Transcript Document

Control
Day
Replicates
1
2
3
4
5
6
7
8
9
10
1
A
A
A
A
A
A
A
A
A
A
2
A
A
A
A
A
A
A
A
A
A
3
A
A
A
A
A
A
A
A
A
A
4
6
4
5
4
5
4
5
6
4
5
5
12
10
12
13
10
11
12
11
10
9
6
A
A
A
D
A
A
A
A
A
A
7
21
22
19
D/21
23
22
20
19
18
Totl
39
36
36
D/36
38
39
37
33
32
D/17
There is one of these tables for each concentration in the test (Control, 6.25, 12.5,
25, 50, 100.
Pimephales promelas Survival
Replicates
Percent Effluent
Rep 1
Rep 2
Rep 3
Rep 4
Control
100
100
100
100
6.25%
100
100
100
100
12.5%
90
90
100
100
25%
90
90
90
100
50%
90
80
80
90
100%
50
40
40
50
Pimephales promelas Dry Weight (mg)
Replicates
Percent Effluent
Rep 1
Rep 2
Rep 3
Rep 4
Control
.620
.637
.567
.642
6.25%
.598
.642
.588
.632
12.5%
.601
.598
.599
.602
25%
.596
.572
.534
.535
50%
.504
.510
.498
.472
100%
.342
.298
.355
.301
Zebroid, Zebrass, Zonkey or
Ze-donk
.
We are not in Kansas anymore Toto.
Cultivated Land –
Milo and Corn
Municipal WRP
A
I
R
Impervious surface
Warehouse District
Metal Plating
Pig
Farms
Seepage
Landfill
City Limits 90,000
Impervious surface
Roads, roofs, parking lots, storm drains,
construction sites
Any stream with greater than 6% impervious
surface in its watershed will be degraded
B
A
S
E
Define the problem:
Based on dissolved oxygen values a segment of a stream has been
determined not to be in compliance for one of its designated uses,
high quality aquatic life.
Since the designated use is not being met the segment has been placed
on the State’s 303(d) list (303(d) lists should be updated every 2 yrs).
The 303(d) list has been prioritized and submitted to EPA. The M
(medium) priority ranking does not dictate that a TMDL is required
but given the location and political will of the area to “fix” the
problem it is likely if it is not delisted that TMDL will have to be
performed during the next round of listings. (These waters are to be
identified and priority ranked according to the provisions established
in EPA’s Water Quality Management and Planning Regulation at 40
CFR 103.7(b))
Delisting of Water Bodies as per Texas Water Quality Standards
Starting with the previous year’s list, the first task in the annual
update of the 303(d) list is to determine if any water bodies can be
delisted for one or more of the following reasons:
more recent data or information refute the original listing;
water quality has improved to meet the standards;
water quality standards have changed so that the original
assessment no longer represents a violation of the standard;
assessment procedures (for example, screening criteria) have
changed so that a reassessment does not show an exceedance
of the criteria (as occurred for the 1998 list where bodies
previously listed for partial support of contact recreation
were delisted);
a TMDL has been approved by the EPA
After examining the delisting requirements it has been determined
that the segment can not be delisted. Therefore, a TMDL will be
proposed and if accepted instituted.
A TMDL or Total Maximum Daily Load is a calculation of the
maximum amount of a pollutant from all contributing point and
non-point sources that a waterbody can receive and still meet water
quality standards, and an allocation of that amount to the pollutant
sources.
The calculation must include a margin of safety (MOS) to ensure
that the waterbody can be used for the purposes the State has
designated. The calculation must also account for seasonable
variation in water quality. Permit limits based on TMDLs are called
water quality based limits. The margin of safety should also allow
for future point and non-point uses.
Policies and Principles
To achieve the water quality goals of the CWA, EPA’s first
objective is to ensure that technology based controls
(engineering controls) on point sources are established and
maintained. Where such controls are insufficient to attain and
maintain, water quality based controls are required.
Lack of information about certain types of problems (for
example, those associated with nonpoint sources or with certain toxic
pollutants) should not be used as a reason to delay implementation of
water quality-based controls
Historically, the water quality based pollution control program has
focused on reducing the load of chemical contaminants (e.g. nutrients,
biochemical oxygen demand, metals) to water bodies. However, it is
becoming increasingly apparent that in some situations water quality
standards – particularly designated use and biocriteria – can only be
attained if non-chemical factors such as hydrology, channel morphology,
and habitat are addressed.
The presence, condition and numbers of types of fish, insects, algae,
plants, and other organisms are data that together provide direct, accurate
information about the health of specific bodies of water. Studying these
factors as a way of evaluating the health of a body of water is called
biological assessment. Biological criteria (biocriteria) on the other
hand, are a way of describing the qualities that must be present to support
a desired condition in a waterbody, and they serve as the standard against
which assessment results are compared. The terms biological assessment
and biological criteria have sometimes been used interchangeably. This
confusion is not surprising considering the interrelationship between the
two terms. [Clear Creek,
Biological Criteria are narrative or numeric expressions that describe the
reference biointegrity (structure and function) of aquatic communities inhabiting
waters of a given designated aquatic life use. Biocriteria are based on the numbers
and kinds of organisms present and are regulatory-based biological measurements.
Biological Integrity - the ability of an aquatic ecosystem to support and maintain
a balanced, adaptive community of organisms having a species composition,
diversity, and functional organization comparable to that of natural habitats within
a region.
Aquatic Community - association of interacting assemblages in a given
waterbody, the biotic component of an ecosystem.
Designated Use - classification specified in water quality standards for each
waterbody or segment describing the level of protection from perturbation
afforded by the regulatory programs. The designated aquatic life uses established
by the state or authorized tribes set forth the goals for restoration and/or baseline
conditions for maintenance and prevention from future degradation of the aquatic
life in specific waterbodies.
Reference Water Bodies – least impacted bodies of water in a region against
which the level of degradation of a non-reference stream can be compared.
Because the biological assessments that are required to determine if
a segment that has a aquatic life designation are time consuming and
expensive the US EPA has developed a series of documents that are
referred to as Rapid Bioassessment Protocols or RBPs. One such
manual is, Rapid Bioassessment Protocols For Use in Streams and
Wadeable Rivers: Periphyton, Benthic Macroinvertebrates, and
Fish. Second Edition. This manual and many others can be obtained
from www.epa.gov/owow/monitoring
The RBPs contain methods to assess the physical, chemical and
biological characteristics of a segment.
Total Assessed Waters of Texas
Assessed Waters of Texas by Watershed
Water Quality by Waterbody Type
Rivers, Streams, and Creeks
Individual Use Support for Assessed Waters
Water Quality Attainment for Assessed Waters
Top State Causes of Impairment
Top State Probable Sources of Impairments
Lakes, Ponds, and Reservoirs
Individual Use Support for Assessed Waters
Water Quality Attainment for Assessed Waters
Top State Causes of Impairments
Top State Probable Sources of Impairments
Red represents links
To implement the TMDL program, the regulation establishes the
following definitions for loading capacity, load allocation, waste load
allocation, total maximum daily load, water quality limited segments
and water quality limited segments still requiring TMDLs. A
definition of Margin of Safety is also provided.
TMDL = LC=WLA + LA + MOS
Loading Capacity (LC) – The greatest amount of loading that a water
can receive without violating water quality standards.
Wasteload Allocation (WLA) – The portion of a receiving water’s
capacity that is allocated to one of its existing or future point sources
of pollution. WLA’s constitute a type of water-quality based effluent
limitation.
Load Allocation (LA) – The portion of a receiving water’s total
loading capacity that is attributed either to one of its existing or
future nonpoint sources of pollution or to natural background
sources. Load allocations are best estimates of the loading
which may range from reasonably accurate estimates to gross
allotments, depending on available data and appropriate
techniques for predicting the loading. Wherever possible,
natural and nonpoint source loads should be distinguished.
Total Maximum Daily Load (TMDL) – The sum of the individual
WLAs for point sources and LAs for non-point sources and natural
background. If a receiving water has only one point source
discharge, the TMDL is the sum of that point source WLA plus the
LAs for any non-point sources of pollution and natural background
sources, tributaries or adjacent segments. TMDLs can be expressed
in terms of either mass per time, toxicity or other appropriate
measure that relates to a State’s water quality standard. If other
nonpoint source pollution control actions make more stringent load
allocations practicable, the WLAs can be made less stringent. Thus,
the TMDL process provides for nonpoint source control tradeoffs.
TMDL = LC=WLA + LA + MOS
Water Quality Limited Segments – Those segments that do not or are
not expected to meet applicable water quality standards even after
the application of technology based effluent limitations required by
sections 301(b) and 306 of the Act. Technology based controls
include but are not limited to, best practicable control technology
currently available (BPT) and secondary treatment.
Margin of Safety (MOS) – A required component of the TMDL that
accounts for the uncertainty about the relationship between the
pollutant loads and the quality of the receiving waterbody. The MOS
is normally incorporated into the conservative assumptions used to
develop TMDLs (generally within the calculations or models) and
approved by EPA either individually or in State/EPA agreements. If
the MOS needs to be larger than that which is allowed through
conservative assumptions, additional MOS can be added as a
separate component of the TMDL .
TMDL = LC=WLA + LA + MOS
As stated in 40 CFR 131.2 “[water quality] standards serve the dual
purpose of establishing the water quality goals for a specific
waterbody and serve as the regulatory basis for the establishment of
water-quality-based treatment controls and strategies beyond the
technology based levels of treatment required by section 301(b) and
306 of the Act.” Standards also contain antidegradation provisions to
prevent the degradation of existing water quality.
From State of Texas Water Quality Standards: Antidegradation
Tier 1 – Existing uses and water quality sufficient to protect those
existing uses will be maintained. Categories of existing uses are the
same as for designated uses, as defined in §307.7 of this title (relating
to Site-specific Uses and Criteria).
Tier 2 – No activities subject to regulatory action which would cause
degradation of waters which exceed fishable/swimmable quality will be
allowed unless it can be shown to the commission’s satisfaction that the
lowering of water quality is necessary for important economic or social
development. Degradation is defined as a lowering of water quality by
more than a de minimis extent (The full expression is de minimis non
curat lex. This is a Latin phrase which means "the law does not care
about very small matters“), but not the the extent that an existing use is
impaired. Water quality sufficient to protect existing uses will be
maintained. Fishable/swimmable waters are defined as waters which
have quality sufficient to support propagation of indigenous fish,
shellfish, and wildlife and recreation in and on the water.
Tier 3 – Outstanding national resources that are defined as high quality
waters within or adjacent to national parks and wildlife refuges, state
parks, wild and scenic rivers designated by law, and other designated
areas of exceptional recreational or ecological significance. The quality
of outstanding national resource waters will be maintained and protected.
(4) – Discharges which cause pollution that are authorized by the
Texas Water Code, the Federal Clean Water Act, or other applicable
laws will not lower water quality to the extent that the Texas
Surface Water Quality Standards are not attained.
(5) – Anyone discharging wastewater which would constitute a new
source of pollution or an increased source of pollution from any
industrial, public or private project or development will be required
to provide a level of wastewater treatment consistent with the
provisions of the Texas Water Code and the Clean Water Act (33
United States Code, §§1251 et seq.). As necessary, cost effective
and reasonable best management practices established through the
Texas Water Quality Management Program shall be achieved for
non-point sources of pollution.
Assessment of the TMDL - Once control measures have been
implemented, the impaired waters should be assessed to determine
if water quality standards have been attained or are no longer
threatened. The monitoring program used to gather the data
should be designed based on the specific pollution problem or
sources. For example, past experience has shown that several
years of data are necessary from agricultural non-point source
watershed projects to detect trends (i.e., improvements) in water
quality. As a result, long term monitoring efforts must be
consistent over time in order to develop a data base adequate for
analysis of control actions.
Sprawl has been identified as one of the causes of increased storm
water run off and stream erosion in many watersheds. In a healthy
functioning watershed, most precipitation soaks into the ground and
is utilized by vegetation, recharges aquifers, and maintains surface
water flows. When just 10% of the watershed is developed,
streambeds start to degrade due to increased runoff. After about
20% of the watershed is developed, most streams have been severely
degraded or destroyed.
Forests goods and services… the value of forests is not measured in
terms of the goods they provide alone, the services they provide
(decreased flooding, water retention, CO2 sequestration, transport of
rain to the interior of countries) may be more valuable than the
goods. Often referred to as ecological services.
Legacy Pollutants
• Legacy pollutant is a collective term used to
describe substances whose use has been banned or
severely restricted by the U.S. EPA. Because of
their slow rate of decomposition, these substances
often remain at elevated levels in the environment
for many years after their widespread use has
ended. No additional loading of legacy pollutants
is allowed or expected due to EPA restrictions.
Gradual declines in environmental legacy
pollutant concentrations occurs as a result of
natural attenuation processes.
Tarrant County water bodies on the State 303d list due to
concentrations of legacy pollutants in fish tissue that have
resulted in the issuance of a fish consumption ban by TDH.
Segment Number
Segment Name
Fish Tissue
Contaminants
TDH Ban Issued
0829
Clear Fork of the Trinity
Below Benbrook Lake,
etc.
Chlordane
01/1990
0806
West Fork of the Trinity
Below Lake Worth
Chlordane
01/1990
0829A
Lake Como (entire lake)
Chlordane, DDT,
Dieldrin, PCBs
04/1995
0806A
Fosdic Lake (entire
lake)
Chlordane, DDE,
Dieldrin, PCBs
04/1995
0806B
Echo Lake (entire lake)
PCBs
12/1995
These chemicals are in the edible portions of fin fish.
The Aquatic Life Orders for the Fort Worth Water Bodies were
issued on the basis of an unacceptable carcinogenic risk of liver
cancer and a noncarcinogenic risk of adverse liver effects due to
fish tissue contaminant levels.
The ultimate goal of these TMDLs is the reduction of fish tissue
contaminant concentrations to levels that constitute acceptable
risk to fish consumers, allowing TDH to remove the bans on fish
consumption. The allowable load of contaminant is based on fish
tissue concentrations.
Source Analysis
• Chlordane was introduced in 1948, and was used
extensively as a broad spectrum insecticide to
control soil insects on agricultural crops, as a
home lawn and garden insecticide, as a fumigating
agent, and for termite control . EPA suspended the
use of chlordane on food crops in 1978, and
phased out other above ground uses over the
following five years. All uses except underground
application for termite control were banned in
1983. Manufacture and sales were halted in 1987,
and use of existing stores was allowed until April
1998 when sale and use were terminated.
Source Analysis continued.
• DDT was initially used in WWII for control of
disease carrying insects, and was used extensively
as a broad spectrum insecticide for the control of
almost all agricultural and disease-carrying
insects. It was used extensively in the 1950s and
1960s for mosquito control in urban areas. DDD is
a metabolite of DDT and was itself manufactured
as a pesticide for several years. Most uses of DDT,
and all uses of DDD, were banned by EPA in
December 1972. DDE is the major degradation
product of DDT and DDD, and is among the most
widely occurring pesticide residues.
Source Analysis - continued
• Dieldrin was used as a pesticide, and is a
degradation product of the pesticide aldrin.
Although aldrin was used in greater quantity, it is
rapidly converted to the more persistent dieldrin in
the environment. Both pesticides were used
primarily for the control of rootworm and
cutworm with some use in the citrus industry and
for mosquito larvae and termite control. All food
crop uses of both compounds were canceled in
May 1975, and only subsurface injection for
termite control was allowed after that time. All
remaining uses were cancelled in 1987.
Source Analysis – continued.
• PCBs are a group of synthetic organic chemicals
containing 209 possible individual compounds, which vary
in chemical and physical properties, toxicity,
environmental persistence., and degree of
bioaccumulation. PCBs were manufactured as mixtures of
different congeners, and generally sold under the name
Aroclor. PCBs were most widely used as coolants and
lubricants in transformers, capacitors, and other electrical
equipment. In 1976 TOSCA banned, with limited
exception, the manufacture, processing distribution in
commerce, and use for PCBs. TSCA also required the EPA
to promulgate regulations for proper use, cleanup, and
disposal. TSCA and subsequent EPA rules did not require
PCB-containing materials to be removed from service and
many are still in use (EPA, 1999). A substantial portion of
PCBs manufactured before 1977 still remain in service,
although these are being phased out as equipment is
replaced or decontaminated.
Legacy pollutant contamination in the Trinity River and urban
lakes appears to have originated from urban areas, as the
watersheds of these water bodies have been highly urbanized
for many years. Erosion as a result of extensive urban
development over the past 10 to 15 years may have
contributed contaminants attached to source soils. Ulery and
Brown (1995) evaluated a number of available data sets from
the Trinity River Basin, and found a significant correlation
between sediment chlordane presence and urban land use.
Irwin (1988) found concentrations of total chlordane in
mosquitofish to be strongly associated with residential runoff
from the area. Kleinsasser and Linam (1989) found elevated
chlordane levels in fish collected within the area covered by
the TDH consumption ban on the Trinity River, and suggested
urban or suburban runoff as the source.
Recent household hazardous wastes (2000) received at the
City of Fort Worth Environmental Collection Center have
included chlordane, suggesting some recent or possible
continued use in the area. Urban residents may have
continued using existing stocks of chlordane since it was in
use longer than some of the other legacy insecticides. Van
Metre and Callender (1997) found the chlordane peak in
sediment cores from White Rock Lake in Dallas to have
occurred around 1990, reflecting its relatively recent urban
use.
Continuing decreases in environmental legacy pollutant levels are
expected, although the necessary time frame is subject to debate.
Within the context of these TMDLs, legacy pollutants are considered
background sources that reflect the site-specific application history
and loss rates of the subject area. All continuing sources of pollutant
loadings occur from nonpoint source runoff, leaching, or erosion of
the various sinks that may exist within the watershed. No authorized
point source discharges of these pollutants are allowed by law.
Therefore, any contribution from point source discharges would be
the result of illegal disposal of these contaminants by customers of
the treatment systems. Available evidence suggests that legacy
pollutants are generally declining in both the surface sediments and
the fish tissue of the affected Fort Worth water bodies. Continuing
natural attenuation of these pollutants is expected via degradation
and metabolism of the contaminants, burial of contaminated
sediment through natural sedimentation in the urban lakes, and
scouring and redistribution of sediments in the river.
Natural attenuation is generally a preferred option for the elimination
of legacy pollutants. More drastic alternatives, such as sediment
removal by dredging, can result in considerable habitat disturbance
and destruction, and sediments resuspended during dredging further
expose aquatic life to contaminants and the potential for additional
uptake, cause abrasive damage to gills and sensory organs of fish and
invertebrates, and interfere with fish prey selection. More drastic
measures such as dredging 0or eradication of contaminated fish
communities and restocking are generally better justified at heavily
contaminate sites impacted by point source discharges and major
spills.
The Laguna de Santa Rosa, California TMDL
Summary
Criterion – 0.02 mg/l (as unionized ammonia) for freshwater aquatic life.
Concentrations of total ammonia (NH3 + NH4+) which contains an unionized ammonia
concentration of 0.020 mg/l NH3.
pH Value
Temp.
oC
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
5
160
51
16
5.1
1.6
0.53
0.18
0.071
0.036
10
110
34
11
3.4
1.1
0.36
0.13
0.054
0.031
15
73
23
7.3
2.3
0.75
0.25
0.093 0.043
0.027
20
50
16
5.1
1.6
0.52
0.18
0.070 0.036
0.025
25
35
11
3.5
1.1
0.37
0.13
0.055 0.031
0.024
30
25
7.9
2.5
0.81
0.27
0.099
0.045 0.028
0.022
Percent un-ionized ammonia in aqueous ammonia solutions
pH Value
Temp
oC
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
5
0.013
0.040
0.12
0.39
1.2
3.8
11
28
56
10
0.019
0.059
0.19
0.59
1.8
5.6
16
37
65
15
0.027
0.087
0.27
0.86
2.7
8.0
21
46
73
20
0.040
0.13
0.40
1.2
3.8
11
28
56
80
25
0.057
0.18
0.57
1.8
5.4
15
36
64
85
30
0.080
0.25
0.80
2.5
7.5
20
45
72
89
Things we need to understand….
Algal Growth Potential Assay – two major nutrients play an important role in
algal growth. These are nitrogen and phosphorus. If you take a sample of
water, add phosphorus to it and put it under the appropriate lighting conditions
and the algae in the sample grow that tells you what? If you take a sample of
water, add phosphorus to it and put it under the appropriate lighting conditions
and the algae don’t grow that tells you what (Liebig’s Law of the Minimum).
If you do the same experiment but instead of adding phosphorus, nitrogen is
added and what you find is that the addition of nitrogen causes the algae to
grow but the addition of phosphorus does not, what does that tell you?
When algae photosynthesize the products are _____________ and
_____________. When algae respire the products are ______________ and
_______________. When the rate of respiration exceeds the rate of exchange
of gaseous oxygen in the atmosphere with the water what happens? So if low
D.O. is a problem one way to fix it is to increase the turbulence of the water so
that there is a greater exchange of atmospheric oxygen and the water, or to
control the algal growth by limiting that factor that is responsible for increased
growth. In the case described above the nutrient to limit is?
Algal growth and subsequent death also contributes to the
reduction of oxygen in the water as a result of?
If this system goes anaerobic there is an additional problem of ?
The incomplete breakdown of organic matter results in the
production of compounds that are in many cases
__________________ , thereby creating a significant
secondary problem.
7 mg/l of oxygen as a standard is very high. This suggests that
the Laguna de Santa Rosa, Ca. is home to what kinds of fish
species?
What happens if a body of water is placed on the 303(d) list because
of “toxicity”? What kinds of problems does that present in terms of
setting up a TMDL?
The problems with toxicity as a parameter for listing on the 303(d)
list is the same as toxicity in an effluent (if the toxicity is
associated with the water column and not the sediment). WET
tells us whether or not the effluent is toxic or not, just as ambient
toxicity tests tell us whether or not the water (or sediment) in an
aquatic system is toxic or not. WET tests do not tell us what is
causing the toxicity. How do we deal with toxicity in a TMDL or
in an effluent.
Most of the time we need to identify what is causing the toxicity in
order to be able to control it, either through a TMDL or an effluent
control strategy. We do this through what is called a Toxicity
Identification Evaluation. Which may or may not be part of a
TRE.
A TRE is a plan that is submitted to the regulatory agency issuing
the permit to a discharger (EPA, its designee, or an Indian Tribe).
The plan is submitted to the permitting agency after an effluent
has been determined to be toxic, i.e. the discharger has failed its
NPDES WET limits. The steps leading up to the submission of a
TRE varies to some degree from permitting agency (state) to
permitting agency (state). It could be that a discharger fails its
NPDES permit for toxicity, reports that to the permitting agency
and the permitting agency increases the frequency of WET
testing. If subsequent tests show that the toxicity is gone then
nothing else has to be done. If the subsequent tests continue to
show toxicity then the regulated facility must submit a TRE. The
plan (TRE) outlines the series of steps that the facility is going to
take to eliminate the toxicity from the effluent. That plan may or
may not contain, but often does, a Toxicity Identification
Evaluation (TIE).
The US EPA has issued several guidance documents on TREs and
TIEs. We will spend most of our time looking at the Phase I TIE.
There is a new book that will be out soon that updates some of the
information on TREs and TIEs since the last of EPAs guidance
documents. I happen to be one of several author/editors of this book.
It is not bed time reading, but does contain some interesting detective
stories about the process people have gone through to identify
toxicants in effluents, ambient waters, and sediments.
Generally, there are three phases to a Toxicity Identification
Evaluation
Phase I Toxicity Characterization
Phase II Toxicity Identification Analysis
Phase III Toxicity Confirmation Analysis
Effluent Sample
Phase I Toxicant Characterization Tests
Treatability
Treatability Approach
or
Identify Toxicant
Approach
Identify Toxicants
Phase II Toxicant Identification Analyses
Phase III Toxicant Confirmation Procedures
Based on Site Specific
Considerations
Toxicity Treatability
Evaluations
Source Investigation
Control Method Selection and Implementation
Post Control Monitoring
TIEs work best on acutely toxic samples. Samples that express
toxicity on the seventh day of a Ceriodaphnia dubia test are often
very difficult to define. The level of difficulty in determining
toxicants in a TIE increases as the toxicity decreases. Freshwater
TIEs are generally done with C. dubia because they require less
sample to perform than for example P. promelas. However, C. dubia
are not more sensitive than P. promelas to all toxicants so care must
be taken to ensure that the appropriate identification of the toxicant(s)
has been made.
Phase I tests characterize the physical/chemical properties of the
effluent toxicant(s) using effluent manipulations and
accompanying toxicity tests. Each characterization test in the
Phase I series is designed to render a group of toxicants such as
oxidants, cationic metals, volatiles, nonpolar organics, or
chelatable metals unavailable. Aquatic toxicity tests performed
before and after the individual characterization steps, indicate
the effectiveness of the treatment to remove or reduce toxicity
and provide information on the nature of the toxicant(s). By
repeating the toxicity characterization tests using samples of a
particular effluent overtime, these screening tests provide
information on whether the characteristics of the toxicant(s)
causing toxicity remain consistent over time.
Toxic Effluent Sample
Initial Toxicity Test
(Day 1)
Baseline Toxicity
Test (Day 2)
EDTA Chelation
Test (Day 2)
C18Solid Phase
Extraction Tests
(Day 2)
Aeration Tests
(Day 2)
Acid
pHi
Base
Acid
Filtration Tests
(Day 2)
Acid
pHi
Base
Oxidant Reduction
Test (Day 2)
pHi
Base
Graduated pH Tests
(Day 2)
pH Adjustment
Tests Day 2
Acid
Base
pH 6 pH 7 pH 8
What do these tests do?
EDTA Chelation Test – We know from the water chemistry
test for hardness that EDTA binds the hardness producing alkaline
earth metals calcium and magnesium. We titrate a sample with
EDTA in the presence of the indicator calmagite and when all the
calcium and magnesium are tied up (chelated) the indicator turns
from red to blue. So EDTA binds divalent cations which include
such things as zinc, copper, lead, silver, aluminum, nickel, barium,
manganese2+, cadmium, cobalt, and strontium.
When a TIE (EDTA test) is performed 10 mls of effluent is added to
each cup and EDTA is added in varying concentrations from the
LC50 level (EDTA is toxic at higher concentrations) to low levels of
EDTA. After the EDTA is added C. dubia neonates (5) are added to
each cup. After 24 hours the survival of the C. dubia is determined.
If all the neonates in all concentrations are dead that means that the
EDTA did not remove the toxicant and therefore metals are not likely
the toxicant in this sample. If the middle concentrations remove the
toxicity that is a pretty good indication that metals are probably
contributing to the toxicity of the effluent.
The same process of treating the toxic sample with one of the TIE
characterization steps and then testing for toxicity is common to all
the steps.
Oxidation/Reduction – sodium thiosulfate is added to the
samples to remove things like chlorine.
Changes in pH (lowering and increasing) makes certain kinds
of toxicants more or less available depending on the toxicant.
pH adjustment/C18 is used as a treatment to remove nonpolar organics. Chemicals soluble in hexane or chloroform are
removed by this step including things like diazinon and other
pesticides.
pH adjustment/filtration step removes those chemicals that
might be associated with particles in the water that are removed
during filtration.
pH adjustment/Aeration test – removes materials that are
subject to volatilization like ammonia and cyanide; it also removes or
reduces surface active agents like soaps, detergents, resin acids,
charged stabilization polymers and coagulation polymers used in
some manufacturing processes
The pH (6, 7, and 8) adjustment step removes or helps define
toxicity due to things like ammonia. At pH 6 less of the toxic form of
ammonia (unionized ammonia NH3) is present. At pH 8 the opposite
is true.
It is often true that more than one treatment may have some affect on
the toxicity of a sample. For example, it is not unusual to find that in
addition to EDTA, some metals are removed when adjusted to high
pH and passed through the C18 column, treatment with sodium
thiosulfate in the Oxidant/Reduction test will also remove or reduce
some metals.
To continue on with our what if scenario we will assume that EDTA
removed the toxicity. We know that if EDTA removes the toxicity
that more than likely a metal(s) are involved. However, we don’t
have any idea at this point which metal(s) is involved. It may be that
in an industrial setting finding out that a metal(s) is causing the
toxicity may be enough to guide the plant personnel to a particular
industrial stream or additive that might be used in a plant. Several
times when cooling water from an industrial facility have been
determined to be toxic due to metals the operators had a good idea
that biocides used to control algae in the cooling towers (many
contain copper) might be a likely candidate and changing biocides
removed the toxicity and solved the problem. Municipal facilities
usually don’t have the same level of knowledge about what is
coming into the plant (who knows what some old codger like Vic
might be dumping down the drain). Therefore, it is often necessary
for these facilities to move to Phase II which is the Toxicity
Identification Phase of the TIE.
In the Toxicity Identification Phase things can get pretty complicated
and the degree of complexity is in part a function of what has been
characterized as the toxicant. We will continue with our
determination that a metal(s) is the toxicant as an example of the
general process. Experience has shown that if EDTA alone removes
the toxicity then copper, lead, cadmium, nickel, and zinc should be
measured. When sodium thiosulfate additions reduce or remove the
toxicity copper, cadmium and silver should be measured. In part
prioritizing what is going to be measured is a function of the method
of analysis. If the method of analysis is graphite furnace AA then
each metal has to be analyzed separately. If the method of analysis is
ICP/MS (inductively coupled plasma with a mass spectrometer) then
many metals can be measured simultaneously at toxicologically
relevant concentrations and and prioritizing the order of metals
analysis is not a necessary.
Once the concentration of the metals in the toxic sample have been determined
then one can begin to sort out which metals might be the ones contributing to
toxicity. To do this one can calculate the toxic units of the various metals. For
example, the acute toxic units TUa can be determined by dividing the
concentration of the metal in the toxic sample by the LC50 value for the test
organism (C. dubia) in our example. Assume the following
Metal
Concentration
ug/l
LC50
ug/l
TUa
copper
100
20
5
silver
25
40
0.625
nickel
200
350
0.571
zinc
400
415
0.96
This table shows that there is sufficient toxicity due to copper alone to cause the
results observed in the tests that have been formed. It does not rule out zinc as a
possible contributor. Nor does it rule out that there might be an interaction
between the metals that we can not account for by this methodology. However,
we have enough information to proceed to the Phase III or Confirmation Phase.
The Confirmation Phase of the TIE is probably the most poorly
developed of all the phases (in my opinion). What you would like to
be able to do in the case of metals is to add a resin that binds up
metals that can then be filtered out of the sample. For example, if
there was a resin that could be added to the sample that was selective
for copper it could be added to the sample, then filter it out and test
for toxicity. If the toxicity was removed the copper could be added
back into the sample at the concentration that was originally
measured and re-test the sample. If the sample was toxic after the
copper was added back to the sample we would have pretty good
confirmation copper was indeed the toxicant. The next step would
then be to try through the pre-treatment program to figure out how
the copper was getting into the system and and then reduce it through
treatment by the facility contributing the copper. Some of the new
methods discussed in the upcoming book address some of these
issues but much research remains to be done.
Once the most likely suspects are determined in Phase II of the TIE,
Phase III or the Confirmation Phase kicks in.
Rarely does one step or one test conclusively prove the cause of
toxicity in Phase III. Rather, all practical approaches are used to
provide the weight of evidence that the cause of toxicity has been
identified. The various approaches that are often useful in providing
that weight of evidence consist of correlation, observation of
symptoms, relative species sensitivity, spiking, mass balance
estimates and various adjustments of water quality. We won’t discuss
any of these in any detail.
What happens if a designated use for a segment is not being met and
the cause is determined to be sediment toxicity.
Again, as with toxicity in the effluent, the sediment toxicity approach
is essentially the same except the job is much more difficult and the
methods are still in a heightened state of development.
For water TIEs, metals, chlorine, and diazinon have been found to be
common toxicants. For sediments, ammonia is frequently identified
as the causative toxicant as well as metals.
What happens if a toxicant in the sediment is identified as the
causative agent and there is no longer any source in the watershed that
could be discharging that toxicant. These are often referred to as
legacy toxicants and “we the people” get to pay for the privilege of
cleaning this up unless there is historical evidence that a company that
is still in business somewhere, but not at this site, then they can be
charged with helping to clean this up.