United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-86/048 July 1986
Project Summary
Field Evaluation of Hazardous
Waste Pretreatment as an Air
Pollution Control Technique
C. C. Allen, S. Simpson, and G. Brant
Three types of commonly used com-
mercial treatment processes were invest-
igated for the removal of volatile organic
compounds (VOCs) from hazardous waste:
thin-film evaporation, steam stripping, and
distillation. These unit operations were
evaluated for their potential to control
emissions from hazardous waste treat-
ment, storage and disposal facilities
(TSDFs) by reducing waste VOC content.
One-day visits were conducted at three
sites which operate thin-film evaporators
to gather data on the types of waste that
can be treated, the treatment costs, and
the major emission points. Steam stripping
and distillation of six different wastes were
evaluated during 3-4 day site visits to two
recycling firms. Data collected on these
two processes permitted calculation of
unit cost-effectiveness and determination
of compound-specific stripping rate con-
stants for each batch. Air emission factors
were also estimated for these two
processes.
The full report also contains generic des-
criptions of thin-film evaporators and dis-
tillation processes. Typical unit designs,
operating modes, and estimates of unit
costs are included.
This Project Summary was developed
by EPA's Hazardous Waste Engineering
Research Laboratory, Cincinnati, OH, to
announce key findings of the research pro-
ject that is fully documented in a separate
report of the same title (see Project Report
ordering information at back).
Introduction
The EPA Office of Air Quality Planning
and Standards (OAQPS) is developing re-
gulations to control emissions from hazar-
dous waste treatment, storage, and dispo-
sal facilities (TSDFs). The purpose of the
OAQPS air emissions regulations is to pro-
tect human health and the environment
from emissions of volatile organic com-
pounds (VOCs) and particulates.
The Hazardous Waste Engineering Re-
search Laboratory (HWERL) is supporting
the OAQPS regulatory development pro-
grams by characterizing TSDF air emis-
sions and determining the effectiveness of
emissions control alternatives. This Sum-
mary describes the field assessment of
one control alternative: waste treatment
processes that could be used to remove
VOCs from wastes, thus reducing the po-
tential for later VOC emissions.
This Summary presents the results from
field studies of three treatment techni-
ques: thin-film evaporation, steam strip-
ping, and distillation. The processes in-
vestigated were located at waste recycl-
ing facilities.
The full report also contains sections
providing general descriptions of thin-film
evaporators and distillation units. These
sections are intended to supplement the
data gathered in the field assessment by
indicating other process design options
and associated costs. The reader is refer-
red to a recent EPA report1 for similar
descriptions of steam stripping processes.
Objectives
The overall objective of this study was
to determine the cost-effectiveness of
VOC removal from hazardous waste based
on field assessments of waste treatment
processes. The degree to which VOCs
could be removed from waste streams
was measured and the cost of removal
was estimated, in order to determine the
cost of treating waste either (1) to a
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specified percent VOC removal or (2) to
a specified level of VOC content. Cost-
effectiveness was calculated in terms of
both $/liter waste treated and $/mega-
gram ($/Mg) VOC removal. Since all pro-
cesses studied are used in other industries,
costs which are peculiar to hazardous
waste treatment were identified, along
with limitations on the types of waste
which a given process could treat. Final-
ly, the mass of residuals (e.g., air emis-
sions) produced by the process per unit
waste treated and per unit VOC removed
was determined.
Approach
In a previous investigation2, 11 com-
mercially available processes were con-
sidered for their potential in treating hazar-
dous wastes to remove VOCs. Four pro-
cesses were identified as being applicable
to a wide variety of wastes with VOC con-
centrations of 0.1 weight percent or above.
They are evaporation, steam stripping,
distillation, and air stripping.
The present study considered three
potentially applicable techniques from this
group: agitated thin-film evaporation, batch
direct-injection steam stripping, and batch
fractional distillation. Other techniques,
particularly air stripping, are being assessed
in another investigation.
One-day site visits were conducted at
five hazardous waste treatment and dis-
posal sites to collect engineering design
and operating information on the three
processes. Table 1 identifies the plants
which were visited and the treatment pro-
cesses which were studied. The types of
wastes which each technique was used
to treat were determined and residual
streams were identified. At the first four
sites, samples were obtained of (1) wastes
which were being treated and (2) air emis-
sions from the processes.
Return visits were made to two sites to
conduct 3-day sampling of the influent
and effluent waste streams and of the pro-
cess residuals. At one site. Plant D, mea-
surements were made during the process-
ing of four different batches of waste
through a direct-injection steam stripper
(500 gallon capacity). At the other site.
Plant B, measurements were made during
the processing of two different batches of
• waste through fractional distillation col-
umns of different sizes.
Waste samples were analyzed for gen-
eral composition (water, organic and solids
content; pH; and viscosity) and for their
VOC content (both total and individual or-
ganic compounds). A headspace analysis
for VOC was also performed on waste
samples. The treatment products and re-
sidual effluent streams were analyzed for
their VOC content. In addition, the total
and compound-specific concentrations of
gas samples of air emissions were analyz-
ed and emission flow rates were measured.
For each process, information was ob-
tained from plant operators on (1) special
maintenance requirements, (2) capital and
operating costs, and (3) limitations in the
types of wastes which could be treated.
In some cases, the field data were sup-
plemented by data obtained from process
vendors.
Process Effectiveness
Table 2 describes the waste streams
that were sampled at each process and in-
dicates the final VOC content of the treat-
ed stream, as well as the percent VOC
removal efficiency.
Thin-film evaporators are used in many
solvent recovery operations where the
waste contains solids. For streams which
are predominantly composed of high boil-
ers and solids, at least 80 percent of the
volatiles can typically be recovered. The
concentrations of volatiles in equilibrium
with the bottoms will therefore be
reduced.
However, if the waste being treated is
predominantly composed of low boiling
point liquids, gas phase equilibrium con-
centrations may not be significantly reduc-
ed. As a result, emissions rates from the
treated wastes may not be significantly
lower than from the untreated wastes, al-
though total emissions will be lower due
to lower volumes of waste being disposed.
Both direct-injection steam stripping and
fractional distillation will remove volatile
organic compounds from oils and waste
water to low levels «1%). Steam strippers
can operate at lower temperatures than
thin-film evaporators and are therefore
more appropriate for some reactive mater-
ials. The volatile organic compounds can
be recovered from the process by decan-
ting, if the organic phase separates from
the condensed steam.
Plant D stripped waste material by direct
injection of live steam into a waste batch.
The process of stripping continued until
the VOC recovery that the facility desired
was achieved. Four batchs of liquid wastes
were evaluated: (1) an aqueous xylene mix-
ture, (2) a chlorinated organic-oil mixture,
(3) a chlorinated organic-water mixture,
and (4) a mixed solvent-water mixture.
Table 1. Treatment Processes Studied
Plant Identifier Treatment Processes
A
B
C
D
£
Thin-Film Evaporator
Thin-Film Evaporator. Fractional Distillation
Thin-Film Evaporator
Direct-Injection Steam Stripper
Fractional Distillation
Table 2.
Process
Thin-Film
Evaporator
Waste Streams Studied and Observed Process
Plant Stream Composition
A
5% Chlorinated organ ics
95% Oil
Effectiveness
Final VOC
Content of
Treated Stream
(mg/LI
1,700
Percent
VOC
Removed
97
Direct-
Injection
Steam Stripping
B Alcohol, xylene and VOCs ND
C 83% VOCs 760,000
17% High boiling organics
and resins
D 26% Aromatics 498
74% Water
ND
8
99.8
Fractional
Distillation
74% Mixed VOCs
26% Oil
18% Chlorinated organics
82% Water
3% Mixed VOCs
97% Water
B 23% Acetone & VOCs
77% Water
5% MEK & VOCs
95% Water
1,400
12,000
385
<700
<600
99.8
93
99
99.6
98.8
ND = Not Determined.
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VOC removal efficiencies ranging from
93% to 99.8% were observed and it is ex-
pected that higher efficiencies could have
been obtained if the economics of waste
recycling had not dictated that stripping
be terminated when it was.
For all four waste streams, the concen-
trations of the volatile organic compounds
at equilibrium in the cooled waste (25°C)
were found to decrease as their concen-
trations decreased during treatment. The
waste material generally showed at least
an order of magnitude decrease in the
vapor concentrations at equilibrium with
the waste due to treatment.
The distillation system at Plant B differed
from the direct injection at Plant D in that
the capacity of Plant B is larger, the steam
heats the waste directly through coils, and
the stream of vapors is processed in a dis-
tillation column. Two different waste
streams were selected for the field evalua-
tion. Both were composed of VOCs in
water, consisting primarily of methyl ethyl
ketone (MEK) and acetone, respectively.
Total-VOC removal efficiencies of over
98% were obtained.
Process Costs
The full report provides example unit
treatment costs ($/L waste and $/Mg VOC
removed) for all three treatment systems.
These are based on cost information ob-
tained from vendors and/or facility opera-
tors. Costs were found to be strongly
dependent on a number of factors, in-
cluding system size and waste stream
composition. For example, the cost of VOC
removal from the four steam-stripped bat-
ches varied from $318/Mg ($0.14/lb) VOC
recovered to $9,472/Mg ($4.30/lb).
Sufficient data on waste treatment and
disposal costs and waste steam stripping
rate constants were obtained to perform
additional cost-effectiveness analyses on
the four batches which were steam strip-
ped. These analyses produced curves of
unit VOC removal costs as a function of
the percent VOC removed. Percent re-
moval ranged from 68 percent to 99.9 per-
cent. The analyses accounted for the fol-
lowing cost estimates which are specific
to the waste stream and/or treatment faci-
lity: waste condensate treatment, batch
cycle time, steam cost, waste collection
revenues, solvent sale credits, and treated
waste disposal costs (to landfill or munici-
pal waste water treatment). The results
show that, for a given waste stream, the
net cost or credit for VOC removal (assum-
ing that the VOC has a resale value) can
vary by as much as $12,000/Mg VOC re-
moved. The principal factor influencing the
net cost was the cost of disposal of the
treated waste.
Process Residuals
The significance of air emissions from
the treatment processes are of interest, as
well as the liquid and solid residuals which
they produce. The treatment would be of
little use if substantial quantities of VOC-
contaminated by-products were produced.
For the processes considered here, the
principal residuals are either organic mat-
erials (which could be incinerated) or aque-
ous streams with the VOCs removed. A
small amount of the VOCs were lost to the
atmosphere.
Air emissions were evaluated from the
three thin-film evaporators and two steam
strippers. At Plants A and B, the major air
emission source identified at the thin-film
evaporators was the vent from the vacuum
pump. The thin-film evaporator at Plant C
was operating at atmospheric pressure
and the concentrations of VOC in this pro-
cess were not significant.
The most significant vent emissions
from the direct injection steam stripping
unit and distillation units were the con-
denser vents. Emissions of 10 - 100 ng
VOC/g waste treated were observed. Emis-
sions of less than 10 mg/sec were esti-
mated to occur from closed roof storage
tanks associated with the steam stripping
process, but these emissions could not be
measured at the distillation units.
Conclusions
General Conclusions
1. Waste treatment is not practiced at
many TSDF sites for the purpose of
VOC control.
2. Based upon information obtained
from these field tests. Table 3 pre-
sents potential uses of three treat-
ment techniques for VOC removal.
All three techniques are applicable to
aqueous, as well as organic and mix-
ed aqueous/organic streams. How-
ever, their applicability is limited by
other waste characteristics shown in
the table.
3. The cost of waste treatment is sen-
sitive to the concentration of VOC in
the influent waste. For a fixed per-
cent of VOC removal, costs rise as
the initial VOC concentration de-
creases. For many wastes, the value
of the recovered VOCs is less than
the treatment costs.
4. Treatment of aqueous waste streams
for VOC removal can significantly de-
crease their disposal cost by making
them amenable to discharge to muni-
cipal sewers.
Thin-Film Evaporator Conclusions
1. Thin-film evaporators permit the re-
covery of VOCs from waste materials
containing sludges and tars. Thin-film
evaporators may not adequately pro-
cess wastes that are reactive (poly-
merize) or that contain large pieces of
solids. VOC removal efficiencies of 23
to 99.9% were observed.*
2. The overhead product from the thin-
film evaporator can be treated by distil-
lation, carbon adsorption, and other
separation or reaction processes ap-
plicable to liquids.
3. The major air emissions source from
the thin-film evaporator is the vacuum
pump vent. Under abnormal operations
(such as inadequate cooling in the con-
denser), the emissions could be signifi-
cant. For properly operated evapora-
tors, the air emissions from thin-film
evaporators are much less than the
VOCs recovered.
4. The degree of emissions reduction that
can be achieved with a thin-film evap-
orator is very dependent upon the rela-
tive volatilities of waste constituents.
In many cases emissions reductions are
just proportional to reduction in waste
volume; emission rates per unit volume
decrease little.
5. Costs of waste treatment using thin-
film evaporation ranged from $0.033 to
$0.37/L of VOC recovered.
Steam Stripping Conclusions
1. Steam stripping is effective for reduc-
ing the concentration of VOCs to levels
of 0.1 percent or lower. Removal effici-
encies of 99 to 99.8% were observed.
2. The amount of steam required to
remove the VOCs in waste materials is
greater than predicted from equilibrium
partitioning based on vapor pressures
and solubility in dilute aqueous
solutions.
3. The rate of volatile removal is loga-
rithmic in nature, with substantially
longer times required to remove the
VOCs present in wastes at lower con-
centrations than at higher
concentrations.
4. The air emissions from the steam strip-
ping process tested are much lower
than the amount of VOCs recovered
from the waste.
5. Costs of treatment ranged from $0.17
to $0.53/L VOC recovered for streams
* All processes tested were at recycling firms and the
extent of waste stream treatment was determined
by economic considerations, not technical constra-
ints. Therefore, VOC removal efficiencies reported
here are lower limits for the combinations of pro-
cesses and waste streams tested.
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that are typically recycled at the facility
visited, but were as high as $4.34/L for
streams of low «10%) VOC
concentration.
Distillation Conclusions
1. The individual VOC components can be
removed from the waste material by
batch distillation. Removal efficiencies
of 99% and greater were observed,
with resultant VOC concentrations
below 0.1%.
2. The removal rates of the components
are a function of the waste matrix and
the ratio of the rate of steam flow to
the batch size, and are generally pro-
portional to the VOC concentration in
the waste. In the distillation process
with reflux to the column, the more vo-
latile materials are removed first from
the waste.
3. In the two processes tested, air emis-
sions from the process vents repre-
sented only a relatively small fraction
(less than 0.2 percent) of the VOC
present.
4. Costs of treatment were typically in the
range of $0.20 to 0.70/L of VOC re-
covered, but were estimated to be as
high as $1.18/L for streams of low
«10%) VOC concentration.
References
1. Shukla, H.M., and R.E. Hicks. 1984.
Process Design Manual for Stripping of
Organics. U.S. Environmental Protec-
tion Agency, EPA-600/2-84-139.
2. Spivey, J.J., et al. 1984. Preliminary
Assessment of Hazardous Waste Pre-
treatment as an Air Pollution Control
Technique (Draft). U.S. Environmental
Protection Agency, Contract No.
68-03-3149. October 1984.
Table 3. Limitation of Technologies Due to Selected Waste Characteristics
Thin-film Batch steam
evaporation stripping
Distillation
Over 50% Water Content
Polymerizable waste
Presence of dissolved solids
Waste containing sludges and tars
Highly viscous waste
A
P
A
A
N
A
P
A
P
N
A
P
P
N
N
A Applicable technique.
P Potentially applicable.
N Not applicable.
C. Clark Allen is with Research Triangle Institute. Research Triangle Park, NC
27709; S. Simpson and G. Brant are with Associated Technologies, Inc.,
Charlotte. NC 28281.
Benjamin L. Blaney is the EPA Project Officer (see below).
The complete report, entitled "Field Evaluation of Hazardous Waste Pretreatment
as an Air Pollution Control Technique," (Order No. PB 86-183 076/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
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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EPA/600/S2-86/048
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