints in pipes utilized
for aerial crossings. The supports shall be designed to
prevent frost heave, overturning and settlement.
2) Freeze and Expansion Protection
Protection against freezing shall be provided. This may be
accomplished through the use of insulation and increased
slope. Expansion jointing shall be provided between the
aerial and buried sections of the sewer line.
3) Flood Clearance
For aerial stream crossings, the impact of flood waters and
debris shall be considered. The bottom of the pipe should be
placed no lower than the elevation of the 50 year flood.
d) Inverted Siphons
Inverted siphons shall have not less than 2 barrels, with a
minimum pipe size of 6 inches and shall be provided with necessary
appurtenances for convenient flushing and maintenance. Long radius
fittings should be used. The inlet and outlet structures shall
have adequate clearances for rodding; and in general, sufficient
head shall be provided and pipe sizes selected to secure
velocities of at least 3.0 feet per second for design average
flows. The inlet and outlet structures shall be designed so that
the design average flow is diverted to 1 barrel, and so that
either barrel may be cut out of service for cleaning.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.350 Protection of Water Supplies>>
a) Water Supply Interconnections
There shall be no physical connections between a public or private
potable water supply system and a sewer, or appurtenance thereto,
which would permit the passage of any sewage or polluted water
into the potable supply.
b) Location Relative to Water Works Structures
1) Location and Soil Condition
A) The engineering plan documents shall show the location
of all existing water works structures (basins, wells,
other treatment units, etc.) that are within 200 feet of
the proposed sewer.
B) Soil conditions in the vicinity of the water works
structures shall be investigated and depicted on the
plans.
2) Minimum Distances
The following minimum distances apply to clay and loan soils
and, as a minimum, shall be doubled for sand. In areas
where creviced limestone or gravel may be encountered, the
Agency shall be contacted for a determination as to what
minimum separation distances and special construction will be
required.
A) Non-watertight sewers and sewer appurtenances such as
manholes and wetwells shall not be located closer than
50 feet from water works structures.
B) Sewers located closer than 50 feet to water works
structures shall be constructed with water main quality
pipe and joints that comply with 35 Ill. Adm. Code
653.119. All such pipe shall be pressure tested in
accordance with "AWWA Standard for Installation of
Ductile-Iron Water Mains and their Appurtenances,"
ANSI/AWWA C600-93 (1994), (no later editions or
amendments) for a working pressure equal to or greater
than the maximum possible surcharge head to assure
watertightness prior to backfilling. No sewer shall be
located closer than 10 feet from water works structures.
c) Relation to Water Mains
1) Horizontal and Vertical Separation
A) Whenever possible, a sewer must be at least ten feet
horizontally from any existing or proposed water main.
B) Should local conditions exist which would prevent a
lateral separation of ten feet, a sewer may be closer
than ten feet to a water main provided that the water
main invert is at least eighteen inches above the crown
of the sewer, and is either in a separate trench or in
the same trench on an undisturbed earth shelf located to
one side of the sewer.
C) If it is impossible to obtain proper horizontal and
vertical separation as described above, both the water
main and sewer must be constructed with water main
quality pipe and joints that comply with 35 Ill. Adm.
Code 653.119 and shall be pressure tested in accordance
with "AWWA Standard for Installation of Ductile-Iron
Water Mains and their Appurtenances," ANSI/AWWA C600-93
(1994) (no later editions or amendments) for a working
pressure equal to or greater than the maximum possible
surcharge head to assure watertightness before
backfilling.
2) Water-Sewer Line Crossings
A) Whenever possible, sewers crossing water mains shall be
laid with the sewer below the water main with the crown
of the sewer a minimum of 18 inches below the invert of
the water main. The vertical separation shall be
maintained on each side of the crossing until the
perpendicular distance from the water main to the sewer
is at least 10 feet. The crossing shall be arranged so
that the sewer joints will be equidistant and as far as
possible from the water main joints. Adequate support
shall be provided for the water mains to prevent damage
due to settling of the sewer trench. Refer to Appendix
H, Drawing No. 1.
B) Where a sewer crosses under a water main and it is not
possible to provide an 18-inch vertical separation, the
following special construction methods shall be
specified (refer to Appendix H, Drawing No. 2):
i) The sewer shall either be constructed with water
main pipe and joints that comply with 35 Ill. Adm.
Code 653.119 and shall be pressure tested in
accordance with "AWWA Standard for Installation of
Ductile-Iron Water Mains and their Appurtenances,"
ANSI/AWWA C600-93 (1994) (no later editions or
amendments) for a working pressure equal to or
greater than the maximum possible surcharge head
or shall be encased in a carrier pipe with the ends
sealed, that, along with the joints, complies with
35 Ill. Adm. Code 653.119.
ii) The water main quality sewer or carrier pipe shall
extend on each side of the crossing to a point
where the perpendicular distance from the water
main to the sewer is at least 10 feet.
iii) For the required length of the water main quality
sewer or carrier pipe, omit the select granular
cradle and granular backfill to one foot over the
crown of the sewer and use selected excavated
material (Class IV) and compact to 95% of Standard
Proctor maximum density.
iv) Point loads between the sewer or sewer casing and
the water main are prohibited.
v) Adequate support shall be provided for the water
main to prevent damage due to settling of the sewer
trench.
C) Where it is not possible for a proposed sewer to cross
under an existing water main, the specifications shall
require the construction methods set out in subsection
(c)(2)(B) above and shall require that any select
granular backfill above the crown of the water main be
removed within the width of the proposed sewer trench
and be replaced with select excavated material (Class
IV) compacted to 95% of Standard Proctor maximum
density. Where a proposed sewer must cross over a
proposed water main, an 18-inch vertical separation
shall be maintained. Refer to Appendix H, Drawing No.
3.
3) Sewer Manhole Separation From Water Main
No water pipe shall pass through or come into contact with
any part of a sewer manhole.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
SUBPART D: SEWAGE PUMPING STATIONS
<BSection 370.400 General>>
a) Flooding
Sewage pumping station structures and electrical and mechanical
equipment shall be protected from physical damage by the 100 year
flood. Sewage pumping stations should remain fully operational
and accessible during the 25 year flood. Regulations of State
and Federal agencies regarding flood plain obstructions shall be
considered.
b) Accessibility
The pumping station shall be readily accessible by maintenance
vehicles during all weather conditions. The facility should be
located off the traffic way of streets and alleys.
c) Grit
Where it is necessary to pump sewage prior to grit removal, the
design of the wet well and pump station piping shall receive
special consideration to avoid operational problems from the
accumulation of grit.
<BSection 370.410 Design>>
The following items should be given consideration in the design of sewage
pumping stations:
a) Type
Sewage pumping stations in general use fall into three types:
wet well/dry well, submersible, and suction lift.
b) Structures
1) Separation
Dry wells, including their superstructure, shall be
completely separated from the wet well. Common walls must be
gastight.
2) Pump Removal
Provision shall be made to facilitate removing pumps and
motors.
3) Access
A) Suitable and safe means of access shall be provided to
dry wells and to wet wells. Access to wet wells
containing either bar screens or mechanical equipment
requiring inspection or maintenance shall conform to
Section 370.600(a)(2)(C).
B) For built-in-place pump stations, a stairway to the dry
well with rest landings shall be provided at vertical
intervals not to exceed 12 feet. For factory-built pump
stations over 15 feet deep, a rigidly fixed landing
shall be provided at vertical intervals not to exceed 10
feet. Where a landing is used, a suitable and rigidly
fixed barrier shall be provided to prevent an individual
from falling past the intermediate landing to a lower
level. A manlift or elevator may be used in lieu of
landings in a factory-built station, provided emergency
access is included in the design.
4) Buoyancy
Where high ground water conditions are anticipated, buoyancy
of the sewage pumping station structures shall be considered
and, if necessary, adequate provisions shall be made for
protection.
c) Pumps and Pneumatic Ejectors
1) Multiple Units
Multiple pumps or ejector units shall be provided. Where
only two units are provided, they shall be of the same size.
Units shall have capacity such that, with any unit out of
service, the remaining units will have capacity to handle the
design peak flows. A single pump equipped with an
audio-visual alarm system to warn of failure may be used when
serving only one single-family dwelling.
2) Protection Against Clogging
A) Pumps handling combined sewage shall be preceded by
readily accessible bar racks to protect the pumps from
clogging or damage. Bar racks should have clear
openings not exceeding 1 inch. Where a bar rack is
provided, a mechanical hoist shall also be provided.
Where the size of the installation warrants,
mechanically cleaned and/or duplicate bar racks shall be
provided.
B) Pumps handling separate sanitary sewage from 30 inch or
larger diameter sewers shall be protected by bar racks
meeting the above requirements. Appropriate protection
from clogging shall also be considered for small pumping
stations.
3) Pump Openings
Pumps handling raw sewage shall be capable of passing spheres
of at least 3 inches in diameter. Pump suction and discharge
openings shall be at least 4 inches in diameter. Grinder
pumps that do not meet these requirements may be used solely
for lift stations with a capacity of 70 gpm or less with the
largest unit out of service.
4) Priming
The pump shall be so placed that under normal operating
conditions it will operate under a positive suction head,
except as specified in Section 370.133.
5) Electrical Equipment
Electrical systems and components (e.g., motors, lights,
cables, conduits, switchboxes, control circuits, etc.) in raw
sewage wet wells, or in enclosed or partially enclosed spaces
where hazardous concentrations of flammable gases or vapors
may be present, shall comply with the National Electrical
Code requirements for Class 1 Group D, Division 1 locations.
In addition, equipment located in the wet well shall be
suitable for use under corrosive conditions. Each flexible
cable shall be provided with water-tight seal and separate
strain relief. A fused disconnect switch located above
ground shall be provided for all pumping stations. When such
equipment is exposed to weather, it shall meet the
requirements of weatherproof equipment (National Electric
Manufacturers Association (NEMA) 3R or 4).
6) Intake
Each pump shall have an individual intake. Wet well and
intake design should be such as to avoid turbulence near the
intake and to prevent vortex formation.
7) Dry Well Dewatering
Duplicate sump pumps equipped with dual check valves for each
pump shall be provided in the dry well to remove leakage or
drainage with discharge above the maximum high water level of
the wet well. Water ejectors connected to a potable water
supply will not be approved. All floor and walkway surfaces
should have an adequate slope to a point of drainage. Pump
seal leakage shall be piped or channeled directly to the
sump. The sump pumps shall be sized to remove the maximum
pump seal water discharge which would occur in the event of
a pump seal failure.
8) Pumping Rates
The pumps and controls of main pumping stations, and
especially pumping stations operated as part of treatment
works, should be selected to operate at varying delivery
rates. The stations shall be designed to deliver as uniform
flow as practicable in order to minimize hydraulic surges.
The peak design flow of the station shall be determined in
accordance with Sections 370.300(c), 370.310(b) and
370.520(c) and should be adequate to maintain a minimum
velocity of 2 feet per second in the force main. Refer to
Section 370.470(f).
d) Controls
Control float tubes and bubbler lines should be so located as not
to be unduly affected by turbulent flows entering the well or by
the turbulent suction of the pumps. Provision shall be made to
automatically alternate the pumps in use.
e) Valves
Shutoff valves shall be placed on suction and discharge lines of
each pump. A check valve shall be placed on each discharge line,
between the shutoff valve and the pump. Check valves shall not be
located on a vertical rise unless they are specifically designed
for such usage.
f) Wet Wells
1) Divided Wells
Where continuity of pumping station operation is critical,
consideration should be given to dividing the wet well into
two sections, properly interconnected, to facilitate repairs
and cleaning.
2) Size
The design fill time and minimum pump cycle time shall be
taken into account in sizing the wet well. The effective
volume of the wet well shall be based on design average flow
and a filling time not to exceed 30 minutes unless the
facility is designed to provide flow equalization. The pump
manufacturer's duty cycle recommendations shall be used in
selecting the minimum cycle time. When the anticipated
initial flow tributary to the pumping station is less than
the ultimate average design flow, provisions should be made
so that the holding time indicated is not exceeded for
initial flows. When the wet well is designed for flow
equalization as part of a treatment plant, provisions should
be made to prevent septicity.
3) Floor Slope
The wet well floor shall have a minimum slope of 1 to 1 to
the hopper bottom. The horizontal area of the hopper bottom
shall be no greater than necessary for proper installation
and function of the inlet.
4) Air Displacement
Covered wet walls shall provide for air displacement open to
the atmosphere, such as by an inverted "j" tube or similar
means.
g) Ventilation
1) General
Adequate ventilation shall be provided for all pump stations.
Where the dry well is below the ground surface, mechanical
ventilation is required. If screens or mechanical equipment
requiring maintenance or inspection is located in the wet
well, permanently installed ventiliation is required. There
shall be no interconnection between the wet well and dry well
ventilation systems.
2) Air Inlets and Outlets
In dry wells over 15 feet deep, multiple inlets and outlets
should be used. Dampers should not be used on exhaust or
fresh air ducts and fine screens or other obstructions in air
ducts should be avoided to prevent clogging.
3) Electrical Controls
Switches for operation of ventilation equipment should be
marked and located conveniently. All intermittently operated
ventilation equipment shall be interconnected with the
respective pit lighting system. Consideration should be
given also to automatic controls where intermittent operation
is used. The manual lighting ventilation switch shall
override the automatic controls.
4) Fans, Heating and Dehumidification
The fan wheel shall be fabricated from non-sparking material.
Automatic heating and dehumidification equipment shall be
provided in all dry wells. The electrical equipment and
components shall meet the requirements of subsection (c)(5)
above.
5) Wet Wells
Wet well ventilation may be either continuous or
intermittent. Ventilation, if continuous, should provide at
least 12 complete air changes per hour; if intermittent, at
least 30 complete air changes per hour. Air shall be forced
into the wet well by mechanical means rather than exhausted
from the wet well. Portable ventilation equipment shall be
provided for use at submersible pump stations and at wet
wells with no permanently installed ventilation equipment.
6) Dry Wells
Dry well ventilation may be either continuous or
intermittent. Ventilation, if continuous, should provide at
least 6 complete air changes per hour; if intermittent, at
least 30 complete air changes per hour. A system of
two-speed ventilation with an initial ventilation rate of 30
changes per hour for 10 minutes and an automatic switch-over
to 6 changes per hour may be used to conserve heat.
h) Flow Measurement
Suitable devices for measuring sewage flow shall be provided at
all pumping stations. Indicating, totalizing and recording flow
measurement shall be provided at pumping stations with a 1200 gpm
or greater design peak flow. Elapsed time meters used in
conjunction with pumping rate tests may be used for pump stations
with a design peak flow of up to 1200 gpm.
i) Water Supply
There shall be no physical connection between any potable water
supply and a sewage pumping station which under any conditions
might cause contamination of the potable water supply. If a
potable water supply is brought to the station, it should comply
with conditions stipulated under Section 370.146(b)(3). In-line
backflow preventors shall not be used.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.420 Suction-Lift Pump Stations>>
a) Pump Priming and Lift Requirements
Suction lift pumps shall be of the self-priming or vacuum-priming
type and shall meet the applicable requirements of Section
370.132. Suction lift pump stations using dynamic suction lifts
exceeding the limits outlined in the following sections may be
approved upon submission of factory certification of pump
performance and detail calculations indicating satisfactory
performance under the proposed operating conditions. Such
detailed calculations must include static suction lift as
measured from "lead pump off" elevation to center line of pump
suction, friction and other hydraulic losses of the suction
piping, vapor pressure of the liquid, altitude correction,
required net positive suction head, and a safety factor of at
least 6 feet.
1) Self-priming Pumps
Self-priming pumps shall be capable of rapid priming and
repriming at the "lead pump on" elevation. Such self-priming
and repriming shall be accomplished automatically under
design operating conditions. Suction piping should not
exceed the size of the pump suction and shall not exceed 25
feet in total length. Priming lift at the "lead pump on"
elevation shall include a safety factor of at least 4 feet
from the maximum allowable priming lift for the specific
equipment at design operating conditions. The combined total
of dynamic suction lift at the "pump off" elevation and
required net positive suction head at design operating
conditions shall not exceed 22 feet.
2) Vacuum-priming Pumps.
Vacuum-priming pump stations shall be equipped with dual
vacuum pumps capable of automatically and completely removing
air from the suction lift pump. The vacuum pumps shall be
adequately protected from damage due to sewage. The combined
total of dynamic suction lift at the "pump off" elevation and
required net positive suction head at design operating
conditions shall not exceed 22 feet.
b) Equipment, Wet Well Access and Valve Location
The pump equipment compartment shall be above grade or offset and
shall be effectively isolated from the wet well to prevent the
humid and corrosive sewer atmosphere from entering the equipment
compartment. Wet well access shall not be through the equipment
compartment. Wet well access may not be through the equipment
compartment and shall be at least 24 inches in diameter. Gasketed
replacements shall be provided to cover the opening to the wet
well for pump units removed for servicing. Valves shall not be
located in the wet well.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.430 Submersible Pump Stations - Special Considerations>>
Submersible pump stations shall meet the applicable requirements under
Section 370.132, except as modified in this Section.
a) Construction
Submersible pumps and motors shall be designed specifically for
raw sewage use, including totally submerged operation during a
portion of each pumping cycle, and shall meet the requirements of
the National Electrical Code (1996). An effective method to
detect shaft seal failure or potential seal failure shall be
provided.
b) Pump Removal
Submersible pumps shall be readily removable and replaceable
without dewatering the wet well or disconnecting any piping in the
wet well.
c) Electrical
1) Power Supply and Control
Electrical supply, control and alarm circuits shall be
designed to provide strain relief and to allow disconnection
from outside the wet well. Terminals and connectors shall be
protected from corrosion by location outside the wet well or
through use of watertight seals. If located outside,
weatherproof equipment shall be used.
2) Controls
The motor control center shall be located outside the wet
well, readily accessible, and be protected by conduit seal or
other appropriate measures meeting the requirements of the
National Electrical Code, to prevent the atmosphere of the
wet well from gaining access to the control center. The
seal shall be so located that the motor may be removed and
electrically disconnected without disturbing the seal.
3) Power Cord
Pump motor power cords shall be designed for flexibility and
serviceability under conditions of extra hard usage and shall
meet the requirements of the National Electric Code (1996)
for flexible cords in sewage pump stations. Ground fault
interruption protection shall be used to de-energize the
circuit in the event of any failure in the electrical
integrity of the cable. Power cord terminal fittings shall
be corrosion-resistant and constructed in a manner to prevent
the entry of moisture into the cable, shall be provided with
strain relief appurtenances, and shall be designed to
facilitate field connecting.
d) Valves
Valves required under Section 370.132(e) shall be located in a
separate valve pit. Provision shall be made to remove accumulated
water from the valve pit. Accumulated water in valve pits deeper
than 4 feet shall be pumped to the wet well or gravity drained to
the ground surface. Valve pits 4 feet deep or less may be gravity
drained to the wet well through a trapped and vented drain that
meets the applicable requirements found in 77 Ill. Adm. Code 890,
"Illinois Plumbing Code". Such pits shall have entrances that
fully expose the pit to the atmosphere. Check valves that are
integral to the pump need not be located in a separate valve pit
provided that the valve can be removed from the wet well in
accordance with subsection (b) above. Provision shall be made for
the use of portable ventiliation equipment during periods of
maintenance.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.440 Alarm Systems>>
Alarm systems shall be provided for pumping stations. The alarm shall be
activated in cases of power failure, pump failure, unauthorized entry, or
any cause of pump station malfunction. Pumping station alarms shall be
telemetered to a municipal facility that is manned 24 hours a day. If such
a facility is not available and a 24-hour holding capacity is not provided,
the alarm shall be telemetered to city offices during normal working hours
and to the home of the person(s) in responsible charge of the lift station
during off-duty hours. Audio-visual alarm systems with a self-contained
power supply may be acceptable in some cases in lieu of the telemetering
system outlined above, depending upon location, station holding capacity
and inspection frequency.
<BSection 370.450 Emergency Operation>>
a) Objective
The objective of emergency operation is to prevent the discharge
of raw or partially treated sewage to any waters and to protect
public health by preventing back-up of sewage and subsequent
discharge to basements, streets, and other public and private
property.
b) Emergency Pumping Capability
Provision of emergency pumping capability is mandatory and may be
accomplished by connection of the station to at least two
independent utility substations, or by provision of portable or
in-place internal combustion engine equipment which will generate
electrical or mechanical energy, or by the provision of portable
pumping equipment. Emergency standby systems shall have
sufficient capacity to start up and maintain the total rated
running capacity of the station. Regardless of the type of
emergency standby system provided, a riser from the force main
with rapid connection capabilities and appropriate valving shall
be provided for all lift stations to hook up portable pumps.
c) Emergency High Level Overflows
For use during possible periods of extensive power outages,
mandatory power reductions, or uncontrollable emergency
conditions, consideration should be given to providing a
controlled, high-level wet well overflow to supplement alarm
systems and emergency power generation in order to prevent backup
of sewage into basements, or other discharges which may cause
severe adverse impacts on public interests, including public
health and property damage. Where a high level overflow is
utilized, consideration shall also be given to the installation
of storage/detention tanks, or basins, which shall be made to
drain to the station wet well. Where such overflows affect
public water supplies or waters used for culinary or food
processing purposes, a storage detention basin, or tank, shall be
provided having 2-hour detention capacity at the anticipated
overflow rate.
d) Equipment Requirements
1) General
The following general requirements shall apply to all
internal combustion engines used to drive auxiliary pumps,
service pumps through special drives, or electrical
generating equipment:
A) Engine Protection
The engine must be protected from operating conditions
that would result in damage to equipment. Unless
continuous manual supervision is planned, protective
equipment shall be capable of shutting down the engine
and activating an alarm on site and as provided in
Section 370.135. Protective equipment shall monitor for
conditions of low oil pressure and overheating, except
that oil pressure monitoring will not be required for
engines with splash lubrication.
B) Size
The engine shall have adequate rated power to start and
continuously operate all connected loads.
C) Fuel Type
Reliability and ease of starting, especially during cold
weather conditions, should be considered in the
selection of the type of fuel.
D) Engine Ventilation
The engine shall be located above grade with adequate
ventilation of fuel vapors and exhaust gases.
E) Routine Start-up
All emergency equipment shall be provided with
instructions indicating the need for regular starting
and running of such units at full loads.
F) Protection of Equipment
Emergency equipment shall be protected from damage at
the restoration of regular electrical power.
2) Engine - Drive Pumping Equipment
Where permanently-installed or portable engine-driven pumps
are used, the following requirements in addition to general
requirements shall apply:
A) Pumping Capacity
Engine-drive pumps shall meet the design pumping
requirements unless storage capacity is available for
flows in excess of pump capacity. Pumps shall be
designed for anticipated operating conditions, including
suction lift if applicable.
B) Operation
The engine and pump shall be equipped to provide
automatic start-up and operation of pumping equipment
unless manual start-up and operation is justified.
Provisions shall also be made for manual start-up.
Where manual start-up and operation is justified,
storage capacity and alarm system must meet the
requirements of subsection (d)(2)(C).
C) Portable Pumping Equipment
Where part or all of the engine-driven pumping equipment
is portable, sufficient storage capacity shall be
provided to allow time for detection of pump station
failure and transportation and hookup of the portable
equipment.
3) Engine-Driven Generating Equipment
Where permanently-installed or portable engine-driven
generating equipment is used, the following requirements
shall apply in addition to general requirements of subsection
(d)(1):
A) Generating Capacity
i) Generating unit size shall be adequate to provide
power for pump motor starting current and for
lighting, ventilation, and other auxiliary
equipment necessary for safety and proper operation
of the lift station.
ii) The operation of only one pump during periods of
auxiliary power supply must be justified. Such
justification may be made on the basis of the
design peak flows relative to single-pump capacity,
anticipated length of power outage, and storage
capacity.
iii) Special sequencing controls shall be provided to
start pump motors unless the generating equipment
has capacity to start all pumps simultaneously with
auxiliary equipment operating.
B) Operation
Provisions shall be made for automatic and manual
start-up and load transfer unless only manual start-up
and operation is justified. The generator must be
protected from operating conditions that would result in
damage to equipment. Provisions should be considered to
allow the engine to start and stabilize at operating
speed before assuming the load. Where manual start-up
and transfer is justified, storage capacity and alarm
system must meet the requirements of subsection
(d)(3)(C).
C) Portable Generating Equipment
Where portable generating equipment or manual transfer
is provided, sufficient storage capacity shall be
provided to allow time for detection of pump station
failure and transportation and connection of generating
equipment. The use of special electrical connections
and double throw switches are recommended for connecting
portable generating equipment.
4) Independent Utility Substations
Where independent substations are used for emergency power,
each separate substation and its associated transmission
lines must be capable of starting and operating the pump
station at its rated capacity.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.460 Instructions and Equipment>>
Sewage pumping stations and portable equipment shall be supplied with a
complete set of operational instructions, including emergency procedures,
maintenance schedules, tools and such spare parts as may be necessary.
<BSection 370.470 Force Mains>>
a) Velocity and Diameter
At design pumping rates, a cleansing velocity of at least 2 feet
per second should be maintained. Lower velocities may be
permitted for very small installations. The minimum force main
diameter for raw sewage shall be 4 inches except for grinder pump
lift stations as allowed under Section 370.410(c)(3).
b) Air and Vacuum Relief Valve
An air relief valve shall be placed at high points in the force
main to prevent air locking. Vacuum relief valves may be
necessary to relieve negative pressure on force mains. Force main
configuration and head conditions shall be evaluated as to the
need for and placement of vacuum relief valves.
c) Termination
Force mains should enter the gravity sewer system at a point not
more than 2 feet above the flow line of the receiving manhole.
d) Design Pressure
The force mains and fittings, including reaction blocking, shall
be designed to withstand normal pressure and pressure surges
(water hammer). The need for surge protection chambers shall be
evaluated.
e) Special Construction
Force main construction near streams or water works structures and
at water main crossings shall meet applicable provisions of
Sections 370.125 and 370.126.
f) Design Friction Losses
1) Friction losses through force mains shall be based on the
Hazen and Williams formula or other acceptable methods. When
the Hazen and Williams formula is used, the value for "C"
shall be 100 for unlined iron or steel pipe for design. For
other smooth pipe materials such as polyvinyl chloride,
polyethylene or lined ductile iron, a higher "C" value not to
exceed 120 may be allowed for design.
2) When initially installed, force mains will have a
significantly higher "C" factor. The effect of the higher
"C" factor should be considered in calculating maximum power
requirements and duty cycle time to prevent damage to the
motor.
g) Identification
Where force mains are constructed of material which might cause
the force main to be confused with potable water mains, the force
main shall be appropriately identified.
h) Flexible Pipe Force Main Embedment
Embedment bedding (haunching and initial backfill as depicted in
ASTM D2321-89, Figure (1)) shall be in accordance with Section
20-2.21 A and 20.2.21 B of Standard Specifications for Water and
Sewer Main Construction in Illinois, 5th ed. (1996)(no later
editions or amendments).
i) Leakage Testing
Leakage testing shall be specified, including testing methods and
leakage limits.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
SUBPART E: SEWAGE TREATMENT WORKS
<BSection 370.500 Plant Location>>
a) General
The following items shall be considered when selecting a plant
site:
1) Proximity to residential areas.
2) Direction of prevailing winds.
3) Necessary routing to provide accessibility by all weather
roads.
4) Area available for expansion.
5) Local zoning requirements.
6) Local soil characteristics, geology, and topography available
to minimize pumping.
7) Access to receiving stream.
8) Compatibility of treatment process with the present and
planned future land use, including noise, potential odors,
air quality, and anticipated sludge processing and disposal
techniques.
9) The requirements of the Illinois Groundwater Protection Act
[415 ILCS 55].
b) Critical Sites
Where a site must be used which is critical with respect to the
items in subsection (a), appropriate measures shall be taken to
minimize adverse impacts.
c) Flood Protection
The treatment works structures, electrical and mechanical
equipment shall be protected from physical damage by the maximum
100 year flood. Treatment works shall remain fully operational
during the 25 year flood. This requirement applies to new
construction and to existing facilities undergoing major
modification. Flood plain regulations of State and Federal
agencies shall be considered.
d) Plant Accessibility
All plant facilities shall be accessible by an all weather road.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.510 Quality of Effluent>>
The required degree of wastewater treatment shall be established by
reference to applicable effluent and water quality standards contained in
35 Ill. Adm. Code Subtitle C, Chapter I unless more stringent limitations
have been established.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.520 Design>>
a) Type of Treatment
1) As a minimum, the following items shall be considered in the
selection of the type of treatment:
A) Present and future effluent requirements.
B) Location and local topography of the plant site.
C) The effects of industrial wastes likely to be
encountered.
D) Ultimate disposal of sludge.
E) System capital costs.
F) System operating and maintenance costs and basic energy
requirements.
G) Existing unit process performance and capacity.
H) Process complexity governing operating personnel
requirements.
I) Environmental impact on present and future adjacent land
use.
2) The plant design shall provide the necessary flexibility to
perform satisfactorily within the expected range of waste
characteristics and volumes.
b) Required Engineering Data for New Process Evaluation
1) The policy of the Agency is to encourage rather than obstruct
the development of any methods or equipment for treatment of
wastewaters. The lack of inclusion in these standards of
some types of wastewater treatment processes or equipment
should not be construed as precluding their use. The Agency
may approve other types of wastewater treatment processes and
equipment under the condition that the operational
reliability and effectiveness of the process or device shall
have been demonstrated with a suitably-sized prototype unit
operating at its design load conditions, to the extent
required.
2) To determine that such new processes and equipment have a
reasonable and substantial chance of success, the Agency will
require the following:
A) Monitoring observations, including test results and
engineering evaluations, demonstrating the efficiency of
such processes.
B) Detailed description of the test methods.
C) Testing, including appropriately-composited samples,
under various ranges of strength and flow rates
(including diurnal variations) and waste temperatures
over a sufficient length of time to demonstrate
performance under climatic and other conditions which
may be encountered in the area of the proposed
installations.
D) Other appropriate information.
3) The Agency will require that appropriate testing be conducted
and evaluations be made under the supervision of a competent
process engineer other than those employed by the
manufacturer or developer.
c) Design Loads
1) Hydraulic Design
A) New Systems
Plans for sewage treatment plants to serve new sewer
systems for municipalities or sewer districts shall be
based upon a design average daily flow of at least 100
gallons per capita, to which must be added industrial
waste volumes. The design also shall include
appropriate allowance for flow conditions determined
under Section 370.122.
B) Existing Systems
Where there is an existing sewer system, the volume and
rates of the existing sewage flows shall be determined.
The determination shall include both dry weather and wet
weather flows. At least one year's flow data should be
used to determine the design flows that are defined in
Section 370.220.
C) Treatment Plant Design Capacity
The treatment plant capacity shall be rated on the
design average flow, selected after any sewer system
rehabilitation, plus appropriate future growth. The
design of treatment units that are not subject to peak
flow requirements shall be based on the design average
flow. For plants subject to high wet weather flows or
overflow detention pumpback flows, the design maximum
flow that the plant is to treat on a sustained basis
must be specified.
2) Organic Design
A) New Systems Minimum Design
i) Domestic waste treatment design shall be on the
basis of at least 0.17 pounds of biochemical oxygen
demand (BOD5) per capita per day and 0.20 pounds of
suspended solids per capita per day.
ii) When garbage grinders are used in areas tributary
to a domestic treatment plant, the design basis
should be increased to 0.22 pounds of BOD5 and
0.25 pounds of suspended solids per capita per
day.
iii) Domestic waste treatment plants that will receive
industrial wastewater flows shall be designed to
include these industrial waste loads.
B) Existing Systems
When an existing treatment works is to be upgraded or
expanded, organic design shall be based upon the actual
strength of the wastewater as determined from
measurements taken in accordance with subsection
(c)(1)(B), with an appropriate increment for growth as
determined under the provisions of subsection (c)(2)(A).
3) Shock Effects
Domestic waste treatment designs shall consider and take into
account the shock effect of high concentrations and diurnal
peaks for short periods on the treatment process,
particularly for small waste treatment plants serving
institutions, restaurants, schools, etc.
4) Design by Analogy
Data from similar existing systems may be utilized in the
case of new systems; however, thorough investigation and
adequate documentation shall be made to establish the
reliability and applicability of such data.
d) Conduits
1) All piping and channels shall be designed to carry the
maximum expected flows. The incoming sewer shall be designed
for unrestricted flow. Bottom corners of the channels must
be filleted. Conduits shall be designed to avoid creation of
pockets and corners where solids can accumulate.
2) Suitable gates should be placed in channels to seal off
unused sections which might accumulate solids. The use of
shear gates is permitted where they can be used in place of
gate valves or sluice gates. Non-corrodible materials shall
be used for these control gates.
e) Arrangement of Units
Component parts of the plant should be arranged for greatest
operating convenience, flexibility, economy, continuity of maximum
effluent quality, and so as to facilitate installation of future
units.
f) Flow Division Control
Flow division control facilities shall be provided as necessary to
insure organic and hydraulic loading control to plant process
units and shall be designed for easy operator access, change,
observation, and maintenance. The use of head boxes equipped with
sharp-crested weirs or similar devices are recommended. The use
of valves for flow splitting is not acceptable. Appropriate flow
measurement shall be incorporated in the flow division control
design.
g) Load Equalization and Attenuation
1) Equalization of hydraulic and organic loads to downstream
treatment units is recommended where the peak hourly load
exceeds 300% of the design average load. Particular
attention shall be given to equalization of pumped flows to
limit hydraulic surges on downstream units.
2) Plants proposed to receive sewage wastes from only
institutions (motels, schools, hospitals, nursing homes,
etc.) or industries which discharge substantially the total
flow in 12 hours or less, shall be designed to include flow
equalization. Where flow equalization facilities are
provided, the design shall include adequate aeration and
mixing equipment to prevent septicity.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.530 Plant Details>>
a) Installation of Mechanical Equipment
The specifications shall be so written that the installation and
initial operation of major items of mechanical equipment will be
inspected and approved by a representative of the manufacturer.
b) Bypasses
Properly located and arranged bypass structures and piping shall
be provided so that each unit of the plant can be removed from
service independently. The bypass design shall facilitate plant
operation during unit maintenance and emergency repair so as to
minimize deterioration of effluent quality and insure rapid
process recovery upon return to normal operational mode.
c) Unit Bypass and Wastewater Pumpage During Construction
Final plans and specifications for upgrading or expanding existing
treatment plants shall include construction scheduling of any unit
bypassing, and appropriate temporary wastewater pumpage acceptable
to the Agency to minimize temporary water quality degradation.
Refer to Section 370.260.
d) Drains and Buoyancy Protection
1) Means shall be provided to dewater each unit. Pipes subject
to clogging shall be provided with means for mechanical
cleaning or flushing.
2) Due consideration should be given to the possible need for
hydrostatic pressure relief devices to prevent flotation of
structures.
e) Construction Materials
Due consideration should be given to the selection of materials
which are to be used in sewage treatment works because of the
possible presence of hydrogen sulfide and other corrosive gases,
greases, oils, and similar constituents frequently present in
sewage. This is particularly important in the selection of metals
and paints. Dissimilar metals should be avoided to minimize
galvanic action.
f) Painting
The use of paints containing mercury should be avoided. In order
to facilitate identification of piping, particularly in the large
plants, it is suggested that the different lines be color coded.
The following color scheme is recommended for purposes of
standardization:
1) Sludge line - brown
2) Gas line - orange
3) Potable water line - blue
4) Non-potable water line - blue with 3 inch yellow band spaced
30 inches apart
5) Chlorine line - yellow
6) Sewage line - gray
7) Compressed air line - green
8) Water lines for heating digesters or buildings - blue with a
6-inch red band spaced 30 inches apart
9) Sulfur dioxide line - yellow with red bands.
10) The contents shall be stenciled on the piping, labeling the
contents in a contrasting color.
g) Operating Equipment
A complete outfit of tools, accessories (such as portable pump and
ventilation blowers, etc.), and spare parts necessary for the
plant operators use shall be provided. Readily accessible storage
space and work bench facilities shall be provided. Consideration
shall be given to provision of a garage storage area for large
equipment storage, maintenance, and repair.
h) Erosion Control During Construction
Effective site erosion control shall be provided during
construction.
i) Grading and Landscaping
Upon completion of the plant, the ground should be graded and
seeded. Concrete or gravel walkways should be provided for access
to all units. Where possible, steep slopes should be avoided to
prevent erosion. Surface water shall not be permitted to drain
into any unit. Particular care shall be taken to protect
trickling filter beds, sludge beds, and intermittent sand filters
from storm water runoff. Landscaping shall be provided when a
plant must be located near residential areas.
j) Confined Spaces
The number of confined spaces should be minimized for safety
purposes.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.540 Plant Outfalls>>
a) Discharge Impact Control
The outfall sewer shall be designed to discharge to the receiving
stream in a manner acceptable to the Agency. Consideration
should be given in each case to the following:
1) Preference for free fall or submerged discharge at the site
selected.
2) Utilization of cascade aeration of effluent discharge to
increase dissolved oxygen.
3) Limited or complete across-stream dispersion as needed to
protect aquatic life movement and growth in the immediate
reaches of the receiving stream.
b) Design and Construction
The outfall sewer shall be so constructed and protected against
the effects of flood water, waves, ice, or other hazards as to
reasonably insure its structural stability and freedom from
stoppage. A manhole should be provided at the shore end of all
gravity sewers extending into the receiving waters. Hazards to
navigation shall be considered in designing outfall sewers.
c) Sampling Provisions
All outfalls shall be designed so that a sample of the effluent
can be readily obtained at a point after the final treatment
process and before discharge to or mixing with the receiving
waters.
<BSection 370.550 Essential Facilities>>
a) Emergency Power or Pumping Facilities
1) All plants shall be provided with an alternate source of
electric power or pumping capability to allow continuity of
operation during power failures. Methods of providing power
or pumping capability include:
A) The connection to at least 2 independent public utility
sources such as substations. A power line from each
substation into the treatment plant with capability for
switchover to the second power source by plant operating
personnel will be required.
B) Portable or in place internal combustion engine
equipment which will generate electrical or mechanical
energy. Refer to Section 370.136(d).
C) Portable pumping equipment when only emergency pumping
is required. Refer to Section 370.136(d).
2) Standby Generating Capacity Requirements
Standby generating capacity normally is not required for
aeration equipment used in the activated sludge process. In
cases where a history of long term (4 hours or more) power
outages have occurred, auxiliary power for minimum aeration
of the activated sludge will be required.
3) Degree of Treatment Required
No reduction in degree of treatment due to power outages will
be allowed when the wastewater is to be treated by
installations using trickling filters, waste stabilization
ponds and/or other low energy usage treatment devices.
4) Continuity of Disinfection
The design shall provide for continuous disinfection during
all power outages, if required due to critical outfall
locations and receiving waters.
5) Continuity of Dechlorination
For facilities using dechlorination equipment, the design
shall provide for continuous dechlorination during all power
outages, if required due to critical outfall locations and
receiving waters.
b) Water Supply
1) General
An adequate supply of potable water under pressure should be
provided for use in the laboratory and general cleanliness
around the plant. No piping or other connections shall exist
in any part of the treatment works which, under any
conditions, might cause the contamination of a potable water
supply.
2) Direct Connections
A) Potable water from a municipal or separate supply may be
used directly at points above grade for the following
hot and cold supplies:
i) Lavatory sink
ii) Water closet
iii) Laboratory sink (with vacuum breaker)
iv) Shower
v) Drinking fountain
vi) Eye wash fountain
vii) Safety shower
viii) Fire protection sprinklers
B) Hot water for any of the above units shall not be taken
directly from a boiler used for supplying hot water to a
sludge heat exchanger or digester heating unit.
3) Indirect Connections
A) Where a potable water supply is to be used for any
purpose in a plant other than those listed in subsection
(b)(2)(A), a break tank, pressure pump and pressure tank
shall be provided. Water shall be discharged to the
break tank through an air-gap at least 6 inches above
the maximum flood line or the spill line of the tank,
whichever is higher. A sketch of an acceptable break
tank is contained in Appendix G, Figure No. 4. In-line
backflow preventers are not acceptable.
B) A sign shall be permanently posted at every hose bib,
faucet, or sill cock located on the water system beyond
the break tank to indicate that the water is not safe
for drinking.
4) Separate Potable Water Supply
Where it is not possible to provide potable water from a
public water supply, a separate well may be provided.
Location and construction of the well should comply with
requirements of the governing State and local regulations.
Requirements governing the use of the supply are those
contained in subsections (b)(2) and (b)(3).
5) Separate Non-Potable Water Supply
Where a separate non-potable water supply is to be provided,
a break tank will not be necessary, but all sill cocks and
hose bibs shall be posted with a permanent sign indicating
the water is not safe for drinking.
c) Sanitary Facilities
Toilet, shower, and lavatory should be provided in sufficient
numbers and at convenient locations to serve the expected plant
personnel.
d) Floor Slope
Floor surfaces shall be sloped adequately to a point of drainage.
e) Stairways
Stairways shall be installed in lieu of ladders for access to
those units requiring inspection and maintenance, including but
not limited to trickling filters, digesters, aeration tanks,
clarifiers and tertiary filters. Spiral or winding stairs are
permitted only for secondary access where dual means of egress are
provided. Stairways shall have slopes between 30 and 40 degrees
from the horizontal to facilitate carrying samples, tools, etc.
Each tread and riser shall be of uniform dimension in each flight.
Minimum tread run shall not be less than 9 inches. The sum of the
tread run and riser shall not be less than 17 nor more than 18
inches. A flight of stairs shall consist of not more than a 12
foot continuous rise without a platform.
f) Flow Measurement
1) Flow measurement facilities shall be provided so as to
measure the following flows:
A) Plant effluent flow.
B) Plant influent flow, if significantly different from
plant effluent flow, such as for lagoons and plants with
excess flow storage or flow equalization.
C) Excess flow treatment facility discharges.
D) Other flows required to be monitored under the
provisions of an NPDES discharge permit.
E) Flows required for plant operational control, including
but not limited to return activated sludge flow, waste
activated sludge flow, recirculation flow and recycle
flows.
2) Indicating, totalizing and recording flow measurement devices
shall be provided for all mechanical plants for all flows
except those specified in subsection (f)(1)(E) above. Flow
measurement equipment for lagoon systems shall consist of, at
a minimum, elapsed time meters used in conjunction with
pumping rate test or calibrated weirs. All flow measurement
equipment must be sized to function effectively in the full
range of flows expected and shall be protected against
freezing.
3) Flow measurement equipment including entrance and discharge
conduit configuration and critical control elevations shall
be designed to ensure that the required hydraulic conditions
necessary for accurate measurement are provided. Conditions
that must be avoided include turbulence, eddy currents, air
entrainment, etc., that upset the normal hydraulic conditions
that are necessary.
g) Sampling Equipment
Effluent composite sampling equipment shall be provided at all
mechanical plants and at other facilities where necessary to meet
discharge permit monitoring requirements.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.560 Safety>>
a) Adequate provision shall be made to effectively protect the
operator and visitors from hazards. The following shall be
provided to fulfill the particular needs of each plant:
1) Enclosure of the plant site with a fence designed to
discourage the entrance of unauthorized persons and animals.
2) Installation of hand rails and guards around all tanks, pits,
stairwells, and other hazardous structures.
3) Provision of first aid equipment at marked locations.
4) Posting of "No Smoking" signs in hazardous areas.
5) Protective clothing and equipment such as air packs, goggles,
gloves, hard hats, safety harnesses and hearing protection.
6) Provision of portable blower and sufficient hose.
7) Portable lighting equipment that complies with the National
Electrical Code.
8) Appropriately placed warning signs for slippery areas,
non-potable water fixtures, low head clearance areas, open
service manhole, hazardous chemical storage areas, flammable
fuel storage areas, etc.
9) Smoke and fire detectors, fire extinguishers, and appropriate
waste receptacles.
10) Provisions for confined space entry in accordance with the
requirements of the Occupational Safety and Health Act and
any other applicable regulatory requirements.
b) Hazardous Chemical Handling
1) Containment Materials
The materials utilized for storage, piping, valves, pumping,
metering, splash guards, etc., shall be specially selected
considering the physical and chemical characteristics of each
hazardous or corrosive chemical.
2) Secondary Containment and Storage
A) Wet and Dry Chemicals
Chemical storage areas shall be enclosed in dikes or
curbs which will contain the stored volume until it can
be safely transferred to alternate storage or released
to the wastewater at controlled rates which will not
damage facilities, inhibit the treatment processes, or
contribute to stream pollution. Liquid polymer should
be similarly contained to reduce areas with slippery
floors, especially to protect travelways. Non-slip
floor surfaces are desirable in polymer handling areas.
B) Liquified Gas Chemicals
Chlorine and sulfur dioxide cylinder and container
storage shall meet the requirements of Sections 370.1020
and 370.1040. Ammonia gas cylinder isolation shall be
provided. Gas cylinder storage facilities shall be
equipped with appropriate alarm system and emergency
repair equipment and control system.
3) Eye Wash Fountains and Safety Showers
A) Eye wash fountains and safety showers utilizing potable
water shall be provided in the laboratory and on each
floor level or work location involving hazardous or
corrosive chemical storage, mixing (or slaking),
pumping, metering, or transportation unloading. These
facilities are to be as close as practical to possible
chemical exposure sites and are to be fully useful
during all weather conditions. The eye wash fountains
shall be supplied with water of moderate temperature
(50 - 90 Fahrenheit (F)), separate from the hot water
supply, suitable to provide 15 minutes to 30 minutes of
continuous irrigation of the eyes.
B) The emergency showers shall be capable of discharging 30
to 50 gallons per minute (gpm) of water at moderate (50
- 90 F) temperature at pressures of 20 to 50 pounds
per square inch (psi). The eye wash fountains and
showers shall be no more than 25 feet from points of
caustic exposure.
4) Splash Guards
All pumps or feeders for hazardous or corrosive chemicals
shall have guards which will effectively prevent spray of
chemicals into space occupied by personnel. The splash
guards are in addition to guards to prevent injury from
moving or rotating machinery parts.
5) Piping, Labeling, Coupling Guards, Location
A) All piping containing or transporting corrosive or
hazardous chemicals shall be identified with labels
every ten feet and with at least two labels in each
room, closet, or pipe chase. Color coding may also be
used, but is not an adequate substitute for labeling.
B) All connections (flanged or other type), except adjacent
to storage or feeder areas, shall have guards which will
direct any leakage away from space occupied by
personnel. Pipes containing hazardous or corrosive
chemicals should not be located above shoulder level
except where continuous drip collection trays and
coupling guards will eliminate chemical spray or
dripping onto personnel.
6) Protective Clothing and Equipment
The following items of protective clothing or equipment shall
be available and utilized for all operations or procedures
where their use will minimize injury hazard to personnel:
A) Air pack breathing apparatus for protection against
chlorine and other toxic gases.
B) Chemical workers' goggles or other suitable goggles.
(Safety glasses are insufficient.)
C) Face masks or shields for use over goggles.
D) Dust masks to protect the lungs in dry chemical areas.
E) Rubber gloves.
F) Rubber aprons with leg straps.
G) Rubber boots (leather and wool clothing should be
avoided near caustics).
H) Safety harness and line.
7) Warning Systems and Signs
A) Facilities shall be provided for automatic shutdown of
pumps and sounding of alarms when failure occurs in a
pressurized chemical discharge line.
B) Warning signs requiring use of goggles and dust masks
shall be located near chemical unloading stations,
pumps, and other points of frequent hazard.
8) Dust Collection
Dust collection equipment shall be provided where dry
chemicals are stored or used to protect personnel from dusts
injurious to the lungs or skin and to prevent polymer dust
from settling on walkways which become slick when wet.
9) Container Identification
The identification and hazard warning data included on
shipping containers, when received, shall appear on all
containers (regardless of size or type) used to store, carry,
or use a hazardous substance. Sewage and sludge sample
containers should be adequately labeled. Below is a suitable
label to identify a sewage sample as a hazardous substance:
<PRaw Sewage>>
Sample Point No. <P >>
Contains Harmful Bacteria.
May contain hazardous or
toxic material.
Do not drink or swallow.
Avoid contact with openings
or breaks in the skin.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.570 Laboratory>>
a) All treatment works shall include a laboratory for making the
necessary analytical determinations and operating control tests,
except for those plants utilizing only processes not requiring
laboratory testing for plant control and satisfactory off-site
laboratory provisions are made to meet the permit monitoring
requirements. For plants where a fully equipped laboratory is not
required, the requirements for utilities and equipment such as
fume hoods may be reduced or omitted.
b) The laboratory shall have sufficient size, bench space, equipment
and supplies to perform all self-monitoring analytical work
required by discharge permits, and to perform the process control
tests necessary for good management of each treatment process
included in the design.
c) The facilities and supplies necessary to perform analytical work
to support industrial waste control programs will normally be
included in the same laboratory. The laboratory size and
arrangement must be sufficiently flexible and adaptable to
accomplish these assignments. The layout should consider future
needs for expansion in the event that more analytical work is
needed.
d) Location and Space
1) The laboratory should be located on ground level, easily
accessible to all sampling points, with environmental control
as an important consideration. It shall be located in a
separate room or building away from vibrating machinery or
equipment which might have adverse effects on the performance
of laboratory instruments or the analyst, or shall be
designed to prevent structural transmission of machine
vibration. The floor and wall construction shall be
designed to keep out machine noise (blowers, pumps, etc.).
The following minimum conditions shall be met:
A) Blowers, pumps, etc., must be located on a separate
floor pad.
B) Common walls between machinery rooms must be
double-walled with sound insulation between the walls.
Connecting doors or windows to machinery rooms are not
acceptable.
C) Common attic space shall be blocked off and effective
sound proof material provided in the ceiling.
2) A minimum of 400 square feet of floor space should be
allocated for the laboratory. Less space may be allowed if
the sampling and analysis program, approved by the Agency,
does not require a full-time laboratory chemist. If more
than two persons normally will be working in the laboratory
at any given time, 100 square feet of additional space should
be provided for each additional person. Bench-top working
surface should occupy at least 35 percent of the total floor
space.
3) Minimum ceiling height should be 8 feet 6 inches. If
possible, this height should be increased to provide for the
installation of wall-mounted water stills, distillation
racks, and other equipment with extended height requirements.
4) Additional floor and bench space should be provided to
facilitate performance of analysis of industrial wastes, as
required by the discharge permit and the utilities industrial
waste pretreatment program. The above minimum space does not
provide office or administration space.
e) Materials
1) Ceilings
Acoustical tile should be used for ceilings except in high
humidity areas where they should be constructed of cement
plaster. Materials containing asbestos shall not be used.
2) Walls
For ease of maintenance and a pleasant working environment,
light-colored ceramic tile should be used from floor to
ceiling for all interior walls.
3) Floors
Floor surface materials shall be fire resistant and highly
resistant to acids, alkalies, solvents, and salts.
4) Doors
A) Two exit doors should be located to permit a straight
egress from the laboratory, preferably at least one to
outside the building. Panic hardware should be used.
They should have large glass windows for easy visibility
of approaching or departing personnel.
B) Automatic door closers should be installed; swinging
doors should not be used.
C) Flush hardware should be provided on doors if cart
traffic is anticipated. Kick plates are also
recommended.
f) Cabinets and Bench Tops
1) Cabinets
A) Wall-hung cabinets are useful for dust-free storage of
instruments and glassware.
B) Units with sliding glass doors are preferable. They
should be hung so the top shelf is easily accessible to
the analyst. Thirty inches from the bench top is
recommended.
C) One or more cupboard-style base cabinets should be
provided for storing large items; however, drawer units
are preferred for the remaining cabinets. Drawers
should slide out so that entire contents are easily
visible. They should be provided with rubber bumpers
and with stops which prevent accidental removal.
Drawers should be supported on ball bearings or nylon
rollers which pull easily in adjustable steel channels.
All metal drawer fronts should be double-wall
construction. All cabinet shelving should be acid
resistant and adjustable from inside the cabinet.
2) Bench Tops
Generally, bench-top height should be 36 inches. However,
areas to be used exclusively for sit-down type operations
should be 30 inches high and include kneehole space.
One-inch overhangs and drip grooves should be provided to
keep liquid spills from running along the face of the
cabinet. Tops should be furnished in large sections, 1 1/4
inches thick. They should be field joined into a continuous
surface with acid, alkali, and solvent-resistant cements
which are at least as strong as the material of which the top
is made.
3) Utility Accessories
Water, gas, air, and vacuum service fixtures; traps,
strainers, overflows, plugs and tailpieces; and all
electrical service fixtures shall be supplied with the
laboratory furniture.
g) Hoods
Fume hoods to promote safety and canopy hoods over heat-releasing
equipment shall be installed.
1) Fume Hoods
A) Location
i) Fume hoods should be located where air disturbance
at the face of the hood is minimal. Air
disturbance may be created by persons walking past
the hood; by heating, ventilating or
air-conditioning systems; by drafts from opening or
closing a door; etc.
ii) Safety factors should be considered in locating a
hood. If a hood is situated near a doorway, a
secondary means of egress must be provided. Bench
surfaces should be available next to the hood so
that chemicals need not be carried long distances.
B) Design and Materials
i) The selection of fume hoods, their design and
materials of construction, must be made by
considering the variety of analytical work to be
performed and the characteristics of the fumes,
chemicals, gases, or vapors that will or may be
released. Special design and construction is
necessary if perchloric acid use is anticipated.
Consideration should be given for providing more
than one fume hood to minimize potential hazardous
conditions throughout the laboratory.
ii) Fume hoods are not appropriate for operation of
heat-releasing equipment that does not contribute
to hazards, unless they are provided in addition to
those needed to perform hazardous tasks.
C) Fixtures
i) One cup sink should be provided inside each fume
hood.
ii) All switches, electrical outlets, and utility and
baffle adjustment handles should be located outside
the hood. Light fixtures should be
explosion-proof.
D) Exhaust
Continuous duty exhaust capability should be provided.
Exhaust fans should be explosion-proof. Exhaust
velocities should be checked when fume hoods are
installed.
E) Alarms
A buzzer for indicating exhaust fan failure and a static
pressure gauge should be placed in the exhaust duct. A
high temperature sensing device located inside the hood
should be connected to the buzzer.
2) Canopy Hoods
Canopy hoods should be installed over the bench-top areas
where hot plate, steam bath, or other heating equipment or
heat-releasing instruments are used. The canopy should be
constructed of steel, plastic, or equivalent material, and
finished with enamel to blend with other laboratory
furnishings.
h) Sinks
1) The laboratory should have a minimum of 3 sinks (not
including cup sinks). At least 2 of them should be
double-well with drainboards. Additional sinks should be
provided in separate work areas as needed, and identified for
the use intended.
2) Waste openings should be located toward the back so that a
standing overflow will not interfere. All water fixtures on
which hoses may be used should be provided with reduced zone
pressure backflow preventers to prevent contamination of
water lines.
3) The sinks should be constructed of material highly resistant
to acids, alkalies, solvents, and salts, and should be
abrasion and heat resistant, non-absorbent, light in weight
and have all appropriate characteristics for laboratory
applications. Traps should be made of glass, plastic, or
lead and easily accessible for cleaning.
i) Ventilation and Lighting
1) Laboratories shall be separately air conditioned and
dehumidification shall be provided where laboratory control
tests procedures will be affected by high humidity
conditions. Separate exhaust ventilation outlet locations
(fume and heat hoods, room air, etc.) shall be provided
remote from ventilation intakes.
2) Adequate lighting, free from shadows, shall be provided to
permit reading of laboratory instrument dials, glassware
calibrations, etc.
j) Gas and Vacuum
1) Natural or bottled gas should be supplied to the laboratory.
Digester gas should not be used.
2) An adequately-sized line source of vacuum should be provided
with outlets available throughout the laboratory.
k) Balance and Table
An analytical balance of the automatic, digital readout, single
pan, 0.1 milligram sensitivity type shall be provided. A heavy
special-design balance table which will minimize vibration of the
balance shall be provided. It shall be located as far as
practical from windows, doors, or other sources of drafts or air
movements, so as to minimize undesirable impacts from these
sources upon the balance.
l) Equipment, Supplies and Reagents
The laboratory shall be provided with all of the equipment,
supplies, and reagents that are needed to carry out all of the
facility's analytical testing requirements. Discharge permit,
process control, and industrial waste monitoring requirements
must be considered when specifying equipment needs. References
such as Standard Methods and the USEPA Analytical Procedures
Manual should be consulted prior to specifying equipment items.
m) Power Supply Regulation
1) To eliminate voltage fluctuation, electrical lines supplying
the laboratory should be controlled with a constant voltage,
harmonic neutralized type of transformer. This transformer
should contain less than 3% total root mean square (rms)
harmonic content in the output, should regulate to <P+>>1% for an
input range of <P+>>15% of nominal voltage, with an output of 118
volts. For higher voltage requirements, the 240-volt lines
should be similarly regulated.
2) Electrical devices in the laboratory not requiring a
regulated supply (i.e., ordinary resistance heating devices)
that are non-portable may be wired to an unregulated supply.
n) Laboratory Grade Water Source
A laboratory grade water source, with at least one gallon per hour
capacity, shall be installed complete with all utility
connections. The type of treatment used to produce laboratory
grade water shall be based on the quality of water required for
the tests to be performed at the plant. Laboratory water
treatment devices shall be constructed of materials that are
compatible with the water to be treated and produced.
o) Laboratory Safety Equipment
Laboratory safety equipment shall be provided in accordance with
the requirements of Section 370.560(a)(3), (a)(9), (b)(3) and
(b)(6).
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
SUBPART F: PRELIMINARY TREATMENT
<BSection 370.600 General Considerations>>
a) Safety
Safety Features Relative to Location
1) Railings and Gratings
A) Manually cleaned channels shall be protected by guard
railings and deck gratings, with adequate provisions for
removal or opening to facilitate raking.
B) Mechanically cleaned channels shall be protected by
guard railings and deck gratings. Consideration should
also be given to temporary access arrangements to
facilitate maintenance and repair.
2) Mechanical Devices
A) Mechanical screening equipment shall have adequate
removable enclosures to protect personnel against
accidental contact with moving parts and to prevent
dripping in multi-level installations.
B) A positive means of locking out each mechanical device
shall be provided.
3) Units and Equipment in Deep Pits
Manually cleaned screens located in pits deeper than 4 feet
shall be provided with stairway access, adequate lighting and
ventiliation, and convenient and adequate means for removing
screenings. Access ladders may be used instead of steps in
pits less than 4 feet deep. Hoisting or lifting equipment
shall be used where necessitated by the depth of the pit or
the amount of material to be removed.
4) In Buildings
Units and equipment installed in buildings where other
equipment or offices are located shall be isolated from the
rest of the building, and shall be provided with separate
outside entrances and separate and independent means of
ventilation.
5) Ventilation
A) Adequate ventilation shall be provided for installations
described in subsections (a)(3) and (4). Ventilation
may either be continuous or intermittent. If
continuous, ventilation shall provide at least 12
complete air changes per hour; if intermittent,
ventilation shall provide at least 30 complete air
changes per hour.
B) Where the pit is deeper than 4 feet mechanical
ventilation is required, and the air shall be forced
into the screen pit area rather than exhausted from the
screen pit. The maximum distance from the fresh air
discharge and the working deck floor shall be 24 inches.
Dampers should not be used on fresh air ducts.
Obstructions in air ducts should be avoided to prevent
clogging. Air intake screens (bird and insect) shall be
located so as to be easily accessible for cleaning.
C) Switches for operation of ventilation equipment should
be marked and located at the entrance to the screen pit
area. All intermittently operated ventilating equipment
shall be interconnected with the respective lighting
system. Consideration should be given to automatic
controls where intermittent operation is used. The
manual lighting-ventilation switch shall override the
automatic controls.
D) The fan wheel shall be fabricated from non-sparking
material. Refer to Section 370.610(a)(3)(C) for motor
and electrical requirements.
6) Electrical Fixtures
Electrical fixtures and controls in enclosed places where gas
may accumulate shall comply with Section 370.610(a)(3)(C).
b) Communition
Communition or other in-stream shredding of sewage solids shall be
followed by primary settling or fine screening devices to remove
the shredded stringy materials prior to the activated sludge
process to minimize operational problems associated with
reaglomeration of stringy materials.
c) Channels
Channels shall be equipped with the necessary gates to divert flow
from any one unit. Provisions must also be made for dewatering
each unit. Channels preceding and following screens shall be
shaped and filleted as necessary to eliminate settling of solids.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.610 Screening Devices>>
a) Bar Racks and Screens
1) Where Required
Screening of raw sewage shall be provided at all mechanical
treatment works. For lift station applications, see Subpart
D.
2) Design and Installation
A) Manually Cleaned Screens
Clear openings for manually cleaned screens between bars
should be from 1 to 1 3/4 inches. Design and
installation shall be such that they can be conveniently
cleaned. An accessible platform shall be provided on
which the operator may rake screenings easily and
safely. Suitable drainage facilities with return flow
to process shall be provided for the platform.
B) Mechanical Screens
Clear openings for mechanically cleaned screens may be
as small as practical to assure the proper operation and
maintenance of treatment facilities. Mechanical screens
shall be located so as to be protected from freezing and
to facilitate maintenance.
C) Velocities Through Screens
For manually or mechanically raked bar screens the
maximum velocities during peak flow periods should not
exceed 2.5 feet per second. The velocity shall be
calculated from a vertical projection of the screen
openings on the cross-sectional area between the invert
of the channel and the flow line. Excessive head loss
through the screen, which may affect upstream flow
measurement or bypassing, shall be taken into account.
D) Invert
The screen channel invert shall be at least 3 inches
below the invert of the incoming sewers. To prevent
jetting action, the length and/or construction of the
screen channel shall be adequate to reestablish
hydraulic flow pattern following the drop in elevation.
E) Slope
Manually cleaned screens should be placed on a slope of
30 to 45 degrees with the horizontal.
3) Control Systems
A) Timing Devices
All mechanical units which are operated by timing
devices should be provided with auxiliary controls which
will set the cleaning mechanism in operation at
predetermined high water marks.
B) Manual Override
Automatic controls shall be supplemented by a manual
override.
C) Electrical Fixtures and Controls
Electrical fixtures and controls in enclosed places
where gas may accumulate shall comply with the National
Electrical Code requirements for Class I, Group D,
Division I locations.
4) Disposal of Screenings
A) Amply-sized, vector-proof facilities shall be provided
for removal, handling and storage of screenings in a
sanitary manner. Suitable drainage facilities shall be
provided for the storage areas with drainage returned to
process. The return of ground screenings to the sewage
flow is unacceptable.
B) Disposal shall be in accordance with 35 Ill. Adm. Code
700 and shall be discussed in the plan documents.
b) Auxiliary Screens
Where mechanically operated screening is used, auxiliary manually
cleaned screens shall be provided. Design shall include
provisions for automatic diversion of the entire sewage flow
through the auxiliary screens should the regular units fail.
Refer to subsection (a)(2).
c) Fine Screens
Fine screens may be used in lieu of primary sedimentation
providing that subsequent treatment units are designed on the
basis of anticipated screen performance. Fine screens should not
be considered equivalent to primary sedimentation. Where fine
screens are used, additional removal of floatable oils and greases
shall be provided if they will adversely affect the function of
downstream treatment units.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.620 Grit Removal Facilities>>
a) Where Required
Grit removal facilities should be provided for all sewage
treatment plants and are required for plants receiving sewage from
combined sewers or from sewer systems receiving substantial
amounts of grit. If a plant serving a separate sewer system is
designed without grit removal facilities, the design shall include
provision for future installation. Consideration shall be given
to possible damaging effects on pumps, and other preceding
equipment, and the need for additional storage capacity in
treatment units where grit is likely to accumulate.
b) Location
Grit removal facilities should be located ahead of pumps. In such
cases, coarse bar racks should be placed ahead of mechanically
cleaned grit removal facilities. Comminution equipment, when used,
shall be located downstream of the grit facility in order to
reduce the operation and maintenance problems associated with
grit.
c) Type and number of units
1) The selection of the type of grit removal shall be based on
necessary flexibility of velocity control to remove the
selected size grit particulates through the range of expected
plant flows, the volume of grit expected, and available area
and hydraulic gradient limits at the site. Aerated or area
type grit removal units equipped with adequate controls for
operational flexibility are recommended where flow rates and
grit characteristics and volume are expected to vary widely.
2) Plants treating wastes from combined sewers shall have at
least one, preferably two or more, mechanically cleaned grit
removal units, with provision for unit bypassing. A single
manually cleaned or mechanically cleaned grit chamber with
unit bypass is acceptable for small sewage treatment plants
serving separate sanitary sewer systems. Minimum facilities
for larger plants serving separate sanitary sewers shall be
at least one mechanically cleaned unit with a unit bypass.
d) Design Factors
1) Channel Type Units
A) Turbulence Control
The equipment and inlet and outlet structures shall be
designed to minimize turbulance throughout the channel.
B) Velocity and Detention
Channel-type chambers shall be designed to provide
controlled velocities as close as possible to 1 foot per
second. The detention period shall be based on the size
of particle to be removed.
2) Aerated Units
A) Inlet
The inlet shall be located and arranged to prevent short
circuiting to the outlet and oriented to the unit flow
pattern so as to provide for adequate scouring
segregation of organic and grit materials prior to
discharge.
B) Detention
A detention time of at least 3 minutes at design peak
flow should be provided.
C) Air Supply
Air should be supplied at 5 cubic feet per minute (cfm)
per foot of tank length. The rate of air supplied shall
be widely variable so as to maximize unit process
effectiveness.
3) Grit Washing and Freeze Protection
All facilities not provided with positive velocity control
should include means for grit washing to further separate
organic and inorganic materials. Grit elevator and washing
facilities shall be housed to prevent freezing. Provision
for adequate heating and ventilation shall be provided to
prevent corrosion.
4) Drains
Provisions should be made for dewatering each unit.
5) Water
An adequate supply of water under pressure shall be provided
for clean up.
e) Grit Removal
Grit removal facilities located in pits shall be provided with
mechanical equipment for pumping or hoisting grit to ground level.
Pits deeper than 4 feet shall be provided with stairway access. An
approved-type elevator or manlift may be desirable in some
locations. Adequate ventilation, as described in Section
370.600(a)(5), and lighting shall be provided for pits that are
deeper than 4 feet or are within an enclosed area.
f) Grit Handling
Impervious, non-slip, working surfaces with drains back to process
shall be provided for grit handling areas. Safety handrails shall
be provided around the working platform areas. If grit is to be
transported, the conveying equipment shall be designed to avoid
loss of material and protection from freezing. Grit disposal
methods shall be in compliance with 35 Ill. Adm. Code 700 and
shall be described in the plan documents.
g) Electrical
All electrical fixtures and controls in enclosed or below grade
grit removal areas where hazardous gases may accumulate shall meet
the requirements of the National Electrical Code (1996) for Class
1, Group D, Division 1 locations.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.630 Pre-Aeration>>
Pre-aeration of sewage to reduce septicity may be required in special
cases.
(Source: Added at 21 Ill. Reg. 12444, effective August 28, 1997)
SUBPART G: SETTLING
<BSection 370.700 General Considerations>>
a) Number of Units
Multiple units capable of independent operation are desirable and
shall be provided in all plants where design average flows exceed
100,000 gallons per day. Plants not having multiple units shall
include other provisions to assure continuity of treatment.
b) Arrangement
Settling tanks shall be arranged in accordance with Sections
370.520(e) and 370.710(g).
c) Flow Distribution
Effective flow splitting devices and control appurtenances shall
be provided to insure proper organic and hydraulic proportion of
flow to each unit. Refer to Section 370.520(f).
d) Tank Configuration
Consideration should be given to the probable flow pattern in the
selection of tank size and shape, and inlet and outlet type and
location.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.710 Design Considerations>>
a) Dimensions
The minimum length of flow from inlet to outlet should be 10 feet
unless special provisions are made to prevent short circuiting.
The sidewater depth for primary clarifiers shall be as shallow as
practicable, but not less than 7 feet. Clarifiers following the
activated sludge process shall have sidewater depths of at least
12 feet to provide adequate separation zone between the sludge
blanket and the overflow weirs. Clarifiers following fixed film
reactors shall have sidewater depth of at least 7 feet.
b) Surface Settling Rates (Overflow Rates)
The hydraulic design of settling tanks shall be based on the
anticipated peak hourly flow.
1) Primary and Bypass Settling Tanks
A) Primary Settling
Some indication of BOD removals may be obtained by
reference to Appendix E, Figure No. 2. The figure
should not be used to design units which receive
wastewaters which have BOD and total suspended solids
concentrations which are substantially different from
normal domestic sewage. The operating characteristics
of such units should be established by appropriate field
and laboratory tests. If activated sludge is wasted to
the primary settling unit, then the design surface
settling rate shall not exceed 1,000 gallons per day per
square foot based on design peak hourly flow, including
all flows to the unit. Refer to subsection (b)(3) and
Section 370.820.
B) Combined Sewer Overflow and Bypass Settling
The maximum surface settling rate shall not exceed 1,800
gallons per day per square foot based on peak hourly
flow. Minimum liquid depth shall not be less than 10
feet. Minimum detention shall not be less than one
hour. The minimum length of flow from inlet baffle to
outlet should be 10 feet, unless special provisions are
made to prevent short-circuiting.
2) Intermediate Settling Tanks
Surface settling rates for intermediate settling tanks
following series units of fixed film reactor processes should
not exceed 1500 gallons per day per square foot based on
design peak hourly flow. Surface settling rates for
intermediate settling tanks following the activated sludge
process shall not exceed 1000 gallons per day per square foot
based on design peak hourly flow.
3) Final Settling Tanks
Settling tests should be conducted wherever a pilot study of
biological treatment is warranted by unusual waste
characteristics or treatment requirements. Testing shall be
done where proposed loadings go beyond the limits set forth
in subsections (b)(3)(A) and (b)(3)(B).
A) Final Settling Tanks - Fixed Film Biological Reactors
Surface settling rates for settling tanks following
trickling filters or rotating biological contactors
shall not exceed 1000 gallons per day per square foot
based on design peak hourly flow.
B) Final Settling Tanks - Activated Sludge
i) Multiple units capable of independent operation
shall be provided at all plants. To perform
properly while producing a concentrated return
flow, activated sludge settling tanks must be
designed to meet thickening as well as solids
separation requirements.
ii) Since the rate of recirculation of return sludge is
quite high in activated sludge processes, surface
settling rate and weir overflow rate should be
adjusted for the various processes to minimize the
problems with sludge loadings, density currents,
inlet hydraulic turbulence, and occasional poor
sludge settleability.
iii) The hydraulic loadings shall not exceed 1000
gallons per day per square foot based on design
peak hourly flow, and 800 gallons per day per
square foot based on peak hourly flow for separate
activated sludge nitrification stage. Refer to
Section 370.1210(c)(4).
iv) The solids loading shall not exceed 50 pounds
solids per day per square foot at the design peak
hourly rate.
v) Flow equalization is recommended where the peak
hourly load exceeds 300% of the design average
load.
C) Rectangular Units
Rectangular final settling tanks following the activated
sludge process frequently exhibit poor solids separation
characteristics and should therefore be avoided. If
land availability or other local conditions mandate the
use of rectangular final clarifiers following the
activated sludge process, the following design
modifications shall be made:
i) Within practicable limits, length shall be
approximately equal to the width.
ii) Excess weir length shall be provided.
iii) Baffles shall be provided to interrupt
longitudinal density currents.
iv) Weir placement shall be adjustable, so as to allow
optimization of the upflow takeoff points.
c) Inlet Structures
Inlets and inlet baffling should be designed to dissipate the
inlet velocity, to distribute the flow equally both horizontally
and vertically and to prevent short circuiting. Channels should
be designed to maintain a velocity of at least one foot per second
at one-half the design flow. Corner pockets and dead ends should
be eliminated and corner fillets or channeling used where
necessary. Provisions shall be made for prevention or removal of
floating materials in inlet structures.
d) Weirs
1) General
Overflow weirs shall be readily adjustable over the life of
the structure to correct for differential settlement of the
tank.
2) Location
Overflow weirs shall be located to optimize actual hydraulic
detention time, and minimize short circuiting.
3) Design Rates
Weir loadings shall not exceed 20,000 gallons per day per
lineal foot based on design peak hourly flows for plants
having design average flows of 1.0 mgd or less. Overflow
rates shall not exceed 30,000 gallons per day per lineal foot
based on design peak hourly flow for plants having design
average flow of greater than 1.0 mgd. Higher weir overflow
rates may be allowed for bypass settling tanks. If pumping
is required, weir loadings should be related to pump delivery
rates to avoid short circuiting. Refer to Section
370.410(c)(8).
4) Weir Troughs
Weir troughs shall be designed to prevent submergence at
maximum design flow, and to maintain a velocity of at least
one foot per second at one-half design average flow.
e) Submerged Surfaces
The tops of troughs, beams, and similar submerged construction
elements shall have a minimum slope of 1.4 vertical to 1
horizontal; the underside of such elements should have a slope of
1 to 1 to prevent the accumulation of scum and solids.
f) Unit Dewatering
Unit dewatering featuring shall conform to the provisions outlined
in Section 370.530. The bypass design should also provide for
redistribution of the plant flow to the remaining units.
g) Freeboard
Walls of settling tanks shall extend at least 6 inches above the
surrounding ground surface and shall provide not less than 12
inches freeboard. Additional freeboard or the use of wind screens
is recommended where larger settling tanks are subject to high
velocity wind currents that would cause tank surface waves and
inhibit effective scum removal.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.720 Sludge and Scum Removal>>
a) Scum Removal
Full surface mechanical scum collection and removal facilities,
including baffling, shall be provided for all settling tanks,
except for Imhoff tanks. The unusual characteristics of scum
which may adversely affect pumping, piping, sludge handling and
disposal, should be recognized in design. Provisions may be made
for the discharge of scum with the sludge; however, other special
provisions for disposal may be necessary. Refer to Section
370.710(g).
b) Sludge Removal
Mechanical sludge collection and withdrawal facilities shall be
designed to assure an effective and controlled rate of removal of
the sludge. Suction withdrawal is encouraged.
1) Sludge Hopper
The minimum slope of the side walls shall be 1.7 vertical to
1 horizontal. Hopper wall surfaces should be made smooth
with rounded corners to aid in sludge removal. Hopper
bottoms shall have a maximum dimension of 2 feet. Extra
depth sludge hoppers for sludge thickening are not
acceptable.
2) Cross-Collectors
Cross-collectors serving one or more settling tanks may be
useful in place of multiple sludge hoppers.
3) Sludge Removal Piping
Each hopper shall have an individually valved sludge
withdrawal line at least 6 inches in diameter. The static
head available for withdrawal of sludge shall be 30 inches or
greater, as necessary to maintain a 3 feet per second
velocity in the withdrawal pipe. Clearance between the end
of the withdrawal line and the hopper walls shall be
sufficient to prevent "bridging" of the sludge. Adequate
provisions shall be made for rodding or back-flushing
individual pipe runs. Piping shall also be provided to
return waste sludge from secondary and tertiary processes to
primary clarifiers where they are used. Refer to Section
370.820.
4) Sludge Removal Control
Sludge wells equipped with telescoping valves or swing pipes
are recommended for primary sludge and fixed film sludges
where periodic withdrawal is proposed. Air lift type of
sludge removal will not be approved for removal of primary
sludges.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.730 Protection and Service Facilities>>
a) Operator Protection
All settling tanks shall be equipped to enhance safety for
operators. Such features shall appropriately include machinery
covers, life lines, stairways, walkways, handrails and
slip-resistant surfaces. If sidewalls are extended more than
three feet above the liquid level or four feet above ground level,
convenient walkways must be provided to facilitate housekeeping
and maintenance.
b) Mechanical Maintenance Access
The design shall provide for convenient and safe access to routine
maintenance items such as gear boxes, scum removal mechanisms,
baffles, weirs, inlet stilling baffle area, and effluent channels.
c) Electrical Fixtures and Controls
Electrical fixtures and controls in enclosed settling basins shall
meet the requirements of the National Electric Code for Class I,
Group D, Division 1 locations. The fixtures and controls shall be
located so as to provide convenient and safe access for operation
and maintenance. Adequate area lighting shall be provided.
<BSection 370.740 Imhoff Tanks>>
a) General
Imhoff tanks may be used for the sedimentation of settleable
solids and for the unheated anaerobic digestion of these solids.
b) Settling Compartment Design
1) Settling Rate
Surface settling rate shall not exceed 1000 gallons per day
per square foot based upon design peak hourly flow.
2) Detention Period
A detention period of not less than 1 hour based upon design
peak hourly flow shall be provided.
3) Dimensions
The minimum length of flow between inlet and outlet should be
10 feet and at least 6 feet of settling depth should be
provided.
4) Freeboard
The freeboard shall be 18 inches or more.
5) Hopper Slope
The bottom of the settling chamber of the conventional tank
shall have a slope of at least 1.4 vertical to 1.0
horizontal. The slot at the bottom of the settling chamber
allowing solids passage shall have a minimum opening and a
minimum overlap of 6 inches.
6) Inlets and Outlets
Inlet and outlet arrangements should be designed so that the
direction of flow may be reversed to allow for a more even
distribution of solids in the digestion compartment.
Adequate scum baffles shall be provided at the ends of the
flow-through chamber.
7) Weirs
Weir design and overflow rates shall be in accordance with
Section 370.710(d).
8) Walkway
A walkway along the length of the tank shall be provided.
c) Sludge Digestion Compartment Design
1) Digestion Chamber Capacity
The digestion chamber shall provide 4 cubic feet of volume
per capita for primary treatment and should provide 6 cubic
feet of volume per capita if secondary process sludge is also
to be digested. The capacity shall be measured below a
horizontal plane 18 inches below the settling chamber slot.
2) Vent Area
A surface area equal to 20% of the total tank surface area
shall be provided for venting the digestion compartment.
3) Hopper Slope
The bottom of the digestion chamber should be a hopper type
structure with minimum side slopes of 1.75 vertical to 1.0
horizontal. Sludge draw-off from the digestion chamber is
usually accomplished by utilizing the hydrostatic head with a
minimum differential of 6 feet being required. Eight inch
diameter sludge draw-off piping or larger shall be used.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.750 Septic Tank - Tile System>>
a) General
Septic tank tile systems shall be used only for domestic or
similar organic waste, where soil conditions are suitable and
sewers tributary to treatment works are not available.
b) Design Standards
Specific design information is contained in the document titled
"Private Sewage Disposal Licensing Act & Code", which can be
obtained from:
State of Illinois
Department of Public Health
Springfield, Illinois 62706.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
SUBPART H: SLUDGE PROCESSING AND DISPOSAL
<BSection 370.800 General>>
Facilities for processing sludge shall be provided at all mechanical sewage
treatment plants. Handling equipment shall be capable of processing sludge
to a form suitable for ultimate disposal.
<BSection 370.810 Process Selection>>
The selection of sludge handling unit processes should be based upon at
least the following considerations:
a) Local land use.
b) System energy requirements.
c) Cost effectiveness of sludge thickening and dewatering.
d) Equipment complexity and staffing requirements.
e) Adverse effects of heavy metals and other sludge components upon
the unit processes.
f) Sludge digestion or stabilization requirements.
g) Side stream or return flow treatment requirements (e.g., digester
or sludge storage facilities supernatant, dewatering unit
filtrate, wet oxidation return flows).
h) Sludge storage requirements.
i) Methods of ultimate disposal.
j) Back-up techniques of sludge handling and disposal.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.820 Sludge Thickening>>
a) Sludge thickeners to reduce the volume of sludge should be
considered. The design of thickeners (gravity tank, gravity
belt, dissolved-air flotation, centrifuge, and others) should take
into account the type and concentration of sludge, the sludge
stabilization processes, storage requirements, the method of
ultimate sludge disposal, chemical needs, and the cost of
operation. The use of gravity thickening tanks for unstabilized
sludges is not recommended because of problems due to septicity
unless provisions are made for adequate control of process
operational problems as well as problems of odors at the gravity
thickener and any following unit processes. Particular attention
should be given to the pumping and piping of the concentrated
sludge and possible onset of anaerobic conditions.
b) Process selection and unit process design parameters should be
based on prototype studies. The Agency will require such studies
where the sizing of other plant units is dependent on performance
of the thickeners. Refer to Section 370.520(b) for any new
process determination.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.830 Anaerobic Sludge Digestion>>
a) General
1) Multiple Units
Multiple units or alternate methods of sludge processing
shall be provided. Facilities for sludge storage and
supernatant separation in an additional unit may be required,
depending on raw sludge concentration and disposal methods
for sludge and supernatant.
2) Depth
If process design provides for supernatant withdrawal, the
proportion of depth to diameter should be such as to allow
for the formation of a reasonable depth of supernatant
liquor. A minimum side water depth of 20 feet is
recommended.
3) Design Maintenance Provisions
To facilitate emptying, cleaning, and maintenance the
following features are desirable:
A) Slope
The tank bottom shall slope to drain toward the
withdrawal pipe. For tanks equipped with a suction
mechanism for sludge withdrawal, a bottom slope not less
than 1 to 12 is recommended. Where the sludge is to be
removed by gravity alone, 1 to 4 slope is recommended.
B) Access Manholes
At least 2 access manholes should be provided in the top
of the tank in addition to the gas dome. There should
be stairways to reach the access manholes. A separate
side wall manhole shall be provided that is large enough
to permit the use of mechanical equipment to remove grit
and sand. The side wall access manhole should be low
enough to facilitate heavy equipment handling and may be
buried in the earthen bank insulation.
C) Safety
Non-sparking tools, rubber-soled shoes, safety harness,
gas detectors for inflammable and toxic gases, and at
least two self-contained breathing units shall be
provided for emergency use.
4) Toxic Materials
If the anaerobic digestion process is proposed, the basis of
design shall be supported by wastewater analyses to determine
the presence of undesirable materials, such as high
concentrations of sulfates and inhibitory concentrations of
heavy metals.
b) Sludge Inlets and Outlets, Recirculation and High Level Overflows
1) Multiple sludge inlets and draw-offs and, where used,
multiple recirculation suction and discharge points to
facilitate flexible operation and effective mixing of the
digester contents shall be provided unless adequate mixing
facilities are provided within the digester.
2) One inlet should discharge above the liquid level and be
located at approximately the center of the tank to assist in
scum breakup. The second inlet should be opposite to the
suction line at approximately the 2/3 diameter point across
the digester.
3) Raw sludge inlet discharge points should be so located as to
minimize short circuiting to the digested sludge or
supernatant draw-offs.
4) Sludge withdrawal to disposal should be from the bottom of
the tank. The bottom withdrawal pipe should be
interconnected with the necessary valving to the
recirculation pipe, to increase versatility in mixing the
tank contents.
5) An unvalved vented overflow shall be provided to prevent
damage to the digestion tank and cover in case of accidental
overfilling. This emergency overflow shall be piped to a
point and at a rate in the treatment process or sidestream
treatment facilities so as to minimize the impact on process
units.
c) Tank Capacity
1) Rational Design
The total digestion tank capacity shall be determined by
rational calculations based upon such factors as volume of
sludge added, its percent solids, and character, the
temperature to be maintained in the digesters, the degree or
extent of mixing to be obtained, the degree of volatile
solids reduction required, method of sludge disposal, and the
size of the installation with appropriate allowances for gas,
scum, supernatant and digested sludge storage. Secondary
digesters of two-stage series digestion systems that are used
for digested sludge storage and concentration shall not be
credited in the calculations for volumes required for sludge
digestion. Calculations should be submitted to justify the
basis of design.
2) Empirical Design
When such calculations are not submitted to justify the
design based on the above factors, the minimum combined
digestion tank capacity outlined below will be required.
Such requirements assume that the raw sludge is derived from
ordinary domestic wastewater, a digestion temperature is to
be maintained in the range of 85 to 95 F (29 to 35 C), 40
to 50 percent volatile matter in the digested sludge, and
that the digested sludge will be removed frequently from the
process. (See also subsection (a)(1) above and Section
370.860(a)(1).)
A) Completely Mixed Systems
For digestion systems providing for intimate and
effective mixing of the digester contents, the system
may be loaded up to 80 pounds of volatile solids per
1000 cubic feet of volume per day in the active
digestion units.
B) Moderately Mixed Systems
For digestion systems where mixing is accomplished only
by circulating sludge through an external heat
exchanger, the system may be loaded up to 40 pounds of
volatile solids per 1000 cubic feet of volume per day in
the active digestion units. This loading may be
modified upward or downward depending upon the degree of
mixing provided.
C) Digester Mixing
Facilities for mixing the digester contents shall be
provided where required for proper digestion by reason
of loading rates or other features of the system. Where
sludge recirculation pumps are used for mixing, they
shall be provided in accordance with the applicable
requirements of Section 370.850(a).
d) Gas Collection, Piping, and Appurtenances
1) General
All portions of the gas system including the space above the
tank liquor, storage facilities and piping shall be so
designed that under all normal operating conditions,
including sludge withdrawal, the gas will be maintained under
pressure. All enclosed areas where any gas leakage might
occur shall be adequately ventilated.
2) Safety Equipment
All necessary safety facilities shall be included where gas
is produced. Pressure and vacuum relief valves and flame
traps together with automatic safety shut off valves shall be
provided and protected from freezing. Water seal equipment
shall not be installed. Safety equipment and gas compressors
should be housed in a separate room with an exterior door.
3) Gas Piping and Condensate
Gas piping shall have a minimum diameter of 4 inches, except
that a smaller diameter pipe may be used at the gas
production meter. Gas piping shall slope to condensation
traps at low points. The use of float-controlled condensate
traps is not permitted. Condensation traps shall be
protected from freezing. Tightly fitted self-closing doors
should be provided at connecting passageways and tunnels
which connect digestion facilities to other facilities to
minimize the spread of gas. Piping galleries shall be
ventilated in accordance with subsection (d)(7).
4) Gas Utilization Equipment
Gas burning boilers, engines, etc., shall be located in well
ventilated rooms. Such rooms would not ordinarily be
classified as a hazardous location if isolated from the
digestion gallery or ventilated in accordance with subsection
(d)(7). Gas lines to these units shall be provided with
suitable flame traps.
5) Electrical Fixtures
Electrical fixtures and controls, in places enclosing
anaerobic digestion appurtenances, where hazardous gases are
normally contained in the tanks and piping, shall comply with
the National Electric Code for Class 1, Group D, Division 2
locations. Refer to subsection (d)(7).
6) Waste Gas
A) Waste gas burners shall be readily accessible and should
be located at least 50 feet away from any plant
structure if placed at ground level, or may be located
on the roof of the control building if sufficiently
removed from the tank. Waste gas burners shall be of
sufficient height to prevent injury to personnel due to
wind or downdraft conditions.
B) All waste gas burners shall be equipped with automatic
ignition such as a pilot light or a device using a
photoelectric cell sensor. Consideration should be
given to the use of natural or propane gas to insure
reliability of the pilot.
C) Gas piping shall be sloped at a minimum of 2 percent up
to the waste gas burner with a condensate trap provided
in a location not subject to freezing.
7) Ventilation
Any underground enclosures connecting with digestion tanks or
containing sludge or gas piping or equipment shall be
provided with forced ventilation in accordance with Section
370.410(g)(1-4) and (6).
8) Meter
A gas meter with bypass shall be provided to meter total gas
production for each active digestion unit. Total gas
production for two-stage digestion systems operated in series
may be measured by a single gas meter with proper
interconnected gas piping. Where multiple primary digestion
units are used with a single secondary digestion unit, a gas
meter shall be provided for each primary digestion unit. The
secondary digestion unit may be interconnected with the gas
measurement unit of one of the primary units. Interconnected
gas piping shall be properly valved with gastight gate valves
to allow measurement of gas production from, or maintenance
of, either digestion unit. Gas meters may be of the orifice
plate, turbine or vortex type. Positive displacement meters
are not recommended. The meter used must be specifically
designed for contact with corrosive and dirty gases.
e) Digestion Tank Heating
1) Insulation
Wherever possible digestion tanks should be constructed above
ground-water level and shall be suitably insulated to
minimize heat loss. Maximum utilization of earthen bank
insulation should be used.
2) Heating Facilities
Sludge may be heated by circulating the sludge through
external heaters or by units located inside the digestion
tank. Refer to subsection (e)(2)(B).
A) External Heating
Piping shall be designed to provide for the preheating
of feed sludge before introduction into the digesters.
Provisions shall be made in the lay-out of the piping
and valving to facilitate heater exchanger tube removal
and cleaning of the lines. Heat exchanger sludge piping
should be sized for peak heat transfer requirements.
Heat exchangers should have a heating capacity of 130
percent of the calculated peak heating requirement to
account for sludge tube fouling.
B) Other Heating Methods
i) The use of hot water heating coils affixed to the
walls of the digester, or other types of internal
heating equipment that require emptying the
digester contents for repair, are not acceptable.
ii) Other systems and devices have been developed
recently to provide both mixing and heating of
anaerobic digester contents. These systems will be
reviewed on their own merits. Operating data
detailing their reliability, operation and
maintenance characteristics will be required.
3) Heating Capacity
A) Sufficient heating capacity shall be provided to
consistently maintain the design sludge temperature
considering the insulation provided and ambient cold
weather conditions. Where digestion tank gas is used
for other purposes, an auxiliary fuel may be required.
B) The provision of standby heating capacity or the use of
multiple units sized to provide the heating requirements
shall be considered unless acceptable alternative means
of handling raw sludge are provided.
4) Hot Water Internal Heating Controls
A) Mixing Valves
A suitable automatic mixing valve shall be provided to
temper the boiler water with return water so that the
inlet water to the removable heat jacket or coil in the
digester can be held below a temperature at which caking
will be accentuated. Manual control should also be
provided by suitable bypass valves.
B) Boiler Controls
The boiler should be provided with suitable automatic
controls to maintain the boiler temperature at
approximately 180 F (82 C) to minimize corrosion and
to shut off the main gas supply in the event of pilot
burner or electrical failure, low boiler water level,
low gas pressure, excessive boiler water temperature or
pressure.
C) Boiler Water Pumps
Boiler water pumps shall be sealed and sized to meet the
operating conditions of temperature, operating head and
flow rate. Duplicate units shall be provided.
D) Thermometers
Thermometers shall be provided to show inlet and outlet
temperatures of the sludge, hot water feed, hot water
return and boiler water.
E) Water Supply
The chemical quality of the water supply shall be
suitable for use as boiler water. Refer to Section
370.550(b) for additional water supply considerations.
5) External Heater Operating Controls
All controls necessary to insure effective and safe operation
are required. Provision for duplicate units in critical
elements should be considered.
f) Supernatant Withdrawal
Where supernatant separation is to be used to concentrate sludge
in the digester units and increase digester solids retention time,
the design shall provide for ease of operation and positive
control of supernatant quality.
1) Piping Size
Supernatant piping should not be less than 6 inches in
diameter.
2) Withdrawal Arrangements
A) Withdrawal Levels
Piping should be arranged so that withdrawal can be made
from 3 or more levels in the tank. An unvalved vented
overflow shall be provided. The emergency overflow
shall be piped to a point and at a rate in the treatment
process or sidestream treatment facilities so as to
minimize the impact on process units.
B) Withdrawal Selection
On fixed cover tanks the supernatant withdrawal level
should preferably be selected by means of
interchangeable extensions at the discharge end of the
piping.
C) Supernatant Selector
A fixed screen supernatant selector or similar device
may only be used in an unmixed secondary digestion unit.
If such a supernatant selector is provided, provisions
shall be made for at least one other draw-off level
located in the supernatant zone of the tank, in addition
to the unvalved emergency supernatant draw-off pipe.
High pressure back-wash facilities shall be provided.
3) Sampling
Provision shall be made for sampling at each supernatant
draw-off level. Sampling pipes should be at least 1 1/2
inches in diameter and should terminate at a suitably sized
sampling sink or basin.
4) Supernatant Disposal
Supernatant return and disposal facilities shall be designed
to prevent adverse hydraulic and organic effects on plant
operations. If nutrient removal (e.g., phosphorus, ammonia)
must be accomplished at a plant, then a separate supernatant
side stream treatment system should be considered.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.840 Aerobic Sludge Digestion>>
a) General
The aerobic sludge digestion system shall include provisions for
digestion, supernatant separation, sludge concentration and any
necessary sludge storage. These may be accomplished with separate
tanks or processes or in digestion tanks.
b) Multiple Units
Multiple digestion units capable of independent operation are
recommended for all plants and shall be provided in those plants
where the design average flow exceeds 100,000 gallons per day.
Plants without multiple units shall provide alternate sludge
handling and disposal methods.
c) Tank Capacity
1) The following digestion tank capacities are based on a solids
concentration of 2 percent with supernatant separation
performed in a separate tank. If supernatant separation is
performed in the digestion tank, a minimum of 25 percent
additional volume is required. These capacities shall be
provided unless sludge thickening facilities (refer to
Section 370.820) are utilized to thicken the feed solids
concentration to greater than 2 percent. If such. thickening
is provided, the digestion volumes may be decreased
proportionally.
Volume (ft.(3)/Population
<PSludge Source>> <PEquivalent (P.E.))>>
Waste activated sludge-no
primary settling 4.5*
Primary plus waste activated
sludge 4.0*
Waste activated sludge
exclusive of primary sludge 2.0*
Extended aeration activated
sludge 3.0
Primary plus fixed film
reactor sludges 3.0
*These volumes apply to waste activated sludge from single stage
nitrification facilities with less than 24 hours detention time
based on design average flow.
2) These volumes are based on digester temperatures of 59 F
(15 C) and a solids retention time of 27 days. Aerobic
digesters shall be covered to minimize heat loss or these
volumes shall be increased for colder temperature
applications. Refer to subsection (g) below for necessary
sludge storage. Additional volume may be required if the
land application disposal method is used in order to meet
applicable Federal regulations.
d) Mixing
Aerobic digesters shall be equipped with devices which can
maintain solids in suspension and which provide complete mixing of
the digester contents.
e) Air Requirements
Sufficient air shall be provided to keep the solids in suspension
and maintain dissolved oxygen between 1 and 2 milligrams per liter
(mg/l). For minimum mixing and oxygen requirements, an air supply
of 30 cfm per 1000 cubic feet of tank volume shall be provided
with the largest blower out of service. If diffusers are used,
the nonclog type is recommended, and they should be designed to
permit continuity of service. If mechanical turbine aerators are
utilized, at least two turbine aerators per tank shall be provided
to permit continuity of service. Mechanical aerators are not
acceptable for use in aerobic digesters due to freezing
conditions experienced throughout Illinois.
f) Supernatant Separation and Scum and Grease Removal
1) Supernatant Separation
Facilities shall be provided for effective separation or
decanting of supernatant. Separate facilities are
recommended; however, supernatant separation may be
accomplished in the digestion tank if additional volume is
provided, in accordance with subsection (c) above. The
supernatant drawoff unit shall be designed to prevent the
recycle of scum and grease back to plant process units.
Provision should be made to withdraw supernatant from
multiple levels of the supernatant withdrawl zone.
2) Scum and Grease Removal
Facilities shall be provided for the effective collection of
scum and grease for final disposal and to prevent recycle
back to plant process units and prevent long term
accumulation and potential for discharge of scum and grease
in the effluent.
g) High Level Emergency Overflow
An unvalved high level overflow and any necessary piping shall be
provided to return digester overflow back to the head of the plant
or to the aeration process in case of accidental overfilling. The
design of the overflow shall take into account the length of time
and rate at which sludge is wasted during periods when the
treatment plant is unattended, potential effects of overflow on
plant process units, location of the discharge from the emergency
overflow, and the potential for discharge of suspended solids in
the plant effluent.
h) Digested Sludge Storage Volume
1) Sludge storage must be provided in accordance with Section
370.870 to accommodate daily sludge production volumes and
as an operational buffer for unit outage and adverse weather
conditions. Designs utilizing increased sludge age in the
activated sludge system as a means of storage are not
acceptable.
2) Liquid sludge storage capacity shall be based on the
following values unless digested sludge thickening facilities
are utilized (refer to Section 370.173) to provide solids
concentrations to greater than 2 percent.
<PSludge Source>> <PVolume (ft.(3)/P.E./day)>>
Waste activated sludge-no
primary settling, primary
plus waste activated sludge,
and extended aeration
activated sludge 0.13
Waste activated sludge
exclusive of primary sludge 0.06
Primary plus fixed film
reactor sludged 0.10
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.845 High pH Stabilization>>
a) General
Alkaline material may be added to liquid primary or secondary
sludges for sludge stabilization in lieu of digestion facilities,
to supplement existing digestion facilities, or for interim sludge
handling. Inasmuch as the high pH stabilization process does not
reduce organic matter but rather increases the mass of dry sludge
solids, so that additional volumes of sludge will be generated in
the absence of supplemental dewatering, the design shall account
for the increased sludge quantities for storage and handling,
transportation and disposal methods and associated costs.
Alkaline material may be added to dewatered sludges for
stabilization pursuant to Section 370.520(b).
b) Operational Criteria
Sufficient alkaline material shall be added to liquid sludge in
order to produce a homogeneous mixture with a minimum pH of 12
after 2 hours of vigorous mixing. Facilities for adding
supplemental alkaline material shall be provided to maintain the
pH of the sludge during interim sludge storage periods.
c) Odor Control and Ventilation
Odor control facilities shall be provided for sludge mixing and
treated sludge storage tanks that are located within 1/2 mile of
residential or commercial areas. Indoor sludge mixing, storage
and processing facilities shall have ventilation that meets the
ventilation requirements contained in Section 370.410(g)(1-4) and
(6) and shall comply with the safety precautions contained in
Section 370.560. Adequate facilities shall be provided to
condition the exhaust air to meet the applicable substantive and
permitting requirements of 35 Ill. Adm. Code Subtitle B: Air
Pollution.
d) Mixing Tanks and Equipment
1) Tanks
Mixing tanks may be designed to operate as either a batch or
continuous flow process. A minimum of two tanks of adequate
size to provide a minimum of 2 hours of contact time in each
tank shall be provided. The following factors shall also be
taken into account in determining the number and size of
tanks:
A) Peak sludge flow rates;
B) Storage between batches;
C) Dewatering or thickening performed in tanks;
D) Repeating sludge treatment due to pH decay of stored
sludge;
E) Sludge thickening prior to sludge treatment;
F) Type of mixing device used and associated maintenance
and repair requirements.
2) Equipment
Mixing equipment shall be designed to provide vigorous
agitation within the mixing tank, to maintain solids in
suspension and to provide for a homogenous mixture of the
sludge solids and alkaline material. Mixing may be
accomplished by either diffused aeration or mechanical
mixing. For diffused aeration, an air supply of 30 cfm per
1000 cubic feet of mixing tank volume with the largest blower
out of service shall be provided. Nonclogging diffusers
designed to permit continuity of service should be used.
Mechanical mixers shall be designed to assure continuity of
service during freezing weather conditions and shall be
equipped with impellers designed to minimize fouling from
debris in the sludge.
e) Chemical Feed and Storage Equipment
1) General
Equipment used for handling or storing alkaline shall be
designed to provide operator protection from eye and tissue
damage. Refer to Section 370.560 for proper safety
precautions. Material storage, slaking and feed equipment
shall be sealed as airtight as practicable to prevent contact
of alkaline material with atmospheric carbon dioxide and
water vapor and to prevent the escape of dust material. All
equipment and associated transfer lines and piping shall be
accessible for cleaning.
2) Feed and Slaking Equipment
The design of the feeding equipment shall be determined by
the treatment plant size, type of alkaline material used,
slaking required and operator requirements. Automated or
batch equipment may be used. Automated feeders may be
volumetric or gravimetric, based on accuracy, reliability and
maintenance requirements. Manually operated batch slaking of
quicklime (CaO) should be avoided unless protective clothing
and equipment are provided. At small plants, for safety
reasons the use of hydrated lime (Ca(OH)[2]) over quicklime
is recommended. Feed and slaking equipment shall be sized to
handle a minimum of 150% of the peak sludge flow rate,
including sludge that may need to be retreated due to pH
decay. Duplicate units shall be provided.
3) Chemical Storage Facilities
Alkaline materials may be received in either bag or bulk
form. Materials delivered in bags must be stored indoors and
elevated above floor level. Bags should be multi-walled and
moisture-proof. Dry bulk storage containers must be as
airtight as practicable and shall contain a mechanical
agitation mechanism. Storage facilities shall be sized to
provide a minimum 30-day supply of alkaline materials.
Adequate provisions shall be made to meet the applicable
substantive and permitting requirements of 35 Ill. Adm. Code
Subtitle B: Air Pollution.
f) Sludge Storage
Refer to Section 370.870 for general design considerations for
sludge storage facilities. The design shall incorporate the
following considerations for the storage of high pH stabilized
sludge:
1) Liquid Sludge
Liquid high pH stabilized sludge shall be stored in a tank or
vessel equipped with rapid sludge withdrawl mechanisms for
sludge disposal or retreatment and may not be stored in a
lagoon. Provision shall be made for adding alkaline material
in the storage tank. Mixing equipment meeting the
requirements of subsection (d)(2) above shall be provided in
all storage tanks.
2) Dewatered Sludge
On-site storage of dewatered high pH stabilized sludge shall
be limited to 30 days. Provisions shall be made for rapid
retreatment or disposal of dewatered sludge stored on site in
case of sludge pH decay.
3) Off-Site Storage
There shall be no off-site storage of high pH stabilized
sludge unless the Agency has issued a permit for off-site
storage.
g) Disposal
Methods and options for immediate sludge disposal should be used
in order to reduce the on-site sludge inventory and the amount of
sludge that must be retreated to reduce odors when sludge pH decay
occurs. Where land application is used, the sludge must be
incorporated into the soil within 24 hours after application.
(Source: Added at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.850 Sludge Pumps and Piping>>
a) Sludge Pumps
1) Capacity
Pump capacities shall be adequate but not excessive.
Provision for varying pump capacity is desirable. A rational
basis of design shall be provided with the plan documents.
2) Duplicate Units
Duplicate units shall be provided at all installations.
3) Type
Plunger pumps, screw feed pumps or other types of pumps with
demonstrated solids handling capability shall be provided for
handling raw sludge. Where centrifugal pumps are used, a
parallel positive displacement pump shall be provided as an
alternate to pump heavy sludge concentrations, such as
primary or thickened sludges, that may exceed the pumping
head of the centrifugal pump.
4) Minimum Head
A minimum positive head of 24 inches shall be provided at the
suction side of centrifugal type pumps and is desirable for
all types of sludge pumps. Maximum suction lifts should not
exceed 10 feet for plunger pumps.
5) Sampling Facilities
Unless sludge sampling facilities are otherwise provided,
quick closing sampling valves shall be installed at the
sludge pumps. The size of valve and piping should be at
least 1 1/2 inches and terminate at a suitably sized sampling
sink or floor drain.
b) Sludge Piping
1) Size and Head
Digested sludge withdrawal piping should have a minimum
diameter of 8 inches for gravity withdrawal and 6 inches for
pump suction and discharge lines. Where withdrawal is by
gravity, the available head on the discharge pipe should be
at least 4 feet and preferably more. Undigested sludge
withdrawl piping shall be sized in accordance with Section
370.720(b)(3).
2) Slope and Flushing Requirements
Gravity piping should be laid on uniform grade and alignment.
Slope on gravity discharge piping should not be less than 3
percent for primary sludges and all sludges thickened to
greater than 2 percent solids. The slope on gravity
discharge piping should not be less than 2 percent for
aerobicly digested sludge or waste activated sludge with less
than 2 percent solids. Cleanouts shall be provided for all
gravity sludge piping. Provisions shall be made for draining
and flushing discharge lines. All sludge pipe shall be
suitably located or otherwise adequately protected to prevent
freezing.
3) Supports
Special consideration shall be given to the corrosion
resistance and permanence of supporting systems for piping
located inside the digestion tank.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.860 Sludge Dewatering>>
a) General
On-site sludge dewatering facilities shall be provided for all
plants, although the following requirements may be reduced or
omitted, if justified, with on-site liquid sludge storage
facilities or approved off-site sludge disposal.
1) Anaerobic Digestion Sludge Production
For purposes of calculating sludge handling and disposal
needs, sludge production values from a two-stage anaerobic
digestion process shall be based on a maximum solids
concentration of 5% without additional thickening. The
solids production values, calculated on a dry weight basis,
shall be based on the following values for the listed
processes:
A) Primary plus waste activated sludge--at least 0.12
lbs/P.E./day;
B) Primary plus fixed film reactor sludge--at least 0.09
lbs/P.E./day.
2) Aerobic Digestion Sludge Production
For purposes of calculating sludge handling and disposal
needs, sludge production values from an aerobic digester
shall be based on a maximum solids concentration of 2%
without additional thickening. The solids production
values, calculated on a dry weight basis, shall be based on
the following values for the listed processes:
A) Primary plus waste activated sludge--at least 0.16
lbs/P.E./day;
B) Primary plus fixed film reactor sludge--at least 0.12
lbs/P.E./day.
3) Production from Other Sludge Treatment Processes
For purposes of calculating sludge handling and disposal
needs, sludge production values from other sludge treatment
processes shall be determined by rational calculations in the
basis of design. Refer to Section 370.520(b) for any new
process determinations.
b) Sludge Drying Beds
1) Applicability
Sludge drying beds may be used for dewatering well digested
sludge from either the anaerobic or aerobic process. Due to
the large volume of sludge produced by the aerobic digestion
process, consideration should be given to using a combination
of dewatering systems or other means of ultimate sludge
disposal.
2) Unit Sizing
Sludge drying bed area shall be calculated on a rational
basis with the following items taken into account:
A) The volume of wet sludge produced by existing and
proposed processes.
B) Depth of wet sludge drawn to the drying beds. For
design calculations purposes a maximum depth of 8 inches
shall be utilized. For operational purposes, the depth
of sludge placed on the drying bed may vary from the
design depth based on the solids content and the type of
digestion used.
C) Total digester volume and other wet sludge storage
facilities.
D) Degree of sludge thickening provided after digestion.
E) The maximum drawing depth of sludge which can be removed
from the digester or other sludge storage facilities
without causing process or structural problems.
F) The time required on the bed to produce a removable
cake. Adequate provision shall be made for sludge
dewatering and/or sludge disposal facilities for those
periods of time during which outside drying of sludge on
beds is hindered by weather. For Illinois that season
is considered to extend from early November through at
least April.
G) Capacities of auxiliary dewatering facilities.
3) Percolation Type Bed Components
A) Gravel
The lower course of gravel around the underdrains should
be properly graded and should be 12 inches in depth,
extending at least 6 inches above the top of the
underdrains. It is desirable to place this in 2 or more
layers. The top layer of at least 3 inches should
consist of gravel 1/8 inch to 1/4 inch in size.
B) Sand
The top course should consist of at least 6 to 9 inches
of clean, washed, coarse sand. The effective size of
the sand should be in the range of 0.8 to 1.5
millimeters. The finished sand surface should be level.
C) Underdrains
Underdrains should be at least 4 inches in diameter laid
with open joints. Perforated pipe may also be used.
Underdrains should be spaced not more than 20 feet
apart. Various pipe materials may be used, so long as
they are sufficiently strong and are corrosion
resistant.
D) Additional Dewatering Provisions
Consideration shall be given to providing a means of
decanting the supernatant of sludge placed on the sludge
drying beds. More effective decanting of supernatant
may be accomplished with polymer treatment of the
sludge.
4) Walls
Walls should be water-tight and extend 18 inches above and at
least 6 inches below the surface of the bed. Outer walls
should be curbed or extended at least 4 inches above the
outside grade elevation to prevent soil from washing on to
the beds.
5) Sludge Removal
Each bed shall be constructed so as to be readily and
completely accessible to mechanical cleaning equipment.
Concrete runways spaced to accommodate mechanical equipment
shall be provided. Special attention should be given to
assure adequate access to the areas adjacent to the
sidewalls. Entrance ramps down to the level of the sand bed
shall be provided. These ramps shall be high enough to
eliminate the need for an entrance end wall for the sludge
bed.
c) Sludge Lagoons for Dewatering
1) General
Lagoons as a means of dewatering digested sludge will be
permitted only upon proof that the character of the digested
sludge and the design mode of operation are such that
offensive odors will not result. Where sludge lagoons are
permitted, adequate provisions shall be made for other sludge
dewatering facilities or sludge disposal in the event of
upset or failure of the sludge digestion process.
2) Location
Sludge lagoons shall be located as far as practicable from
inhabited areas or areas likely to be inhabited during the
lifetime of the structures.
3) Seal
Adequate provisions shall be made to seal the lagoon bottoms
and embankments to prevent leaching into adjacent soils or
groundwater. Refer to Section 370.930(d)(1)(A), (d)(2)(C)
and (d)(2)(D).
4) Access
Provisions shall be made for sludge pumping or heavy
equipment access for sludge removal from the lagoon.
d) Mechanical Dewatering Facilities
1) General
Provision shall be made to maintain sufficient continuity of
service so that sludge may be dewatered without accumulation
beyond storage capacity. The number of vacuum filters,
centrifuges, filter presses, belt filters, or other
mechanical dewatering facilities should be sufficient to
dewater the sludge produced with the largest unit out of
service. Unless other standby wet sludge facilities are
available, adequate storage facilities of at least 4 days
production volume shall be provided. Documentation must be
submitted justifying the basis of design of mechanical
dewatering facilities.
2) Water Supply Protection
The water supply for mechanical dewatering facilities shall
meet the requirements of Section 370.550(b).
3) Auxiliary Facilities for Vacuum Filters
Back-up vacuum and filtrate pumps shall be provided. It is
permissible to have uninstalled back-up vacuum and filtrate
pumps for every three or less vacuum filters, provided that
the installed units can easily be removed and replaced. At
least one filter media replacement unit shall be provided.
4) Ventilation
Adequate facilities shall be provided for ventilation of the
dewatering area. The exhaust air should be properly
conditioned to avoid odor nuisance. Ventilation shall be
provided in accordance with Section 370.410(g)(6).
5) Chemical Handling Enclosures
Lime-mixing facilities should be completely enclosed to
prevent the escape of lime dust. Chemical handling equipment
should be automated to eliminate the manual lifting
requirement. Refer to Section 370.560.
e) Drainage and Filtrate Disposal
Drainage from beds or filtrate dewatering units shall be returned
to the sewage treatment process at appropriate points and rates.
f) Other Dewatering Facilities
If it is proposed to dewater sludge by other methods, a detailed
description of the process and design data shall accompany the
plans. Refer to Section 370.520(b) for any new process
determinations.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.870 Sludge Storage and Disposal>>
a) Storage
1) General
Sludge storage facilities shall be provided at all mechanical
treatment plants, and may consist of any combination of
drying beds, lagoons, separate tanks, additional volume in
stabilization units, pad areas or other means to store either
liquid or dried sludge. Drainage of supernatant from sludge
storage facilities shall be returned to the sewage treatment
process at appropriate points and rates. Refer to Section
370.860(b) and (c) for drying bed and lagoon design criteria,
respectively.
2) Volume
Rational calculations justifying the number of days of
storage based on the total sludge handling and disposal
system shall be submitted. Refer to Sections 370.840(g) and
370.860(a) for anaerobicly and aerobicly digested sludge
production values; values for other stabilization processes
shall be justified on the basis of design. If land
application is the only means of sludge disposal used at a
treatment plant, a minimum of 150 days storage shall be
provided, in order to account for inclement weather and
cropping practices.
b) Disposal
1) Landfilling
Sludge and sludge residues may be disposed of in Agency
approved municipal solid waste landfill units under the terms
and conditions of permits issued by the Agency's Bureau of
Land. On-site landfilling shall be conducted in conformance
with the design recommendations of the Bureau of Land and
must be approved by the Agency's Bureau of Water.
2) Land Application
Specific design criteria for land application of sludge are
set out in Design Criteria for Sludge Application on Land, 35
Ill. Adm. Code 391. Additional operating criteria may be
obtained from applicable Federal regulations. In order to
assure compliance with the facility's effluent standards,
alternative sludge disposal options to account for inclement
weather and cropping practices are recommended.
3) Sludge Lagoons
The use of lagoons for ultimate disposal of sludge is not
recommended because of odor potential, area and volume
required and possible long term problems from groundwater
contamination. If a lagoon is proposed, a hydrogeologic
survey must be performed to demonstrate the appropriateness
of a disposal lagoon at the particular site. A groundwater
monitoring program must be included in any sludge lagoon
design. Refer to Section 370.860(c) for lagoon design
criteria.
4) Other Disposal Methods
A detailed description of the technique and design data shall
accompany the plans of any proposal to dispose of sludge by
methods other than those specified in this Section. Refer to
Section 370.520(b) for any new process determinations.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
SUBPART I: BIOLOGICAL TREATMENT
<BSection 370.900 Trickling Filters>>
a) General
1) Applicability
Trickling filters may be used for treatment of sewage
amenable to treatment by aerobic biologic processes.
Trickling filters shall be preceded by settling tanks
equipped with scum and grease collecting devices, or other
suitable pretreatment facilities.
2) Design Basis
Filters shall be designed so as to provide the required
reduction in biochemical oxygen demand, ammonia nitrogen, or
to properly condition the sewage for subsequent treatment
processes.
3) Multiple Units
Multiple trickling filter units capable of independent
operation are recommended for all plants and must be provided
for those plants where the design average flow exceeds
100,000 gallons per day. Plants not having multiple units
shall include other provisions to assure continuity of
treatment.
b) Dosing Equipment
1) Distribution
A) All hydraulic factors involving proper distribution of
sewage on the filter should be carefully calculated and
submitted with the basis of design.
B) The sewage may be distributed over the filter by rotary
distributors or other suitable devices which will permit
reasonably uniform distribution to the surface area. At
design average flow, the deviation from calculated
uniformly distributed volume per square foot of the
filter surface shall not exceed plus or minus 10
percent at any point.
2) Dosing and Recirculation
A) Sewage may be applied to the filters by siphons, pumps
or by gravity discharge from preceding treatment units
when suitable flow characteristics have been developed.
Application of the sewage should be continuous except
for low rate filters. A hydraulic system for
recirculation shall be provided for new facilities and
should be considered where existing trickling filter
units are included in treatment plant upgrading.
B) The piping system, including dosing equipment and
distributor, shall be designed to provide capacity for
the peak hourly flow rate including recirculation rates
determined under subsection (h).
3) Distributor Head Requirements
For reaction type distributors, a minimum head of 24 inches
between low water level in siphon chamber and center of arms
is required. Similar allowances shall be made in design for
added pumping head requirements where pumping to the reaction
type distributor is used. The design shall include the head
required at the center column for the full range of flows,
taking into account all head losses from the center column
back to the dosing facility at all water levels.
Calculations shall be submitted to justify the basis of
design.
4) Clearance
A minimum clearance of 6 inches between media and distributor
arms shall be provided. Refer to subsection (e)(4).
c) Media
1) Quality
The media may be crushed rock, slag or specially manufactured
material. The media shall be durable, resistant to spalling
or flaking, and be relatively insoluble in sewage. The top
18 inches shall have a loss by the 20-cycle, sodium sulfate
soundness test of not more than 10 percent, as prescribed by
ASCE Manual of Engineering Practice, Number 13, the balance
to pass a 10-cycle test using the same criteria. Slag media
shall be free from iron. Manufactured media shall be
resistant to ultraviolet degradation, disintegration,
erosion, aging, all common acid and alkalies, organic
compounds, and fungus and other biological attack. Such
media shall be structurally capable of supporting a man's
weight or a suitable access walkway shall be provided to
allow for distributor maintenance.
2) Depth
The filter media shall have a minimum depth of 6 feet above
the underdrains. For rock media filters (subsection
(c)(3)(A)), only the top 7 feet of the volume of the filter
shall be considered in BOD removal credit computations. For
manufactured media filters see subsection (c)(3)(B).
3) Size and Grading of Media
A) Rock, Slag and Similar Media
i) Rock, slag and similar media shall not contain more
than 5 percent by weight of pieces whose longest
dimension is 3 times the least dimension.
ii) Media shall be free from thin elongated and flat
pieces, dust, clay, sand, or fine material and
shall conform to the following size and grading
when mechanically graded over vibrating screen with
square openings:
Passing 4 1/2 inch screen - 100% by weight
Retained on 3 inch screen - 95-100% by weight
Passing 2 inch screen - 0-2% by weight
Passing 1 inch screen - 0-1% by weight
B) Manufactured Media
Suitability of size, space, media configuration and
depth will be evaluated on the basis of experience with
installations handling similar wastes and loadings. To
ensure sufficient void clearance, media with a specific
surface area of no more than 30 square feet per cubic
foot may be used for filters employed for carbonaceous
reduction, and media with a specific surface area of no
more than 45 square feet per cubic foot may be used for
second stage ammonia reduction. See subsection (c)(1)
for quality requirements.
4) Handling and Placing of Media
A) Material delivered to the filter site shall be stored on
wood planks or other approved clean hard surfaced areas.
B) All material shall be rehandled at the filter site and
no material shall be dumped directly into the filter.
Crushed rock, slag and similar media shall be rescreened
or forked at the filter site to remove all fines.
C) The material shall be placed by hand to a depth of 12
inches above the tile underdrains and all material shall
be carefully placed so as not to damage the underdrains.
The remainder of the material may be placed by means of
belt conveyors or equally effective methods approved by
the engineer.
D) Manufactured media shall be handled and placed as
recommended by the manufacturer and approved by the
engineer.
E) Trucks, tractors, or other heavy equipment shall not be
driven over the filter during or after construction.
d) Underdrainage System
1) Arrangement
Underdrains with semi-circular inverts or equivalent should
be provided and the underdrainage system shall cover the
entire floor of the filter. Inlet openings into the
underdrains shall have an unsubmerged gross combined area
equal to at least 15 percent of the surface area of the
filter.
2) Slope
The underdrains shall have a minimum slope of 1 percent.
Effluent channels shall be designed to produce a minimum
velocity of 2 feet per second at design average flow of
application to the filter and shall have adequate capacity
for the peak hourly flow rate including the required
recirculation flows.
3) Flushing
Provision should be made for flushing the underdrains. In
small filters, use of a peripheral head channel with vertical
vents is acceptable for flushing purposes. Inspection
facilities should be provided.
4) Ventilation Requirements for Underdrains
The underdrainage system, effluent channels, and effluent
pipe should be designed to permit free passage of air. The
size of drains, channels, and pipe should be such that not
more than 50 percent of their cross-sectional area will be
submerged under the design hydraulic loading. Consideration
should be given in the design of the effluent channels to the
possibility of increased hydraulic loading.
e) Special Features
1) Flooding
Provision shall be made in the design of conventional rock
filter structures so that the media may be flooded.
2) Maintenance
All distribution devices, underdrains, channels and pipes
shall be designed so that they may be properly maintained,
flushed or drained.
3) Flow Measurement
Devices shall be provided to permit measurement of flow to
the filter, and of recirculated flows.
4) Protection From Freezing
Trickling filters shall be covered to protect from freezing,
and to maintain operation and treatment efficiencies. The
filter cover shall be constructed of appropriate corrosion
resistant materials and designed to allow operator access for
maintenance, repair and replacement of the filter dosing
equipment.
5) Ventilation of Covered Filters
Forced ventilation shall be provided for covered trickling
filters to insure adequate oxygen for process requirements.
Windows or simple louvered mechanisms so arranged to insure
air distribution throughout the enclosure shall be provided.
The ventilation facilities shall be designed to allow
operator control of air flow in accordance with outside
temperature. Design computations showing the adequacy of air
flow to satisfy process oxygen requirements shall be
submitted.
f) Two-Stage Filters
The foregoing standards also apply to second stage filters.
g) Special Applications
1) Roughing Filters
In some instances it is desirable to partially reduce the
organic strength of wastewaters. In such cases trickling
filters may be used for roughing treatment. Design
parameters and contaminant removal efficiencies will be
approved on a case-by-case basis. Refer to subsections
(h)(2) and (h)(3).
2) Nitrifying Filters
Trickling filters may, under favorable conditions, be used as
nitrification devices. Design parameters and contaminant
removal efficiencies will be approved on a case-by-case
basis. Refer to Section 370.1210(d).
h) Efficiency
1) Single Stage, Settling Tank -- No Recirculation
Expected reduction of BOD of settled normal domestic
wastewater by a single stage filter, packed with crushed
rock, slag or similar material and with subsequent settling,
shall be determined from Appendix F, Figure No. 3. In
developing this curve, loading due to recirculated sewage
has not been considered.
2) Single or Multi-Stage, Settling Tank -- Recirculation
Expected BOD removal efficiencies may also be determined by
theoretical and empirical formula if accompanied by detailed
explanation, particularly for roughing filters and for
filters with recirculation. (Refer to WEF Manual of Practice
(MOP) No. 8, "Design of Municipal Wastewater Treatment
Plants", vol. 1 (1992).)
3) Single or Multi-Stage, No Settling Tank -- Recirculation
Filters not followed by a settling tank and discharging into
a subsequent treatment process shall not be credited with BOD
removal efficiencies as in subsections (h)(1) and (h)(2)
above. Expected performance in such cases, including filters
packed with manufactured media, shall be determined from
prototype testing and full-scale plant experience.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.910 Rotating Biological Contactors>> <B(Repealed)>>
(Source: Repealed at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.915 Rotating Biological Contactors>>
a) General
Wastewater treatment facilities that propose to use rotating
biological contactors (RBCs) shall submit to the Agency for review
field experience and operational data that demonstrates that
observed problems with the process have been solved at similar
full scale installations. The Agency will review the claimed
field experience against known field conditions and the
operational history of observed problems at similar facilities.
b) Mechanical Reliability and Structural Integrity
1) The mechanical and structural reliability of the shafts and
media subjected to cyclic stress reversals must be
demonstrated relative to the design life of the plant and the
known weight of the machines based on field experience.
2) The design must show that film thickness will be effectively
controlled throughout all parts of the media pack to prevent
excessive film weight and water pickup weight due to plugging
restrictions. The equipment design must include load cells
to warn of the need for film thickness control and to
demonstrate the effectiveness of the proposed film thickness
control practices.
c) Process Reliability
1) Process reliability must be demonstrated, including proven
operational control procedures relative to design organic
loadings for the unit media area or volume, which
satisfactorily insure that the applicable effluent standards
are met. The process design shall also include proven
operational control procedures that will prevent process
functional deficiencies and media plugging that cause the
weight to exceed shaft and media structural capabilities
during the design life of the plant.
2) The design must show that adequate void clearance (as
distinguished from void ratio) is provided to insure that the
biological film, including any grease and fats that may
accumulate, will not interefere with the flow of liquid and
air in the media pack. The Agency will compare the RBC
designs under review to past experience with designs used for
plastic trickling filter media to accomplish adequate void
clearance.
3) The design shall provide for maintaining a minimum of 2.0
mg/l dissolved oxygen in the basin liquor. The effectiveness
of the proposed method for maintaining adequate dissolved
oxygen will be evaluated based on field experience at similar
full scale installations.
4) If pilot testing is proposed, the size of the RBC pilot plant
unit and the scope and duration of the testing program on the
specific waste that will be treated must be thoroughly
documented. The proposed pilot testing program should be
submitted to the Agency for comment prior to the initiation
of testing. The RBC pilot units must be of prototype scale.
Because of differential seasonal weight and plugging field
problems, the test period must cover the four seasons, to
allow the Agency to evaluate the proposed design against the
experience of existing full scale plants.
5) The process design must include provisions for meeting
applicable effluent limits with some units out of service for
unit repair, biofilm thickness control, out-of-balance
correction and other operational problems. Added units for
standby credit will be required to insure compliance with
effluent limitations and to prevent mechanical or structural
failures during periods of unit outage for maintenance,
repair, or process control purposes.
(Source: Added at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.920 Activated Sludge>>
a) General
1) Applicability
A) Biodegradable Wastes
The activated sludge process, and its various
modifications, may be used to treat wastewater which is
amenable to biological treatment. Approval of new
activated sludge plants shall be limited to those plants
where the design average flow capacity exceeds 0.25 mgd.
B) Operation Control Requirements
The activated sludge process requires close attention
and competent operating supervision. Facilities and
appurtenances for routine control and control tests
shall be provided at all activated sludge plants.
These requirements shall be considered when proposing
this type of treatment.
C) Energy Requirements
This process requires major energy usage to meet
aeration demands. Energy costs and potential mandatory
emergency public power reduction events, in relation to
critical water quality conditions, must be carefully
evaluated. Capability of energy usage phasedown while
still maintaining process viability, both under normal
and emergency energy availability conditions, must be
included in the activated sludge design.
2) Specific Process Selection
The activated sludge process and its several modifications
may be employed to accomplish varied degrees of removal of
suspended solids and reduction of 5-day BOD and nitrogenous
oxygen demand. Choice of the process most applicable will be
influenced by the proposed plant size, type of waste to be
treated, treatability of waste, degree and consistency of
treatment required and local factors. All designs shall
provide for flexibility in operation. All plants shall be
designed to operate in at least two modes.
3) Winter Protection
Units shall be protected against freezing. Maximum
utilization of earthen bank insulation shall be considered.
4) Process Efficiency
The activated sludge process designed within the organic and
hydraulic loading limits of these standards, treating normal
domestic wastewaters unaffected by surge loadings, long term
peak flows, or industrial wastes, may be expected to meet an
effluent standard of 20 mg/l CBOD[5] or BOD[5] and 25 mg/l
suspended solids when computed on a 30-day monthly average
basis. Those installations which are anticipated to be
subject to surge loadings, long term peak flows or
industrial wastes shall have appropriate design
modifications in order to assure consistent effluent
quality.
b) Preliminary Treatment
Effective removal of grit, debris, excessive oil and grease and
screening of solids shall be accomplished prior to the activated
sludge process. Where primary settling does not precede the
activated sludge process, screening with 1/2 inch or smaller clear
opening is recommended in order to prevent plugging of return
sludge piping and pumps.
c) Primary Treatment Bypass
When primary settling is used, provision shall also be made for
discharging raw sewage directly to the aeration tanks following
preliminary treatment.
d) Process Organic Loadings
The aeration tank capacities and permissible loadings for the
several adaptations of the processes shown in the table shall be
used.
Permissible Organic Loading
For The Activated Sludge Processes
For Normal Domestic Sewage*
Aeration Tank
Organic Loading,
Process Mode Plant Design lbs BOD[5]/day/
Average Flow 1000 cu. ft.
_______________________________________________________________
Conventional, Less than 1 mgd
Complete Mix, Contact 35
Stabilization,**
Step Aeration,
Tapered Aeration
1 mgd or greater 50
_______________________________________________________________
Extended Aeration 15***
Single Stage Nitrification
_______________________________________________________________
* Where significant industrial wastes will be tributary to the
process, design modification shall be made as required by
subsection (a)(4), to assure compliance with effluent standards.
** Total aeration capacity includes both contact and reaeration
capacities.
*** Detention time at Design Average Flow for extended aeration shall
be 24 hours. This requirement may govern tank capacity. Detention
time for single stage activated sludge for nitrification is
governed by Section 370.1210(c)(3)(B).
e) Aeration Tanks
1) Multiple Units
Multiple tanks shall be provided. Tanks shall be designed so
that each tank may be dewatered and operated independently.
2) Tank Geometry
The dimensions of each independent mixed liquor aeration tank
or return sludge reaeration tank shall be such as to
maintain effective mixing and utilization of air. Liquid
depths should not be less than 10 feet. The shape of the
tank, the location of the inlet and outlet and the
installation of aeration equipment shall provide for
positive control of short-circuiting through the tank.
3) Freeboard
All aeration tanks shall have a freeboard of not less than 18
inches. Greater heights are desirable. Suitable water spray
systems or other approved means of froth and foam control
shall be provided if foaming is anticipated.
4) Inlet and Outlet Control
Inlets and outlets for each aeration tank unit shall be
suitably equipped with valves, gates, stop plates, weirs, or
other devices to permit balancing, proportioning, and
measuring the flow to and from any unit and to maintain
reasonably constant liquid level. The hydraulic elements of
the system shall permit the design peak flow to be carried
with any single aeration tank out of service.
5) Conduits
Channels and pipes carrying liquids with solids in suspension
shall be designed to maintain self-cleansing velocities or
shall be agitated to keep such solids in suspension at all
design rates of flow. Adequate provisions should be made to
drain segments of channels which are not being used due to
alternate flow patterns.
f) Aeration Equipment
1) General
A) Aeration requirements depend upon mixing energy, BOD
loading, degree of treatment, oxygen uptake rate, mixed
liquor suspended solids concentration and sludge age.
Aeration equipment shall be capable of maintaining a
dissolved oxygen concentration of 2.0 mg/1 in the
aeration tanks under all design loads. Energy transfer
shall be sufficient to maintain the mixed liquor solids
in suspension.
B) In the case of nitrification, the oxygen requirement for
oxidizing ammonia must be added to the above requirement
for carbonaceous BOD removal. The nitrogen oxygen
demand (NOD) shall be taken as 4.6 times the diurnal
peak ammonia (as nitrogen) content of the influent. In
addition, the oxygen demands due to recycle flows such
as sludge processing, return from excess flow first
flush storage and other similar flows, must be taken
into account due to the high concentrations of BOD and
ammonia associated with such flows.
C) Careful consideration should be given to maximizing
oxygen utilization per unit power input. Unless flow
equalization is provided, the aeration system should be
designed to match the diurnal organic load variation
while economizing on power input.
2) Diffused Air Systems
A) Except as noted in subsection (f)(2)(B) below, normal
aeration tank air requirements shall be based upon a
design figure of 1,500 cu. ft. of air supplied/lb. of
BOD[5] applied to the aeration tanks. This design
figure assumes that the equipment is capable of
transferring 1.0 lb. of oxygen to the aeration tank
contents/lb. of BOD[5] applied to the aeration tank. For
the extended aeration process, air requirements shall
be based on a design figure of 2250 cu. ft. of air
supplied per lb. of BOD[5] applied to the aeration tanks
to account for oxygen demand for endogenous respiration
and ammonia (as nitrogen) for normal strength waste.
Refer to Section 370.1210(c) for nitrification
requirements.
B) Air requirements may be determined based upon
transferring 1.0 lb. oxygen/lb. of applied oxygen
demand, as determined by subsection (f)(1) above, using
standard equations incorporating the factors listed
below. When using this design technique, the field
oxygen transfer efficiency of the equipment shall be
included in the specifications, and the detailed design
computations shall be contained in the basis of design:
i) Tank depth;
ii) Alpha factor of the waste;
iii) Beta factor of the waste;
iv) Documented aeration device transfer efficiency;
v) Minimum aeration tank dissolved oxygen
concentrations;
vi) Critical wastewater temperature;
vii) Plant altitude.
C) In the absence of experimentally determined alpha and
beta factors for the design described in subsection
(f)(2)(B) above, wastewater transfer efficiency shall be
assumed to be no more than 50% of clean water efficiency
for plants treating primarily (90% or greater) domestic
sewage. Treatment plants whose waste contains higher
percentages of industrial wastes shall use a
correspondingly lower percentage of clean water
efficiency and shall submit calculations to justify such
a percentage. The design wastewater oxygen transfer
efficiency of the equipment shall be included in the
specifications.
D) The specified capacity of blowers or air compressors,
particularly centrifugal blowers, should take into
account that the air intake temperature may reach 115
F or higher and the pressure may be less than normal.
The specified capacity of the motor drive should also
take into account that the intake air may be -20 F or
less and may require oversizing of the motor or a means
of reducing the rate of air delivery to prevent
overheating or damage to the motor.
E) The blowers shall be provided in multiple units, so
arranged and in such capacities as to meet the maximum
total air demand with the single largest unit out of
service. The design shall also provide for varying the
volume of air delivered in proportion to the load demand
of the plant.
F) The air diffusion piping shall be capable of delivering
200 percent of the design air requirements. Air piping
systems should be designed such that the friction head
loss from the blower outlet (or silencer outlet where
used) to the diffuser inlet does not exceed 0.5 psi at
100 percent of design air requirements at average
operating conditions for temperature and pressure.
G) The spacing of diffusers should be in accordance with
the oxygenation requirements through the length of the
channel or tank, and should be designed to facilitate
adjustments of their spacing without major revision to
air header piping. Diffusers in any single assembly
shall have substantially uniform pressure loss.
H) Individual assembly units of diffusers shall be equipped
with control valves, preferably with indicator markings
for throttling and for complete shut off. The
arrangement of diffusers shall also permit their
removal for inspection, maintenance and replacement
without dewatering the tank and without shutting off the
air supply in the tank, unless the dewatered aeration
basins are no more than 25% of the total aeration basin
capacity. Total aeration basin capacity shall include
the basins in both stages of a two-stage activated
sludge process.
I) Air filters shall be provided in numbers, arrangement,
and capacities to furnish at all times an air supply
sufficiently free from dust to prevent clogging of the
diffuser system used.
3) Mechanical Aeration Systems
A) Oxygen requirements shall be determined in accordance
with subsections (f)(2)(B) and (f)(2)(C) above.
B) The mechanism and drive unit shall be designed for the
expected conditions in the aeration tank in terms of
the power performance. Certified testing shall verify
mechanical aerator performance. The design field oxygen
transfer efficiency of the equipment shall be included
in the specifications, and the detailed design
computations shall be contained in the basis of design.
C) The mechanical aerators shall be provided in multiple
units, so arranged and in such capacities as to maintain
all biological solids in suspension, meet maximum oxygen
demand and maintain process performance with the largest
unit out of service. Provision shall be made for varying
the amount of oxygen transferred in proportion to the
load demand on the plant.
D) Due to high heat loss, the mechanism as well as
subsequent treatment units shall be protected from
freezing.
E) Motors, gear housing, bearings and grease fittings shall
be easily accessible and protected from inundation and
spray as necessary for proper functioning of the unit.
g) Return Sludge Equipment
1) Return Sludge Rate
The rate of sludge return, expressed as a percentage of
design average flow of sewage, shall be variable between
limits of 15 and 100 percent.
2) Return Sludge Pumps
A) If motor driven return sludge pumps are used, the
maximum return sludge capacity shall be obtained with
the largest pump out of service. The rate of sludge
return shall be varied by such means as variable speed
motors or drives, multiple constant speed pumps, or
telescoping valves. A positive head should be provided
on pump suctions. Pumps shall be capable of passing
spheres of at least 3 inches in diameter. Pump suction
and discharge openings shall be at least 4 inches in
diameter.
B) If air lift pumps are used for returning sludge from
each settling tank, no standby unit shall be required
provided that the design of the air lifts is such as to
facilitate their rapid and easy cleaning. Air lifts
should be at least 3 inches in diameter and provided
with adjustable air valving to permit flow control in
accordance with subsection (g)(1) above.
3) Return Sludge Piping
Suction and discharge piping should be at least 4 inches in
diameter and should be designed to maintain a velocity of not
less than 2 feet per second when return sludge facilities
are operating at normal return sludge rates. Suitable
devices for observing, measuring, sampling and controlling
return activated sludge flow from each settling tank shall
be provided.
4) Waste Sludge Control
Waste sludge control facilities should have a maximum
capacity of not less than 25 percent of the average rate of
sewage flow and function satisfactorily at rates of 0.5
percent of average sewage flow. Means for observing,
measuring, sampling and controlling waste activated sludge
flow shall be provided. Waste sludge may be discharged to
the primary settling tank, concentrator or thickening tank,
sludge digestion tank, vacuum filters, or any practical
combination of these units. Refer to Sections 370.820 and
370.710(b)(1)(A).
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.930 Waste Stabilization Ponds and Aerated Lagoons>>
a) Supplement To Engineer's Report
1) The engineer's report shall contain pertinent information on
location, geology, soil conditions, area for expansion, and
any other factors that will affect the feasibility and
acceptability of the proposed treatment.
2) Supplementary Field Survey Data
The following information must be submitted in addition to
that required in Section 370.111:
A) The location and direction of all residences, commercial
development, and water supplies within 1/2 mile of the
proposed pond.
B) Soil borings to determine surface and subsurface soil
characteristics of the immediate area and their effect
on the construction and operation of a pond located on
the site.
C) Data demonstrating anticipated percolation rates at the
elevation of the proposed pond bottom.
D) A description, including maps showing elevations and
contours of the site and adjacent area suitable for
expansion.
E) Sulfate content of the water supply.
F) Identification of the location, depth and discharge
point of any field tile in the immediate area of the
proposed site.
b) Location
1) Distance From Habitation
A pond site should be as far as practicable from habitation
or any area which may be built up within a reasonable future
period.
2) Prevailing Winds
If practicable, ponds should be located so that local
prevailing winds will be in the direction of uninhabited
areas. Preference should be given sites which will permit an
unobstructed wind sweep across the ponds, especially in the
direction of the local prevailing winds.
3) Surface Runoff
Adequate provisions shall be made to divert storm water
around the ponds and otherwise protect pond embankments.
4) Ground Water Contamination
The requirements of the Illinois Groundwater Protection Act
[415 ILCS 55] shall be taken into account in the siting of
ponds. Ponds should not be located proximate to water
supplies and other facilities subject to contamination or
located in areas of porous soils and fissured rock
formations. If conditions dictate using such a site, then
the potential for and the means necessary to combat
groundwater contamination shall be critically evaluated in
the engineer's report. In such locations, the Agency will
require groundwater monitoring wells.
5) Geology
Ponds shall not be located in areas subject to sink holes and
mine subsidence. Soil borings and tests to determine the
characteristics of surface soil and subsoil shall be made a
part of preliminary pond site selection surveys. Gravel and
limestone areas should be avoided; however, where conditions
dictate locating ponds in such areas and the minimum
separation between the pond bottom and gravel or limestone
will be less than 10 feet, the Agency shall be contacted
about the necessary precautions.
c) Basis Of Design
1) Organic Loading
A) Waste Stabilization Ponds
The organic loading on each cell shall not exceed the
loadings listed below. If more accurate design
information for the particular type waste is not
submitted and supported by the engineer, subsequent
cells shall be sized for an organic loading of 25% of
each preceding cell.
i) North of Illinois Highway 116 (Pontiac) 22 lbs.
BOD per acre per day.
ii) Between Illinois Highway 116 and U.S. Highway 50,
26 lbs. BOD per acre per day.
iii) South of U.S. Highway 50 (Salem-Carlyle) 30 lbs.
BOD per acre per day.
B) Aerated Lagoons
The organic loading for aerated lagoons shall not exceed
0.5 lb. BOD[5] day per 1,000 cu. ft. first cell nor 0.3
lb. BOD[5] day per 1,000 cu. ft. on any subsequent
cells. If more accurate design information for the
particular type waste is not submitted and supported by
the engineer, the second and third cells shall be sized
for an organic loading of 25% of each preceding cell.
2) Depth
A) Waste Stabilization Ponds
The minimum operating liquid depth for waste
stabilization ponds should be 2 feet. The maximum
operating liquid depth shall be based on design storage
requirements and shall not be less than 5 feet.
B) Aerated Lagoons
The design water depth for aerated lagoons should be 10
to 15 feet. This depth limitation may be altered
depending on the aeration equipment, waste strength,
climatic and geological conditions.
3) Aeration Requirements For Aerated Lagoons
A) Aeration systems shall be designed to provide, with the
largest unit out of service, a minimum of 1,500 cu. ft.
of air/lb. of BOD[5] in the raw waste (1.5 lbs. of
oxygen/lb. of BOD[5] plus oxygen required to oxidize
the ammonia present in the raw waste). The aeration
equipment shall be located to ensure proper mixing and
distribution of oxygen in proportion to oxygen demand in
multiple cells. Splash type aerators with motors above
the water surface may not be used.
B) Where hose type diffusers are used, the holes shall be
of sufficient size to prevent plugging by dissolved
solids incrustation.
4) Multiple Cells
A minimum of two cells to be operated in series or parallel
should be provided for all waste stabilization ponds when
they are utilized as a part of the primary and secondary
treatment process. The number of cells required for aerated
lagoons are dependent upon the degree of treatment required.
Refer to subsection (c)(6).
5) Pond Shape
The shape of all primary cells should be such that there are
no narrow or elongated portions. Round, square, or
rectangular ponds with a length not exceeding 3 times the
width are considered most desirable. No islands, peninsulas,
or coves should be permitted. Dikes should be rounded at
corners to minimize accumulations of floating materials.
6) Solids Removal
All lagoon systems shall include effective solids removal
facilities. Design criteria for acceptable solids removal
facilities are contained in Subpart K. Other solids removal
facilities may be approved in accordance with Section
370.520(b).
d) Construction Details
1) Embankments and Dikes
A) Material
Embankments and dikes shall be constructed of relatively
impervious materials and compacted to at least 90%
Standard Proctor density to form a stable structure.
Vegetation and other unsuitable material shall be
removed from the area upon which the embankment is to be
placed.
B) Top Width
The minimum embankment top width should be 8 feet to
permit access of maintenance vehicles. Lesser top
widths will be considered for very small installations.
C) Maximum Embankment Slopes
i) Inner Slopes:
3 horizontal to 1 vertical.
ii) Outer Slopes:
3 horizontal to 1 vertical.
D) Minimum Embankment Slopes
i) Inner Slopes:
4 horizontal to 1 vertical. Flatter slopes are
sometimes specified for larger installations
because of wave action but have the disadvantage of
added shallow areas conducive to emergent
vegetation.
ii) Outer Slopes:
Outer slopes shall be sufficient to prevent surface
runoff from entering the ponds.
E) Freeboard
Minimum freeboard shall be 3 feet except for very small
installations 2 feet may be acceptable.
F) Erosion Control Requirements
For effective erosion control on the lagoon embankments,
both seeding and riprap (or acceptable alternate) are
required.
i) Seeding
Embankments shall be seeded from the outside toe to
1 foot above the high water line on the dikes,
measured on the slope. Perennial type, low
growing, spreading grasses that withstand erosion
and can be kept mowed are most satisfactory for
seeding of embankments. In general, alfalfa and
other long rooted crops should not be used in
seeding, since the roots of this type plant are apt
to impair the water holding efficiency of the
dikes. The County Agricultural Extension Agent
can usually advise as to hardy, locally suited
permanent grasses which would be satisfactory for
embankment seeding.
ii) Riprap
Riprap (or acceptable alternate) shall be placed on
the inner slope of the embankments from 1 foot
above the high water mark to 1 foot below the low
water level. Riprap shall be comprised of a
two-layer system consisting of a minimum 4-inch
layer of coarse aggregate that meets the Illinois
Department of Transportation (IDOT) Standard
Specification for Road and Bridge Construction
adopted January 1, 1997 for the gradations in the
range of CA-6 through CA-10 and a minimum 12-inch
layer of stone. The rock layer shall consist of
evenly graded material with a maximum weight of 150
pounds per piece and shall meet the IDOT gradations
for rock of either Grade No. 3 or 4.
2) Pond Bottom
A) Uniformity
Finished elevations shall not be more than 3 inches from
the average elevation of the bottom. Shallow or
feathering fringe areas usually result in locally
unsatisfactory conditions.
B) Vegetation
The bottom shall be cleared of vegetation and debris.
Organic material thus removed shall not be used in the
dike core construction. However, suitable topsoil
relatively free of debris may be used as cover material
on the outer slopes of the embankment.
C) Soil
Soil used in constructing the pond bottom (not including
the seal) shall be relatively incompressible and tight.
Porous topsoil shall be removed. Porous areas, such as
gravel or sandy pockets, shall be removed and replaced
with well compacted clay. The entire bottom shall be
compacted at or up to 4% above the optimum water content
to at least 90% Standard Proctor density.
D) Seal
The pond bottom and embankments shall be sealed such
that seepage loss through the seal is as low as
possible. Seals consisting of soils, bentonite or
synthetic liners may be used, provided that the
permeability, durability and integrity of the proposed
material is demonstrated for anticipated conditions.
The results of a testing program that substantiates the
adequacy of the proposed seal shall be incorporated into
or accompany the engineering report. Standard ASTM
procedures or similar accepted testing methods shall be
used for all tests.
i) A seal consisting of soil materials shall have a
thickness of at least 24 inches and a permeability
of less than 1x10(-7) cm per second. Provision
shall be made in the specifications for
demonstrating the permeability of the seal after
completion of construction and prior to filling the
pond.
ii) For a seal that consists of a synthetic liner,
seepage loss through the liner shall not exceed a
quantity equivalent to seepage loss through a soil
seal as described above.
E) Prefilling
Prefilling the pond after completion of testing is
recommended in order to protect the seal from weed
growth, to prevent drying and cracking and to reduce
odor during initial operation. The pond dikes must be
completely prepared as described in subsection
(d)(1)(F). Synthetic liners shall be protected from
damage during installation and filling.
3) Influent Lines
A) Material
Any generally accepted material for underground sewer
construction will be given consideration for the
influent line to the pond. The material selected should
be adapted to local conditions. Special consideration
must be given to the character of the wastes,
possibility of septicity, exceptionally heavy external
loadings, abrasion, the necessity of reducing the number
of joints, soft foundations, and similar problems.
B) Manholes
A readily accessible manhole shall be installed at the
terminus of the trunk sewer or the force main, unless
the force main discharges directly to the lagoon as
described in subsection (d)(3)(H). The manhole shall be
located as close to the dike as topography permits and
its invert should be at least 6 inches above the maximum
operating level of the pond to provide sufficient
hydraulic head without surcharging the manhole.
Surcharging of the sewer upstream from the inlet manhole
is not permitted.
C) Grade
i) Influent line can be placed at zero grade and
should be located along the bottom of the pond so
that the top of the pipe is just below the average
elevation of the pond bottom. The pipe shall have
adequate seal below it.
ii) The laying of the influent pipe on the surface of
the pond bottom is prohibited.
D) Point of Discharge
Influent lines to the primary cell should terminate at
approximately the third point farthest from the outlet
structure. For interconnecting piping to secondary
cells refer to subsection (d)(4)(B).
E) Flow Distribution
Flow distribution structures shall be designed to
effectively split hydraulic and organic loads
proportionally to primary cells. Refer to Section
370.520(f).
F) Submerged Inlets
Submerged inlet lines shall discharge horizontally into
a shallow, saucer-shaped depression which should extend
below the pond bottom not more than the diameter of the
influent pipe plus 1 foot.
G) Discharge Apron
The end of the discharge line should rest on a suitable
concrete apron with a minimum size of 2 feet square.
H) Force Mains
Force mains discharging directly to lagoons are
permitted if the force main has a freefall discharge
into the lagoon and is not turned upward at the point of
discharge. The point of discharge shall be at
approximately the third point farthest from the outlet
structure and the pipe shall be sloped for drainage into
the lagoon to avoid freezing.
I) Anti-Seep Collars
Anti-seep collars shall be used on all piping passing
through or under the lagoon embankments.
4) Outlet Structures and Interconnecting Piping
A) Outlet Structure
i) Outlet structures shall be designed to allow the
operating level of the pond to be adjusted to
permit operation at depths of 2 feet to the maximum
depth. The design shall also allow effluent to be
drawn from various depths below all operating
levels. All structures and devices such as weirs,
gates and valves shall be watertight and capable of
being easily adjusted by the operator without the
need of additional mechanical equipment. Wooden
stop-planks are not acceptable for level control.
ii) Drawoff lines should not be located any lower than
12 inches off the bottom to control eroding
velocities and avoid pickup of bottom deposits.
iii) A locking device should be provided to prevent
unauthorized access to the level control
facilities.
iv) When possible, the outlet structure should be
located on the windward side to prevent short
circuiting. The outlet structure shall be properly
baffled to prevent the discharge of floating
material.
v) Consideration must be given in the design of all
structures to protect against freezing or ice
damage under winter conditions.
B) Interconnecting Piping and Unit Bypass
i) Interconnecting piping and overflows should be
constructed of materials that will withstand damage
during construction and operation, giving special
consideration to damage that may occur during
compaction of embankments and damage to shallow
piping. Piping shall be sized to allow transfer of
maximum flows without raising the lagoon water
level by more than 6 inches in the upstream cell.
In no case shall interconnecting pipe be less than
8 inches in diameter. Interconnecting piping
between cells should be valved or provided with
other arrangements to regulate flow between
structures and permit flexible depth control.
ii) The interconnecting pipe to the secondary cell
should discharge horizontally near the lagoon
bottom to minimize need for erosion control
measures and should be located as near the dividing
dike as construction permits.
iii) Piping and valves shall be provided so that each
cell can be operated independently of any other
cell. Provision shall be made for independent cell
dewatering.
C) Anti-Seep Collars
Anti-seep collars shall be used on all interconnecting
and outlet piping passing through or under the lagoon
embankments.
5) Miscellaneous
A) Fencing
The pond area shall be enclosed with a suitable fence to
preclude livestock and discourage trespassing. A
vehicle access gate of sufficient width to accommodate
mowing equipment shall be provided. All access gates
shall be provided with locks.
B) Warning Signs
Appropriate signs should be provided along the fence
around the pond to designate the nature of the facility
and advise against trespassing.
C) Flow Measurement, Sampling and Level Gauge
Provisions for flow measurement and sampling shall be
provided on the inlet and outlet. Pond level gauges
shall be provided. The NPDES permit monitoring
requirements for the facility shall be taken into
account. Elapsed time meters on pumps or calibrated
weirs may be used as flow measurement devices for
lagoons.
D) Sludge Removal
When an existing lagoon is to be upgraded, the project
design shall provide for removal of any sludge
accumulation in the existing lagoon. The sludge removed
shall be disposed of in accordance with IPCB
regulations.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.940 Intermittent Sand Filtration for Secondary Treatment>>
a) Applicability
Use of the intermittent sand filter for secondary treatment is
generally limited to weak to normal strength wastewaters which are
amenable to biological treatment. Cold weather operational
problems may preclude the use of this process unless the influent
temperature to the filter is adequate to allow efficient filter
operation necessary to meet the applicable effluent standards.
b) Pretreatment Requirements
Wastewaters applied to intermittent sand filters must be
substantially free of grit, debris, oil and grease, floating and
suspended materials, and components which inhibit biological
processes and cause rapid clogging of the filter. Special
consideration shall be given to the design of preceding treatment
units, including dosing facilities, to limit heat loss during
winter operation.
c) Multiple Units
Intermittent sand filters shall be provided in multiple units,
designed for independent operation and maintenance.
d) Location
Intermittent sand filters treating septic tank or primary effluent
should be restricted to relatively isolated locations or otherwise
modified in order to minimize odor nuisances.
e) Recirculation
Recirculation of filter effluent may be practiced in order to
attenuate and equalize organic and hydraulic loads to the filter,
and improve unit process efficiency, control odors, and improve
day-to-day reliability.
1) Rate
A recirculation rate of up to 300% of the settled sewage load
to the filter may be provided.
2) Variability
The capability of varying the recirculation rate allows
greater process control and optimization of process
efficiency. This feature shall be included where
recirculation is provided.
f) Dosing
1) Dosing Volumes
The dosing facilities shall be designed for a capacity of
2,500 gallons per 1,000 sq. ft. of filter bed to be dosed at
any given time.
2) Dosing Rates for Siphons or Pumps
Siphons (at minimum head) or pumps shall have a discharge
capacity at least 100% in excess of the maximum rate of
inflow to the dosing tank, including recirculation, and at
average head, at least 90 gallons per minute per 1,000 square
feet.
3) Discharge Line Capacity
The discharge lines to the beds shall have sufficient
capacity to permit the full rated discharge of the siphons or
pumps.
g) Construction Details
1) Earth Base
The earth base of the filters shall be sloped to the
underdrains.
2) Underdrains
The sand filter shall be provided with open-joint or
perforated pipe underdrains. They should be sloped to the
outlet and spaced not to exceed 10 foot centers. Vertical
riser vents shall be provided at both ends of each underdrain
pipe and shall be located as not to be overtopped at maximum
dosing depth.
3) Media
A) Gravel Base
Clean graded gravel, preferably placed in at least three
layers, should be placed around the underdrains and to a
depth of at least 6 inches over the top of the
underdrains. Crushed stone may not be used in lieu of
gravel. Suggested gradings for the three layers are:
1 1/2" to 3/4", 3/4" to 1/4", 1/4" to 1/8".
B) Sand
At least 24 inches of clean washed sand shall be
provided. Sand shall be durable and relatively
insoluble in sewage. Clay content shall be less than 1%
by weight. The effective size shall be 0.3 to 1.0
millimeter (mm). The uniformity coefficient shall not
be greater than 3.5.
4) Splash Slabs
Splash slabs shall be provided at each point of discharge to
the filter. A means of dissipating the energy of the
discharge velocity shall be provided around the periphery of
the splash slab.
5) Curbs
Provision shall be made to prevent soil and surface runoff
from entering the filter area. Curbs should be high enough
to hold the maximum dose and provide adequate freeboard.
6) Distribution System
A) Arrangement
Provision shall be made for even distribution of the
flow on the filter surface. If troughs or piping are
used, they shall be so located that the maximum lateral
travel of the flow on the media surface is not more than
20 feet.
B) Drains
Troughs, discharge piping or other distribution
equipment shall be sloped to drain to prevent freezing.
h) Loading Rates
The loading rates shall be based on the raw sewage flow and
organic strength. The following loading rates shall not be
exceeded:
Raw Waste Strength Dose Rate
(BOD[5] mg/l) (gals./ft.(2)/day)
_______________ __________________
100 to 200 3
200 to 300 2
above 300 1
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
SUBPART J: DISINFECTION
<BSection 370.1000 General>>
Where needed to meet applicable standards, disinfection of the effluent
shall be provided. The design shall provide for meeting both the bacterial
standards and any disinfectant residual limits applicable to the effluent.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.1010 Disinfection Process Selection>>
a) The disinfection process should be selected after due
consideration of waste characteristics, type of treatment
processes provided prior to disinfection, waste flow rates, waste
pH, disinfectant demand rates, current technology application,
cost of equipment, chemical availability, power costs and
maintenance requirements. Areawide public safety shall be
considered where large liquid chlorine or sulfur dioxide
containers are to be handled.
b) Chlorine may be used in the form of liquid chlorine or calcium or
sodium hypochlorite. Dechlorination will be required where
necessary to meet applicable chlorine residual effluent
limitations.
c) An ultra-violet radiation system may be used as an alternative
disinfection process.
d) Other alternative means of disinfection will be evaluated
according to the provisions of Section 370.520(b).
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.1020 Chlorine Disinfection>>
a) Type of Feed Equipment
The types of chlorine feed equipment include:
1) Vacuum solution feed by gas;
2) Direct gas feed;
3) Hypochlorite solution positive displacement pump feed;
4) Hypochlorite tablet feed.
b) Selection of Feed Equipment
The selection of the type of chlorine feed equipment shall take
into account operator safety and overall public safety relative to
the proximity of the sewage treatment plant to populated areas and
to the security of the gas cylinder or container storage.
c) Output Capacity of Gas Chlorine Cylinders
<PDelivery Rates (lbs of chlorine/day)>>
Ambient 100 pound 150 pound 1 Ton
Temp. F Cylinder Cylinder Container
40 6 9 100
50 14 21 240
60 23.7 35.5 385
70 32 47.5 536
80 41.2 62 700
Some types of vacuum chlorinators can deliver chlorine at rates
greater than those listed above under the same conditions. When
designs include rates in excess of those indicated above,
manufacturer's specifications and test results shall be provided.
d) Standby Equipment and Spare Parts
Standby equipment of sufficient capacity should be available to
replace the largest unit during shutdowns. Spare parts shall be
available for all chlorinators to replace parts which are subject
to wear and breakage.
e) Potable Water Supply Protection
An ample supply of water shall be available for operating the
chlorinator. Where a booster pump is required, duplicate
equipment should be provided and, when necessary, also standby
power (refer to Section 370.550(a)(4)). Protection of a potable
water supply shall conform to the requirements of Section
370.550(b)(3). In-line backflow preventers are not acceptable.
f) Chlorine Gas Supply
1) Cylinders
The use of 1-ton containers should be considered where the
average daily chlorine gas consumption is over 150 pounds.
All upright chlorine cylinders shall be strapped securely to
prevent tipping.
2) Tank Cars
A) At large installations the use of tank cars, generally
accompanied by evaporators, may be considered. Areawide
public safety shall be evaluated as a part of the
considerations. Provision shall be made for a chlorine
supply during tank car switching.
B) The tank car being used for the chlorine supply shall be
located on a dead end, level track that is a dedicated
siding. The tank car shall be protected from accidental
bumping by other railway cars by a locked de-rail
device, a closed lock switch, or both. The area shall
be clearly posted "DANGER-CHLORINE." The tank car shall
be secured by adequate fencing with locked gates for
personnel and rail access.
C) The tank car site shall be provided with an operating
platform at the unloading point that allows for easy
access to the protective housing on the tank car for
flexible feed line connection and valve operation. Area
lighting adequate for night time operation and
maintenance shall be provided.
3) Scales
A) Scales shall be provided for weighing cylinders and
containers at all plants using chlorine gas.
B) At large plants, indicating and recording scales are
recommended. At a minimum, a platform scale shall be
provided. Scales shall be made of corrosion-resistant
material. Scales should be recessed unless hoisting
equipment is provided or the scales are low enough to
allow the cylinders to be rolled onto them.
4) Evaporators
Where manifolding of several cylinders or containers will be
required to evaporate sufficient chlorine, consideration
should be given to liquid drawoff and installation of an
evaporator.
5) Leak Detection and Controls
A bottle of ammonium hydroxide solution should be available
for detecting chlorine leaks. Consideration should also be
given to the provision of caustic soda solution reaction
tanks for absorbing the contents of leaking 1-ton containers
where such containers are in use. Also, when cylinders,
containers or tank cars are used, a leak repair kit approved
by the Chlorine Institute shall be provided. At
installations using over 150 pounds of chlorine gas per day
consideration should be given to the installation of
automatic gas detection and related alarm equipment.
g) Piping and Connections
1) Piping systems should be as simple as possible, and shall be
specially selected and manufactured to be suitable for
chlorine service, with a minimum number of joints. Piping
should be well supported and protected against temperature
extremes.
2) The chlorine system piping shall be color coded and labeled
to distinguish it from sulfur dioxide and other plant piping.
Where sulfur dioxide is used, the piping and fittings for
chlorine and sulfur dioxide systems shall be designed so that
interconnection between the two systems cannot occur.
h) Housing
1) Container and Equipment Location
Containers and feed equipment should be located indoors, in a
suitable fire-resistant building. Gas cylinders should be
protected from direct sunlight if not located indoors.
A) Separation
If gas chlorination equipment and chlorine cylinders or
containers are to be housed in a building used for other
purposes, the chlorine cylinders or containers and
equipment shall be located in an isolated room. This
room shall not contain any sulfonation equipment, sulfur
dioxide cylinders or other equipment unrelated to
chlorination. Common walls to other areas of the
building shall be gastight. Doors to this room shall
open only to the outside of the building and shall be
equipped with panic hardware. Rooms shall be at ground
level and shall permit easy access to all equipment.
Storage areas should be separated from the feed area.
B) Inspection Window
A clear gastight window shall be installed in the
chlorinator room to permit the units to be viewed and
gauges to be read without entering the room.
C) Heat
Chlorinator housing facilities shall be provided with a
means of heating so that a temperature of at least 60 F
can be maintained. Where chlorine gas is to be
withdrawn from cylinders or containers, the cylinders or
containers shall be maintained at essentially room
temperature. The room shall be protected from excessive
heat. If liquid chlorine is to be withdrawn from the
cylinders or containers to an evaporator unit, the feed
cylinders or containers may be located in an unheated
area.
3) Ventilation For Gas Chlorination Systems
A) Forced, mechanical ventilation shall be installed which
will provide 1 complete air change per minute. The
entrance to the air exhaust duct from the room shall be
within 12 inches of the floor and the point of discharge
shall be so located as not to contaminate the air in the
immediate vicinity of the entrance door to the
chlorinator room or ventilation inlet or window or
entrance door to any buildings or inhabited areas.
Where the public may be subjected to extensive exposure
to chlorine in case of chlorine leaks, scrubbers may be
required on the ventilation discharge.
B) The chlorination room air inlets shall be so located as
to provide cross ventilation with air and at such
temperature that will not adversely affect the
chlorination equipment. The vent hose from the
chlorinator shall discharge to the outside atmosphere
above grade.
4) Electrical Controls
The controls for the fans and lights shall be provided at
those locations where it is necessary to enter the
chlorination room and shall automatically operate when the
door is opened and continue to operate when the operator
enters the room and the door is closed. Provision shall be
made for manual operation of controls from the outside of the
room without opening the door.
5) Outdoor Cabinet Housing
Outdoor shallow cabinet-type units, with wide opening doors,
that are shallow enough not to need or require operator
entry, may be used to house the containers and feed
equipment. Use of such cabinets shall be limited to small
plants that provide seasonal disinfection or use less than 10
pounds of chlorine per day. Only two chlorine gas cylinders
of 150 pounds or less on line may be housed in the cabinets.
The following items shall be provided for in the design:
A) The cabinet structure shall be located on and securely
anchored to a concrete slab sized to allow for safe
transport and handling of the cylinders. The structure
and slab shall be capable of withstanding expected wind
loadings on the cabinet. The design of the cabinet
support slab shall take into account the effects of
frost and settling due to soil stability. Flexible
piping connections should be considered for lines
connected to the cabinet.
B) The cabinet shall be protected from direct sunlight to
prevent overheating of the chlorine cylinders.
C) The cabinet doors shall extend the full width of the
long side of the cabinet structure so that the full
interior of the cabinet is exposed with the door open.
Provision shall be made to secure the open doors while
the operator is changing cylinders and maintaining the
feed equipment.
D) The cabinet depth shall not exceed 24 inches. The feed
equipment shall be positioned to allow easy access for
maintenance and to allow observation of the gauges and
meters.
E) Provision shall be made for chains, wall mounted
fastener hooks or similar means for anchoring the
chlorine cylinders to prevent tipping.
F) The cabinet structure shall be corrosion resistant to
chlorine gas.
G) Where electrical power is available, the cabinet should
be placed in a well-lighted area.
i) Respiratory Protection Equipment
Respiratory protection equipment meeting the requirements of the
National Institute for Occupational Safety and Health (NIOSH)
shall be available at all installations where chlorine gas is
handled and shall be stored in a convenient location outside of
any room where chlorine is used or stored. The respiratory
protection units shall use compressed air, have at least a
30-minute capacity, and be compatible with or exactly the same as
NIOSH-approved units used by the local fire department.
Instructions for using, testing, and replacing mask parts shall be
posted. At large installations, consideration should be given to
providing acid suits and fire suits.
j) Application of Chlorine
1) Contact Period
After thorough mixing, a minimum contact period of 15 minutes
at design peak hourly flow or maximum rate of pumpage shall
be provided.
2) Chlorinator Dosing Rate Capacity
Chlorinators shall be designed to have a capacity adequate to
produce an effluent that will meet the applicable bacterial
limits. Where necessary to meet the operating ranges,
multiple units shall be provided for adequate peak capacity
and for a sufficiently low feed rate on turn down to allow
proper chlorine residual. The chlorination system shall be
designed on a rational basis and calculations justifying the
equipment sizing and number of units shall be submitted for
the whole operating range of flow rates, including the
minimum turn down capacity for the type of control to be
used. System design considerations shall include the
controlling sewage flow meter (sensitivity and location),
telemetering equipment and chlorinator controls. For treated
normal domestic sewage the following dosing capacity, based
on design average flow, is suggested (see Section
370.520(c)(1)):
<PType of Treatment>> <PDosage (mg/l)>>
Primary Settled Sewage 20
Lagoon Effluent (unfiltered) 20
Trickling Filter Plant Effluent 10
Lagoon Effluent (filtered) 10
Activated Sludge Plant Effluent 6
Activated Sludge Plants with
Chemical Addition 4
Filtered Effluent Following
Mechanical Biological Treatment 4
k) Contact Tank
1) Mechanical means of sludge removal is recommended and should
be provided unless multiple chlorine tanks are provided.
Portable deck-level vacuum cleaning equipment may be used for
small treatment plants. Provisions for draining contact
tanks not equipped with mechanical sludge removal equipment
shall be provided, with the drain flow returned to process
for treatment.
2) Exception to the requirement of duplicate contact tanks may
be granted if the contact tank follows a sand filter or if
the main treatment works is a waste stabilization pond, with
provisions for storing the sewage flow for several days while
the contact tank is being cleaned.
3) Adequate mixing during the chlorine contact period shall be
insured by the installation of adequate baffling, air or
other mixing equipment. Facilities for the retention and
removal of floating scum shall be provided.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.1021 Dechlorination>>
a) General
Dechlorination of sewage plant effluents may be required to reduce
toxicity due to chlorine residuals.
b) Feed Equipment
1) Type
The common types of dechlorination feed equipment using
sulfur compounds include:
A) Vacuum solution feed of sulfur dioxide gas.
B) Positive displacement pump feed or aqueous solutions of
sulfite or bisulfite products.
2) Selection of Feed Equipment
The selection of the type of feed equipment using sulfur
compounds shall include consideration of operator safety and
overall public safety relative to the proximity of the sewage
treatment plant to populated areas and the security of the
gas cylinder storage. The selection and design of sulfur
dioxide feeding equipment shall take into account the fact
that the gas reliquifies very easily.
c) Output Capacity of Sulfur Dioxide Cylinders
The number of feed cylinders or containers necessary to meet the
design delivery rates shall be based on the physical,
thermodynamic and chemical properties for sulfur dioxide. Refer
to the Compressed Gas Association publication CGA G-3-1988 "Sulfur
Dioxide" or other standard reference sources for information on
sulfur dioxide properties.
d) Standby Equipment and Spare Parts
Standby equipment should be available of sufficient capacity to
replace the largest unit during shutdown. Spare parts to replace
parts that are subject to wear and breakage shall be available for
all sulfonators.
e) Potable Water Supply
An ample supply of water shall be available for operating the
sulfonator. Where a booster pump is required duplicate equipment
should be provided and, when necessary, standby power. (Refer to
Section 370.550(a)(4).) Protection of the potable water supply
shall conform to the requirements of Section 370.550(b)(6).
In-line back flow preventers may not be used.
f) Sulfur Dioxide Gas Supply
1) Cylinders
The use of 1-ton containers should be considered where the
average daily sulfur dioxide consumption is over 150 pounds.
All upright sulfur dioxide cylinders shall be strapped
securely to prevent tipping.
2) Tank Cars
A) The use of tank cars, generally accompanied by
evaporators, may be considered for large installations.
Areawide public safety shall be evaluated as part of the
considerations. Continuity of sulfur dioxide supply
shall be maintained during tank car switching.
B) The tank car being used for the sulfur dioxide supply
shall be located on a dead end, level track that is a
dedicated siding. The tank car shall be protected from
accidental bumping by other railway cars by a locked
de-rail device, a closed lock switch, or both. The area
shall be clearly posted "DANGER-SULFUR DIOXIDE." The
tank car shall be secured by adequate fencing with
locked gates for personnel and rail access.
C) The tank car site shall be provided with an operating
platform at the unloading point that allows for easy
access to the protective housing on the tank car for
flexible feed line connection and valve operation. Area
lighting adequate for night time operation and
maintenance shall be provided.
3) Scales
A) Scales shall be provided for weighing cylinders or
containers at all plants using sulfur dioxide gas.
B) At large plants indicating and recording scales are
recommended. At a minimum, a platform scale shall be
provided. Scales shall be made of corrosion resistant
material. Scales should be recessed unless hoisting
equipment is provided or the scales are low enough to
allow the cylinders to be rolled onto them.
4) Evaporator
Where the manifolding of several cylinders or containers will
be required to evaporate sufficient sulfur dioxide,
consideration should be given to liquid drawoff and
installation of an evaporator. A liquid nitrogen gas padding
system to enhance the liquid sulfur dioxide delivery rate
should be considered.
5) Leak Detection and Controls
Sulfur dioxide leak detection equipment shall be provided
which has a sensitivity level equal to that of ambient air
pollution monitoring equipment. Where cylinders, one-ton
containers and tank cars are used, a leak repair kit that is
compatible for use with sulfur dioxide gas shall be provided.
Leak repair kits used for chlorine gas (Section
370.1020(f)(5)) equipped with gasket materials suitable for
service with sulfur dioxide may be used. (See paragraphs
10.4 and 13.2 of "Sulfur Dioxide," Compressed Gas
Association, Inc., Publication CGA G-3-1988 for a discussion
of suitable materials.) Refer to Section 370.560.
g) Piping and Connections
1) Piping systems should be as simple as possible, with a
minimum number of joints, and shall be suitable for sulfur
dioxide service. Piping should be well supported and
protected against temperature extremes.
2) The piping for the sulfur dioxide system shall be color-coded
and labeled to distinguish it from chlorine piping, and the
system shall be designed so that interconnections with
chlorine piping cannot occur.
h) Housing
1) Container and Equipment Location
Containers and feed equipment should be located inside a fire
resistant building. Gas cylinders and containers should be
protected from direct sunlight.
A) Isolation
If gas sulfonation equipment and sulfur dioxide
cylinders will be located in a building also used for
other purposes, the sulfur dioxide equipment and
containers shall be located in an isolated room that
shall not contain any chlorination equipment, chlorine
containers or any other equipment unrelated to
sulfonation. Common walls to other areas of the
building shall be gastight. Doors to the room shall
open only to the outside and shall be equipped with
panic hardware. Rooms shall be at ground level and
shall allow easy access to all equipment. Storage areas
should be separated from feed areas; sulfur dioxide and
chlorine cylinders shall be stored in separate areas.
B) Inspection Window
A clear gastight window shall be installed in the
sulfonate room to permits the units to be viewed and
gauges to be read without entering the room.
2) Heat
Sulfonator housing facilities shall be provided with a means
of heating so that cylinder temperatures can be maintained in
the range of 90 to 100 F when sulfur dioxide is to be
withdrawn from the cylinder. The sulfonator room shall be
protected from excessive heat.
3) Ventilation for Sulfur Dioxide Systems
A) Forced, mechanical ventilation that will provide one
complete air change per minute shall be installed in the
sulfonator room. The entrance to the exhaust duct from
the room shall be within 12 inches from the floor and
the point of discharge shall be located so as not to
contaminate the air in the immediate vicinity of the
door to the sulfonator room or ventilation inlet to any
buildings or inhabited areas.
B) The air inlets to the sulfator room shall be located so
as to provide cross ventilation with air and at
temperatures that will not adversely affect the
sulfonation equipment. The vent hose from the
sulfonator shall discharge to the outside atmosphere
above grade.
4) Electrical Controls
Controls for fans and lights shall be located at the
entrances to the sulfonation room and shall automatically
operate when the door is opened and continue in operation
when the operator enters the room and the door is closed.
Provision shall be made for operation of the fans and lights
from the outside without opening the door.
i) Respiratory Protection Equipment
Respiratory protection equipment meeting the requirements of NIOSH
shall be available at all installations where sulfur dioxide gas
is handled and shall be stored in a convenient location outside of
any room where sulfur dioxide is used or stored. The units shall
use compressed air, shall have at least a 30-minute capacity and
shall be the same as or compatible with NIOSH-approved units used
by the local fire department. Instructions for using, testing and
replacing mask parts shall be posted. At large installations,
providing acid suits and fire suits should be considered.
j) Application of Sulfonation Chemicals
1) Contact Period and Reaeration
A minimum contact period of 30 seconds, including mixing
time, at design peak hourly flow or maximum pumpage rate
shall be provided. Mechanical mixers are required unless the
mixing facility will provide the necessary hydraulic
turbulence to assure thorough mixing. A means of reaeration
shall be provided to insure maintenance of the required
dissolved oxygen concentration in the effluent and the
receiving stream after sulfonation. When choosing a
reaeration method the fact that excess sulfur dioxide, formed
when the dechlorinating chemicals are dissolved in water, may
be expected to consume 1 mg of dissolved oxygen for every 4
mg of sulfur dioxide should be taken into account.
2) Sulfonation Dosing Rate Capacity
A) Capacity
Sulfonators shall be designed to have a capacity
adequate to produce an effluent that meets the
applicable chlorine residual effluent limits. Where
necessary to meet the operating ranges, multiple units
shall be provided for adequate peak capacity and to
provide a sufficiently low feed rate on turn down to
avoid depletion of the dissolved oxygen concentrations
in the receiving waters. The sulfonator system shall be
designed on a rational basis and calculations justifying
the equipment sizing and number of units shall be
submitted for the entire operating range, including the
minimum turn down capability for the type of control to
be used. System considerations shall include the
sensitivity and location of the controlling sewage flow
meter, the telemetering equipment and sulfonator
controls.
B) Dosing Rates
The design dosage rate of the sulfonation equipment
shall be based on the particular dechlorinating chemical
used and the applicable residual chlorine limits. The
following theoretical amounts of the commonly used
dechlorinating chemicals may be used for initial
approximations to size feed equipment.
Theoretical mg/l
required to neutralize
1 mg/l Cl[2]
Sulfur dioxide (gas) 0.90
Sodium meta bisulfite
(solution) 1.34
Sodium bisulfite
(solution) 1.46
The design shall take into account the fact that under
good mixing conditions approximately 10% more
dechlorinating chemical than theoretical value is
required for satisfactory results.
C) Liquid Solution Tanks
Mixing and dilution tanks for dechlorinating feed
solutions shall be provided as necessary to mix dry
compounds and to dilute liquid compounds to provide for
proper dosage. Solution tanks should be covered to
minimize evaporation. The mixing and dilution tanks
should be sized to provide sufficient feed solution for
several days of operation. The tanks shall be made of
materials that will withstand the corrosive nature of
the solutions. Refer to Section 370.560.
(Source: Added at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.1022 Ultraviolet Disinfection>>
Because operating data and experience with this process is not well
established, expected performance of the ultraviolet disinfection units
shall be based upon either experience at similar full scale installations
or thoroughly documented prototype testing with the particular wastewater.
Use of this process should be limited to high quality effluent having at
least 65% ultraviolet radiation transmittance at 254 nanometers wave length
and BOD and suspended solids concentrations no greater than 30 mg/l at any
time. Projects will be evaluated by the Agency on the basis of the factors
set out in Section 370.530(b).
(Source: Added at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.1030 Chlorine Gas Supply (Repealed)>>
(Source: Repealed at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.1040 Piping and Connections (Repealed)>>
(Source: Repealed at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.1050 Housing (Repealed)>>
(Source: Repealed at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.1060 Respiratory Protection Equipment (Repealed)>>
(Source: Repealed at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.1070 Application of Chlorine (Repealed)>>
(Source: Repealed at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.1080 Sampling and Testing>>
a) Facilities shall be included for collecting samples, as monitoring
requirements warrant, of the disinfected effluent.
b) Where chlorine disinfection is used, equipment shall be provided
for measuring chlorine residual using accepted test procedures.
c) Where required by the Agency, equipment shall also be provided for
measuring fecal coliform using accepted test procedures.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
SUBPART K: TERTIARY FILTRATION
<BSection 370.1100 Applicability>>
Various types of tertiary filters may be used to polish effluents of
secondary treatment plants.
<BSection 370.1110 Type>>
a) Granular media filtration is considered to include the following
type units:
1) High rate single, dual and multi-media of either the pressure
or gravity type with facilities for backwashing.
2) Low rate sand filters dosed intermittently or periodically.
b) Low rate filtration is generally limited in use to small
installations.
c) For miscellaneous considerations, refer to Section 370.203(j).
<BSection 370.1120 High Rate Filtration>>
a) Design Considerations
Care should be given in the selection of pumping equipment ahead
of filter units to minimize shearing of flow particles.
Consideration should be given in the plant design to providing
flow-equalization facilities to moderate filter influent quality
and quantity.
b) Pretreatment
A positive method shall be provided to control the suspended
solids loading to the filters. Equipment for the feeding of
chemical coagulant aids prior to secondary settling shall be
provided unless other equally effective means of suspended solids
control are used.
c) Multiple Units
Multiple units shall be provided. At least three units should be
provided. Units shall be capable of independent operation and
maintenance.
d) Filtration Rates
The peak hourly flow rate applied to the filter shall not exceed 5
gpm/sq. ft. of filter area, computed with one unit out of service.
1) Rate Controls
Controls shall be provided which allow adjustment and control
of the rate of flow to each filter unit.
2) Flow Measurement
The flow to each filter shall be monitored by indicating
equipment.
e) Accessibility and Maintenance
Each filter unit shall be designed and installed so that there is
ready and convenient access to all components and the media
surface for inspection and maintenance without taking other units
out of service.
f) Housing
Housing of filter units shall be provided. The housing shall be
constructed of suitable corrosion-resistant materials. All
controls shall be enclosed, and the structure housing the filter,
controls and equipment shall be provided with heating and
ventilation adequate to minimize problems with excess humidity.
g) Construction Details
1) Underdrains
The underdrain system shall be designed for uniform
distribution of flow of backwash water (and air, if
provided) without danger of clogging from solids in the
backwash water. A positive means of pressure relief shall
be provided for the underdrain system to prevent structural
damage by excessive backwash pressures. The selection of the
underdrain system shall be based on demonstrated satisfactory
field experience under similar conditions.
2) Media
The selection of proper media sizes and types depends upon
the filtration rate selected, the type of treatment provided
the influent to the filter, filter configuration, and
effluent quality objectives. In dual or multi-media filters,
media size and type selection must consider compatibility
among media. Media shall be selected and provided to meet
specific conditions and treatment requirements relative to
the project under consideration. The selection and sizing of
the media shall be based on demonstrated satisfactory field
experience under similar conditions. All media shall have a
uniformity coefficient of 1.7 or less. The uniformity
coefficient, effective size, depth and type of media shall be
set forth in the specification.
3) Appurtenances
The design of the filter appurtenances shall be based on
demonstrated satisfactory field experience under similar
conditions. The filters shall be equipped with the
following:
A) Wash water troughs.
B) Surface wash, air scouring equipment or mechanical
agitation designed to adequately remove entrapped solids
from the media.
C) Equipment for measuring filter head loss.
D) Filter influent and effluent sampling points.
Also refer to subsections (h)(2), (h)(4) and (i) below.
h) Backwash
1) Rate and Duration
The backwash rate shall be adequate to fluidize and expand
each media layer a minimum of 20 percent based on the media
selected. Minimum and maximum backwash rates shall be based
on demonstrated satisfactory field experience under similar
conditions. The design shall provide for a minimum backwash
period of 10 minutes. Excessive backwash rates may cause
washout of the filter media.
2) Control and Flow Measurement
A positive means of shutting off flow to a filter shall be
provided. Controls shall be provided which permit adjustment
of both the backwash rate and the backwash period. Flow
measurement of the backwash flow rate shall be provided. A
staff gauge or wall mounted scale to allow use of the rise
rate for flow measurement may be used.
3) Clearwell
A clearwell or other plant tankage isolated from unfiltered
flows shall be provided as a source of backwash water.
Filtered plant effluent shall be used as backwash water.
The volume of storage provided shall be sufficient to allow
sequential backwashing of at least 2 filter units at the
design backwash rate.
4) Chlorination of Filter Backwash
Provision shall be made for periodic chlorination of filter
backwash water (or filter influent) to control slime growths.
The flows from the cleaning of the filters shall be returned
to the head of the plant. Refer to subsection (h)(6)(A)
below.
5) Backwash Pumps
Where used, backwash pumps shall be provided in multiple
units, designed for independent operation and maintenance.
Pumps shall be sized in accordance with subsection (h)(1)
above to provide the required backwash rate with one unit out
of service and should be of equal size. The total dynamic
head of the pump shall be limited to that needed for the
application so that undue stress of the underdrain system
will not occur. Refer to subsection (g)(1) above.
6) Mudwell
A mudwell or other plant tankage shall be provided to hold
backwash water from the filters. The volume provided shall
be sufficient to hold the water generated by the backwashing
of two filter units including the water in and above the
filter media prior to filtration. Refer to subsection (h)(1)
above. Filter backwash shall be returned to process or
otherwise treated to insure compliance with applicable
standards.
A) Return Rate
The rate of return of filter backwash to the treatment
units shall not exceed 15 percent of the design average
flow to the treatment units. Refer to subsection (j)(1)
below and Section 370.520(g).
B) Mudwell Return Pumps
Backwash return pumps, where used, shall be provided in
multiple units designed for independent operation and
maintenance. The units shall be sized to provide the
required pumping rate with the largest unit out of
service. Refer to subsection (h)(6)(A) above.
i) Control Panel
Automatic controls shall be provided, with a manual override on
the control panel for operating equipment, including each
individual valve essential to the filter operation.
j) Miscellaneous Considerations
1) Return Backwash Loadings
The return of backwash water and solids will result in
increases in the hydraulic and suspended solids loads to the
preceding treatment units. Design of these units shall take
into account the increased loads.
2) Oil and Grease
Filters at treatment plants treating wastewaters containing
above normal concentrations of greases or similar materials
should be of the gravity type. Facilities should be
considered for the periodic addition of chemicals to remove
greases in such cases.
3) Proprietary Equipment
Proprietary equipment not conforming to the requirements of
this section will be evaluated on a case-by-case basis in
accordance with Section 370.520(b).
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.1130 Low Rate Intermittent or Periodically Dosed Sand Filters>>
a) Applicability
1) Intermittent sand filters may be used to polish secondary
effluents. The process removes residual suspended solids and
soluble biochemical oxygen demand and converts ammonia to
nitrate. (See Section 370.1210(b).)
2) Cold weather operational problems may preclude the use of
this process unless the influent temperature to the filter is
adequate to allow efficient filter operation necessary to
meet the applicable effluent standards.
3) Because of manual labor necessary to clean, maintain and
replace sand on the filters, the application is usually
limited to small waste treatment plants.
b) Design Criteria
The criteria of Section 370.940(b), (c), and (f)(3), are generally
applicable to intermittent sand filters used as tertiary
filtration units.
1) Dosing Volumes
The dosing facilities shall be sized to provide for a 12-hour
dosing cycle for each bed.
2) Siphon or Pump Capacity
Siphons (at minimum head) or pumps shall have a discharge
capacity at least 100 percent in excess of the maximum rate
of inflow to the dosing tank, including recirculation, and at
average head, at least 90 gallons per minute per 1,000 square
feet being dosed.
3) Recirculation
Provision for recirculation of filter effluent may be
included to improve process flexibility.
A) Rate
A recirculation rate of up to 100% of design average
flow to the filter may be provided.
B) Variability
Capability for varying the recirculation rate shall be
provided.
4) Loading Rates
The hydraulic load of secondary wastewater applied to
supplemental intermittent sand filters shall not exceed 15
gallons per day (gpd)/sq. ft. More conservative application
rates should be provided for low quality filter influents.
Refer to subsection (d)(3) below.
c) Construction Details
The criteria of Section 370.940(g) are generally applicable to
tertiary intermittent sand filters. Also, refer to subsection
(d).
d) Special Design Considerations in Lagoon Systems
1) General
Low rate sand filter systems that are intermittently or
periodically dosed may be used to reduce suspended solids
from multicell aerated or nonaerated sewage lagoon treatment
plants.
2) Cold Weather Design
Lagoons which have sand filters shall be designed to provide
storage of flows received during cold weather when the filter
is expected to be inoperable.
3) Hydraulic Loading
A) The filter area design considerations must include the
following:
i) The total annual flow volume to be treated (Section
370.520(c)(1)) including wet weather flows if the
lagoons are to be used for wet weather storage.
ii) The effective net days annually for filter
operation excluding cold weather shut-down and
filter maintenance time.
iii) Lagoon effluent quality.
iv) Extent and reliability of flow data from the sewer
system.
B) Where sewer system conditions are not favorable or
industrial waste loadings are expected to increase algae
blooms, the loading rate should be limited to 10
gal./ft.(2)/day.
4) Dosing Considerations
A) Methods of Operation
The design should include allowance for periodic dosing
of varied volumes onto the filter while the filter
discharge is shut off, then to be followed by a
filtration period to completely empty the filter at a
controlled rate.
B) Depth
The filter shall be designed for flexibility of dosing
depth from 6 inches to 2 feet.
C) Valving, Piping, Flow Measurement
i) The filter shall be provided with valving to allow
shutting off and controlling rate of flow both onto
and from the filter. A flow measurement weir or
flume shall be provided both on the inlet and
outlet of the filter for operator control of the
dosing and filtration rates under the falling head
conditions.
ii) The outlet valving, piping and flow measurement
shall be designed to allow complete drainage of the
filter underdrains at the end of the filter cycle
to insure aerobic conditions in the filter during
the rest period.
D) Dosing Inlet Structures
The dosing inlet structures shall be designed to
dissipate inlet velocity and prevent sand scouring
during the dosing period at the high dose rates. The
inlet structures should be arranged to not interfere
with maintenance of the sand surface.
5) Filter Containment Structure
The filter containment may be of vertical concrete walls on
three sides (refer to subsection (d)(6) below) or sloped
earthen berms with impervious lining, constructed to insure
that no ground surface runoff or silts get onto the sand
surface. A freeboard of 1 foot above the maximum design
dosing depth should be provided.
6) Access Ramps
The filter should be designed with a ramp on one end sloped
and surfaced for access to the edge of the bed by wheeled
vehicle to facilitate removing and replacement of sand. For
larger filters, concrete tracks at the level of the sand
surface may be desirable to reduce distance sand must be
handled.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
SUBPART L: NUTRIENT REMOVAL
<BSection 370.1200 Phosphorus Removal by Chemical Treatment>>
a) General
1) Method
Addition of lime or the salts of aluminum or iron may be used
for the chemical removal of soluble phosphorus. The
phosphorus reacts with the calcium, aluminum or iron ions to
form insoluble compounds. These insoluble compounds may be
flocculated with or without the addition of a coagulant aid
such as a polyelectrolyte to facilitate separation by
sedimentation.
2) Design Basis
A) Preliminary Testing
Laboratory, pilot or full-scale trial of various
chemical feed systems and treatment processes are
recommended to determine the achievable performance
level, cost-effective design criteria, and ranges of
required chemical dosages.
B) System Flexibility
Systems shall be designed with sufficient flexibility to
allow for several operational adjustments in chemical
feed location, chemical feed rates, and for feeding
alternate chemical compounds.
b) Process Requirements
1) Dosage
The required chemical dosage shall include the amount needed
to react with the phosphorus in the wastewater, the amount
required to drive the chemical reaction to the desired state
of completion, and the amount required due to inefficiencies
in mixing or dispersion. Excessive chemical dosage should be
avoided.
2) Chemical Selection
A) The choice of lime or the salts of aluminum or iron
should be based on the wastewater characteristics and
the economics of the total system.
B) When lime is used it may be necessary to neutralize the
high pH prior to subsequent treatment in secondary
biological systems or prior to discharge in those flow
schemes where lime treatment is the final step in the
treatment process.
3) Chemical Feed Points
Selection of chemical feed points shall include consideration
of the chemicals used in the process, necessary reaction
times between chemical and polyelectrolyte additions, and the
wastewater treatment processes and components utilized.
Considerable flexibility in feed location should be provided,
and multiple feed points are recommended.
4) Flash Mixing
Each chemical must be mixed rapidly and uniformly with the
flow stream. Where separate mixing basins are provided, they
should be equipped with mechanical mixing devices. The
detention period should be at least 30 seconds.
5) Flocculation
The particle size of the precipitate formed by chemical
treatment may be very small. Consideration should be given
in the process design to the addition of synthetic
polyelectrolytes to aid settling. The flocculation equipment
should be adjustable in order to obtain optimum floc growth,
control deposition of solids, and prevent floc destruction.
6) Liquid - Solids Separation
A) The velocity through pipes or conduits from flocculation
basins to settling basins should not exceed 1,5 feet per
second in order to minimize floc destruction. Entrance
works to settling basins should also be designed to
minimize floc shear.
B) Settling basin design shall be accordance with criteria
outlined in Subpart G. For design of the sludge
handling system, special consideration should be given
to the type and volume of sludge generated in the
phosphorus removal process.
7) Filtration
Effluent filtration shall be considered where effluent
phosphorus concentrations of less than 1 mg/1 must be
achieved.
c) Feed Systems
1) Location
A) All liquid chemical mixing and feed installations should
be installed on corrosion-resistant pedestals and
elevated above the highest liquid level anticipated
during emergency conditions. Refer to Section
370.147(b)(2)(A).
B) Lime feed equipment should be located so as to minimize
the length of slurry conduits. All slurry conduits
shall be accessible for cleaning.
2) Liquid Chemical Feed Pumps
A) Liquid chemical feed pumps should be of the positive
displacement type with variable feed rate. Pumps shall
be selected to feed the full range of chemical
quantities required for the phosphorus mass loading
conditions anticipated with the largest unit out of
service.
B) Screens and valves shall be provided on the chemical
feed pump suction lines.
C) An air break or anti-siphon device shall be provided
where the chemical solution stream discharges to the
transport water stream to prevent an induction effect
resulting in overfeed.
D) Consideration shall be given to providing pacing
equipment to optimize chemical feed rates.
3) Dry Chemical Feed System
A) Each dry chemical feeder shall be equipped with a
dissolver which is capable of providing a minimum
5-minute retention at the maximum feed rate.
B) Polyelectrolyte feed installations should be equipped
with two solution vessels and transfer piping for
solution make-up and daily operation.
C) Make-up tanks shall be provided with an eductor funnel
or other appropriate arrangement for wetting the polymer
during the preparation of the stock feed solution.
Adequate mixing should be provided by a large-diameter
low-speed mixer.
d) Storage Facilities
1) Size
Storage facilities shall be sufficient to insure that an
adequate supply of the chemical is available at all times.
Exact size required will depend on size of shipment, length
of delivery time, and process requirements. Storage for a
minimum of a 10-day supply should be provided.
2) Location
A) The liquid chemical storage tanks and tank fill
connections shall be located within a containment
structure having a capacity exceeding the total volume
of all storage vessels. Valves on discharge lines shall
be located adjacent to the storage tank and within the
containment structure.
B) Auxiliary facilities, including pumps and controls,
within the containment area shall be located above the
highest anticipated liquid level. Containment areas
shall be sloped to a sump area and shall not contain
floor drains.
C) Bag storage should be located near the solution make-up
point to avoid unnecessary transportation and
housekeeping problems.
3) Accessories
A) Platforms, stairways, and railings should be provided as
necessary to afford convenient and safe access to all
filling connections, storage tank entries, and measuring
devices.
B) Storage tanks shall have reasonable access provided to
facilitate cleaning.
e) Other Requirements
1) Materials All chemical feed equipment and storage facilities
shall be constructed of materials resistant to chemical
attack by all chemicals normally used for phosphorus
treatment.
2) Temperature, Humidity and Dust Control
Precautions shall be taken to prevent chemical storage tanks
and feed lines from reaching temperatures likely to result in
freezing or chemical crystallization at the concentrations
employed. Enclosure heating or insulation may be required.
Consideration must be given to temperature, humidity and dust
control in all chemical feed room areas.
3) Cleaning
Consideration shall be given to the accessibility of piping.
Piping should be installed with plugged wyes, tees or crosses
at changes in direction to facilitate cleaning.
4) Drains and Drawoff
Above-bottom drawoff from chemical storage or feed tanks
shall be provided to avoid withdrawal of settled solids into
the feed system. A bottom drain shall also be installed for
periodic removal of accumulated settled solids.
f) Hazardous Chemical Handling
The requirements of Section 370.147(b), Hazardous Chemical
Handling, shall be met.
g) Sludge Handling
1) General
Consideration shall be given to the type and additional
capacity of the sludge handling facilities needed when
chemicals are added.
2) Dewatering
Design of dewatering systems should be based, where possible,
on an analysis of the characteristics of the sludge to be
handled. Consideration should be given to the ease of
operation, effect of recycle streams generated, production
rate, moisture content, dewaterability, final disposal, and
operating cost.
<BSection 370.1210 Ammonia Control>>
a) General
Ammonia control can be accomplished by physical, chemical,
biological and ion-exchange techniques. These criteria contain
design standards for a limited number of biological types and
configurations of ammonia control systems. Other types and
configuration of systems will be evaluated in accordance with
Section 370.520(b).
1) Process Selection
A) Biological systems, normally used to accomplish
secondary levels of treatment, may be adapted to
function as nitrification systems. In applications of
the fixed growth processes staged biological treatment
is normally provided. The single stage activated sludge
process has been found to be reliable for nitrification
and is more commonly used than the two-stage activated
sludge process.
B) Because operating data and experience for the fixed
growth processes for nitrification are not well
established, expected performance in all cases shall be
based upon experience at similar full scale
installations or thoroughly documented prototype testing
with the particular wastewater. The design shall
provide the necessary flexibility to perform
satisfactorily within the range of expected waste
characteristics and temperatures.
2) Alkalinity and pH Control
Biological utilization of ammonia to produce nitrates is
consumptive of available alkalinity in the ratio of 7.14
pounds alkalinity (as CaCO[3]) per pound of ammonia nitrogen
(as N) oxidized. The determination of the need for added
alkalinity must be calculated and included in the basis of
design to be submitted with the plan documents for Agency
approval. The following factors shall be taken into account
in determining the amount of alkalinity to be added:
A) The available alkalinity in the raw wastewater and any
sidestreams;
B) The total ammonia load (including sidestreams such as
flows from digesters and sludge handling facilities)
imposed on the process;
C) The alkalinity needed to maintain pH levels in the range
of 7.2 to 8.4.
3) Load Equalization
Load equalization shall be considered to limit peak loadings
of ammonia from plant sidestreams or slug sources on the
sewer system. For the fixed growth biological nitrification
processes, the ammonia loading peaks shall be limited to 150%
of the design average ammonia loading value.
b) Intermittent Sand Filters
Intermittent sand filters, used in conjunction with various
primary and secondary treatment systems, may be considered for use
as a biological process to convert ammonia to nitrate.
1) Construction Details
The construction details are generally as described in
Section 370.940(g).
2) Loading Criteria
A) Following Primary Treatment
The design loading criteria following primary treatment
is described in Section 370.940(e), (f) and (h) except
that reduced organic loadings should be considered to
insure meeting effluent ammonia limitations.
B) Following Secondary Treatment
The design loading criteria following secondary
treatment is described in Section 370.1130(b)(4) and
(d)(3).
c) Suspended Growth Systems
1) Applicability
Suspended growth nitrifying systems may be designed as a
single stage process with combined carboneous BOD removal and
nitrogenous oxygen demand reductions or as the second stage
of a two-stage process following a first stage activated
sludge process or other types of biological treatment such as
trickling filters.
2) Design Requirements
A) Aeration and Mixing
For nitrification, the oxygen requirement for oxidizing
ammonia must be added to the requirement for
carbonaceous BOD removal. The nitrogen oxygen demand
shall be taken as 4.6 times the peak hourly ammonia (as
N) content of the influent. In addition, the oxygen
demands due to sidestream flows (digestion and sludge
handling facilities and the like) must be considered due
to the high concentrations of BOD and ammonia associated
with such flows. Sufficient aeration and mixing
capability shall be provided to maintain a sludge age of
up to 20 days and a dissolved oxygen concentration in
the aeration tank of at least 2 mg/l.
B) Power
Careful consideration should be given to maximizing
oxygen utilization per unit of power input. Unless flow
equalization is provided, the aeration system should be
designed to match the peak hourly load variation while
economizing on power input.
C) Temperature
Careful consideration shall be given in the design and
selection of aeration and mixing equipment to minimize
heat losses and to maintain sewage temperatures of at
least 50 F in cold weather.
D) Chemical Feed
Where the ratio of ammonia to available alkalinity in
the wastewater requires its use, chemical feed equipment
shall be provided to maintain adequate alkalinity and a
pH level between 7.2 and 8.4.
3) Single Stage Activated Sludge
In addition to the requirements of Section 370.920, the
following criteria shall govern the design:
A) Organic Loading Organic loading shall not exceed 15
lbs/day of BOD[5] per 1,000 cu.ft. of available tank
volume.
B) Detention Time
The hydraulic detention time shall be a minimum of 8
hours based on the plant design average flow as
determined by Section 370.520(c).
4) Activated Sludge Nitrifying Stage Following Secondary
Treatment
The following subsections set out criteria in addition to the
requirements of Section 370.920 for the activated sludge
nitrifying stage following a first stage activated sludge or
fixed growth process used for carbonaceous BOD removal.
A) Organic Loading
BOD[5] concentration shall be limited to 20-50 mg/1.
B) Detention Time
The hydraulic detention time shall be a minimum of 6
hours based on the plant design average flow as
determined by Section 370.520(c).
C) Special Design Requirement
The following requirements in addition to subsection
(c)(3) above, shall be provided:
i) Bypass around the first stage process to allow
discharge of raw or primary settled sewage to the
second stage aeration tank as needed as a carbon
source for control of the nitrification process.
ii) Careful consideration shall be given in the design
and selection of covers and ventilation or aeration
and mixing equipment to minimize heat losses in the
first stage process and maintain sewage
temperatures of at least 50 F in cold weather.
d) Fixed Growth Systems
1) Applicability
Nitrifying fixed growth systems may be used following
activated sludge and fixed growth systems used for
carbonaceous BOD removal.
2) Design Requirements
A) Peak Loadings
In addition to the requirements of Section 370.900, the
design of fixed growth systems shall take into account
the peak hourly ammonia content of the influent. The
design shall provide for ammonia load equalization in
accordance with subsection (a)(3) above.
B) Temperature
Adequate cover or housing of the nitrification units
shall be provided and preceding systems shall be
designed or upgraded to minimize heat losses to maintain
sewage temperatures of at least 50 F in cold weather.
C) Ventilation for Process Air Requirements
Adequate ventilation shall be provided to satisfy the
oxygen demand of the process. Refer to Section
370.900(e)(5).
D) Chemical Feed
Chemical feed equipment shall be provided to maintain
adequate alkalinity concentrations and a pH level
between 7.2 and 8.4 where the ratio of ammonia to
available alkalinity in the wastewater requires its use.
E) Post-Process Settling
Settling tanks following nitrifying fixed growth systems
shall be provided and designed in accordance with
Subpart G. A single unit will be allowed if the
applicable BOD and suspended solids effluent limitations
can be met and other serious operational problems will
not occur when the clarifier is temporarily out of
service.
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.APPENDIX A Table No. 1 - Resident Occupancy Criteria>>
<PResidence Type>> <PNumber of Persons>>
Efficiency or Studio Apartment 1
1 Bedroom Apartment 1.5
2 Bedroom Apartment 3
3 Bedroom Apartment 3
Single Family Dwelling 3.5
Mobile Home 2.25
<BSection 370.APPENDIX B Table No. 2 - Commonly Used Quantities of Sewage
Flows From Miscellaneous Type Facilities>>
Gallons Per Person
Per Day
(Unless otherwise
<PType of Establishment>> <P noted) >>
Airports (per passenger) 5
Bathhouses and swimming pools 10
Camps:
Campground with central comfort stations 35
With flush toilets, no showers 25
Construction camps (semi-permanent) 50
Day camps (no meals served) 15
Resort camps (night and day) with
limited plumbing 50
Luxury camps 100
Cottages and small dwellings with
seasonal occupancy 75
Country clubs (per resident member) 100
Country clubs (per non-resident member
present) 25
Dwellings:
Boarding houses 50
(additional for non-resident boarders) 10
Rooming houses 40
Factories (gallons per person, per shift,
exclusive of industrial wastes) 35
Hospitals (per bed space) 250
Hotels with laundry (2 persons
per room) per room 150
Institutions other than hospitals including
Nursing Homes (per bed space) 125
Laundries-self service (gallons per wash) 30
Motels (per bed space) with laundry 50
Picnic parks (toilet wastes only per
park user) 5
Picnic parks with bathouses, showers and
flush toilets (per park user) 10
Restaurants (toilet and kitchen wastes
per patron) 10
Restaurants (kitchen wastes per meal served) 3
Restaurants (additional for bars and cocktail
lounges) 2
Schools:
Boarding 100
Day, without gyms, cafeterias or showers 15
Day, with gyms, cafeterias and showers 25
Day, with cafeterias, but without gyms
or showers 20
Service stations (per vehicle served) 5
Swimming pools and bathouses 10
Theaters:
Movie (per auditorium seat) 5
Drive-in (per car space) 10
Travel trailer parks without individual
water and sewer hook-ups (per space) 50
Travel trailer parks with individual
water and sewer hook-ups (per space) 100
Workers:
Offices, schools and business
establishments (per shift) 15
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.APPENDIX C Table No. 3 - Air Test Table for Sanitary Sewer
Leakage Testing*>>
SPECIFICATION TIME (MIN:SEC) REQUIRED FOR PRESSURE DROP
FROM 3 1/2 TO 2 1/2 PSIG WHEN TESTING ONE PIPE DIAMETER ONLY
Length of
Sewer Pipe PIPE DIAMETER, INCHES
<PIn Feet>> <P4>> <P6>> <P8>> <P10>> <P12>> <P15>> <P18>> <P21>> <P24>>
25 0:04 0:10 0:28 0:28 0:40 1:02 1:29 2:01 2:38
50 0:09 0:20 0:35 0:55 1:19 2:04 2:58 4:03 5:17
75 0:13 0:30 0:53 1:23 1:59 3:06 4:27 6:04 7:55
100 0:18 0:40 1:10 1:50 2:38 4:08 5:56 8:05 10:34
125 0:22 0:50 1:28 2:18 3:18 5:09 7:26 9:55 11:20
150 0:26 0:59 1:46 2:45 3:58 6:11 8:30
175 0:31 1:09 2:03 3:13 4:37 7:05
200 0:35 1:19 2:21 3:40 5:17 12:06
225 0:40 1:29 2:38 4:08 5:40 10:25 13:36
250 0:44 1:39 2:56 4:35 8:31 11:35 15:07
275 0:48 1:49 3:14 4:43 9:21 12:44 16:38
300 0:53 1:59 3:31 10:12 13:53 18:09
350 1:02 2:19 3:47 8:16 11:54 16:12 21:10
400 1:10 2:38 6:03 9:27 13:36 18:31 24:12
450 1:19 2:50 6:48 10:38 15:19 20:50 27:13
500 1:28 5:14 7:34 11:49 17:01 23:09 30:14
*From Standard Specifications for Water and Sewer Main Construction in
Illinois, Fourth Edition, May, 1986. (Copies may be obtained from Illinois
Society of Professional Engineers, Springfield, Illinois 62704.)
(Source: Amended at 21 Ill. Reg. 12444, effective August 28, 1997)
<BSection 370.APPENDIX D Figure No. 1 - Design of Sewers - Ratio of Peak
Flow to Daily Average Flow>>
<BSection 370.APPENDIX E Figure No. 2 - Primary Settling>>
<BSection 370.APPENDIX F Figure No. 3 - B.O.D. Removal Single Stage
Trickling Filter Units Including Post Settling - No Recirculation Included>>
<BSection 370.APPENDIX G Figure No. 4 - Break Tank Sketch for Potable Water
Supply Protection>>
<BSection 370.APPENDIX H Old Section Numbers Referenced (Repealed)>>
(Source: Repealed at 21 Ill. Reg. 12444, effective August 28, 1997)