EPA440/5-77-017
PCBs REMOVAL
IN PUBLICLY-OWNED
TREATMENT WORKS
Criteria and Standards Division
U.S. Environmental Protection Agency
Washington, D.C. 20460
July 19,1977
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DISCLAIMER
This report has been reviewed by the Office of Water and
Hazardous Materials, U. S. Environmental Protection Agency, and
approved for publication. Mention of trade names or ccnroercial
products does not constitute endorsement or reccranendation for use.
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EPA440/5-77-017
PCBs HEMJVAL IN PUBLICLY-' 'L
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ABSTRACT
The removal of PCBs in each major unit process of publicly-owned sewage
treatment works CPOTWs) was quantified so that the removal efficiency results
may be applied to other POIWs. Two POIWs, differing widely in size and in
influent PCBs loading, were each sampled on a 24-hour basis for 7 to 10 days.
The overall PCBs removal efficiencies achieved were 83 to 89 percent,
slightly lower than the suspended solids removal efficiencies achieved at the
two plants. The steady-state PCBs removal efficiency of each unit process was
strongly correlated to the corresponding suspended solids removal efficiency.
In addition, large day-to-day variations in unit process PCBs removal efficien-
cies were correlated to variations about the mean influent PCBs and BOD con-
centrations.
Although reasonable PCBs material balances were achieved for one of the
two plants, PCBs removed from the wastewaters of the other plant could not be
accounted for in the sludges. PCBs loss by volatilization from the secondary
treatment processes was discounted as an important mechanism, the result of
explicitly analyzing the air emitted from the activated sludge aeration tanks.
The quantities volatilized were very small fractions of the PCBs removed from
the wastewaters.
11.
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TABLE OF CONTENTS
Page
1.0 SUMMARY 1
2.0 INTROXJCTION 5
2.1 Background 5
2.2 Approach 5
2.3 Potential Sources of PCBs to the POTWs 6
2.3.1 The Blocmington POTW 6
2.3.2 The Baltimore POTW 7
2.4 Structure of this Report 8
3.0 DESCRIPTIONS AND OPERATING DATA FOR THE POTWS 10
3.1 The Blocmington POTW 10
3.1.1 Plant Influent 10
3.1.2 Primary Clarification 10
3.1.3 Trickling Filter 14
3.1.4 Secondary Clarification 16
3.1.5 Polishing Lagoon 17
3.1.6 Sludge Processing 18
3.1.7 Operating Data 19
3.2 The Baltimore POTW 21
3.2.1 Plant Influent 21
3.2.2 Primary Clarification 21
3.2.3 Trickling Filter 25
3.2.4 Secondary Clarification ; 25
3.2.5 Activated Sludge System 26
3.2.6 Secondary Clarification 27
3.2.7 Sludge Processing 28
3.2.8 Operating Data 30
4.0 PROCEDURES FOR PCBs SAMPLING AND ANALYSIS 33
4.1 Collection, Transport and Compositing of Samples . 33
4.2 Analysis of Samples from the Bloomington POTW. . . 36
4.3 Analysis of Samples from the Baltimore POTW. ... 38
111.
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TABLE OF CONTENTS (Con't)
5.0 PCBS DATA AND ANALYSIS OF RESULTS 43
5.1 PCBs Concentration Data 43
5.1.1 Analysis of Variance in Concentration Data. 43
5.1.2 Uncertainty in Derived PCBs Removal
Efficiencies 48
5.2 Overall PCBs Removal Efficiencies 49
5.3 PCBs Removal in Primary Sedimentation 49
5.3.1 The Bloomington POTW Primary System .... 49
5.3.2 The Baltimore POTW Primary System 55
5.4 PCBs Removal in Secondary Treatment 56
5.4.1 The Bloomington POTW Trickling Filter
System 56
5.4,2 The Baltimore POTW Secondary Systems ... 56
5.5 PCBs Removal in the Bloomington Final Lagoon ... 58
5.6 Correlation of Unit Process PCBs Removal
Efficiencies 58
6.0 PCBs MATERIAL BALANCES 62
6.1 The Bloomington POTW 62
6.2 The Baltimore POTW 64
6.2.1 Measurement of PCBs in Sludges 64
6.2.2 Primary System 65
6,2.3 Secondary System 66
7.0 EXPERIMENTAL STUDY OF PCBs VOLATILIZATION 69
7.1 Laboratory Experiments 69
7.2 In-Situ Experiments at the Baltimore POTW .... 71
7.3 Conclusions 76
IV.
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List of Tables
1. Hydraulic Loading, Bloomington POTW Primary
Clarifiers 13
2. Comparison Among Independently-Measured Flow Rates,
Bloomington POTW 15
3. Total Flow and Suspended Solids and BCD Analyses,
Bloomington POTW 20
4. Hydraulic Loading, Baltimore PCTW Primary Clarifiers . 24
5. Activated Sludge Operating Data, Baltimore POTW. ... 29
6. Fluid Flow and Solids Balances, Baltimore POTW .... 31
7. Flow and Suspended Solids and BOD Analyses,
Baltimore POTW 32
8. Summary of Sampling Stations ........ 34
9. Precision of PCBs Measurements - Baltimore POIW. ... 42
10. PCBs Concentrations, yg/1 as Aroclor 1016 -
Bloomington POIW 44
11. PCBs Concentrations, ug/1 as Aroclor 1242 -
Baltimore POTW 45
12. Overall Removal Efficiencies 50
13. Removal Efficiencies, Bloomington POTW 51
14. Laboratory Vaporization Runs 72
15. Baltimore POTW Activated Sludge System, 2/77 76
v.
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LIST OF FIGURES
1. Bloonington POIW Schematic 11
2. Baltimore POIW Schematic 22
3. Chromatograms of Standard and of Typical Bloomington
Sample 37
4. Chromatogram of Typical Baltimore POIW Sample 39
5. PCBs Removal Efficiency vs. Influent PCBs Concentration. 52
6. PCBs Removal Efficiency vs. Influent BOD Concentration . 54
7. PCBs Removal Efficiency vs. Influent PCBs Concentration. 57
8. PCBs vs. Suspended Solids Removal Efficiencies 60
9. In-Situ Sampler 73
VI.
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ACKNOCECIGEMENTS
This report was prepared by the staff of Versar Inc., Springfield, Virginia,
under the overall direction of Dr. Robert L. Durfee, Vice President. Mr. Donald
H. Sargent, Mr. Roderick A. Carr, and Mr. Gregory A. Vogel were the principal
authors. The analyses for PCBs were conducted at the Versar laboratories by Mr.
Scott Powers, Mr. Vogel, and Dr. Mohantnad N. Khattak. Mr. Michael C. Calhoun
was the leader of the Versar field crew which conducted the 24-hour sampling at
the Baltimore POTW. Mr. Philip Powers and Mr. Vogel designed and fabricated the
air collector, and conducted this phase of the testing at the Baltimore POTW.
The considerable contributions of personnel of the Environmental Protection
Agency is acknowledged. Mr. R. Kent Ballentine of the Criteria and Standards
Division provided guidance as the Technical Project Officer. The sampling at
the Bloomington POTW was conducted by an EPA Region V crew from the Evansville,
Indiana field office, led by Mr. Richard Reising.
This project could not have been conducted without the full cooperation of
the personnel at the two POTWs. The assistance of Mr. Steven Drake, Superinten-
dent of the Winston Thomas plant at Bloomington; and of Mr. Paul S. Ander, Oper-
ations Engineer and Mr. Robert Mohr, Plant Manager, of the Back River plant at
Baltimore; is especially acknowledged.
Vll.
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1.0 SUMMARY
The removal of PCBs in publicly-owned treatment works (POTWs) was quanti-
fied by sampling each of two POTWs on a 24-hour basis for 7 and 10 days respec-
tively. The sampling was designed to yield PCB removal efficiencies for each
major unit process (primary sedimentation, secondary trickling filter and clari-
fication, secondary activated sludge and clarification, and tertiary polishing
lagoon) so that the results may be applied to other POTWs with different combina-
tions of major unit processes. Mass balances and engineering design and operating
data for the unit processes at the two surveyed PCTIWs are included in this report,
with comparisons to "typical" process data, to facilitate the application of
these PCB removal results to other PCTWs.
One of the two POTWs surveyed was the Winston Thomas STP at Bloomington,
Indiana. The raw sewage to this 3.6-mgd plant includes the discharge (to the
Bloomington municipal sewer system) of a major user of PCBs, which accounts for
the high level of PCBs in the influent to this POEW. The other POTW surveyed
was the Back River Wastewater Treatment Plant at Baltimore, JXkryland. Although
several minor industrial dischargers of PCBs are served by this 180-mgd POTW,
the PCBs in the influent are more generally attributable to diverse industrial
and domestic sources typical of a heavily-industrialized urban area.
Consistent with the sources of PCBs in the sewage to these two plants were
the types of PCBs found in the samples of wastewaters and sludges. Aroclor 1016,
the PCB used by the capacitor manufacturer at Bloomington, was identified as the
PCB in the POTW samples. The PCBs in the Baltimore POTW samples were more dif-
ficult to identify and to analytically determine, since their chromatograms did
not directly correspond to standards for commercial PCB mixtures. Identification
of the PCBs in the Baltimore samples was aided by mass spectrographic analysis.
The sampling procedures at the PCTWs were designed to avoid partitioning of
the PCBs, since PCBs strongly adhere to surfaces on sample bottles or on suspended
solids. Hence, individual samples were collected on an hourly basis (1,241 from
Bloomington and 1,035 from Baltimore) , and shipped to the laboratory, where they
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were carefully composited (into 71 composites from Bloonington and 55 from Balti-
more) and extracted with a hexane/methylene chloride mixture to ensure that all
of the PCBs would be included in the extracts. The extracts were concentrated
and subjected to gas chroraatographic analysis for PCBs.
Replicate sampling and analysis at each POTW resulted in a standard deviation
for each daily PCBs concentration measurement of 23 percent of the concentration,
which includes the errors introduced by sampling, compositing, extracting, concen-
trating, and chrcmatographic analysis. The sampling and 24-hour compositing pro-
cedures followed did not appreciably add to the measurement uncertainties introduced
by the laboratory procedures.
The average PCBs concentrations in the POTW influents were 145 yg/1 at the
Bloomington POTW, and 15 yg/1 at the Baltimore POTW. The overall PCBs removal
efficiencies achieved were 88 ± 2 percent for the Bloomington POTW, 89 ± 3 percent
for the activated sludge side of the Baltimore POTW, and 83 ± 4 percent for the
trickling filter side of the Baltimore POTW. These overall values are slightly
lower than the suspended solids and BOD removal efficiencies achieved by the two
plants.
The PCBs concentrations at each station in the Baltimore POTW exhibited no
greater' day-to-day variability than could be attributed to the measurement uncer-
tainty. The influent PCBs concentration at the Bloomington POTW, however, varied
much more widely, as it is sensitive to the day-to-day variations of the pre-
dominant industrial dischargers. This influent variability was reflected through-
out the treatment system, although the -system capacity provided some damping. For
the Bloomington POTW primary system, the PCBs removal efficiency (n) was found to
depend upon the influent PCBs concentration (C, yg/1) and upon the influent BOD
concentration (B, ma/1) :
= 53 + 33 .- 68B ~ 249
145 / wu\ 249
Similarly, the day-tfl-day PCBs removal efficiency for the Bloomington POTW
secondary system was found to depend upon the influent PCBs concentration:
=49+38
/C_-_56\
I 56 ) '
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A surrnary of the steady-state removal efficiencies for the individual unit
processes at the two POTWs is:
Bloomington Primary System 53 ± 9%
Bloomington Trickling Filter System 49 ± 6%
Bloomington Final Lagoon 31 ± 14%
Baltimore Primary System 46 ± 13%
Baltimore Activated Sludge System 82 ± 5%
Baltimore Trickling Filter System 71 ± 7%
Four of the above six individual unit process PCBs removal efficiencies
ware strongly correlated to the corresponding unit process suspended solids
removal efficiencies:
% - 65
n
nPCBs,
ss
% = 53 5 + 75 i '
^'3 + '*
One of the other unit processes was the Bloomington POTW final lagoon, which
exhibited a low apparent PCBs removal efficiency most probably because "old"
PCBs in the lagoon sediment were being resuspended and discharged (the PCBs
waste load to this POTW was higher in previous years) .
The other unit process not agreeing with the above correlation was the
Baltimore POTW primary system, which only achieved a 29 percent suspended solids
removal efficiency. The much higher PCBs removal efficiency is postulated to
result from an alternate mechanism; e.g. , scum removal.
Although reasonable PCBs mass balances were achieved for the Bloomington
POTW, the PCBs removal from the Baltimore POTW wastewater could not be accounted
for by the PCBs found in the sludges. The discrepancy in the Baltimore POTW
primary system could be explained by the alternate scum removal mechanism.
Two potential mechanisms were postulated for the disappearance of PCBs from
the Baltimore POTW secondary treatment process: biodegradation and volatilization.
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Since volatilization, if significant, would result in the direct re-release
of PCBs to the environment, a two-part experimental program was conducted to
explicitly determine the quantity vaporized. Laboratory experiments simulating
the Baltimore POTW aeration basins were conducted, followed by in-situ measure-
ments at the Baltimore POTW using a gas collection apparatus which isolated a
portion of the aeration basin. PCBs were indeed recovered from the air samples,
but the quantities were no greater than an equivalent 0.033 pounds per day from
the entire Baltimore POTW aeration basins. These quantities volatilized were
very small fractions of the PCBs quantities in circulation in the mixed liquor
or of the quantities removed from the wastewaters, and volatilization was dis-
counted as an important mechanism for the removal of PCBs from wastewaters in
PCTWs.
Biodegradation of Aroclor 1242, as indicated by disappearance in the labora-
tory experiments, was of sufficient magnitude to explain the disappearance of PCBs
from the secondary treatment processes at the Baltimore POTW. No direct measure-
ments of biodegradation rate were made, however, so that the disappearance mechanism
still remains unresolved.
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2.0 INTRDDUCTICN
2.1 Background
The U.S. Environmental Protection Agency (EPA) is currently involved in
the promulgation process for establishing effluent standards for toxic pollutants.
EPA has set forth final effluent standards for direct dischargers of polychlori-
nated biphenyls (PCBs), under Section 307 (a) of the Federal Water Pollution
Control Act Amendments of 1972 (FWPCA, PL92-500) in the Federal Register (42 F.R.
6532, Feb. 2, 1977). In the course of technical and economic studies to support
the proposed direct discharge standards for PCBs, it became evident that substantial
quantities were being discharged to publicly owned treatment works (POTWs). EPA
has authority under Section 307 (b) of the FWPCA to regulate the discharge of
pollutants to POTWs if the pollutants are toxic and disrupt the operation of the
POTW, or else pass through the POTW without sufficient treatment. The study des-
cribed in this report was therefore conducted to determine the efficacy of PCBs
removal by POTWs.
2.2 Approach.
The approach in this study was to collect hourly samples, on a 24-hour
basis, for 7 and 10 consecutive days, respectively, at each of two secondary POTWs,
and to analyze for PCBs the daily composite of the 24 hourly samples. The primary
objective was to measure the PCBs removal efficiency of each wastewater unit oper-
ation at these plants, such that the results might be projected to many other
POTWs which may have different design combinations of the wastewater unit operations.
The choice of the two POTWs for this study was based upon three major factors:
1. That the two treatment plants would have, between them, a good
representation of the major wastewater unit operations - primary
sedimentation, activated sludge secondary treatment, trickling
filter secondary treatment, and secondary clarification.
2. That there would be a sufficient concentration of PCBs, at least
in the POTW influent for each of the two plants, to avoid undue
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analytical difficulties and/or imprecision of the results. A
nominal target for the influent PCBs concentration was a nunimum
of about 10 ppb, so that the expected lower concentrations after
POIW treatment could be differentiated from the influent concen-
tration with some precision.
3. The geographic location of the POEWs with respect to the Versar analytical
laboratories, or in proximity of transportation facilities; to avoid
delays between sanpling and laboratory extraction and analysis. In addi-
tion, the plants must be large enough to require constant operator atten-
tion and to provide reliable laboratory analyses of classical parameters
(BCD, suspended solids, etc.)*
Two POTWs were chosen for study in response to the above factors:
1. The Winston Thomas Sewage Treatment Plant, Blootnington, Indiana, was
sampled for ten days fron September 20th through September 29, 1976.
This 3.6 mgd plant services (among other sources) the campus of Indiana
University at Bloonington, and most important, the Westinghouse Electric
Corporation capacitor manufacturing plant at Blooraington, a significant
user of PCBs.
2. The Back River Wastewater Treatment Plant, Baltimore, Maryland was
sampled for seven days from October llth through October 18, 1976. This
180 mgd plant services mostly domestic waste sources in the City and
County of Baltimore, but also (amounting to a significant wastewater quan-
tity) the manufacturing waste sources of this industrialized city which
by preliminary sampling was shown to contain significant quantities of
PCBs.
2.3 Potential Sources of PCBs to the POTWs
2.3.1 The BloomingtPn POTW
The major potential source of PCBs to the Bloomington POTW is
the discharge to the municipal sewage system of the Westinghouse Electric
Corporation capacitor manufacturing plant in Bloomington. This plant exclusively
uses Aroclor 1016 as the capacitor dielectric fluid. Test results of the plant
discharge, reported by Westinghouse, are:
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Date (1975)
V9
2/3
3/1
4/30
5/30
Discharge Flow,
gallons per day
189,481
162,069
134,924
118,637
106,177
Aroclor 1016
Concentration, ppb
3,900*
526
964
268
1,930
Aroclor 1016
Quantity, Ibs/day
6.16
0.71
1.08
0.27
1.71
*Average of two determinations; 4,600 and 3,170 ppb.
2.3.2 The Baltimore POIW
Three potential minor industrial sources of PCBs to the Balti-
more POTW have been identified. One is the Western Electric facility at 2500
Broening Highway, Baltimore, which in the past manufactured submarine cables
using Polycin 146, a two-conponent potting compound which contains up to 20 per-
cent by weight of Aroclor 1254. The total PCB use did not exceed 140 pounds for
the inclusive 1972-1975 period. Cables manufactured after 1975 utilized a non-
PCB potting compound.
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A second potential industrial source is the General Electric
transformer repair shop at 920 E. Fort Avenue, Baltimore, which has reportedly
ceased the use of PCBs as of July 1, 1976. This facility historically handled
about three PCB-containing transformer repair jobs each year (only about 5 per-
cent of all transformers contain PCB dielectric fluid). A typical transformer
would contain 200 to 300 gallons of fluid. The PCBs were purchased as n^cied
in 55-gallon drums, and were not stored in large quantities. During an EPA
survey on March 4, 1976, prior to the cessation of PCB usage at this facility,
a PCB concentration of 205 ppb was measured in an oil separator which discharges
to the municipal sewage system.
The third potential industrial source is the Westinghouse
Electric transformer repair shop in Baltimore. There is continuing repair of
6 to 8 PCB-containing transformers per year, each of which require about 500
gallons of fluid. The PCB fluid is ordered as needed in 55-gallon drums.
During an EPA survey on March 5, 1976, a PCB concentration of 690 ppb was
measured in a final sump, fron the washing and steam-cleaning areas, which dis-
charges to the municipal sewage system.
In industrialized areas such as Baltimore, it would be expected
that other sources of PCBs would be from the past general usage of PCB-based hy-
draulic fluids and heat-transfer fluids in manufacturing operations. Another
potential source to both Bloomington and Baltimore is toilet tissue and other
paper products; present-day tissue products which contain recycled paper, are
reported to contain 1 to 3 ppm of PCBs. Other general paths of PCBs into municipal
sewage include fallout from the atmosphere and storm water runoff from urban areas.
2.4 Structure of This Report
The first sections of the body of this report contain descriptions
and engineering characteristics of the unit processes in the two POTWs, with
details of the specific sample collection locations, and with the operating
histories during the survey periods. The next section describes the sampling
procedures employed, the handling and transport of the samples, the compositing
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of the samples at the Versar laboratory, and the analytical procedures employed
at this laboratory for determining PCBs. Next, "the data is presented for the
PCBs analyses, and the results are analyzed with respect to the PCBs removal
accomplished by each unit process, as influenced by the POTW operating conditions
and other factors. PCBs material balances are presented for each POTW. The final
section of this report is a presentation and discussion of data for the explicit
determination of PCBs volatilized from the Baltimore POTW.
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3.0 DESCRIPTIONS AND OPERATING DATA FOR THE POTWS
3.1 The Bloomington PQTW
The Winston Thonas Sewage Treatment Plant in Bloomington, Indiana,
is a 3.,6 mgd plant which features primary sedimentation, trickling-fliter
secondary treatment, and a polishing lagoon. Figure 1 is a schematic drawing
of this POIW.
3.1.1 Plant Influent
The plant influent consists of the flow from three trunk sewers,
plus two plant return flows which are added to one of these sewers. The two
return flows, shown on Figure 1, are the sludge from the secondary clarifiers
(A), and the supernatant from sludge digester No. 3 (B), which is the last of
four digesters in series. There is no access to measure or sample the influent
flow before the influx of the two return flows. MDreover, it was judged that
mixing among the three influent trunk sewers was not effective upstream of the
two aerated grit chambers (which have scum removal capability) . Hence, the in-
fluent flow rate and sampling station (identified as Point 1 on Figure 1) was
selected downstream of the degritters. Samples from this station were collected
from a manhole just downstream of the plant's magnetic flow meter. However, since
the calibration of the plant's flow meter was questionable, the influent flow rate
was independently measured with a rectangular suppressed weir in conjunction with
a Manning flow meter. It is this independent flow measurement that is the primary
measurement for this study, rather than the plant's meter.
3.1.2 Primary Clarification
As Figure 1 shows the flow from the degritters is split to
two banks of rectangular primary clarifiers, each with three independent tanks.
Each of the six basins is approximately 15 feet wide by 95 feet long, with a
water depth of about 10 feet. The volume of each basin is 105,000 gallons,
and the total primary clarifier volume is 630,000 gallons. The surface area
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TRICXUNG
PUMP?
10
II
'-MOON
12
«
12
JU»«E MTIMd SS5S
Figure !- Bloomington POTW Schematic
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per basin is about 1,420 square feet, and the total area for all six primary
basins is 8,500 square feet. At a nominal total flow of 3.6 mgd, the average
detention time is 4.2 hours and the average overflow rate is 420 gpd/sq. ft.
During all of the survey period at the Bloomington POTW, however,
the north bank of primary clarifiers had only two of the three basins in opera-
tion. The northern-most basin (the furthest from the south bank of clarifiers)
was dry, with maintenance being performed on the sludge collectors. However,
it was apparent that the flow through the north bank was greater than through
the south bank, probably due to asymmetry of the flow channels - the south bank of
clarifiers was the original set, with the north bank added in a later plant
expansion. Both banks, however, have the same basin dimensions. The actual
hydraulic loading during the survey period is shown in Table 1. The detention
time varied from 1.9 to 5.0 hours, and the overflow rate varied from 310 to 915
gallons per day per square foot. In comparison, a typical design parameter for
achieving good primary clarification of municipal wastewaters is 800 to 1,200
gpd/sq. ft. average overflow rate (where "good clarification" is 50 to 60 per
cent suspended solids removal and 30 to 35 per cent BOD removal).(1) According
to an alternate reference, primary sedimentation before trickling filters typically
has a detention time of 2.0 to 2.5 hours or has an overflow rate of 600 to 900
gpd/sq. ft. It appears that despite the hydraulic unbalance between the
two banks of clarifiers during the survey period, adequate capacity existed
in each bank to achieve good primary clarification.
The effluent from each bank of primary clarifiers was measured
and sampled in the channel which runs across the three basins. A rectangular
weir in conjunction with a Stevens Headstage Recorder and stilling well was
used to measure flow from each bank. These sampling and flow measuring
stations are identified in Figure 1 as Point 2 (north bank of primary clarifiers)
and as Point 3 (south bank).
Three independent measurements of plant flowrate were made at
the Bloomington POTW: the influent to the primary treatment system (including
return flows), the sum of the north and south primary effluents, and the
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Day
Avg. Dally Flf>w, inrjcl:
North
South
Avg. Detention, lirs:
North
South
Avlal flow Measurement
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effluent from the final lagoon. Since no direct measurements were made of
return flows, sludge flows, or bypassed flows at the Bloonington POTW, no
corrections to the plant flow rates could be made for individual unit pro-
cesses. Table 2 shows the comparison among the irxiependently-measured flow
rates - although significant daily differences occur, the averages for the
first eight days of the survey period are very close to each other.
A gate at the end of each of the two prajnary effluent channels,
upstream from the sampling and measuring stations 2 and 3, is used by the
plant personnel to bypass excess flow around the secondary treatment system.
Although no quantitative measure of bypassed flow was made, the gates were
opened during eight days of the ten-day survey period:
Hours of Secondary Bypass
1 6
2 4
3 10
4 6
5 0
6 0
7 10
8 19
9 7
10 20
3.1.3 Trickling Filter
The combined flow from the primary clarifiers (except for that
bypassed) is fed to a trickling filter bed via two siphon dosing tanks and
fixed nozzles. Each dosing tank feeds a distinct half of the bed, but there
is no physical boundary in the bed nor is there a separation of drainage from
the two halves of the bed. The total trickling filter bed, with stone media,
has a surface area of about 1.5 acres, a depth of about 9 feet, and a volume
of 588,000 cubic feet. The filter is a one-pass low-rate unit with no recycle.
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Table 2 - Comparison Among Independently-Measured Flew Pates,
"Bibaninoton POTW " '
Day
1
2
3
4
5
6
7
3
9
10
Average ,
Days 1-8
North Primary Effluent Plus
South Primary Effluent, mgd
3.81
3.63
2.99
3.30
3.65
3.25
4.04
4.29
3.62
Plant Influent,
mgd
2.95
3.45
3.72
3.05
3.19
3.04
4.06
3.94
4.35
4.35
3.43
Final Effluent,
mca
3.11
3.16
3.59
3.88
3.62
3.20
3.74
4.06
4.03
4.20
3.55
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The .hydraulic loading of the bed at the nominal flow of 3.6 mgd is 2.4 mgd/
acre, within the "typical" range of 1 to 4 mgd/acre.(1/2) During the
Blocmington survey period, the average BOD concentration of the trickling
filter influent (the primary effluent) was about 150 mg/1. At a nominal flow
rate of 3.6 mgd, the organic load to the trickling filter was 4,500 pounds
per day of BOD, or 7.7 pounds of BOD per day per thousand cubic feet. This
is at the lower end of the range of the organic loading for "typical" low-rate
trickling filters, 5 to 25 Ibs. BOD/day/1,000 cu. ft.(1'2)
Periodically, the Blocmington trickling filter is flooded to
kill filter fly larvae; and also periodically an insecticide is sprayed on the
boundary walls of the filter.
A sampling station (Point 6 on Figure 1) was established in a
wall just downstream of the trickling filter, upstream of where the flow divides
to the several secondary clarifiers. However, hourly samples were not collect-
ed at Point 6 (as they were at Points 1, 2, 3, 4, and 5). Instead, a sample
was taken from Point 6 once every 8-hour shift during the sampling period.
Dcwnstream of this sampling station, but upstream of the clarifiers, the under-
drain from the sludge drying beds (C on Figure 1) is returned to the main
plant stream.
3.1.4 Secondary Clarification
There are four secondary clarifiers at the Bloomington POTW:
the tvro original rectangular basins and the two circular clarifiers which
were added later. The approximate dimensions of each rectangular clarifier
basin are 20 feet wide by 65 feet long by 10 feet deep; each circular clarifier
is approximately 54 feet in diameter with depths from 10 feet at the sidewall
to 14 feet at the center. The total volume of all four secondary clarifiers is
660,000 gallons, and their total surface area is 6,600 square feet. The
volume of the circular clarifiers is 2.5 times the volume of the rectangular
clarifiers; and the surface area of the circular clarifiers is 75 per cent
more than the surface area of the rectangular clarifiers. Since no flow
-16-
-------
measurement for individual basins oould reasonably be made/ the entire group
of four secondary clarifiers was treated as an aggregate in this study. The
sludge from the secondary clarifiers (A in Figure 1) is returned to the head
of the plant.
At the nominal flow rate of 3.6 mgd, the detention time is
4.4 hours and the overflow rate is 550 gallons per day per square foot. In
comparison, "typical" final clarification following trickling filters is
characterized in the literature by average overflow rates of 400 to 600
gpd/sq. ft.(1), or alternately of 800 to 1,000 gpd/sq. ft.(2)
After the overflows frcm the four secondary clarifier basins
are rejoined, a sampling station (Point 4 in Figure 1) was established in a
wet well. Downstream of this sampling station, the water is pumped to the
polishing lagoon. There are two pumps, one running continuously and the other
running intermittently according to the level in the wet well. Each pump is
equipped with a running-time meter; readings were recorded during this survey.
Although there are provisions for bypassing a portion of the secondary clarifier
effluent directly to Clear Creek (the receiving stream) instead of to the lagoon,
no water was bypassed during the survey period.
3.1.5 Polishing Lagoon
The polishing lagoon is rectangular in shape and has a surface
area of 16.5 acres. The depth of water, to the sludge-sediment layer, was
roughly measured in this survey at about 5 feet. The influent spills into the
lagoon at its northeast corner and the final effluent to Clear Creek is at the
southeast corner. In this southeast corner, a dam isolates a small section of
the lagoon, with weirs for the influent to this section and for the final
effluent. A chlorine solution is added to the water in this section. The
final effluent flow rate was measured with a suppressed rectangular weir in
conjunction with a Manning flow meter, and a sampling station (Point 5 in
Figure 1) was established for the final effluent.
The effective volume of the Bloomington polishing lagoon is
approximately 27 million gallons. At a nominal flow rate of 3.6 mgd, the
-17-
-------
detention time is 7.5 days. Typically, detention tires of 7 to 30 days are
found for facultative lagoons. (2) At an average BOD concentration of 50 mg/1
for the influent to the Bloonington lagoon, the organic loading (at the
nominal 3.6 mgd) is about 1,500 pounds per day, or about 90 pounds of BOD per
day per acre. The organic loading for "typical" facultative lagoons is, in
comparison, 20 to 50 pounds of BCD per day per acre.
Six grab samples of sludge from the bottom of the lagoon were
taken on September 20, 1976, using a Petersen dredge. The sampling stations
(see Figure 1) were as follows:
Point 10 - North East Quarter (nearest to inlet)
Point 11 - East Central
Point 12 - South East Quarter (nearest to outfall)
Point 13 - South West Quarter
Point 14 - West Central
Point 15 - North West Quarter
3.1.6 Sludge Processing
The collected sludge from the primary clarif iers (D in
Figure 1) was sampled (one grab sample on September 20, 1976) from one of the
three piston pumps, Point 7 in Figure 1. This primary sludge is pumped to
Digester No. 1, and then Digesters No. 2, 4, and 3 (in that order) are used in
series. Digesters No. 1 and 2 are each about 50 feet in diameter and 33 feet
high, with volumes for each of about 500,000 gallons. They have gas mixers
and sludge heating via an external pump-around circuit. Digesters No. 4 and
No. 3 are each about 40 feet in diameter; No. 4 is about 25 feet high with a
volume of 240,000 gallons, and No. 3 is about 32 feet high with a volume of
300,000 gallons.
The supernatant from Digester No. 3, the last in series, is
returned to the head and of the plant (B in Figure 1) . The digested sludge
from the four anaerobic digesters is periodically sent to the bank of 13
drying beds, each with a capacity of 30,000 gallons. The underdrain from the
drying beds (C of Figure 1) is returned to the influent to the secondary
-18-
-------
clarifiers. Dried sludge fron the beds is presently being stockpiled at the
Blcxraington plant, since landfilling or soil conditioning use has been dis-
continued because of the high PCBs content of this sludge.
NO direct measurements ware made of the flow rate of primary
sludge or of its concentrations of total suspended solids and volatile solids.
Hjwever, the total suspended solids in the sludge may be estimated from the
difference between the TSS in the plant influent (average of 300 mg/1) and the
TSS in the primary effluent (average of 100 mg/1). At a nominal wastewater
flow rate of 3.6 mgd, the primary sludge solids would amount to 6,000 pounds
per day. At a typical volatile solids content of 0.7 for primary sludge,
the volatile suspended solids loading to the digesters would be 4,200 pounds
per day. ' Moreover, a typical primary sludge solids concentration of 3 per
cent implies a primary sludge volume for Bloomington of 24,000 gallons per
day. Using these estimated digester loadings in conjunction with the total
digester volume at Bloomington of 1,540,000 gallons (or 206,000 cubic feet)
results in an hydraulic retention time of 64 days and in a volatile suspended
solids loading of 0.020 pounds per day per cubic foot. In comparison, "typical"
primary sludge low-rate digesters have hydraulic retention times of 30 to 60
days and volatile suspended solids loadings of 0.04 to 0.1 pounds per day per
cubic foot.^2'3^ Typical high-rate digesters have 10 to 20 days retention times
(2 3)
and VSS loadings of 0.15 to 0.40 pounds per day per cubic foot. '
Using "typical" values for anaerobic digesters of 40 per cent
digestion of volatile solids and of 17 cubic feet of digester gas generated
per pound of digested volatile solids, the gas production at Blocmington
is estimated as 29,000 cubic feet per day.
3.1.7 Operating Data
The hydraulic data for the Bloomington POIW, measured by the
EPA field crew during the survey period, were presented in Tables 1 and 2.
Table 3 lists the suspended solids and BOD5 data, supplied by POTW personnel,
during this period.
-19-
-------
Table 3 - Total Flow are! Suspended Solids and BOO Analyses, mooiiiJngton POTW
I)
o
I
Total Flow, mgd
SSr mg/1:
Primary Influent
Primary Effluent
Trickling Filtox Kff .
Sec. Clarifier Eff.
Final lagoon Eff.
BCXV, mg/1:
Primary Influent
Primary Effluent
Trickling Filter Rff.
Sec. Clarifier Eff.
Final lagoon Eff.
"1
3.81
255
103
65
2}
5
240
108
55
44
21
2
3.63
292
12B
104
36
4
240
170
46
35
2]
r~i ~
2.99
328
100
70
11
4
313
155
86
54
22
Da
3.30
204
120
56
42
]2
250
152
97
45
20
Y of Sur
3.65
256
24
3
220
144
__
24
vey Period
6 7
3.25
507
50
5
305
148
14
4.04
212
00
53
25
25
220
114
54
47
23
"B
4.29
396
116
98
84
42
330
182
95
69
32
4.35
184
155
108
58
20
173
97
73
39
16
T T7X
10
4.35
244
120
72
24
20
203
150
63
33
16
Flow-Weighted
Average
3.77
283
102
81
40
15
246
141
72
46
21
-------
3.2 The Baltimore POIW
The Back River Wastewater Treatment Plant in Baltimore, Maryland, is
a 180 mgd POIW which has parallel trickling filter and activated sludge
secondary treatment units after a cannon primary treatment unit. Figure 2 is
a schematic drawing of this POIW.
3.2.1 Plant Influent
IXiring the sampling period of October 11-18, 1976, the influent
raw sewage to the plant had an average daily flow of 179 million gallons. A
sample of this raw sewage, upstream of any return flow additions, is regularly
taken by plant personnel from the influent chamber. Sampling station No. 1
was established at this same position.
Three return flows are added to the raw sewage upstream of the
primary clarifiers. The overflow from the sludge elutriation tanks (labeled
"A" in Figure 2), which averaged 1.9 mgd, is added at the influent chamber.
Return flow (B) is the sludge from the secondary clarifiers on the trickling-
filter side of the plant (these clarifiers are called humus tanks). This flow
averaged 0.9 mgd, and joiiis the main plant influent downstream of two parallel
bar screens. The third return flow (C), the overflow from the sludge thickener,
which is added downstream of the degritters, averaged 14.6 mgd. The total
flow into the primary clarifiers averaged 196 mgd (approximately 200 mgd).
Sampling station No. 2 was established at this point (shown in Figure 2), which
coincides with a sampling station regularly used by plant personnel, and with
plant flowmeters which measure the flow rates into each of seven parallel
primary clarifiers.
3.2.2 Primary Clarification
The seven circular primary clarifiers are each 12 feet deep
at the sidewall and 21 feet deep at the center. Clarifiers No. 1 ard No. 2
are each 200 feet in diameter, and each has a volume of 3,520,000 gallons arcl a
surface area of 31,400 square feet. Clarifiers No. 3, 4, 5, 6, and 7 are each
170 feet in diameter, with a volume of 2,550,000 gallons and a surface area of
-21-
-------
StWER
] BflR SCRffMS
[ } ofar.mr.Rs
"
f ICMIORINATION
f'
EFFLUENT
TO BACK RIVER
AERATION
TANKS
SECONDARY
CLARIFIERS
OtOfSiTTERS
VACUUM
FILTERS
SLUOOE CAKE TO
SANITARY LANDFILL
EFFLUENT TO
BETHLEHEM STEF.L CO.
TREArMENT PLANT
Figure 2-Baltimore POTW Schematic
-------
22,700 square feet. The totals for all seven clarifiers are 19,790,000 gallons
volume and 176,300 square feet surface area. At an average total flow of 200
mgd, the average detention time is 2.37 hours, and the average overflow rate
is 1,130 gpd/sq. ft. The total flow is usually divided among the seven
clarifiers so that both the detention time and the overflow rate are the same
for all: the average flow to each of Clarifiers No. 1 and No. 2 is nominally
35.6 mgd, and the average flow to each of Clarifiers No. 3, 4, 5, 6, and 7 is
nominally 25.7 mgd.
However, Clarifier No. 7 was out of service during the sampling
period of October 11-18, 1976. The hydraulic loadings for the remaining six
clarifiers during this period are listed in Table 4.
During the high flow period in the diurnal cycle, the flow
peaked at about 117 per cent of the average daily flow, with corresponding
effects upon the clarifier loadings.
In comparison, a typical design parameter for achieving good
primary clarification of municipal wastewaters is 800 to 1,200 gpd/sq. ft.
average overflow rate. According to an
primary sedimentation data are applicable:
average overflow rate. According to an alternate reference, the following
Detention Time, Overflow Rate,
Hours gpd/sq. ft.
Before .Activated Sludge Secondary 0.75 - 1.0 1,000 - 1,500
Before Trickling Filter Secondary 2.0-2.5 600 - 900
It appears, then, that with the one clarif ier out of service
during the sampling period, the remaining clarifier capacity may have been
marginal for achieving good primary sedimentation.
A total of about 2.1 mgd of primary sludge is removed from
the primary clarifiers (labeled "D" in Figure 2) . Of the 198 mgd of overflow
from the clarifiers, about 1.7 mgd are removed and used as plant flushing water
(E). The remaining primary effluent flows by gravity down a long channel along-
side the trickling filter bed, and several cross-connections feed approximately
-23-
-------
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-------
150 mgd to the bed. Sanpling station No. 3 (shown in Figure 2) was established
in the long channel, approximately midway along the bed. The approximately 46
mgd of primary effluent, remaining in the channel after the trickling filter
influent is withdrawn, continues flowing in the channel to the activated sludge
process units. By sunroer of 1977, the flow of primary effluent to the activated
sludge process will be increased to 60 mgd.
3.2.3 Trickling Filter
The trickling filter is a one-pass low-rate unit with no re-
cycle. The total bed area is 30 acres, and is filled to a depth of 8.5 feet
with trap rock of 1 to 2 1/2 inch size. The total bed volume is 11,110,000
cubic feet. Most of the bed is fed by 50 rotary distributors, each 157 feet
in diameter. One of these distributors has a flow range of 4.02 to 8.04 mgd,
while the other 49 each has a range of 1.34 to 2.68 mgd. The remainder of the
trickling filter bed is fed by 5,830 fixed nozzles.
The hydraulic loading of the entire bed, at the average flow
(during the sanpling period) to the bed of 150 mgd, was 5 mgd/acre, compared
to the "typical" range of 1 to 4 mgd/acre.' ' ' During the sampling period,
the average BOD concentration of the trickling filter influent (the primary
effluent) was 154 mg/1. At an average flow rate to the trickling filter of 150
mgd, the organic load to the filter was 193,000 pounds per day of BOD, or 17.3
pounds of BOD per day per thousand cubic feet. This value is within the range
of the organic loading for "typical" low-rate trickling filters, 5 to 25 Ibs.
BOD/day/1,000 cu. ft.(1'2)
3.2.4 Secondary Clarification (After Trickling Filter)
Two streams are withdrawn from the main effluent from the
trickling filter, upstream of the humus tanks. About 13.4 mgd is withdrawn as
dilution water (labeled "G" in Figure 2) for the primary sludge; and about 1.4
mgd (labeled "H") is withdrawn as elutriation water. The remaining 135 mgd of
trickling filter effluent flows to five parallel secondary clarifiers, called
"humus tanks" at the Baltimore POTW. Four of these tanks (Nbs. 1A, IB, 2A,
and 2B) are rectangular, each with dimensions of 143 feet by 276 feet by 10
-25-
-------
feet deep. Each has a surface area of 39,500 square feet and a volume of
2,950,000 gallons. The fifth humus tank (No. 3) is circular, with a diaiteter
of 170 feet, a depth ranging from 11 to 17.5 feet, a surface area of 22,700
square feet, and a volume of 2,230,000 gallons. The totals for all five
secondary clarifiers are 180,700 square feet surface area and 14,030,000
gallons volume. At an average total flow of 135 mgd, the average overflow
rate is 750 gpd/sq. ft., and the average detention time is 2.49 hours. The
total flow is actually divided among the five clarif iers so that the overflow
rate is the same for all (750 gpd/sq. ft.). The average flow to each of the
rectangular clarif iers is 29.6 mgd, and the average flow to the circular clari-
fier is 17.0 mgd. The detention times, therefore, are 2.39 hours in the
rectangular clarifiers and 3.15 hours in the circular clarifier.
In comparison, "typical" final clarification following
trickling filters is characterized in the literature by average overflow rates
of 400 to 600 gpd/sq. ft.,(1) or alternately of 800 to 1,000 gpd/sq. ft.(2)
The sludge from the humus tanks (labeled "B") is returned to
the head of the plant. This flow averaged 0.9 mgd during the survey period.
A grab sample of this sludge was taken (at Point 8 in Figure 2) for PCB analysis.
A sampling station (Point 6 in Figure 2) was established just
downstream of the circular humus tank. The plant personnel regularly take
samples at this same point.
The combined overflow from all five humus tanks is submitted
to chlorination before discharge to Back River. As Figure 2 shows, there is
a cross-connection which allows this treated water to be alternately discharged
to the Bethlehem Steel Company treatment facility at the Back River Plant;
after settling and chlorination; this treated water is then used by Bethlehem
Steel at Sparrows Point.
3.2.5 Activated Sludge System
The primary treatment effluent which is not fed to the trick-
ling filter is subjected to activated sludge secondary treatment. Sampling
-26-
-------
point 4 was established at the end of the long channel from the primary
clarifiers, just upstream of the activated sludge units.
The activated sludge process at the Baltimore POTW consists
of two parallel units, each with two aeration tanks and two secondary clari-
fiers. As Figure 2 shows, there is a common return sludge line for the two
units. Each of the four aeration tanks is actually a set of two rectangular
basins: the influent (primary effluent) and the return sludge are both fed at
the head of one basin, the mixed liquor flows to the end of that basin, and
is then turned 180 degrees into the second parallel basin. These units are
conventional activated sludge, with the flow closely approximating plug flow.
Each basin is 386 feet long and 30 feet wide, with a mixed-liquor depth of
15.3 feet. Each of the four aeration tanks (consisting of two basins) has a
volume of 346,000 cubic feet, or 2,590,000 gallons.
Aeration tanks No. 3 and No. 4, and the corresponding final
clarifiers No. 3 and No. 4, are very recent additions to the plant. During
the survey period of October 11-18, 1976, the total settled sewage (activated
sludge influent) feed rate to Units No. 3 and No. 4 averaged 29.5 mgd. From
October 11-17, the total settled sewage feed rate to Units No. 1 and No. 2
averaged 16.1 mgd; these two units were taken out of service for renovation
after October 17th.
3.2.6 Secondary Clarification (After Activated Sludge)
The mixed liquor from aeration tanks No. 1 and No. 2 flows to
two parallel circular clarifiers, each 126 feet in diameter, with a surface
area per tank of 12,500 square feet and with a volume per tank of 1,330,000
gallons. Similarly, each of the two circular clarifiers downstream of
aeration tanks No. 3 and No. 4 is 180 feet in diameter, with a surface area of
25,400 square feet per tank and with a volume per tank of 2,300,000 gallons.
For all four activated sludge units together, an average of
0.94 mgd. of settled sludge was wasted. This sludge (labeled "F" in Figure 2),
is added to dilution water from the trickling filter before mixing with the
-27-
-------
primary sludge prior to treatment in the sludge thickener. A grab saraple (No.9
on Figure 2) was taken of the return sludge, and another (Kb. 10) of the mixed
liquor from aeration tank No. 2, for PCB analysis.
Table 5 lists average operating data for the two activated
sludge units, for the survey period. Also listed in this table are "typical"
design and operating data for the conventional activated sludge process,
including final clarification. In most respects, the operation of the acti-
vated sludge units at the Baltimore POTW was within the ranges for "typical"
operation.
A sampling station (No. 5 on Figure 2) was established in the
cannon channel for the overflow from all four secondary clarifiers. This
treated water flows to the Bethlehem Steel Company plant at Sparrows Point,
where it is used as cooling water. As Figure 2 shows, there is a cross-
connection which allows this treated water to be alternately discharged (after
disinfection) to Back River.
3.2.7 Sludge Processing
The right-hand side of Figure 2 shows the sludge processing
operations at the Baltimore POTW. Primary sludge (labeled "D"), averaging 2.1
mgd, flows through high rate degritters, and then is combined with a total flow
of 13.1 mgd, made up of 0.9 mgd of wasted activated sludge (F) and of 12.2
mgd of dilution water from the trickling filter (G). The combined 15.2 mgd
flows to 6 parallel sludge thickeners (two additional thickeners were out of
service during the sampling period). The thickened sludge fron all thickeners
amounted to 0.57 mgd during the sampling period; the thickener overflow ("C"
in Figure 2) of 14.6 mgd is returned to the head of the plant. A grab sample
of thickened sludge (Point 11 on Figure 2) was obtained for PCB analysis.
There are six anaerobic high-rate sludge digesters in parallel,
to which the thickened sludge is added. These digesters are maintained at 90
to 95°F with external recirculation and heat transfer circuits. The gas from
one of the digesters was passed through a PCB-adsorbing column, which was then
subjected to analysis. This is labeled as Point 13 on Figure 2. The total gas
production from the digesters is normally 1,500,000 cubic feet per day; at the
-28-
-------
Taola 5 - Artivated Sludge Operating Data, Baltimore PCTW
Influent Flow, mgd
Influent SS, m;/l
Influent BCD, mg/1
Return Sludge Flow, ragd
Air Usage, million CF/day
MLSS, mg/1
MLVSS, mg/1
ML D.O. , mg/1
Sludge Volune Index, al/a
Effluent SS, mg/1
Effluent BOD, mg/1
Sludge Recycle, % of Influent
Aeration Detention Tine, hrs.
Sludge Retention Time, days
Organic loading. It BOD/day/lt MLSS
F/M, It BCO/day/li) MLVSS
Volumetric loading, It BOD/day/1000 CF
darifier Loading, Its solids/day/ sq . ft.
Air Supplied, CF/lb 300 removed
Air Supplied, CF/gallon total flow
SS Raraoval Efficiency, ?er Cent
BOD Renewal Efficiency, Per Cent
darifier Overflow Rate, g?d/sq. ft.
darifier Detention Time, his.
Tanks No. 1 I No. 2
16.15
120
154
4.31
36.30
1,475
990
5.6
87.4
8.5
11.3
26.7
6.08
3.9
0.326
0.485
29.9
11.8
1,890
1.78
92.9
92.7
820
3.12
Tanks No. 3 t No. 4
29.56
120
154
7.49
49.75
1,858
1,250*
4.0
84.0
8.9
14.7
25.3
3.35
2.7
0.475
0.708
55.0
10.5
1,440
1.34
92.6
90.5
730
2.98
Typical" Data'1'2'
2,000-, 2500 (4)
50-100 (4)
6-8C1),ll6<2>~4-8(4)
5-15 (l)
0.2-0.3 !2'4'
0.3-0.5
2 WO (1)
800-1 , 500 (1 ' 4 } , 768-1 , 000 t2 '
0. 4-1.5 (2),0. 5-2 (4)
85-95
85-95 (1'
400-800 (1) ,800-1,000 (2!
2-3 (2!
ML.VSS for Tanks No. 3 & No. 4 estimated, based upon sane MLVSS/KIS5 ratio as Tanks No. 1 and No. 2.
-29-
-------
time of this survey, the production was 893,000 cubic feet per day. Sate is
used for heating of the digesters and plant buildings. The digested sludge was
withdrawn at an average rate of 0.62 rogd during the sampling period. A grab
sanple (Point 12 in Figure 2) was obtained for PCS analysis.
An average of 1.41 mod of elutriation water (labeled "H")
fron the trickling filter, plus about 0.34 rngd of filtrate from the sludge
vacuum filters, are added to the digested sludge, for a total of 2.37 mgd
influent to two elutriation tanks in series. A polymeric flocculant is also
added to the elutriation tanks. The overflow fron the final elutriation tank
(labeled "A"), amounting to 1.94 mgd, is returned to the head of the plant.
Additional polymer is added to condition the 0.43 mgd of
transfer sludge prior to vacuum filtration. The filter cake, averaging 469
tons per day, with a solids content of 19.1 per cent, is then transported to
sanitary landfill.
Table 6 is an approximate iraterial balance of the Baltimore
PCTW, both for fluid flow and for solids. The balances may not exactly check
cut because of imprecision in measuring flews and concentrations, and because
large capacities (e.g., sludge in the aerators, in the thickeners, and in the
digesters) ray have resulted in non-steady-state data for the survey period.
3.2.8 Operating Data
Table 7 lists the hydraulic, suspended solids, and organic
loading data for the Baltimore POIW during the survey pericd, as supplied by
the POTW personnel.
-30-
-------
Table 6
Fluid Flew and Solids Balances, Baltimore POIW
Stream Identification (Figure 2)
Raw Influent Sewage
(A) Elutriation Tank Overflew Return
(B) HXCTIS Tank Sludge Return
(C) Thickener Overflew Return
Primary Treatment Influent
(D) Primary Sludge to Thickener
Primary Treatment Effluent
(E) Flushing Water Drawn Off
Trickling Filter Influent
(G) Dilution Water to Thickener
(H) Elutriaricn Water to Elut. Tanks
Sonus Tank Influent
Humus Tank Overflow (Effluent)
Influent to Activated Sludge Units
Serum Sludge to Aerators
Influent to Act. Sludge Clarifiers
Effluent fron Act. Sludge Clarifiers
(F) Wasted Activated Sludge to Thickener
Total Saturn & Wasted Activated Sludge
Total Influent to Thickener
Thickened Sludge to Digester
Digested Sludge to Elutriaticn
Filtered Sludce Cake to Tjarnr-i 1 7
Flow Rate,
mod
176.6
1.94
0.89
14.64
194.1 *
2.09*
192.0
1.69
144.5
12.19*
1.41*
131.0
130.1
45.71*
11.30*
57.51
44.77
C.94
12.74*
15.22
0.57
0.62*
SS Cone. ,
rag/1
165*
229 (a)
1,790
229 (a)
178*
4,220
134*
134*
134*
41*
41*
41*
29*
120*
7,930
1,720*
9*
7,930
7,930
1,100
43, 900 (h)
33,900
Solids in
Stream,
Pounds/Day
243,000
3,700
13,300
27,900
237,000
73,300
214,000
1,900
161,000
4,200
500
44,700
31,400
45,600
780,000
825,000
3,400
62,300
341, COO
139,300
209,300
175,200
172,000
*Measured by Baltimore ?OTW
(a)Estimated Equal S3 Concentration for Streams A&C
Cb)Measured by Versar
-31-
-------
Table 7 - Flow and Sustiended Solids and BOD Analyses, Baltinore POIW
IO
I
Flow Rate, mrjtl:
1. Plant Influent
2. Primary Influent
3. Trickling Filter Influent
4. Activated Sludge Influent
5. Activated Sludge Effluent
6. Humus Tank Effluent
7. Plant Effluent to River
Suspended Solids, mcj/1:
1. Plant Influent
2. Primary Influent
3. Trickling Filter Influent
4. Activated Sludge Influent
5. Activated Sludge Effluent
6. Humus Tank Effluent
7. Plant Effluent to River
B0t>5, mg/1:
1. Plant Influent
2. Primary Influent
3. Trickling Filter Influent
4. Activated Sludge lnfl\K?nt
5. Activated Sludge Effluent
6. Humus Tank Effluent
7. Plant Effluent to River
Bay of Survey Period
1
189.8
207,3
157.6
46.0
45.2
141.9
114.9
188
180
200
140
9
41
18
138
119
132
142
10
7
6
2
188.8
206.3
15C.1
46.2
45.2
140.5
103.9
187
152
90
104
4
18
18
146
130
124
126
6
5
2
3
183.2
200.7
153.0
43.8
42.9
140.1
__
104
40
36
4
7
13
179
183
148
187
16
20
18
4
184.2
201.7
151.8
46.2
45.3
136.3
254
224
164
176
19
50
29
151
154
115
146
14
24
22
5
182.3
199.8
150.8
45.9
45.0
135.1
76.6
168
196
92
96
6
14
20
91
171
82
6
22
6
6
174.2
191.7
141.8
45.9
45.0
126.0
73.3
206
228
140
136
12
34
25
176
218
208
199
22
48
22
7
169.4
186.9
137.7
45.4
44.3
121.7
68.8
137
180
168
120
9
37
26
200
196
166
162
13"
18
13
8
176.6
194.1
159.8
30.2
29.2
143.7
72.8
167
156
178
152
8
32
31
179
183
148
187
18
20
18
Flow-Weightod
Average
181.1
198.6
151.1
43.7
42.8
135.7
85.1
187
177
134
116
9
29
22
157
168
151
151
13
20
10
-------
4.0 PROCEDURES FOR PCBS SAMPLING AND ANALYSIS
4.1 Collection/ Transport, and Compositing of Samples
Table 8 summarizes the stations at the two POTWs for tne coj.Ieeciuu ul
samples for subsequent PCB analysis, the sample station locations are shown on
Figure 1 for Bloomington and Figure 2 for Baltimore. The main wastewater streams
at the plants (BL-1 through BL-5, and BA-1 through BA-6) were sampled once each
hour, 24 hours per day for the duration of the sampling periods, into individual
100-ml graduated glass bottles. The sampling periods were 10 days at Bloomington
and 7 days at Baltimore. For stations BL-6 and BA-7, one sample was collected
into a quart bottle once each 8-hour shift for the duration of the sampling period.
Each of the sludge and sediment samples (BL-7, BL-8, BL-10 through BL-15, and BA-8
through 12) was a single grab sample collected in a quart bottle. Each individual
wastewater, sludge, and sediment sample was collected in its own bottle, which had
previously been cleaned and dried. Teflon or aluminum foil cap liners were used.
The field crew preserved each sample with a 37 per cent formalin solution (1.5 ml
per 100 ml of sample).
The digester gas sample (BA-13) was an adsorbent column through which
digester gas at a controlled and measured flow rate was passed for a measured
time period.
The 1,241 individual samples at the Bloomington POTW were collected
by an EPA field sampling crew from the Evansville, Indiana, field office of
EPA Region V. The preserved samples were refrigerated and shipped via air
freight once each day to Washington National Airport, and then transported by
Versar personnel to the Versar Springfield, Virginia , laboratories where they
were again placed under refrigeration. The total transport time from the
Bloomington POTW to the Versar laboratory was about 6 hours. The EPA Region V
Chain of Custody Procedures were adhered to.
The 1,035 individual samples at the Baltimore POTW were collected by
a Versar field sampling crew. The preserved samples were transported once
each day (a 2-hour trip) to the Versar Springfield, Virginia , laboratories where
they were placed under refrigeration.
-33-
-------
Table 8 - Summary of Sampling Stations
(BL » Bloomington, BA = Baltimore)
Station
BL-1
BL-2
BL-3
BL-4
BL-5
BL-6
BL-7
BL-8
BL-10, 11,12, 13,14, 15
BA-1
BA-2
BA-3
BA-4
BA-5
BA-6
BA-7
BA-8
BA-9
BA-10
BA-11
BA-12
BA-13
Description of Samcled Stream
Primary Influent
North Primary Effluent
South Primary Effluent
Secondary Clarifier Effluent
Final Lagoon Effluent
Trickling Filter Effluent
Primary Sludge
Digested Sludge
Lagoon Sediment (6 locations)
Plant Influent
Primary Influent
Trickling Filter Influent
Activated Sludge Influent
Activated Sludge Clarified Effluent
Trickling Filter Clarified Effluent
Final Effluent
Sludge, Trickling Filter Clarifier
Sludge, Activated Sludge Clarifier
Mixed Liquor from Aerator
Thickened Sludge
Digested Sludge
Digester Gas
Type of
Samples*
H
H
H
H
H
S
G
G
G
H
H
H
H
H
H
s
G
G
G
G
G
A
Number of
Samples
240
240
240
240
240
30
2
3
6
168
168
168
168
168
168
21
**.
1
1
1
1
1
1
* Type of Samples:
H - Hourly, 24 per day
S - Once each 8-hour shift, 3 per day
G - Single grab sample during sampling period
A - Adsorbed from gas stream, once during sampling period
-34-
-------
At the Bloomington POIW, each of the wastewater samples CBL-1 through
BL-5) was (roughly) volumetrically proportioned according to the hourly plant
influent flow rate, on the basis of 100 ml for each sample for the maximum
hourly flow rate, using the graduations on the sample bottles. At this small
plant, the field crew had relatively easy manual access to the flow channels
to permit this partial filling operation. At the much larger Baltimore POIW,
however, the field crew was forced to use a bottle holder at the end of a long
pole to reach the wastewater in the channels, prohibiting the partial filling
of a bottle. Hence, all wastewater samples from Baltimore were full bottles.
The basic sampling procedure followed at both Blocmington and
Baltimore ^5 designed to strictly avoid any technique which might partition
PCBs. Since PCBs adhere to the glass surfaces of bottles, and strongly adhere
to finely-divided suspended solids in the wastewaters, each sample was collected
in a clean and dry bottle without pre-rinsing of the bottle in the wastewater
stream, without emptying part of a collected sample from a bottle (which pre-
cluded flow proportioning at Baltimore), and without any transfer of sample
between bottles. This basic principle of avoiding PCBs partitioning was the
reason for individual sample bottles to be shipped to the laboratory, as opposed
to the conventional procedure (used for parameters other than PCBs) of com-
positing in the field. Such compositing would have biased the results by
leaving PCEs in the original collection bottles.
For each main sampling station (BL-1 through BL-5, and BA-1 through
BA-6), 24 individual samples were collected for each day of the survey period.
The 24 samples were combined by adding all of each sample to the daily composite.
The composite aqueous sample was then extracted with the hexane/methylene
chloride, at a volumetric ratio of 2:1 (aqueous:organic). The organic extract
was then concentrated by evaporation, to 10 ml. Each of the grab samples was
similarly extracted and concentrated.
After compositing, the number of samples subsequently extracted,
concentrated, and analyzed was 126 (71 from the Bloomington POTW, and 55 from
the Baltimore POTW).
-35-
-------
daily composite PCBs samples fron the Bloonington POTW correspond
with the daily flow, suspended solids, and BOD data. However, the PCBs samples
from the Baltimore POM were collected (and composited) for 24 hours starting
at 12 noon - the first "day" was 10/11/76 - 10/12/76. Ihe flow, suspended
solids, and BCD data from the Baltimore POTW were reported for each day starting
at 12 midnight on 10/11/76.
4.2 Analysis of Samples from the Bloomington POIW
After concentration of the organic extract to 10 ml, one yl was
injected into a Hewlett Packard Model 5710A gas chronatograph, with a column
of 1.5 per cent CV-17 plus 1.95 per cent QF-1 100/120 GCQ, operated at a
temperature of 210°C.
A quantitative calibration curve was obtained by injecting 1, 5, and
10 ng of Aroclor 1016 and measuring selected peak areas. Upon comparison of
sample chromatograms with calibration chromatograms of Aroclor 1016, an un-
ambiguous identification was made that the PCBs in the sample were, in fact, the
same isomers, in appropriate proportions, as those in Aroclor 1016. Figure 3
shows an Aroclor 1016 calibration chromatogram and a typical sample chromatogram;
Bloomington samples showed the characteristic peaks of Aroclor 1016. In
addition, the grab sediment samples from the Bloomington polishing lagoon
(BL-10 through BL-15) showed qualitative evidence of Aroclor 1232 in minor
amounts.
Since the wastewater samples from Bloomington yielded chromatograms
that were virtually identical to those of Aroclor 1016 standards, the total
PCBs in the samples were calculated as Aroclor 1016, by calibration with known
quantities of Aroclor 1016 standards.
Five of the composited samples were re-analyzed after passage through
a florisil clean-up column. The peak areas of the original and the cleaned-
up sets only differed by an average of 20 per cent, with no observable bias.
This 20 per cent difference is roughly the same as the two-sigrna confidence
interval obtained in serial replicates of standards:
-36-
-------
Standard
10 ng Aroclor 1016
9/23/76 Composite Sample BL-1,
Bloomington,POIW Influent
Figure 3
Chroratograins of Standard and of Typical Bloomington Sample
-37-
-------
Aroclor 1016
Standard, ng
1
5
10
Concentration in
Calibration Std, ppb
20
100
200
2a Confidence
Interval, Per Cent
± 18
± 25
± 18
Since there was no apparent interference with the analysis for
Aroclor 1016 PCB isoners, the potential for analytically-significant losses
during florisil cleanup was avoided. All Bloondngton samples were therefore
analyzed using single extraction and concentration.
Experience in PCB analysis at the Versar laboratory predicts a
recovery of PCB from the samples to be in excess of 72 per cent of the amount
present. The data reported is the amount extracted with no correction applied
for recovery efficiency.
4.3 Analysis of Samples from the Baltimore POIW
The extraction, concentration, and gas chromatograph procedures for
the Baltimore POIW samples were essentially the same as those for the Bloonington
POTW samples. A major difference existed, however, in the identification and
quantification of the PCBs in the Baltimore samples: there was no standard of
a conmercial PCB mixture which yielded a chromatogram directly comparable to
a sample chromatogram. The Baltimore chromatograms displayed a mixture of PCB
isomers, unlike the "fingerprint" of individual commercial mixtures such as
Aroclors 1016, 1232, 1242, 1248, 1254, or 1260. Figure 4 is a typical chroma-
togram of a Baltimore POIW sample. In this case, mono-, di-, tri-, and other
chloro isomer peaks were identified by their relative retention times (RRT) on
chromatographic columns in comparison with -standard PCB isomers (not commercial
mixtures) obtained from Mansanto. Remaining peaks on the sample chromatograms,
not matching the peaks of the standard pure isomers available for comparison,
were then matched with the peaks from standard commercial mixtures (Aroclors
1016, 1232, 1242, 1248, and 1254).
-38-
-------
- PC3 Peak Nb. 1
Figure 4 - Ghranatcgram of Typical
Baltimore PCIW Sample
(BA-1, 10/20/76)
-39-
-------
Careful scrutiny of all peaks on the sample chronatograms allowed a
number to be eliminated from consideration as PCS peaks, since the sams peaks
appeared in blanks and were ascribed to solvent constituents. Aroclor 1232
was eliminated because of its very minor past and present use and unlikelihood
of its significant appearance in the Baltimore wastewater.
Standards and selected Baltimore samples were also subjected to mass
spectronetric analysis at the Naval Research laboratory Finnigan Model 3000
spectrometer. The hexane extracts of Baltimore POIW samples verified the pre-
sence of rtono-chloro, di-chloro, tri-chloro, tetra-chloro, and penta-chloro
biphenyls, and some indication of higher mass clusters. Only two unknown
clusters with masses of 231 and 282 were observed. This indicates a significant
lack of potential interference from unknown species in the gas chromatographic
analysis.
Two peaks on the sample chromatograms were selected as representing
PCBs. These peaks, identified on Figure 4, had retention times of 153 to 160
seconds (Peak No. 1), and of 254 to 261 seconds (Peak No. 2), relative to an
Aldrin. retention time of 175 seconds under the same conditions.
Peak No. 1 in the Baltimore sanple chromatograms corresponds in
retention time with the major peak in chromatograms of both Aroclors 1242 and
1016. In the Aroclor 1242 standard, the area under this peak represents 48
per cent of the total area under all peaks; in Aroclor 1016, 33 percent. This
peak also is fairly representative in terns of retention time (a qualitative
measure of the number of chlorines in the PCS isoners} - about one-third of the
other peaks in the Aroclor 1242 standard have lower retention times, and about
one-half in the Aroclor 1016 standard.
Peak No. 2 in the Baltimore sanple chromatograms corresponds in
retention time with the next-largest peak in the Aroclor 1242 standard (it
accounts for 16 percent of all the area in the standard chraratogram). Peak
No. 2 is also present in the Aroclor 1016 chromatogram, but to a smaller degree.
About one-third of the other peaks in the Aroclor 1242 standard have greater
retention times than Peak No. 2; this peak is the last significant peak in the
Aroclor 1016 standard chromatogram.
-40-
-------
Together, Peaks No. 1 and No. 2 account for 64 percent of the total
area under the Aroclor 1242 standard, and cover both lower - and higher -
chlorinated isomers. The sum of the areas of these two selected peaks was
therefore used for calculation of PCBs concentration in the Baltimore POTW
samples, and the concentrations are reported as Aroclor 1242 concentrations.
Of the 52 sairple chranatograms (including 10 replicates), three were
rejected because the retention times of the selected peaks fell outside the
ranges quoted previously. These were Station BA-3, Day 5; and Station BA-4,
Day 4 (both replicates).
The replicate results (after rejection of three analyses) are pre-
sented in Table 9. The pooled estimate of the standard deviation (with 9 degrees
of freedom) is 21.6 percent of the mean concentration. This is twice the
standard deviation (10 percent) obtained in measuring concentrations of standard
Aroclors in water.
-41-
-------
Table 9 - Precision of PCBs Measurements
Baltimore POTW
I
K)
I
Station
Day
Replicate A: PCBs, ug/1
Replicate B: PCBs, yg/1
Replicate C: PCBs, ug/1
Mean: PCBs, yg/1
Standard Deviation, yg/1
Std. Dev. as Pet. of Mean
Degrees of Freedom
BA-1
1
13.45
11.14
11.40
12.00
1.26
10.6
2
BA-2
1
16.23
15.60
15.92
0.45
2.8
1
BA-2
2
14.20
17.12
15.66
2.07
13.2
1
BA-3
3
13.17
5.87
9.52
5.16
53.4
1
BA-5
5
1.96
1.93
1.83
1.91
0.07
3.6
2
BA-6
6
2.84
2.06
2.45
0.55
22.5
1
BA-6
7
3.16
2.36
2.76
0.57
20.5
1
Note: Replicate C is a repeat chromatogram of the same concentrate as Replicate A;
Replicate B is a chromatogram of a repeat extraction and concentration as
Replicate A.
-------
5.0 PCBS DATA AND ANALYSIS OF RESULTS
5.1 PCBs Concentration Data
Tables 10 and 11 (respectively) list the PCBs concentrations for the
Blooraington POTW and for the Baltimore POTW. The PCBs concentrations at Blocm-
ington are an order of magnitude higher than at Baltimore, the result of the
discharge of Aroclor 1016 by the Westinghouse capacitor plant to the Blocmington
sewer system.
5.1.1 Analysis of Variance in Concentration Data
The mean concentration of PCBs at each station, and the day-
to-day standard deviation for each station, are presented in Tables 10 and 11.
At this stage, one additional data point was rejected - the result for Baltimore
POTW Station BA-4 on Day 3, which was 18.7 yg/1 PCBs. With this data point
included, the standard deviation about the mean for Day 3 was 4.66 yg/1; without
this data point, the standard deviation was 2.08 yg/1. The value of the F
statistic of (4.66/2.08)2 = 5.03, with 5 and 4 degrees of freedom for numerator
and denominator respectively, is significant at the 90 percent confidence level,
justifying rejection of this data point.
It is apparent from Tables 10 and 11 that much greater day-to-
day variability occurred at Blcomington than at Baltimore. The pooled estimate
of standard deviation for all stations at the Blocmington POTW was 42 percent
of the respective mean, while it was 20 percent at the Baltimore POTW. The much
higher day-to-day variability in the data of the Blocmington POTW is explained
by the high dependence of the influent PCBs concentration upon a single indus-
trial discharge, which indeed does vary widely in time (as demonstrated by the
discharge data in Section 2.3.1). Conversely, the sources of PCSs to the
Baltimore POTW are much more diffuse, and the plant influent PCBs concentrations
do not vary significantly from day-to-day.
The high day-to-day variability in the Blocmington POTW primary
influent PCBs concentration (S = 59 percent of the mean) is reflected in the
high variability in the PCBs concentrations in the North and South primary
-43-
-------
Table 10 - PC3s Concentrations, jjg/1 as Aroclor 1016
Bloomrngton POIW
i
i
Station
Day 1
Day 2
Day 3
Day 4
Day 5
Day 6
Day 7
Day 8
Day 9
Day 10
Mean
S, Std. Dev.
S/Mean, %
BL-1
Primary
Influent
222
236
124
216
84
280
50
54
110
72
145
85
59
BL-2
North
Primary
Effluent
68
100
64
74
38
56
38
46
42
34
56
21
37
BL-3
South
Primary
Effluent
108
62
56
84
68
42
38
46
24
28
56
26
46
BL-2, BL-3
Average
Primary
Effluent
88
81
60
79
53
49
38
46
33
31
56
21
37
BL-4
Secondary
Clarifier
Effluent
26
26
22
28
34
36
24
20
22
20
26
6
21
BL-5
Final
Lagoon
Effluent
11
22
28
18
30
14
12
10
14
16
18
7
39
-------
Table 11
PCBs Concentrations, |ig/l as Aroclor 1242
Baltimore
Station
Day I
Day 2
Day 3
I>ay 4
Day 5
Day 6
Day 7
Mc'an
S, Std. Dev.
S/fean, %
BA-1
Plant
Influent
12.0
14,8
"11,2
15.9
17.1
18.0
13.7
15.1
2.1
14
UA-2
Primary
Inf luant
15.9
15.7
16.7
18.8
16.5
19.2
11.9
16.4
2.4
15
HA-3
Trickling
Filter
Inflmxit
5.6
9.3
9.5
11.4
11.7
5.6
8.9
2.7
JO
FlA-4
Activated
Sludge
JnOuent
7.2
11.9
6.6
9.0
7.1
8.4
2.1
22
BA-3, HA-4
Avg. Influent
to Secondary
Vtcxxjsses
6.4
10.6
9.5
11.4
6.G
10.4
6.4
8.8
2.2
25
I1A-5
r~~
ActiveJtad
Sludge
F.fOirat
i . 7'3
1.34
0.99
1.93
1.91
1.85
1.59
1.63
0.35
22
BA-6
Ilisnu'J
Tank
Effluent
2.95
1.98
i. 37
2.39
2.81
2.45
2.76
2.53
0.33
13
-------
effluents (S = 37 and 46 percent, respectively) , although sate damping my have
occurred. The standard deviation about the mean for the Bloomington secondary
clarifier effluent PCBs concentration is only 21 percent, indicating that the
trickling filter and secondary clarifiers provide sufficient capacitance for
PCBs so that wide day-to-day swings in the PCBs concentration influent to this
secondary treatment process are considerably damped. The PCBs concentration in
the final, lagoon effluent varies much more widely, with a standard deviation of
39 percent of the mean. Since the lagoon detention time is so large, 7.5 days,
it would be expected that day-to-day swings in the lagoon influent concentration
(the primary effluent bypassed around the trickling filter as well as the secondary
clarifier- overflow) would be completely damped. The wide day-to-day variability
of the lagoon effluent concentrations are probably attributable to day-to-day
differences in wind-induced turbulence in the shallow lagoon which cause resus-
pension of PCB-laden fine solids.
The mean PCBs concentrations for the North and South primary
effluents at the Bloomington PCTW were the same - 56 vgA- Although the over-
flow rate in the North bank of primary clarif iers was considerably higher, the
overflow rates of both banks were well within the guidelines for good primary
clarification (no independent measures of suspended solids removal are available).
It is therefore assumed that both banks of clarif iers did indeed have equivalent
PCBs effluent concentrations, and the daily averages are listed in Table 10.
The day-to-day differenoes betaken BL-2 and BL-3 therefore provide a direct
measure of the total uncertainty in sampling, compositing, extracting, concen-
tration, and chronatographic analysis:
Day
Std. Dev. , ug/1
Std. Dev., % of Mean
1
28
32
2
27
33
3
6
9
4
7
9
5
21
40
6
10
20
7
0
0
8
0
0
9
13
39
10
4
14
The pooled estimate of the standard deviation is 24.5 percent
of the mean concentration. This represents the total imprecision in each PCBs
concentration data point at Bloomington.
-46-
-------
Similar ily, it may be assumed that the PCBs concentrations are
equivalent for the Baltimore POTW stations BA-3 and BA-4 (the trickling filter
influent and the activated sludge influent, respectively). Both stations are in
the same wastewater channel, and the mean PCBs concentrations are very close:
8.9 and 8.4 yg/1. Moreover, the data of Table 7 show that the mean concentra-
tions of suspended solids at the two stations (134 and 116 mg/1) and of BODs at
the two stations (151 and 151 mg/1) are also close. Table 11 lists the average
PCBs concentrations for these two stations. The day-to-day differences between
BA-3 and BA-4 provide a direct measure of the total uncertainty in sampling,
compositing, extraction, concentration, and chromatographic analysis:
Day
Std. Dev. , yg/1
Std. Dev. , % of Mean
1
1.1
18
2
1.8
17
6
1.9
18
7
1.1
17
The pooled estimate of the standard deviation is 17.5 percent
of the mean concentration. This represents the total imprecision in each PCBs
concentration data point at Baltimore. Pooling this value (with 4 degrees of
freedom) with the Bloomington value of 24.5 percent (with 10 degrees of freedom)
yields an overall imprecision in each PCBs concentration data point, for both
POTWs, of 22.7 percent of the concentration. This value is essentially the
same as the standard deviation, 21.6 percent, of replicate extraction, concen-
tration, and chromatographic analysis (as derived in Section 4.3). Hence, the
sampling and 24-hour compositing procedures followed at these two POTWs did not
appreciably add to the measurement uncertainties introduced by the laboratory
procedures.
When the pooled standard deviation of measurement, 22.7 percent,
is compared with the day-to-day standard deviations at each station in Table 11,
it is apparent that the PCBs concentrations at the Baltimore POIW did not vary
significantly from day to day. The same comparison made with the day-to-day
standard deviations at each station in Table 10, however, indicate that only the
-47-
-------
secondary clarifier effluent (Station BL-4) remained relatively the same; and
that the PCBs concentrations at the other Bloonington POIW stations did vary
significantly frcm day to day.
5.1.2 Uncertainty in Derived PCBs Removal Efficiencies
The PCBs removal efficiency for any treatment process (or for
any series combination of processes) is defined as n = 100(1 - CL./CT) ,
where: n = PCBs removal efficiency, percent
C_ = PCBs concentration in effluent
Cj = PCBs concentration in influent.
Based upon error theory,
Where ACj. and ACg are (respectively) the measurement errors in PCBs concentration
in the influent and effluent, and where An is the resultant error in the calcu-
lated ranoval efficiency.
If the percent errors are the sane for CU and C , e.g. , if ACU/CL = AC_/C_ =
«£* -L & ~j J. X
AC/C, the error in the calculated removal efficiency is
An = ioOvT"(AC/o (loo - n) .
Since AC/C = 0.227,
An - 0.321 (100 - n).
The uncertainty in the PCBs removal efficiency thus depends
not only upon the uncertainty in PCBs concentrations, but upon the value of
removal efficiency itself:
n, %
sn = An, %
10
29
25
24
50
16
75
8
90
3
95
2
The higher the efficiency, therefore, the better known it is.
-48-
-------
Sn, the standard deviations for the removal efficiency (listed above)
apply to daily values, since they are based upon the uncertainty in daily
PCBs concentration values. Sn is a treasure of the uncertainty in each daily
removal efficiency value. When, as in this study, several days'data are ob-
tained so that several values of the removal efficiency n exist, the average
removal efficiency is more precisely known than is each daily value. The
standard error of the mean PCBs removal efficiency (Sri) over N days is:
0-321
/N (10°-^
5.2 Overall PCBs Removal Efficiencies
The overall PCBs removal efficiencies for each of the two POTWs is
derived from the mean PCBs concentrations at the plant influent and effluent.
The values, along with ± 2S- confidence limits, are listed in Table 12. Also
in Table 12 are the corresponding removal efficiencies achieved for suspended
solids and for BCD (from the data of Tables 3 and 7). The PCBs removal
efficiencies are comparable to, but slightly less than, the corresponding
removal efficiencies for suspended solids and for BOD. There is very little
doubt, based upon these overall plant data, that POTWs do in fact effectively
remove PCBs from wastewaters.
5.3 PCBs Removal in Primary Sedimentation
5.3.1 The Bloomington POIW Primary System
Table 13 lists the daily PCBs removal efficiencies in the
Bloomington POIW primary system, derived from the concentration data of Table
10. The mean removal efficiency is 53 percent. Listed next in Table 13 are
the daily values of the influent PCBs concentration from Table 10; and a
normalized version of this concentration about the mean influent concentration
of 145 yg/1- Figure 5 shows that the PCBs removal efficiency depends upon
the influent PCBs concentration - the higher the influent concentration, the
higher the efficiency. The straight line of Figure 5 has the equation
n = 48.5 + 33 (C-145)/145.
-49-
-------
Table 12 - Overall Removal Efficiencies
POIW
Bloomington
Bloonington
Baltinore
Baltimore
Treatment
Systems
All, Including
Final Lagoon
Primary and
Secondary
Primary and
Activated Sludge
Primary and
Trickling Filter
PCBs Removal
Efficiency,
Percent
88 ± 22
82 ± 4
89 ± 3
83 ± 4
Suspended Solids
Removal Efficiency,
Percent
95
86
95
84
BOD
Removal Efficiency,
Percent
91
81
92
87
-------
T.llilo 13
I
Ul
rrjg^ai*,
r, litf luonL mia, |i/24'J
An'
il" mis, t
HiKXMxluiy Syutonu
nit:na, %
C, Influent. Kilo, inj/1
(056)/56
Ail
II* 1X113, %
1
60
222
10.53
-11
41
240
0.04
I
40
70
UU
10.57
-22
41)
2
66
2)4
I0.fi)
-21
45
240
0.04
-)
42
60
Ul
10.45
17
51
J
52
124
0.14
t5
5/
il)
I0.2C
I If)
75
63
00
10.07
-3
60
4
61
216
(0.49
If,
4/
2 SO
0.00
0
47
65
79
10.41
-16
49
5
37
(14
-0.42
1)4
51
220
0.12
-II
43
)6
53
-0.05
12
30
6
03
2UO
-0.91
-5!
:»2
J0r>
(0.22
115
f.7
27
4'J
-O.I 3
15
12
7
24
50
-0.60
122
46
720
-0.!2
-0
HI
!/
it)
-0.32
1 12
4')
0
15
54
-0.63
121
36
130
10. 13
122
5U
5/
46
-0.10
17
64
9
VO
110
-0.24
IB
7(3
173
-0. 31
-21
57
33
31
-0.41
16
49
10
57
72
-0.50
I If,
73
20)
-0.10
-12
61
35
31
-0.45
17
52
IVan
53
145
0.00
0
53
249
0.00
0
53
49
56
0.00
0
49
-------
-2S-
-,, ?C3E removal Efficiency, Percent
O
a
2 S
I
3
2
r;
o
o
o
N
O
i»
£
f?
4?
B
»-
-------
An explanation for this dependence is the PCBs damping capacity
of the primary clarifiers - in the clarified water, in the settled sludge, and
upon the structural surfaces of the clarifiers. Thus, a temporary higher-than-
average PCBs concentration in the influent would not immediately and proportion-
ately be observed in the effluent, resulting in a temporary higher apparent PCBs
removal efficiency.
This damping phenomenon is demonstrated by the day-to-day con-
centration variations in Table 10. Although the standard deviation for the
primary influent is 59 percent, the standard deviation for the average primary
effluent is only 37 percent.
The next line in Table 13 is a correction to each daily PCBs
removal efficiency, to normalize the efficiency to an average influent PCBs
concentration of 145 yg/1. This correction is An = - 33 (C-145)/145. Next,
in Table 13 is the normalized efficiency, n' = n + An.
A similar exercise is next performed, using the influent BOD
concentration from Table 3 as the independent variable. Figure 6 shows that ^
n1, the PCBs removal efficiency (already normalized for its dependence upon the
influent PCBs concentration), is dependent upon the influent BOD5 concentration.
The equation of the straight line in Figure 6 is
n1 = 59.0 - 68 (B-249)/249.
One explanation of this dependence is that the higher the BOD concentration,
the more soluble the PCBs may be in the water phase, thereby inhibiting the
direct removal of PCBs with solids via the primary clarification process.
-53-
-------
I0°
1
-^
H
II
?.!
h 60
pi
N 4O
O
Fiijuru 6
IV 'Us Idmuval !;! i
\
lilrxl
^\
\
it:ieiicy vs.
lill>ltOll IHTIW
O
0
0 8'
ItiflitenL Ht») OMUxiiiLraLion
I't iiiury liyut
eiu
O
0
\
X
\
O8 -06 -04 -Oa OU 102 104 t06 + O8 410
H Mnul tzcjl Inilik.'nL IKJI) tliiicorjtraLioii. (JJ-24'J)/li49
D
-------
The correction (for influent BOD concentration) is made to
each daily PCBs removal efficiency by An1 = + 68 (B - 249)/249; and then the
normlized efficiency is calculated by.n" = n' + An,1. The mean for the normal-
ized PCBs removal efficiency is not changed by this stepwise multiple regression
process. A predictive equation for the daily PCBs removal efficiency at the
Bloonington POTW primary -system is:
- 53 + 33 - S3
The day-to-day standard deviation of rip , the raw PCBs
removal efficiency, is 21.3 percent (with 9 degrees of freedon) . The day- to-
day standard deviation of nMpCBs/ the PCBs removal efficiency normalized for
the daily variations in the primary influent PCBs and BCD concentrations , is
14.3 percent (with 7 degres of freedom) . The predicted standard deviation in
the PCEs removal efficiency (from Section 5.1.2) at n = 53 percent is 15.1 per-
cent. Hence, the residual variance in the daily values of n" is attribut-
able to the uncertainties in the measured PCBs concentrations.
For the 10-day average PCBs removal efficiency, the standard
error of the mean is 14.3//~IcT =4.5 percent. The two-sigma confidence
interval around the normalized PCBs removal efficiency for the Blocmington POIW
primary system is therefore 53 ± 9 per cent.
5.3.2 The Baltimore PCTW Primary System
Since the day-to-day variations in the PCBs concentrations
are attributable to the measurement uncertainties, the mean concentrations will
be used to derive a PCBs removal efficiency. This efficiency is 100(1 - S.3/
16.4) or 46 percent. The predicted standard deviation (from Section 5.1.2) at
H = 46 percent is 17.2 percent, and the standard error of the 7-day mean is
17,2//~T= 6.5 percent. The two-sigma confidence interval is therefore 46 ± 13
percent for the Baltimore POTW primary system PCBs removal efficiency.
-55-
-------
5.4 PCBs Removal in Seconda.ry Treatment
5.4.1 The Bloomington POTW Trickling Filter System
Table 13 lists the daily PCBs removal efficiencies for the
Bloomington POTW trickling filter system, derived from the concentration data
of Table 10. The mean removal efficiency is 49 percent. In a similar fashion
to the regression analysis in Section 5.3.1, Table 13 also lists the PCBs con-
centrations influent to the secondary system, and their normalized versions.
Figure 7 shows the strong dependence:
n = 49 + 38 (C - 56)/56,
which, is explained by the same damping capacity arguments made for the primary
system. As Table 10 indicates, the day-to-day standard deviation in the
secondary effluent is 21 percent, damped from the 37 percent for the secondary
influent.
The correction is An = - 38 (C-56)/56, and Table 13 lists
daily values of the normalized efficiency, n" = n + An.
The day-to-day standard deviation of n^r-n^' the raw removal
rV-tiS
efficiency, is 16.9 percent (with 9 degrees of freedom) . The comparable number
for n 'TV-IDS/ the removal efficiency normalized for the daily variations in the
secondary influent PCS concentration, is 9.8 percent (with 8 degrees of freedom)
The predicted standard deviation in the PCBs removal efficiency (from Section
5.1.2) at n = 49 percent is 16.3 percent. The residual variance in the daily
values of n '.-« is attributable to the measurement uncertainties.
The standard error of the 10-day mean is 9.8/ /10 = 3.1
percent, and the two-sigma confidence interval around the normalized PCBs
removal efficiency for the Bloomington POTW secondary system is therefore
49 ± 6 percent.
5.4.2 The Baltimore POTW Secondary Systems
The PCB removal efficiencies (based upon the mean concentra-
tions of Table 11) and the associated reliability estimates, are as follows:
-56-
-------
too
41
1 "
1
H 60
11
?C3s Renewal
*
o
r~
20
0
1 1 1 1 1
Figure 7
rujs Itoiuvul lafiuiunuy va. Intlueiit IXJUa Conuentration
O
Illurin
^"
nylon Trick
0
^
O
0
limj Kiltur i
O
^^
^
jyatuni
^-^
^^
^^
08 "°* -°« -o* oo toz +04 toe foe 410
Normalized Intluont WTlia Concentration, (C-56)/b6
-------
Activated Sludge
System.
Trickling Filter
System
PCBs Removal Efficiency, %
Predicted Std Deviation, %
Std Error of the Mean, %
2a Confidence Interval, %
81.5
6.0
2.2
±4.5
71.2
9.2
3.5
±7.0
5.5 PCBs Removal in the Bloonington Final Lagoon
The day-to-day standard deviation of the final lagoon effluents
(Table 10) is 39 percent, indicating that measurement uncertainties do not
account for all of this variability. However, the detention time in the lagoon
is too large for any effects of the lagoon influent variability (or of bypassed
flows) to be seen at the effluent. The effects of wind or other factors are
more likely to be important.
Based upon the mean PCBs concentrations of Table 10, the PCBs removal
efficiency for the final lagoon is 31 percent. The efficiencies calculated
from daily concentrations have a standard deviation about this mean of 22 percent.
The standard error of the 10 - day mean is 22/ /lb~ =7.0 percent, and the two -
sigma confidence interval around the mean removal efficiency is 31 - 14 percent.
5.6 Correlation of Unit Process PCBs Removal Efficiencies
A summary of the PCBs removal efficiencies for the unit processes
is as follows:
Bloomington Primary System
Bloomington Trickling Filter
Bloomington Final Lagoon
Baltimore Primary System
Baltimore Activated Sludge
Baltimore Trickling Filter
nPCBs, %
53 ± 9
49+6
31 + 14
46 ± 13
81.5 ± 4.5
71.2 ± 7.0
nss, %
64
61
62
29
93
77
-58-
-------
Also listed above are the corresponding suspended solids renewal efficiencies.
The PCBs removal efficiency is plotted against the suspended solids removal
efficiency in Figure 8. Points for four of the six unit processes fall very
close to the straight line:
nPCBs
= 53.5 + 75
"ss"65
55
According to this line, npCBs is somewhat lower than nsg. This result is the
expected one, since it is well known from prior studies (e.g., of pulp and
paper wastewater treatment) that PCBs are adsorbed onto suspended solids. If
the PCBs were uniformly distributed on the solids, then the model for PCBs
removal would predict that the partition of PCBs between overflow and under-
flow in each solids-separation process (including the secondary clarifiers)
would identically follow the solids partition; e.g., that rL^ = nss. In
practice, more PCBs become adsorbed onto the finer solids, which are more
difficult to remove, so that Hp^*. nss- However, the only way for npCBs to
be greater than nss is for another removal mechanism to be effective. In the
case of the Baltimore POTW primary system, where npc^s = 46 percent and nss = 29
percent, the only feasible alternate mechanism for PCBs removal is scum
removal. Unfortunately, data are not available either for the PCBs concentration
in the primary scum nor of the scum flow. The only related data are the follow-
ing measurements of fats, oils, and greases (FOG):
Date
10/14/76
10/17/76
10/18/76
FOG, mg/1
Plant Influent
76.0
39.1
22.2
Primary Effluent
56.0
14.5
11.2
FOG Ranoved,
Ibs/day
33,600
38,300
17,800
Based upon these data, an average of 30,000 pounds per day of FOG are
removed in the primary system. Some of this FOG would be adsorbed onto solids,
and some would be in the primary scum,
-59-
-------
-09-
, ?C2s Sanoval Sfficienry, Percent
cccocoocS
o
1
i
1
n l
< i
;, |
2 I
s '
e |
* i
^5 rl ^ r
s * - 2 ^
1 o "»
-------
The other data point on Figure 8 not falling close to the correlation
line is that for the Blocmington POTW final lagoon. The evidence that rw,^ <
ng may be explained by a resuspension of PCB-laden fine solids via wind-
induced turbulence, resulting in a lower apparent Hp. The smallest particles,
which would likely remain resuspended, would have a relatively large quantity
of PCBs adsorbed because of the high specific surface area. Ifowever, these
smallest particles would not as strongly affect the solids removal efficiency,
which is on a weight basis rather than a surface area basis.
Moreover, much of the PCBs in the lagoon sediment, which may be re-
suspended, reflects prior years of operation, when the waste load of PCBs to
the POTW was higher, and when this waste load consisted of PCBs other than
Aroclor 1016. Evidence of higher-chlorinated PCB isomers was fo -ri in the
ciiromatograms for the lagoon sediment analyses.
With the above explanations, then, for the two unit processes not
following the general correlation, the conclusion reached for the other four
unit processes is that the removal of PCBs does closely follow the rotoval of
suspended solids. It should be remembered, however, that day-to-day effects
are also important - specifically the influent PCBs concentrations for both
primary and secondary systems, and the influent BOD concentration for primary
systems.
-61-
-------
6.0 PCBs MATERIAL BALANCES
6.1 The Blocmington POTW
Since the sludge from, the secondary clarifiers at the Blocmington
PGTW is returned to the head of the plant/ the PCBs and the suspended solids
that are removed from the wastewaters most be in either the primary sludge
(Sampling Station BL-7) or in the lagoon sediment (Sampling Stations BL-10
through BL-15). The predicted ratio of PCBs to dry solids in these two
locations may be derived by difference, from the average wastewater data of
Babies 3 and 10:
PCBs in Influent, yg/1
PCBs in Effluent, yg/1
PCBs Removed, yg/1
SS in Influent, mg/1
SS in Effluent, mg/1
SS Removed, .mg/1
PCBs Removed _ wciqht
SS Removed ' ^ ary wu*rc
Primary Sludge
145
56
89
283
102
181
492
Lagoon Sediment
26
18
8
40
15
25
320
Two grab samples of raw primary sludge (Station BL-7) were taken, one
on September 20, 1976, and the other on September 30, 1976. The results of the
sludge analyses, in ppm PCBs (dry weight) were, respectively, 409 and 361. The
experimental average of 385 ppm is 22 percent'less than the predicted value of
492 ppm. The difference is of the same size as the measurement errors involved.
Alternately, some of the PCBs removed in the primary system at the Bloomington
POTW may have been in the removed sctsn rather than in the removed solids.
Six grab samples of lagoon sediment were taken on^September 20, 1976,
at different locations in the pond. The results of the sediment analyses, in
ppm PCBs (dry waight) were:
-62-
-------
BL-10
BL-11
BL-12
BJ>13
BI/-14
BL-15
5,340
1,410
2,300
1,360
1,440
2,680
The measurement average of 2,420 ppm is more than 7 times the predicted value
of 320 ppm. One possible explanation of this discrepancy is that frequent by-
passes of the secondary treatment system occur at Bloonington, resulting in
primary effluent being pumped to the lagoon along with secondary effluent.
Again using wastewater values fron Tables 3 and 10, the predicted PCBs content
of the lagoon sediment from bypassed flow is:
SS in lagoon influent
SS in lagoon effluent
SS removed in lagoon
PCBs in lagoon influent
PCBs in lagoon effluent
PCBs removed in lagoon
PCBs Removed
SS Removed
102 mg/1
15 mg/1
87 mg/1
56 yg/1
18 yg/1
38 yg/1
437 ppm dry weight
This predicted ratio of PCBs to suspended solids is also much lower than the
experimental ratio for the lagoon sediment. Hence, the frequent bypass of the
secondary treatment system cannot be responsible for this discrepancy.
A probable explanation for this discrepancy is the reasoning given
in Section 5.6 - that the PCBs in the lagoon sediment are "old" PCBs reflecting
prior years of POTW operation rather than current operation. A PCBs material
balance around the lagoon is therefore complicated by the differences in PCB
loadings of present-day influent and effluent vs. prior-day sediments.
An additional explanation is that the sediment solids degrade into
gaseous and other end products over extended periods of time. As the quantity of
solids decrease,.with time, the ratio of PCBs to solids in the sediments increases,
-63-
-------
Three additional grab samples were obtained at Bloonington. These
were of primary sludge at several stages of digestion:
Sludge front First Digester in Series 735 ppm PCBs (dry wt.)
Sludge from Second Digester in Series 891 ppm PCBs (dry wt.)
Sludge from Final Digester in Series (BL-8) 674 ppm PCBs (dry wt.)
The average of 767 ppm PCBs (dry weight) in the digested sludge is twice the
value obtained for raw sludge upstream, of the digester (385 ppm). Two possible
explanations are that:
1. The suspended solids content is reduced (by a typical 30 percent)
via digestion of the volatile solids, thereby significantly increasing
the PCBs content in the remaining digested sludge solids; and that
2. The higher PCS content of digested sludge may reflect a higher PCB
content in older raw primary sludge (fed to the digester prior to
the ten-day survey period). The residence time in these digesters
may be in the order of 60 days.
Although plans were made for the digester gas to be sampled for PCBs
(Station 9 in Figure 1) / this sampling was not performed at the Bloomington
POTW.
It is concluded that reasonable PCBs materials balances were obtained
for the Bloomington POIW primary system and primary sludge processing.
6.2 The Baltimore POTW
6.2.1 Measurement of PCBs in Sludges
Single grab samples of sludges, collected at the Baltimore
POIW, resulted in the following experimental data:
Solids Ccntanc of Sludge, Percar.t
?C3s, ug/1 in vet sludge
PC3s, ?cm dry weigirt of solids
Sludge Flew, sigd
PCSs in Sludge, Ibs/day
Point 3
Eiunsjs Tank
Sludge
3.24
32
13
0.393
0.24
Point 9
Act. Sluice
(Settled Sluice)
O.S9
46
~
112.74 (total)
! 3.344 (vasts)
14.89 (total;
' 0.36 (vassal
Point 11
Thidcer.ad
SiJdge
4.39
630
16
3.57
3.23
Point 12
2igestac
Sludge
3.26
315
25
0.52
4.21
-64-
-------
6.2.2 Primary System
The average quantity of PCBs in the digester influent and
effluent is 3.7 pounds per day. A PCBs balance around the sludge thickeners
(just upstream of the digesters, see Figure 2 and Table 6) may be agtinHteari
to derive the PCBs in the primary sludge:
Effluent from Thickeners:
Thickened Sludge
Thickener Overflow
Influent to Thickeners:
Dilution Water
Waste Activated Sludge
Primary Sludge
Flow, mgd
0.60
14.64
12.19
0.84
2.09
PCBs, vg/l
750
~ 8
~ 3
46
230
PCBs, Ibs/day
3.7
1.0
0.3
0.4
4.0
In comparison, the PCBs quantity removed from the 198.6 mgd
of primary wastewater, at a concentration difference of 16.4 - 8.8 = 7.6 yg/1,
vjould be 12.6 pounds per day, or three times the quantity estimated to be in
the primary sludge. This finding is independently and qualitatively substanti-
ated by the comparison of PCBs removal efficiency, 46 percent, with the sus-
pended solids removal efficiency, 29 percent, which indicates an alternate
mechanism (like scum removal) for removing PCBs in the primary system at the
Baltimore POTW.
As shown previously, the PCBs/solids ratio measured for digested
sludge (sampling station 12 in Figure 2) was higher than for the thickened sludge
feed to the digester (sampling station 11). These results are consistent with a
loss of solids in the digestion process, which typically is about 30 percent. A
digester gas sample was collected (at point 13 in Figure 2), and subsequent anal-
ysis revealed no measurable PCBs in the digester gas.
-65-
-------
6.2.3 Secondary Systems
In the secondary treatment processes at the Baltimore POTW,
the following quantities of PCBs were removed from the wastewaters:
Activated Sludge System
Trickling Filter System
Flow,
mgd
42.8
135.7
PCBs Removed,
yg/i
7.2
6.3
PCBs Pemoved,
Ibs/day
2.6
7.1
The comparable values derived from PCBs measurements of the secondary sludges
were 0.36 pounds per day in the waste activated sludge and 0.24 pounds per
day in the humus tank (trickling filter) sludge.
TWo potential mechanisms for explaining the unaccounted-for
PCBs in the secondary treatment systems at the Baltimore POTW are biodegradation
and volatilization.
A pilot study of the activated sludge process was conducted
by Tucker, Saeger, and Hicks, using several Aroclars^ . Both biodegradation
and volatilization rates were reported. The biodegradation rates were as follows:
PC3 Mixture
Aroclor 1221
MCS 1043
Aroclor 1016
Aroclor 1242
Aroclor 1254
a,
%
21
30
41
42
54
Initial Cone,
ug/l
667
667
667
667
667
48-hr Degradation,
%
81 ± 6
56 ± 16
33 ± 14
26 ± 16
15 ± 38
Degradation Rate,
ugA/hr
11.3 ± 0.8
7.8 ± 2.2
4.6 ± 1.9
3.6 ± 2.2
2.1 ± 5.3
The detention time of the wastewater in the aerators of the
Baltimore POIW activated sludge units is 3.4 to 6.1 hours. At the Aroclor
1242 and 1254 degradation rates from the above pilot study, a PCBs concentration
reduction of 7 to 22 ug/l might be expected. This is sufficient to account for
all of the PCBs concentration reduction actually achieved across the activated
sludge units, from 8.5 to 1.6 ug/l.
-66-
-------
In. this Tucker study, the 48-hour disappearance of PCBs, due
to volatility, was 3.6 to 6.1 percent of the initial quantity, which was 667
yg/liter. This vaporization rate was therefore 0.50 to 0.85 yg per hour per
liter. Another batch activated sludge study, conducted by Kaneko, Morirnoto, and
Narabu, resulted in a vaporization rate of 3 percent per hour: 15 percent of the
PCBs vaporized in 3 hours and 65 percent in 20 hours. ^ In this study the initial
PCBs concentration was 10 ygA/ so that the vaporization loss was about 0.3 yg per
hour per liter.
A mass balance model for PCBs in Lake Michigan resulted in the
observation that evaporation and/or codistillation was a significant process by
which PCBs are transferred to the atmosphere from aqueous solution. The
evaporation rate constant for Aroclor 1254 in aqueous solution at ambient temper-
ature (298°K)f where the vapor pressure of Aroclor 1254 is 7.7 x 10"s mm Hg, was
evaluated both from kinetic theory and from empirical Lake Michigan data as
2.5 x 10~ia lbs/hr/ft2. Applying this rate constant to the Baltimore trickling
filter, with a surface area of about 220 x 106square feet, results in an evapora-
tion rate of 40 pounds per hour. Hence, the 7.1 pounds per day (0.3 pounds per
hour) of PCBs removed from the wastewater by the trickling filter process could
evaporate to the atmosphere. A very large air/water interfacial area is also
provided (by design) in the activated sludge units, for evaporation of PCBs to
take place.
At the Baltimore POTW activated sludge units, the detention time
of the wastewater in the aerators is 3.4 to 6.1 hours. At a vaporization rate of
0.5 yg per hour per liter (typical of the two pilot studies referenced above),
a reduction in PCBs concentration of 2' to 3 yg/1 might be expected. This is
less than the experinentally-determined PCBs concentration reduction across
the activated sludge units, from 8.8 to 1.6 yg/1; and is several times less
than the expected rate of PCBs biodegradation.
-67-
-------
7.0 EXPERIMENTAL STUDY CF PCBs VOLATILIZATTCN
The mechanisms of PCBs volatilization to the atmosphere, and of PCBs biodegra-
dation, are potential ways to explain the disappearance of PCBs in the secondary
treatment processes at the Baltimore POTW. It was important to explicitly deter-^
mine the quantity (if any) of PCBs vaporized, as this mechanism results- in direct
re-release of PCBs to the environment rather than capture, disposal, or destruc-
tion. A two-part experimental program was carried out - first in the laBoratory
in a bench-scale aeration unit, and then in situ at an aeration basin at the
Baltimore POTW.
7.1 Laboratory Experiments
The laboratory experiments were conducted with the same volume-
specific air rate as in the Baltimore PCTW aerators. At Baltimore, an average
of 86.05 million cubic feet per day (2.44 million cubic meters per day or 3.59
million cubic feet per hour) were supplied to the aerators, which have a total
volume of 1.38 million cubic feet. The volume-specific air rate used as a
scaling parameter was then 3.59/1.38 or 2.60 volumes of air per hour per volume
of mixed liquor.
The PCBs removed from the wastewaters at the Baltimore POTW .activated
sludge units were 7.2 Ibs/day, of which 6.8 Ibs/day (3,100 grams per day) were
not accounted for by the PCBs in the secondary wasted sludge. If all of the
missing PCBs had vaporized, the average PCBs concentration in the air would
have been 3,100/2.44 = 1,260 micrograms per cubic meter, or 1.26 micrograms per
liter of air.
Six laboratory experiments were conducted, with air (or nitrogen)
sparged through a test liquor. The incoming gas was first passed over activated
charcoal to ensure its purity. The exiting gas was passed through a train of
two 100 ml ethylene glycol inpingers for capture of PCBs. As a safety precaution,
the final waste gas was passed through another activated charcoal trap. Upon
completion of each experiment, the contents of the two impingers were combined
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(together with washings from the sampling train) and analyzed. The test liquor
for each experiment was also analyzed for PCBs after aeration. Initial PCBs
analyses (prior to aeration) were conducted for Runs B-l through B-4.
These samples were analyzed in a different manner from the previous
wastewater samples. One liter of the test liquor was extracted with 500 ml
petroleum ether rather than hexane-methylene chloride to remove the interfering
peaks found in the earlier reagent blanks. The samples were then concentrated,
placed on Florisil columns and eluted with 200 ml of 6 percent diethyl ether-
petroleum ether and concentrated to 10 ml in iso-octane for injection into the
electron capture gas chraiatograph. The combined ethylene glycol contents of
the two impingers were diluted with water, extracted with 50 ml petroleum ether
and concentrated for injection.
Chranatographic conditions were modified from those used for the
previous analysis of the water samples. The retention times were increased to
provide better separation for the more volatile peaks and the sensitivity
increased ten-fold.
The first series of laboratory runs, A-l and A-2, were conducted
using distilled water, spiked with 100 ug/1 of Aroclor 1242, as the test liquor.
For the other four experiments, B-l through B-4, the test liquor was a synthe-
sized mixed liquor made by adding return sludge to influent wastewater (e.g.,
primary effluent) in the 20.5/79.5 ratio which existed during the survey period
at the Baltimore POTW. The return sludge and the influent wastewater were
separately obtained from the Baltimore PCQW at Stations 9 and 4 respectively
(Figure 2). The return sludge was aerated at all times prior to the laboratory
experiments.
Experiment No. B-l was a direct simulation of the full-scale aeration
basins. For Experiment No. B-2, the synthesized mixed liquor was spiked with
an additional known quantity of Aroclor 1242 prior to aeration. Experiment B-3
and B-4 were similar (respectively) to Experiments B-l and B-2, except that two
steps were taken to prevent biodegradation as a competing mechanism (to vapor-
ization) for PCBs disappearance. First, nitrogen was used instead of air as
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sparging gas for Experiments B-3 and B-4. Second, the synthesized mixed liquors
for these two experiments were autoclaved at 250°F and 15 psig for 20 minutes
and cooled while sealed, prior to the evaporation experiments.
The conditions and results for the six experiments are in Table 14.
For Hun A-2 where distilled water, at 40°C, spiked with 100 yg/1 of Aroclor 1242
was the test liquor, the vaporization rate was about 2.7 ug/hr per liter of
liquor, or about 2.7 percent of the initial quantity per hour. The vaporization
rate in Run A-l, where the test liquor was maintained at 9°C, was much lower -
about 0.15 ug/hr/1 or 0.15 percent per hour.
For Runs B-l through B-4, where synthesized mixed liquor was used,
the average vaporization rate was about 0.06 ug/hr per liter of liquor, about
0.4 percent of the initial quantity per hour, or about 0.023 yg per liter of
gas. These rates are much lower than those obtained using water instead of
synthesized mixed liquor, a result consistent with the premise that PCBs would
adsorb onto solids, thereby inhibiting vaporization. However, these vaporization
rates obtained from mixed liquor are also lower than the results of Kaneko^
and Tucker in batch activated sludge units.
Cbmparison between the runs using air and mixed liquor on the one
hand, with those using nitrogen and autoclaved mixed liquor on the other hand,
indicates that tiie vaporization rates are significantly lower when steps were
taken to prevent biodegradation.
7.2 In-Situ Experiments at the Baltimore PCHM
Having observed the vaporization of PCBs from activated sludge under
laboratory conditions an air sampler for the activated sludge aeration basin was
constructed. The sampler was designed to isolate a portion of the surface of
the aeration basin by submerging a 12 inch diameter tube six inches below the
surface to insure a liquid seal but not to inhibit liquid circulation. A
diagram of the apparatus appears in Figure 9 with its placement in the aeration
basin. Air was drawn into the dirpinger train through a funnel with a diameter
of 8-3/4 inches placed four inches above the mixed liquor level in the aerator.
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Table 14
Laboratory vapor i»»t-inn Runs
Test Liquor:
Total Volume Prepared, ml
Distilled Water, % by vol.
Settled Wastewater, % by vol.
Return Sludge, % by vol.
Aroclor 1242 Aided, ug
Temperature of Liquor, °C
Liquor Autoclaved?
Liquor Withdrawn for Analysis, ml
Liquor Aerated, ml
Aroclor 1242 in Liquor Aerated, pg
Gas Sparoed:
Gas Used
Flow, liters/hour
Duration, hours
Total Flow, liters
PC3s Quantities, ug:
Test Liquor Prior to Aeration
Test Liquor After Aeration
Xnpingers
Unaccounted for
PCBs Vaporization Rate:
yg/bour
ug/liter liquor/hr
ug/liter of gas
Percent of Initial Quantity/hr
Unaccounted for PCBs:
ug/hour
ug/liter liquor/hour
Percent of Initial Quantity/hr
Run Nvnfcer
A-l
600
100
60
9
No
0
600
60
Air
1.56
6.0
9.36
(60)
57.0
0.53
2.5
0.088
0.147
0.057
0.15
0.42
0.7
0.7
A-2
600
100
60
40
No
0
600
60
Air
1.56
6.0
9.36
(60)
22.8
9.55
32.4
1.59
2.65
1.02
2.7
5.4
9.0
15.0
B-l
4,000
79.5
20.5
16
No
1,000
3,000
Air
7.80
6.0
46.8
16.8
22.2
0.68
-o
0.113
0.038
0.015
0,67
-0
-0
-0
B-2
4,000
79.5
20.5
400
16
No
1,000
3,000
300
Air
7.80
6.0
46.8
172.8
127.2
2.4
43.2
0.400
0.133
0.051
0.23
7.2
2.4
4.2
B-3
4,000
79.5
20.5
16
Yes
1,000
3,000
N2
.7.80
6.0
46.8
10.2
13.2
0.33
-o
0.055
0.018
0.007
0.54
-0
-0
-0
B-4
4,000
79.5
20.5
400
16
Yes
1,000
3,000
300
N2
7.80
6.0
46.8
302.4
302.6
0.83
-o
0.139
0.047
0.018
0.046
-0
-0
-0
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FIGURE 9, IN-SITU SAMPLER
DROPLET
CATCH vj\
RIND X
FLOW METER
VACUUM PUMP
"i C0( I ECTOfl fOH
CONDENSATION
ON RiNO
AERATION TANK
DECK
-------
A ring was positioned under the funnel, draining into a itetal can, to catch any
condensate and entrained droplets. The air flowrate through the impinger train
was maintained at 10 SCFH (283 liters per hour). Since the total air flew at
Baltimore in aeration tanks 3 and 4 was about 1,500,000 SCFH (42,500,000 liters
per hour, and the total surface area of these basins is 37,000 square feet, the
average air emission rate was 1,150 liters per hour per square foot of surface.
The 12-inch diameter collection tube isolated 0.785 square feet of surface, so
that about 900 liters per hour of air were emitted through the collector. The
excess air (900 - 283 or about 600 liters per hour) was released through a side
vent through a water seal of 2 inches depth.
However, the air at the Baltimore POTW is sparged from a header along
one side of each aeration basin, and there is a visually apparent gradient of
air emission across the 24-foot basin surface. The collector tube was situated
close to the sidewall at the same side as the air header, so that the actual
air captured was greater than the overall average.
The collector was positioned at the head of one aeration tank, 27.5
feet downstream from the mixing of influent wastewater and return sludge. The
total length of each tank (consisting of two basins) is 672 feet.
The impinger train consisted of three inpingers in series, each con-
taining 100 ml of ethylene glyool. After each run, the funnel and all tubing
in the train was washed, and combined with the impinger contents and with the
contents of the metal can (which turned out to be negligible). The PCBs
analysis was conducted in the same manner as in the preceding laboratory experi-
ments.
Two runs were made at the Baltimore POTW, on February 23 and 25, 1977.
PCBs in the impinger train were identified, and the quantitative results (which
show excellent agreement between the two runs) are as follows:
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Bun duration/ hours
Air flow through, train, 1/hr
Total air through train, liters
PGBs collected, yg
PCBs, yg/hr
PCBs, yg/liter air
7/23/77
3.5
283
990
0.68
0.194
0.00069
2/25/77
6.0
283
1,700
1.17
0.195
0.00069
The PCBs collected per liter of air, 0.0007 yg, is one-twentieth the
quantity in the laboratory experiment (0.015 yg in Run B-l) simulating the POTW
aerators.
During these runs, liquid samples were also collected at several
stations around the activated sludge units. Three samples (each 220 ml) were
collected at each station and composited on February 23rd, and four samples
(each 220 ml) were collected at each station and composited on February 25th.
The results of analyses for PCBs (in yg/1) are in Table 15, along with plant
operating flows for these periods and derived PCBs quantities. During these
runs, aeration basins (and clarifiers) 1 and 2 were out of service, and the
sludge recycle ratio was much higher than in the previous survey period.
During the February 25th run, mixed liquor samples were collected at
the head of an aeration tank (near the air collector), at the mid-point along
the tank length (at the end of the first basin of two in series), and at the
tail of the second basin. The flow in the tanks approximate plug flow, so that
appreciable loss of PCBs via any mechanism should result in a PCS concentration
decline along the tank length. The data in Table. 15 indicate no apparent decline.
The quantities of PCBs (Table 15) in the system illustrate the fact
that the system has a large capacitance for PCBs. As the return sludge is re-
circulated, about 3 pounds per day of PCBs are recirculated. In comparison,
the PCBs in the influent wastewater amounted to less than Q..2 pounds per day
during these runs. Since the PCBs concentrations in the influent wastewater
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Table 15
Baltimore POTW Activated Sludge System, 2/77
(Aeration Basins #3 and #4)
Flow Eates:
Influent Wastewater, mgd
Total Sludge, rogd
Return Sludge, mgd
Waste Sludge, mgd
Mixed Liquor, mgd
Air- Flow, minion fiTFH
PCBs Concentration, ug/T
Influent Wastewater
Effluent from Secondary Clarif ier
Secondary Sludge
Mixed Liquor: Head
Mid-Point
End
Average
PCBs Quantity, Ibs/day
Influent Wastewater
Effluent from Clarif ier
Waste Sludge
Return Sludge
Mixed Liquor to Clarif iers
2/23/77
12:15-3:45 p.m.
19.1
10.1
8.7
1.1
27.8
1.49
0.61
0.25
42.9
22.0
22.0
0.097
0.040
0.392
3.10
5.10
2/25/77
9:30 a.m.-3:30 p.m.
18.9
9.7
9.1
0.9
28.0
1.43
1.25
1.48
29.5
19.1
16.6
21.0
18.9
0.197
0.234
0.222
2.24
4.41
-75-
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was very low for these few hours (0.8 to 1.3 yg/1) compared to the average 8.8
ug/1 measured in the previous 8-day survey period, the secondary clarifier
effluent contained PCBs attributable not to the PCBs influent during these few
hours but to the PCBs accumulated previously in the recirculating mixed liquor.
Hence, while PCBs removal efficiencies during these time periods, calculated
from influent and effluent concentrations, were 59 and -18 percent; the PCBs
removal efficiencies for the secondary clarifier were 99 and 95 percent (based
upon mixed liquor and effluent PCBs quantities).
7.3 Conclusions
'Ihe quantities of PCBs in the air emitted from the liquid surface
were determined to be 0.00069 yg per liter of air from the in-situ measuranents.
Since the total air flow at the plant was 1.46 x 10s SCEH, or 990 x 106 liters
per day; the equivalent quantity of PCBs vaporized is 0.68 grams per day, or
0.0015 pounds per day. Even at tfie higher vaporization rate found in the labo-
ratory Experiment B-l (0.015 yg/liter air), the equivalent quantity of PCBs
vaporized would be 0.033 pounds per day. Either of these quantities is a
small fraction of the quantity of PCBs in recirculation in the mixed liquor
(3 Ibs/day), and is also a very small fraction of the quantities unaccounted-
for during the previous 8-day survey (6.8 Ibs/day). It is therefore concluded
that, vaporization of PCBs is not an important mechanism for removal of PCBs
from wastewaters in activated sludge systems (and by analogy in trickling filter
systems).
The circumstantial evidence, therefore, points to biodegradation as the
predominant mechanism for PCBs destruction in secondary systems. However, nc direct
measurement was maie at the Baltimore POTW to explicitly determine biodegradat i on
rate. A comparison of laboratory experiments B-2 and B-4 indicates that in the
former experiment, where biodegradation might have occurred, indeed 25 per-
cent of the initial PCBs were removed other than by volatilization. In experiment
B-4, where biodegradation was specifically inhibited, no significant quantities
of the PCBs disappeared.
-76-
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The Aroclor 1242 disappearance rate in experiment B-2 was 2.4 ug/l/hr;
results entirely consistent with those of Tucker et al., which -were 3.6 ug/l/hr,
(7)
for Aroclor 1242. If the expected initial Aroclor 1242 concentration (from
the quantity added) of 300 ugA is used rather than the measured 172.8 ug/1,
the disappearance rate for experiment B-2 is 9.5 ug/1. As stated in Section 6.2.3,
these PCBs biodegradation rates (from laboratory and pilot studies) are sufficient
to account for the PCBs concentration reduction achieved across the secondary
treatment processes at the Baltimore POTW.
These results indicate that biodegradation of PCBs may occur in
secondary treatment processes in POTVfe. Until biodegradation is jqpiicit-ly
determined, such as by using Ci4-labeled PCBs, as opposed to a hypothesis
based upon disappearance, the mechanism for disappearance must remain an open
question.
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REFERENCES
1. U.S. Environmental Protection Agency, Technology Transfer, Process Design
Manual for Upgrading Existing Wastewater Treatment Plants, October 1974.
2. U.S. Environmental Protection Agency, Office of Water Programs, Procedures
for Evaluating Performance of Wastewater Treatment Plants (Contract 68-01-
0107).
3. U.S. Environmental Protection Agency, Technology Transfer, Process Design
Manual for Sludge Treatment and Disposal, EPA 625/1-74-006, October 1974.
4. Fair, G.M., J.C. Geyer, and D.A. Okun, Elements of Water Supply and Waste-
water Disposal, 2nd ed., Wiley, N.Y. (1971).
5. Mass Balance Model for PCB Distribution, in PCBs in the United States:
Industrial Use and Environmental Distribution, Versar Inc., Final Report,
Task I, EPA Contract No. 68-01-3259 (February 25, 1976).
6. Kaneko, M., K. Morimoto, and S. Nambu, The Response of Activated Sludge to
a Polychlorinted Biphenyl (KC-500), Water Research 10, 157-163 (1976).
7. Tucker, E.S., V.W. Saeger, and O. Hicks, Activated Sludge Primary Bio-
degredation of Polychlorinated Biphenyls, Bull. Environmental Contamination
and Toxicology 14_, 6, 705-713 (1975).
8. Dube, D.J., G.D. Veith, and G. F. Lee, Polychlorinated Biphenyls in Treatment
Plant Effluents, J.W.P.C.F. 46_, 5, 966-972 (May 1974).
9. Choi, P.S.K., H. Nack, and J.E. Flirrn, Distribution of Polychlorinated
Biphenyls in an Aerated Biological Oxidation Wastewater Treatment System,
Bull. Environmental Contamination & Toxicology 11, 1, 12-17 (1974).
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BIBLIOGRAPHIC DATA
SHEET
1. Report
3. Recipient's Accession No.
. Title and Subtitle
PCBs Raioval in Publicly-Owned Treatment Marks
5. Report Date
April 19, 1977
6.
7. Authorfs
H. Sargent, Roderick A. Carr and Gregory A. Vogel
8. Performing Organization Rept.
No.
'. Performing Organization Name and Address
Versar Inc.
6621 Electronic Drive
Springfield, Virginia 22151
10. Project/Task/Work Unit No.
Task 13
11. Contract/Grant No.
68-01-3273
2. Sponsoring Organization Name and Address
U.S. Environmental Protection Agency
Criteria and Standards Division
Washington, D.C. 20460
13. Type of Report & Period
Covered
Final Report
14.
IS. Supplementary Notes
16. Abstracts
The removal of PC3s"'in' each major unit process of publicly-owned sewage treatment works (POTWs) was
quantified so that the reaoval efficiency results may be applied to other POTHs. Two POTWs, differing
widely in size and in influent FOBS loading, were each sampled on a 24-hour basis for 7 to 10 days.
The overall PO3s renewal efficiencies achieved were 83 to 89 percent, slightly lower than the sus-
pended solids renoval efficiencies achieved at the two plants. The steady-state PCBs raroval efficiency
of each unit process was strongly correlated to the corresponding suspended solids removal efficiency.
In addition, large day-to-day variations in unit process POBs removal efficiencies were correlated to
variations about the mean influent PCBs and BOO concentrations.
Although reasonable PCBs material Kaiannag were achieved for one of the two plants, PCBs removed
from the wastewaters of the other plant could not be accounted for in the sludges. PCBs loss by
volatilization from the secondary treatment processes was discounted as an important mechanism, the
result of explicitly analyzing the air emitted from the activated sludge aeration tanks. The quantities
volatilized were very snail fractions of the PCBs removed from the wastewaters.
17. Key Words and Document Analysis. 17o. Descriptors
Polychlorinated Biphenyls (PCBs)
Municipal Sewage Treatment Plants
Primary Sedimentation
Trickling Filters
Activated Sludge
Gas Chrctnatographic Analysis
Volatilization
Biodegradation
17b- Identifiers/Open-Ended Terms
17e. COSATI Field/Group
18. Availability Statement
Release Unlimited
19. Security Class (This
Report)
UNCLASSIFIED _
20. Security Class (This
^UNCLASSIFIED
21. No. of Pages
85
22. Price
FORM NTIS-SS IREV. 10-73) ENDORSED BY ANSI AND UNESCO.
THIS FORM MAY BE REPRODUCED
USCOMM-DC 9265-P74
1J.U . S . GOVERNMENT PRINTING OFFICE: 1978-720-335/6061
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