United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S2-90/012 Aug. 1990
&EPA Project Summary
Performance of Activated
Sludge - Powered Activated
Carbon - Wet Air Regeneration
Systems
Kevin J. Deeny, James A. Heidman, and Arthur J. Condren
The investigation summarized in
this report was undertaken to
evaluate the performance of
powdered activated carbon (PAC)
technology used in conjunction with
wet air regeneration (WAR) at
municipal wastewater treatment
plants. Excessive ash concentrations
accumulated in the mixed liquor
suspended solids (MLSS) at all
facilities that relied on the WAR unit
blowdown for ash control. A variety
of ash control methods have been
implemented and are documented.
The nitric acid test for PAC was
shown to substantially overestimate
PAC concentrations. Previous claims
that PAC losses through WAR are 5%
or less were based on selected use
of the nitric acid test. PAC losses
across WAR or the desirability and
economics of recovering the volatile
suspended solids. (VSS) exiting the
WAR reactor could not be quantified.
Other areas covered in the report
include adsorptive capacity of the
recycled material, tertiary filter per-
formance, metals accumulation,
oxygen transfer, operation and
maintenance concerns and economic
considerations. The report includes
Appendices submitted by the system
manufacturer that dispute many of
the report conclusions and provide
alternative explanations for some of
the data obtained.
This Project Summary was
developed by ERA'S Risk Reduction
Engineering Laboratory, Cincinnati,
OH, to announce key findings of the
research project that is fully
documented in a separate report of
the same title (see Project Report
ordering information at back).
Introduction
Addition of PAC to activated sludge
systems is a proven technology for
wastewater treatment. The use of wet air
oxidation for the treatment of non-PAC
sludges, such as primary and secondary
sludges, is also an established
technology. Eleven municipal facilities in
the United States have been built using
these combined technologies, with the
wet air oxidation process, which is
commonly called WAR, used for
oxidation of excess biological solids and
regeneration of spent PAC.
Nearly all municipal systems designed
for PAC addition in the United States
have included WAR. A majority of these
systems received Federal funding under
the innovative technology program. The
evaluation summarized in this report was
undertaken to document the performance
of the PAC/WAR technology at municipal
plants. The information on plant operation
and performance reflects data available
on or before August 1988.
Technology Description
Figure 1 illustrates a flow diagram for
a typical municipal system incorporating
the PAC/WAR technology. Virgin PAC is
added to the activated sludge system
influent as a make-up dosage. A slip
stream from the the secondary clarifier
-------
underflow, which is composed of an
activated sludge/PAC mixture, is
thickened before being pumped to WAR.
Effluent filters, at one time considered
optional (1), were installed in nearly all of
the municipal systems.
The purposes of the WAR systems
are to destroy excess biomass,
regenerate PAC and provide a means of
controlling ash build-up.
High pressure feed pumps are used to
pump the activated sludge/PAC mixture
to the WAR system and to sustain an
operating pressure of approximately 800
psi. Air is injected into the sludge/PAC
stream by means of multiple-stage high-
pressure compressors. Heat exchangers
are included for the mutual functions of
reducing the temperature of the treated
material and increasing the temperature
of the incoming material. The
air/sludge/PAC rrjixture reacts in a vessel
(reactor) for a period of 25 to 50 min
before being discharged through the heat
exchangers. Steam boilers are used at he
beginning of each operating cycle to
raise the system temperature. The
oxidation reaction generally provides
most of the heat required to sustain the
reaction temperature between 230 °C to
245°C. Material exiting the WAR system
consists of a mixture of PAC, other VSS,
nonvolatile suspended solids (NVSS),
and a large component of soluble
organics (which are formed in the for the
process). In accordance with the claims
process (2), the WAR reactor blowdown
stream was the only means of controlling
ash in the original design approach. This
stream was to be mixed with plant
effluent and a return stream from a
parallel plate settler underflow, before
flowing to the settler for separation of the
PAC and ash materials. The settler
overflow, containing recovered PAC, was
to be returned to the process. A portion
of the settler underflow, containing settled
ash, was to be wasted.
Study Procedures
Initially, discussions were held with
personnel at the operating facilities, U. S.
Environmental Protection Agency (EPA)
regional offices, and the process
From
Primary
Clartfiers
lTo Tertiary Filters
i Cake Disposal
Figure 1. Flow Diagram of Typical System with PAC/WAR.
-------
manufacturer (Zimpro Inc.) to gather
background information. Typical process
data were collected from the various
facilities and reviewed. Site visits to five
facilities were made to review the
intended versus the actual operation, and
the types of plant records maintained and
analyses performed; a thorough plant
inspection documented locations of
sampling points and sidestreams.
Following a preliminary analysis of the
data and assessment of the PAC/WAR
process, an interim meeting was held
(12/87) with personnel from Zimpro, EPA
and the assessing contractor to review
and discuss the preliminary findings.
Information and discussions from this
meeting were used by EPA to determine
steps needed to complete the evaluation.
Subsequently, two more facilities were
visited to gather additional data.
Supplemental conversations were then
held with people at the various operating
plants to confirm information or secure
missing data. This information was
analyzed along with other published data
to complete the technology evaluation.
A summary of the results was
presented and discussed during a final
meeting (8/88) with several EPA
personnel, Zimpro personnel, and the
contractor team. Discussions during the
final review meeting and subsequent
communications with Zimpro Inc., have
clearly indicated a difference of opinion
as to the appropriate interpretation of
much of the assembled data. For this
reason, comments from Zimpro Inc., are
provided in two appendices to the final
report so that their viewpoints will also be
available to the reader.
Plant Summary
The municipal PAC/WAR facilities that
were reviewed are summarized in Table
1. Color reduction, nitrification, limited
space availability and toxics removal
were the predominant factors given for
selecting this technology. Effluent permit
limits range from typical 30/30 mg/L for
BOD5 and total suspended solids (TSS)
(with and without nitrification) to summer
limits at Kalamazoo of 7/20/2/1 mg/L for
BOD5/TSS/NH3-N/Total Phosphorus. The
current status of municipal facilities
indicates that all have, in some way,
modified the original design and/or of
their systems.
Ash Accumulation and Control
Mixed liquor ash accumulation was a
common problem at all full scale
PAC/WAR facilities listed in Table 1.
when they were operated as originally
designed. The size and specific gravity of
the ash and PAC particles were found to
be similar, and effective separation would
not occur. As a result, ash was returned
to the process from the Lamelle settler
along with the PAC. Mixed liquor ash
levels of from 60% to 80% were
observed at facilities that relied solely on
WAR unit blowdown for ash control. This
led to the loss of excess TSS from the
secondary loadings on the tertiary filters.
A variety of methods were initiated for
ash control. Vernon discontinued PAC
addition for several months at a time, but
continued to run the WAR system.
Mixed liquor was occasionally purged to
the primary clarifiers for disposal with the
primary sludge. PAC addition was
recently reinitiated to control effluent
color. Mount Holly discharges a portion of
the WAR unit effluent to the primary
sludge dewatering system for disposal.
East Burlington practices direct
dewatering of a WAR reactor effluent slip
stream. PAC addition at South Burlington
has been discontinued, and the plant
currently operates as a conventional
activated sludge facility. Kalamazoo
purged mixed liquor for ash control
before constructing a differential
sedimentation and elutriation (DSE)
system to separate ash. Bedford Heights
switched to addition of a nonactivated
carbon (NAG), which is used on a throw-
away basis (no WAR system operation).
The NAC costs $0.16/lb, which is roughly
half the cost of a typical PAC, and is
maintained at the minimum concentration
needed for satisfactory plant operation.
Medina County is operating a modified
DSE system and is dewatering the ash
with the primary sludge. North Olmsted
experimented with several operating
modes, with and without WAR unit
operation and with and without PAC or
NAC addition. They recently switched to
conventional activated sludge operation
but plan to convert back to the use of
NAC. Sauget added PAC during start-up,
but a catastrophic failure of a heat
exchanger made it impossible to operate
their WAR system. The initial PAC dose
has since been wasted from the plant. El
Paso is wasting a slip-stream of sludge
upstream from their WAR reactor to
anaerobic digesters.
Differential Sedimentation and
Elutriation (DSE)
Zimpro Inc., conducted a number of
standardized pilot plant studies of the
DSE process to estimate the
requirements for full-scale ash removal
facilities. On average, the results
indicated that 37% ash removal and 90%
VSS recovery would be reasonable
expectations. Four of the PAC/WAR
systems either have or are in the process
of installing DSE systems.
A slip-stream of the WAR unit effluent
is blended with softened water in an ap-
proximately 1:4 volumetric ratio.
Dispersants, such as sodium hexameta-
phosphate or metasilicate, and an anionic
polymer are then added before an up-
flow elutriation tank. VSS (including PAC)
are concentrated and removed in the
underflow, and the ash fraction is
concentrated and exits in the overflow.
Cationic polymer addition flocculates the
ash, and this stream is sent to a clarifier
for separation. A filter press is the normal
mode for dewatering the concentrated
ash underflow. East Burlington has a full
scale DSE system but, because of the
low PAC dosage required for satisfactory
wastewater treatment, does not consider
it cost effective to operate. Instead a
slip stream of WAR reactor effluent is
sent to a dedicated filter press for
dewatering. The system at Jessup, MD,
was not in operation at the time this
technology evaluation was conducted. A
full scale system at Kalamazoo was
brought on line in June 1988. Data from
the modified DSE system at Medina were
unavailable for incorporation in this
evaluation.
Ash Balances and Accumulation
East Burlington and Kalamazoo
maintain extensive plant records and also
monitor internal sidestreams. Material
balances for several parameters (e.g.,
TSS, VSS, and NVSS) around their
aeration basins and WAR units were
developed from the operating records at
these plants. An excellent TSS balance
was developed for 1 yr of record at the
East Burlington plant. The recycled ash
(NVSS) from the WAR unit constituted
83% of the ash entering the aeration
basins.
Figure 2 illustrates the buildup of
various MLSS components that was
experienced over a 273-day period at the
Kalamazoo facility. This operating period
was selected because it does not include
the removal of 4 million gallons of mixed
liquor from the aeration basins for
temporary ash reduction, which occurred
in the last quarter of 1986, nor does it
include the period of sustained high
effluent TSS, which occurred in the last
quarter of 1987. The mixed liquor carbon
volatile suspended solids (PAC)
concentration was measured by a nitric
acid digestion procedure discussed in the
next section of this summary. During the
periods when effluent quality was
reasonably satisfactory (April through
-------
Table 1. Summary of Municipal PAC/WAR Facilities Reviewed
Permit Limits
Facility
Vernon, CT
Mt. Holly. NJ
E, Burlington, NC
S. Burlington, NC
Kalamazoo, Ml
Bedford Hts., OH
Medina Co., OH
N. Olmsted, OH*
SaugetlL
EIPaso.TX
Flow, mgd
Current/
Design
4.2/6.5
2.4/5.0
7.0112.0
6.8/9.5
25/54
3.4/3.5
7/10
6/7
16/27
4.5/10
PAC/WAR
Status' i
MA [
MA l
MA '•
AS
MA :
NAC '•
MA S
AS I
AS i
MA ,
i-ieason
for
PAC"
C
C,S
C.N.T
C,N,T
C,N,T
N,S
N
N.S
T
A/,0
BODg,
mg/L
~W
30
72-24
12-24
7-30
10
10
10
20
SD##
rss,
mg/L
20
30
30
30
20-30
12
12
30
25
SD
NH3-N,
mg/L
20
4.0-8.0
4.0-8.0
2.0-10.0
5.1
1.5-8.0
2.3-6,9
""*
SD
*MA = Modified operation and/or design for ash pontrol.
AS = Converted to conventional activated sludge.
NAC = Converted to the use of nonactivated carbon without regeneration.
-C - Color Removal, S = Space, N = Nitrification, T = Toxics, O = Organics.
*Plan to convert to NAC without regeneration.
##SD - Secondary Drinking Water Standards.
mid-September), there was a continuous
increase in ash concentrations.
PAC Measurements and Loss
Analytical Procedures
Attempts to construct mass balances
for PAC from plant records were
unsuccessful. Determination of the PAC
content in the mixed liquor is an
important process control parameter, and
the inability to perform PAC balances
was deemed significant. This led to a
review of the nitric acid test method used
to determine the PAC fraction of the
MLSS in PAC/WAR systems.
The MLVSS measured in PAC/WAR
system aeration tanks may be presumed
to include active biomass, residue,
nondegradeable VSS in the entering
wastewater, recycled and virgin PAC,
organics bound to the PAC (which are
measured as VSS), and any inert VSS
formed in and/or not oxidized or
solubilized in the WAR process.
PAC/WAR plants have traditionally
classified all VSS in the aeration basin as
either PAC or biomass, with the PAC
concentrations measured on an ash free
basis. The analytical method provided to
the facilities to differentiate between
these two classes of VSS assumes that
all non-PAC VSS are dissolved by nitric
acid digestion.
According to Zimpro personnel (3), the
nitric acid digestion technique was
developed at Zimpro to attempt to
quantitatively determine the biomass and
powdered carbon in a mixture. A number
of claims concerning the accuracy and
appropriateness of the test are doc-
umented in the Report.
Plant Operating Results
In addition to using the nitric acid test
procedures forf process control, several
operating facilities also use the nitric acid
techniques to measure the PAC losses
across the WAR unit. The individual
measurement results from three facilities
where these data were available are
summarized in Table 2.
Nine months of data from both East
Burlington and tKalamazoo were analyzed
in attempts to establish PAC balances for
these facilities. The results of this
analysis are presented in Table 3. These
material balances show that Kalamazoo
measures daily losses and accumulations
of PAC that exceed the PAC addition rate
by a factor of four. East Burlington
measures daily PAC losses that are five
times higher than the mass of daily PAC
addition. Since measurement of the PAC
addition rate does not depend on the
nitric acid procedure and has been
verified through comparison with plant
purchase and [use records, the average
rate of PAC addition is known. Therefore,
the nitric acid procedure substantially
overestimates PAC concentrations,
making the measured value of this
parameter of no quantitative significance.
A steady state mass balance was also
developed for East Burlington to evaluate
aerator PAC concentrations as a function
of PAC loss in WAR and in effluent and
waste solids. JThe results indicated that
the PAC concentrations measured in the
aerator with ihe nitric acid test were
higher than could be present. A
comparison of the measure value with
computed values for various assumed
oxidation losses in the WAR unit
indicated that even with no PAC oxidation
in WAR, the measurement error
[(measured value-true value) true value]
would be 67%.
Results of previous VSS destruction
studies on wet air oxidation of sludges
not containing PAC are summarized in
the report and show that most, but not all,
of the VSS are oxidized or solubilized. A
small portion of VSS does not go into
solution and, as shown in Figure 1,
nondegradeable VSS entering the plant
that are neither oxidized nor solubilized
by WAR must cycle in the system until
escaping in the plant effluent or until
being removed in a waste stream. Part or
all of the gradual buildup in MLVSS at
Kalamazoo, as shown in Figure 2, can be
attributed to this type of material.
Biomass destruction through WAR
(measured by the nitric acid test) at
Kalamazoo decreased from greater than
96% shortly after start-up in 1985 to an
average of 83% during the first 5 mos. of
1988.
The characterization of the VSS
existing WAR (as measured by the nitric
acid test) at three facilities are sum-
marized in Table 4. The accumulation of
this "biomass" material contributes to the
falsely high values for the measured PAC
concentrations.
The absence of a correlation between
PAC addition and PAC levels (as
measured by the nitric acid procedure) at
Kalamazoo is apparent in Figure 3. Ten-
-------
day moving averages of PAC addition
minus the estimated daily PAC loss
calculated from the effluent VSS values
and the measured PAC percentage in the
aeration basins) are shown along with the
measured 10-day moving average values
of mixed liquor PAC concentrations in the
aeration basins. There is a gradual rise in
the measured PAC concentrations that,
on a long term basis, is independent of
the PAC addition rate.
PAC Loss by WAR
The data summarized in Table 2
indicate PAC losses across WAR units to
be in the range of 30% to 40% per
regeneration. As shown in Table 3,
however, the magnitude of the PAC loss
exceeds by four to five fold the amount of
PAC added; this shows that the absolute
values of the PAC concentration
measured by the nitric acid digestion
technique are meaningless. Whether or
not the relative change of 30% to 40%
represents the actual percentage loss per
WAR cycle cannot be determined from
the data available.
In previous pilot studies of PAC
systems with WAR, Zimpro reported low
PAC losses through WAR. For
example.results reported from Back River
(4) stated that the WAR unit operated
with PAC recovery efficiencies in excess
of 95%. In an attempt to ascertain the
reason for the large variations between
the Back River results and those
observed at the three facilities
summarized in Table 2, a detailed
analysis of the Back River report was
undertaken. The reasons for the apparent
differences are related to the selected
use of the nitric acid procedure and are
detailed in the final report.
Tertiary Filtration
Tertiary filters were installed in nearly
all of the municipal PAC/WAR facilities
even though several facilities have an
effluent TSS limit of only 30 mg/l. Solids
capture in secondary clarification was not
adequate at East Burlington or Kala-
mazoo to consistently meet the discharge
permit indicating the key role played by
the tertiary filters at these locations. In
addition, polymer assisted clarification
was normally used at the various
facilities. Typical polymer costs were
estimated at $21,000/yr/MGD based on
an applied dosage of 2.75 mg/l and a unit
costs of $2.50/dry Ib.
Recycle Loadings
PAC systems have a high mass of
organics, nitrogen and phosphorus in the
WAR reactor effluent. The WAR return
stream can represent a significant portion
of the loading applied to the secondary
process. Organic (BOD5) recycle loading
at E. Burlington and Kalamazoo ranged
from 11 % to 29% of the primary effluent
loading and the NH3-N loading ranged
from 54% to 120%.
Kalamazoo monitors total phosphorus
in the WAR return stream. The
concentration is high and represents
730% of the mass loading from the
primary clarifier. This facility has a
phosphorus limitation and adds alum to
the secondary system for its precipi-
tation. The precipitated phosphorus
compounds and those resulting from
cellular destruction by WAR have
concentrated as an insoluble, inert
recycled material.
Adsorptive Capacity of
Recycled PAC
It is difficult to characterize the
adsorptive capacity of the material exiting
the WAR system. Attempts to
characterize the regenerated PAC from
the Sauget pilot study (5) showed that the
COD adsorption capacity was too low to
measure. That study concluded that
comparison of virgin and regenerated
PACS was not an appropriate indicator of
performance.
Recktenwalt (6) reported that PAC
subjected to multiple regenerations does
not retain significant capacity for
adsorption of low molecular weight
compounds such as 2,4-dinitrophenol. On
the other hand, methylene blue
adsorption after regeneration was
essentially the same as that for virgin
PAC. Materials that have adsorptive
properties similar to methylene blue
should adsorb as well to the recycled
VSS as to virgin PAC.
Metals Accumulation
Activated carbon will adsorb some
heavy metals. This removal mechanism
could help reduce the toxicity to
biological functions in PAC/activated
sludge systems. One facility (Bedford
Heights) experienced operating and
Table 2. Measured PAC Losses Across WAR by Nitric
Acid Digestion
Measured PAC
Loss per WAR Number
Location Period Cycle, % of Samples
Table 3. PAC Balances
Kalamazoo 2/88-5/88 40.6
£ Burlington 1/87-2/88 30.8
Mt. Holly 1/87-7/87 32.1
46
31
48
Parameter
Input
PAC Added'
Kalamazoo,
Ib/day
3,704
Total 3,704
East
Burlington,
Ib/day
404
404
Loss + Accumulation
PAC Accumulation' 1,277 0
PAC in Final Effluent" 1,056 232
PAC Destroyed in WAR" 11,452 1,596
PAC Removed in Filter Press Solids"1 0 344
Total 73,785 2,172
"Reported on an ash-free basis.
"Based on nitric acid test procedure.
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uillllilinjiiiui^iiliNiNlilllliiiiimun.lllNllllil-uiuu
i 16 31 46 61 76 91 106 121 136 151166 181 196 211 226 241 256 271
Jan 1 to Sept 30, 1987
o MLSS mg/l + MLVSS, mg/l « MLCVSS, mg/l
figure 2. Aeration basin suspended sdjids components at Kalamazoo, Ml.
effluent quality problems that were
attributed to heavy metals accumulation.
This facility later controlled ash and ash
associated heavy metal accumulations by
substituting NAG for PAC and
abandoning attempts at media recovery.
The Vernon facility noted high metals
concentrations in the blend of primary
and waste secondary sludge fed to the
vacuum filters and conducted an EP
Toxicity Extraction to determine the
Resources Conservation Recovery Act
(RCRA) status of the sludge. Results of
the EP Toxicity Extraction analyses
indicated that the metals did not leach
appreciably under conditions of the test.
Operations and Maintenance
Considerations
A WAR unit is composed of high
temperature and high pressure compo-
nents. Operating temperature/ pressure
conditions require that repairs (such as
welding) be performed by certified
craftsmen and that all repairs be
completed in such a manner that the
pressure and temperature rating
certifications are maintained.
Operations of a WAR system requires
a working knowledge of boiler water
chemistry. Several facilities experienced
coil failures in their WAR system boilers
that were reported to be the result of
inadequate deoxygenation of boiler feed
water. Othei" facilities experienced
frequent failure of high pressure valves
that required I replacement of trims and
seats. A design modification to utilize
ceramic components has decreased the
failure rate at] some facilities. Kalamazoo
and Mount Holly have located alternative
suppliers which has resulted in valve
component increased service life and
reduced co:St. North Olmsted had
difficulty in! obtaining replacement
components, borne of which had a 52-wk
delivery schedule because of the special
nature of the alloys specified by the
system manufacturer.
Scale formation in the WAR reactor
reported by several facilities. Formation
was severe at some plants, resulting in
limited throughput capacity and
decreased operating temperature. Scale
formation continued to occur in some
plants that regularly acid cleaned their
WAR systems. Manual removal of scale
with water lasers has been required at
some facilitieb-
Significant scum accumulation on the
surface of secondary clarifiers was
experienced at three facilities. The cause
(s) for these accumulations has not been
determined.
Additional O & M considerations in-
cluded frequent maintenance on the last
stage of multi-stage air compressors, ab-
rasion-related repairs to slurry transfer
pumps, and check valve problems on
high pressure feed pumps.
Economic Considerations
A few facilities maintained separate
records of the costs associated with WAR
system, O & M. Average monthly O & M
costs in 1986 (parts, electricity,fuel oil
cleaning and labor) for one facility that
processed an average of 42,000 gpd,
containing 26,300 Ib/d of TSS, through
their WAR unit averaged $21.86/1,000 gal
or $35.13/1,000 Ib of TSS processed
through the WAR unit. Another plant that
also maintained separate cost records
computed 1986 WAR processing costs
(fuel, water, electric @ $.07/Kwh, repairs,
and labor) to be $27.68/1,000 gal or
50.88/1,000 Ib of TSS.
Bedford Heights maintained detailed
records of WAR operating costs. For an
-------
2 -
7 -
0
-7 -
-2 -
-3-
-4-
-5
+\
+ Carbon In-Out, LB/D
D 10-day MLCVSS, mg/l
I I
7 76 37
I1""
46
T"
67
""I '"
76
97
I
706
I
736
Jan-Sept. 1987
151 166
I I I I I
787 796 277 226 247
I
256
I
277
Figure 3. Ten day moving average ofPAC addition less loss and measured aeration basin levels at Kalamazoo, Ml.
11-mo period in 1986, the WAR unit
processed 2.58 million gal at an average
cost $42.00/1,000 gal (labor, natural gas,
electricity, water lubricants, and repairs).
The cost was equivalent to $75.58 per
1,000 Ib processed. Bedford Heights also
operates a low pressure oxidation (LPO)
unit for primary sludge conditioning. The
1986 LPO operating costs (labor, utilities,
repairs) were $15.00/1,000 gal con-
ditioned in this unit.
Bedford Heights considered installing
a DSE system during their cost
effectiveness analysis of options to
address ash buildup problems. Instead,
they chose to substitute NAG for PAC
and waste the excess biomass/NAC
mixture to the primary clarifiers. The
combined sludge is now conditioned in
the LPO unit and the WAR unit is no
longer operated as such. They have
proposed to convert the WAR unit to an
additional LPO unit.
The economic analysis performed for
the retrofit DSE system at Kalamazoo
assumed that all VSS that exited the
WAR system were PAC (7). Based on the
nitric acid procedure, the PAC content is
only 68% of the total VSS (Table 4).
Based on the mass balances presented
earlier, however, it is clear that the actual
PAC concentration is substantially less
than that measured by this testing
procedure. Since there is no analytical
procedure available for the determination
of true PAC content, the cost
effectiveness of the Kalamazoo DSE
system cannot be accurately determined
on the basis of the reported value of the
PAC that is recovered by the system.
Table 4. Characterization of VSS from
WAR
Facility % PAC' % Biomas"
E. Burlington
Kalamazoo
Mt. Holly
79.0
67.7
79.2
21.0
32.3
20.8
"As measured by the nitric acid procedure
Operating costs for DSE systems
include those associated with water,
water softening, dispersant and dual
polymer application, power and labor.
Manufacturer pilot studies were used to
project these costs to be approximately
$20/1,000 gal of material processed.
Given the inaccuracy of the estimates of
PAC content, it is difficult to determine
the benefit of a DSE system operation
over that of direct wasting of a fraction of
the material, as is practiced by several
facilities.
The full report was submitted in
fulfillment of EPA contract No. 68-03-
3429 by James M. Montgomery
Consulting Engineers, Inc. under the
sponsorship of the U.S. Environmental
Protection Agency.
References
1. "Powdered Carbon: Right Combination
at Tight Times", Reactor, 57, Zimpro,
Inc. , June 1986.
-------
2. Bendt, C. L, Wet Air Regeneration of
PAC, presented at the International
Conference on Application of
Adsorption to Wastewater Treatment,
Vanderbilt University, February, 1981.
3. Knopp. P. V., et a!., "Wet Oxidation
Regeneration", in Carbon Adsorption
Handbook, edited by P. N.
Cheremisinoff and F. Ellerbusch, Ann
Arbor Science Publishers, Ann Arbor,
Ml, (1978).
4. Pilot Activated Sludge and Powdered
Carbon Enhanced Activated Sludge
Study at Baltimore, Maryland's Back
River WWTP, prepared by Zimpro
Inc. , Rothschild, Wisconsin.
5. Vollstedt, T J. and Berrigan., J. K.,
"Evaluation 'of Ash Removal from a
PACT/WAR^ pilot System at the
American Bottoms RWWTP", Zimpro
Inc., Rothschild, Wisconsin, July
(1987). ;
6. Recktenwalt M.A., fWet Air
Regeneration of PAC. in the
PAC/Activated Sludge Prgcess", M.
S. thesis, Environmental Engineering
in Civil Engineering, University of
Illinois, Urbana, IL(1986).
7. "Ash Removal Carbon Recovery
System Testing and Proposed Full-
Scale Design for the Water
Reclamation Plant, Kalamazoo
Michigan", Zimpro Inc., August
(1986).
Kevin J. Deeny is with Jumkins Engineering, Inc., Morgahtown, PA 19543-0368;
James A. Heldman (also the EPA Project Officer, see below) is with the
Risk Reduction Engineering Laboratory, Cincinnati, OH 45268; and Arthur
J. Condron is with James M. Montgomery Consulting Engineers, Inc.,
Pasadena, CA 91109-7009.
The complete report, entitled "Performance of Activated Sludge-Powered
Activated Carbon-Wet Air Regeneration Systems," (Order No. PB 90-
188889IAS; Cost: $17.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161 i
Telephone: 703-487-4650
The EPA Project Officer can be contacted at: :
Risk Reduction Engineering Laboratory
U.S Environmental Protection Agency
Cincfncinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental! Research
Information
Cincinnati OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
Official Business
Penalty for Private Use $300
EPA/600/S2-90/012
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