vvEPA
United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-81-019 Mar. 1981
Project Summary
Concentration Technologies
for Hazardous Aqueous Waste
Treatment
Alan J. Shuckrow, Andrew P. Pajak, and Jerome W. Osheka
Data 'were compiled on the
performance of unit processes for
concentrating hazardous constituents
of aqueous waste streams. During the
course of this study, information was
also collected on known ground and
surface water contamination
problems.
After the data were gathered
evaluations were made of the
applicability of each technology to the
identified contamination problems
Selected technologies were then
carried forward for more detailed
review. Compounds identified in the
waste streams fell into one of 12
chemical classes: alcohol, aliphatic,
amine, aromatic, halocarbon, metal,
miscellaneous, PCB, pesticide,
phenol, phthalate, or polynuclear
aromatic:
Next, an extensive literature review
was conducted to focus on the
selected technologies and on the 12
types of chemical compounds. Six
processes were concluded to have the
greatest potential range and
immediate applicability: biological
treatment, chemical coagulation,
carbon adsorption, resin adsorption,
membrane processes, and stripping.
Since it was evident that in most
cases no single unit process would be
sufficient to adequately treat the
diverse contamination problems likely
to be encountered, five process trains
were selected as being most broadly
applicable to the types of known
contamination. An analysis was then
performed of the ability of each
process train to treat each of three
selected contamination problems. The
resulting evaluations can help
determine the applicability of a given
technology to specific situations in the
absence of experimental data. Results
were also used to set priorities for
further study of the technologies in
the on-going phase of the project.
This Project Summary was develop-
ed by EPA's Municipal Environmental
Research Laboratory, Cincinnati, OH,
to announce key findings of the
research project that is fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
Contamination from unsecured
industrial waste storage and disposal
sites is widespread. Often this
contamination manifests itself in the
form of hazardous leachates and
contaminated ground and surface
waters. These contaminant streams
are diverse in terms of composition and
concentration, varying between and
within sites, or over time at any given
location. Some contaminant streams
contain a broad spectrum of organic and
inorganic constituents, while others
have only a few compounds.
Regardless of whether contaminant
streams are associated with active or
abandoned sites, there is often the need
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to detoxify or decontaminate these
hazardous aqueous wastes. Very
limited data and experience exist for the
treatment of hazardous aqueous
wastes. In order to fill this information
gap, the Solid and Hazardous Wastes
Research Division of the Municipal
Environmental Research Laboratory
(MERL) initiated a project to evaluate
and verify selected concentration tech-
niques for hazardous constituents of
aqueous waste streams. This project
involves literature search and data
acquisition, technology evaluations,
and experimental investigations to
evaluate and adapt appropriate tech-
nologies.
Project activities that preceded the
experimental investigations are
included.
Process Evaluation
Technologies were first characterized
and screened for potential applicability
on the basis of available data. The initial
step in the evaluation was to identify
technologies potentially applicable to
the concentration of hazardous
constituents of aqueous wastes. Thus,
early in the project, the following list of
candidate technologies was developed:
• Biological treatment
• Carbon Adsorption
• Catalysis
• Centrifugation
• Chemical precipitation
• Crystallization
• Density separation
• Dialysis/electrodialysis
• Distillation
• Evaporation
• Filtration
• Flocculation
• Ion exchange
• Resin adsorption
• Reverse osmosis
• Solvent extraction
• Stripping
• Ultrafiltration
Technology profiles were then pre-
pared for each of these unit processes
without regard to specific waste
streams to be treated. These profiles
were used to screen each technology for
its ability to concentrate specific
hazardous constituents of aqueous
wastes. At this point, certain
technologies were eliminated from
further consideration and others were
carried forward for more detailed
scrutiny.
Next an extensive literature review
was conducted to focus on the tech-
nologies that survived the initial
screening and on chemical compounds
in the contaminant classes listed below:
• Alcohol
• Aliphatic
• Amine
• Aromatic
• Halocarbon
• Metal
• Miscellaneous
• PCB
• Pesticide
• Phenol
• Phthalate
• Polynuclear aromatic
Chemicals in these classes have
previously been identified as occurring
at various hazardous waste sites.
Chemical treatability information on
more than 500 compounds was
reviewed and summarized, and the
information was assembled in an
appendix to the project report. To
provide a quick reference on the
treatability of the 505 different chemical
compounds listed in the report appen-
dix, a concise summary was included in
the body of the report.
As a result of the literature review,
the following unit processes were
determined to have the potentially
broadest range of applicability to the
treatment of hazardous leachates and
contaminated groundwater.
• Biological treatment
• Chemical coagulation
• Carbon adsorption
• Membrane processes
• Resin adsorption
• Stripping
These processes must be supplementei
with ancillary processes such a
sedimentation and filtration, however.
Formulation of
Process Trains
Since hazardous aqueous wast
streams vary widely in composition am
often contain diverse constituents, m
single unit process is capable o
providing optimum treatment. Rather
individual processes must be arrange*
in trains to achieve high levels o
treatment in the most cost-effectivi
manner. The objective was to identif
process trains that would produci
quality effluents when applied to thi
wide range of waste strean
compositions likely to be encountered
Five such process trains, incorporatinj
the selected concentration technolo
gies, were formulated. Each of thesi
process trains has particular strengths
and weaknesses. One or more of thes<
trains should be applicable to mos
situations dictating concentrator
treatment of hazardous leachate o
contaminated groundwater.
Process Train 1
Biological treatment followed b
granular carbon sorption (Figure 1) i;
applicable to the treatment o
wastewaters that are high in TOC, an
low in toxic (to a biomass) organics, am
contain refractory organics. Chemica
coagulation and pH adjustment an
provided for heavy metal removal an<
protection of the subsequent biologica
system. This step may not be necessan
if heavy metal concentrations are belov
toxicity thresholds and if the moderat*
removal efficiencies typical of biologica
treatment are sufficient. The furthei
removal of metals by activatec
carbon may also make chemical coagu-
lation unnecessary.
Biological treatment such as
activated sludge, rotating biologica
contactors, or anaerobic filters is
included to reduce BOD as well as
biodegradable toxic organics. This
treatment reduces the organic load tc
subsequent sorption processes. Tc
prevent rapid heat loss caused by the
accumulation of solids in the sorptior
columns, clarification and multimedia
filtration are provided. The intent is tc
reduce suspended solids to 25 to 5C
mg/L |
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Coagulant
and pH Adjustments
Influent
Chem
Coagulant
Backwash
luent
1
1
GAC
+ • -
Filtration
(Optional)
|
1
r
Biological
|— »• Sludge
•
Clarification
Spent
Carbon
Figure 1. Biological treatment/carbon sorption process train.
Granular carbon adsorption is
included to remove refractory organic
residuals and toxic organics. Activated
carbon rather than polymeric or
carbonaceous resins has been specified
because more full-scale experience
exists, and performance as well as
design and operating criteria have been
reported.
This process train is expected to be
highly effective and economical. Its
success, however, depends on
biological system performance. A
potentially major impediment to the use
of this process train is the possible
stripping of volatile compoundsfrom the
waste stream during aeration and the
resulting air pollution.
Because the process is intended to
handle multicomponent waste streams,
pollutant recovery for reuse is unlikely.
Three by-product wastes are produced:
chemical sludge, biological sludge, and
spent carbon. Spent carbon can be
regenerated, but the sludges must be
disposed of in an environmentally
acceptable manner.
Process Train 2
The second process train uses the
same unit processes but places
granular carbon ahead of biological
treatment (Figure 2). This train, which is
also applicable to high TOC
wastewaters, was designed to
respond to situations in which waste-
stream components may be toxic to
biological cultures. The rationale is to
use the activated carbon to protect the
biological system from toxicity
problems. The carbon would thus be
allowed to leak relatively high
concentrations of TOC (organics) rather
than to be operated to achieve
maximum reduction of organic
compounds. Allowable leakage would
be based on the point at which the
carbon-treated effluent becomes toxic
to the subsequent biological process.
Thus, selection of the allowable TOC or
organic leakage (i.e., breakthrough)
from the carbon contactors is crucial to
the performance and cost effectiveness
of this process train. If biologically toxic
Coagulant
and pH Adjustments
Influent
organics are present, treatability
studies must be conducted for several
reasons; one of the primary reasons
would be to establish the acceptable
breakthrough level. Higher organic
loads handled by the biological system
result in greater service life of the
granular carbon and, consequently,
lower costs related to the carbon
treatment phase.
In this configuration, the chemical
coagulation step (including settling and
filtration) plays a role in organics
removal and paniculate removal to
minimize head losses in contact
columns.
As with the process train m Figure 1,
there is little potential for recovery of
pollutants. But, volatile organic
compounds present in the waste stream
may pose less of a problem in this
process configuration si nee they maybe
sorbed onto the carbon before an
aeration step.
Process Train 3
The third process train (Figure 3) uses
biophysical treatment, which is a
combination of biological and powdered
activated carbon treatments conducted
simultaneously. This approach is
simpler than the sequential
carbon/biological treatments, and it
has the potential of achieving
comparable effluent quality. Potential
advantages include the use of less
costly carbon (powdered versus
Effluent
Chemical
^P* Coagulant
*\t*ttlinn
1 -
I
1
Sludge
Backwash
i
i
j
GAC
1
Spent
Carbon
Figure 2. Carbon sorption/biological process train.
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Coagulant
PAC
Influent-
Chemical
Clarification
(Opt)
,
I
Biological/
Carbon
Settling
\ I
'Effluent
Sludge
Figure 3. Biophysical process train.
granular) and minimal physical
facilities. Spent carbon/biological
sludge can be regenerated or dewatered
and disposed of directly. If the latter
approach is considered, economic
comparisons must include cost for
disposal of toxic-laden carbon sludge.
Complete mix activated sludge or
contact stabilization are the two
biological processes most frequently
used. Recent reports suggest operating
at long solids retention times,
concentrations of 20,000 to 25,000
mg/L (60% PAC and 40% biomass).
Process Train 4
Train 4 consists of a membrane
process preceding biological treatment
(Figure 4). This configuration would be
applicable to wastewaters containing
organic and inorganic pollutants.
Selection of the appropriate membrane
process, ultrafiltration, and/or reverse
osmosis would depend on wastewater
composition and treatment goals.
Ultrafiltration is a membrane process
capable of separating high molecular
weight (mw > ~ 1000) species from a
liquid stream on the basis of size.
Reverse osmosis uses a semipermeable
membrane to concentrate numerous
dissolved species, both organic and
inorganic. Salinity isan important factor
to be considered, since ultrafiltration
will allow dissolved salts to enter the
permeate stream, and reverse osmosis
will not. The use of reverse osmosis on
high salinity waste streams is therefore
questionable because large volumes of
concentrate are generated. Numerous
reverse osmosis membrane materials
and configurations are available.
Different configurations provide
different surface areas, flux rates, flow
velocities, and other process variables.
Care must be exercised in selecting
Sludge
membrane materials and configura-
tions. Organic removals of 20% to 70%
have been reported for reverse osmosis,
but some membranes (e.g., cellulose
acetate) tend to concentrate some
organics (e.g., phenol and aniline) in the
permeate stream.
A biological process was paired with
the membrane process to address low
molecular weight organics. As an
alternative, stripping processes could
be paired with membranes. Sorption
processes were not considered in
conjunction with membranes because
of the likelihood that the lower
molecular weight readily soluble
organics would pass through the
system.
A major disadvantage of the fourth
process train is that membrane
Coagulant
and pH Adjustments
processes generate concentrate
streams that require additional
handling and disposal. The concentrate
stream flow may be 10% to 20% of the
feed flow.
Process Train 5
A processing system consisting of
stripping and carbon adsorption is
illustrated in Figure 5. This
configuration will be applicable
primarily to wastewaters containing
organics, although chemical
coagulation for inorganics and
paniculate removal is provided. This
process flow may be suited to situations
involving volatile and refractory or toxic
organics. The method is essentially
pertinent in the presence of a single or
small number of volatile compounds
that can be recovered from the overhead
gas stream. Even though the
wastewater may contain air-strippable
compounds, air stripping may not be the
best selection if air pollution is a
potential concern (unless off-gases can
be contained and collected). Stripping
probably will remove biodegradable
rather than refractory TOC, and it has
therefore been paired with activated
carbon adsorption rather than a
biological process.
Aside from pH adjustment before
stripping, little pretreatment is
necessary. If the wastewater contains
Influent •
Chemical
Clarification
*... - 1
1
... J
P.O.
or U.F.
\
Concentrate
I
Backwash
Effluent
Biological
Sludge
Figure 4. Membrane/biological process train.
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readily settleable suspended solids,
removal before packed column or tray
tower steam stripping will prevent
solids buildup in the stripping unit.
The steam stripping process train
generates three waste streams:
overhead condensate, chemical sludge,
and spent carbon. Assuming that
carbon will be regenerated, either on-
site or by a commercial service, the two
remaining streams require additional
treatment and/or disposal. Preferably,
the organic phase of the overhead
condensate can be recovered and
reused , with the water phase returned
to the treatment system. If recovery is
not possible, however, incineration is
the best method for condensate
disposal. Chemical sludge should be
dewatered and disposed by a method
compatible with the materials
contained in the sludge.
Evaluation of
Process Trains
Process trains illustrated in Figures 1
through 5 do not represent the only
possible configurations. They do,
however, encompass the concentration
technologies that are expected to have
the greatest broad-range applicability
and effectiveness. They are the
processes that have been demonstrated
for the treatment of hazardous aqueous
wastewaters.
Before experimental studies were
initiated, it was decided to evaluate the
five process trains to predict
performance potential on actual
hazardous waste streams. Based on
unit process performance data compiled
from the literature, the performance
potential of each of the five process
trains was calculated for each of the
three actual waste streams. These
calculations indicated that all of the
process trains were potentially capable
of producing effluents suitable for direct
stream discharge. But because much of
the available data were generated from
single-compound, laboratory-scale
.studies, actual treatability of a
multicomponent wastewater cannot be
accurately assessed. Treatability
studies using the actual wastewaters
are needed to verify performance
expectations and to select the optimum
process train for a particular situation.
The full report was submitted in ful-
fillment of Contract No. 68-03-2766 by
Touhill, Shuckrow and Associates, Inc.,
under the sponsorship of the U.S.
Environmental Protection Agency.
Coagulant
Influent -p-
L-
Air/ Steam
Strip
t
,
Chemical
i
Sludge
riiiiaiiuii
1
1
-i 1
1
1
Spent
Carbon
—^Effluent
Backwash
Figure 5. Stripping/carbon sorption process train.
Alan J. Shuckrow, Andrew P. Pajak, and Jerome W. Osheka are with Touhill,
Shuckrow and Associates, Inc., Pittsburgh, PA 15237.
Stephen C. James is the EPA Project Officer (see below).
The complete report, entitled "Concentration Technologies for Hazardous
Aqueous Waste Treatment,"(OrderNo. PB81 -150583;Cost:$26.0O, subject
to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Municipal Environmental Research Laboratory
U. S. Environmental Protection Agency
Cincinnati, OH 45268
> US.OOVERNMENT PRINTINGOFFICE. 1M1-757-064/0296
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