IEPA ATTACHMENT NO. 2-
United States
?
Office Of Water
Environmental Protection (4305)
Agency
EPA 823-B-96-007
June 1996
The Metals Translator:
Guidance For
Calculating A Total
Recoverable Permit Limit
From A Dissolved
Criterion
FORWARD
This document is the result of a successful collaborative effort between the United
States Environmental Protection Agency (USEPA), Electric Power Research Institute (EPRI),
and Utility Water Act Group (UWAG). Methods and procedures suggested in this guidance
are for the specific purpose of developing the metals translator in support of the dissolved
metals criteria and should not be interpreted to constitute a change in EPA regulatory policy
as to how metals should be measured for such regulatory purposes as compliance monitoring.
This document provides guidance to EPA, States, and Tribes on how best to
implement the Clean Water Act and EPA's regulations to use dissolved metal concentrations
for the application of metals
aquatic
life criteria and to calculate a total recoverable permit
limit from a dissolved criterion. It also provides guidance to the public and to the regulated
community on appropriate protocols that may be used in implementing EPA's regulations.
The document does not, however, substitute for EPA's regulations, nor is it a regulation itself.
Thus, it cannot impose legally-binding requirements on EPA, States, or the regulated
community, and may not apply to a particular situation based upon the circumstances. EPA
may change this guidance in the future, as appropriate.
This document will be revised to reflect ongoing peer reviews and technical advances
and to reflect the results of planned as well as ongoing studies in this technically challenging
area. Comments from users will be welcomed. Send comments to USEPA, Office of Science
and Technology, Standards and Applied Science Division (4305), 401 M Street SW,
Washington, DC 20460.
Tudor Davies, Director
Office of Science and Technology
ABSTRACT
On October 1, 1993, in recognition that the dissolved fraction is a better representation of the
biologically active portion of the metal than is the total or total recoverable fraction, the Office of
Water recommended that dissolved metal concentrations be used for the application of metals aquatic
life criteria and that State water quality standards for the protection of aquatic life (with the exception
of chronic mercury criterion) be based on dissolved metals. Consequently, with few exceptions, each
metal's total recoverable-based criterion must be multiplied by a
conversion factor
to obtain a dissolved
criterion that should not be exceeded in the water column. The Wasteload Allocations (WLA) or Total
Maximum Daily Loads (TMDLs) must then be translated into a total recoverable metals permit limit.
By regulation (40 CFR 122.45(c)), the permit limit, in most instances, must be expressed as
total recoverable metal. This regulation exists because chemical differences between the effluent
discharge and the receiving water body are expected to result in changes in the partitioning between
dissolved and adsorbed forms of metal. As we go from total recoverable to dissolved criteria, an
additional calculation called a
translator.
is required to answer the question "What fraction of metal in
the effluent will be dissolved in the receiving water?" Translators are not designed to consider
bioaccumulation of metals.
This technical guidance examines what is needed in order to develop a metals translator.
The
translator is the fraction of total recoverable metal in the downstream water that is dissolved;
that is,
the dissolved metal concentration divided by the total recoverable metal concentration. The translator
may take one of three forms. (1) It may be assumed to be equivalent to the criteria conversion factors.
(2) It may be developed directly as the ratio of dissolved to total recoverable metal. (3) Or it may be
developed through the use of a partition coefficient that is functionally related to the number of metal
binding sites on the adsorbent in the water column (i.e., concentrations of TSS, TOC, or humic
substances).
Appendix A illustrates how the translator is applied in deriving permit limits for metals for
single sites and as part of a TMDL for multiple sources. Appendix B presents some indications of site
specificity in translator values. Appendix C illustrates the process of calculating the translator.
Appendix D provides some detail of a statistical procedure to estimate sample size. Appendices E and
F present information on clean sampling and analytical techniques which the reader
may elect
to
follow. This material (E and F) is presented
only
to assist-the reader by providing more detailed
discussion rather than only providing literature citations; these procedures are
not
prescriptive.
ii
ACKNOWLEDGMENT
Many people have contributed long hours reviewing and editing the
many drafts of this document. The success of technical guidance documents,
such as this one, depends directly on the quality of such reviews and the quality
of the reviewers suggestions. As such, we thank the many reviewers for their
contributions. We wish to express our gratitude to the Coors Brewing
Company for making available a large and very complete data set for our use in
developing this technical guidance document; and to the City of Palo Alto,
Dept. of Public Works for permitting us to use the data they are collecting as
part of a NPDES Permit Application. The Cadmus Group, Inc. and EA
Engineering, Science and Technology, Inc also contributed to the success of
this document.
Development of this document has been a collaborative effort
between industry and the USEPA; it has been authored by Russell S.
Kinerson, Ph.D. (USEPA), Jack S. Mattice, Ph.D. (EPRI), and James
F. Stine (UWAG).
iii
TABLE OF CONTENTS
1.
INTRODUCTION
1
1.1
Considerations of Reasonable Potential
2
1.2.
Margin of Safety
2
1.3.
Converting from Total Recoverable to Dissolved Criteria
2
1.4.
Translating from a Dissolved Metal Ambient Water Quality Criterion to a Total
Recoverable Concentration in the Effluent
5
1.5.
Developing Translators
5
1.5.1. Direct
Measurement of the Translator
6
1.5.2. Calculating
the Translator Using the Partition Coefficient
6
1.5.3. The
Translator as a Rebuttable Presumption
7
1.6.
Applying Metals Translators
7
2.
UNDERSTANDING THE METALS TRANSLATOR
9
2.1.
Sorption-Desorption Theory
9
2.2.
The Partition Coefficient
9
2.2.1. Developing
Site Specific Partition Coefficients
10
3.
FIELD STUDY DESIGN
11
3.1. Sampling Schedule
11
3.1.1. Considerations
of Appropriate Design Flow Conditions for Metals 12
3.1.2. Frequency
and Duration of Sampling
12
3.2.
Sampling Locations
13
3.2.1. Collect
Samples at or Beyond the Edge of the Mixing
13
3.2.3. Collect
Samples from Effluent and Ambient Water and Combine in the
Laboratory
14
3.3.
Number of Samples
15
3.4
Parameters to Measure
16
3.5.
The Need for Caution in Sampling
16
4.
DATA GENERATION AND ANALYSIS
17
4.1.
Analytical Data Verification and Validation
17
4.2.
Evaluation of Censored Data Sets
17
4.3
Calculating the Translator Value
18
5.
SITE-SPECIFIC STUDY PLAN
20
5.1. Objective
20
5.2. Approach
20
5.3. Parameters
21
5.4.
Sampling Stations
21
5.5.
Sampling Schedule
22
5.6. Preparation
23
5.7
Sampling Procedure
24
5.8.
Field Protocol
25
5.9.
Data Analysis
26
iv
5.10.
?
Schedule ?
26
5.11.
?
State Approval
?
26
6.
BUILDING A SPREADSHEET MODEL
?
27
7. REFERENCES ?
29
APPENDIX A ?
31
APPENDIX B ?
40
APPENDIX C ?
42
APPENDIX D ?
51
APPENDIX E ?
52
APPENDIX F ?
58
Executive Summary
T
his guidance presents
procedures that may be used to
determine translator values that
more accurately reflect site specific conditions.
In this Executive Summary, steps to implement
the dissolved metals policy through
development and use of the translator are
presented.
Before beginning a translator study one
should make a
determination of reasonable
potential
with a translator of 1 (all the metal in
the effluent becomes dissolved in the receiving
water).. If the releases of metal from a
discharge do not pose a reasonable potential of
exceeding water quality criteria levels with the
largest possible translator, then a permit limit
does not have to be written for their release.
However, if a discharge has a water quality
based permit limit for a metal, and the State is
adopting standards based on dissolved metals,
then a translator study is needed.
In the toxicity tests to derive metal
criteria, some fraction of the metal was
dissolved and some fraction was bound to
particulate matter. Assuming that the dissolved
fraction more closely approximates the
biologically available fraction than does total
recoverable, conversion factors have been
calculated. The conversion factors are
predictions of how different the criteria would
be if they had been based on measurements of
the dissolved concentrations.
The translator is the fraction of total
recoverable metal in the downstream water that
is dissolved; fp C D/C
T.
It may be determined
directly by measurements of dissolved and total
recoverable metal concentrations in water
samples taken from the well mixed effluent and
receiving water (i.e.. at or below the edge of
the mixing zone).
EPA encourages that site
specific data be generated to develop site
specific translators.
If the translator is being developed to
show a functional relationship to environmental
properties such as TSS, pH, and salinity,
samples should be collected under an
appropriate range of conditions in order to
develop a statistically robust translator. If the
translator is not to be functionally related to
adsorbent concentrations, or other
environmental parameters, the study would
normally be designed to collect samples under
low flow conditions where TSS concentrations
are relatively constant. Either the directly
determined translator (the ratio of C
D/CT) or a
translator calculated by using a partition
coefficient (K
r
) may be used.
The most direct procedure for
determining a site-specific metal translator is
simply to determine f
p
by measuring C
T
and CD
and to develop the dissolved fraction as the
ratio C
D/CT
. The
translator
is calculated as the
geometric mean of the dissolved fractions.
A partition coefficient may be derived
as a function of TSS and other factors such as
pH, salinity, etc. The partition coefficient is
the ratio of the particulate-sorbed and dissolved
metal species multiplied by the adsorbent
concentration. Use of the partition coefficient
may provide advantages over the dissolved
fraction when using dynamic simulation for
Waste Load Allocation (WLA) or the Total
Maximum Daily Load (TMDL) calculations
and permit limit determinations because K
p
allows for greater mechanistic representation of
the effects that changing environmental
variables have on fp.
vi
1.?
INTRODUCTION
he U.S. Environmental
Protection Agency (EPA)
issued a policy memorandum
on October 1, 1993, entitled
Office of Water
Policy and Technical Guidance on
Interpretation and Implementation of Aquatic
Life Metals Criteria
("Metals Policy"). 1 The
Metals Policy states:
It is now the policy of the Office of Water that
the use of dissolved metal to set and measure
compliance with water quality standards is the
recommended approach, because dissolved
metal more closely approximates the
bioavailable fraction of metal in the water
column than does total recoverable metal.
The primary mechanism for toxicity to
organisms that live in the water column is by
adsorption to or uptake across the gills; this
physiological process requires metal to be in a
dissolved form. This is not to say that
particulate metal is nontoxic, only that
particulate metal appears to exhibit
substantially less toxicity than does dissolved
metal.' Dissolved metal is
operationally defined
as that which passes through a 0.45 i_tm or a
0.40 j.im filter and particulate metal is
operationally defined
as total recoverable metal
minus dissolved metal. Even at that, a part of
what is measured as dissolved is particulate
metal that is small enough to pass through the
filter, or that is adsorbed to or complexed with
organic colloids and ligands. Some or all of
this may be unavailable biologically.
The Metals Policy further states:
Until the scientific uncertainties are better-
The complete October I. 1993 memorandum
can be obtained from EPA's Office or Water Resource
Center (202) 260-7786 or the Office of Water Docket.
resolved, a range of different risk management
decisions can be justified. EPA recommends
that State water quality standards be based on
dissolved metal. EPA will also approve a State
risk management decision to adopt standards
based on total recoverable metal, if those
standards are otherwise approvable as a matter
of law.'
The adoption of the Metals Policy did
not change the Agency's position that the
existing total recoverable criteria published
under Section 304(a) of the Clean Water Act
continue to be scientifically defensible. When
developing and adopting its own standards, a
State, in making its risk management decision,
may wish to consider sediment, food chain
effects and other fate-related issues and decide
to adopt total recoverable or dissolved metals
criteria.
Because EPA's Section 304(a) criteria
are expressed as total recoverable metal, to
express the criteria as dissolved, application of
a conversion factor is necessary to account for
the particulate metal present in the laboratory
toxicity tests used to develop the total
recoverable criteria.
By regulation (40 CFR 122.45(c)), the
permit limit, in most instances, must be
expressed as total recoverable metal.' Because
chemical differences between the discharged
effluent and the receiving water are expected to
result in changes in the partitioning between
2
See Section 510. Federal Water Pollution
Control Act. Public Law 100-4. 33 U.S.C. 466 et seq.
For example. metals in the effluent of an
electroplating facility that adds lime and uses clarifiers
will be a combination of solids not removed by the
clarifiers and residual dissolved metals. When the effluent
from the clarifiers. usually with a high pH level. mixes
with receiving water with a si
gnificantly
lower pH level.
these solids instantly dissolve. • Measuring dissolved
metals in the effluent. in this case. would underestimate
the impact on the receivin
g water.
1
dissolved and adsorbed forms of metal, an
additional calculation using what is called a
translator
is required. This
translator
calculation answers the question "What fraction
of metal in the effluent will be dissolved in
receiying_water_bodf?" Translators are not
designed to consider bioaccumulation of
metals.
1.1?
Considerations of Reasonable
Potential
Water quality-based permit limitations
are imposed when a discharge presents a
reasonable potential to cause or contribute to a
violation of the applicable water quality
standard. . If the releases'f metal from a
facility are sufficiently low so as to pose no
reasonable potential of exceeding water quality
criteria levels, then a permit limit does not have
to be written for their release. If a facility has a
water quality based permit limit for a metal,
and the State is adopting standards based on
dissolved metals, then a translator is needed to
produce a permit limit expressed as total
recoverable metal. Of course, if the facility has
a technology based permit limit for the metal
and the limit is more stringent than a limitation
necessary to meet water quality standards, then
no translator is required or appropriate.
1.2.
?
Margin of Safety
TMDLs must ensure attainment of
applicable water quality standards, including all
numeric and narrative criteria. TMDLs include
waste load allocations (WLAs) for point
sources and load allocations (LAs) for nonpoint
sources, including natural background, such
that the sum of these allocations is not greater
than the loading capacity of the water for the
pollutant(s) addressed by the TMDL, minus the
sum of a specified margin of safety (MOS) and
any capacity reserved for future growth. The
MOS shall be sufficient to account for technical
uncertainties in establishing the TMDL and
shanescribe the manner in which the MOS is
determined and incorporated into the TMDL.
The MOS may be provided by leaving a portion
of the loading capacity unallocated or by using
conservative modeling assumptions to establish
WLAs and LAs. If a portion of the loading
capacity is left unallocated to provide a MOS,
the amount left unallocated shall be described.
If conservative modeling assumptions are relied
on to provide a MOS, the specific assumptions
providing the MOS shall be identified. For
example, a State may recommend using the 90
percentile translator value to address MOS
needs and account for variabliity of data and to
use the critical 10' and 90 th percentiles for
other variables such as hardness and TSS when
conducting steady-state modeling.
1.3.
?
Converting from Total Recoverable
to Dissolved Criteria
In the toxicity tests used to develop
metals criteria for aquatic life, some fraction of
the metal is dissolved and some fraction is
bound to particulate matter. When the toxicity
tests were originally conducted, metal
concentrations were expressed as total. Some
of the tests were repeated and some test
conditions were simulated, for the purpose of
determining the percent of total recoverable
metal that is dissolved. Working from the
premise that the dissolved fraction more closely
approximates the biolo g
ically available fraction
than does total recoverable, these
conversion
factors
have the effect of reducing the water
quality criteria concentrations. The conversion
factors are predictions of how different the
criteria would be if they had been based on
measurements of the dissolved concentrations
in all of the toxicity tests that were most
important in the derivation of the criteria.
Consequently each metal's total
recoverable criterion must be multiplied by a
conversion factor
to obtain a dissolved criterion
that should not be exceeded in the water
column. For example, the silver acute
conversion factor of 0.85 is a weighted average
and is used as a prediction of how much the
final acute value would change if dissolved had
been measured. At a hardness of 100 mg/L as
calcium carbonate (CaCO
3
)
,
the acute total
recoverable criterion is 4.06 p.g/L while the
dissolved silver criterion is 3.45 p.g/L.
For additional details on aquatic life
criteria for metals, the reader is referred to FR
60(86): 22229-22237.
Both freshwater (acute and chronic)
and saltwater (acute) conversion factors' are
presented (Tables 1 and 2); conversion factors
for saltwater chronic criteria are not currently
available. Where possible, these conversion
factors are given to three decimal places as they
are intermediate values in the calculation of
dissolved criteria. Most freshwater aquatic life
criteria are hardness-dependent' as are the
conversion factors for Cd and Pb. The values
shown in these tables are with a hardness of
100 mg/L. Conversion factors (CF) for any
hardness can be calculated using the following
equations:
Cadmium
Acute:
CF = 1.136672 - [In (hardness) (0.041838)]
Chronic:
CF = 1.101672 - [In (hardness) (0.041838)]
Lead
Acute and Chronic:
CF = 1.46203 - [In(hardness) (0.145712)]
Federal Register / Vol. 60, No.86 / 22229-
22237/Thursday, May 4. 1
.
995 / Rules and Regulations.
Water Quality Standards: Establishment of Numeric
Criteria for Priority Toxic Pollutants: States' Compliance--
Revision of Metals Criteria.
5
Although most of the freshwater aquatic life
criteria for metals are hardness dependent. those for
trivalent arsenic. trivalent chromium. mercury, aluminum.
iron. and selenium are not.
Table 1. Freshwater Criteria Conversion Factors for Dissolved Metals
Metal
Conversion Factors
Acute
Chronic
Arsenic
1.000
1.000
Cadmium
*
0.944
0.909
Chromium (III)
0.316
0.860
Chromium (VI)
0.982
0.962
Copper
0.960
0.960
Lead '
0.791
0.791
Mercury
0.85
N/A
Nickel
0.998
0.997
Silver
0.85
N/A
Zinc
0.978
0.986
Conversion factors fro Cd and Pb are hardness dependent. The valuse show
are with a hardness of 100 mg/L as calcium carbonate (CaCO3).
Table 2. Saltwater Criteria Conversion Factors for Dissolved Metals
Metal
Conversion Factors (Acute)
Arsenic
1.000
Cadmium
0.994
Chromium (111)
N/A
Chromium (IV)
0.993
Copper
0.83
Lead
0.95 I
Mercury
0.85
Nickel
0.990
Selenium
0.998
Silver
0.85
Zinc
0.946
The fractions of metals in dissolved and
particulate
phases are very dependent on water
4
chemistry. Because of the (typically) great
differences between chemical properties of
effluents, the chemical properties of receiving
waters, and the chemical properties of the
waters used in the toxicity tests, there is no
reason to expect that the conversion factors can
be used to estimate either the fraction of metal
that would be in the dissolved phase in the
receiving waters or the total recoverable metal
concentration in the effluent that would result
in a receiving water concentration not
exceeding a criterion concentration. Thus, a
translator is required to derive a total
recoverable permit limit from a dissolved
criterion'.
1.4. Translating from a Dissolved Metal
Ambient Water Quality Criterion to
a Total Recoverable Concentration
in the Effluent
As the effluent mixes with the
receiving water, the chemical properties of the
mixture will determine the fraction of the metal
that is dissolved and the fraction of the metal
that is in particulate form (typically adsorbed to
surfaces of other compounds). Many different
properties influence this dissolved to total
recoverable metal ratio. Important factors
include water temperature, pH, hardness,
concentrations of metal binding sites such as
concentrations of total suspended solids (TSS),
particulate organic carbon (POC), and
dissolved organic carbon (DOC), as well as
concentrations of other metals and organic
compounds that compete with the metal ions
for the binding sites. It is difficult to predict
the result of such complex chemistry. The
6
As a reasonable worst case, however, it may be
assumed that metal in the receiving environment would be
biologically available to the same extent as during toxicity
testing: and the conversion factors may be used as
translators if a site-specific translator is not developed. In
that case, the water quality criterion that already has been
multiplied by the conversion factor would be divided by
the conversion factor.
most straightforward approach is to analyze the
mixture to determine the dissolved and total
recoverable metal fractions. This ratio of
dissolved to total recoverable metal
concentrations can then be used to translate
from a dissolved concentration in the water
column downstream of the effluent discharge
(the criterion concentration) to the total
recoverable metal concentration in the effluent
that will not exceed that dissolved
concentration in the water column.
Appendix A presents an example that
summarizes the steps involved in applying the
' dissolved metals policy, using the translator, to
develop a permit limit.
1.5.?
Developing Translators
The purpose of this technical guidance
document is to present additional details
regarding development and application of the
metals translator to go from a dissolved metal
criterion to a total recoverable permit limit.
This chapter identifies different approaches that
may be used in developing site specific
translators. In the following chapters, we will
focus on designing and conducting field studies,
analytical chemistry procedures, data analysis,
and application of the metals translator to meet
mass balance requirements.
There is always a translator in going
from a dissolved criterion to a total recoverable
permit limit. The rebuttable presumption is
that the metal is dissolved to the same extent as
it was during criteria development. The default
translator value should be that the translator
equals the conversion factor. this represents a
reasonable worst case.
EPA encourages that site specific data
be generated to develop site specific partition
coefficients (translators), and use of translators
based on EPA's old data (as published in
USEPA, 1984 and presented in Table 3 below)
5
be phased out unless other data as suggested
below, have been generated that establish their
validity for the sites in question.
The guidance
released on October 1, 1993 identified three
methods of estimating the metals translator.
One of these was the use of the relationships
developed from the STORET data (USEPA,
1984). In the years between 1984 and 1993
there was general recognition that the
relationships had some inaccuracies due to
contaminated metals data and other factors.
However, limited comparisons of predictions
from these relationships with data generated
and analyzed with good QA/QC indicated
generally good agreement and some tendency
to be conservative. The stream data for lead
were reanalyzed and a better relationship was
developed. The parameters for these default
partition coefficient estimation equations are
presented in Table 3 where K
p
has units of L/kg
with TSS expressed as mg/L.
Table 3.
?
Calculation of Default Partition
Coefficients [K p
= Kpo • TSS
Lakes
Streams
Metal
K„
a
Kpo
a
Cu
2.85E+06
-0.9000
1.04E+06
-0.7436
Zn
3.34E+06
-0.6788
1.25E+06
-0.7038
Pb
2.0E+06
-0.5337
2.80E+06
-0.8
Cr(111
2.17E+06
-0.2662. 3.36E+06
-0.9304
Cd
3.52E+06
-0.9246
4.00E+06
-1.1307
N
i
2.21E+06
-0.7578
4.90E+05
-0.5719
site.specific conditions may render
these default parOfion
. cofficients, overly or
underly protective. Data presented in Appendix
B illustrate the variability that exists between
different sites in some values of the dissolved
metal fractions. Recent work by Sung (1995)
demonstrates that reliance on the relationships
in Table 3 does not always provide for
conservative estimates of the translator.
Similar conclusions have been arrived at with
data from rivers and streams in Washington.'
Therefore, it may be appropriate to develop a
dissolved to total recoverable ratio based on a
single sample
to
confirm that the partition
coefficient produces an estimate of the
translator that is either reasonably accurate or
conservative.
This guidance document presents
procedures that may be used to determine
translator values that accurately reflect site
specific conditions.
The procedures in this document do not
cover all possible approaches. Greater
precision can be achieved by means of more
elaborate procedures which, at the current time,
are generally used only in research situations.
Although, the use of such procedures is
acceptable, they will not be discussed in this
document.
1.5.1. Direct Measurement of the
Translator
As mentioned in Section 1.4, the most
straightforward approach for translating from a
dissolved water quality criterion to a total
recoverable effluent concentration is to analyze
directly the dissolved and total recoverable
fractions. The translator is the fraction of total
recoverable metal that is dissolved and may be
determined directly by measurements of
dissolved and total recoverable metal
concentrations in water samples.
1.5.2. Calculating the Translator Using the
Partition Coefficient
' Personal communication with Gregory
Pelletier. Department of Ecolo
gy
. Olympia WA (206)-
407-6485.
6
The partition coefficient (K
r) may be
derived as a function of the number of metal
binding sites associated with the adsorbent.
USEPA (1984) and the technical support
accompanying EPA's Dissolved Policy
Memorandum expressed the translator
according to Eqn 2.7. The role of TSS is
evident from this equation; as TSS increases,
the dissolved fraction decreases because of the
increased number of binding sites.
There is a general tendency to assume
that the partition coefficient will increase with
increasing TSS. It is important to recognize
that in both the laboratory and in the field, K p
has been observed to be constant or to decrease
with increasing particulate concentrations (Di
Toro, 1985).
The fraction of the total metal in the
downstream water that is dissolved (the
translator) may be determined indirectly by
means of a partition coefficient. The partition
coefficient, in turn, may be either a function of
varying adsorbent concentrations or be related
to a constant adsorbent concentration associated
with critical flow conditions. See Section 3.1.1
for considerations of factors affecting the
appropriate design flow for metals.
1.5.3. The Translator as a Rebuttable
Presumption
In the Technical Support Document for
Water Quality-based Toxics Control (EPA,
1991a) commonly called the TSD, as well as in
other documents, EPA has discussed the
options one has for translators. These options
include using a translator which assumes no
difference between dissolved and total
recoverable metal concentrations. The TSD
identifies this as the most stringent approach
and suggests it would be appropriate in waters
with low solids concentrations, situations where
the discharged form of the metal was mostly in
the dissolved phase, or where data to use other
options are unavailable. There are some
advantages to its use including the fact that it is
already being used by some States, it is easy to
explain and implement, and it effectively
implements the statutory requirement found in
§303(d) of the Clean Water Act calling for a
margin of safety (MOS) in developing TMDLs.
The disadvantage is that, as demonstrated by
the conversion factors used to convert total
recoverable water quality criteria into the
dissolved form, it is highly unlikely that metals
will remain totally in the dissolved form, even
in high quality water. Furthermore, when the
assumption that all of the metal is dissolved is
applied in combination with dissolved criteria
conversion factors, the resulting permit limit is
more restrictive than that which existed when
metal criteria were expressed as total
recoverable.
Therefore, as a rebuttable
presumption, conversion factors canbe
.
used as
the translator Where no site-specific translator
is -clev–ilbped; this is
.
the reasonable worst case.
1.6.?
Applying Metals Translators
If the translator is to be a function of
adsorbent concentrations (e.g.,TSS) it is critical
that samples be collected under a broad range
of TSS conditions to develop a statistically
robust translator. If the translator is not to be
functionally related to adsorbent concentrations
the study would normally be designed to collect
samples under low flow conditions where TSS
concentrations are relatively constant. Either
the directly determined ratio (C
a/CT)
or a
translator calculated using a partition
coefficient (K r ) may be used.
In actuality, metal partitioning in
receiving water bodies is more complicated
8
?
Cksina
.
the conversion factors as a translator will
produce the same result as assumin g_ no difference
between dissolved and total recoverable metal
concentrations.
7
than can be explained by TSS alone.
Consequently, it is possible and permissible to
develop the translator on some basis other than
TSS, such as humic substances or POC.
9 The
materials presented in Appendix C guide the
reader through a possible evaluation of other
factors that might be warranted in some studies.
Basically, the translator is applied by
dividing a dissolved WLA or permit limitation
by the translator to produce a total recoverable
permit limitation. Appendix A contains a
detailed explanation of how permit limits can
be derived.
'
9
If the adsorbent is POC. then K, (L/mg) =
Cp
(ig/L ) / (C o (p.g/L) • POC (in OL)
8
2.
UNDERSTANDING THE METALS
TRANSLATOR
he translator is the fraction of
the total recoverable metal in
the downstream water that is
dissolved. The reason for using a metal
translator is to allow calculation of a total
recoverable permit limit from a dissolved
criterion.
A translator is used to estimate the
concentration of total recoverable metal in the
effluent discharge that equates to (or results in)
the criterion concentration in the receiving
water body. In this chapter we will explore
some of the possible approaches to developing
site specific metals translators. The purpose of
this document is to help implement EPA's
dissolved metals policy; therefore, every
attempt has been made to keep the following
discussion as technically simple as possible.
As you read this discussion, keep in mind that
the metals partition between dissolved and
2
adsorbed forms. The partition coefficient
expresses this equilibrium relationship and may
be used to calculate the dissolved fraction. The
following discussion presents only the essential
equaviOns needed to develop the translator. For
a comprehensive discussion of partition
coefficients, see Thomann and Mueller (1987).
where
C
T =
total metal,
C, =
particulate sorbed metal, and
C
D
= dissolved metal.
The metal concentrations are typically
expressed as mass per volume (i.e., C
D
(mass/vol water), C
p
(mass/vol solids plus
water, the bulk volume)).
For a given adsorbent concentration
(e.g., TSS) C
p
can be expressed as
C p =
x • m
[Eqn 2.2]
where x is the metal concentration of the
particulate phase expressed on a dry weight
solids basis (e.g., µg/mg) andm
is
the
adsorbent concentration (mass of solids/vol of
solids and water; e.g., mg/L). With these
dimensions, C
p
has units of ug/L.
2.2. The Partition Coefficient and the
Dissolved Fraction
The distribution of metal at equilibrium
between the particulate and dissolved forms is
the partition coefficient K
p
(L/mg). The
partition coefficient is the slope of the data of
particulate metal (µg/mg) against dissolved
metal (p.g/L)
T
K
p
=x/C
D?
[Eqn. 2.3]
2.1. Sorption-Desorption
Theory
In effluents and receiving waters,
metals can exist in either of two basic phases;
adsorbed to particulates or dissolved in water.
More precisely, these "particulates" are
sorbents including clays and related minerals,
humic substances, organic and inorganic
ligands, and iron and sulfur compounds. The
total concentration of a metal in the water
column can be expressed as
C
T =-
Cp + C
D?
[Eqn 2.1]
Combining Eqn. 2.3 with Eqn 2.2
provides other useful relationships between
dissolved and particulate metals concentrations
Cp = C
D •
K
p
• m [Eqn 2.4]
Substituting Eqn 2.4 into Eqn. 2.1 gives
C
T
= Cp
CD
C T =
(CD • IC •
rn) +
CD
9
C T = C D
(K
p
• m + 1) [Eqn
2.5]
dissolved metal (C
D).
The translator, or dissolved metal fraction, f
0,
?
K
t,
?
x
/CD
is defined as
We also saw in Eqn. 2.2 that C
p = x •
m. If we
fp-
C
D / CT
?
[Eqn. 2.6]
let m = TSS, then x = C
p
TSS.
Substituting into Eqn 2.3 gives
Substituting Eqn 2.6 into Eqn 2.5 and solving
for
gives
I
fo = (1 + Kp
• m)-1
[Eqn.
2.7]
The distribution of metal between dissolved
and adsorbed phases therefore depends on the
partition coefficient and the adsorbent
concentration. This is the basis of the metals
translator.
K
p = (C
p
/ TSS ) /
C
D
[Eqn. 2.8]
which rearranges" to
Kp = Cp
/ (C0
•
TSS ) [Eqn. 2.9]
2.2.1. Developing Site Specific Partition
Coefficients
As we saw in Eqn. 2.3, the partition
coefficient is not measured directly, rather it is
calculated from measured values (at
equilibrium) of adsorbed metal per unit
adsorbent' (x) divided by the concentration of
10
TSS is used throughout this document as the
measure of metal bindin
g
sites. It is possible to use other
measures of the binding sites such as total organic carbon
(TOC), particulate organic
carbon (POC), dissolved
organic carbon (DOC), or some combination of TSS, TOC,
DOC, etc.
If Kr is desired
with units of L/k
g, Eqn 2.9 is
modified
by the conversion factor of 10' kg/mg:
K, (Like) = C,
(ugrL ) (CD
(i.ig/L) •
TSS
(mg/L)
• 10' (kg/mg))
10
3.?
FIELD STUDY DESIGN
onsideration should be given to
use of clean sampling and
analytical techniques. These
are recommended but not necessarily required;
however, it is essential that appropriate
procedures be used to detect metals at the
concentrations present in the effluent and
receiving waters. Clean sampling and
analytical methods are useful ways of obtaining
good data when traditional methods may
provide data with significantly high or low bias.
Sufficient quality control data must accompany
environmental data to allow its validation.'
A statistically valid field study design,
with attendant QA/QC, (e.g., adequate number
of samples, field blanks, spiked samples, etc.)
is essential for the successful development of a
metals translator. Recognizing that a key factor
in metals availability to biota in the water
column is the partitioning of metals between
the solid phase material and water, TSS (which
contains humic materials, clay minerals, other
organic matter both living and dead) emerges
as the obvious environmental variable of
interest. However, the composition of TSS is
highly variable both in terms of the constituents
(e.g., sand, silt, clay, planktonic organisms, and
decomposing organic materials) and their size
distributions. Highly variable relationships
between TSS and metals partitioning must be
anticipated because of the temporal (e.g.,
season of year, type and magnitude of storm)
and the spatial variability (e.g., such as may be
associated with changes in hydrology,
geochemistry, or presence, number, and type of
effluent dischargers) of the receiving water
12
Measurements made below the quantitation
levels (Q1..) will suffer from significant analytical
variability, which may directly affect the ratio (especially
if the ratio in near 1.0). Test measurements capable of
achieving extremely low detection levels and QLs should
be sought to avoid the excessive analytical variability.
The choice of laboratories and analytical methods can be
critical to the success of a translator study.
bodies. For example, pH may vary over
several units as a result of acidic precipitation
in the watershed, photosynthetic activity in the
water body (lowest pH at dawn and highest pH
in early afternoon coincident with peak
photosynthetic activity of phytoplankton and
other aquatic vegetation), or effluent discharge
to the water body. Changes in pH over a
specific range may have a marked effect on
metal solubility. Consequently, it may be
important to consider the normal range of pH
when designing the study and to collect
samples under pH conditions that would render
the metal or metals of interest most soluble, or
over a narrow range of pH conditions to reduce
scatter in the resulting data set. The pH effect
is of concern in geographic areas that have little
buffering capacity and on "acid sensitive"
streams.
Industrial and municipal waste waters
and receiving waters vary greatly in chemical
constituents and characteristics. This chapter
presents general guidelines and considerations
to assist in establishing effective sampling .
programs for varied situations.
3.1.?
Sampling Schedule
The sampling design should be
adequate to evaluate spatial and/or temporal
variability and to properly characterize the
environmental condition. The choice of when
and where to conduct the study, how long to
study, and how frequently to sample may be
influenced by the type of translator being
developed.
For instance, the translator may be
developed specifically for use under conditions
that are most likely to be representative of
"critical flow" or "design" conditions. (The
critical flow may or may not be the same as the
7Q10 or 4B3 design low flow; this is discussed
in Section 3.1.1 below.) To meet this
application, samples should be collected under
1 1
conditions that approximate the critical flow.
On the other hand, the translator may
be developed for use over a broad range of flow
and associated TSS concentrations. if this is
desired, then the samples should be collected to
produce a data set representative of a broad
range of conditions.
3.1.1. Considerations of Appropriate
Design Flow Conditions for Metals
In the absence of data to the contrary,
the normal assumption will be that low flow
(limited dilution capacity) is the critical flow
for metals.'
However, determining the period
of critical flow is more complicated for metals
than for many other pollutants because one
cannot necessarily ascertain the appropriate
design conditions without a field study to
generate data on flow, pH, and adsorbent
concentrations. If one were to collect samples
of TSS, POC, water flow, hardness pH,
ambient metals, etc. over.a prolonged period
(i.e., several years) then one could examine the
data set to determine which combination of
conditions would result in the highest dissolved
metal concentration for a "unit load" of metal
in the effluent stream. The flow regime
associated with this critical condition would
constitute the design flow. Because the
dissolved metals concentration in the receiving
water depends on metals partitioning to solids
as well as dilution of dissolved metals in the
water, and because the lowest TSS (or other
adsorbent) concentrations do not always
correspond with low stream flow conditions,
there will be some combination of TSS, flow,
hardness and pH that will result in the greatest
dissolved concentration.
13
It
is important to recognize that worse-case
acute dilution (hi
g
hest concentration of effluent) may not
occur
durin
g
. periods of low flow and TSS. especially in
estuarine waters. Under such circumstances. the data to
develop the translator should be collected to represent the
critical conditions.
For instance, consider a facility that has
high solids releases and contributes a sizeable
fraction of the receiving water flow. It may be
that TSS concentrations in the mixing zone
show a bimodal distribution with stream flow
(high under low flow conditions because of the
effluent dominance, low under higher stream
flow conditions because of greater dilution, and
high under high flow conditions because of
upstream nonpoint source solids loadings). It is
conceivable that the low TSS may be more
important than low flow in achieving water
quality standards in this stream segment.
Additionally, pH may vary throughout
,
the day,
may vary seasonally, or may be somehow
correlated With flow. Information of this nature
should also be used in selecting the most
appropriate conditions and most appropriate
time to conduct the study.
To reduce
variability in the data caused by factors other
than adsorbent concentration, it will be helpful
to measure pH and, to the extent possible,
collect samples under similar pH conditions.
As suggested above, samples should be
collected under pH conditions that would
render the metal(s) of interest most soluble.
3.1.2.
Frequency and Duration
of Sampling
A field study to develop a metals
translator is expected to extend over several
months. A long sampling schedule has many
advantages, chief among them is the ability to
generate data that are representative
. of the
rriany conditions that characterize receiving
water bodies. Ideally, prior to collecting data
to develop a metals translator, the receiving
water body would have been studied
sufficiently to characterize temporally, if not
spatially, distributions of flow, TSS, hardness.
and pH. To the extent that such data exist, the
sampling can be stratified to reduce variability.
If such data are available to characterize the
system, statistical methods may be used to
determine the frequency of sampling.
In the
absence of such data, EPA suggests weekly or
12
biweekly sampling during specified receiving
water flow conditions when developing the
translator for use under "design flow"
conditions and biweekly or monthly sampling
when developing the translator for use over a
range of flow conditions.
In addition to receiving water
conditions, it is equally important to consider
variable plant operations when determining
sampling frequency. In addition to continuous
and uniform releases, the range of conditions
may include:
(1)
Seasonal operation,
(2)
Less than 24 hour per day
operation,
(3)
Special times during the day, week
or month, or
(4)
Any combination of the above.
When monitoring these types of
operations, it is necessary to sample during
normal working shifts in the season of
productive operations.
3.2.
?
Sampling Locations
Depending-on-state–guidance..or.
regulatory negotiations, samples may be
collected from.the_effluent, the receiving water
before mixing with the effluent, the receiving
water at the edge of the mixing zone, and/or the
receiving water in the far field (beyond the
mixing zone). Results obtained from these
different locations may differ substantially.
The magnitude of the translator may
depend on the concentration of effluent in the
downstream water. The concentration of
effluent in the downstream water will depend
on where the sample is taken, which will not be
the same for acute and chronic mixing zones.
The criteria maximum concentration (CMC)
applies at all points except those inside a CMC
mixing zone; thus if there is no CMC mixing
zone, the CMC applies at the end of
,
the pipe.
The criteria chronic concentration (CCC)
applies at all points outside the CCC mixing
zone.
There are some practical difficulties
involved in selecting the sampling location in
the receiving environment. In the absence of a
mixing zone study it is very difficult to define
with any certainty the shqpe and extent of a
mixing zone, or the dilution and dispersion that
occur within the mixing zone. Many states
have separate boundaries for compliance with
acute and chronic criteria. Dilution and
dispersion processes are influenced not only by
volume, velocity, and other characteristics of.
the discharge, but also by convection, currents,
and wind effects in the receiving water. As a
result, extensive sampling and computer
modeling are typically required to estimate the
nature and extent of mixing.
The following approaches are
acceptable for the purpose of developing the
translator. When deciding where to locate
sampling stations, consideration should be
given to sampling at the point of complete
mixing (rather than at the edge of the mixing
zone) if existing environmental factors
constitute a basis for concern that downstream
conditions may result in nontoxic metal
becoming toxic.
3.2.1. Collect Samples at or Beyond the
Edge of the Mixing Zone
It is recommended that samples be
collected at or beyond the edge of the mixing
zone. Appropriate field sampling techniques
and appropriate QA/QC are discussed in
Appendix E. It is important to recognize that if
samples are not also collected from the ambient
water (background), then the subsequent
analysis (for permit limit determination)
implicitly assumes that
all
of the metal in the
receiving water comes from the discharger.
13
The translator should result in a permit
limit that is protective of the receiving water.
In order to ensure this,
under some conditions,
it may be important that samples be collected
from a point where complete mixing has
occurred. It may be advisable within a given
river segment to take the samples well below
the edge of the mixing zone in order to ensure
good mixing and to reduce variability in the
data set. Environmental processes that might
cause nontoxic metal to become toxic include
fate processes such as oxidation of organic
matter or sulfides or an effluent or tributary that
lowers the pH of the downstream water. The
approach of collecting samples beyond the edge
of the mixing zone may be especially valuable
in estuarine and coastal ocean locations where
the ebb and flow of tidal cycles complicate the
hydrodynamics.' In areas where cumulative
discharge effects can be anticipated, the
individual contributions and combined effects
of the multiple discharges must be considered
in developing the translator, as well as in the
TMDL allocation and development of the
permit limit.
3.2.2. Collect Samples from the Far Field
There are times when concerns for far
field effects will require evaluation of the ratios
of dissolved and total recoverable metals and
metal partitioning beyond the mixing zone. Far
field sampling is appropriate in circumstances
where changes in geology, land use/land cover,
or low pH effluent discharges from other
facilities may alter the water body chemistry.
Far field studies also may be required where
spatial changes in water chemistry and
hydrology affect sorption-desorption rates and
settling rates respectively with the potential
adverse effects on the biological integrity of
benthic communities. The potential for
increased dilution resulting in lower metal
1 4 ,
his document does not discuss hydrologic
differences that are specific to marine and estuarine
discharges.
concentrations and increased analytical
difficulties must also be considered when
contemplating these studies. If, however, the
samples are collected within the same reach,
there should not be any appreciable increase in
dilution.
If samples for translators are collected
from far-field locations a translator will result
whose value is established based on the
characteristics of the receiving water, not on
the characteristics at the edge of the mixing
zone or on the characteristics of the effluent
before it is fully mixed. Recent investigations
of discharges from a Waste Water Treatment
Plant (WWTP) to a lowflow stream in Florida
have demonstrated an apparent increase in the
dissolved fraction of silver at a distance (travel
time) of four hours downstream of the
discharge.''
3.2.3.
Collect Samples from Effluent and
Ambient Water and Combine in the
Laboratory
Samples are collected from the effluent
(i.e., end of pipe) and the ambient receiving
water (i.e., upstream of the outfall in rivers and
streams; outside of the influence of the
discharge in lakes, reservoirs.. estuaries, and
oceans). Appropriate QA/QC and field
sampling techniques are discussed in Appendix
E. Mixing and filtration must be done as soon
as possible to minimize risk of changes to the
dissolved/total metals ratio due to adsorption
onto the container and partitioning effects. The
Agency is soliciting data that will allow
recommendations to be developed regarding
maximum delays in combining the samples and
how long the combined sample should be
allowed to equilibrate before filtering an aliquot
for the dissolved portion.
''
Personal communication with Tim Fitzpatrick.
Florida Department of Environmental Protection.
Tallahassee. FL.
14
Samples are collected from the effluent
and the receiving water before it mixes with the
discharge and are mixed in accordance with the
dilution factor to create a simulated
downstream water in proportion to the dilution
that the mixing zone is designed to achieve.
The mixed waters are analyzed for dissolved
and total recoverable metal. The translator is
calculated from the dissolved fractions.
For rivers and streams, the receiving
water samples would be collected upstream of
the discharge. For lakes, reservoirs, estuaries,
and oceans, the samples would be collected at a
point beyond the influence of the discharge, yet
representative of water that will mix with the
discharge. In tidal situations, where the
effluent plume may move in different
directions over the tidal cycle, some knowledge
of the hydrodynamics of the receiving water
will be necessary to select the appropriate point
as well as the appropriate sampling time within
the tidal cycle. In estuaries that are dominated
by either river flow or tidal flushing, the
sampling location should reflect the dominant
source of dilution water.
In cases of multiple discharges to the
same river segment, for example, the translator
should be developed as f;, at the downstream
end of the river segment and applied to all
dischargers to that segment
3.3.?
Number of Samples
Most statistics textbooks (e.g.,
Sriedecor, 1956; Steel and Torrie, 1980; Zar,
1984; Gilbert, 1987)) present discussions of
sample size (i.e., number of samples).
Generally, sample size is affected by the
variance of the data, the allowable error in the
estimation of the mean, and the desired
confidence level. If data have been collected
previously, they can be used to provide a good
estimate of the expected variance.
From a statistical basis we can specify
a theoretical minimum number of samples.
Beyond this consideration, it is necessary to be
cognizant of such factors as spatial and
temporal variability in physical and chemical
conditions that may affect the value of the
translator and to design the study to
appropriately account for these differences.
Seasonality of receiving water flow and
associated chemical properties need to be
considered. The value of the translator must be
appropriate to provide protection to the water
body during the low flow or otherwise critical
condition associated with a particular critical
time of the year.
In the metals guidance memorandum
(Prothro, 1993), EPA recommended the
development of site-specific chemical
translators based on the determination of
dissolved-to-total ratios: EPA's initial
recommendation was that at least four pairs of
total recoverable and dissolved ambient metal
measurements be made during low flow
conditions or 20 pairs over all flow conditions.
EPA suggested that the average of data
collected during low flow or the 95th percentile
highest dissolved fraction for all flows be used.
The low flow average provides a representative
picture of conditions during the rare low flow
events. The 95th percentile highest dissolved
fraction for all flows provides a critical
condition approach roughly analogous to the
approach used to identify low flows and other
critical environmental conditions.
The collection of dissolved and total
concentrations at low flows is still the
recommended approach, but the collection of at
least 10 samples, rather than 4, is
recommended to achieve higher confidence in
the data. The 95 th
percentile or other extreme
percentile of f
c
, (e.g., 90 th percentile) may be
MOS
used as
in
an
TMLDs
alternative
or WLAs.
method
Additional
of includindetailsga
of determining the required sample size are
presented in Appendix D.
15
3.4 Parameters
to Measure
Ideally the field study is designed to
generate data on total recoverable (CT),
dissolved (C
D
), and particulate metal fractions
(C
p
) as well as TSS, POC, pH, hardness, and
stream (volume) flow. A complete data set
allows for more complete understanding of the
environmental fate and transport processes and
may result in a more accurate
• permit limit
because of reduced variability and
uncertainties.
Depending on the means by which the
translator is being developed, some of these
data elements may not need to be generated.
For instance, it may be desirable to estimate
Cp= CT - C
D
rather than to measure C
p. Of
course, if C
p
is the parameter of greatest
interest, calculating C
p from the dissolved and
total recoverable concentrations incorporates
the uncertainty associated with the latter two
measurements. A direct measurement of the
particulate fraction may reduce this uncertainty.
Of course, the measurement of the particulate
fraction then increases the total uncertainty
because of the uncertainty associated with its
measurement. It is likely that if the three
fractions (total, dissolved. and particulate) are
measured, the sum of these three fractions will
not equal C T .
It is possible to develop the
translator from a study that only generates data
on total recoverable and dissolved
concentrations in the downstream water.
3.5. The Need for Caution in Sampling
The sampling procedures for metals
that have been used routinely over the years
have recently come into question in the
academic and regulatory communities because
the concentrations of metals that have been
entered in some databases have been shown to
be the result of contamination. At EPA's
Annapolis Metals Conference in January of
1993. the consensus of opinion was (1) that
many of the historical low-concentration
ambient metals data are unreliable because of
contamination during sampling and/or analysis,
and (2) that new guidance is needed for
sampling and analysis that will produce reliable
results for trace metals determinations.
EPA has released guidance for
sampling in the form of Method 1669
"Sampling Ambient Water for Determination
of Trace Metals at EPA Water Quality Criteria
Levels" (USEPA, 1995a). This sampling
method describes the apparatus, techniques, and
quality control necessary to assure reliable
sampling. Method 1669 was developed based
on information from the U.S. Geological
Survey and researchers in academia, marine
laboratories, and the commercial laboratory
community. A summary of salient points are
presented in Appendix E. Interested readers
may also wish to refer to the 1600 series of
methods, CFR 40, Part 136, July 1, 1995.
Note that recent studies conducted by
the USGS (Horowitz, 1996) indicate that great
bias can be introduced into dissolved metals
determinations by filtration artifacts. The use
of the Gelman #12175 capsule filter, which has
an effective filtration area of 600 cm = , and the
practice of limiting the volume of sample
passed through the filter to 1000 ml are
necessary to ensure unbiased collection of
dissolved metals. Variations from these
recommendations must be demonstrated to
produce equivalent quality data.
16
4.?
DATA GENERATION AND
ANALYSIS
etermination of metals'
concentrations at ambient
criteria levels is not presently
routine in many commercial and industrial
laboratories. To familiarize laboratories with
the equipment and techniques that will allow
determination of metals at trace levels, the
Agency has supplemented existing analytical
methods for determination of metals at these
levels, and published this information in the
"Quality Control Supplement for Determination
of Trace Metals at EPA Water Quality Criteria
Levels Using EPA Metals Methods" (QC
Supplement; USEPA, 1994a). The QC
Supplement is based on the procedures and
techniques used by researchers in marine
research laboratories who have been at the
forefront of trace metals determinations.
An overview of the QC Supplement is
presented in Appendix E for the reader's
convenience. Persons actually developing a
metal translator should read the QC
Supplement
4.1.?
Analytical Data Verification and
Validation
In addition to Method 1669 for
sampling (USEPA, 1995a) and analytical
methods for determination of trace metals
(USEPA, 1994b), the Agency has produced
guidance for verification and validation of
analytical data received (USEPA, 1995b). This
guidance was produced in response to the
Agency's need to prevent unreliable trace
metals data from entering Agency databases
and other databases in the environmental
community and relies on established techniques
from the Agency's data gathering in its Water
and Superfund analytical programs to
rigorously assess and document the quality of
analytical data. General issues covered in the
guidance include:
The data elements that must be
reported by laboratories and permittees
so that Agency reviewers can validate
the data.
The review of data collected and
reported in accordance with data
elements reported.
A
Data Inspection Checklist
that can be
used to standardize procedures for
documenting the findings of each data
inspection.
4.2.?
Evaluation of Censored Data Sets
Frequently data sets are generated that
contain values that are lower than limits
deemed reliable enough to report as numerical
values (i.e., quantitation levels [QL]). These
data points are often reported as nondetected
and are referred to as censored. The level of
censoring is based on the confidence with
which the analytical signal can be discerned
from the noise. While the concentration may
be highly uncertain for substances below the
reporting limit, it does not necessarily mean
that the concentration is zero (USEPA. 1992).
Measurements made below the
quantitation levels will suffer from analytical
variability, which may directly effect the ratio,
especially if C
D/C T
is near 1.0. Extremely low
detection levels and quantitation levels should
be sought to avoid excessive analytical
variability.
This guidance does not address whether
or not it is appropriate to use test measurements
below quantitation or detection levels in any
context other than chemical translator studies
conducted by the discharger. For translator
studies, measurements at or above a detection
level that is reliably achievable by the
17
Box 1. The Translator is the Dissolved
Fraction: fp
=
CD/CT
Step 1 - For each field sample determine
fp = C
D
/C
T
Step 2 - If the translator is not dependent
on TSS, determine the geometric
mean
GM_fD=
exp(E
l n ln(fD
)/ n)
and upper percentile values of the
dissolved fraction. If the data are
found not to be log-normal, then
alternative transformations should
be considered to normalize the
data and determine the
transformed mean and percentiles.
Also, alternative upper percentiles
may be adopted as a state's policy
to address MOS (e.g., 90 `11
or 95th
percentiles may be appropriate.)
Step 3 -
If the translator is found to be
dependent on TSS, regression
equations relating f
p
to TSS should
be developed. Appropriate
transformations should be used to
meet the normality assumptions
for regression analysis (for
example log-transformation of f
and TSS may be appropriate). The
regression equation or an upper
prediction interval may be
considered for estimation offp
from TSS depending on the
strategy for addressing MOS.
particular laboratory performing the analyses
can be used. If concentrations are near the
detection level, some of the samples may be
reported as below the detection level (i.e.,
nondetects). If both total re_o_v.erable-and
dissolved concentrations ale_nondeteets,--the
data pair should be discaLcie.d. If only the
dissolved concentration is nondetect. it-could-be
assurried to equal one-half the_
detec.tionlevel,
Some studieshave collected enough data so
that incomplete records, including records
where dissolved concentrations were
nondetects, were discarded prior to analysis. If,
for example, the translator is a function of TSS,
the TSS concentration that accompanies each
total recoverable and dissolved data pair must
also be at or above the detection level.
Alternatively, assuming that an adequate
number of samples have been collected,
incomplete records may be eliminated from
analysis.
4.3?
Calculating the Translator Value
The most direct procedure for
determining a site-specific metal translator is
simply to determine f
p by measuring
C T and
CD
and to develop the dissolved fraction as the
ratio C D/CT
. The first step (Box 1) is to
calculate the dissolved fraction in the receiving
water. The translator is calculated as the
geometric mean of the dissolved fractions.
As a general comment on the proposed
use of the geometric mean, the geometric mean
is only an appropriate estimate of the central
tendency if the data are log-normal.
Alternative measures of central tendency or
transformations should be considered if the
distribution of fp
is found not to be lo-normal.
For example, the arcsine square root
transformation is often used to normalize
populations of percentages or proportions
18
(square root of each value is transformed
to its
arcsine).
A partition coefficient may be derived
as a function of TSS and other factors such as
pH, salinity, etc. (Box 2). The partition
coefficient is the ratio of the particulate-sorbed
and dissolved metal species multiplied by the
adsorbent concentration. The dissolved
fraction and the partition coefficient are related
as shown in step 3.
Box 2.
The Translator is the
Dissolved Fraction (fD)
Calculated via Site Specific
Partition Coefficients
Step 1 - For each field sample
determine
C
p
= C
T
-
CD ,
K
p
= C
p
/(C
p
• TSS)
Step 2 - Fit least squares
regressions to
data (transformed, stratified by
pH, etc.) as appropriate
to
solve
for Kp.
Step 3 - Substitute the regression
derived value of K
p
in Eqn 2.7,
fp = (1 +
K
p
• TSS)`
Step 4 Determine f
p
for a TSS value
representative of critical
conditions.
The partition coefficient may provide
advantages over the dissolved fraction when
using dynamic simulation for Waste Load
Allocation (WLA) or the Total Maximum
Daily Load (TMDL) calculations and permit
limit determinations because K
p
allows for
greater mechanistic representation of the
effects that changing environmental variables
have on fp.
Examples of these analyses to
determine appropriate translator values are
presented in Appendix C.
19
5.?
SITE-SPECIFIC STUDY PLAN
C
hapter 3 discusses the
considerations involved in
designing a field study for a
site-specific chemical translator for metals.
Chapter 4 and Appendix D discuss analytical
chemistry considerations. This Chapter
provides guidance on preparing a basic study
plan for implementing a translator study, with
specific considerations for each of four types of
receiving waters: rivers or streams, lakes or
reservoirs, estuaries, and oceans. It can be used
for all of the options discussed in this guidance.
This generic plan is based on the determination
of-dissolved-to-total
ratios in a series of 10 or
more samples. With this guidance, the
discharger should be able to prepare a study
plan that its environmental staff could
implement or one that could be used to solicit
bids from outside consultants to conduct the
studies.
In most cases, the study plan should be
submitted to the state for review and approval
before implementation.
The format of this chapter is.to present
sequentially the essential sections of a study
plan: - objective, approach, parameters,
sampling stations. sampling schedule,
preparation, sampling procedure, field protocol,
and data analysis. Within each section a three-
tiered format is used to provide instructions for
the study plan preparer. The basic directions
for preparing the section are presented left-
justified on the page. Under each direction is a
checklist of decisions or selections, designated
with the symbol 0, that the preparer must make
to complete that direction. Under each of these
decision points is a list of important
considerations, noted by the symbol *.
References to more detailed discussions are
provided where appropriate. If any state
guidance
for translator studies exists. it would
supersede any of the considerations discussed
below unless the state and the discharger agree
to an alternative plan.
Much of the basic study plan is
presented in a generic context that is applicable
to any type of receiving water. Where
differences in the study plan would occur for
different receiving waters, the considerations
are highlighted with a +. Dischargers on run-
of-river reservoirs, or on lakes or reservoirs
dominated by riverain discharges during runoff
events, should generally follow the
considerations listed for rivers/streams.
?
5.1.?
Objective
State the objective of the project. For
example,
"To determine the acute [or
chronic or acute and chronic]
metals translator for [list
metals] in the discharge from
Outfall 00X."
?
5.2.?
Approach
Describe briefly the approach adopted
in the study plan to achieve the objective. For
example,
"Samples of effluent and
upstream receiving water will
be collected and mixed in
proportions appropriate to the
dilution at the edge of the
[acute/chronic] mixing zone[s].
These mixed samples will be
analyzed for total recoverable
and dissolved [list metals]. The
translator will be calculated as
the geometric mean of the
ratios of dissolved metal to
total recoverable metal for all
sample pairs."
Equipment blanks and field blanks are
critical to document sample quality.
20
especially at low concentrations which can be
significantly biased by even small amounts of
contaminants. Field duplicate samples are also
very important to establish precision in
sampling and final sample preparation.
5.3.?
Parameters
Prepare a table listing parameters,
analytical methods, and required detection
levels.
Select parameters—see Section 3.4.
q
Select analytical methods and detection
levels—see Section 4.
•
Detection level will be the primary
determinant of the analytical methods
to be used. Metals potentially requiring
GFAA and perhaps ultralow analyses
are those with very low aquatic life
criteria and concentrations below 10
/
./.g/L. Prime candidates are cadmium
(fresh water), copper (salt water),
mercury, and silver.
•
Ideally, the detection level should be 5-
10 times lower than the concentration
of dissolved metal. An ultralow
detection level should be considered if
dissolved concentrations are less than
1-2 times higher than the standard
detection level.
•
Detection levels and methods should be
reviewed with the analytical laboratory
expected to perform the analyses before
finalizing the study plan. One or more
test samples may be advisable if
detection levels or concentrations are
unknown in any particular matrix.
•
Estuary/Ocean
Chloride interference
may affect detection levels, particularly
for GFAA methods. Special steps may
be necessary to achieve detection levels
low enough to produce a valid
translator. Such alternatives include
matrix modifiers, background-
correction instrumentation, and
extraction or preconcentration. If
uncertain, check with a local laboratory
experienced in saltwater matrix
analyses. Preliminary testing and
detection level studies may be
necessary to determine if a problem
exists.
As an option for justifying the selected
methods and detection levels to the regulatory
agency, prepare
.
a narrative of the rationale for
the selections made.
Identify the laboratory that will be
analyzing the samples and provide evidence of
state certification, if required.
Describe laboratory protocols and QA
requirements.
q
Select standard or clean (class-100)
practices—see Section 3.1, 4.3.
Select QA requirements
•
Trip blank
•
Duplicate analysis of all samples and
blanks
•
Laboratory method blank for each
batch of samples
•
MS/MSD on each batch of samples
5.4.
?
Sampling Stations
Prepare a map and/or a narrative
description of the sampling stations.
1=1?
Select a sample location option—see
Sections 3.2, 3.2.1, 3.2.2, 3.2.3.
•
Conceptually, collecting samples at the
21
edge of the mixing zone is the
most direct way to determine
the translator. However, the
edge of the mixing zone may
be difficult to define, especially
if stream flow and discharge
rate (e.g., number of units
operating) will be variable over
the course of the study. Even if
the mixing zone's dimensions
are prescribed exactly, the
samples may have to be
collected at some critical
hydrologic condition to
represent the critical
toxicological conditions. An
alternative option may be to
collect effluent and upstream
receiving water samples, and
mix them in the appropriate
proportions before analysis. In
addition, far-field sampling
may be required to establish
that dissolved metal
concentrations do not increase
after the effluent is well-mixed
with the receiving water.
•
Definition of the "upstream" sampling
point will vary with the receiving water
type:
♦
River/Stream
Immediately upstream
of the influence of the discharge, or any
point further upstream with no
contributing source between it and the
outfall
♦
Lake/Reservoir
Beyond the influence
of the discharge (dilution > 100:1),
generally in a direction toward the
headwaters of the lake/reservoir if
possible
•
Estuary/Ocean
Beyond the influence
of the discharge (dilution > 100:1),
generally in a direction away from the
movement of the discharge plume at
the time of sampling,
q
Determine whether grab or composite
samples will be used —see Appendix
E.
•
Wastewater treatment plant
effluent-24-hour composite
•
Noncontact cooling water—same as
receiving water
♦
River/Stream—Grab,
under low-flow
conditions
0?
Lake/reservoir—Grab
♦
Estuary/Ocean—Grab
(slack tide) for
acute; tidal composite for chronic
5.5.?
Sampling Schedule
Specify the number of samples,
frequency of sampling, study period, and any
other conditions (e.g., season, stream flow)
affecting the sampling schedule.
q
Select the number of samples—see
Section 3.3.
' •?
The recommended minimum number
of samples for a low-flow sampling
program is 10; 12 would be appropriate
if monthly sampling for a year is
desired to incorporate seasonality.
•
If sampling occurs over a wide range of
flows or the translator is developed
through regression analyses, 20 or more
samples may be appropriate.
q
Select the frequency of sampling—see
Section 3.1.2.
•
Weekly sampling is recommended;
monthly sampling may be appropriate
if seasonality is expected to be an issue.
♦
River/Stream
The interval between
samples will have to be somewhat
flexible because samples should be
collected under low-flow conditions:
e.g., if a sample is to be collected on
Wednesday and the river flow is high
22
on that day, sampling should be
postponed until the first day
when flow returns to base-flow
levels, or it will have to be
postponed until the next
planned weekly event.
♦
Estuary/Ocean
Monthly or biweekly
sampling may be required if state
regulations reference critical monthly
tidal periods, such as biweekly neap
tides.
q
Determine the study period—see
Section 3.1.
•
River/Stream
Generally, the low-flow
period of the year (e.g., July through
October in the East and Midwest) is
preferred, unless the time constraints of
the permitting process or the local •
hydrologic regimen dictate otherwise.
•
Lake/Reservoir
Unless there are
seasonal discharges or reservoir
operating procedures that significantly
affect water quality, study period
generally is not critical to study plan.
Algal bloom conditions should be
avoided.
•
Estuary
May need to split sampling
between low- and high-salinity seasons,
because large changes in salinity
between seasons indicates the
dominance of different water sources
(fresh water at low salinity and salt
water at high salinity) with potentially
different particulate matter
concentrations or binding capacities.
•
Ocean
Unless seasonal currents
significantly affect water quality, study
period generally is not critical to study
plan.
q
Determine other important
considerations
•
Plant operating conditions should be
considered. Samples should be
collected during periods of typical
operation, particularly with respect to
operations that affect the TSS
concentration or the concentration or
the total:dissolved ratio of the metal(s)
being studied.
•
If copper is being studied by an electric
utility, and the plant has copper and
non-copper condenser tubes, sampling
should occur when the units with
copper tubing are operating.
•
River/stream
Sampling should be
conducted under base-flow conditions,
which could be defined in terms of
measured stream flow (e.g., less than
the 25th percentile low flow), stream
stage (e.g., stream height less than 1.5
feet at gaging station XYZ), turbidity
(e.g., less than 5 NTU), TSS
concentration (e.g., less than 10 mg/L),
visual appearance (e.g., no visible
turbidity), or days since last significant
rainfall (e.g., more than 3 days since
rainfall of 0.2 inches or more).
•
Lake/Reservoir.
As long as the
sampling location is unaffected by
runoff, hydrologic considerations are
,
not significant.
•
Estuary/Ocean
Since acute criteria
are generally considered to have an
exposure duration of 1 hour, samples
for acute translators should be collected
under worst-case tidal
conditions—generally low slack when
dilution is typically at its lowest.
Chronic criteria are usually expressed
with a 4-day average exposure
duration, so sampling over a tidal cycle
is appropriate for chronic translators. If
the discharger is willing to accept the
conservatism of sampling for a chronic
translator under worst-case
conditions—slack tide—then sampling
costs could be reduced substantially.
5.6.
?
Preparation
23
Prepare a list of equipment and supplies
that need to be assembled before each sampling
event; for example.
Sample bottles, labeled, with
preservative (for total recoverable)
Samples bottles, labeled, without
preservative (for dissolved
Sample bottle carrier, e.g., clean plastic
cooler
Waterproof marker for filling in bottle
labels
Chain-of-custody form
Sampling gear—e.g., sampling bottle,
sampling pole (plastic or aluminum if
aluminum is not being studied), high-
speed peristaltic pump and teflon
tubing
Field portable glove box (for on-site
filtering and compositing)
Plastic gloves (non-talc)
Filtering apparatus, if required for field
crew
Field notebook or lo
g sheet
Safety equipment
Describe cleaning requirements for
sample bottles and sampling equipment that
will come in contact with samples.
q Select
standard or clean
sampling/analysis.
Prepare a list of actions to be
completed before the sampling event, such as
contacts to be made (discharger, consultant,
laboratory, regulatory agency).
Prepare a list of contacts and phone
numbers.
5.7
Sampling Procedure
Prepare detailed instructions on the
correct procedure for collecting a sample at any
station.
Start with guidance on the careful
sampling techniques necessary to avoid sample
contamination. For example,
Given the low metals concentrations
expected, extreme care needs to be
taken to ensure that samples are not
contaminated during sample collection.
Smoking or eating is not permitted
while on station, at any time when
sample bottles are being handled, or
during filtration.
Each person on the field crew should
wear clean clothing, i.e., free of dirt,
grease, etc. that could contaminate
sampling apparatus or sample bottles.
3.
An equipment blank should be done
with the actual equipment used for the
environmental samples. The field
blank described in this section should
be performed with the sampling
equipment BEFORE the environmental
samples are collected. This blank will
serve to verify equipment and sampling
protocol cleanliness.
4.
Each person handling sampling
apparatus or sample bottles should wear
the sampling gloves provided. One
person only should handle sample
bottles, and that person should touch
nothing else while collecting or
transferring samples.
Then provide step-b
y -step instructions
24
for the sampling crew to follow. The specific
steps will vary depending on what type of
water/wastewater is being sampled and what
type of sampling device is being used. For grab
samples collected by hand using a sampling
pole to which the sample bottles are attached,
the guidance might continue:
5.
Attach unpreserved bottle to sample
collecting pole. Plunge pole 2 to 3 feet
under water surface quickly. Pull
sample bottle up and fill preserved
bottle from unpreserved sample bottle,
leaving 'A to 1 inch of air space at the
top. Swirl to mix acid, close cap
tightly, and return bottle to carrier.
6.
Collect duplicate sample by plunging
unpreserved sample bottle back under
water, retrieving, and capping bottle
tightly for dissolved sample, again
leaving 1/2
to I inch of air space in the
bottle. Return bottle to carrier.
Other sampling procedures may be
chosen to produce acceptable quality data, e.g.
a closed sampling system with immediate
sample processing. Equipment for in-line
sample collection used for filtering with the
(essentially mandatory) Gelman capsule filter
can be used for sample collection. See Method
1669 § 8.2.8 for a description of sampling steps
and Method 1669 § 8.3 for on-site composting
and filtration in a glove box. See also
Appendix E.2.
5.8.?
Field Protocol
Provide a list of criteria which the field
crew leader should review before starting
sampling to ensure that proper conditions exist.
•
Is there a discharge? Are operating
conditions at the facility appropriate for
measuring the metals of concern in the
effluent?
•
Are hydrologic conditions (e.g., base
flow, slack tide) acceptable?
Describe
in clear, simple instructions
the sequence of actions that the field crew will
follow from the beginning to end of a sampling
event. This sequence will vary from project to
project. Typical steps might include:
1.
Before embarking, confirm number and
type (preserved/unpreserved) of sample
bottles, and read off checklist of
equipment/supplies.
2.
Before beginning sampling, fill in
•
chain-of-custody forms and bottle
labels with all information except time
of sampling.
•
Each bottle should have a unique
sample number, and it should be
labeled "Total" or "Dissolved." If
preservative has been added to the
bottles before sampling, the label
should note that fact.
•
Chain-of-custody forms pre-prepared
with everything but the sampling date
and time are recommended.
•
Provide sample chain-of-custody form
and bottle label as attachments to study
plan.
3.
At Station 1, fill in sampling time on
label of two samples bottles, one
preserved and one unpreserved.
Collect samples following the
procedure outline above. Return bottles
to carrier immediately after collection.
Fill in field notebook or log
form—weather, hydrologic conditions,
plant operating status (if known),
sample bottle numbers and collection
time (total and dissolved), and unusual
observations or circumstances.
4.
At Station 2, fill in sampling time on
labels of two sample bottles, one
25
preserved and one unpreserved.
Collect samples following the
procedure outline above.
Return bottles to carrier
immediately after collection.
Fill in field notebook or log
form—weather, hydrologic
conditions, plant operating
status (if known), sample bottle
numbers and collection time
(total and dissolved), and
unusual observations or
circumstances.
5.?
After finishing at Station 2, collect the
field blanks—one preserved and one
unpreserved. Fill in sampling time on
label, open sample bottle, and pour in
laboratory water. Cap bottles tightly
and place in carrier. Note bottle
numbers and collection time in field
notebook or log sheet.
If additional sampling gear is used in
collecting the samples, the field blanks
should be collected by rinsing that gear
three times with the laboratory water,
and then filling the gear with enough
water to transfer to the 2 field blank
bottles. If a pump or an automatic
sampler is used, several sample bottle
volumes of laboratory water should be
pumped through the sampler tubing
before the field blank bottles are filled.
Complete chain-of-custody. Check
bottle carrier to ensure bottles are
upright and well packed.
Deliver samples to laboratory. Have
sample custodian sign chain-of-custody
for receipt of samples, and obtain a
copy of the chain-of-custody.
Depending on the project, additional
instructions may be needed for setting up
automatic samplers, field filtering, and
overnight shipping of samples. Because data
quality is directly dependent on quality control,
the Quality Control Supplement( EPA, I994a)
should be reviewed.
?
5.9.?
Data Analysis
Describe the method for calculating the
chemical translator.
•
Select a calculation procedure—see
Sections 1.5.
•
Specify the treatment for values below •
the detection level—see Section 4.2.
?
5.10.?
Schedule
Provide a schedule for the entire study,
from selection of consultant or mobilization of
field effort through completion of final study
report.
•
Link schedule to receipt of approval
from state, if required
•
Emphasize impact of delays on study if
samplin
g
must occur within a certain
calendar timeframe
•
Incorporate contingencies for sampling
events postponed because of
unacceptable conditions
5.11. State Approval
Provide a signoff line for state
regulatory agency. This is recommended, but
not mandatory.
26
6.
?
?BUILDING A SPREADSHEET
MODEL
s discussed in earlier chapters,
a series of steps must be taken
to implement the dissolved
metals policy, including converting the water
quality criteria from the total recoverable to the
dissolved form, translation from the dissolved
CCC or CMC to the total recoverable metal
concentration in the discharger's waste stream,
calculating the WLA or TMDL, and developing
the permit limit. These steps or calculations are
easily handled using a simple spreadsheet
model. Use of these equations, whether in a
spreadsheet or not, can avoid many common
mistakes.
The following equations may be used to
translate dissolved criteria to total recoverable
permit limits with translators developed
through studies such as those described in
Chapter 5. This model may be used as a static
model with design flow conditions, it may be
used in a continuous mode (i.e.., using daily
flow and other data), or it may be used (with
programs such as @RISK or Crystal Ball ) to
perform Monte Carlo analyses. These
calculations do not provide concentration
estimates between the point of discharge and
the point of complete mixing.
The in-stream total recoverable
concentration is estimated by solving the
following equation:
C, = (6
• Q
u
• C, + Q
c •?
/ (0 • Qu
+ Q,)
[Eqn 6.1]
where C, = pollutant concentration at the
edge of the mixing zone,
Q u = upstream flow,
C, = upstream pollutant
concentration (background),
Q, = effluent flow,
C
e
= effluent pollutant
concentration, and
6 = fraction of flow available for
mixing.
For example, with Eqn 6.1, the
downstream TSS concentration is estimated
from mass balance calculations of upstream
and effluent loadings:
TSS (6 • Q
u • TSS u Q
e • TSS e) / (6 • Q
u + Qe)
[Eqn 6.2]
For translators developed from
partitioning equations 16,
(Eqn 2.7), the
dissolved in-stream concentration can be
expressed as:
Cd = Ct
(I+ Kp • TSS)?
[Eqn 6.3]?
•
By setting the dissolved in-stream
concentration (C
d) equal to the dissolved
criterion concentration (C
d
CC
d ) and
rearranging the equation, we can solve for the
in-stream total recoverable concentration (C ,')
that equates to a dissolved in-stream
concentration equal to the dissolved criterion.
Note that this corresponds to Eqn 2.5.
C,' = CC d (1+K u • TSS)?
[Eqn 6.4]
The total recoverable concentration in
the effluent (C
e
') that equates to a dissolved in-
stream concentration which equals the
dissolved criterion in the mixed receiving
waters is calculated by Eqn 6.5. This
represents the maximum release that will still
allow attainment of water quality standards,
16
If
the translator has been determined directly
from measurements of dissolved and total recoverable
metal in the downstream water, Eqns 6.3 and 6.4 are not be
used. Instead, the dissolved criterion concentration is
divided by fp to calculate
?
which in turn is used in Eqn
6
.5.
If the partition coefficient has units of Like. then
both Eqns 6.3 and 6.4 contain the term I E-6.
A
27
that is the maximum WLA or the maximum
TMDL.
c
e' =?
• Qu
+ Qt) -?
Q, • Cu)/
Q,
[Eqn 6.5]
Table 4 presents a simple spreadsheet
that utilizes these relationships. Note that the
second equation in the spreadsheet calculates
K p
and the third equation calculates the
associated f
p
. In studies where the translator is
developed directly as f
p
, the K r
equation in the
spreadsheet is deleted and f
p
is changed from
an equation to an input parameter.
Streamix, an EPA developed
spreadsheet application for mixing zone
analyses, has been enhanced to consider metal
partitioning between dissolved and particulate-
sorbed forms. This version, developed for
EXCEL, is called METALMIX and provides
details of mixing between the point of _
discharge and the point of complete mix.
Beyond these approaches, EPA's
DYNTOX model (USEPA, 1995c) has been
modified to properly account for the
distribution of metals between dissolved and
particulate-sorbed forms. DYNTOX supports
Continuous Simulation, Monte Carlo, and
Lognormal Probabilistic Analyses
Table 4.
?
Spreadsheet to Calculate Total Recoverable Waste Load Allocation based on Dissolved
Criterion
4/ariables:
Input
Values:
D_u
104
TSS_u
325
u
19
D_e
8.75
TSS_e
1845
-iardness_u
100
Hardness_e
50
mixing fraction (theta)
0.25
Equations:
::',C_d
=EXP(a*LN(Hardness_mix)+b)*conv_fact
?
<dissolved criterion concentration>
<p
=2.8*TSS
_mix^-0.8?
<example only>
D
=1/(1 +
Kp*TSS_mix)
-lardness_mix
=(theta
* 0_u
*
Hardness_u
+ Q_e
*
Hardness_e)
/
(theta
*
Q_u
+
Q_e)
TSS_mix
=(theta
*
Q_u
*
TSS_u
+
Q_e
*
TSS_e) /
(theta
*
Q_u +
Q_e)
:_t_prime
=CC_d*(1
/ fD)?
<instream total recov conc that equates to dissolved criterion>
72,_e_prime
=(C_t_prime
*
(theta
*
Q_u
+
Q_e) - theta
* Q_u
* C_u)/ Q_e
<effluent total recov conc resulting in the dissolved criterion in receiving water>
28
7.?
REFERENCES
Benedetti, M,F., Milne, C.J., Kinniburgh, D.G.,
Van Riemskijk, W.H., and Koopal, L.K. 1995.
Metal Ion Binding to Humic Substances:
Application of the Non-Ideal Competitive
Adsorption Model. Environ. Sci. Technol.
29,446-457.
Di Toro, D.M. 1985. A Particle Interaction
Model of Reversible Organic Chemical
Sorption. Chemosphere 14(10):1503-1538.
Gilbert, R.O. 1987. Statistical Methods for
Environmental Pollution Monitoring. Van
Nostrand Reinhold, NY.
Horowitz, A.J., Lum, K.R., Lemieux, C.,
Garbarino, J.R., Hall, G.E.M., Demas, C.R.
1996. Problems Associated with Using
Filtration to Define Dissolved Trace Element
Concentrations in Natural Water Samples.
Environmental Science & Technology, Vol 30,
No 3.
Shi, B., Grassi, M.T., Allen, H.E., Fikslin, T.J.,
and Kinerson, R.S. 1996. Development of a
Chemical Translator for Heavy Metals in
Receiving Water. Paper Presented at Water
Environment Federation 69th Annual
Conference & Exposition, Dallas, TX
Snedecor, G.W. 1956. Statistical Methods.
The Iowa State University Press, Ames, Iowa,
534pp.
Steel, R.G.D. and Torrie, J.H. 1980.
Principles and Procedures of Statistics, A
Biometrical Approach. Second Edition.
McGraw-Hill.
Sung, W. 1995. Some observations on surface
partitioning of Cd, Cu, and Zn in estuaries.
Environ. Sci. Technol. 29:1303-1312.
Thomann. R.V. and Mueller, J.A. (1987)
Principles of Surface Water Quality Modeling
and
.
Control. HarperCollins
Publishers
Inc,
New York, NY,644pp.
U.S. Environmental Protection Agency
(USEPA). 1983. Methods for Chemical
Analysis of Water and Wastes. EPA 600-4-79-
020.
U.S. Environmental Protection Agency
(USEPA). 1984. Technical Guidance Manual
for Performing Waste Load Allocations - Book
II Streams and Rivers -,Chapter 3 Toxic
Substances. EPA 440-4-84-022.
U.S. Environmental Protection Agency
(USEPA). 1991a. Technical Support
Document for Water Quality-based Toxics
Control. EPA 505-2-90-001.
U.S. Environmental Protection Agency
(USEPA). 1991b. Methods for the
Determination of Metals in Environmental
Samples. EPA 600-4-91-0.10.
U.S. Environmental Protection Agency
(USEPA). 1992. Guidelines for Exposure
Assessment; Notice. Federal Register
57(104):22888-22938.
U.S. Environmental Protection Agency
(USEPA). 1994a. Quality Control Supplement
for Determination of Trace Metals at EPA
Water Quality Criteria Levels Using EPA
Metals Methods. Engineering and Analysis
Division (4303), USEPA. Washington, DC
20460, December 1994.
U.S. Environmental Protection Agency
(USEPA). 1994b. Methods for the
Determination of Metals in Environmental
Samples. EPA 600-R-94-111.
U.S. Environmental Protection Agency
(USEPA). 1995a. Method 1669, Sampling
Ambient Water for Determination of Trace
Metals at EPA Water Quality Criteria Levels.
29
EPA 821-R-95034.
U.S. Environmental Protection Agency
(USEPA). 1995b. Guidance on the
Documentation and Evaluation of Trace Metals
Data Collected for Clean Water Act
Compliance Monitoring. Engineering and
Analysis Division (4303), Washington, DC
20460, December 1994.
U.S. Environmental Protection Agency
(USEPA). 1995c. Dynamic Toxics Wasteload
Allocation Model (DYNTOX). EPA 823-C-
95-005.
Zar, J.H. 1984. Biostatistical Analysis.
Second Edition. Prentice Hall„ NJ.
30
APPENDIX A
Deriving Permit Limits for Metals
T
his Appendix summarizes the
steps involved in applying the
dissolved metals policy and
illustrates how the translator is used in
developing a permit limit.
A.1?
The Setting for the Example
Our example site is a river which has
been identified as being water quality-limited
because o
•high
copper concentrations with
potential adverse impacts on aquatic life.
Copper loading
to
the impaired reach comes
from naturally occurring and anthropogenic
sources in the watershed (background) and
permitted point source discharges, including
two metal plating facilities and a publicly
owned treatment works (POTW). For the sake
of simplicity, steady-state modeling is used.
Episodic, precipitation-driven runoff loadings
from urban and industrial areas adjacent to the
river could be accounted for using continuous
simulation.
Design low flows are typically used for
calculating steady-state wasteload allocations
(WLAs), including the 1-day average low flow
with a ten year recurrence period (1Q10) for
acute criteria and the 7-day average low flow
with a ten-year
recurrence
period (7Q 10) for
chronic criteria. Analysis of 30 years of
records from the USGS gage above the sources
indicates a 1Q10 flow of 111.77 cfs and a 7Q10
flow of 140.09 cfs.
The two metal plating facilities in our
example have multiport diffusers, which have
been shown to quickly achieve complete
mixing across the width of the river. The
POTW effluent enters the same reach as the
facility discharges and
is
released
to
a bend in
the river where mixing also occurs rapidly. The
State's water quality regulations require that
water quality criteria are met at the edge of the
mixing zone.
A.2?
Water Quality Standards and
Criteria
Water quality standards consist of
criteria, designated uses, and an anti-
degradation statement. The river, in this
example, is classified as having designated uses
for aquatic habitat and primary contact
recreation (i.e., "fishable, swimmable"), and
the State has adopted the federal water quality
criteria into its water quality standards to
protect aquatic life and human health. The
numeric water quality criteria for acute toxicity
(criterion maximum concentration, or
CMC)
and chronic toxicity (criterion continuous
concentration, or
CCC)
to aquatic life are part
of the water quality standards and are based on
the dissolved
fraction
of metals. The CMC and
CCC
depend on ambient hardness
concentrations as expressed by the following
equation form (as total recoverable metal):
WQC meta =
exp
[a •
ln(H) +
b]
?
(1)
where
a
and
b
are metal-specific constants
defined as part of the water quality criterion.
For copper in freshwater systems, these
constants are:
Copper
a
b
Chronic Criteria
(i_ig/L)
0.8545
-1.465
Acute Criteria
(p.g/L)
0.9422
-1.464
31
At 100 mg/L hardness, these lead to a
CCC of 11.8 p,g/L and a CMC of 17.7 µg/L.
These criteria concentrations are expressed on
the basis of total recoverable metal (Box A-I).
A.3
?
Change from Total Recoverable to
Dissolved Criteria
As illustrated in Box A-1, each metal's
total recoverable criterion must be multiplied
by a
conversion factor
to obtain a dissolved
criterion that should not be exceeded in the
water column. The criteria are based on a total
recoverable concentration. For example, the
copper acute (and chronic) conversion factor.of
0.960 is a weighted average and is used as a
prediction of how much the final value would
change if dissolved had been measured. Where
possible, these conversion factors are given to
three decimal places as they are intermediate
values in the calculation of dissolved criteria.
At a hardness of 100 mg/L, the acute dissolved
criterion is 17.0 p.g/L. Most of the freshwater
aquatic life criteria and their conversion factors
are hardness-dependent. Box A-1 shows an
example calculation of dissolved and total
recoverable copper criteria concentrations.
A.4
?
Translating from a Dissolved Metal
Ambient Criterion to a Total
Recoverable Concentration in the
Effluent
As the effluent mixes with the
receiving water, the chemical properties of the
mixture will determine the fraction of the metal
that is dissolved and the fraction of the metal
that is in particulate form (typically adsorbed to
surfaces of other compounds). The most direct
approach to determining the fraction of the total
recoverable metal in the downstream water that
is dissolved (fi)is
to analyze the downstream
water (the mixing zone of effluent and
receivin g
water) to determine the dissolved and
total recoverable metal fractions. This ratio
Box A-1.?
Calculation of Acute (CMC)
and Chronic (CCC) WQC for Copper
Hardness (mg/L)
100
Conversion Factor
0.96
CMC
(total recoverable) (41-)
exp[.9422 x In(100) - 1.464] = 17.7
CMC(dissolved
)(p-g/L)
= 17.7 x .96 =
17.0
CCC
(total recoverable)(11g/L)
exp[.8545 x In(100) - 1.465] = 11.8
CCC(dissolved)
(1-tg/L) = 11.8 x .96 = 11.4
can then be used to
translate
from a dissolved
concentration in the water column (the criterion
concentration or some fraction thereof ) to the
total recoverable metal concentration in the
effluent that will equate to that dissolved
concentration in the water column.
A.5?
Calculation of WLAs for a Point
Source
For this example, it is assumed that the
site-specific data have been collected and
analyzed to determine that
1;,=
0.4.
From analysis of existing data, the
avera ge
background concentration of total
recoverable copper in the river at low flow
(upstream of the effluent discharge) is 4 .ig/L
and varies within a relatively small range, from
less than 2 to 9.5 .ig/L, with the average
declining to about 3 I_ig/L above median flows.
For this analysis the mean background
concentration is used.
The (instream) total recoverable
concentration [C,„„,„,„] that equates to the
dissolved criterion concentration is expressed
as:
[C instream ]?
WQC (dissolved)
?
(2)
Given the information on the design
flows and background concentrations (Box A-
2), WLAs, expressed as total recoverable
metal, are calculated to meet the dissolved
CCC and dissolved CMC at the edge of the
mixing zone assuming that the effluent is
mixed rapidly and that a simple, mass-balance
equation is appropriate.
Chronic and acute WLAs (for any
single source, without consideration of other
sources) can be calculated at the 7Q10 and
1Q10 flows, respectively, for total recoverable
copper concentration, using Equation 3.
WLA
(total mewl)o
[C„,„,,„„,] •
(Qe+Q,)
?
(3)
where [Ci„,„,a,„] is calculated from Equation 2,
Q, is the effluent flow,
Q, is the receiving water flow, and
C, is the background (upstream )
concentration.
42.5 • (50+111.77) - 111.77
?
4
WLA
II
-
50
= 128.6
t.
,
grIL total recoverable Cu
(4)
A.6
?
?Calculating
the TMDL for Multiple
Point Sources
The previous section shows the
calculation of wasteload allocations for a
single point source. Concentrations in the
receiving water, however, are influenced by
all three point sources simultaneously. In
other words, the full assimilative capacity of
the water body is not available to each source;
instead, this capacity must be apportioned
between all three sources via the TMDL
procedure.
The three permitted point sources in
our example all operate within the effluent
limits specified in their current NPDES
permits. They do not, however, address
cumulative impacts of all three sources.
Permits for the two metal finishing facilities
specify a maximum daily limit (MDL) of
3380 [ig/L and an average monthly limit
(AML) of 2070 .tg/L.
?
•
In addition to potential impairment
under current permit limits, the POTW is
undergoing a significant (60%) capacity
expansion, and its increased effluent flow will
also increase copper loading at current
effluent concentrations. At an average.
concentration of 81 u.g/L of total recoverable
copper and an increased effluent flow of 80
cfs, the load from the POTW (see Box A-3)
would be 35 lbs/day. The increased flow
from the plant also has a si
gnificant impact on
low flow volumes in the receiving water,
requiring recalculation of the WLAs.
The TMDL analysis is
straightforward when multiple, steady-state
sources are considered using hydrologically
based design conditions. The strategy is to:
Box
A-2.
Data for Calculation of WLAs
and Existing Permit Limits
for the POTW
Effluent Flow (cfs)
?
50
Average Effluent Concentration,
as Total Recoverable Copper (p.g/L)
?81
Coefficient of Variation of Load
?0.12
33
Box A-3. Conversion Factors for
Concentration and Load
Concentration to load rate:
(ii.g/L) x (cfs) x 0.005394 = (lbs/day)
Load rate to concentration:
(lbs/day) / (cfs) x
185.4
= (i_tg/L)
.
(1) calculate the acute and chronic dissolved
(for metals) criteria concentrations [Eqn 1],
(2)
calculate the instream concentration
[C
instream] (in terms of total recoverable metal)
that equates to the dissolved criterion
concentration [Eqn 2],
(3)
calculate the total loading capacity
(TMDL) of the waterbody (in terms of total
recoverable metal) [Eqn 6],
(4)
calculate the background load,
(5)
calculate the allocatable portion of the
loading capacity (i.e., the difference between
the loading capacity and background) [Eqn 7],
(6)
calculate the current loadings from the
sources and their fractional contributions to
the total current load,
(7)
compare the current total loadings to the
waterbody with the required TMDL (if either
the acute or chronic total loadings exceed the
TMDL then the loads must be reduced), and
(8)
reduce loadings from the point sources,
equitably allocating waste loads to the
discharging facilities.
The steady-state TMDL for a given
location or reach of the river is calculated (in
units of cfs - p.g/L) as:
TMDL = WQC • (EQe
+Qs)?
(5)
where
Q, is the total flow of effluents
discharging to the reach (cfs),
Qs is the appropriate flow (e.g.,
7Q10) of the river upstream of all the
discharges (cfs), and
WQC is the water quality criterion
expressed in i_tg/L.
TMDLs for metals are developed on
the basis of the instream total recoverable
metal concentrations that equate to the
dissolved criteria concentrations.
Consequently, the term WQC in Equation 5 is
replaced with the term [C,„,,„,„" as calculated
by Equation 2.
TMDL = [
Cinstrecim
] (EQe+Qs)
?
(6)
The calculated TMDL is then divided
among WLAs for point sources; LAs, for
nonpoint sources and background loads; and a
margin of safety (MOS). The TMDL and the
portion of the TMDL taken up by background
load (at 4
I.L2/1_.)
can be calculated in terms of
total copper mass, as shown in Table A-I.
Because the current loading for the
chronic TMDL exceeds the allocatable
portion, loadings from all of the NPDES
permitted sources must be reduced. Many
different mechanisms or schemes for
apportioning the necessary reductions in
allocations are possible. Assume for the
purpose of this example that the State has
determined that necessary reductions will be
applied equally to all point sources. Reduced
TMDL-based WLAs can then be calculated
based on the current proportion of load
attributable to a given source:
WLA = [TMDL - Background] x
(7)
where WLA, is the WLA for
source I,
and
f,
is the proportion of the existing load
attributable to a given source.
The allocation fraction, f, is simply a
proportionality constant that is arrived at by
dividing the current load from
source,
by the
sum of all the loads (e.g.,
fl =
PSI / (PSI +
PS2 + POTW + MOS)). The allocation
fraction is then multiplied by the Allocatable
Portion to yield the Allowed Load as in Table
A-2. In the calculations summarized in Table
A-2 and A-3, a MOS of 10 percent of the
allowable TMDL has been applied.
35
Table A-1.?
Calculation of TMDL (Total Recoverable Copper)
Acute TMDL
Chronic
TMDL
TMDL
(total recoverable copper)
(lbs/day)
[Eqn 6]
44.11
33.76
Background
(total recoverable copper)
at design flow (lbs/day)
[Background =
Q.
*
Cs]
2.41
3.02
Allocatable Portion (lbs/day)
[Allocatable Portion
=
TMDL - Background]
41.69
30.73
Current Loading (lbs/day)
[1,oading =
PSI +
PS?
+
POTW +Rackpround]
42.38
42.99
Table
A-2.?
Allocation
of Loads to
Achieve the (Chronic) TMDL
Source
Current Load
(lbs/day)
Allocation
Fraction
(f)
Allocatable
Portion
(TMDL -
Background)
Allowed Load
(lbs/day)
PSI
1.67
0.04
30.73
1.16
PS2
3.35
0.08
30.73
-)
—.3—--)
POTW
34.95
0.79
30.73
24.18
MOS
4.44
0.10
30.73
3.07
SUM
44.41
1
30.73
36
Table A-3.?
Allocation of Loads to Achieve the (Acute) TMDL
Source
Current Load
(lbs/day)
Allocation
Fraction
D
Allocatable
Portion
(TMDL - Background)
Allowed Load
(lbs/day)
PSI
1.67
0.04
41.69
1.57
PS2
3.35
0.08
41.69
3.14
POTW
34.95
0.79
41.69
32.81
MOS
4.44
0.10
41.69
4.17
SUM
44.41
1
41.69
37
A.7 Calculating
the Permit Limits for a
Point Source
Permit limits for the POTW are
developed in accordance with USEPA
(1991a) guidance on establishing WLAs and
permit limits for single sources. In
accordance with NPDES regulations, effluent
Box A-4. Calculation of LTA
Multipliers
LTA,
CV = 0.12
z
99
= 2.326
0
2
4 =
In [CV
2
/4+1] = 0.00359
exp [0.5
02 4 - Z 99 0
4]
= 0.87
LTAa
CV = 0.12 •
z
99
= 2.326
02
= In [CV
2
+1] = 0.014297
exp [0.50
2
-
z
99
a] = 0.76
limits for the POTW are expressed in the
permit as mass units (pounds per day total
recoverable copper), using the conversion
factors shown in Box A-3. The WLA , for
total recoverable copper (Table A-2) is
equivalent to 24.18 lbs/day and is more
restrictive than the WLA
;
, 32.81 lbs/day
(Table A-3). Converting the WLA to a
permit limit involves two additional
considerations: (1) there is variability in the
effluent concentration, and concentrations on
any given day may be greater or less than the
avera ge
value used to calculate the WLA; and
(2) permit compliance will be assessed from
limited sampling (e.g., weekly), which means
there will be uncertainty in the estimation of
actual load from the facility. These issues are
addressed by (1) calculating a
long-term
average
(LTA) which accounts for the
variability in actual load, and (2) using the
LTA to calculate a
maximum daily limit
(MDL) and
average monthly limit
(AML)
which serve as trigger values for compliance
monitoring.
The permit limits are developed using
a steady-state, two-value WLA model, as
described in Chapter 5 of USEPA (1991a).
First, variability in effluent load,. expressed
through the coefficient of variation (CV), is
incorporated into the calculation of
appropriate long-term averages (LTAs). The
chronic long-term average (LTA „) for copper
was calculated from
LTA
,
= WLA •
exp [0.5024-z9904]
= 24.18
lbs/day •
0.87
(9)
= 21.0
lbs/day
where the value for the factor exp [0.5 02–
z99
04]
was calculated from the coefficient of
variation of effluent concentrations (CV,
defined as standard deviation divided by the
mean, and assumed to be 0.12) by the
methods of USEPA (1991a. Table 5-1), using
the 99th percentile occurrence probability
(Box A-4).
The acute LTA„ was calculated in a
similar manner, again usin
g
a 99th occurrence
probability as a multiplier:
LTA, =
32.81
lbs/day •
0.76
= 24.9
lbs/day
(10)
38
The limiting LTA for copper discharges from
the facility is the smaller of the LTA
a and
LTA
c
, or 21.0 lbs/day. This is well below the
current average load from the facility of 43.95
lbs/day.
The permit for the POTW is written
to ensure an LTA load not to exceed 21.0
lbs/day total recoverable copper through the
specification of an MDL and AML for
compliance monitoring. The MDL for copper
is calculated using the expression
MDL = LTA •
exp [z99 a - 0.5 021
= 21.0
lbslday •
1.37
= 28.8
lbs/day
where the value for exp [z99
a - 0.5 02] is
taken from Table 5-2 in USEPA (1991a),
using a CV value of 0.12 and the column for
the 99th percentile basis. The AML for
copper is calculated from
AML = LTA •
exp [z99
a
?
o-,2,]
= 21.0
lbsIday •
1.15
?
(12)
= 24.2
lbsIday
where the value for exp [z
99
0,, - 0.5
on
2]
is
taken from Table 5-2 in USEPA (1991a), in
which
n
equals 4 samples per month for total
recoverable copper, using the 99th percentile
basis.
39
APPENDIX B
Table B-1.
?
Comparison of average
?
data from three locations in the
U.S.
Three different
calculation methods are used with the Pima County data.
NY/NJ
Harbor
Boulder,
CO
Pima County, AZ
Cd/Ct
Cd/(Cd+Cp)
by regression
from logKp
Copper
0.56
0.23
0.37
0.43
0.42
Cadmium
1.00
0.51
0.71
0.51
0.69
Lead
0.18
0.29
0.20
0.28
0.26?
.
Nickel
0.86
— 1.0
---
---
---
•
Zinc
0.90
0.44
0.61
0.63
0.65
These data illustrate two points. First,
notice the similarity in the values of the
translators for each of the metals in the Pima
County study. The differences between
column 1 and column 2 of the Pima County
data arise from limits in the analytical
precision of measurements of dissolved and
particulate sorbed fractions. Second, notice
the differences in the values of the translators
between the three sites represented in this
table. These differences reflect the site
specificity of the translator, further
strenzhing the case for development of site
specific translator values in contrast to the use
of nation wide values.
Preliminary data collected for the
City of Palo Alto Regional Water Quality
Control Plant permit renewal process (Table
B-2) suggest a translator value of 0.62 for
copper (62% of the copper in the downstream
water is dissolved). This differs from all of
the translator values in Table B-1.
40
Table B-2.?
Data Collected in Palo Alto, CA for Cu Permit Limit from a Waste Water
Treatment Plant.
Station#
Date
Cd
Ct
Cp
TSS
fD
Station 1
9/7/89
2.6
3.4
0.8
89
0.76
Station 1
10/2/89
3.3
4.5
1.2
290
0.73
Station 1
10/25/89
3
4
1
52
0.75
Station 1
1/10/90
2.9
4.1
1.2
49
0.71
Station 1
2/7/90
1.4
8
6.6
228
0.18
Station 1
3/7/90
3
5
2
77
0.60
Station 1
7/9/90
4.2
9.6
5.4
180
0.44
Station 1
8/7/90
6.3
7
0.7
83
0.90
Station 1
9/19/90
3.6
5.7
2.1
125
0.63
Station 1
12/12/90
2.9
?
.
5.9
3
57
0.49
Station 1
1/10/91
3.5
4.3
0.8
46
0.81
Station 1
2/13/91
4
4.7
0.7
55
0.85
Station 1
10/10/91
4.3
4.6
0.3
78
0.93
Station 1
2/19/92
2
9.9
7.9
250
0.20
Station 2
9/7/89
3
5
2
110
0.60
Station 2
10/2/89
2.2
4.5
2.3
160
0.49
Station 2
10/25/89
6
11
5
132
0.55
Station 2
1/10/90
2.9
4.1
1.2
.
?
46
0.71
Station 2
2/7/90
1.7
6.1
4.4
110
0.28
Station 2
3/7/90
4.3
5
0.7
60
0.86
Station 2
7/9/90
6.8
7.2
0.4
100
0.94
Station 2
8/7/90
6.5
8.2
1.7
48
0.79
Station 2
9/19/90
3.9
5.6
1.7
65
0.70
Station 2
12/12/90
2.8
4.6
1.8
51
0.61
Station 2
1/10/91?
4.2
4.8
0.6
61
0.88
Station 2
2/13/91?
4.5
4.8
0.3
47
0.94
Station 2
10/10/91
?
I
?
4.5
4.7
0.2
77
0.96
Station 2
2/19/92?
2
4.9
2.9
120
0.41
Mean
3.7
5.8
2.1
101.6
0.67
Stdev
1.4
2.0
2.0
65.5
0.22
95%
6.4
9.8
6.2
243.4
0.94
25%
2.9
4.6
0.7
54.3
0.53
Geomean
3.4
5.5
1.4
86.6
0.62
41
APPENDIX C
C.?
Developing the Metals Translator
s may be concluded from the
discussion in Chapter 2,
there are several ways of
develop ng the metals translator. This
Appendix presents two suggested possibilities
and illustrates their application.
C.1. Minimum Data Requirements
Samples should be collected to'
characterize completely mixed effluent plus
receiving water downstream of the discharge
(such as should occur at, or below, the edge
of the mixing zone). These represent the
absolute minimum in data requirements.
Ideally, samples should be collected from the
effluent and the upstream receiving water
(before mixing with the effluent) to quantify
metal loading and background
concentrations. An alternative to collecting
the downstream samples on site is to combine
upstream and effluent waters to meet the
desired dilution fraction in the mixing zone.
In addition, there may be occasions when it is
desirable to collect samples to characterize
the far-field conditions, particularly when
encountering deposits containing metals, mine
tailings, drainage waters of high acidity, or
different geologic substrates.
To keep this simple and to avoid
having to develop data on the kinetics of
metal adsorption and desorption, the translator
should be developed to describe equilibrium
partitioning. Equilibrium partitioning also
reduces the frequency for which far field
effects need to be investigated. It also lets us
apply the same translator for evaluation of
both acute and chronic mixing zones.
C.2.
?
The Translator is
the Ratio of
CD/CT
The translator is the fraction of the
total recoverable metal in the downstream
water that is dissolved ( fD
= CD/C7.).
It is
calculated from data collected over some
period of time arid some range of flow
conditions. For example, samples may be
collected weekly for three months under
conditions of "relatively low flow" (which
may or may not include design low flow
conditions) or samples may be collected
monthly for a period of one or more years
under a broad range of flow conditions.
Under this latter sampling scheme we may
expect to have a broad range of TSS
conditions. The dissolved fraction may be
determined (directly) from measurements of
dissolved and total recoverable metal
concentrations collected from waters
downstream of the effluent discharge. The
dissolved fraction may be related to a constant
adsorbent concentration associated with low
flow conditions or a function of varying
adsorbent concentrations.
Note that this ratio
(C
7.),
as
exemplified by Eqn 2.6 and 2.7, is not a
partition coefficient but it does embody a
partition coefficient. As shown by Eqn 2.3
and Eqn 2.8, the partition coefficient is the
ratio of the particulate-sorbed and the
dissolved metal species. The dissolved
fraction and the partition coefficient are
related accordin
g, to f p = 1 +
?
• m)
-I
. It is
important to distinguish between the dissolved
fraction (fD)
and the partition coefficient (K
p)'
because what we're interested is the dissolved
fraction. We're only usin
g
the partition
coefficient because it is one way of getting to
the dissolved fraction.
This guidance uses TSS as a default
parameter to represent all of the ion
adsorption sites.
It
is generally recognized,
however, that humic substances play a major
A
42
Box C-1. The Translator is the Dissolved
Fraction: fp
=
CD/CT
Step 1 - For each field sample determine
fD = CD/CT
Step 2 - If the translator i§ not dependent
on TSS, determine the. geometric
mean
GM_fD=
exp(E," In(fD )/ n)
and upper percentile values of the
dissolved fraction. If the data are
found not to be log-normal, then
alternative transformations should
be considered to normalize the
data and determine the
transformed mean and percentiles.
Also, alternative upper percentiles
may be adopted as a state's policy
to address MOS (e.ge., 90 or 95th
percentiles may be appropriate.)
Step 3
If the translator is found to be
dependent on TSS, regression
equations relating f p
to TSS should
be developed. Appropriate
transformations should be used to
meet the normality assumptions
for regression analysis (for
example log-transformation off
and TSS may be appropriate). The
regression equation or an upper
prediction interval may be
considered for estimation of f
from TSS depending on the
strategy for addressing MOS.
role in the environmental fate and availability
of metal ions in the environment. The humic
and fulvic acids are mixtures of naturally
occurring polyelectrolytes that have different
types of functional groups to which ions can
bind. Benedetti, et. al. (1995) write that metal
binding in natural systems will be affected by
humic acids whose chemical heterogeneity
and polyelectric properties will affect metal
binding. Multivalent cations will compete for
the same sites, along with other ions and
protons in the aquatic systems, and hence
influence the binding of each other.
The following step-by-step examples
are designed to guide the reader through
possible sequences of data analyses leading to
the development of the metals translator. One
set of data was collected during the New
York/New Jersey Harbor study. The data
presented here are a subset of the total and do
not include samples that are incomplete (i.e.,
records lacking pH or POC values) to
simplify this presentation. The data set
reflects spatial differences. The data are not a
time series at a single location. However,
there would not be a great difference in the
following analyses if the data did represent a
time series.
The second data set was provided by
the Coors Brewing Company. Again, the data
presented here are a subset of the total. The
original data set contains time series data for
several variables at several locations. To
simplify this example, however, the data for
only one metal and one site are presented.
C.2.1.
Spatial Example Using the Ratio of
CD/CT
The most direct procedure for
determining a site-specific metal translator is
simply to determine f
0
by measuring C T and
C
D and to develop the dissolved fraction as
the ratio C
D/C T This is illustrated, using data
from Table 1 and following the sequence as
outlined in Box C-1. The metal
concentrations in Table I are for lead. The
data records, numbers 1 through 27, repregmt
spatially separate sampling stations in th•
estuary. The first step (Step 1 in Box C?
is
to calculate the dissolved fraction in the
receiving water. The result of this calculation
is shown in Column 8 of Table I.
43
Lead
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
0
*
40
•
4*
w
•
•
•
0
20?40
TSS
Lead
0.70 -
0.60 -
0.50 -
0.40 -
0 0.30
0.20 -
0.10
0.00 -
-0.10
-1.00
?
?0.00
?
1.00?
2.00
?
3.00
?4.00
in (TSS)
?
R-Square = 0.77
Step 2 indicates that there is a lot of
variation in the values of f
p
; the mean is 0.21
with a standard deviation is 0.17. The
variability in this dataset indicates that it is
unwise to attempt to spatially average f 0
values in this situation. To do so would be to
ignore spatially critical conditions. Because,
it does not provide a good representation of
the waterbody, one cannot accept the mean f
D
(0.21) as the translator.
The translator should be calculated as
a geometric mean or other estimate of central
tendency (see Section 4.3). Use of the
arithmetic mean is appropriate when the
values can range from minus infinity to plus
infinity. The geometric mean is equivalent to
using the arithmetic mean of the logarithms of
the values. The dissolved fraction cannot be
negative, but the logarithms of the dissolved
fraction can be. The distribution of the
Figure 1.?
Dissolved fraction (lead) vs TSS.
transformations would be appropriate.
Examination of Figure 2 further supports the
logarithmic transformation of values and the
choice of the geometric mean. Even at that,
the geometric mean value of the dissolved
fraction (0.16 does not provide a good
representation of the waterbody in which TSS
is spatially correlated.
The translator needs to
account for the spatial-and/or temporal
variability evidenced in the waterbody.
In order to account for the spatial
variability of.this waterbody, we need a
translator that can be tied functionally to
important physical or chemical variables.
TSS concentrations vary spatially throughout
the estuary. Spatial variability in TSS
concentrations requires the use of a translator
that includes the relationship between TSS
and fp
. This empirically derived relationship
is valid for this estuary.
Figure 2.?
Dissolved fraction (lead) vs log
transformation of TSS.
logarithms of the translator is therefore more
likely to be normally distributed. Figure 1
displays the arithmetic distributions of the
dissolved fractions with TSS. Note that the
skewed distributions su ggest
that logarithmic
The regression of the natural
lo garithm of fp
-against the natural logarithm
of TSS (Figure 2) provides a reasonably good
fit as evidenced by the R Square of 0.77. The
44
dissolved fraction is highly correlated with
TSS; therefore the translator (Figure 2) takes
the form of:
In(fD)= - 0.6017 - 0.6296 • ln(TSS).
The translator is the dissolved
fraction, not the regression equation. The
way to use the regression equation is to select
TSS concentrations that are representative of
specific locations in the estuary and calculate
fp
values that serve as the translators for the
discharges in these respective locations.
Sung, et.al. (1995) have demonstrated
a relationship between K
p
and salinity for Cd,
Cu, and Zn in the Savannah River Estuary. It
may well be that by considering salinity as
well as TSS, more variability could have been
accounted for in the relationship portrayed in
Figure 2.
45
Table C-1. Example Data Used to Calculate Translator for Lead
(Source: NY/NJ Harbor Study)
No.
pH
POC
TSS
- Cr
CP
fb?
KP
(CT/CD)-1
1
8.8
0.132
0.61
0.046
0.027
0.019
0.59
1.15
0.704
2
8.6
0.104
0.92
0.044
0.03
0.014
0.68
0.51
0.467
3
8.6
0.159
1.88
0.25
0.094
0.156
0.38
0.88
1.660
4
8.4
0.280
128
0.31
0.16
0.15
0.52
0.73
0.938
5
8.4
0.376
3.32
0.68
0.10
0.58
0.15
1.75
5.800
6
8.4
0.190
2.94
0.46
0.098
0.362
021
126
3.694
7
82
0.183
5.36
0.89
0.14
0.75
0.16
1.00
5.357
8
8.3
0.351
4.71
0.80
0.27
0.53
0.34
0.42
1.963
9
8.4
0.266
3.50
0.67
022
0.45
0.33
0.58
2.045
10
8.1
0.416
7.98
.
2.40
0.59
1.81
• 0.25
0.38
3.068
11
8.1
1.060
44.42
9.10
027
8.83
0.03.
0.74
32.704
12
8.1
0.538
11.08
3.40
0.44
2.96
0.13
0.61
6.727
13
8.1
0.596
10.60
3.90
0.85
3.05
02 1?
0.34
3.588
14
8.2
0.785
14.77
320
0.54
2.66
0.17
0.33
4.926
15
8.4
0.626
8.95
1.40
0.26
1.14
0.19
0.49
4.385
16
8.4
0.602
19.94
220
0.17
2.03
0.08
0.60
11.941
17
8.3
0.540
21.10
2.10
0.14
1.96
0.07
0.66
14.000
18
8.3
0.676
19.45
2.10
0.15
1.95
0.07?
0.67
13.000
19
8.2
0.629
25.70
2.90
0.15
2.75
0.051?
0.71
18.333
20
8.4
0.726
27.75
1.90
0.16
1.74
0.081?
0.39
10.875
21
8.4
0.494
22.30
1.50
0.17
1.33
0.111?
0.35
7.824
22
8.4
2.360
7.89
1.40
0.26
1.14
0.19!?
0.561?
4.385
23
8.4
0.427
7.32
1.70
0.22
1.48
0.131
?
0.92
6.727
24
8.4
0.414
8.48
1.60
0.27
1.33
0.171
?
0.581
?
4.926
25
8.51?
1.470?
8.22 1.20
0.10 1.10
0.08?
1.34?
11.000
215
8.5 0.4071
?
7.091
?
0.82 0.088 0.732
0.11?
1.17?
8.318
27
8.6 0.3811?
7.52
?
0.58
0.065 0.515
0.11?
1.05?
7.923
Mean
0.561?
11.30
1.76
0.22
1.54
0211?
0.75?
7.31
Stdev
0.461
1023
1.80
0.19
1.72
0.171?
0.36
6.77
95%
1.35
27.14
3.75
0.58
3.02
0.57'?
1.31
17.03
25%
0.32
4.11
0.68
0.10
0.52.?
0.101?
0.50
3.33
Geomean
0.441
?
7.261
?
1.061 0:17,
0.82!
?
0.16'
?
0.67
?
4.90
46
Table C-2.
Time Series Example Calculating the Translator for Zinc.
(Source: Coors Brewing Company Study)
DATE
pH
TSS
CT
CD
(CT/CD)- 1
fD
10/16/91
7.5
3
0.47
0.24
0.96
0.51
11/13/91
.7.3
32
0.72
, 0.27
1.67
0.38
. 12/11/91
8.1
5
0.47
0.20
1.35
0.43
01/16/92
8.2
8
0.43
0.38
0.13
0.88
02/18/92
8.2
7
0.55
0.19
1.86
0.35
03/18/92
8.1
7
0.49
0.24
1.07
0.48
04/14/92
7.2
14
0.84
0.44
0.92
0.52
05/12/92
7.7
15
0.34
0.18
0.87
0.54
06/17/92
7.5
8
0.25
0.15
0.64
0.61
07/15/92
7.5
5
0.18
0.13
0.43
0.70
08/18/92
7.2
23
0.26
0.08
2.12
0.32
09/09/92
7.2
4
0.22
0.03
5.72
0.15
10/14/92
8.0
7
0.25
0.11
1.27
0.44
11/16/92
8.2
13
0.44
0.22
1 .00
0.50
12/15/92
7.9
1
0.47
. 0.24
0.97
0.51
01/12/93
8.8
6
0.67
0.32
1.08
0.48
02/18/93
7.9
12
0.71
0.38
0.87
0.54
03/16/93
8.1
10
0.57
0.22
1.58
0.39
04/13/93
8.0
18
0.48
.- 0.16
2.04
0.33
05/12/93
7.5
20
0.42
•?
0.08
4.10
0.20
06/15/93
8.1
64.6
0.54
0.10
4.67
0.18
07/15/93
•
7.5
. 10
0.14
0.06
1.25
0.44
08/12/93
7.8
6
0.17
0.09
0.94
0.52
09/16/93
8.1
4
0.24
0.12
1.09
0.48
10/13/93
8.1
5
0.26
0.12
1.11
0.47
11/10/93
8.4
1.7
0.30
0.15
1.03
0.49
12/13/93
7.9
4.6
0.45
0.23
1 .00
0.50
01/13/94
7.5
1.8
0.33
0.17
0.97
0.51
02/11/94
7.91 5.5
0.49
0.24
1.01
0.50
03/09/94
8.41
5
0.34
0.09
2.57
0.28
04/07/94
8.3
16
0.48
0.14
2.54
0.28
05/12/94
7.6
47.7
0.72
0.09
7.35
0.12
07/13/94
7.8
6
0.13
0.05
1.43
0.41
08/23/94
8.0
13
0.14
0.05
2.20
0.31
09/20/94
8.1
61
0.15
0.06
1.30
0.44
10/18/94
8.0
5.5 0.28
0.14
1.06
0.49
Mean
11.68 0.40
0.17
1.73
0.43
Stdev
12.90 0.19
0.10 1.50
0.15
95%
0.71 0.71
0.33 0.71 0.71
25%
5.001 0.25
0.091 0.971 0.34
Geo mean
1
1
7.901 0.351 0.14 1.331 0.40
47
C.2.2. Time Series Example Using the
Ratio of CD/CT
Using a data set developed over a
three year time span on Clear Creek in
Colorado and the same analytical procedure
as described in Box 1. f
p
is calculated as the
ratio of C
D/C T
. A subset of the collected
data, Table C-2, illustrate the approach.
This subset includes the following
variables: total recoverable Zn, dissolved Zn,
TSS, and pH that were measured at one
sampling location. Additionally, presented in
Table 2 are fp values (Box C-1 - Step 1).
This data set was censored in the following
manner. When calculating
fo, if
the dissolved
concentration was found to exceed the total
recoverable concentration, C „was set equal
to
C.
and fry calculated as 1 (100% dissolved
metal).
At the pH levels encountered in Clear
Creek during the three year sampling period,
no relationship was obtained between pH and
fD . This is not an unexpected result because
pH is in the 7 to 9 range; the major effect of
pH on the dissolved fraction is normally
observed at low pH levels. Relationships
based on POC (not shown) provide no
improvement over the TSS based
relationships.
The translator value selected for Zn
on Clear Creek is the ir4eometric mean of the
I'D values (0.40).
C.3.?
The Translator Calculated Using
Site Specific Partition Coefficients
It is important to remember with this
method, as with the previous method, that the
translator is the dissolved fraction in the
downstream water.
Box C-2 provides a procedure for developing
the translator via partition coefficients. In
Step
I
calculate the particulate fraction, the
partition coefficient, and the dissolved metal
Box C-2. The Translator is the
Dissolved Fraction (fD)
Calculated via Site Specific
Partition Coefficients
Step 1 For each field sample
determine
Cp
CT - CD
KP •Cp/(C
p • TSS)
Step 2 - Fit least squares regressions to
data (transformed, stratified by
pH, etc.) as appropriate to
solve for Kp.
Step 3 - Substitute the regression
derived value of Kp in Eqn 2.7,
fp = (1 + Kp • TSS)-'
Step 4 Determine f
p for a TSS value
representative of the critical
conditions.
fraction. C p is calculated as the difference''
between total recoverable and dissolved
metal concentrations. The partition
coefficient the ratio of the particulate-sorbed
and the dissolved metal species times the
adsorbent concentration (Eqn 2.9). The
17
The particulate fraction can also be
measured in the laboratory by filtering the solids,
scraping the solids from the filter, drying,
weighing, and subjecting to appropriate chemical
analyses. The increased number of steps may
provide opportunities for additional sources of
error, accompanied by increased uncertainty. See
Eqn 2.2. 2.3, and 2.4.
48
1.800?
• •
1.600 -
1.4001400-
1.200-
1,000-
•
•
0.800-i
0.600
?
••
0.400
0.200
0.000
-
-
••
-?
•
4
,
•
•
•
?•
•
•
0
10
20
30
40
50
TSS?
R-Square = 0.11
dissolved fraction and the partition
coefficient are related according to Eqn 2.7.
C.3.1. Spatial Example Using Partition
Coefficients'
Using the same NY/NJ Harbor data
as used above (Table C-1), this example
Figure 3. Kp
as a function of TSS.
demonstrates the calculation of K
p and how it
may be used to arrive at site-specific values
of fp .
The partition coefficient - TSS data
are not as well behaved (Figure 3) as are the
f
p
-TSS data. However,
Shi,
et. al. (1996)
show that after algebraic rearrangement of
Eqn 2.7 to
(Ct/Cd)-1 = K
p •
TSS.
K
p
can be obtained by linear regression. The
slope of the curve is the partition coefficient
(Figure 4).
Figure 4.
?
The fraction [(Ct/Cd)-1] as a
• function of TSS.
By regression analysis, K
p = 0.624
L/mg. This value is used in Eqn 2.7 along
with an appropriate value of TSS to calculate
the translator.
C.3.2. Time Series Example Using
Partition Coefficients
Continuing the analysis of data
collected from Clear Creek, this section
demonstrates estimating the dissolved
fraction by using a site-specific partition
coefficient. The particulate sorbed fraction is
operationally defined as
C
T
-
C
D and the
partition coefficient is calculated as a
function of TSS according to Equation 2.8
following the procedure given in Box 2 - Step
1. Table C-2 presents the data generated by
the field study as well as the calculated
values.
Substitute the regression derived
value of K r
in Eqn 2.7, as suggested in Box 2
- Step 3. As in the previous example, the
way to use this equation is to select TSS
concentrations that are representative of
Lead
49
critical conditions in the receiving waterbody
and calculate the dissolved fractions
(translator values) .
Figure 5. The
fraction [(Ct/Cd)-1] as
a function of TSS.
50
APPENDIX D
D.1. Sample Size
S
tatistically, the most
important objective for a
metal translator study is to
determine the mean concentrations of total
and dissolved metal within an acceptable
confidence interval of the true mean such that
the estimated dissolved fraction is a good
representation of the true dissolved fraction.
The null hypothesis (H
o)
is:mean
total concentration (i,t,)= mean dissolved
concentration (i.,cd)..
To determine sample size, three
factors must be selected:
1.
Type 1 error (a) is the probability of
rejecting a true hypothesis.
2.
Type II error ((3) is the probability of
accepting a false hypothesis.
3.
The expected difference between the
means (A), expressed as a multiple of
the standard deviation (a), which is
assumed to be equal for the two
populations (a = a, = a„):
A = (pct- /-td) –
For a translator study, the null
hypothesis is assumed to be false, i.e., there
is a difference between total and dissolved
concentrations. Therefore, (3 must be small
to ensure that a translator is not rejected (no
difference detected between the means) when
a difference does exist. For a and p levels of
0.05. the following shows the relationship
between A and n. assuming a t distribution:
al?
A?
n
0.05?
0.05?
1.0?
27
2.0?
8
?
3.0?
5
?
4.0
?
4
A sample size of 4, therefore, would
determine that a difference exists only if the
difference between the means is 4 a or more.
At very low concentrations typical of many
metals—for example, if the dissolved copper
concentration is 3 i_tg/L and the total
concentration is 6
i..ig/L
and a is 1 ktg/L—this
sample size would not be adequate to
demonstrate that a difference exists. The
translator would be rejected
.
, therefore, even
though it is actually valid. A sample size of
8, on the other hand, would be large enough
to show a difference between the two means
and support the use of a translator other than
1.
A sample size of 10 (or greater) is
recommended because it would allow
demonstration of a significant difference for
A somewhat less than 2.0, while still keeping
a = 13 = 0.05. Furthermore,.if 1 or 2 samples
have to be discarded because of undetectable
concentrations, outlier concentrations, or
other sampling or analytical problems, there
would still be an adequate number of samples
to meet the assumed statistical criteria. The
only really reliable method of estimating how
many samples are going to be needed is to
collect some data, examine the statistical
variability, and project from that basis.
51
•
APPENDIX E
E.1.
?
Topics covered in Method 1669
include:
ontamination control,
includin g : minimizing
exposure of the sample, the
wearing of gloves, use of metal-free
apparatus, and avoiding sources of
contamination.
Safety, including: use of material
safety data sheets and descriptions of
the risks of sampling in and around
water and in hot and cold weather.
Apparatus and materials for
sampling, including: descriptions and
part numbers for sample bottles,
surface sampling devices such as
poles and bottles, a subsurface jar
sampling device, continuous flow
samplers including peristaltic and •
submersible pumps, glove bag for
processin
g
, samples. gloves, storage
bags, a boat for collection of samples
on open waters, filtration apparatus
consistent with the apparatus studied
and used by USGS. and apparatus for
field preservation of samples.
Reagents and standards for sample
preservation, blanks, and for
processin
g samples for determination
of trivalent chromium.
Site selection
Sample collection procedures,
including: "clean hands/dirty hands"
techniques, precautions concerning
wind direction and currents, manual
collection of surface and sub-surface
samples. depth sampling using a jar
sampler, and continuous flow
samplin
g using a pump.
Field filtration and preservation
procedures using an inflatable glove
bag, and instructions for packaging
and shipment to the laboratory.
Quality assurance/quality control
procedures, including: collection of
an equipment blank, field blank, and
field duplicate.
Re-cleaning procedures for cleaning
the equipment and apparatus between
sites.
•
Suggestions for pollution prevention
and waste management.
Twenty references to the technical
literature on which the Method is
based and a glossary of unique terms
used in the Method.
Table E-1 details some of the
differences between standard sampling for
metals and sampling for trace metals using
the procedures outlined below and detailed in
Method 1669.
52
Table E-1.
?
Standard vs. Trace Metals Sampling
Component
Standard Sampling Technique
Trace Metals Sampling
(USEPA, 1983, 1991b)
Technique (USEPA, 1995a)
Bottles
Borosilicate glass,
polyethylene, polypropylene, or
Fluoropolymer, polyethylene,
or polycarbonate, filled and
Teflon ®
stored with 0.1% ultrapure HCI
solution
Cleaning
Wash with detergent; rinse
Detergent wash, DI water
successively with tap water, 1:1
rinse, soak for 2 h minimum in
HNO3
, tap water, 1:1 HC1, tap
hot, concentrated HNO
3 ,
DI
water, deionized distilled water
water rinse, soak for 48 h
(GFAA methods; EPA, 1983).
minimum in hot, dilute
•
Soak overnight; wash with
detergent; rinse with water;
ultrapure HCI solution, drain,
fill with 0.1% ultrapure HCI
soak in FINO
3
:HChwater
solution, double bag, and store
(1:2:9); rinse with water; oven
dry (ICP Method 200.7;
until use.
USEPA, 1991b)
Gloves
No specification.
Powder-free (non-talc, class-
100) latex, polyethylene, or
polyvinyl chloride.
Filter
0.45 1.1M membrane; glass or
Gelman #12175 capsule filter
plastic filter holder
or equivalent capacity 0.45 p.m
filter with a minimum 600 cm'
filtration area.
?
Rinsing the
#12175 filter with 1000 ml
ultrapure water is adequate
cleaning for current ambient.
level determinations.
Preservative
Conc. redistilled HNO
.3
, 5 ml/L
Ultrapure HNC) ; to pH <2 or
(GFAA methods; USEPA,
1983).
?
1:1 HNO ;
to pH <2
lab preserve and soak for 2
days. Lab preserve samples
(3mI/L) (ICP Method 200.7;
for mercury to preclude
USEPA, 1991b)
atmospheric contamination.
53
E.2.?
Method of Sampling
Sampling Method 1669 (USEPA,
1995a) provides detailed guidance on steps
that can be followed to collect a reliable
sample and preclude contamination. Choose
manual or continuous sampling depending
upon which method is best for the specific
sampling program. Only trained personnel
should be entrusted the task of sample
collection.
E.2.1. Manual Sampling of Surface
Water or Effluent
In the manual sampling procedure,
the sampling team puts on gloves and orients
themselves with respect to the wind and
current to minimize contamination. "Dirty
hands" opens the sample bag. "Clean hands"
removes the sample bottle from the bag,
removes the cap from the bottle, and discards
the dilute acid solution in the bottle into a
carboy for wastes. "Clean hands" submerges
the bottle, collects a partial sample, replaces
the cap, rinses the bottle and cap with
sample, and discards the sample away from
the site. After two more rinses, "clean
hands" fills the bottle, replaces the cap, and
returns the sample to the sample bag. "Dirty
hands" reseals the bag for further processing
(filtration and/or preservation) or for
shipment to the laboratory.
E.2.2. Grab Sampling of Subsurface
Water or Effluent Using a Pole
Sampler
In sampling with the pole (grab)
samplin gdevice,
"dirty hands" removes the
pole and sampling device from storage and
opens the bag. "Clean
.
hands" removes the
sampling device from the bag. "Dirty hands"
opens the sample bag. "Clean hands"
removes the sample bottle, empties the dilute
acid shipping solution into the carboy for
wastes, and installs the bottle in the sampling
device. Using the pole, "dirty hands"
submerges the sampling device to the desired
depth and pulls the cord to fill the sample
bottle. After filling, rinsing, and retrieval,
"clean hands" removes the sample bottle
from the sampling device, caps the bottle,
and places it in the sample bag. "Dirty
hands" reseals the bag for further processing
or shipment.
E.2.3. Grab Sampling of Subsurface
Water or Effluent Using a Jar
Sampler
In sampling with the jar sampling
device, "dirty hands" removes the device
from its storage container and opens the outer
bag. "Clean hands" opens the inner bag,
removes the jar sampler, and attaches the
pump to the flush line. "Dirty hands" lowers
the weighted sampler to the desired depth and
turns on the pump, allowing a large volume
of water to pass through the system. After
stopping the pump, "dirty hands" pulls up the
sampler and places it in the field-portable
glove bag. "Clean hands" aliquots the sample
into various sample bottles contained within
the glove bag. If field filtration and/or
preservation are required, these operations
are performed at this point. After
filtration/preservation, "clean hands" caps
each bottle and returns it to its bag. "Dirty
hands" seals the bag for shipment to the
laboratory.
E.2.4. Continuous Sampling of Surface
Water, Subsurface Water, or
Effluent Using a Submersible
Pump
In the continuous4low sampling
technique using a submersible pump, the
sampling team prepares for sampling by
setup of the pump, tubing, batteries. and. if
54
required, the filtration apparatus. "Clean
hands" removes the submersible pump from
its storage bag and installs the lengths of
tubing required to achieve the desired depth.
"Dirty hands" connects the battery leads and
cable to the pump, lowers it to the desired
depth, and turns on the pump. The pump is
allowed to run for 5 - 10 minutes to pump 50
- 100 liters through the system. If required,
"clean hands" attaches the filter to the outlet
tube. "Dirty hands" unseals the bag
containing the sample bottle. "Clean hands"
removes the bottle, discards the dilute acid
shipping solution into the waste carboy,
rinses the bottle and cap three times with
sample, collects the sample, caps the bottle,
and places the bottle back in the bag. "Dirty
hands" seals the bag for further processing or
shipment.
E.3.
?
Preservation
Samples to be analyzed for total
recoverable metals are preserved with
concentrated nitric acid (HNO
3
) to a pH less
than 2. In normal natural waters, 3-5 ml of
acid per liter of sample is recommended
(EPA, 1983, 1991b) to achieve the required
pH. The nitric acid must be known to be free
of the metal(s) of interest. Method 1669
provides specifications for the acid. Samples
for total recoverable metals should be
preserved immediately after sample
collection. It is common for laboratories to
recommend sample acidification in a
controlled uncontaminating environment for
both total recoverable and dissolved metal
fractions.
Field preservation is necessary for
trivalent and hexavalent chromium. Field
preservation is advised for hexavalent
chromium in order to provide sample
stability for up to 30 days.
To preclude contamination from
atmospheric sources, mercury samples should
be shipped unfiltered and unpreserved via
overnight courier and filtered and/or
preserved upon receipt at the laboratory.
E.4.
?
Filtration
Because the
operational definition of
"dissolved" is so greatly affected by filtration
artifacts, the Gelman #12175 capsule filter or
equivalent capacity filter must be used,
regardless of how the samples are collected.
(The next largest capacity filter is
approximately 80 cm 2 surface area.) The
minimization of filtration artifacts can be
assured with high capacity tortuous path
filters and limited sample volume ( 1000
ml). The Gelman #12175 capsule filter has
equivalent filtration area of 600 cm'-.
The filtration procedure given in
Method 1669 is used for samples collected
using the manual, grab, or jar collection
systems. In-line filtration using the
continuous-flow approach was described
above. The filtration procedure used in
Method 1669 is based on procedures used by
USGS, and the capsule filter is the filter
evaluated and used by USGS.
The filtration system is set up inside
a glove bag, and a peristaltic pump is placed
immediately outside of the glove bag.
Tubing from the pump is passed through
small holes in the glove bag to assure that all
metallic parts of the pump are isolated from
the sample. The capsule filter is also placed
inside the glove bag.
Using "clean hands/dirty hands"
techniques, blank water and sample are
pumped through the system and collected.
The sample is acidified, placed back inside
the sample bag, and shipped to the
laboratory.
55
O
E.S.
?
Field Quality Assurance
The study plan should describe the
sampling location(s), sampling schedule, and
collection methodology, including explicit
information on the sampling protocol.
Detailed requirements and procedures for
field quality control and quality assurance are
given in USEPA Method 1669. If Method
1669 is not used, deviations. from that
Method should be described and the Method
should be supplemented by standard
operating procedures (SOPs) where
appropriate. It is desirable to include blind
QC samples as part of the project.
Equipment blank - Prior to the use of
any sampling equipment at a given
site, the laboratory or equipment
cleaning contractor is required to
generate equipment blanks to
demonstrate that the equipment is
free from contamination. Two types
of equipment blanks are required:
bottle blanks and sampling equipment
blanks.
Equipment blanks must be run on all
equipment that will be used in the
field. If. for example. samples are to
be collected using both a grab
sampling device and the jar sampling
device, then an equipment blank must
be run on both pieces of equipment.
The equipment blank must be
analyzed using the same analytical
procedures used for analysis of
samples so that contamination at the
same level is detected. If any
metal(s) of interest or any potentially
interferin
g
substance is detected in
the equipment blank, the source of
contamination/interference must be
identified and removed. The
equipment must be demonstrated to
be free from the metal(s) of interest
before the equipment may be used in
the field.
Field blank - In order to demonstrate
that sample contamination has not
occurred during field sampling and
sample processing, at least one (1)
field blank must be generated for
every ten (10) samples that are
collected at a given site. The field
blank is collected prior to sample
collection and should be collected for
each trip to a given site if fewer than
10 samples are collected per
sampling trip.
Field blanks are generated by filling a
large, pre-cleaned carboy or other
appropriate container with reagent
water (water shown to be free from
metals at the level required) in the
laboratory, transporting the filled
container to the sampling site,
processing the water through each of
the sample processing steps and
equipment (e.g., tubing, sampling
devices, filters, etc.) that will be used
in the field, collecting the field blank
in one of the sample bottles, and
shipping the bottle to the laboratory
for analysis.
If it is necessary to clean the
sampling equipment between
samples, a field blank should be
collected after the cleaning.
procedures but before the next
sample is collected.
Field duplicate - A field duplicate is
used to assess the precision of the
field sampling and analytical
processes. It is recommended that at
least one (1) field duplicate sample
56
be collected for every ten (10) samples that
are collected at a given site or for each
sampling trip if fewer than 10 samples are
collected per sampling trip.
The field duplicate is collected either
by splitting a larger volume into two
aliquots in the glove bag, by using a
sampler with dual inlets that allows
simultaneous collection of two
samples, or by collecting two
samples in rapid succession.
57
APPENDIX F
F.1.
?
Laboratory Facility, Equipment,
and Reagents
any of the laboratories
presently performing
metals determinations are
incapable of making measurements at or near
ambient criteria levels because of limitations
in facilities, equipment, or reagents. The QC
Supplement suggests the facilities
modifications necessary to assure reliable
determinations at these levels. The
modifications required can be extensive or
minimal, depending on the existing
capabilities of the laboratory. The ideal
facility is a class-100 clean room with walls •
constructed of plastic sheeting attached
without metals fasteners, down-flow
ventilation, air-lock entrances, pass-through
doors, and adhesive mats for use at entry
points to control dust and dirt from entering
via foot traffic. If painted, paints that do not
contain the metal(s) of interest must be used.
Class-100 clean benches, one
installed in the clean room; the other adjacent
to the analytical instrument(s) for preparation
of samples and standards, are recommended
to preclude airborne dirt from contaminating
the labware and samples.
All labware must be metal free.
Suitable construction materials are
fluoropolymer (FEP, PTFE), conventional or
linear polyethylene, polycarbonate, or
polypropylene. Only fluoropolymer should
be used when mercury is a target analyte.
The QC supplement su
ggests cleaning
procedures for labware. Gloves, plastic
wrap, storage bags, and filters may all be
used new without additional cleaning unless
results of the equipment blank pinpoint any
of these materials as a source of
contamination. In this case, either an
alternate supplier should be found or the
materials will need to be cleaned.
Each reagent lot should be tested for
the metals of interest by diluting and
analyzing an aliquot from the lot using the
techniques and instrumentation to be used for
analysis of samples. The lot will be
acceptable if the concentration of the metal
of interest is below the detection limit of the
method being used. Ultrapure acids are
available and should be used to preclude
contamination from this source, although
technical grades of acid may be pure enough
to be used for the first steps in the cleaning
processes.
Reagent water--water demonstrated
to be free from the metal(s) of interest and
potentially interfering substances at the
method detection limit (MDL) for that metal
in the analytical method being used--is
critical to reliable determination of metals at
trace levels. Reagent water may be prepared
by distillation, deionization, reverse osmosis,
anodic/cathodic strippin
g voltammetry, or
other techniques that remove the metal(s) and
potential interferant(s).?
-
F.2.?
Analytical Methods
The test methods currently in 40 CFR
Part 136 may not be sufficiently sensitive for
trace metals determinations. The Agency
believes dischar
gers
may use more sensitive
methods, such as stabilized temperature
graphite furnace atomic absorption
spectroscopy (STGFAA) and inductively
coupled plasma/ mass spectrometry
(ICP/MS) (USEPA, 1994c) even though
those methods have not yet been approved in
40 CFR Part 136 for general use in Clean
Water Act applications. In some instances,
STGFAA and ICP/MS may be preceded by
hydride generation or on-line or off-line
preconcentration to achieve these levels. The
58
Agency is developing methods for those
metals that cannot as yet be measured at
ambient criteria levels. The methods being
developed use the apparatus and techniques
described in the open technical literature.
This guidance does not address the use on
non-Part 136 methods in any context other
than metal translator studies performed by
the discharger.
Although analyses by STGFAA are
generally cheaper than those by ICP/MS, the
cost.
differences are usually not a limiting
consideration given the implications of
obtaining a precise and accurate translator
value. Achieving low detection levels can
add appreciably to the cost, but those costs
may be justified if a translator means the
difference between permit compliance and
noncompliance.
F.3. Laboratory
Quality Control
The QC Supplement provides
detailed quality control procedures that
should assure reliable results. The QC
Supplement requires each laboratory that
performs trace metals determinations to
operate a formal quality assurance program.
The minimum requirements of this program
consist of an initial demonstration of
laboratory capability, analysis of samples
spiked with metals of interest to evaluate and
document data quality, and analysis of
standards and blanks as tests of continued
performance. Laboratory performance is
compared to established performance criteria
to determine if the results of analyses meet
the performance characteristics of the
method. This formal QA program has the
following required elements:
The analyst must make an initial
demonstration of the ability to
generate acceptable accuracy and
precision with the method used for
analysis of samples. This
demonstration is comprised of tests
to prove that the laboratory can
achieve the MDL in the EPA method
and the precision and accuracy
specified in the QC Supplement.
Analyses of blanks are required
initially and with each batch of
samples started through the analytical
process at the same time to
demonstrate freedom from
contamination.
The laboratory must spike at least
10% of the samples with the metal(s)
of interest to monitor method
performance. 'When results of these
spikes indicate atypical method
performance for samples, an
alternative extraction or cleanup
technique must be used to bring
method performance within
acceptable limits.
The laboratory must, on an ongoing
basis, demonstrate through
calibration verification and through
analysis of a laboratory control
sample that the analytical system is
in control.
The laboratory must maintain records
to define the quality of data that are
generated.
In recognition of advances that are
occurring in analytical technology, the
analyst is permitted to exercise certain
options to eliminate interferences or lower
the costs of measurements. These options
include alternate digestion, concentration,
and cleanup procedures and changes in
instrumentation. Alternate determinative
techniques, such as the substitution of a
colorimetric technique or changes that
degrade method performance. are not
59
allowed. If an analytical technique other than
the technique specified in the EPA method is
used, then that technique must have a
specificity equal to or better than the
specificity of the techniques in EPA method
for the analytes of interest.
60
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