United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S7-86/047 Apr. 1987
&EPA Project Summary
Toxic Organic Emissions from
Synfuels and Related Industrial
Wastewater Treatment Systems
Fritzi A. Scheffel and Frank J. Castaldi
The study examined the potential for
toxic organic emissions from synfuels
wastewater treatment systems. The
synthetic fuels facilities examined were
coal gasification, direct and indirect coal
liquefaction, shale oil, by-product coke,
and associated petrochemical products.
A literature survey was performed to
assess the fate of organic priority pol-
lutants during wastewater treatment.
Pollutants in the volatile, base-neutral,
and acid-extractable fractions were
examined in order to assess their po-
tential for volatilization during waste-
water treatment. Compounds found to
contribute organic emissions during
wastewater storage and treatment were
in the volatile fraction (e.g., benzene,
toluene) and the base-neutral fraction
(e.g., polynuclear aromatic hydrocar-
bons). Acid extractables (e.g., phenol)
also present in synfuels wastewaters
are rarely stripped or volatilized from
wastewater stored in impoundments or
during activated sludge treatment.
However, phenol will be stripped from
wastewaters that are applied to evap-
orative cooling towers as makeup water.
This Project Summary was developed
by EPA's Air and Energy Engineering Re-
search Laboratory, Research Triangle
Park, NC, 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 In-
formation at back).
Introduction
Air emissions from industrial waste-
water treatment processes pose a poten-
tial environmental concern where these
emissions cannot be effectively controlled.
Volatilization of organic compounds from
surface impoundments is one source of
concern. It is also possible that aeration
during activated sludge processes may
cause air stripping of volatile organics
and increase emissions to the atmosphere.
At this time, the fate of toxic organics in
industrial wastewater handling and treat-
ment processes is uncertain. Their fate
during and after wastewater treatment
must be measured accurately before
assessing the need for emission control.
Therefore, there is a need to compile
available information that establishes the
magnitude of the problem.
The purpose of this study is to assemble
data from the literature on the fate of
toxic organics during aerobic wastewater
treatment. Data on the competitive inter-
actions between biodegradation, air strip-
ping, vaporization, and bioaccumulation
in waste sludge are also included. The
emphasis is on synfuels facilities such as
coal gasification, direct and indirect
liquefaction, and shale oil which may
produce liquid fuels and petrochemicals.
Summary and Conclusions
Coal gasification, direct and indirect
coal liquefaction, shale oil, by-product
coke, and associated petrochemical pro-
ducts all produce wastewaters which
contain organic priority pollutants. Little
actual data are available as to the exact
nature of the organics and their con-
centrations, since many of these pro-
cesses are still being developed or the
data are considered proprietary. The
wastewater treatment processes which
will be used in future commercial-scale
facilities are also uncertain at this time.
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The literature was surveyed to assess
the actual fate of organic priority pol-
lutants during wastewater treatment. The
results reveal that little information is
available at present with which to define
the magnitude of this problem. Although
it has long been believed that the reduc-
tion in effluent concentration of organics
is due to biodegradation, some pollutants
may also be adsorbed onto sludge, vola-
tilized, or forcibly stripped during treat-
ment. Several studies have attempted to
assess their fate; however, progress has
been slow toward resolving questions
concerning the fate of pollutants during
wastewater treatment. Some researchers
have also attempted to develop theoretical
models to predict the fate of the organics;
however, results to date have been in-
conclusive. The ability to predict fates
and resultant concentrations in the dif-
ferent phases (i.e., solid, liquid, gas)
present in wastewater treatment applica-
tions is doubtful without a concerted ef-
fort to develop an experimental program
that will accurately track pollutant fate
during treatment so that the models can
be verified with test data.
Most of the models available estimate
only the maximum emissions of certain
compounds. They also do not take into
consideration the competition between
air stripping, biodegradation, and ac-
cumulation in sludge. The accuracy of
the estimations is unknown for, in many
cases, no data are available with which
to compare the predictions. Some labora-
tory studies have been performed with
synthetic wastes in an attempt to experi-
mentally determine the fate of organics.
However, the few compounds studied
were present in concentrations lower than
those which are usually found in high-
strength industrial wastes This may lend
error to the analysis, since a compound
may bioaccumulate in systems containing
high pollutant concentrations but be en-
tirely biodegraded in systems with lower
concentrations
No one removal mechanism may be
examined by itself without causing in-
accuracies in experimental data. For
example, if air stripping is the only process
considered, the estimated air emissions
may be higher than the actual, since
some compounds (e.g., methylene chlo-
ride) are also preferentially biodegraded
at low concentrations This lends error to
the predicted fate of the compound.
Based on the data found through the
literature survey, many EPA priority pol-
lutants may present a hazard due to
volatilization and air stripping during
wastewater treatment. Most of the volatile
fraction pollutants (e.g., EPA 624) and
several of the base-neutral fraction pol-
lutants, particularly simple halogenated
compounds, exhibit significant removal
by air stripping. Several PCB and pesticide
compounds such as toxaphene and beta-
BHC also show potential for volatilization
during treatment. Acid extractables, on
the other hand, are rarely stripped or
volatilized from wastewater stored in
impoundments or during activated sludge
treatment. However, studies with solvent-
extracted fixed-bed-gasifier quench
liquors have indicated that phenol will be
air stripped from wastewaters that are
applied to evaporative cooling towers as
makeup water. It appears that most of
the compounds which may be air stripped
have Henry's Law constants greater than
103atm mVmole.
Of the compounds and groups listed
above, several are suspected to be pres-
ent in wastewater from the synthetic
fuels industries of interest. These are
benzene, ethylbenzene, toluene, pheno-
lics, and certain polynuclear aromatic
hydrocarbons. It should be noted that the
presence of some of these compounds is
suspected but not confirmed analytically.
It is more likely that the volatile fraction
(EPA 624) compounds will result from
the upgrade of synthetic fuels to more
conventional sources of energy (e.g.,
gasoline, kerosene). Halogenated priority
pollutants are not expected to be found in
wastes from these industries, since
halogenation is not a reaction used in
production of alternate fuels. However,
they do result from the production of
petrochemicals using conventional petro-
leum feedstocks.
Wastewater purification processes
which may release air pollutants during
treatment are equalization facilities and
activated sludge processes which use
surface impoundments for storage and
treatment of aqueous wastes. Since the
petroleum industry uses both of these in
treating its wastewater, it is likely that
both tar producing and non-tar producing
coal gasification facilities will also use
them.
Secondary treatment (i.e., activated
sludge) processes will probably not be
common in the oil shale industry because
the wastewaters are likely to be used to
quench and moisten the processed shale.
However, the presence of volatile organics
might preclude the use of wastewaters
for this purpose, since any vaporized
water and organics would directly enter
the atmosphere. It should be noted that,
at this time, wastewater data for the oil
shale industry are based on computer
models, laboratory experiments, and m
pilot-plant information. Neither the pre-
sence of volatile organics nor the use of
equalization basins or activated sludge in
wastewater treatment/management has
been confirmed.
The magnitude of the problem con-
cerning air emissions from wastewater
treatment processes is unknown. Labora-
tory and bench-scale studies of the fate
of pollutants in industrial wastewaters
are not available. Analysis of wastewater
streams from the industries of concern is
also needed before the problem and the
need for control strategies can be
assessed.
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F. Scheffel andF. Castaldi are with Radian Corporation, Austin, TX 78766.
William J. Rhodes is the EPA Project Officer (see below).
The complete report, entitled "Toxic Organic Emissions from Synfuels and
Related Industrial Wastewater Treatment Systems," (Order No. PB 87-140
356; Cost: $13.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, V'A 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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Official Business
Penalty for Private Use $300
EPA/600/S7-86/047
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