United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-87/094 Jan. 1988
&EPA Project Summary
Case Studies of Hazardous
Waste Treatment to Remove
Volatile Organics
C. Allen, M. Branscome, C. Northeim, K. Leese, and S. Harkins
Three treatment processes were
investigated for the removal of volatile
organic (VO) compounds from hazard-
ous waste: thin-film evaporation,
steam stripping, and steam stripping
with carbon adsorption. The data
collected included the VO removal
effectiveness, air emissions from the
process, cost, and process limitations.
Pilot-scale tests of a thin-film evapo-
rator treating refinery sludges showed
that greater than 99 percent removal
of purgeable organics and over 10 to
75 percent of extractable organics
(depending on operating conditions)
could be obtained. Two full-scale
steam strippers treating aqueous
wastewaters containing about 6,000
ppm purgeable organics were tested.
Total VO removal efficiencies of 99.8
and 99.999 percent were obtained. At
a full-scale steam stripper/carbon
adsorption unit, 92 percent reduction
in extractable organics was obtained by
the stripper alone, while an overall
removal efficiency of greater than 99.6
percent was obtained by the stripper
followed by carbon adsorption.
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 doc-
umented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
The U.S. Environmental Protection
Agency (EPA) Office of Air Quality
Planning and Standards (OAQPS) is
developing regulations under the 1976
Resource Conservation and Recovery Act
(RCRA) and its 1984 amendments to
control air emissions from hazardous
waste treatment, storage, and disposal
facilities (TSOF). The purpose of the air
emissions regulations is to protect
human health and the environment from
emissions of volatile compounds and
particulate matter.
Sources of volatile organic (VO) emis-
sions include storage tanks, treatment
processes, surface lagoons, landfills,
land treatment, and drum storage and
handling facilities. Approximately 5,000
TSDF locations exist in the United States
where one or more of these activities is
in progress. Most of these sites are part
of industrial facilities, and the rest are
commercial facilities that accept wastes
from offsite.
Research has concentrated on the
characterization of uncontrolled emis-
sions from these sources by using field
measurements and by determining the
reliability of emission models. Recent
investigations have identified a number
of options for controlling VO emissions
from TSDF. These include restricting the
VO concentrations of wastes going to
sources where emission rates would be
high, i.e., the "pretreatment" of waste
to remove volatiles, and the use of in-
situ (i.e., add-on) control techniques at
the TSDF.
The purpose of the field tests reported
here was to collect data for the support
of regulations that consider waste
pretreatment as an alternative for the
control of volatile air emissions from
TSDF. To the extent possible, these data
were collected from processes that were
treating hazardous wastes or that were
treating wastes with physical character
istics similar to hazardous wastes in
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order to permit a comparison of pretreat-
ment to other emission controls. For the
purposes of these tests, the term "vol-
atile organic (VO)" includes those com-
pounds which can be identified in wastes
using separation via purging, or acid or
base/neutral extraction (e.g., EPA
Methods 624 and 625).
Field data collected on several waste
treatment techniques helped determine
(1} how efficiently they remove volatiles
from hazardous waste streams, (2) what
the removal costs are, (3) how the
byproducts from the pretreatment tech-
nologies are collected and disposed of,
and (4) what limitations (in terms of
waste types, volatile concentrations, etc.)
are placed on the use of such treatment
techniques.
Approach
The processes selected for evaluation
included a pilot-scale thin-film evapora-
tor used to treat refinery sludge, two
steam strippers used to remove purge-
able organic compounds from industrial
wastewater, and one steam stripper used
in combination with liquid-phase carbon
adsorption to remove semivolatile (i.e.,
extractable) organic compounds from
wastewater. Preliminary site visits were
conducted to observe and discuss the
process operation and to collect informa-
tion on process limitations, costs, oper-
ating conditions, and potential sampling
points.
Detailed sampling and analysis plans,
which also included the quality assur-
ance plan, were written for each site.
These plans provided details on the
proposed sampling and analytical
approaches, sampling points and number
of samples, and the quality assurance/
quality control (QA/QC) procedures and
goals. Liquid samples were collected at
the influent and effluent to each treat-
ment unit. Samples of process residuals,
such as sludge, recovered organics, and
air emissions, were also taken. Steam
stripper tests lasted for two days at each
site. The pilot-scale TFE test lasted for
four days.
The thin-film evaporator (TFE) study
was a pilot-scale evaluation of the TFE
for removal of VO from petroleum
refinery sludges. These sludges were
non-hazardous refinery wastes that were
chosen because they had physical prop-
erties (e.g., boiling point curves) similar
to API separator and DAF unit sludges
(which are listed hazardous wastes). The
study was performed at three tempera-
tures and three flow rates, and under
both vacuum and atmospheric pressure.
Two full-scale steam strippers used to
treat industrial wastewater containing
about 6,000 ppm of purgeable organics
were tested. The tray column stripper at
Plant H processes about 850 L/min of
water that contained primarily ethylene
dichloride and chloroform. The packed
column steam stripper at Plant I pro-
cessed about 42 L/min of water that
contained primarily methylene chloride
and chloroform. At Plant I, an upstream
decanter was used to remove solids and
organic phases from the waste stream.
This decanter was also sampled.
The steam stripping/carbon adsorp-
tion unit at Plant G was used to remove
semivolatiles from water, which con-
tained nitrobenzene, 2-nitrotoluene, and
4-nitrotoluene. The industrial waste-
water flow rate for this packed column
stripper was 500 L/min. The carbon
adsorption columns contained about
20,000 kg of carbon.
The data were analyzed to determine
the process removal efficiency for the
specific organic compounds found in the
waste. Removal efficiencies were calcu-
lated for each constituent and for total
VO. Measurements of vent flow rates and
vapor concentrations were used to
calculate or estimate air emissions from
the process. Process residuals were
characterized in terms of quantity and VO
content. In addition, cost data were
collected and evaluated to provide an
assessment of the total cost of the
process and the cost-effectiveness for
VO removal.
Summary of Findings
General Conclusions
Each of the processes investigated
successfully removed VO from the
wastes. The TFE removed over 99 per-
cent of the VO from petroleum refinery
sludge, the two chemical industry steam
strippers removed 99.8 to 99.999 per-
cent of the VO (purgeable organic
compounds) from the wastewater, and
the steam stripper/carbon adsorber
removed 99.6 percent of the VO (primar-
ily semivolatiles) from aqueous wastes.
The results are summarized in Tables 1,
2, and 3.
Table 1 shows that steam strippers can
reduce purgeable organics from 6,000
ppm to less than 9.8 ppm at Plant H or
to less than 37 ppb at Plant I. Semivol-
atiles may be reduced by steam stripping
from over 600 ppm to about 48 ppm as
shown in Table 2. Carbon adsorption of
these semivolatiles reduced concentra-
tions to below detection limits (<0.8
ppm). The TFE generally reduced volatile
compounds by over 99 percent. Semivol-
atiles such as naphthalene and methyl-
naphthalene were removed efficiently
(85-97 percent) at the higher tempera-
ture runs (Table 3).
The applicability of each of these
processes depends in part on the solids
content of the wastes. The TFE can
handle sludges that contain high-boiling
oils (17 to 25 percent oil) and solids (2
to 3 percent solids). The steam stripper
tests showed that solids may need to be
removed prior to steam stripping to 0.01
g/L (as done at Plant I) or the operator
may experience fouling and frequent
cleaning (as seen at Plant H with 1.4 g/
L). Solids removal prior to steam stripping
generates a sludge containing VO that
may be a troublesome disposal problem.
The various processes that generate
air emissions are preliminary treatment
tanks (e.g., solids decanters), feed and
storage tanks, condensate collection and
storage tanks, and process vents (e.g.,
condenser vents). Condenser efficiencies
for volatile organics ranged from 91
percent (cooling tower water at 21 °C) to
99 percent for a condenser cooled with
refrigerated glycol (2°C).
Thin-Film Evaporator (TFE)
Conclusions
TFEs are able to process nonhomog-
enous feed streams such as oily refinery
sludges. The major process limitations
are that the feed and bottoms product
must be pumpable and the feed should
not foam excessively during processing.
The TFE was found to have very high
removal efficiencies of VO compounds
from the waste sludges that were tested.
In each of the three methods used to
assess the reduction of volatiles, the
removal efficiencies for VO compounds
were greater than 99 percent. The
removal efficiency for VO was greatest
when the TFE was operated at the
highest temperature (320°C). VO remo-
val at this temperature generally
exceeded 99 percent, with no clear
trends relative to changes in feed rate.
The percent of semivolatiles removed
from the feed ranged from 10 to 75
depending on the TFE operating con-
ditions.
There were difficulties when the
system was operated at high tempera-
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Table 1 . Summary of Steam Stripper Performance for Purgeable
Compound In fppm) Out (ppm)
Plant H
1 ,2-Dichloroethane
Chloroform
1,1 -Dichloroethane
1 ,2-Dichloroethene
Vinyl Chloride
1 .1 ,2- Triochloroethane
Other Volatiles
Total
Plant 1
Methylene chloride
Chloroform
Carbon Tetrachloride
Chloromethane
Other volatiles
Total
5,630
271
11
8.9
8.4
75
14
5,950
4,490
1,270
55
33
11
5,860
Table 2. Summary of Steam Stripper and
(Plant G)
Nitrobenzene
Concentrations (ppm)
To stripper
From stripper
From adsorber
Percent reduction
Stripper
Adsorber
Overall
505
41
<0.8
92
>98
>99.8
0.097
9.6
<0.01
<0.01
<0.01
<001
<001
<9.8
0.011
0.006
<0.005
<0.005
<0.005
<0.037
Volatile Organics
Percent Reduction
99.998
96.5
>99.9
>99.9
>99.9
>99.9
>99.&
>99.8
99.999
99.999
>99.99
>99.98
>99.95
>99.999
Carbon Adsorber Performance for Semivolatiles
2-Nitrotoluene 4-Nitrotoluene Total
78
2.4
<0.8
97
>67
>98.9
51 634
4.4 48
<0.8 <2.4
91 92
>82 >95
>98.4 >99.6
ture (320°C) under vacuum, as some
carryover of feed into the condensate
was observed. The condensate from the
vacuum runs was a milky-white emul-
sion that would require additional treat-
ment to separate the oils.
The gas flow rates and total VO
emissions from the TFE condenser were
highly dependent on the waste being
processed. The first waste, an emulsion
tank sludge, showed only minimal (less
than 250 mL/min) flows from the con-
denser, and the second waste, oily tank
bottoms, showed much higher (0.75 to
10 L/min) vent gas flow rates. All of the
condenser vent gas concentrations were
greater than 10,000 ppm (reported as
hexane). The high VO concentrations in
the vent gas were due to the vapor
pressure of light hydrocarbons at the
cooling water temperatures. A glycol-
cooled condenser, a two-stage con-
denser (first stage cooling water, second
stage chilled glycol), an incinerator, or
some other appropriate control device
could be used to reduce these emissions.
The condenser and vent gas control
system should be designed specifically
for the waste to be treated because
different wastes may contain different
quantities of noncondensible or difficult-
to-condense compounds.
The approximate capital and operating
costs of TFEs when used to process
petroleum waste sludges using various
operational modes range from compar-
able to less than the cost of conventional
land treatment. The cost of TFE sludge
treatment was either $27.60, $40.60,
$97.40 or $128/Mg depending on the
mode of operation as compared to a cost
of $110/Mg for land treatment. The
process does not eliminate land treat-
ment and the cost analysis assumes that
the sludge from the TFE is disposed of
by land treatment.
Table 3. Summary of Thin-Film Evaporator Results for Two Temperatures
Compound
Toluene
2 - Met hy /naphthalene
Naphthalene
m-Xylene
o.p-Xylene
Benzene
Ethylbenzene
Styrene
In
2,800
790
765
280
280
230
180
160
Out'
5.8-6. 1
320-660
160-520
1 3-38
1.4-44
<0.01-1 0
0 7-2 1
08-25
Percent
Reduction
998
16-59
32-79
99-99.5
98-99.5
99 6->99.9
99-99 6
98-99 5
Outb
2.7-4.6
99-120
24-46
0.7-09
0.7-0.9
<001-06
04-06
1.2-1.6
Percent
Reduction
99.8-99.9
85-87
94-97
99.7-99.8
99.7-998
99.7 ->99. 9
99.7-99.8
99-99.3
a From Runs 5 and 7 at 1 50°C.
"From Huns 8 and 10 at 320°C
Plant I Stream Stripping
Conclusions
The steam stripper reduced the total
VO concentration by over five orders of
magnitude from a feed concentration of
roughly 6,000 ppm (0.6 percent) to less
than 0.037 ppm. The removal of total VO
was approximately 99.999 percent.
The primary condenser removed about
91 percent of the total VO in the vapors.
Efficiencies for individual constituents
ranged from 89 percent for chlorometh-
ane to 94 percent for chloroform. The
secondary vent condenser (with cooling
tower water) did not appear to provide
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measurable control or condensation of
VO. Theoretical calculations indicate that
using refrigerated glycol cooling on the
secondary condenser may improve its
control efficiency for total VO to 68
percent.
The major air emission sources for the
process are the solids decanters, storage
tank, and noncondensibles from the
steam stripper. Emissions were esti-
mated as 2.7 grams (g) per L of water
treated. For an average treatment rate
of 41.6 liters per minute (L/min) or 11
gallons per minute (gal/min) for 75
percent of the year, annual emissions are
estimated as 44 megagrams per year
(Mg/yr) or 1.4 grams per second (g/s).
These annual emission estimates
assume a constant feed concentration of
6,000 ppm.
The vapor flow rate from the primary
condenser when it was vented directly
to the atmosphere was measured as 57
L/min. The emissions were measured as
2.4 g/L of water treated or 39 Mg/yr
(1.2 g/s) for operation for 75 percent of
the year. When the primary condenser
was vented to the secondary condenser,
the flow rate from the secondary con-
denser was measured at 11 to 13 L/min
with an emission rate of 0.5 g/L of water
treated or 8.2 Mg/yr (0.26 g/s) for
operation for 75 percent of the year. The
difference in measured flow rates (57
versus 11 to 13 L/min) suggests that
some flow was not sampled because of
leaks in the overhead system, overflow
pipes, or tank vents. The estimates of
annual emissions are based on the
conditions during the test with an
average feed concentration of 6,000
ppm.
Plant H Steam Stripping
Conclusions
The steam stripper reduced the total
VO concentration by approximately three
orders of magnitude from a feed concen-
tration of roughly 6,000 ppm (0.6 per-
cent) to an average of 9.7 ppm. Removal
of the major constituent (1,2-
dichloroethane) consistently exceeded
99.99 percent.
The removal of all constituents was
consistently high except for chloroform.
The variations in chloroform removal
appear to be related to fouling from the
accumulation of solids. Suspended solids
concentrations in the stripper influent
were on the order of 0.1 percent.
The overhead condenser removed 99+
percent of the total VO in the overhead
vapors. The condenser efficiency was
much lower for specific individual com-
pounds present at low parts per million
levels in the stripper influent. The flow
rate from the condenser vent ranged
from 1.9 to 4.2 L/s (4.0 to 8.8 ftVmin).
The condenser vent on this steam
stripper was routed to an incinerator. A
similar system vented to the atmosphere
could emit 12 to 51 Mg/yr of VO.
The cost-effectiveness of the steam
stripping operation was approximately
$220/Mg of VO removed. Steam usage
for this steam stripper appeared to be
optimized because it was lower than
values observed for other steam strippers
and was also lower than values given
in design manuals.
The major operational problem expe-
rienced with this steam stripper is the
fouling of the heat exchanger and column
trays. Solids removal prior to the steam
stripper may provide a more consistent
operation. The results indicate that a
steam stripper can be operated for
wastewater containing 0.1 percent solids
if the operator is willing to backflush and
clean the system periodically. However,
if the solids are removed prior to steam
stripping, the resulting sludge may be a
troublesome disposal problem and an
additional source of VO. Consequently,
the company has chosen to incur the
additional cost of cleaning the existing
system periodically instead of installing
equipment for the removal, treatment,
and disposal of solids.
Plant G Steam Stripping/
Carbon Adsorption
Conclusions
Semivolatile organic compounds can
be removed from wastewater using
steam stripping and carbon adsorption.
Removal efficiencies of 92 percent were
observed for the steam stripper, and the
carbon adsorber removed more than 95
percent of the organics fed to it. The
removal efficiency of the combined
steam stripper-carbon adsorber was
greater than 99.6 percent.
Air emissions from the condenser vent
were very low, and the gas flow from
the vent could not be measured reliably.
Concentrations of VO in the vent stream
varied widely, with total VO (as ppm
hexane) between 10 and 2,000 ppm. The
maximum air emissions were estimated
to be 4.0 g/h.
Carbon was added to the adsorbers in
a pulse feed mode at an average of 1.5
times per day, with a carbon addition of
908 to 1,360 kg/charge. The carbon was
regenerated offsite and was the major
cost of the process. The organic concen-
trations of the wastewater fed to the
adsorber were relatively low (47.8 ppm),
and utilization of the carbon was corre-
spondingly low (0.021 kg organics
removed/kg carbon used). The total
annualized cost of the steam stripper-
carbon adsorption system was $14.30/
kg organics removed.
The high normalized operating costs of
the system resulted primarily from the
low feed concentrations (634 ppm organ-
ics) and the high removal efficiency
(>99.6 percent) of the steam stripper
carbon adsorber. On a water-processed
basis, the total annualized cost was
$0.0089/kg water treated (or 0.89 C/L).
Approximately 78 percent of the steam
used in the steam stripper was
condensed into the water being stripped,
and 22 percent was condensed with the
stripped organics. This condensation into
the stripped liquid produces a varying
gas/liquid (G/L) ratio within the column:
55 m3/m3 at the base and 24 mVm3 at
the top. The heat exchanger, used to heat
the feed with the bottoms from the
stripper column, reduced the steam
requirements for the column.
Principal variables influencing the
effectiveness of the process were the
feed rate and steam rate of the process.
Downtime of the process was reported
as less than 1 percent of operating time,
with heat exchanger fouling as the only
maintenance problem.
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C. Allen. M. Branscome, C. Northeim. K. Leese, andS. Harkinsare with Research
Triangle Institute, Research Triangle Park, NC 27709.
Benjamin L. Blaney is the EPA Project Officer (see below).
The complete report consists of two volumes, entitled "Case Studies of
Hazardous Waste Treatment to Remove Volatile Organics:"
"Volume I," (Order No. PB 88-125 893/AS; Cost: $19.95)
"Volume II." (Order No. PB 88-125 901/AS; Cost: $19.95)
The above reports will be available only from: (costs subject to change)
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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