United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-89/026 Mar. 1990
roject Summary
Removal and Fate of
RCRA and CERCLA Toxic
Organic Pollutants in
Wastewater Treatment
Sanjoy K. Bhattacharya, Rao V. R. Angara, Dolloff F. Bishop, Jr.,
Richard A. Dobbs, and Barry M. Austern
Two separate studies were con-
ducted to investigate the removal and
fate of 28 selected Resource Conser-
vation and Recovery Act (RCRA)
compounds (0.25 mg/L of each
compound) and 19 selected Compre-
hensive Environmental Response,
Compensation, and Liability Act
(CERCLA) compounds (0.5 mg/L of
each compound) in conventional
activated sludge treatment In each
study, two pilot-scale (35 gpm) acti-
vated sludge systems (Solids Reten-
tion Time (SRT): 4 days for RCRA
study and 8 days for CERCLA study)
were operated in parallel at The U.S.
Environmental Protection Agency's
Test & Evaluation Facility in
Cincinnati, Ohio. One system was
spiked continuously with either RCRA
or CERCLA toxics to produce an
acclimated biomass; the other was
spiked intermittently with the same
toxics and sampled to determine
performance under unacclimated
conditions. The selected RCRA or
CERCLA compounds did not cause
any adverse effects on Chemical
Oxygen Demand (COO) and
Suspended Solids (SS) removals. The
concentrations of organics (RCRA
study) in the air emissions indicated
that the chlorinated aliphatic solvents
were essentially volatilized into the
plant air emission stream, whereas
the aromatic volatile benzenes were
substantially degraded. Additional
work is planned to attempt to reduce
the analytical variability encountered
in these studies.
This Project Summary was devel-
oped by EPA's Risk Reduction engi-
neering Laboratory, Cincinnati, OH, 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
A survey of publicly owned treatment
works (POTW) showed that concentration
of priority pollutants in the influent
wastewater to many of these plants
exceeded the allowable concentrations
for these chemicals. In a study of the fate
of 22 toxic organics in wastewater
treatment plants, researchers reported
that a typical POTW significantly (up to
90%) reduced the concentrations of most
of these compounds. Certain compounds
were, however, present in the activated
sludge effluent in relatively high (20-30
ug/L) concentration. In an investigation of
the comparative removal of priority
pollutants by six biological and physical-
chemical treatment processes, research-
ers reported that the activated sludge
process provided best results. A further
review of the literature indicated that only
limited data are available for many
priority pollutants.
In the study summarized here, the
removal and fate of selected RCRA and
CERCLA toxic organic pollutants were
evaluated with two pilot-scale activated
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sludge systems fed municipal waste-
water. The 28 RCRA (semi-volatile and
volatile) and 19 CERCLA (semi-volatile
only) chemicals (Table 1) were spiked
into the raw wastewater in two separate
test periods.
Experimental Systems and
Testing Approach
The two activated sludge systems
were operated at a flow rate of 35 gpm
and a hydraulic retention time (HRT) of
7.5 hr. An operational SRT of 4 days was
used in the RCRA study period. In the
CERCLA study period, the SRT was 8
days. Each compound was spiked at
0.25 mg/L for the RCRA study and at 0.5
mg/L for the CERCLA study. The
operating conditions and design char-
acteristics for the two systems used in
the study are given on the next page.
Both RCRA and CERCLA studies were
performed with an acclimated (con-
tinuous addition of toxicants) and an
unacclimated (intermittent spiking of
toxicants) system. These systems were
operated in parallel.
To sample from the air space above
the primary clarifier, the units were
covered and vented through a duct to the
Operating Conditions and Design Characteristics of the Pilot Systems
Design flow = 2.2 Us
= 191
Primary clarifiers -Diameter = 2.9 m
Weir diameter = 2.8 m
Surface area = 6.8 m2
Surface overflow rate = 28.0 m3/m2.d
Aeration basins - LW:D = 5.4 m:3.0 m:3.6 m
Surface area = 16.3 m2
Volume = 59.7 m3
Hydraulic residence time = 7.5 hr.
Secondary clarifiers -Diameter = 3.6 m
Surface area = 10.4 m2
Surface overflow rate = 18.4 m3/m2.d
roof. An air sweep equivalent to a 5
km/hr wind was maintained over the
surface of the primary clarifier by ex-
hausting air at 14,000 L/min. The
aeration basin was fitted with an air tight
cover and the off-gas was also vented to
the roof. Air flow in the aeration basins
averaged 5,600 L/min.
Automated analytical procedures were
used for the conventional pollutants
Table 1. RCRA and CERCLA Toxic Organic Pollutants
RCRA study period
CERCLA study period
acetone
cyclohexanone
furfural
2-butanone
4-methyl-2-pentanone
tetrahydrofuran
carbon tetrachloride
chlorobenzene
chloroform
1,2-dichloroethane
1,2-dichloropropane
methylene chloride
tetrachloroethylene
trichloroethylene
1,1,1-trichloroethane
1,1,2-trichloroethane
ethylbenzene
toluene
total xylenes
bis(2-ethylhexyl) phthalate
butyl benzyl phthalate
1,4 -dichlorobenzene
2,4 -dimethylphenol
2,4-dinitrophenol
naphthalene
nitrobenzene
4-nitrophenol
pheno
1,2-dichlorobenzene
1,3-dichlorobenzene
1,4-d/cWorobenzene
1,2,4-trichlorobenzene
nitrobenzene
1,3-dinitrobenzene
2,6-dinitrotoluene
p-cresol
4-chloroaniline
hexachloroethane
hexachlorobutadiene
dimethyl phthalate
diethyl phthalate
dibutyl phthalate
butyl benzyl phthalate
bis(2-ethylhexyl) phthalate
naphthalene
lindane
dieldrin
(COD, BOD, IMH4-N, NO3-N and TKN]
and Gas Chromatography/Mass Spec-
trometry (GC/MS) procedures were used
for the toxic organic compounds. RCRA
samples were analyzed by a contract
laboratory (PEI Associates Inc.,
Cincinnati, OH). Air samples, collected in
stainless steel canisters, were analyzed
by GC/MS. From these data, masses ol
each RCRA compound stripped during
the sampling event were calculated.
Sludge and liquid samples were also
analyzed by GC/MS according to
approved USEPA methods. Semi-volatile
RCRA compounds were extracted from
the samples with the use of continuous
liquid-liquid extraction. Prepared portions
of the extracts were injected into the
GC/MS for analysis. The semi-volatile
CERCLA compounds were analyzed
following Method 1625. Analyses were
performed at the EPA's Risk Reduction
Engineering Laboratory (RREL). Details
of the analytical procedures are in the
Project Report.
Three tests (sample collection events)
were performed during the RCRA study
period. For the CERCLA study, 11 tests
were done on the continuously spiked
(acclimated) system and 4 tests on the
intermittently spiked (unacclimated)
system.
Results
The presence of the spiked toxic
organics in the wastewater produced no
major adverse effects on the treatment of
conventional pollutants. Average re-
movals of conventional pollutants in the
pilot systems during the two studies
were between 94% and 97% for SS and
between 81% and 88% for COD. In the
RCRA study period, nitrification in the
activated sludge processes produced
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average NH4-N reductions between 76%
and 81% percent. In the CERCLA study,
the NH4-N removal was between 88%
and 98%. The CERCLA toxics (0.5 mg/L)
did interfere with nitrification in the
acclimated system.
Substantial variability occurred in the
reported results with some toxic com-
pounds, especially in the RCRA study
period. Table 2 lists average measured
concentrations of the selected RCRA
organics in wastewater and sludges for
the acclimated system. The difference
between the concentration of most toxics
in the spiked wastewater feed and
primary effluent was very small. The
primary sludge showed enhanced con-
centrations of the two phthalates and
naphthalene along with reduced concen-
trations in primary effluent; this indicated
adsorption onto sludge solids. Four
compounds (tetrahydrofuran, 1,2 dichlo-
roethane, methylene chloride, and 1,1,2-
trichloroethane) were present in the
secondary effluent stream in high con-
centrations (between 95 and 140 ug/L);
this indicated these organics were poorly
removed. Five other compounds (cyclo-
hexanone, furfural, 2,4-dimethyl phenol,
2,4-dinitrophenol and 4-nitrophenol) were
not evaluated because of inconsistent
results. The average removals of the
toxic compounds in the RCRA study are
summarized (Table 3). The removal of
RCRA organics with primary treatment
was between 3% and 44%. The total
removals were between 37% and 99%.
The calculated percent stripped for the
individual volatile compounds varied from
1% to 139%. No air analyses were
performed for the semivolatiles.. Biode-
gradation of a compound was estimated
by subtracting the measured removals by
adsorption and stripping of the compound
from the total removal. The estimated
biodegradation was between -42% and
97%. A negative biodegradation indicated
inconsistent mass balance and the prob-
lems of estimating biodegradation with
this approach. Biodegradation appeared
to be the predominant removal mecha-
nism for the polar solvents and the
aromatic volatiles (e.g., toluene: 72%,
xylenes: 66%, chlorobenzenes: 60%).
The unacclimated system (e.g., biodeg-
radation of toluene: 56%) showed similar
results, and no significant advantage of
acclimation was observed.
Table 4 lists the average concentra-
tions of the CERCLA organics. Five
compounds showed high concentrations
in the secondary effluents: 1,2,4-trichlo-
robenzene; 89 ug/L; 2,6-dinitrotoluene;
125 ug/L; p-cresol; 156 ug/L; lindane; 198
ug/L; and dieldrin; 99 ug/L. The average
removals of the toxic compounds in the
CERCLA study are summarized in Table
5. The removals of CERCLA organics in
primary treatment with the acclimated
system was between 4% and 79%. The
total removal varied between 56% and
98%. Biodegradation was estimated by
subtracting the removal by adsorption
from the total removal of a particular
compound. The extent of biodegradation
varied between 28% and 100%. The
unacclimated system also exhibited
similar removals. Biodegradation values
were similar for both acclimated and
unacclimated systems (e.g., naphthalene:
79% and dimethyl phthalate: 85%). As in
the RCRA study, no significant advantage
of acclimation was observed for the
CERCLA compounds. In the CERCLA
study period, the amounts of organics
found in the complex primary sludge
samples were substantially lower than the
measured removals across the primary
process. Because of the analytical
variability encountered in these studies,
additional work has been planned.
Conclusions
The following conclusions were drawn
from this study:
1. The polar solvents and aromatic vola-
tiles were biodegraded to a great
extent. For example, toluene ex-
hibited 72% and total xylene showed
66% biodegradation.
2. A significant amount of chlorinated
aliphatic solvents may be volatilized
from an activated sludge system.
The percent stripped varied between
1% and 139%.
3. Pesticides (lindane and dieldrin) were
removed both by adsorption onto
sludge and by biodegradation in the
secondary tank.
The full report was submitted in partial
fulfillment of Contract No. 68-03-4038 by
the University of Cincinnati under the
sponsorship of the U.S. Environmental
Protection Agency.
U.S. Environmental
Great Lakes Rational Program
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Table 5. Average Percent Removals of CERCLA Organics for the Acclimated System (Average of Eleven Test Runs)
Primary Total* Removed in Sludge+ Biodegradation
Compounds
Dichlorobenzene, Probably 1,2
Dichlorobenzene, Probably 1,3
Dichlorobenzene, Probably 1,4
1 ,2,4-Trichlorobenzene
Nitrobenzene
1 ,3-Dinitrobenzene
2,6-Dinitritoluene
p-Cresol
4-Chloroaniline
Hexachloroethane
Hexachlorobutadiene
Dimethyl phthalate
Diethyl phthalate
Dibutyl phthalate
Butyl benzyl phthalate
Bis(2-ethylhexyl)phthalate
Naphthalene
LJndane
Dieldrin
Removal
15.1
15.0
11.3
27.2
6.9
79.0
23.3
21.4
34.3
39.8
3.5
3.6
36.5
43.6
9.9
18.7
54.0
Standard
Deviation
11.7
9.9
11.6
15.0
12.8
9.8
18.5
35.2
16.2
13.6
6.2
7.8
10.7
11.3
9.6
8.0
15.2
Removal
93.4
88.9
95.3
85.1
92.8
96.7
68.2
73.9
87.6
97.1
96.2
98.1
97.6
96.1
96.9
97.9
55.9
81.4
Standard
Deviation
4.3
5.1
5.2
7.8
2.6
3.7
15.3
21.9
23.1
2.5
4.5
1.5
1.6
3.7
3.9
7.3
39.2
9.1
Removal
20
16
17
37
1
12
2
2
0
50
1
1
42
49
14
27
48
Standard
Deviation
9
10
9
12
1
15
1
1
tt
16
0
1
10
12
9
10
19
Removal
73
72
79
48
91
57
69
78
100
47
97
96
54
47
84
28
36
Standard
Deviation
10
11
10
14
3
38
21
28
•*
17
1
2
10
12
8
38
24
Total : Primary * Secondary
'Sludge : Primary * Waste Activated Sludge
" : Only one data point available
Sanjoy K. Bhattacharya and Rao V. R. Angara are with the University of Cincinnati,
Cincinnati, OH 45221; the EPA authors Dolloff F. Bishop, Jr., Richard A. Dobbs,
and Barry M. Austern are with the Risk Reduction Engineering Laboratory,
Cincinnati, OH 45268
Sidney A. Hannah is the EPA Project Monitor (see below).
The complete report, entitled "Removal and Fate of RCRA and CERCLA Toxic
Organic Pollutants in Wastewater Treatment," (Order No. PB 89-195 2001 AS;
Cost: $21.95, subject to change) will be available only from:
National TechnicaJ Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Monitor can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
U.S. Environmental Protection Agency
Great Lakes National Program Office
GLNPO Library
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EPA/600/S2-89/026
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