United States
Environmental Protection
Agency
Robert S. Kerr Environmental
Research Laboratory
Ada OK 74820
Research and Development
EPA-60Q/S2-82-075 Nov. 1982
Project Summary
Treatment Compatibility of
Municipal Waste and
Biologically Hazardous
Industrial Compounds
A. F. Gaudy, Jr., Don F. Kincannon, and T. S. Manickam
The overall objective of this research
was to gain information on the effect of
organic priority pollutants on the
performance of activated sludge units at
publicly owned treatment works. The
study was designed to gain information
on the effects of a wide array of
compounds and to determine the most
useful study procedures to be used in
assessing effects related to the need for
pretreatment of industrial wastes.
Batch and continuous flow bench-
scale activated sludge pilot plants were
fed settled municipal sewage. The
general approach was to compare the
performance of control systems with
that of comparable systems dosed with
various concentrations of priority
pollutants. Twenty-four compounds
were studied in batch pilot plants; eight
of these were also studied in continuous
flow pilot plants operated at a sludge
age of 5 days. Four of the eight were also
studied in extended aeration pilot
plants. Each compound was studied for
a period of six months under each mode
of operation.
In batch operations, only pentachlo-
rophenol and 2-chlorophenol caused
increases in soluble residual chemical
oxygen demand (COD) at feed concen-
trations of 5 mg/l. None of the eight
compounds tested in continuous flow at
a sludge age of 5 days showed increased
effluent soluble COD at the 5 mg/l
dosage. However, the effluent of the
units dosed with phenol and methylene
chloride did show increased suspended
solids concentrations. Higher dosage
levels of several compounds led to
higher soluble COD and suspended
solids concentrations in the effluent.
Effluents from the extended aeration
process were better than from compar-
able systems at lower sludge age. From
the analyses made for specific com-
pounds, there was no evidence for
excessive pass-through of priority
pollutants on publicly owned treatment
works.
This Project Summary was devel-
oped by EPA's Robert S. Kerr Environ-
mental Research Laboratory, Ada,
OK, to announce key findings of the
research project that is fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
The magnitude of the information
base required for formation of regulatory
policy to protect the public health and
the public investment in biological
treatment facilities is best realized by
considering the engineered natural
process employed for treatment. The
microbial population involved in the
biological waste treatment is very
diverse and the species making up the
sludge may change due to interspecies
interactions alone without change in
the environmental conditions. So the
task of determining whether a particular
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chemical at low concentrations is
responsible for an observed malfunction
of an activated sludge process requires
considerable data collection.
This 2-year study was undertaken to
evaluate as many compounds as possible
but for a sufficient time and with
sufficient depth of investigation to
provide reliable and useful information.
The most critical need is to assess the
effect and magnitude of effect rather
than the mechanism involved. The
major effect would be the leakage of
soluble organics and solids in the
effluent. The fate of the priority pollutant
is also of concern.
Some compounds were studied con-
currently in extended aeration, activated
sludge, and batch systems. This enables
one to assess the usefulness of batch
systems as well as the effect of sludge
age in accommodating the priority
pollutant. Also, auxiliary short-term
batch studies were made to assess the
rate of purification under various
dosages of toxic compounds and to
determine the degree to which the
priority pollutants can be stripped under
conditions of aeration in the pilot plant.
In addition to determining the biological
effects of specific compounds on
activated sludge, this study was designed
to evaluate methods which can be
employed to obtain data for the formula-
tion of pretreatment policy.
Conclusions
Based on the results of pilot plant
studies, the following conclusions were
made. Of the 24 compounds studied in
batch systems, only pentachlorophenol
and 2-chlorophenol gave evidence of
causing metabolic stress to the system
at a feed concentration of 5 mg/l. At a
feed concentration of 25 mg/l and
higher, 4-chloro, 3-methyl phenol
showed metabolic disturbance. In the
continuous flow activated sludge unit,
none of the compounds tested showed
leakage of soluble organics at a dosage
level of 5 mg/l. Leakage of soluble
organics and effluent suspended solids
at higher dosage levels was observed
for phenol and methylene chloride.
Trichloroethylene showed metabolic
disturbances and increased effluent
solids concentrations when subjected
to cyclic loading with alternating
concentration.
In the case of the extended aeration
systems, there was evidence for in-
creased soluble COD in the effluent only
from the unit dosed with phenol at the 5
mg/l dosage level. There was no in-
crease in effluent suspend ed solids for
any of the four compounds at this
dosage level. At the higher levels of
dosage (25 mg/l and 50 mg/l}, there
was evidence of increased soluble COD
and suspended solids only in the units
dosed with phenol. Also, only in the
units dosed with phenol was there
evidence of disturbance of effluent
quality when the dosage was changed
on alternate days. From the results of
this study, there was evidence that the
effluents of the extended aeration pilot
plants were lower in soluble COD and
particularly in suspended solids con-
centrations. Any assessment of the ef-
fects of priority pollutants on activated
sludge should include ecological con-
siderations such as effluent clarity and
sludge species diversity.
In regard to study techniques for
assessment of effects of priority pollut-
ants on publicly owned treatment
works, it is concluded that batch pilot
plant operations, although more easily
facilitated, cannot be used in place of
continuous flow pilot plant studies as a
means of gaining information on which
to base pretreatment policy regulations.
The analysis made for specific test
compounds gave indication of the fateof
the compound. With exception of
nitrobenzene and 2-chlorophenol, most
of the other compounds studied were
present in the effluent only at very low
concentrations. Most of the test com-
pounds were removed by either stripping
biodegradation, or attachment to the
surface of the microorganisms.
Recommendations
In future assessments of the effect of
priority pollutants on the activated
sludge process, a study period of about 6
months should be sufficient for each
compound. Batch pilot .studies should
be abandoned as a basis for formulation
of regulatory policy because, as observed
in the current investigation, operation
environment, e.g., different sludge
ages, effected changes in the ecology of
the sludge which translated to changes
in effluent quality in the presence of
various toxicants.
Bench-scale continuous flow- pilot
plants should be run on municipal
wastes relatively devoid of industrial
wastes at three or more sludge ages.
Variations in dosage and mode of its
administration should include steady
dosages, variations in mode of dosage
including steady concentration levels,
and pulsating levels with various time
periods of resting between dosages.
Combinations of priority pollutants
should be run. The analyses should
include specific toxicant levels in
effluent and sludge, forms of nitrogen,
detailed observation of changes in
predominant species of microorganisms
in the biomass and auxiliary batch
growth studies to establish whether the
presence of toxicant causes changes in
the biokinetic constants used in design
and operational models.
Results
Twenty-four compounds on the priority
list were studied in batch pilot plants.
Eight compounds were studied in
continuous flow activated sludge pilot
plants, and four were studied in extended
aeration systems. The continuous flow
units operated were of internal recycle
type. A listing of the compounds studied
and operational conditions under which
they were studied is given in chronolog-
ical order in Table 1. The feedstock
consisted of effluent from the primary
clarifier of the Stillwater Treatment
Plant supplemented with glucose and
ammonium sulfate. To this feedstock
various concentrations of the test
compound were added during conduct
of the experiment. The major analytical
techniques employed were COD, sus-
pended solids concentration, and specific
compound concentration measured by
gas chromatography.
The batch units were operated on a
24-hour fill and draw schedule. The
internal recycle continuous flow units
were operated at a mean cell residence
time of 5 days and hydraulic retention
time of 8 hours. The extended aeration
activated sludge systems were operated
at a hydraulic retention time of 16
hours.
The performance of the batch and
continuous flow pilot plants was evalu-
ated based on the statistical analysis of
the data along with plotted data for a
control and the unit receiving the test
compound. Changes in predominant
species, presence or absence of proto-
zoa and/or filamentous organisms
were also taken into account.
In the batch studies, pentachloro-
phenol and 2-chlorophenol showed the
most adverse effects upon soluble COD
removals. These effects were at all
concentrations. The other compounds
showed very little effect.
For the compounds tested in the
continuous flow activated sludge pilot
plants, there was no evidence for
increased soluble COD in the effluent at
the 5 mg/l dosage. At this lower dosage,
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Tattle 1,
Batch
Compounds Studied and Operational Conditions
Continuous Flow
Un-0.2 days'
extended Aeration
Period
Naphthalene
Toluene
Hexachlorobenzene
Benzene
Phenol
Pentachlorophenol
Nitrobenzene
2-Chlorophenol
Anthracene
2-Nitrophenol
Hexachloroethane
Fluorene
Methylene Chloride
Carbon Tetrachloride
Chloroform
Trichloroethylene
Chlorobenzene
Tetrachloroethylene
4-Chloro,3-methyl
phenol
Ethylbemene
1,2-Dichloroethane
1,1,2-Trichloroethane
Bromoform
Tetrachloroethane
Benzene
Phenol
Nitrobenzene
2-Chlorophenol
Methylene Chloride
Trichloroethylene
Phenol
2-Chlorophenol
Methylene Chloride
4-Chloro,3-methyl phenol 4-Chloro.3-methyl phenol
1,2-Dichloroethane
7/15.
1977
to
1/15.
1978
1/15.
1978
to
7/15.
1978
7/15.
1978
to
1/15.
1979
1/15,
1979
to
6/15.
1979
there was evidence for increased
suspended solids in the effluent of pilot
plants dosed with phenol and methylene
chloride. At the higher dosage levels,
there was evidence for an increase in
both soluble COD and suspended solids
in the effluent for the pilot plant dosed
with phenol. For the units dosed with 2-
chlorophenol, methylene chloride, and
1,2-dichloroethane, soluble COD in the
effluent was not affected, but there was
some disturbance in effluent suspended
solids concentration. In addition, cyclic
loading of nitrobenzene and trichloro-
ethylene led to increased suspendeds in
the effluent.
Based upon the analyses made, there
was no evidence of massive passthrough
of any of the compounds for which
specific analytical determination was
made, even at the dosage level of 50
mg/l. However, small quantities of
some of the compounds were detected
in the effluents.
The results of this study showed that
the effluents of the extended aeration
pilot plants were lower in soluble COD
and suspended solids than effluents
from comparable faster growing systems.
Among reasons for such results may be
lower mass loading rate, i.e., higher
biomass concentration and longer
mean hydraulic retention time. The
reason for the lower suspended solids
concentration is probably due to gener-
ally greater abundance of protozoa.
Generally in the faster growing systems,
an increase in dosage of. the test
compound appeared to cause more
serious reduction in protozoan activity
than in the extended aeration system.
Thus, while the biomass with fewer
grazing species could provide nearly
equal efficiency with respect to residual
soluble COD, it would not provide a low
suspended solids concentration in the
effluent. Therefore, in designing study
procedures to assess effects of priority
pollutants on activated sludges, the eco-
logical considerations as reflected in ef-
fluent clarity as well as other aspects of
ecology, such as limiting effects on
species diversity, should be included as
parameters for assessment.
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A. F. Gaudy, Jr., Don F. Kincannon. and T. S. Manickam are with Oklahoma State
University, Stillwater. OK 74074.
Thomas E. Short, Jr. is the EPA Project Officer (see below).
The complete report consists of two volumes, entitled "Treatment Compatibility
of Municipal Waste and Biologically Hazardous Industrial Compounds,"
"Volume l,"(0rder No. PB 83-105 536; Cost: $19.00, subject to change)
"Volume/I. (Appendix}," {Order No. PB 83-105 544; Cost: $23.50, subjectto
change)
The above reports 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:
Robert S. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
P.O.Box 1198
Ada, OK 74820
U.S. GOVERNMENT PRINTING OFFICE: 1982—6S9-O17/O859
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
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