United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-86/028 July 1986
&EPA Project Summary
Preliminary Assessment of
Hazardous Waste
Pretreatment as an Air
Pollution Control Technique
James J. Spivey, C. Clark Allen, Robert L. Stallings, D. A. Green, J. P. Wood, and
Benjamin L. Blaney
Many hazardous or potentially haz-
ardous waste streams that contain
volatile compounds can be emitted to
the atmosphere during waste storage,
treatment, and disposal. One way to
minimize or eliminate these emissions
is to pretreat wastes to remove these
compounds.
The full report examines 72 waste
streams containing volatile compounds
and the technical applicability of 12 pre-
treatment techniques (e.g., steam strip-
ping) for removing volatile compounds
from them. Based on this analysis, con-
clusions are derived about the general
applicability of these techniques to haz-
ardous waste streams for volatile re-
moval. In addition, a cost analysis is
performed for each of the 12 pretreat-
ment techniques to determine the unit
costs of VOC removal.
This Project Summary was devel-
oped by EPA's Hazardous Waste Engi-
neering Research Laboratory, Cincin-
nati, 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 infor-
mation at back).
Introduction
The purpose of this study was to con-
duct a preliminary assessment of the
technical and economic feasibility of
various pretreatment techniques for the
removal of volatile constituents from
hazardous waste streams. This study
was conducted in response to increas-
ing concern over the potentially adverse
health and environmental conse-
quences associated with emissions of
volatile substances from hazardous
waste treatment, storage, and disposal
facilities (TSDFs).
According to U.S. Environmental Pro-
tection Agency (EPA) national survey of
TSDFs conducted in 1981, there are
about 4,820 TSDFs in this country man-
aging a total of about 151 billion liters of
hazardous waste annually. There are a
number of sources within TSDFs from
which volatile emissions can be emit-
ted. These sources include aerated im-
poundments, landfills, land treatment,
surface impoundments, cooling towers,
storage tanks and general process oper-
ations. While in many cases these emis-
sions can be controlled by add-on
equipment (e.g., carbon canisters), an-
other option is to remove volatile com-
pounds from waste before the waste en-
ters these TSDF processes.
Approach
The approach to this project was to:
1. Identify an appropriate hazardous
waste stream data base for use in
assessing the feasibility of VOC re-
moval by waste treatment.
2. Identify general pretreatment unit
processes (e.g., adsorption) that
can be used to remove volatile
constituents from physically and
chemically different hazardous
waste streams and to estimate
volatile removal efficiency.
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3. Calculate preliminary economics,
using an example case, for each
pretreatment unit operation.
Reasonably detailed data on stream
composition and physical properties
are required to evaluate pretreatment
technology for removing volatile con-
stituents. Available compilations of haz-
ardous and potentially hazardous waste
stream composition and generation
rate information were evaluated to find
the one most suitable for this study. The
Waste Environmental Treatment (WET)
Model* was judged to have the most
pertinent information for an engineer-
ing assessment of this type. It is also the
most comprehensive, and, in spite of
some limitations (e.g., volatile con-
stituents are not identified for some
streams, and waste streams can vary in
composition), the WET Model data were
useful for assessing potential pretreat-
ment techniques.
A thorough screening of current tech-
nology was conducted to determine
which pretreatment techniques could
be used for volatile constituent re-
moval/recovery. Twelve engineering
techniques were selected:
Steam stripping
Chemical oxidation
Liquid phase carbon adsorption
Liquid phase resin adsorption
Air stripping/adsorption
Evaporation/adsorption
Biological treatment
Ozonation/radiolysis
Distillation
Wet oxidation
Solvent extraction
Physical separation
Techniques that are used primarily for
ultimate destruction, such as incinera-
tion and pyrolysis, were excluded. The
individual compatibility of each of these
techniques with the 72 WET Model
waste streams that contained volatiles
was evaluated.
For each pretreatment technique,
there is a set of hazardous waste stream
characteristics (or criteria) that deter-
mine if the technique is applicable to
that stream. (For example, one criterion
for using liquid phase carbon adsorp-
tion pretreatment to remove volatiles is
that the waste stream in contact with
the adsorbent must not contain exces-
sive concentrations of metallic ions or
solids.) Using such criteria, an appropri-
*The 1983 version of the WET model was used in
this study. The model is being updated and ex-
panded.
ate WET Model stream was selected for
each treatment technique and a detailed
example was prepared to show how
pretreatment might be used. In addi-
tion, an economic analysis was per-
formed for each technique on one waste
stream to obtain preliminary unit cost
estimates.
Example CaseLiquid Phase
Carbon Adsorption
As an example of the analysis of each
of the 12 treatment techniques, sum-
mary of the applicability of liquid phase
carbon adsorption to waste treatment
for volatile removal is presented here.
The adsorption of organic com-
pounds from both liquid and gaseous
phases onto activated carbon is a ma-
ture process technology with wide-
spread use as an integral unit operation
in such industrial manufacturing proc-
esses as corn syrup and pharmaceuti-
cals production and sugar refining, in
industrial and municipal wastewater
treatment, in drinking water purifica-
tion, in the separation and recovery of
organic compounds from vapor
streams, and in pollution control of at-
mospheric emissions. Although acti-
vated carbon has been and continues to
be the dominant adsorbent used, other
adsorbents such as resin or polymeric
materials and zeolite molecular sieves
have found increasing use for a number
of special applications in recent years.
Process Description
The liquid phase activated carbon ad-
sorption process involves two basic
steps as shown in Figure 1. In Step 1
(adsorption), the waste stream contacts
the carbon, which selectively adsorbs
the hazardous material(s) and allows
the purified stream to pass through.
Step 2 (disposition of contaminated or
spent carbon) represents a number of
process options. When the carbon
reaches its maximum capacity or when
the effluent is unacceptable for dis-
charge, the carbon is removed from the
adsorber for disposal, destruction, or
regeneration as established by the op-
tion selected under Step 2. In some
cases, the carbon can be regenerated in
such a way that the adsorbate is recov-
ered. This may be important in pretreat-
ment of hazardous wastes because the
recovered volatile material may have
some economic value (e.g., as a sol-
vent).
Process Operation
The technical suitability of a waste
stream for carbon adsorption pretreat
ment depends mainly on its physics
form and the type and relative concen
tration of constituents. However, othe
factors that affect the treatment eco
nomics often dictate which streams an
actually feasible for carbon treatment
such factors include the required de
gree of solute removal, waste through
put rate, and carbon utilization.
The following characteristics may b
used as guidelines to identify wast
streams that are likely candidates fo
carbon treatment:
Aqueous waste streams with oi
ganic solute concentrations the
are less than 15 percent, althoug
in practice the most concentrate
influent to be treated contains les
than 10,000 ppm total organic cai
bon.
Waste streams in which the aggrf
gate concentration of high moleci
lar weight nonvolatile organics i
substantially lower than the cor
centration of the volatile organics
Waste streams in which suspende
solids are less than 50 ppm if th
stream is not prefiltered and les
than 2.5 percent if prefiltered.
Waste streams in which oil an
grease concentrations are lesstha
10 ppm.
Waste streams in which the coi
centration of dissolved inorganic
is low (less than 100 ppm), unles
waste stream preconditioning an
spent carbon washing before rea
tivation operations are included.
The removal efficiency of carbo
treatment can be controlled to pracl
cally any level through the design of tr
carbon contractor. Typical carbon trea
ment efficiencies are better than 99 pe
cent with influent concentrations belo
1,000 ppm. At higher influent concei
trations, removal efficiencies can e
ceed 99.99 percent removal to yield
fluent concentrations at several ppr
As with most alternative treatmei
processes, carbon treatment remov
efficiencies must be compared to caf
tal and operating costs which increa:
dramatically as efficiencies approac
100 percent.
Process Economics
Several variables and/or alternative
in the design and operation of a carbt
treatment system can have a major ir
pact on the economics of the proces
These factors include:
type of carbon (GAC or PAC),
flow rate,
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Hazardous
Waste Stream
Carbon
Purified
Waste Stream
Disposal
Regeneration with Destruction
of Hazardous Waste, e.g..
Thermal Reactivation
Contaminated
Carbon
Regenerated with Reclamation
of Hazardous Material
Figure 1. Steps in carbon adsorption.
contact time,
process configuration (series, par-
allel, or moving bed)
number of stages, and
flow direction (packed or ex-
panded; upflow or downflow).
Wet Model Example
Waste stream 02.02.14 from the WET
Model was selected as an example to
show a typical carbon adsorption sys-
tem design, associated material bal-
ances, and treatment economics.
Possible
Pollution of
Air,
Water & Land
Emissions of
CO2,Ash, Heat
and
Other Products
Regenerated
Adsorbent
for Recycle
Reclaimed
Hazardous
Material for
Recycle
Regenerated
Adsorbent
for Recycle
This stream, with a nominal rate of
426,000 kg/day (17,750 kg/h, based on
365 day/yr operation) contains benzene,
toluene, and phenol at concentrations
ranging from 3,000 to 5,000 ppm. Al-
though these concentrations are on the
upper range of the concentrations cur-
rently being treated in commercial prac-
tice, GAC has been effective for these
constituents at these levels. The compo-
sition of WET stream 02.02.14 is given in
Table 1.
The major process uncertainties in
the design of this carbon adsorption
Table 1. Composition of Wet Stream
02.02.14, Quench Slowdown
from Ethylene Production by
Thermal Cracking of Heavy
Liquids
Component
Benzene
Phenol
Toluene
Solids
Water
Mass
fraction
0.005
0.003
0.004
0.010
0.980
Flow rate,
kg/h
88.8
53.3
71.0
177.5
17,359.5
Total 1.002
17,750.1
system are: (1) the equilibrium capacity
of the carbon for the three organics in a
multicomponent aqueous solution of
this particular composition, (2) the ad-
sorber residence (retention) time, and
(3) the carbon recirculation rate. For this
case, a carbon loading of 0.3 kg adsorb-
ate/kg carbon and a minimum adsorber
residence time of 30 min. was assumed.
Also, to size the reactivation furnace, a
furnace residence time of 30 min. was
assumed. These assumptions are con-
sistent with the ranges used in current
practice.
The capital and operating costs for
the above example case were based on
24 h/day, 330 day/yr operation, an ad-
sorber design capacity of 200,000 gal/
day (126 percent of waste stream rate
including recycle streams to the ad-
sorber), and reactivation furnace
throughput rate of 25,500 kg carbon/
day. The capital costs of the major com-
ponents of the carbon treatment system
including support equipment, installa-
tion, engineering, legal, financing, and
administrative costs are presented in
Table 2.
The annual operating costs for the
system are also included in Table 2. The
major operating costs include: labor,
electricity, fuel (natural gas), mainte-
nance materials, and carbon makeup.
Advantages and Disadvantages
The major advantages of carbon pre-
treatment are:
It is a mature technology in com-
mercial use for waste treatment ap-
plications.
Carbon adsorption can handle a
broad range of organic con-
stituents and concentrations.
The disadvantages of carbon pre-
treatment include:
Carbon adsorption treatment, es-
pecially with thermal reactivation,
is a complex and labor-intensive
operation.
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Table 2. Capital and Operating Costs for Carbon Adsorption Pretreatment With Thermal
Reactivation of the Carbon for WET Model Stream 02.02.14
Capital Costs
Influent pump station 21,000
Carbon adsorption system (2 pulsed-bed contactors) 181,000
Carbon regeneration system (fluidized-bed furnace) 1,925,000
Carbon inventory (150,000 Ib (w $0.85/lb) 128,000
Construction costs8 925,000
Total Installed Cost $3,180,000
Annualized Operating Cost
Operating labor (36,000 man-hours fc> $15/m-h) 540,000
Maintenance (5% of capital cost) 159,000
Electricity (824,000 kWh (a) $0.05/kWh) 41,200
Steam (13,680,000 Ib @ $4/1,000 Ib) 54,700
Fuel (1,430,000 therms (& $0.59/therm) 840,000
Water (20,800,000 gal (& $0.40/1,000 gal) 8,300
Carbon makeup (829,000 Ib (a) $0.85/lb) 704,700
Taxes, insurance, administration (4% of capital cost) 127,200
Capital recovery (16.3%; 10% over 10 years) 518,300
Total Operating Costs $2,993,400
Product Recovery Credit 0
Net Operating Costs $2,993,400
Waste treated (kg/yr) 155,490,000
Total volatiles removed (kg/yr) 1,865,880
Unit treatment cost ($/kg waste treated) 0.019 $/kg
($/kg volatiles removed) 1.60 $/kg
"Construction fee (10%), contingency (15%), engineering (15%), startup (1%).
Carbon adsorption has substantial
operating costs.
Study Findings
Table 3 shows the results of the anal-
ysis of other types of pretreatment proc-
esses. Applicable pretreatment proc-
esses are shown for some typical waste
types that may contain volatile con-
stituents. This table shows that air strip-
ping or evaporation (coupled with car-
bon adsorption of the off gases), steam
stripping, and distillation are the most
widely applicable techniques for
volatile removal.
The full report draws conclusions
based on engineering judgment regard-
ing the most applicable pretreatment
technique(s) for all streams covered in
the preliminary version of the WET
Model. In the final report for this project
a matrix is presented that matches the
12 pretreatment techniques considered
which were studied with all 72 WET
Model streams that contain volatile con-
stituents. Based on this matrix, the fol-
lowing pretreatment techniques are
considered most applicable for remov-
ing volatile constituents from the WET
Model waste streams:
Air stripping or evaporation/carbon
adsorption
Table 3. Appropriate Pretreatment Proc-
ess by Waste Type
Applicable
Waste type pretreatment process(es)
Organic liquids Distillation
Aqueous, up to
20% organic
Aqueous, less
than 2%
organic
Sludge with
organics
Some sludge in
organic or
aqueous
stream
Steam stripping
Solvent extraction
Steam stripping
Carbon adsorption
Resin adsorption
Air stripping with car-
bon adsorption
Ozonation/radiolysis
Wet oxidation
Biological treatment
Air stripping with car-
bon adsorption
Evaporation with carbon
adsorption
Ozonation/radiolysis
Wet oxidation
Chemical oxidation
Evaporation with carbon
adsorption
Physical separation
Steam stripping
Batch distillation
A distinction can be made betweei
pretreatment processes that are appli
cable at the site of generation and proc
esses that could be used at a TSDF trts
accepts waste materials from a variet
of sources. At a commercial TSDF, th
waste streams are generally not segre
gated by source. Thus, pretreatmer
using carbon adsorption, steam strip
ping, or batch distillation, which has th
capability of handling a variety of wast
types, is likely to be most applicable i
such TSDFs. Streams treated at th
point of generation are likely to be mor
uniform in composition and flow. I
such situations, continuous distillatior
solvent extraction or biodegradatio
may be applicable.
Insofar as the hazardous wast
streams analyzed in this summary ar
typical of the application of each pn
treatment technique, the reporte
volatile removal efficiency (kg volatil
removed/kg volatile in the stream), un
cost ($/kg stream treated), and cos
effectiveness ($/kg of volatile remove<
are typical of what may be expected
the pretreatment technique were use
on other streams of a similar natur
The cost-effectiveness of pretreatin
specific waste streams ranged from $E
to over $1800/mg volatiles removed.
Conclusions
This project is a preliminary enginee
ing assessment of various pretreatme
techniques for the removal of volati
compounds from hazardous was
streams identified in one data base. Tf
conclusions and analyses herein a
preliminary; at the time of this study I
tie data were available on hazardoi
waste stream treatment and many
the conclusions are based on other i
dustrial applications of the 12 prc
esses. However, this study does provi<
insight into the potential applicability
pretreatment to reduce emissions
volatile compounds from TSDFs.
The conclusions of this investigati
are:
Pretreatment of these hazardo
waste streams could remove m<
(90 to 99 percent) of the volatile rt
terials. A number of alternati
processes are available for p
treatment for most of the wa:
streams.
The cost-effectiveness of pretre
ing specific waste streai
varies greatly. The actual co
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effectiveness depends on the
chemical and physical characteris-
tics of the waste stream(s), the de-
sign capacity of the pretreatment
system, and the degree of volatile
removal required.
Pretreatment techniques using car-
bon adsorption, steam stripping, or
batch distillation are the most ap-
plicable ones for the waste streams
evaluated. This judgment consid-
ers cost, the range of applicability,
and the extent to which the technol-
ogy has been demonstrated.
James J. Spivey, C. Clark Allen, Robert L Stallings. David A. Green, and John P.
Wood are with Research Triangle Institute, Research Triangle Park, NC 27709;
and the EPA author, Benjamin L. Blaney (also the EPA Project Officer, see
below), is with Hazardous Waste Engineering Research Laboratory, Cincinnati,
OH 45268.
The complete report, entitled "Preliminary Assessment of Hazardous Waste
Pretreatment as an Air Pollution Control Technique," (Order No. PB 86-172
095/AS; Cost: $22.95, 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:
Hazardous Waste Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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