United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-86/095 Feb. 1 987
&EPA Project Summary
Technical Resource Document
Treatment Technologies for
Solvent Containing Wastes
Marc Breton, Mark Arienti, Paul Frillici,
Michael Kravett, Steven Palmer,
Andrew Shayer, and Norman Surprenant
The full Technical Resource Document
for Treatment Technologies for Solvent
Containing Wastes compiles available in-
formation on those technologies. It is
intended to provide support for the land
disposal prohibition, currently being con-
sidered by the EPA, and to provide tech-
nical information for those individuals and
organizations concerned with the subject
waste streams.
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).
Background
Solvents are low molecular weight or-
ganic compounds that are widely used by
all segments of American society. As a
result of their widespread usage and their
mobility within the environment, their
presence is frequently detected in all me-
dia, including ground water. To combat the
potential negative effects of solvent con-
tamination, the 1984 amendments to the
Resource Conservation and Recovery Act
(RCRA) directed EPA to ban certain sol-
vent wastes from land disposal to the ex-
tent required to protect human health and
the environment. The ban is effective 8
November 1986, two years after the en-
actment of the amendments.
EPA has taken steps to meet this dead-
line by evaluating the availability and tech-
nological capability of land disposal alter-
natives. As a result of this evaluation, a
2-year national variance was proposed for
wastewaters, solvent contaminated soils,
and inorganic sludges and solids contain-
ing less than 10,000 ppm of organic con-
stituents. The variance was based on a
determination by EPA that the available
capacity of alternative treatment technol-
ogies capable of achieving high destruc-
tion or removal efficiencies (i.e., low ppm
range) for these wastes will be insufficient
to accommodate the quantities managed
in land disposal units.
The categories of wastes subject to the
8 November 1986 land disposal restric-
tions are identified in the 14 January 1986
Federal Register1. They include organic
wastes characterized as RCRA waste
codes F001 through F005 and commercial
chemical products, manufacturing inter-
mediates and spill residues containing
solvents identified in these codes (i.e.,
priority solvents of concern). Land disposal
restrictions for other RCRA wastes will be
developed and implemented at later dates.
Scope
This summary of the Solvents Technical
Resource Document provides information
that can be used by environmental regula-
tory agencies and others as a source of
technical information describing waste
management options for solvents and
other wastes containing low molecular
weight organic compounds. These options
include waste minimization (i.e., source
reduction, reuse, recycling), treatment and
disposal of waste streams. Although em-
phasis is placed on the collection and
interpretation of performance data for
proven technologies, the full range of
waste minimization processes and treat-
ment/recovery technologies that can be
used to manage solvent wastes is dis-
cussed (see Table 1).
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Table 1. Waste Management Alternatives to Land Disposal
Applicable
Waste management objective waste typetsl
Potential waste
management alternative
Waste Minimization
Source Reduction
Recycling
Pretreatment
All
All
Liquid with solids
Liquid - Two Phase
Sludge
Bulky Solids
Low Btu/High Viscosity Blending
Raw material substitution
Product reformulation
Reclamation
Process redesign
Waste segregation
Reuse /e.g., as a fuel or process solvent)
Screening
Floatation
Decanting
Distillation
Vacuum filtration
Shredders
Sedimentation
Settling
Floatation
Filter press
tiammermills
Filtration
Centrifugation
Centrifugation
Centrifugation
Crushers
Distillation
Extraction
Other dewatering
Treatment
Physical
Chemical
Liquid
Liquid
Distillation
Steam stripping
Wet air oxidation
Evaporation
Air stripping
Fractional/on
Carbon adsorption
Supercritical water oxidation
Other chemical oxidations
Biological
Incineration
Other Thermal
Post Treatment
Liquid
All
All
Organic Liquid
Solid/Sludge
Aqueous Liquid
Activated sludge
Liquid injection
Pyrolysis processes
Plasma systems
Decanting
Solidification
Carbon adsorption
Ozonation
Aerated lagoon
Rotary kiln
Molten glass
Electric reactor
Dehydrating
Encapsulation
Resin adsorption
Other oxidations
Chlorinolysis
Trickling filter
Fluidized-bed
Circulating fluid bed
Molten salt
Fractionation
Thermal destruction
Air stripping
Extraction
Resin adsorption
Ozonation
Dechlorination
Starved air
Thermal destruction
Biological Treatment
In general, treatment process selection
will be limited to wastes possessing spe-
cific chemical, physical and flow charact-
eristics. Applicable technologies for
wastes with varying ranges in initial sol-
vent concentration are provided in Figure
1. A summary of overall performance, ap-
plicable waste streams, residuals genera-
tion and status of development for the
primary solvent waste treatment pro-
cesses is provided in Table 2.
Determination of the overall applicability
of these technologies for treating spent
solvents requires an understanding of the
nature of solvent wastes and current
waste management practices. Thus, the
range and variability in data requirements
include solvent waste physical, chemical,
and flow (i.e., rate, periodicity) character-
istics which, in turn, necessitates an
understanding of solvent waste industrial
origins. An analysis of current waste
management practices serves to identify
available methods which have proven to
be both technologically and economically
capable of treating solvent wastes. To a
significant extent, waste management
alternatives which will permit industry to
meet EPA disposal requirements have
already been implemented. This occurred
Chemical Oxidation
Dryi
H
Thin Film Evaporation
Fractional Distillation
Steam Stripping
Incineration
Solvent Extraction
Air Stripping
Resin Adsorption
Carbon Adsorption
Ozone/ 'UV Radiation
Legend Wet Air
Potential Extension
i i i i i i i 1 1 i i i i i i 1 1 1 i
Oxidation
Supercritical Water
i i i i i i 1 1 i i i i i i 1 1
0.01
Figure 1.
0.05 0.1
0.5 1.0
Initial % Organics
10
50 IOC
Approximate ranges of applicability oftreatment techniques as a function of organic
concentration in liquid waste streams.
Source: References 1 and 11.
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Table 2. Summary of Solvent Treatment Processes
Process Applicable waste streams
Incineration
Liquid injection
incineration
Rotary kiln
incineration
Fluidized bed
incineration
Fixed/multiple
hearths
Use as a Fuel
Industrial kilns
High temperature
industrial boilers
All pumpable liquids
provided wastes can be
blended to Btu level of
85OO Btu/lb. Some solids
removal may be necessary
to avoid plugging nozzles.
All wastes provided Btu
level is maintained.
Liquids or nonbulky
solids.
Can handle a wide
variety of wastes.
Generally all wastes.
but Btu level, chlorine
content, and other
impurity content may
require blending to
control charge
characteristics and
product quality.
All pumpable fluids, but
should blend halogenated
organics. Solids removal
particularly important to
ensure stable burner
operation.
Stage of development
Estimated that over 219
units are in use. Most
widely used incineration
technology.
Over 40 units in service;
most versatile for waste
destruction.
Nine units reportedly in
operation-circulating bed
units under development.
Approximately 70 units
in use. Old technology
for municipal waste
combustion.
Only a few units now
burning hazardous waste.
Several units in use.
Performance
Excellent destruction
efficiency f>99.99%).
Blending can avoid
problems associated
with residuals, e.g., HCI.
Excellent destruction
efficiency f>99.99%).
Excellent destruction
efficiency 099.99% ).
Performance may be
marginal for hazardous
wastes, particularly
halogenated wastes.
Usually excellent
destruction efficiency
O99.99%) because of
long residence times and
high temperatures.
Most units tested have
demonstrated high ORE
O99.99%).
Residuals generated
TSP, possibly some PICs,
and HCI if halogenated
organics are fired. Only
minor ash if solids removed
in pretreatment processes.
Requires APCDs. Residuals
should be acceptable if
charged properly.
As above.
As above.
Requires APCDs. Residuals
should be acceptable.
Waste must be blended to
meet emission standards for
TSP and HCI unless boilers
equipped with APCDs.
Other Thermal Technologies
Circulating bed Liquids or nonbulky
combustor solids.
Molten glass
incineration
Molten salt
destruction
Furnace pyrolysis
units
Plasma arc
pyrolysis
Fluid wall advanced
electric reactor
Almost all wastes,
provided moisture and
metal impurity levels
are within limitations.
Not suitable for high
(>20%) ash content
wastes.
Most designs suitable
for all wastes.
Present design suitable
only for liquids.
Suitable for all wastes
if solids pretreated to
ensure free flow.
Only one U.S. manufac-
turer. No units treating
hazardous waste.
Technology developed for
glass manufacturing. Not
available yet as a
hazardous waste unit.
Technology under develop-
ment since 1969, but
further development on
hold.
One pyrolysis unit RCRA
permitted. Certain designs
available commercially.
Commercial design
appears imminent, with
future modifications
planned for treatment
of sludges and solids.
Ready for commercial
development. Test unit
permitted under RCRA.
Manufacturer reports
high efficiencies
O99.99%).
No performance data
available, but DREs
should be high
O99.99%).
Very high destruction
efficiencies for organics
(six nines for PCBs)
Very high destruction
efficiencies possible
f>99.99%). Possibility
of PIC formation.
Efficiencies exceeded
six nines in tests with
solvents.
Efficiencies have
exceeded six nines.
Bed material additives can
reduce HCI emissions.
Residuals should be
acceptable.
Will need APC device for
HCI and possibly PICs;
solids retained
(encapsulated) in molten
glass.
Needs some APC devices to
collect material not retained
in salt. Ash disposal may be
a problem.
TSP emissions lower than
those from conventional will
need APC devices for HCI.
Certain wastes may produce
an unacceptable tarry
residual.
Requires APC devices for
HCPand TSP, needs flare for
H2and CO destruction.
Requires APC devices for
TSP and HCI; Chlorine
removal may be required.
-------
Table 2. (Continued)
Process
Applicable waste streams Stage of development
Performance
Residuals generated
In situ Technique for treating
vitrification contaminated soils, could
possibly be extended to
slurries. Also use as
solidification process.
Physical Treatment Methods
Distillation This is a process used
to recover and separate
solvents. Fractional
distillation will require
solids removal to avoid
plugging columns.
Evaporation Agitated thin film units
can tolerate higher levels
of so/ids and higher
viscosities than other
types of stills.
Steam Stripping A simple distillation
process to remove volatile
organics from aqueous
solutions. Preferred for
low concentrations and
solvents with low
solubilities.
Air Stripping
Liquid-Liquid
Extraction
Carbon Adsorption
Resin Adsorption
Generally used to treat
low concentration
aqueous streams.
Generally suitable only
for liquids of low solid
content.
Suitable for low solid,
low concentration
aqueous waste streams.
Suitable for low solid
waste streams. Consider
for recovery of valuable
solvent.
Chemical Treatment Processes
Wet air oxidation
Supercritical
water oxidation
Ozonation
Other chemical
oxidation
processes
Suitable for aqueous
liquids, also possible
for slurries. Solvent
concentrations up to 15%.
For liquids and slurries
containing optimal
concentrations of about
10% solvent.
Oxidation with ozone
(possibly assisted by
[UV])suitableforlow
solid, dilute aqueous
solutions.
Oxidizing agents may be
highly reactive for
specific constituents
in aqueous solution.
Not commercial, further
work planned.
No date available, but
DREs of over six nines
reported.
Technology well developed
and equipment available
from many suppliers;
widely practiced
technology.
Technology is well
developed and equipment
is available from several
suppliers; widely oracticed
technology.
Technology well developed
and available.
Technology well developed
and available.
Technology well developed
for industrial processing.
Separation depends upon
reflux (99+ percent
achievable). This is a
recovery process.
This is a solvent recovery
process. Typical recovery
of 60 to 70 percent.
Not generally considered
a final treatment, but
can achieve low residual
solvent levels.
Not generally considered
a final treatment, but may
be effective for highly
volatile wastes.
Can achieve high
efficiency separations
for certain solvent/waste
combinations.
Technology we/I developed; Can achieve low levels
used as polishing of residual solvent in
treatment. effluent.
Technology well developed
in industry for special
resin/solvent combinations.
Applicability to waste
streams not demonstrated.
High temperature/pressure
technology, widely used
as pretreatment for
municipal sludges, only
one manufacturer.
Supercritical conditions
may impose demands on
system reliability.
Commercially available
in 1987.
Now used as a polishing
step for wastewaters.
Oxidation technology
well developed for
cyanides and other
species (phenols),
not yet established
for general utility.
Can achieve low levels of
residual solvent in
effluent.
Pretreatment for
biological treatment.
Some compounds resist
oxidation.
Supercritical conditions
achieve high destruction
efficiencies f>99.99%)
for all constituents.
Not likely to achieve
residual solvent levels
in the low ppm range
for most wastes.
Not likely to achieve
residual solvent levels
in the low ppm range
for most wastes.
Off gas system needed to
control emissions to air. Ash
contained in vitrified soil.
Bottoms will usually contain
levels of solvent in excess of
1,000 ppm; condensate may
require further treatment.
Bottoms will contain
appreciable solvent.
Generally suitable for
incineration.
Aqueous treated stream will
probably require polishing.
Further concentration of
overhead steam generally
required.
Air emissions may require
treatment.
Solvent solubility in aqueous
phase should be monitored.
Adsorbate must be
processed during
regeneration. Spent carbon
and wastewater may also
need treatment.
Adsorbate must be
processed during
regeneration.
Some residues likely which
need further treatment.
Residuals not likely to be a
problem. Halogens can be
neutralized in process.
Residual contamination
likely; will require additional
processing of off gases.
Residual contamination
likely; will require additional
processing.
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Table 2. (Continued)
Process
Applicable waste streams Stage of development
Performance
Residuals generated
Chlorinolysis
Dechlorination
Suitable for any liquid
chlorinated wastes.
Dry soils and solids.
Biological Treatment Methods
Aerobic technology
suitable for dilute
wastes although some
constituents will
be resistant.
Process produces a
product te.g., carbon
tetrachloride). Not
likely to be available.
Not fully developed.
Conventional treatments
have been used for years.
Not available.
Destruction efficiency
of over 99% reported
for dioxin.
May be used as final
treatment for specific
wastes, may be pretreat-
ment for resistant species.
Air and wastewater
emissions were estimated as
not significant.
Residual contamination
seems likely.
Residual contamination
likely; will usually require
additional processing.
in response to increased regulatory re-
quirements and the improved economic
viability of solvent waste minimization and
treatment options. The latter resulted from
increased disposal costs, liability, and
technological developments.
Solvent waste generation, characteris-
tics and management practices are briefly
summarized below. This is followed by a
discussion of potential waste manage-
ment methods, including source reduction
and recycling, which are applicable to sol-
vent wastes (see Table 1). Emphasis is
placed on identifying treatment process
design and operating factors and waste
characteristics which affect treatment/
recovery of solvent wastes. This discus-
sion concludes with a summary of tech-
nical and economic factors which should
be considered in the selection of an
optimal waste management system.
Solvent Waste Generation,
Characteristics and Management
Practices
Of the more than 8 billion gallons of
organic solvent compounds consumed an-
nually, approximately 60 percent consists
of priority solvents which may ultimately
be affected by the upcoming land disposal
restrictions. Of this, 64 percent are non-
halogenated solvents. These are widely
used in the paint and allied products indus-
try as ingredients and wash solvents and
in general industry applications as cold
cleaners. The remainder are halogenated
compounds which are primarily used as
vapor degreasers, cold cleaners, and dry
cleaning solvents.
Hazardous solvent wastes are generated
at a rate of 4 to 8 billion gallons annually,
the majority of which are dilute, solvent
contaminated aqueous wastes. However,
the bulk of waste solvent constituents are
found in non-aqueous streams; is., greater
than 1 percent total organics. Of these,
roughly 1.5 billion gallons are managed in
RCRA treatment, storage, and disposal fa-
cilities with 60 percent being recycled.
Although there are some exceptions,
nonaqueous solvent waste generation and
recycling tend to parallel solvent consump-
tion. This occurs because solvents are
used in nonconsumptive applications and
are recycled (onsite or offsite) to approxi-
mately the same extent. On average, low
cost solvents typically result in larger
volume waste streams (e.g., wash sol-
vents) which provides comparable eco-
nomic incentives (e.g., high disposal cost,
economies of scale) to recover relative to
more expensive solvents; e.g., chlorinated
degreasing solvents. In addition, nonhalo-
genated waste solvents and treatment re-
siduals find widespread use as fuel supple-
ments relative to halogenated compounds.
Organic liquids comprise the vast major-
ity of currently recycled waste solvents
with aqueous, solid, and sludge wastes
contributing little to total recycled quan-
tity. Landfills are used as the primary
management method for a disproportion-
ately high fraction of solids, sludges,
halogenated, and low volume solvent
wastes. Conversely, large volume, liquid,
and nonhalogenated solvents have a
higher tendency to be treated via other
methods; e.g., tanks and wastewater
technologies.
Although over one-third of currently
landfilled solvents wastes contain over 10
percent solvent, these wastes tend to be
low volume streams which generators
could not justify reusing or recycling.
However, higher disposal costs, recent
technological developments (e.g., low
cost, high recovery package distillation
systems), technology transfer, and
increased availability of offsite manage-
ment alternatives (e.g., solvent reclaimers,
waste exchanges) have resulted in a
corresponding increase in solvent
recylcing.
This trend in recycling should be acceler-
ated upon implementation of the land dis-
posal restrictions since recycling and other
forms of waste minimization will become
the next lowest cost alternative for man-
aging many solvent wastes. In the short
term, use of evaporation technologies
which yield high solvent recoveries will
reduce overall solvent quantity requiring
land disposal but probably result in the
generation of more solvent solids and
sludges (less than 10,000 ppm solvent).
These wastes and aqueous streams will
be subject to a two year extension of the
land disposal ban as noted previously. In
that period, implementation of waste mini-
mization efforts should decrease net vol-
ume of solvent waste requiring disposal
and create a shift in the distribution of
these waste from aqueous to sludge/solid
physical form.
EPA feels that alternative treatment ca-
pacity for solvent wastes will be available
under the proposed disposal ban schedule.
This determination was based on esti-
mates of current waste quantities dis-
posed, small quantity generator disposal
requirements, projected residuals gener-
ated as a result of increased use of recov-
ery technologies and available treatment
capacity. Capacity shortfalls should not
occur as a result of the conservative
assumptions used in EPA's analysis regard-
ing available treatment capacity. EPA as-
sumed that only available offsite incinera-
tion and wastewater treatment would be
available as land disposal alternatives due
to lack of data on other options. Specifi-
cally, data gaps include available onsite
capacity, impact of waste minimization,
availability of emerging treatment process-
-------
es capable of yielding high removal effi-
ciencies, and uncertainties surrounding
the future regulation of hazardous waste
use as a fuel. EPA was not able to consider
these in its analysis despite the fact that
they will result in both lower demand and
increased available treatment capacity.
Waste Minimization
Waste minimization alternatives consist
of two basic approaches, source reduction
and recycling. Individual case studies of
waste minimization programs have been
extensively documented, which show net
cost savings and rapid payback periods on
equipment purchases for both large and
small waste generators. For example, over
a period of 3 years, IBM reported a waste
reduction of 234 million pounds of solvent
wastes at five plants which resulted in a
net cost savings of 120 million dollars. Due
to the site specific nature of these applica-
tions, it is difficult to estimate the national
impact of future activities on overall waste
generation. Waste minimization programs
are likely to significantly decrease solvents
currently land disposed. To date, these pro-
grams have been more commonly applied
to solvent wastes relative to other hazar-
dous wastes primarily as a result of
favorable economics.
Source reduction represents a preven-
tive approach to hazardous waste man-
agement which can be accomplished
through raw material substitution, product
reformulation, process modifications, or
waste segregation. Recycling can either
take the form of direct reuse in a process
which tolerates lower solvent quality
specifications or involves some form of
reclamation prior to reuse. Considerations
for both source reduction and recycling in-
clude impacts on product quality, process
performance, and net cost savings relative
to the use of virgin products and other
waste management options.
Primary recycling methods currently in
use include some form of distillation or
evaporation, decanting filtration, and less
commonly, fractionation and steam strip-
ping. Extraction and adsorption processes
are less frequently used to recover RCRA
solvent wastes. The majority of priority
solvents are recycled as a reclaiment while
ignitable wastes are primarily used as fuel
supplements. Other recycling methods in-
clude direct reuse as a feedstock. Halo-
genated solvents are finding increased use
as cement kiln and iron blast furnace fuel
supplements with small amounts being
used as an extender in the manufacture
of concrete blocks and asphalt.
Pretreatment
The purpose of pretreatment is to
remove restrictive waste characteristics to
simplify or reduce costs of subsequent
treatment. Most pretreatment methods in-
volve physical separation of different
phases or chemical species or modifica-
tion of the waste physical form. Common-
ly applied pretreatment methods have
been summarized in Table 1 for various
waste types.
Physical Treatment Processes
Physical treatment processes are the
most commonly applied methods used to
treat solvent wastes. Highly concentrated
organics (i.e., greater than 10 percent sol-
vent) are generally treated through some
from of distillation/evaporation. Steam
stripping is used for insoluble organic
species and fractionation used for sepa-
rating mixtures or recovering high purity
products. Steam stripping can also be
used, along with solvent extraction and
resin adsorption, for aqueous wastes with
organic solvent levels below 10 percent.
Air stripping and carbon adsorption are
only economically applied to wastes with
solvent concentration at 1 percent or less.
Pretreatment requirements include vary-
ing degrees of solids, oil, grease, metals,
and nonhazardous organic contaminant
removal to prevent fouling of heat or mass
transfer surfaces. Waste constituents
which are generally most difficult to
separate via physical mechanisms include
those which are highly soluble (e.g.,
alcohols) and those which have low vola-
tility relative to the bulk of the waste
stream; e.g., nitrobenzene or cresol con-
taminated wastewater. Under favorable
conditions, adsorption and stripping proc-
esses are capable of yielding residual prod-
ucts which can be discharged without
requiring additional treatment.
Distillation/evaporation processes are
the most widely applied technologies for
recovering concentrated organic wastes.
Separation efficiencies of well over 90 per-
cent have been reported. However, re-
moval is limited due to constraints im-
posed by vapor liquid equilibrium (e.g.,
azeotrope formation, low differential vapor
pressure), restrictive waste characteristics
(e.g., presence of contaminants that foul
heat transfer or packing surfaces, low
thermal decomposition and autoignition
temperatures, high viscosity), and eco-
nomics; e.g., high residence time, capital
cost and operating temperature and low
pressure requirements. With conventional
equipment, bottoms must be kept in a
pumpable state which often represents
the most limiting factor in solvent
recovery.
Fractionation is used for separating mix-
tures of volatile organics from waste
streams containing minimal solids content.
It is frequently applied as a post treatment
purification step. The other extreme in high
volume processing equipment is agitated
thin film evaporators. These units can han-
dle wastes with viscosities up to one
million centipoises and have been eco-
nomical in processing wastes with as lit-
tle as 6 to 8 percent recoverable solvent.
These units are widely applied by commer-
cial solvent reclaimers due to their high
potential recoveries and minimal pretreat-
ment requirements. Removal efficiencies
are maximized in these units as a result ol
their capability of processing high viscos
ity wastes in turbulent conditions. This
minimizes the adverse effect of mass
transfer resistance on volatilization rate
and enables residual solvent levels to be
reduced below 100 ppm under favorable
conditions.
Recent technological innovations ir
distillation/evaporation equipment include
development of semi-batch, low volume
package systems which permit process
ing to solid or sludge bottoms products
Use of these and other solids handlinc
equipment (e.g., drum dryer, jacketec
heating vessel with mechanical driver tc
maintain waste flow) result in maximurr
solvent recovery and minimum volume o'
waste requiring subsequent disposal
Alternatively, mixing distilling liquids with
nonvolatile carrier fluids (e.g., waste oil
allows for higher recovery efficiency while
maintaining pumpable bottoms. These
techniques and equipment are currently
applied primarily to halogenated solvem
wastes to minimize disposal/blending
costs but will find widespread use for al
solvents when land disposal is no longei
a viable management option.
Steam stripping is most effectively ap
plied in aqueous solutions (less than 1(
percent solvent) for the removal of volatili
components (boiling point less thai
150°C, Henry's law constant greater thai
10~4 atm-m3/mole) that are only slight!'
soluble in water (less than 1000 ppm). I
can also be used for stripping organic solu
tions when water forms low boiling azeo
tropes with the compounds to be removei
and does not adversely affect overhead o
bottoms quality. Steam stripping is wideh
applied to separate halogenated and cet
tain aromatics from water, but is less ef
fective for stripping miscible organics sucl
as ketones or alcohols. Since there are n<
-------
heat transfer surfaces and bottoms remain
fluid, steam stripping can tolerate higher
contaminant quantities relative to conven-
tional distillation. Under ideal conditions,
bottoms products may not require addi-
tional treatment.
In general, steam stripping is more cost
effective than air stripping for waste with
appreciable solvent content; i.e., greater
than 1 percent. Air stripping has only
found significant commercial application
in treating solvent contaminated water
supplies with concentrations of a few
parts per million or less. The technology
has demonstrated high removal efficien-
cies for volatile organics and, thus, may
find increased use as a polishing treatment
step; e.g., for compounds resistant to
biodegradation or exhibiting low adsorp-
tion characteristics.
Liquid-liquid extraction is not a com-
monly used treatment method but it has
potential for treating aqueous wastes
which are not readily treated through more
conventional methods. Extraction can be
attractive in cases where the solutes are
present at high enough concentrations to
prohibit use of adsorption, are toxic to
biological organisms, and when steam
stripping is less effective as a result of low
solute volatility or formation of azeo-
tropes. Extraction is most cost effective
when solutes are in the 1 to 10 percent
concentration range. Costs can be high as
a result of solvent regeneration require-
ments and post treatment costs associ-
ated with removal of residual solvent from
the treated aqueous stream.
Carbon and resin adsorption can be
used for treating dilute aqueous wastes to
levels which permit discharge as a nonhaz-
ardous waste. Carbon adsorption is a
widely applied technology for effluent
polishing. It can be used to treat wastes
with up to 5000 ppm organics and 100O
ppm inorganics. However, it is more typi-
cally used for wastes with less than 1000
ppm organics due to high regeneration
costs (thermal regeneration is typically re-
quired). Activated carbon is most effective
in removing nonpolar, low solubility (less
than 0.1mg/ml), high molecular weight
(greater than 100) compounds. Pretreat-
ment to remove oil and grease (less than
10mg/l), suspended solids (10 to 70 mg/l
depending on carbon treatment flow con-
figuration) and nonhazardous organics
(biological pretreatment) which compete
for adsorption sites or clog macropores
minimizes required regeneration frequency.
Powdered activated carbon is frequently
used in conjunction with biological treat-
ment. The carbon acts as a buffer to mini-
mize the adverse effects of high or variable
concentrations of toxic compounds.
Resins are significantly more expensive
than natural carbon base materials; how-
ever, they offer improved processing capa-
bilities. Resins can be manufactured to
have higher polarity and more controlled
pore size distributions and are conse-
quently capable of achieving higher re-
moval efficiencies for certain compounds.
They are more easily regenerated through
extraction processes which extends their
capability for treating wastes with higher
initial solvent concentration (up to 5 per-
cent). This is especially desirable if recov-
ery of solvent is economically feasible.
Finally, adsorption and extraction proc-
esses are also used as a polishing step for
dehydrating solvent streams such as
decanted overhead products from distill-
ation or steam stripping. Drying methods
which are currently in use include caustic
extraction and molecular sieve, calcium
chloride and ionic resin adsorption.
Chemical Treatment Processes
Chemical treatment methods for solvent
wastes include oxidation, chlorinolysis,
and dechlorination processes. The most
important of these processes is oxidation.
Of particular interest is the supercritical
water oxidation (SWO) process developed
by MODAR, Inc. The first commercial SWO
unit is now being designed to treat up to
30,000 gallons of aqueous waste per day
with installation scheduled for late 1987.
Although the characteristics of the aque-
ous waste have not been made public at
this time, a solvent concentration of about
10 percent is reported to be thermally opti-
mal for the process. On the basis of re-
ported test data, the destruction and re-
moval efficiency (ORE) is anticipated to be
at the six nines level for all halogenated
and nonhalogenated solvent constituents.
In addition to high ORE, another feature
of the SWO process is its applicability to
the treatment of halogenated organics.
Hydrochloric acid formed as a result of ox-
idation of chlorinated compounds can be
neutralized within the system by prior ad-
dition of caustic to the feed stream. The
chloride salts formed (and other inorganic
salts) are essentially insoluble in water at
super critical conditions and are removed
from the process stream by a separator
which is an integral part of the SWO sys-
tem design. Ultimately, the applicability of
SWO to the treatment of solvent wastes in
aqueous streams will depend on the eco-
nomics of the process. The economics in
turn, will depend upon the ability of the
process equipment to withstand stringent
supercritical temperature and pressure re-
quirements which are in excess of 374 °C
and 218 atmospheres.
The wet air oxidation (WAO) process,
which operates at subcritical and therefore
less stringent temperature and pressure
conditions (e.g., less than 320 °C and 200
atmospheres), may also have some appli-
cation for the treatment of solvent wastes
in aqueous media. However, the DREs will
not be as high as those achieved by the
SWO process. This is particularly true for
chlorinated aromatics such as chloroben-
zene which are highly resistant to oxida-
tion under WAO conditions. In addition,
low molecular weight residuals which re-
sist further degradation, such as acetic
acid and formic acid are commonly re-
ported as byproducts of aqueous solvent
wastes treated by the WAO process.
The WAO process is an established
technology for the treatment of municipal
sludges. It has also found application for
the treatment of a limited number of speci-
fic waste streams, including aceylonitrile
and coke oven gas scrubbing waste-
waters. While the WAO process may also
find utility for the treatment of other
specific waste streams, it may prove to be
most useful as a pretreatment for solvent
waste streams which are too dilute to in-
cinerate and yet too toxic to biotreat.
Available data indicate that solvent
streams that are resistant to biological
treatment can generally be detoxified by
the WAO process to allow subsequent ef-
fective biological degradation.
Other chemical oxidation processes that
have been used for the degradation of sol-
vent wastes operate at ambient or only
moderately elevated conditions of temper-
ature and pressure. Primary oxidation
agents include ozone, hydrogen peroxide,
and potassium permanganate. These oxi-
dants have found application as polishing
agents for dilute organic contaminated
wastewater or as oxidants for specific
organics (e.g., aldehydes and phenols) in
industrial waste streams. However, their
applicability to solvent waste streams ap-
pears to be limited. Process residuals are
usually found which will often require
additional treatment to produce an envi-
ronmentally acceptable discharge stream.
Further, the indiscriminate nature of the
oxidation process limits its application to
the treatment of hazardous aqueous
water. Cost And. in some cases, the need
for stringent process control measures,
become prohibitive if organic slurries and
slurries are to be treated.
There is some evidence to indicate that
the efficiency and completeness of oxida-
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tion is enhanced by UV photolysis. How-
ever, the evidence is limited and the sen-
sitivity of photolysis to the presence of im-
purities in the process stream is an issue
of concern.
The chlorinolysis and dechlorination
processes do not appear to have general
application for the treatment of solvent
wastes. Chlorinolysis is a pyrolysis process
conducted in the presence of chlorine to
produce low molecular weight chlorinated
compounds (e.g., carbon tetrachloride)
using chlorine bearing wastes from
sources such as the pesticide industry.
The process has not yet been utilized in
the United States. It requires high levels
of capital expenditure and is economically
dependent upon the return available from
the sale of the chlorinated hydrocarbon
product. It is unlikely that the process will
become available in the foreseeable future.
The dechlorination processes examined
are experimental processes that are being
developed primarily for the treatment of
highly toxic dioxin compounds. Although
they are capable of achieving high solvent
DREs, the alkali metal based reactants
used in these processes are expensive and
highly reactive. Other technologies appear
to be more suitable.
Biological Treatment
Despite the almost universal use of cost
effective, biological methods for the treat-
ment of wastes, very little information
could be found describing DREs for the
constituents in solvent-bearing wastes.
Data are available for aerobic systems
showing discharge concentrations for
many solvents that are below the ppm
level. However, these data are based on in-
fluent levels that, while sufficient to
demonstrate significant DREs, are not high
enough to exhibit appreciable inhibitory
biological effects. Some degree of pre-
treatment through technologies such as
WAO, carbon adsorption, or solvent ex-
traction will be required for many wastes
containing high levels of organic com-
pounds, particularly the more biotoxic
halogenated compounds. As noted, addi-
tion of powdered activated carbon to acti-
vated sludge has proven effective in
mitigating the inhibitory activity of solvent
constituents to biological activity.
Thermal Destruction Technologies
The thermal destruction of organic sol-
vent wastes has been the subject of EPA
research for several years. DREs in excess
of the 99.99 percent requirement for incin-
erators have been well documented for
most solvents of concern present in var-
ious types of waste. Documentation is par-
ticularly extensive for the halogenated
compounds considered most difficult to
thermally destroy. Incineration techniques
that represent proven technology include
liquid injection; fixed hearth, including
those using starved-air designs rotary
kilns, and fluidized-bed incineration. The
incineration of many solvent wastes will
require air pollution control devices to
achieve the incinerator requirements of:
• At least 99 percent removal of
hydrogen chloride from the exhaust
gas if hydrogen chloride emissions
are greater than 4lb/hour; and
• Particulate emissions not exceeding
0.08 grains/dry standard cubic feet,
corrected to 7 percent oxygen in the
stack gas.
In 1981, prior to the promulgation of the
1982 incinerator standards, over half of
the operating incinerators were not equip-
ped with air pollution control systems for
either particulates or acid gases. Although
the present status of control device appli-
cation at incinerators is now being assess-
ed by EPA, it is possible to comply with
the incinerator standards by restricting
waste feed streams to those low ash, non-
halogenated wastes for which control
measures will not be necessary.
Because of the broad applicability of
thermal destruction to solvent wastes and
the added demands for alternatives to land
disposal resulting from the 1984 RCRA
amendments, a number of emerging ther-
mal technologies are in various stages of
development. Several pyrolysis processes,
molten glass and molten salt technologies,
circulating bed combustion and the in situ
vitrification processes are among the more
prominent. Pyrolysis processes are partic-
ularly well advanced with two processes,
a furnace design manufactured by the
Midland-Ross Corporation and the Huber
advanced electric reactor now operating
under RCRA permit status. A third proc-
ess, under development by Pyrolysis
Systems, Inc. of Welland, Ontario, is now
undergoing intensive testing by EPA. All
of the pyrolysis units should meet DRE re-
quirements but will have to or already have
incorporated control systems for particu-
lates and acid gases.
The molten glass furnace is based on
technology long established in the glass
industry. Although no units are now oper-
ating commercially, two companies are
actively pursuing development. DREs of
99.99 + percent can be anticipated, al-
though interest in this process has also
focussed on its potential for containing
solid and inorganic residues within a sta-
ble, nonleachable glass matrix. The de-
struction principle is similar in concept tc
that of the Molten Salt Destruction Tech
nology. This latter technology, under devel-
opment by Rockwell since 1969, has
achieved greater than 99.9 percent DRE.
However, solid residues must be freed
from the salt matrix during regeneration
and may require further treatment. Al-
though three units (maximum capacity
2000lb/hour) have been built by Rockwell,
no commercial units have been sold. A1
the present time no further development
is planned by Rockwell.
The circulating bed combustor is an out-
growth of conventional fluidized bed com-
bustion technology. By using high veloci-
ties and a circulating bed, potential prob-
lems associated with maintaining the crit-
ical flow velocity needed for bed stability
are avoided. Turbulence is also increased,
which should enhance DRE (already dem-
onstrated to be in excess of 99.99 percent
for solvents). Addition of limestone to the
bed can effectively reduce hydrochloric
acid emissions from halogenated solvent
combustion. However, pollution control
systems will be required to meet the in-
cinerator standards for particulate
emissions.
The in situ vitrification process is de-
signed to treat contaminated soils rather
than process waste streams. Now under
development by Battelle Northwest, DREs
in excess of 99.99 percent have been
achieved in the laboratory for solvents. An
added feature of this technology is the en-
capsulation of solid wastes in a vitrified
matrix which is leach resistant and dur-
able. Work, some of it supported by the
Electric Power Research Institute, is con-
tinuing, with focus on PCB rather than sol-
vent, contaminated soils.
Use as a Fuel
Thermal destruction of solvents wastes
in industrial boilers and other high
temperature industrial processing equip-
ment (e.g., cement, lime, and aggregate
kilns) has been actively studied by EPA in
recent years. Performance data indicate
that most industrial boilers and process-
ing units can meet the incinerator DRE
standard of 99.99 percent for solvent con-
stituents. No difficulties were encountered
in meeting the 4lb/hour emission standard
for hydrogen chloride during the combus-
tion of nonhalogenated solvent wastes.
Also, no significant changes in particulate
emissions were observed that could be at-
tributed to the burning of waste fuels. The
particulate emission standard of 0.08
grains per dry standard cubic feet at 7 per-
cent oxygen can be met by a waste with
an ash content of about 0.3 percent. The
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exact value will depend upon the Btu value
of the fuel, its elemental composition, and
other factors. Blending of many low ash
content wastes with conventional fuel oils
prior to combustion could avoid the) need
to install costly pollution control devices
for many wastes.
Land Disposal of Residuals
Ash residues from thermal destruction
processes, including burning of wastes in
industrial boilers and process equipment,
appear to be acceptable for land disposal.
However, they and other treatment resid-
uals may be required to undergo solidifica-
tion or encapsulation prior to land disposal.
Present understanding of the interaction
of solvent containing wastes and residuals
with various solidification materials is
limited and long-term interactions can only
be inferred from short-term behavior.
Potential problems associated with the
disposal of process residuals is a major
factor in assessing alternatives to land
disposal.
Selection of Optimal Waste
Management Alternative
Waste management options have been
summarized previously in Table 1. These
include source reduction, recycling, use of
a treatment system or some combination
of these waste handling practices. Selec-
tion of the optimal management alter-
native will ultimately be a function of
regulatory compliance, economics, and
availability of onsite and offsite systems
and equipment. Economic considerations
include processing (including pretreatment
and post-treatment) and disposal costs.
value of recovered products, and potential
adverse effects on product quality or proc-
ess equipment resulting from waste min-
imization or reuse of recovered products.
Additional consideration in system selec-
tion must be given to factors such as safe-
ty, public and employee acceptance, liabili-
ty, and degree of uncertainty in cost esti-
mates and ability to meet treatment
objectives.
MarcBreton, MarkArienti, PaulFrillici, MichaelKravett, Steven Palmer, Andrew
Shayer, Clay Spears, and Norman Surprenant are with GCA Corporation,
Bedford. MA 01730.
Harry M. Freeman is the EPA Project Officer (see below).
The complete report, entitled "Technical Resource Document: Treatment
Technologies for Solvents Containing Wastes," (Order No. PB 87-129 821 /
AS; Cost: $54.95, 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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