United States
Environmental Protection
Agency
Environmental Research
Laboratory
Duluth MN 55804
Research and Development
EPA-600/S3-83-083 Dec. 1983
Project Summary
Effects on Toxicity of Volatile
Priority Pollutants Added to a
Conventional Wastewater
Treatment System
Timothy W. Neiheisel, William B. Horning, II, Albert C. Petrasek, Jr., Vivian R.
Asberry, Debbe A. Jones, Ronda L. Marcum, and Christopher T. Hall
Static acute, unaerated, toxicity tests
using fathead minnows and Daphnia
magna and a bacterial toxicity assay,
Microtox™, were conducted on samples
of influent and effluent from two
conventional activated sludge pilot
wastewater treatment systems. The
two pilot treatment systems (A and B)
were constructed and operated in an
identical manner except that a mixture
of 16 volatile priority pollutants was
continuously added to the influent of
the experimental, B system. The com-
mon, unspiked influent for both systems
was a mixed industrial and domestic
wastewater. The volatile priority pollu-
tants were added to system B to obtain
a nominal concentration of 50 //g/l
each. The toxicity tests were performed
on the influent, primary effluent, and
secondary effluent samples to determine
the acute toxicity of the various samples
and to compare the reduction in toxicity
across the two treatment systems. The
results of these tests indicated that
there was no difference in toxicity
reduction between the two pilot treat-
ment systems at the level of pollutants
added. Toxicity for pairs of similar
samples, influent A and B, primary
effluent A and B, and secondary
effluent A and B, was essentially the
same. Even the influent samples, where
the highest concentration of pollutants
would be expected in the B samples,
were not different.
This Project Summary was developed
by EPA's Environmental Research
Laboratory. 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
ordering information at back).
Introduction
Static acute, unaerated, toxicity tests
using fathead minnows, Pimephales
promelas, and an invertebrate, Daphnia
magna, and a bacterial toxicity assay,
Microtox™* (Beckman Instruments, Inc.)
were conducted on influents and effluents
from two conventional activated sludge
pilot wastewater treatment systems. The
treatment systems were identical except
that a mixture of 16 volatile organic
priority pollutants, at a concentration of
50 //g/l each, was continuously added to
one of the systems. A concentration of
50fjg/\ each was chosen because it was
measurable and was at the high end of
concentrations of pollutants typically
found in municipal treatment plant
influents. The toxicity testing was
conducted by staff of the Environmental
Research Laboratory-Duluth/Newtown
(ERL-D/N) as part of a joint research
project with staff of the Municipal
Environmental Research Laboratory-
Cincinnati (MERL). The pilot treatment
systems were designed, constructed and
operated by MERL staff at the U.S.
Environmental Protection Agency's Test
and Evaluation Facility (T&E Facility)
Cincinnati, Ohio.
•Mention of trademarks or commercial products does
not constitute endorsement or recommendation for
use by the U.S. Environmental Protection Agency
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Objectives
The volatile organic priority pollutant
study was one of a series of MERL
projects designed to determine the
capacity of conventional waste treatment
systems to treat or remove "priority
pollutants." The primary objective of the
toxicity testing was to biologically
determine toxicity and toxicity removal
across the treatment systems. The
biological data were then to be used to
supplement MERL's chemical and physi-
cal evaluation of the treatment systems.
Approach
Two series of toxicity tests were
conducted on weekly grab samples of
influent and effluents. Only fathead
minnow 96-hr and Daphnia 48-hr unaer-
ated static tests were conducted on
influent and secondary effluent during
the first test series, June 1 through July
27, 1981. Fathead minnow and Daphnia
acute tests, along with Microtox™,
bacterial assays, were conducted on
influent, primary effluent, and secondary
effluent in the second series of tests,
August 11 through September 14,1981.
Results
Although test procedures for the two
series of tests were somewhat different
and test conditions varied slightly, the
results of the testing were similar.
Influent samples for both series of
tests with the fathead minnows and the
Daphnia were moderately toxic. In the
first series of tests, fathead minnow LC50
values for system A influent ranged from
9.7 to >50% and for system B influent
ranged from 9.7 to >50%. Daphnia EC50
values for system A influent ranged from
5.3 to >50% and for system B influent
from 8.6 to 46.2%. In the second series of
tests, fathead minnow LC50 values for
system A influent ranged from 20.9 to
50.8% and for system B influent ranged
from 20.9 to >50%. Daphnia EC50 values
for system A influent ranged from 15.9 to
66.3% and for system B influent ranged
from 14.2 to >50%. Microtox values for
the influent, available only for the second
series of tests, were lower than fathead
minnow and Daphnia test values. For
system A, Microtox EC50 values ranged
from<6.3 to 15.7% and for system B from
6.3 to 11.7%.
Results for the primary effluent samples
were available only for the second series
of tests. Fathead minnow LC50 values for
system A ranged from 23.6 to >50% and
for system B ranged from 20.9 to >50%.
Daphnia EC50 values for system A
ranged from 22.9 to 72.6% and for system
B ranged from 21.7 to 62.1%. Microtox
values were again lower than fathead
minnow and Daphnia test values and for
system A ranged from <6.3 to 13.9% and
for system B ranged from <6.3 to 20.5%.
For all the fathead minnow and
Daphnia tests for secondary effluent,
LC50 and EC50 values were >100%
effluent for both A and B systems. All
Microtox EC50 values were >50% which
was the highest concentration tested in
the early part of the second test series.
For the last three tests, in which a 100%
effluent was tested, there was no effect.
It should be noted that in only 3 of more
than 70 comparisons of similar samples
taken from system A and B did the 95%
confidence limits of the LC50 or EC50
values not overlap. Also, in only 8 of more
than 60 comparisons of test values for
fathead minnow and Daphnia for the
same samples did the 95% confidence
limits for the two species not overlap.
Further, in only oneDaphnia test compar-
ison and one Microtox comparison were
the influent and primary effluent samples
taken the same week different.
Discussion
The results of the toxicity tests indicate
that there was no difference in toxicity
reduction between the control and the
experimental system at the level of
volatile organic priority pollutants added.
The systems were essentially duplicates.
There was no difference in toxicity, with a
few exceptions, between similar samples
taken at the same time from the two
treatment systems. This was true even of
the influent samples, where the concen-
tration of the priority pollutants was
highest in system B. The data also
indicate, with a few exceptions, that there
was no reduction in toxicity between
samples of influent and primary effluent.
There was, however, a significant reduc-
tion in toxicity between influent and
secondary effluent and between primary
and secondary effluent.
In terms of relative sensitivity of the
test systems or organisms, the fathead
minnow 96-hr and Daphnia 48-hr tests
gave similar values for toxicity for
comparable samples. The Microtox 15-
min assay consistently gave lower EC50
values than the other tests for the
influent and primary effluent. This
apparent greater sensitivity may result
from a greater sensitivity of the Micro-
tox™ assay, a sublethal test, or it may
have been caused by the use of the
Microtox Reagent Diluent, the standard
diluent for the Microtox test, rather than
the dilution water used for the other tests.
The EPA authors T. W. Neiheisel (also the EPA contact, see below), W. B.
Horning, II, A. C. Petrasek. Jr., V. R. Asbarry, D. A. Jones, R. L. Marcum.
and C. T. Hall are with the Environmental Research Laboratory, Duluth, MN
55804.
The complete report, entitled "Effects on Toxicity of Volatile Priority Pollutants
Added to a Conventional Wastewater Treatment System," (Order No. PB 83-
259 721; Cost: S7.OO, 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:
Newtown Fish Toxicology Station
Environmental Research Laboratory—Duluth
U.S. Environmental Protection Agency
Cincinnati, OH 45244
*US. GOVERNMENT PRINTING OFFICE 1983-759-015/7245
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Environmental Protection
Agency
Center for Environmental Research
Information
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