United States
Environmental Protection
Agency
Environmental Research
Laboratory
Duluth MN 55804
Research and Development
EPA/600/S3-85/005 Mar. 1985
vxEPA Project Summary
Site-Specific Water
Quality Studies of the
Straight River, Minnesota:
Complex Effluent Toxicity, Zinc
Toxicity, and Biological Survey
Relationships
Anthony R. Carlson and Thomas H. Roush
Comparative laboratory toxicity tests
using Ceriodaphnia reticulate and the
fathead minnow Pimephales promelas
were conducted to establish relation-
ships between the toxicity of a sewage
treatment plant effluent containing high
concentrations of zinc, toxicity of the
effluent in the receiving water, toxicity
of zinc added to the receiving water and
a reference water, and receiving water
biota survey data. Water and biota were
sampled under summer (3 times), fall
(once) and winter (once) conditions
over a one-year period. The relation-
ships were used in evaluating the pro-
tectiveness of a site-specific water
quality criterion derived for zinc. A
strong correlation between the effluents
toxicity to daphnids was established,
however, toxicity correlation with ad-
verse impact on river biota could not be
established.
It was concluded that the effluent did
not adversely affect taxa composition
and abundance at 2.7 miles (3.2 km)
below the discharge to the river. At 2.7
miles the zinc concentrations
ranged from <100 to 154 /ug/l and
averaged 144 fjg/\ on 3 of 4 sampling
dates indicating that a site-specific
criterion average concentration of 145
jug/I, approximately 3 times greater
than the national average concentra-
tion, would be protective of river biota.
This Project Summary was developed
by EPA's Environmental Research Lab-
oratory, Duluth, MN, to announce key
findings of the research project that is
fully documented in a separate report of
the same title (see Project Report order-
ing information at back).
Introduction
The physical and/or chemical charac-
teristics of water in a natural system may
alter the biological availability and/or
toxicity of a material such as zinc. Guide-
lines for deriving site-specific water qual-
ity criteria which take these factors into
account have been published by the U.S.
Environmental Protection Agency (here-
after referred to as the site-specific
guidelines)(U.S. EPA, 1983A). One guide-
line approach is tosimplytest a prescribed
number of resident species in site water
to meet minimum data requirements
from which a site criterion is calculated.
Another approach is to test sensitive
"indicator or surrogate species" from the
same population in both clean reference
water, hereafter referred to as laboratory
water, and site water at the same time
(except for water characteristics) under
similar conditions. The ratio of site water
toxicity value/lab water toxicity value is
used to modify the national criteria value
to a site-specific value. Both of these
criteria derivation approaches are based
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on the assumptions: (1) that differences
i n the toxicity values of a specific material
determined in laboratory water and site
water may be attributed to chemical (e.g.,
complexing ligands) and/or physical (e.g.,
adsorption) factors that alter the biological
availability and/or toxicity of a material
and (2) that selected test species directly
integrate differences in the biological
availability and/or toxicity of the material
and provide a direct measure of the
capacity of a site water to increase or
decrease toxicity values relative to values
obtained in laboratory water. Such single
chemical criteria address effects of pol-
lutants on aquatic life in the absence of
other pollutants in the water column, a
condition which seldom occurs. A chem-
ical of interest is usually one component
of many components in an effluent which
may affect the chemicals biological avail-
ability and/or toxicity.
The objectives of this research project
were (1) to evaluate the use of sublethal
toxicity test endpoints (effects on survival,
growth, and reproduction of selected
species) obtained in effluent dilution and
receiving water tests for predicting im-
pacts on resident biota; and (2) to deter-
mine if site-specific water quality criteria
are protective under complexed ambient
conditions caused by a point source
effluent.
The objectives were approached by
conducting aquatic toxicity tests to estab-
lish relationships between the toxicity of
a sewage plant effluent (STP) containing
high concentrations of zinc, toxicity of the
effluent in the receiving water, toxicity of
zinc added to receiving water and a
laboratory water, and biological survey
data.
Conclusions
A strong correlation between the ef-
fluents toxicity and zinc toxicity was
established; however, toxicity correlation
with adverse impact on river biota could
not be established. The lack of correlation
between effluent toxicity to daphnids and
biological impact in the river at a sam-
pling station approximately 1 mile (1.6
km) downstream from the STP discharge
may have been due to not sampling and
testing the effluent and receiving water
over a sufficient number of days to get a
measure of the exposure duration of the
river biota to conditions toxic to the test
animals. Often riverflow had been higher
prior to sampling indicating that suscept-
ible biota may not have time to react to
adverse conditions. The higher flow may
also have contributed to biota recoloniza-
tion which may have masked effluent
impact.
Under the conditions of this study the
distribution of benthic-macroinverte-
brates and fish did not appear to be
adversely impacted by the STP effluent or
its zinc component at a sampling station
approximately 2.7 miles (3.2 km) down-
stream. At this station, zinc concentra-
tions ranged from <100 to 154 /ug/l on
the 4 dates it was sampled and averaged
144 fjg/\ on 3 of 4 sampling dates. The
total number of benthic-macroinverte-
brate taxa found at this station were
similar or greater than found at the
reference station on the 4 sampling
dates. The total number of fish species
were similar between these stations on
the 2 dates they were sampled. The total
number of plankton taxa were markedly
different on 1 of the 3 dates they were
sampled. This difference could have been
due to predation or upstream effluent
impacts causing plankton death and/or
sedimentation. Nevertheless, if the as-
sumption of the national (U.S. EPA,
1983B) and site-specific guidelines that
the protection of site-species all of the
time is not necessary because aquatic life
can tolerate some stress and occasional
adverse effects is taken into considera-
tion, these data indicate that a site-specif-
ic criterion average concentration of 145
/ug/l, approximately 3 times greater than
the national average concentration would
• be protective of Straight River biota.
EPA authors, A. R. Carlson (also the EPA Project Officer, see below) and T. H.
Roush are with Environmental Research Laboratory, Duluth, MN 55804.
The complete report, entitled "Site- Specific Water Quality Studies of the Straight
River, Minnesota: Complex Effluent Toxicity, Zinc Toxicity, and Biological
Survey Relationships, "(Order No. PB 85-160 703/AS; Cost: $10.00. subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Research Laboratory
U.S. Environmental Protection Agency
Duluth, MN 55804
U.S. GOVERNMENT PRINTING OFFICE: 1985-559-016/27006
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