United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S2-90/013 Aug. 1990
&EPA Project Summary
Treatability of RCRA Compounds
in a BOD/Nitrification Wastewater
Treatment System with Dual
Media Filtration
Steven I. Safferman and Sanjoy K. Bhattacharya
The discharge of nitrogen and poten-
tially toxic or hazardous organic com-
pounds to the environment from
wastewater treatment plants has come
under scrutiny in recent years. Of
specific concern are the many organic
compounds excluded from Resource
Conservation and Recovery Act (RCRA)
regulations if they are discharged into a
wastewater treatment plant. This study
investigated the treatability and fate of 28
organic RCRA compounds in a combined
organic removal and nitrification process
and secondary effluent gravity filtration.
A 3.8 L/min pilot-scale extended aeration
wastewater treatment system with dual
media effluent filter was used for the
study. With a total concentration of ap-
proximately 1.5 mg/L organics (sum of
the concentration of all 28 RCRA com-
pounds) in the aeration basin, most of the
compounds were removed to below
detectable limits by secondary treatment
under either acclimated or unacclimated
conditions. The effectiveness of the ef-
fluent filter to remove organic com-
pounds could not be assessed as most of
the compounds entering the filter were
already reduced to below detectable
levels. Ammonia removal was sig-
nificantly impaired at a total concentra-
tion of 19.2 mg/L organics in the aeration
basin. COD reduction was apparently not
inhibited at any of the spike concentra-
tions tested.
This Project Summary was developed
by EPA's Risk Reduction Engineering
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 or-
dering information at back).
Introduction
The effects of discharging hazardous
wastes into the environment without ade-
quate treatment have become of increasing
concern to regulatory agencies and the
scientific community. Some of the com-
pounds associated with hazardous waste
can accumulate in the environment and are
mutagenic, teratogenic, or carcinogenic.
They can also volatilize into the atmosphere,
cause ground water contamination, and in-
hibit wastewater treatment processes.
Under the domestic sewage exclusion
statement, certain RCRA-regulated com-
pounds are exempt from RCRA regulations
if discharged into wastewater treatment
plants. Such compounds are assumed to
be treated adequately by the facility and to
cause no process interference.
The treatability of these compounds must
be assessed and their effect on the treatment
process understood. The specific objective
of this study was to investigate the treatability
and fate of selected organic RCRA com-
pounds in a combination BOD/nitrification
process. The importance of this objective is
realized when the recent changes in regula-
tions to require reduced ammonia discharge
are considered. Many wastewater treatment
plants that previously did not stabilize
nitrogen may now be required to do so.
One common means of achieving both
nitrification and carbonaceous BOD
removal is with an extended aeration sys-
-------
tern. In this study, 28 RCRA compounds
with a broad range of properties were spiked
into a pilot-scale extended aeration system
with dual media secondary effluent filters to
achieve the following goals:
• investigate the treatability and fate of the
selected RCRA toxics in the nitrification
process for both acclimated and unac-
climated conditions and
• determine the effectiveness of effluent
dual media filtration to remove the com-
posite RCRA toxics.
Procedure
To carry out the objectives of this project,
two 3.78 L/min pilot-scale extended aeration
wastewater treatment plants with dual media
secondary effluent filters were constructed
and operated at the U.S. Environmental
Protection Agency (EPA) Test and Evalua-
tion Facility (T&E) in Cincinnati, Ohio. The
hydraulic retention time of each system was
16.8 hr and the average solids retention time
was 21 days.
The influent was primary effluent from the
Mill Creek Wastewater Treatment Plant in
Cincinnati, Ohio; primary effluent from one
of two pilot-scale conventional activated
sludge systems at the T&E facility; or a com-
bination of both. Because the conventional
pilot systems were being spiked with the
RCRA compounds, this design allowed
spiking of the extended aeration systems
continuously or intermittently at various
toxics concentrations.
The 28 RCRA compounds were spiked
into the conventional pilot systems at several
different concentrations ranging from 0.25 to
1.0 mg/L of each organic. These com-
pounds were selected to ensure a good
representation of RCRA compounds with a
wide range of properties. The resulting ran-
ges were Henry's coefficient: 0.0000 to
0.944; and log octanol/water coefficient:
0.07 to 8.69.
The three phased project studied (1)
process interference caused by organic
RCRA compounds, (2) treatability and fate
of organic RCRA compounds, and (3)
removal of organic RCRA compounds by
dual media effluent filtration. A description
of the procedures for each phase follows.
PAiase 1, Process Interference
In this phase, the effect of the 28 RCRA
compounds on the ability of a pilot-scale
extended aeration wastewater treatment
plant to adequately treat the wastewater was
investigated. Chemical oxygen demand
(COD), nitrate, ammonia, and total Kjeldahl
nitrogen (TKN) were the primary process
control variables used to evaluate the
system's performance.
The performance was compared under
five different spike conditions:
• baseline, system performance before any
spike had been added;
• total spike concentration of 1.8 mg/L,
which was calculated by summing the
amount of each compound found from
each event and taking the average of the
three events;
• total spike concentration of 4.8 mg/L,
which were similarly calculated as above;
• total spike concentration of 19.2 mg/L,
which was calculated based on the spike
pump's setting; and
• discontinuation of spike.
Phase 2, Treatability and Fate
In this phase of the project, the concentra-
tion of the 28 compounds at different stages
of the treatment process were studied. The
influent spike concentration was about 0.1
mg/L for each compound, assuming mini-
mal removal by the primary clarifier. From
the literature and from preliminary opera-
tions, this initial concentration was selected
so as not to cause any process interference
to the system.
To investigate the removal and fate of the
compounds under both acclimated and un-
acclimated conditions, one of the extended
aeration systems was spiked continuously
with the RCRA compounds to allow the
microorganisms to become acclimated to
the toxics. The other system was spiked
only during sampling events so that the
microorganisms would not become ac-
climated.
Data were obtained from three sampling
events, each consisting of a 48-hr time
period. For the first 24 hr of each event, the
unacclimated system was spiked with the
RCRA compounds. For each event,
samples were taken every 4 hr and com-
posited for analysis of the RCRA com-
pounds.
Phase 3, Removal by Filtration
In this phase, the efficiency of dual media
effluent filtration to remove organic RCRA
compounds was investigated. To assess
the effectiveness, the concentration of each
compound was measured in the secondary
effluent (before entering the filter) and then
in the filter effluent. Data were obtained for
two secondary effluents:
• secondary effluent obtained from the ac-
climated extended aeration system, which
was being spiked at a total toxics con-
centration into the aeration basin of 1
mg/L and
• secondary effluent obtained from the a>
climated conventional system at the T&
facility, which was being spiked at a tot
toxics concentration into the aeratic
basin of 4.8 mg/L.
Samples were collected for RCRA con
pound analysis 11 times: 3 for the extende
aeration system's secondary effluent and
for the conventional secondary effluent.
Results and Discussion
Phase 1, Process Interference
The process control parameters of CO[
ammonia, and nitrate were used to gauc
the process interference caused by th
spiked RCRA compounds during Phase 1 c
this study. Four spike concentrations wer
tested. Figure 1 shows the percent remov;
of TKN and ammonia and the increase «
nitrate resulting from secondary treatmer
for each spike concentration. The trends i
the figure seem to indicate that nitrificatio
was inhibited even at a low spike concentre
tion, although ammonia reduction by secor
dary treatment was not inhibited until spik
concentrations between 4.8 and 19.2 mg/
were reached. After spiking ceasec
nitrification returned to its pre-spiking levi
within a few days. COD removal did nc
seem to be adversely affected by the spik
even at the highest composite concentratio
tested, 19.2 mg/L
To assess the interference of the RCR
compounds on an unacclimated system,
parallel system was intermittently spikec
The average total spike concentration (tot,
concentration of 28 compounds) was 1.
mg/L for three shock loadings, which ap
parently caused no inhibition of COD or air
monia reduction.
Phase 2, Treatability and Fate
The treatability and fate of the 28 organi
RCRA compounds spiked in Phase 1 at
total concentration of 1.8 mg/L was inves
tigated in Phase 2 for acclimated and unac
climated conditions. Composite samples c
aeration basin influent, secondary clarifie
effluent, and recycled activated sludge wen
collected three times for analysis of the com
pounds.
For the three sampling events from th<
acclimated system, all of the compounds
for which valid data were collected, wen
removed to below detectable limits (Tabk
1). The variations in the aeration basin in
fluent were probably caused by differen
removal rates of the compounds in the
primary clarifier, background concentra
-------
700
90
80 -|
70
60 -
50 -
40 -
30 ~i
20 ~
10 ~
% Removal of ammonia caused by seconday treatment
% Removal of TKN caused by secondary treatment
Increase in nitrate caused by secondary treatment, mg/L
I I I I I I I I I I I
0 2 4 6 8 10
Total spike concentration, mg/L
Figure 1. Acclimated conditions, ammonia, TKN, nitrate vs. concentration of spike.
I
12
]
14
I
16
I
18
Dns of the compounds in MSD's secondary
fluent and analytical errors.
For the three sampling events for the un-
:climated system (spiked intermittently at
i average total concentration of 1.3 mg/L),
ily four compounds had removals below
5%: 1,1,2-trichloroethane, bis(2-ethylhexyl)
ithalate, toluene, and nitrobenzene (Table
. The unacclimated conditions apparently
d not result in a significant reduction in
imoval efficiency at the RCRA compound's
Dncentration tested.
hase 3, Removal by Filtration
The secondary effluent from both the ac-
imated and unacclimated nitrification sys-
ms were passed through dual media
fluent filters for the first 62 days of the
•oject. The secondary effluent from the
Dnventional system was passed through
ne of the filters after day 62. Eleven
nalyses were run for the organic RCRA
impounds going into and coming out of
ie filter: three for the nitrification secondary
fluent and the others for the conventional
Astern.
The filters removed approximately 50% of
ie total suspended solids for most operat-
ig conditions. Because the secondary ef-
jent from the nitrification system had very
iw concentrations of RCRA compounds,
ie effectiveness of the filters could not be
assessed for the first 62 days of the project.
Higher concentrations of some of the com-
pounds were present in the secondary ef-
fluent from the conventional system. The
results indicate acetone, tetrahydrofuran,
tetrachloroethylene, and phenol had sig-
nificant removals by the filters (Table 3).
Values for these compounds, however,
were found only in Event 9. The remaining
compounds, for both Events 4 and 9, had
removals under 20%.
Conclusions
The following conclusions were drawn
from this study:
• COD removal was not inhibited at the
tested composite spike concentrations of
1.8, 4.8 (measured by summing the con-
centrations of all 28 compounds into the
aeration basin), and 19.2 mg/L (estimated
based on pump setting).
• Ammonia removal was significantly in-
hibited at the composite spike concentra-
tion of 19.2 mg/L (the sum of the
concentrations of all 28 compounds into
the aeration basin).
• Almost 100% of the spiked organic RCRA
compounds were removed when the
spike concentration was at 1.8 mg/L (the
sum of the concentrations of all 28 com-
pounds into the aeration basin) for the
acclimated condition and 1.3 mg/L for the
unacclimated condition.
• Adsorption did not appear to be a principal
mechanism for the removal of the RCRA
compounds.
Recommendations
This study indicates that an extended
aeration wastewater treatment plant can ef-
fectively remove low concentrations of or-
ganic RCRA compounds without interfering
with BOD, ammonia, and suspended solids
removal. Because of the many different
combinations and concentrations of RCRA
compounds that could be expected in the
influent to a municipal wastewater treatment
plant, a correlation between this study and a
real life situation is risky. Further studies and
surveys of actual extended aeration was-
tewater treatment plants are required to con-
firm these study findings, to determine if or
when harmful by-products are produced,
and to find the compound's removal
mechanism.
This report was submitted in fulfillment of
Contract No. 68-03-4038 by the University of
Cincinnati under the sponsorship of the U.S.
Environmental Protection Agency.
-------
Table 1. Summary of Sampling Events for Acclimated Conditions
Event 1 Event 2
Event 3
Compound
Cyclohexanone
Methy ethyl ketone
Methyl isobutyl ketone
Tetrahydrofuran
Carbon tetrachloride
Chlorobenzene
Chloroform
1 , 2-Dichloroethane
1 , 2-Dichloropropane
Tetrachloroethylene
Trichloroethylene
1,1,1- Trichloroethane
1 ,1 ,2'Trichloroethane
Ethylbenzene
Toluene
o-xylene
Bis(2-ethylhexyl)phthalate
Butyl benzyl phthalate
1 , 4-Dichlorobenzene
2, 4-Dimethylphenol
2, 4-Dinitrophenol
Naphthalene
Nitrobenzene
4-Nitrophenol
Phenol
ABI.
210
130
120
130
79
190
100
110
99
73
69
100
91
75
130
150
40
N
N
10
40
64
35
N
120
% REDSEC
100
100
100
100
100
100
100
1
100
100
100
100
95
100
100
100
100
NF
NF
100
100
100
100
NF
100
ABI.
N
150
N
N
64
110
81
93
67
64
62
70
74
65
110
21
40
13
N
N
N
77
N
N
N
% REDSEC
NF
100
NF
NF
100
100
100
100
100
100
100
100
100
100
100
100
85
100
NF
NF
NF
100
NF
NF .
NF
ABI.
N
148
N
63
70
100
90
96
74
66
70
77
72
95
170
42
45
N
42
N
N
67
68
32
180
% REDSEC
NF
100
NF
100
100
100
100
100
100
100
100
100
100
100
100
100
100
NF
100
NF
NF
100
100
100
100
AVG. ABI.
ML)
210
143
120
97
71
133
90
95
80
68
67
82
79
78
137
71
42
13
42
10
40
69
52
32
150
AVG.
% REDSEC
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
#
1
3
1
2
3
3
3
2
3
3
3
3
3
3
3
3
3
1
1
1
1
3
2
1
2
ABI.: Concentration into aeration basin,
AVG.: Average.
I: Influent concentration less than effluent concentration.
N: None detected.
NF: Compound not found in aeration basin influent
% REDSEC: Percent of compound reduced by secondary treatment.
#: Number of samples with valid values, out of 3.
Note: Acetone, Methylene Chloride, and Furfural were analyzed for but not found in feed or the compound was found in the blank.
-------
Table 2. Summary of Sampling Events for Unacclimated Conditions
Event 1 Event 2
Event 3
Compound
Cyclohexanone
Methy ethyl ketone
Methyl isobutyl ketone
Tetrahydrofuran
Carbon tetrachloride
Chlorobenzene
Chloroform
1 ,2-Dichloroethane
1 ,2-Dichloropropane
Tetrachloroethylene
Trichloroethylene
1,1,1-Trichloroethane
1, 1 ,2-Trichloroethane
Ethylbenzene
Toluene
o-xylene
Bis(2-ethylhexyl)phthalate
1 ,4-Dichlorobenzene
Naphthalene
Nitrobenzene
Phenol
ABI.
180
140
71
97
36
65
72
N
50
19
27
64
61
17
57
48
38
28
54
76
170
% REDSEC
100
100
100
100
100
100
100
NF
100
100
100
100
100
100
67
100
100
100
100
75
100
ABI.
N
240
N
N
N
76
36
12
31
36
25
N
24
77
96
130
22
22
50
32
130
% REDSEC
NF
100
NF
I
NF
100
100
100
100
100
100
NF
88
99
99
98
82
100
100
78
100
ABI.
N
330
75
N
35
73
66
N
40
32
46
50
42
45
120
66 B
15
24
38
36
220
% REDSEC
NF
100
100
NF
100
100
100
NF
100
100
100
100
90
100
100
100
100
100
100
81
100
AVG. ABI.
-------
-------
-------
Steven /. Safferman and Sanjoy K. Bhattacharya are with the Department of Civil and
Environmental Engineering, University of Cincinnati, Cincinnati, OH 45221.
Sidney A. Hannah is the Technical Project Monitor (see below)
The complete report, entitled "Treatability of RCRA Compounds in a BOD I Nitrification
Wastewater Treatment System with Dual Media Filtration" (Order No. PB 90-194
7051 AS; Cost: $17.00, 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 Technical Project Monitor can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
Official Business
Penalty for Private Use $300
EPA/600/S2-90/013
------- |