United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
^'f
Research and Development
EPA/600/S2-85/069 Jan. 1986
Project Summary
Evaluation  of  Emerging
Technologies  for  the
Destruction of Hazardous Wastes
Jan Radimsky and Arvind Shah
  The objective of the full report is to
provide detailed information regarding
four  innovative alternative technolo-
gies demonstration projects for treat-
ing and destroying hazardous wastes.
Under a cooperative agreement be-
tween the U.S. Environmental  Protec-
tion Agency (EPA) and the State of Cal-
ifornia, the Department of  Health
Services (DHS) carried out a pilot-scale
test program on the following promis-
ing technologies.
1. High Temperature   Thagard
    Fluid-Wall        Research
2. Evaluation of       Air Resources
    Emission Tests    Board  State
    from SunOhio    of California
    Mobile PCB
    Treatment Pro-
    cess
3. Wet Air Oxidation   Zimpro
4. Evaluation of       Air Resources
    Emission Tests    Board  State
    from Wet Air      of California
    Oxidation Zim-
    pro Process
  Discussions of the above processes
include project descriptions, results,
conclusions, and recommendations.
  This Project Summary was devel-
oped by EPA's Hazardous Waste Engi-
neering Research  Laboratory,  Cincin-
nati,  OH, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering infor-
mation at back).

Introduction
  On January 20,1981, the State of Cal-
ifornia entered into a cooperative agree-
ment with the  Office of Research and
Development, EPA, to evaluate selected
 promising technologies for destroying
 hazardous waste. The inclusion of a pro-
 cess in the report should in no way be
 considered an endorsement of the pro-
 cess by either the State of California or
 the EPA.

 High Temperature Fluid-Wall,
 Thagard Research Company

 Summary
  The  High Temperature Fluid-Wall
 (HTFW) Reactor was developed origi-
 nally for the continuous dissociation of
 methane into carbon fines and hydro-
 gen. This particular process required
 the generation of stable temperatures
 above  1,700°C and the prevention of
 precipitate formation on the reactor
 walls. This fact has particular relevance
 to the project herein.
  Reactor consists of a tubular core of
 porous refractory material capable of
 emitting sufficient radiant energy to ac-
 tivate the reactants fed into the tubular
 space.  The reactor has been built with
 cylindrical core diameters of 3", 6", and
 12" with heated core lengths of up to
'72". The core material is designed to be
 of uniform porosity to aJlow the perme-
 ating of a radiation-transparent gas
 through the core wall into the interior.
 The core is completely jacketed and in-
 sulated in a fluid-tight pressure vessel.
 Electrodes located in the annular space
 between jacket and core provide the en-
 ergy required to heat the core to radiant
 temperatures.
  To achieve both goals simultaneous-
 ly, the reacting stream is kept out of
 physical contact with the reactor wall by
 means of a gaseous blanket formed by
 flowing an  inert gas radially inward

-------
through the porous  reactor tube (or
core). Both high temperatures and high
rates of heat transfer are achieved by
heating the porous carbon core to in-
candescense so that  the predominant
mode of heat transfer is by radioactive
coupling from the core to the stream.
  Reactor is heated electrically with six
carbon resistance heaters.  Because of
the extreme temperatures encountered
in operation of the device, the insulation
package consists not of refractory brick
but of a radiation shield made of multi-
ple layers of graphite paper backed up
with  carbon felt.  The short residence
time  associated with the reactor which
demands  the  pulverization of solid
feeds also lends itself to a compact sys-
tem where a reasonably high through-
put is seen for  a small installation, and
portability becomes an attainable de-
sign feature.
  Four volatile chlorinated hydrocar-
bons [(dichloromethane;  1,1,1-
trichloroethane; carbon  tetrachloride;
and  Freon-12  (dichlorodifluorometh-
ane)]  and  one nonvolatile chlorinated
hydrocarbon (hexachlorobenzene) have
been decomposed in the HTFW Reactor
in bench-scale tests to assess the appli-
cability of the  device for efficient de-
struction  of these particular com-
pounds.
  The hexachlorobenzene, loaded onto
a solid radiatiorvtarget, exhibited high
(O9.9999  percent) destruction effi-
ciency, while the  vapors (which could
be heated only by secondary thermal
conduction from solid radiation target)
exhibited  destruction efficiencies re-
lated inversely to the compound heats
of formation,  indicating that vapor-
phase reaction  temperatures were
lower than  the solid reaction. Destruc-
tion efficiencies ranged from 99.999965
percent for dichioromethane to 84.99
percent for Freon-12. Heat transfer anal-
ysis indicated that vapor heating is de-
pendent on  the solid  particle density,
and that efficient  heating (and destruc-
tion) of vapors can be achieved simply
by increasing the particle density.


Results and Conclusions

Chlorinated Hydrocarbon
 Vapor Samples
  The most important conclusion
drawn from the work completed is that
chlorinated  hydrocarbons introduced
into  the reactor in the vapor form are
much more difficult to destroy than sim-
ilar materials loaded onto solids, given
identical residence times and reactor
temperatures.
  While the governing factor in the case
of the solids was the direct absorption
of radiation  by the solid surfaces and
consequent extremely rapid heating,
the governing factor in the case of the
vapors was the conduction of the heat
from  the particle surface into the
vapor—a much slower process limited
in rate by the thermal conductivity of
the vapor itself.

  Thus, as might be  anticipated, the
temperature levels achieved in the va-
pors for a given residence time will not,
in general,  be as high  as the tempera-
tures achieved on the solids. The exper-
imental result of this behavior will  be
that minimum temperatures and mini-
mum  residence times for complete de-
struction of the vapor-phase substances
will not be achieved, and that the ob-
served destruction levels will now  be
critically dependent on the heat of for-
mation of the substance being investi-
gated.
Chlorinated Hydrocarbons
Solid Sample

  The  results for hexachlorobenzene
(HCB) in soil are in agreement with HCB
results on carbon, thus duplicating both
the destruction and analytical methods
and further substantiating the  conclu-
sion that the  solids are rapidly heated
and the toxic material effectively de-
composed.
  Despite some data problems, the frac-
tion of HCB remaining on the solids and
in the effluent gases was approximately
10~6, corresponding to a destruction ef-
ficiency of approximately 99.9999  per-
cent.
  The  demonstration of gettering of
chlorine (from decomposition of HCB)
with calcined lime (CaO) mixed with the
soil produced no identifiable  results.
Since gettering of halogens and sulfur
with lime and  subsequent fixing into a
vitreous slag has been previously dem-
onstrated on numerous occasions with
other materials we must conclude  that
some  deficiency in the experimental
procedure was introduced  (inadequate
mixing of the lime in the soil, too low a
CaO/CI ratio for this particular applica-
tion, etc.). Subsequent experimental
work will seek to quantify this parame-
ter  which is an important system con-
sideration of on-site disposal.
Air Resources Board's (ARB)
Evaluation to Determine
Emissions from SUNOHIO's
Mobile PCB Treatment Process
  Three evaluation tests were  con-
ducted to allow determination of emis-
sions from SUNOHIO's  mobile PCB
treatment process. The mobile unit was
tested while treating contaminated oils
at three locations: Chevron's USA refin-
ery at  El Segundo, California;  Pacific
Gas and Electric (PG&E) Company's fa-
cility at Union City, California; and
Maxwell  Laboratory's facility  in San
Diego,  California.
  PCBs were not detected in samples of
emissions taken at two of the tests.
However, relatively high benzene and
aliphatic  hydrocarbon concentrations
were measured  in the units'  uncon-
trolled  exhaust gases. Measured con-
centrations ranged from 18 to 7,000
ppm for benzene and 700 to 2,700 ppm
for aliphatic hydrocarbons. Low process
volumetric  flow  rates resulted in the
mass emission rates for benzene and
the aliphatic hydrocarbons to values of
approximately 0.1 Ib/hr. and  below.
Data from samples taken by the South
Coast Air Quality Management  District
(SCAQMD) staff during the El Segundo
test indicate that dioxins and furans are
not present above the limit of detect-
ability.
  The efficiency of the carbon adsorp-
tion control system for preventing emis-
sions to the atmosphere of benzene and
aliphatic  hydrocarbons was found to
have varied from  approximately 99 to
30 percent, indicative  that carbon ad-
sorption breakthrough occurred. The 30
percent  efficiency calculation was
based  upon concentration measure-
ments from the evaluation test con-
ducted at the PG&E facility.
  An alternative control  system was
tested that utilized an oil fired furnace, a
component of the PCBX process, to in-
cinerate the emissions. Furnace exhaust
gas samples indicate a general reduc-
tion in concentration of compounds
measured across the furnace. Benzene
and toluene were  not detected in the
furnace exhaust gas.

Introduction
  On December 2 and 10, 1982 and No-
vember 30,1983, the ARB's Engineering
Evaluation  Branch conducted  evalua-
tion tests  on chemical processing
equipment  designed to reclaim trans-
former oils contaminated with PCBs.
The process  tested is known as the

-------
 "PCBX" process and was developed by
 SUNOHIO, a  partnership  between the
 Sun Company of Radnor, Pennsylvania
 and the Ohio Transformer Corporation
 of Louisville, Ohio. The equipment is in-
 stalled on two mobile trailers and can
 be driven to different geographical lo-
 calities to treat contaminated oils on
 site. The first test was conducted on De-
 cember 2,1982 at Chevron's USA El Se-
 gundo refinery. This was a joint venture
 between SCAQMD and the ARB. The
 second test was conducted on Decem-
 ber 10, 1982 at a PG&E facility in Union
 City. The third test was conducted on
 November 30,1983 at the San Diego fa-
 cility of Maxwell Laboratory.
  The objectives of the evaluation tests
 were to allow determination of emis-
 sions from the unit's vacuum degasser
 and determination  of the efficiency of
 two prototype emission  control sys-
 tems. One control system consists of an
 oil mist eliminator, in combination with
 an  activated charcoal filter  to control
 emissions from the vacuum degasser's
 vent pipe. The other control system uti-
 lizes an oil fired furnace that is a compo-
 nent of the PCBX process to incinerate
 the emissions.

 Conclusions and
 Recommendations
  Based on the analytical results and
 staff experience  obtained from the
 ARB's evaluation test conducted on the
 SUNOHIO PCBX process, the following
 observations are made:
  1. The activated  carbon adsorption
     canister used during testing is not
     big enough to provide effective
     emissions control for an extended
     period of time, the control system
     should be (1) redesigned to have a
     larger activated carbon adsorption
     unit, or (2) revise the  maintenance
     schedule for the present carbon
     canister to  require  canister re-
     placement with a frequency com-
     mensurate with a demonstrated
     breakthrough* time.
  2.  If  emissions are to  be  prevented
     from  the carbon canister, the car-
     bon canister breakthrough should
     be monitored  with  a continuous
     analyzer.
  3.  Based upon the results of this test,
     the oil fired furnace  as a control
     device appears to,be  effective.

Results and Discussion
  1.  Results From the Test Conducted
     at Chevron's USA El Segundo Re-
     finery
   Results of analyses performed on
   samples taken from the PCBX pro-
   cess during  the ARB evaluation
   test conducted at Chevron's USA
   El Segundo refinery indicate that
   Benzene and Ca-C^ hydrocarbons
   were the predominant  compo-
   nents measured in the gases
   vented directly out of the vacuum
   degasser during the treatment of
   transformer oil. Benzene concen-
   trations  ranged from 400 ppm to
   7,000 ppm and hydrocarbon con-
   centrations from 7 ppm  to 1,600
   ppm. TRW's  analytical  results for
   samples taken at the same location
   as the ARB, show benzene concen-
   trations exceeding 5,000 ppm and
   C5 hydrocarbon concentrations as
   being 1,400 ppm. TRW results for
   benzene are  in the range of con-
   centrations determined by the ARB
   and the hydrocarbon concentra-
   tions, while not directly compara-
   ble to the ARB results, are proba-
   bly not inconsistent. SCAQMD did
   not take samples from the vacuum
   degasser outlet.
   PCBs were not detected above the
   detection limit of the  analytical
   method for any of the  ARB sam-
   ples taken. TRW also sampled for
   and could not detect PCBs above
   the limit of detection for their ana-
   lytical method (1 ppm).
   As discussed  previously, SCAQMD
   took samples before and after the
   activated carbon adsorber and an-
   alyzed those  samples  for PCBs,
   furans, and dioxins. Because they
   sampled at a different location and
   the  emphasis of their analytical
   work was different, no direct com-
   parison can be made between the
   SCAQMD and ARB test results.
   Test results  indicate that furans
   and dioxins are not present above
   the detectable limits, less than 4-30
   parts per trillion. However, in two
   samples taken from the centrifuge
   vent at the inlet and outlet of the
   carbon  cannister, detectable
   amounts of PCBs were measured;
   1..7 (10~3) ppm at the inlet and 8.7
   (10~6) ppm at the outlet.

2.  Results  From the Test Conducted
   at PG&E's Union City Facility
   Benzene and aliphatic  hydrocar-
   bons were the major components
   measured in  the  ARB samples
   taken from the degasser vent dur-
   ing  the  treatment  of PCB-
   contaminated oils stored in a tank
   at a PG&E facility located in Union
   City. The range of concentrations
   determined for benzene and Ce-C^
   hydrocarbons was 50 to 950 ppm
   and 1,900 to 2,700 ppm, respec-
   tively.
   Benzene and aliphatic hydrocar-
   bons were  also  the  significant
   components in the treated vacuum
   degasser vent gas as  sampled at
   the outlet from the control  sys-
   tem's activated charcoal adsorber.
   The range of benzene concentra-
   tions was 600-700  ppm and  the
   range of Ce-C^ hydrocarbons was
   1,400 to 1,800 ppm. BAAQMD also
   took samples at the charcoal  ad-
   sorber outlet and test results
   showed: a comparable benzene
   concentration  of 840 ppm (aver-
   age); a comparable C6-Ci2 hydro-
   carbon concentration  of 1,500
   ppm; and total organic and non-
   methane organic  compound con-
   centrations of 2,600 ppm (average)
   and 2,400 ppm (average), respec-
   tively.
   The control system's charcoal can-
   ister was the same one used at the
   El Segundo test. Results of a com-
   parison between  the  concentra-
   tions determined for the inlet and
   outlet of the control system are in-
   dicative of carbon adsorption
   breakthrough. The reduction of
   both benzene and aliphatic hydro-
   carbons was  approximately 30
   percent across the control system.
   PCBs were not detected above the
   detection  limit of the analytical
   method for any of the ARB sam-
   ples taken.

3.  Results From the  Test Conducted
   at the  Maxwell Laboratory in San
   Diego
   Concentration values for emis-
   sions were measured  during two
   distinct phases of the  PCBX  pro-
   cess: (i) degassing and (ii) dechlo-
   rination. Benzene concentrations
   in the uncontrolled vacuum  de-
   gasser emissions,  measured at the
   common inlet to both control sys-
   tems, ranged from 18 ppm to 220
   ppm. Toluene was also measured
   at concentrations ranging from 0.1
   ppm to 290 ppm.
   At the  outlet from the  condenser/
   carbon control systems, measured
   benzene concentrations ranged
   from 10 ppm  to 23  ppm and
   toluene from 0.1 ppm to 26 ppm.
   Benzene and toluene were not

-------
     measured above the 0.1 ppm limit
     of detection in the exhaust gases
     from the combustion control de-
     vice.
     Products of combustion in the fur-
     nace exhaust gas were monitored
     when the furnace was fired on fuel
     oil only and when it was fired with
     a mixture of fuel oil  and vacuum
     degasser vapors. When combust-
     ing  fuel oil  only, the following
     compounds were measured: 75
     ppm S02, 72 ppm NOx, 9.3 ppm
     THC, 133 ppm CO,  10.2 percent
     C02 and 9.7 percent 02. When vac-
     uum degasser vapors were added
     for  combustion  in the furnace,
     measured concentrations were: 78
     ppm S02, 92 ppm NOx, 24 ppm
     THC, 200 ppm CO,  10.2 percent
     C02, 9.1 percent 02, 0.1 ppm ben-
     zene and 0.1  ppm, toluene.
     Samples taken before and after the
     control devices were speciated to
     determine the types of compounds
     present in the emissions. For com-
     parison purposes, a sample of am-
     bient air was taken. The com-
     pounds detected in  the ambient
     sample were all at the part per bil-
     lion (ppb) level. The magnitude of
     the  other concentration  values
     measured in the uncontrolled and
     controlled emissions were at the
     part per million level.

Commercial Demonstration of
Wet Air Oxidation of  Hazardous
Wastes
Summary
  Wet Air Oxidation by Zimpro, Inc., is a
process which has been used to oxidize
dissolved or suspended  organic sub-
stances at elevated  temperature  and
pressures. The process  is thermally
self-sustaining with relatively low or-
ganic feed concentrations  and is, there-
fore, most useful for wastes which are
too dilute to incinerate economically yet
too toxic to treat biologically.
  The purpose of this project  was to
demonstrate wet air oxidation of toxic
and hazardous wastes at  a full-size in-
stallation which was located at Cas-
malia Resources,  a  commercial waste
treater in California. In the operation of
the full-scale Zimpro Wet Air Oxidation
unit, wastes selected from classified
groups of organic wastes were detoxi-
fied. These classified groups were: phe-
nolic wastes,  organic sulfur wastes,
general organic wastes,  cyanide
wastes, pesticide wastes, and  solvent
still bottoms wastes. This section con-
tains detail evaluation of these six clas-
sified wastes' treatment, the effective-
ness of the wet air oxidation unit, and
sample analysis of feed and effluent.

Description of Wet Air
Oxidation Process

  The Zimpro Wet Air Oxidation unit for
this demonstration processed aqueous
wastes at a designed reactor tempera-
ture of 550°F, a  designed reactor  pres-
sure of 2,000  PSIG, a liquid waste flow
rate of 10 GPM, and a compressed air
rate of approximately 190 SCFM. In the
wet oxidation process, liquid waste, ex-
iting from  a  high  pressure pump, is
combined with compressed air and di-
rected through the cold, heat-up side of
the heat exchanger. The incoming
waste-air mixture exits from the heat-up
side  of the  heat exchanger and enters
the reactor where exothermic reactions
increase the temperature of the mixture
to a  desired value. The waste-air mix-
ture exits the reactor and enters the hot,
cool-down side  of the heat exchanger
and, after passage through the system
pressure control valves, is directed to
the separator.  In the separator, the
spent process vapors (noncondensible
gases) are separated from the oxidized
liquid phase and are directed into  a
two-stage water scrubber-carbon bed
adsorber, vapor treatment system.
  In  the wet air oxidation  process, or-
ganic substances can be completely ox-
idized to yield highly oxygenated prod-
ucts  and water.  For example, organic
carbon-hydrogen compounds can be
oxidized to carbon dioxide and water,
while reduced organic sulfur com-
pounds (sulfides, mercaptans, etc.) and
inorganic sulfides are easily oxidized to
inorganic sulfate, usually present in the
oxidized liquor as sulfuric acid.  Inor-
ganic cyanides and organic cyanides
(nitriles) are easily oxidized to carbon
dioxide, ammonia, or molecular nitro-
gen. It should be noted that oxides of
nitrogen such as NO or N02 are not
formed in wet air oxidation.
  When incomplete oxidation of or-
ganic substances occurs, the easily oxi-
dized reduced sulfur and cyanides are
usually still oxidized to sulfate and car-
bon dioxide-ammonia provided a suffi-
cient degree of oxidation is accom-
plished. However, incomplete oxidation
of other organic compounds results in
the formation of low molecular weight
compounds such as acetaldehyde, ace-
tone, and acetic acid. These low molec-
ular weight compounds are volatile and
are distributed between the process
off-gas phase and the oxidized liquid
phase. The concentration of these low
molecular weight compounds (mea-
sured as total hydrocarbons  (THC) ex-
pressed as methane) in the process of
off-gas is dependent on their concentra-
tion in the oxidized liquid phase, which
is determined by the degree of oxida-
tion accomplished, the waste being oxi-
dized, and the influent organic concen-
tration of the waste.

Results and Conclusion

  Wet air oxidation of phenolic and or-
ganic sulfur  classes of waste has been
demonstrated at the Casmalia Re-
sources, Inc., full-scale wet air oxidation
installation.  Oxidation of a  petroleum
refining spent caustic waste at a process
temperature of 515°F (268°C)  and a
nominal residence time of 113 minutes
resulted in 99.77 percent total phenols
reduction, 94.0 percent  organic sulfur
reduction, and 89.3 percent chemical
oxygen demand (COD) reduction. Gas
chromatographic/mass  spectroscopic
(GS-MS) analysis identified acetic acid,
benzoic acid, and several sulfide deriva-
tives as the major components present
in the effluent oxidized waste. Analysis
of treated process off-gases indicated a
total hydrocarbon (THC) concentration
of only 84.5  ppm (expressed as
methane).
  Oxidation  resulted in  >99.7 percent
sulfide sulfur  reduction, 98.8  percent
total phenols reduction, and 81.3 per-
cent COD reduction. Sulfide sulfur and
total phenols concentrations were re-
duced to > 1.0 mg/l and 66 mg/l, respec-
tively, upon oxidation.  Further reduc-
tion  in residual total  phenols
concentration would likely be achieved
by postoxidation treatment with ozone
or hydrogen peroxide.
  The raw spent caustic wastewater
had a BODs/COD ratio of 0.49 compared
to 0.64 for the oxidized product indicat-
ing a slight increase in biodegradability
following oxidation. The oxidized prod-
uct would likely be easily biodegradable
since highly biodegradable  materials
generally have BODs/COD ratios in the
range of 0.5 to 0.6. The wastewater pH
decreased from 12.6 in the raw waste to
8.7 upon  oxidation, likely due to the
conversion of reduced sulfur com-
pounds to sulfuric acid.
  An eight-hour wet air oxidation dem-
onstration of a general organic waste-
water was performed at the Casmalia

-------
Resources, Inc., full-scale wet oxidation
installation on July 28, 1983.
  The general organic wastewater was
processed continually during the eight-
hour wet air oxidation demonstration.
During the demonstration period, the
wet air oxidation unit was operated at
an average reactor temperature of 531°F
(277°C), a  compressed air flow rate of
190 SCFM and a reactor pressure of
1,515 PSIG. Waste was processed at an
average liquid flow rate of 5.0 GPM re-
sulting in a nominal  residence time of
120 minutes. Residual oxygen concen-
trations in the process off-gas averaged
4.1  percent during the demonstration
period.
  The data  indicates the waste to be rel-
atively high strength with a chemical
oxygen demand (COD) of  76.0 g/l and a
dissolved  organic carbon (DOC) con-
centration of 20,830 mg/l. The  raw
waste had  a pH of  1.9. Very effective
treatment  of the general organic waste
was obtained by wet air oxidation. Oxi-
dation resulted in 96.7 percent COD re-
duction with the waste COD reduced to
2.5 g/l. A DOC reduction of 96.7 percent
was obtained with the oxidized waste
having a DOC concentration of 685 mg/l.
  Analysis  of the off-gas  sample indi-
cated carbon dioxide, oxygen, nitrogen,
and carbon monoxide concentrations of
12.9, 5.9, 81.2, and 0.3 percent, respec-
tively. Total hydrocarbon  (THC)  and
methane concentrations  of 29.1 ppm
(expressed as methane)'and 10.0 ppm,
respectively, were determined for the
process off-gas sample.
  Treatment of cyanide wastewafers by
wet air oxidation  has been demon-
strated at the Casmalia Resources, Inc.,
full-scale wet air oxidation installation.
The wet air oxidation  demonstration
was performed on July 29 and August
18,1983 during a combined six-hour pe-
riod of steady state operation.
  The wastewater processed during the
wet air oxidation demonstration was a
mixture of cyanide wastes generated by
various metal plating processes. Labo-
ratory screening tests performed by
Zimpro, Inc., indicated the individual
wastes contained in the wastewater
mixture to be treatable by wet air oxida-
tion and compatible with respect to ma-
terials of construction.
  During the combined demonstration
period, the wet air oxidation unit  was
operated at an average reactor temper-
ature of 495°F (257°C), a compressed air
flow rate of 190 SCFM, and a reactor
pressure of 1,220 PSIG. Waste was pro-
cessed at an average liquid flow rate of
7.5 GPM, resulting  in a nominal  resi-
dence time of 80 minutes. Residual oxy-
gen concentrations  in the  process off-
gas averaged 7.1 percent during the
demonstration period. The analyses in-
dicate the composite raw waste to be a
typical  high  strength  cyanide waste
with a cyanide concentration of 25,390
mg/l, chemical  oxygen demand (COD)
of 37.4,  g/l and  pH of 12.6.
  Wet air oxidation  resulted in very ef-
fective treatment of the cyanide waste.
The cyanide concentration of  the raw
waste was reduced to 82  mg/l, repre-
senting  a cyanide reduction of 99.7 per-
cent. A  COD reduction of 88.8 percent
and a dissolved organic carbon (DOC)
reduction of 88.4 percent were obtained
by wet air oxidation. COD and DOC con-
centrations in the composite oxidized
waste were 4.2 g/l and 1,710 mg/l, re-
spectively.
  The scale formation which  occurred
in the oxidation unit during the cyanide
demonstration period is reflected by the
total ash data. The composite raw waste
had a total ash concentration of 112.9 g/l
compared to only 77.4 g/l for the com-
posite oxidized  waste. Since the ash is
expected to pass through the oxidation
unit as inert material, the data indicates
as much as 35  g/l of inert solids were
deposited in the oxidation  system dur-
ing treatment of the cyanide waste.
  Analysis of the off-gas sample  indi-
cated 1.5 percent carbon  dioxide, 8.5
percent  oxygen, and 82.8 percent nitro-
gen.  Carbon monoxide was  not de-
tected in the off-gas  sample. A total hy-
drocarbon (THC) concentration of 61.1
ppm  (expressed as methane) and a
methane concentration of 9.0 ppm was
determined for the process off-gas sam-
ple.
  Wet air oxidation of four pesticides—
dinoseb, methoxychlor, carbaryl, and
malathion—was evaluated  in a  full-
scale demonstration at Casmalia Re-
sources, Casmalia, California, on March
28,  1984. Since wastewaters containing
relatively high concentrations of a  vari-
ety of pesticides were not easily avail-
able, the above compounds were
spiked into an  acidic distillate waste-
water which had previously been  pro-
cessed in the Casmalia wet air oxidation
unit.
  Prior to the full-scale pesticides wet
air  oxidation demonstration, bench
scale autoclave  oxidations  of a variety
of pesticides had  been  evaluated.
Greater than 99 percent destruction was
observed for seven pesticides, includ-
ing the four subsequently demon-
strated in the Casmalia full-scale unit.
  Removals of the four pesticides
ranged from 98.0 to greater than 99.8
percent. Analyses  of pesticides in the
feed and effluent composites were by
gas and liquid chromatography.

  COD, BOD5, and  DOC removals were
quite similar to results obtained during
oxidation of the acidic distillate waste
alone. COD, BOD5, and DOC removals
of 95.3, 93.8, and 96.1 percent were ob-
served. Carbon dioxide, oxygen,  nitro-
gen, and carbon monoxide concentra-
tions of 14.2, 3.5, 79.0, and 0.7 percent,
respectively, were  observed. Total hy-
drocarbon (THC) and methane concen-
trations of 153 ppm  (expressed as
methane) and 61.9 ppm, respectively,
were determined for the process off-gas
sample.
  Wet air oxidation of a solvent still bot-
toms type waste was evaluated in a full-
scale  demonstration at Casmalia Re-
sources, Casmalia,  California, on March
29, 1984. The wastewater  was  pro-
cessed continuously during the eight-
hour wet air oxidation demonstration.

  Soluble chloride analyses for feed
and effluent indicated 7,860 and 505
mg/l, respectively.  These  data indicate
material in  the feed causing  a positive
interference 'in the chloride analysis.
Oxidation of this material resulted in an
apparent decrease  in -soluble chloride.
This behavior is frequently seen in the
wet air oxidation of industrial wastes.

  Soluble fluoride increased from 7.5 to
42.7 mg/l upon oxidation, likely due to
the destruction of  fluorinated  organic
compounds. This fluoride content was
not observed  in previous bench  scale
screening of this wastewater. Fluoride
levels much higher  than this may not be
acceptable in the Casmalia wet air oxi-
dation unit because of corrosive effects
on titanium system components.
  Carbon dioxide,  oxygen,  nitrogen,
and carbon  monoxide concentrations of
11.8, 3.8, 81.2, and nil percent, respec-
tively,  were observed. THC  and
methane concentrations of 217 ppm
(expressed as methane) and 80 ppm, re-
spectively, were determined for the pro-
cess off-gas sample. However, on-line
off-gas THC  measurements  indicated
increasing THC concentrations through-
out the demonstration run as the vapor
phase activated carbon  adsorption bed
became exhausted.

-------
Air Resources Board's
Evaluation Test Conducted on a
Wet Air Oxidation Process to
Treat Hazardous Wastes

Summary
  The California Air Resources Board
(ARB) conducted six evaluation tests on
a wet air oxidation unit manufactured
by Zimpro, Inc. The unit designed to
treat toxic wastes is installed and oper-
ated at a Class I waste disposal facility
managed by Casmalia  Resources and
located in Casmalia, California. The test
results of the four  category wastes,
namely—phenols, sulfides, acid organ-
ics, and cyanides—are discussed in the
full report.
  The ARB  evaluation tests were initi-
ated in response to a request by Santa
Barbara County Air Pollution Control
District for emission data with which to
properly  establish and  assess the wet
air oxidation unit's waste processing  ca-
pabilities and the effectiveness of the air
pollution control devices.

Results and Discussion
  1.  Wet Air Oxidation Process
     Wet air oxidation appears to be an
     effective method for reducing the
     concentration of  liquid phase
     cyanide and  phenol compounds.
     Cyanide concentrations measured
     at the inlet and outlet of the wet air
     oxidation  process were 46,300
     parts per  million by weight (ppm
     W) and 6.94 ppm W, respectively.
     Inlet and outlet phenol concentra-
     tions were 18,700 micrograms per
     milliliter  (jjig/ml) and 2.35 (jig/ml.
     The reduction in concentration  for
     both compounds  treated by the
     wet air oxidation process was over
     99 percent.
     However, wet air oxidation of acid-
     organics was somewhat less con-
     sistent. Two sets  of inlet-outlet
     samples were  taken across  the
     process with one  indicating a  64
     percent reduction of the initial con-
     centration and the  other, a 97 per-
     cent reduction. Each value was ob-
     tained by ratioing the GC/FID
     generated total peak areas for an
     inlet-outlet  sample pair taken
     across the wet air oxidation pro-
     cess. When the output sample's
     GC/FID trace was compared to that
     for the inlet sample, some peaks
     had disappeared, some were no-
     ticeably reduced, and in some  in-
     stances, new peaks appeared. Be-

                                  6
  cause the availability of standards
  to identify each peak was limited,
  the ratio of total  peak areas was
  used to give a relative indication of
  the wet air oxidation process.
2. Condensible,  Noncondensible
  Separator
  With  the  exception of  acid-
  organics, the amount of noncon-
  densible cyanide, phenols, and
  sulfide measured  at the separator
  was at the  microgram level. The
  quantity of CN, phenol, and sulfide
  captured was 3.23 |xg, and 713 jxg,
  respectively. These values also
  represent the  prescrubbed gas
  concentrations at the inlet to the
  scrubber. The total volume drawn
  for each sample was 45 cubic feet.
  A "less than" symbol (<) preced-
  ing a value implies that it is below
  the detection limit of the analytical
  method with respect  to the total
  volume sampled.
  Noncondensible acid-organic
  samples taken at the separator
  were  used to identify and  semi-
  quantitate the major organic com-
  ponents present in the gas stream
  prior to entering the control equip-
  ment. The results show that for the
  treatment of this particular waste,
  halogenated  (bromo-, chloro-)
  alkenes and benzene appear to be
  the major compounds in the gase-
  ous effluents from the separator.
3. Scrubber
  The scrubber was effective in re-
  moving sulfide from the gas
  stream but did  not afford any
  greater  control  advantage for
  cyanide and phenols than was
  achieved by the wet air oxidation
  process.
  The calculated cyanide concentra-
  tion at the inlet was very low,
  0.0025 jxg/l or 0.0034 ppm.
  The measured scrubber efficiency
  for controlling noncondensible
  sulfide was 93.4 percent. The
  scrubber reduced the inlet concen-
  tration of 0.555 |jig/l, or ppm, to
  0.037 (i.g/1, or ppm.
  The outlet cyanide concentration
  of 0.0026 jig/l, <0.0025 ppm is
  comparable to the inlet concentra-
  tion and indicates that the scrub-
  ber has no apparent effect on
  cyanide when this compound is in-
  troduced into the scrubber at such
  low levels.
  It appears that a major portion of
  the residual phenols and cyanides
    remaining after the wet air oxida-
    tion process is retained in the sep-
    arator's liquid  phase and pumped
    to the facility's water discharge
    pond. Any liquid phase  reactions
    that may be  occurring are  un-
    known. There  is a minimal contri-
    bution of cyanide and phenols to
    the gas phase for control  by the
    scrubber.  However, whether the
    scrubber  would be an  effective
    control device at higher inlet con-
    centrations of cyanide and  phe-
    nols,  as might occur during an
    upset condition, is yet to be deter-
    mined.
  4. Carbon Bed
    The carbon bed was most effective
    in controlling the discharge to at-
    mosphere of  gas  phase bromi-
    nated compounds. The inlet  con-
    centration of 450  ppm  was
    reduced to 0.18 ppm at the outlet
    of the carbon  bed, representing a
    removal efficiency of over 99 per-
    cent. Note that these concentration
    values are order of magnitude esti-
    mates based on (a) the qualitative
    speciatipn  data that identified
    brominated hydrocarbons as the
    major noncondensible hydrocar-
    bons  present and (b) quantitative
    analysis that normalized all
    significant GC  peaks to  1,2-
    dibromomethane, which was the
    major identifiable compound for
    which a standard was available.
    The normalization technique was
    performed because  standards
    were  not  available  for the other
    major peaks. A comparison of
    these values will give a relative ef-
    ficiency performance of the carbon
    adsorber.
    The percentage control for cyanide
    and sulfide was minimal: 17.8 per-
    cent  and 26.8 percent, respec-
    tively.
  The full  report was submitted in par-
tial fulfillment of Cooperative  Agree-
ment No. R-808908 under sponsorship
of the EPA and the State of California,
DHS.
                                                                       U. S. GOVERNMENT PRINTING OFFICE:1986/646-l 16/20750

-------
   Jan Radimsky and Arvind Shah are  with  Department  of Health  Services,
     Sacramento. CA 95814.
   Harry M. Freeman is the EPA Project Officer (see below).
   The complete report,  entitled "Evaluation of Emerging Technologies for the
     Destruction of Hazardous Wastes,"  fOrder No. PB 86-128 717/AS; Cost:
     $16.95, 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
     BULK RATE
POSTAGE & FEES PAID
        EPA
  PERMIT No. G-35
Official Business
Penalty for Private Use $300

EPA/600/S2-85/069

-------