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22009
September 23,
2009
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Marie E. Tipsord
Hearing Officer
cThQ,V
Illinois Pollution
Control
Board
100
West Randolph Suite
11-500
Chicago, Illinois
60601
Re:
R2008-009,
In The Matter of: Water
Quality
Standards
and Effluent
Limitations
for
the
Chicago Area Waterway
System and the
Lower Des
Plaines River: Proposed
Amendments
to
35
III. Adm.
Code 301,
302, 303 and 304
Dear
Madam Hearing Officer,
This letter
serves as ENVIRON’s
response
on
behalf
of Stepan
Company to Board Member
Dr.
Shundar
Lin’s
question
at the August 13
hearing regarding the
dosage of chlorine
necessary
to
meet the proposed
effluent bacteria standards
at
end of pipe.
The dosage
of
chlorine
determined
by ENVIRON was 70
mg Cl
2!L of wastewater.
In addition
to providing
the exact
chlorine
dose, the
following
comments summarize
ENVIRON’s
general approach
to chlorine
disinfection.
First, the
concept
of chlorine consumption
must be
considered. In typical
wastewater,
there
are
four sources
of chlorine or
hypochlorite consumption,
three of
which compete with
chlorine
availability
for disinfection.
Consequently,
adequate chlorine
must be
added
to satisfy these
sources
of chlorine
consumption and provide
sufficient residual
chlorine to
kill fecal coliform.
These sources
are:
1.
Ammonia-N,
which reacts
with chlorine to form
nitrogen
gas;
2. Oxidizable
organics,
such
as phenols, which
are converted to simpler
organic
constituents and, hopefully,
not converted into
chiorinated—organics;
3.
Oxidizable
inorganics,
such as cyanides, or
sulfides, which are
reduced
to
lower state compounds;
and,
4.
Biological organisms,
including fecal coliforms,
which
are killed in the
presence of sufficient
residual chlorine.
Upon
that
foundation, the calculation
of the chlorine
dose was arrived
in the following
manner.
Stepan’s
wastewater averages
about 2.1 mg/L
of
ammonia-N,
which is a chlorine
consumer,
and
it can range
as high as 3.0 mg/L
of ammonia-N. This will
result
in “breakpoint
chlorination”
to convert
the
ammonia
to
harmless nitrogen gas,
requiring
about
15:1 Cl2 to N (See
Design
Manual
Municipal Wastewater
Disinfection.
Cincinnati: US
EPA Office of
Research and
Development,
1986.
Print).
The theoretical
dosage of chlorine
to convert ammonia
to nitrogen
gas is
47.25 mg/L
[2.1 x 15 x
1.5 (roughly ratio
of maximum to average
ammonia-N
concentration)].
This
leaves approximately
20 mg of CI2
!L
of
wastewater
for disinfection.
From
the
Design of Municipal
Wastewater Treatment
Plants, WEF
Manual of Practice
No.
8 / ASCE
Manual
and Report on
Engineering Practice
No. 76. Alexandria,
VA: Water
Environment
Federation,
1991.
Print, Chapter 14,
Table 14.1: Typical
Chlorine Dosages,
the required
dosage
of chlorine
for disinfecting
municipal
activated sludge
effluent can
be up to 9
mg!L.
Because
of
201
Summit View Drive, Suite 300,
Brentwood, TN 37027
www.environcorp.com
Tel: +1
615.377.4775
Fax: +1 615.377.4976
Marie
E Tipsord
-2-
September
23,
2009
the
industrial
nature of
the Stepan wastewater,
there will
most
likely be constituents
that exert
an
additional chlorine
demand (residual
organics surfactants
etc)
Because
this
additional
chlorine
demand
has not been
quantified, a 100%
safety factor
was applied, rounding
the
required
dosage of chlorine
for disinfection
to
20
mgIL. Adding
that amount
of chlorine to
the
amount necessary
to address the presence
of ammonia-N,
which
consumes chlorine,
and
rounding off the
calculations, we
arrived
at 70 mg of CI
2
IL
of wastewater
to achieve
disinfection.
This
dosage of
chlorine is also what
was implicitly reflected
in our cost
calculations,
as the
following calculations
demonstrate:
Design
Flow = 1,100,000
gal/day
The gallons of bleach
solution projected
for disinfection
= 235,883
gal/yr (see
Table
8
of Exhibit
321), which is roughly
646 gallons/day
[235,883/365].
The
bleach
solution is 12.5% bleach
(NaOCI),
so
the bleach/liter
of wastewater
is
approximately
73 mg of NaOCl/L
of wastewater
[646 gals/day
x 12.5%
NaOCl/1,100,646
(gallons
of wastewater plus bleach
solution
in a day)].
Using the molecular
weights
of sodium (Na), oxygen
(0) and
chlorine (Cl), the 73
mg
of NaOCl/L of wastewater
is equivalent
to 51 mg of 0C17
L
of wastewater
and
to 70 mg of Cl
2
/L
of wastewater.
Consequently,
the dosage
of approximately
70 mg of
Cl
2
/L
of wastewater
accounts for
the
presence of ammonia,
susceptible organics/inorganics,
and
a safe residual
for
disinfection
and
served
as the
basis
for our
cost
estimate.
Sincerely,
ENVIRON
International Corporation
Carl E.
Adams Jr., PhD,
PE
Principal