HW
   EP 230/3
   85-502
   vol. 2
           United States        Off ice of Policy,       March 1985
           Environmental Protection    Planning and Evaluation
           Agency          Washington, DC 20460     230385502B


           Policy Planning and Evaluation
\vEPA     Assessment of Incineration
           As A Treatment Method for
           Liquid Organic Hazardous
           Wastes
           Background Report II:
           Assessment of Emerging
           Alternative Technologies

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ASSESSMENT OF ALTERNATIVE TECHNOLOGIES
March 1985
A background report for the study by EPA's
Office of Policy, Planning and Evaluation:
"Assessment of Incineration As A Treatment
Method for Liquid Organic Hazardous Waste."
Prepared by:

James Basilico, Harry Freeman,
Tim Oppelt, Glen Shira
U.S. Environmental Protection Agency
Office of Research and Development
Hazardous Waste Engineering Research Laboratory
26 West St. Clair Street
Cincinnati, Ohio  45268

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                        TABLE OF CONTENTS
EXECUTIVE SUMMARY ..........................................   1






INTRODUCTION ...............................................   7






EXISTING ALTERNATIVE THERMAL PROCESSES  .....................   9






     Hazardous Waste as Fuel in Industrial Processes  .......   9




     Incineration of Hazardous Waste  in Power Boilers  ......  10






EMERGING ALTERNATIVE TECHNOLOGIES  ..........................  13






     High Temperature Electric Reactor  .................... .  16




     Molten Salt ...........................................  17



     Plasma Arc ............................................  18




     Wet Air Oxidation .....................................  20




     Molten Glass Incineration .............................  23




     Supercritical Water ...................................  24






BIOLOGICAL TREATMENT .......................................  26






CHEMICAL TREATMENT .........................................  27






Appendix ...... .......................... .... ...............  29






References .................................................  32

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                        EXECUTIVE SUMMARY








     Assessment of incineration as a treatment method for




liquid combustible and other liquid organic waste streams must




take into account the availability of technologies that offer




suitable treatment and destruction alternatives to conventional




incinerators.  This report reviews existing and emerging thermal,




chemical, and biological hazardous waste destruction processes




that can be used to treat or destroy the same types of liquid




organic wastes that are presently destroyed in incinerators.






     The processes reviewed are those that currently exist, or




may exist in the next five years.  Existing alternative technologies




are defined as those processes other than conventional incineration




that are in existence today, are suitable for treating or destroying




liquid organic waste streams, and are available for commercial




use.  Emerging alternative technologies are innovative processes




that are suitable for treating or destroying liquid organic




waste streams, but have not yet been adopted for commercial use.






     This report addresses the following questions:




     1.  What technologies other than incineration are now




         available, or may be available in the near future, to




         treat, destroy, or recycle combustible liquid hazardous




         wastes?




     2.  What is the likely commercialization rate of each of




         these technologies?

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     3.  How do these technologies compare to incineration in



         terms of cost, capability, benefits, and environmental



         and human health impacts?






     Each alternative technology is described in terms of the



types of waste the system is capable of accepting, throughput/



capacity of the process, operational costs, anticipated environmental



impact, and anticipated date for commercialization (for emerging



technologies).






     Although liquid organic waste streams can theoretically be



treated in various thermal, chemical, and biological processes,



only thermal processes were determined to be significant alternatives



to conventional incineration.  This is because biological and



chemical processes are only in the initial stages of development,



have environmental impacts that are numerous and hard to predict,



are expensive, and are frequently incapable of handling combustible



liquid organic hazardous wastes.  Biological and chemical processes



were found to be either inappropriate or suitable for only small



amounts of the waste streams in question.





EXISTING ALTERNATIVE TECHNOLOGIES






     The existing thermal alternative technologies believed to be



most suitable are industrial processes (cement kilns, lime kilns,



and aggregate kilns), and co-combustion in industrial boilers.



At the present time, susbstantially more hazardous waste is burned



in industrial boilers than in incinerators.

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EMERGING ALTERNATIVE TECHNOLOGIES






     Twenty-five emerging technologies were initially considered




for inclusion in the report using the following criteria:




     1.  Is the process designed for a liguid organic waste stream?




     2.  Is the process at a development stage to be commercially




         available within five years?




     3.  Is the process innovative, or is the process just a




         modification of conventional incineration technology?






     Only a few of the processes reviewed meet all three criteria




and thus were determined to be relevant to this study.  Those




emerging processes selected for further consideration in the




study are:




     1.  High Temperature Electric Reactor




     2.  Wet Air Oxidation




     3.  Plasma Arc




     4.  Supercritical Water




     5.  Molten Salt Reactor




     6.  Molten Glass Incineration






     It should be noted that not all of these alternatives are




able to destroy the full range of wastes handled by conventional




incinerators.  However, for the purpose of this study, candidate




waste streams for treatment by emerging alternative technologies




were identified, based on EPA data that they represent the highest




volumes of  waste incinerated in the United States in 1981.

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COMPARISON OF ALTERNATIVE TECHNOLOGIES WITH CONVENTIONAL
INCINERATION


Cost

     Cost figures for all of the technologies, especially some of

the emerging technologies, are not available.  Although it varies

by waste, there is a considerable reclamation of energy value in

the existing alternative processes (cement kilns and boilers).

Therefore, their overall costs are less than those for incineration,

Another major advantage is that the use of existing facilities

requires little capital investment.  Among emerging processes,

costs for supercritical water, plasma arc, and molten glass will

exceed conventional incineration, while costs for wet oxidation,

the high temperature electric reactor, and molten salt appear

comparable to conventional incineration.


     It should be pointed out that each of these systems offers

advantages over conventional incineration for specific waste

streams that may more than offset the increased costs.  Some

advantages are:  the ability to handle small or large quantities

of highly toxic wastes; smaller units to make on-site treatment

economically feasible and eliminate safety factors of handling

and transportation; portable units; and less production of air

emissions.  Thus, decisions about the probability of these

technologies replacing  incinerators cannot be made on the basis

of cost alone.

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Throughput/Capacity



     Capabilities and capacities of the various processes evaluated



vary widely.  Existing alternative technologies are capable of



consuming significant amounts of liguid wastes, especially under



existing regulations which exempt these processes from RCRA



incineration standards.  However, the Agency is now developing



standards for these processes similar to those for hazardous



waste incinerators.  As a result, the capability of these processes



to dispose of waste may be lessened considerably.  (The potential



impact of these standards on the market for incineration is not



addressed in this report.)






Commercial Status



     Emerging alternative technologies will have minimal impact on



the quantity of liquid hazardous waste currently destroyed in



conventional processes.  Although all of the emerging processes



evaluated offer some technical advantages, their commercial



adoption will not significantly affect the market for conventional



incineration, since it is expected that these new processes will



only be used on the most toxic wastes, representing only 2-3% of



liquid combustible waste streams.






Environmental Impact






     More testing will be needed to determine the environmental



effects of both existing and emerging alternative technologies.



Environmental effects of the existing alternative technologies

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are currently being assessed.  RCRA regulations are now being



proposed for industrial boilers to assure that their operating



performance is protective of human health and the environment.



For most emerging alternative technologies, the environmental



impacts have not been tested.  In many cases, their effects are



expected to be roughly comparable to those of conventional



incineration.

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INTRODUCTION



     The purpose of this task is to assemble available information  on



technologies, both existing and new, that offer alternatives to either



land based or ocean incineration of liquid hazardous  wastes.









     The processes of interest in this task are those that  currently



exist, or that may exist in the next five years.  They are  not incineration



processes, but can be used to treat or destroy the same types of liquid



organic waste streams that are presently destroyed in incinerators.



Existing alternative technologies are defined as those processes other



than conventional incineration that are in existence  today, are suitable



for treating or destroying liquid hazardous waste streams,  and are



available for commercial use.  For example, the process of  burning



hazardous waste as a fuel in cement kilns is an existing alternative



technology  because it is an alternative to conventional incineration



that is practiced commercially.



Emerging alternative technologies are innovative processes  that are



suitable for treating or destroying liquid hazardous  waste  streams, but



have not yet been adopted for commercial use.  The process  of using high



temperature plasma to destroy wastes is an emerging technology, because



it is still under development and has yet to be widely used for the



treatment of hazardous wastes.

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     Another point to emphasize is  that  this  report  addresses  only those



processes that are intended to  treat  or  destroy  liquid  organic waste



streams.  Many emerging technologies  for hazardous waste  treatment are



designed to treat other types of waste  streams,  i.e.  solids, or  inorganic



waste streams.  Finally, for the purpose of this report,  improved



incineration processes  such as fluidized bed incinerators  or  mobile



incinerators  are treated as conventional incineration  rather  than



alternative technologies, and are not discussed.



     The task is directed towards answering the  following three  questions:



     1)  What technologies besides  incineration  are  available  (or may be



         in the near future) to treat, destroy or recycle combustible



         liquid hazardous wastes?



     2)  What is the likely commercialization rate of each  of  these



         technologies?



     3)  How do these technologies  compare to incineration  in  terms  of  cost,



         capability, benefits, and environmental and human  health  impacts?



     In the subsections that follow are brief discussions of  the alternative



processes included in the study.  Each discussion is structured  as  follows:



     1.  Brief discussion of technology involved.



     2.  What type of wastes is the system capable of accepting.



     3.  Throughput/capacity of process.



     4.  Operational costs.



     b.  Anticipated date of commercialization (for  emerging  technologies).



     6.  Environmental  considerations.

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EXISTING ALTERNATIVE THERMAL PROCESSES



     The following existing technologies were identified as alternative



technologies that are practiced commercially and should be included in



this study:



     0  Disposal  in industrial  processes (cement kilns, lime kilns,



        aggregate kilns)



     0  Co-combustion in industrial  boilers



HAZARDOUS WASTE AS FUEL IN INDUSTRIAL PROCESSES



     An integral  part of the production of products such as cement,



limestone, and aggregate is the roasting of the feed material in large



rotary kilns.  The purpose of this roasting is to produce a temperature



high enough for the chemical reactions necessary to produce the product



to occur.  Because of the high process temperatures (2000 - 2600°F),  and



because of the long residence times for combustion, kilns are potential



thermal treatment devices for destroying many organic wastes.  These



wastes can be used as supplemental fuels, replacing some of the primary



fossil fuels such as fuel oil or coal normally used to fire the kilns.



Suitable Hastes



     The types of waste suitable for co-combustion in kilns is very



dependent upon the individual process.  However, generally kilns can



accept waste solvents, bottoms from solvent reclamation operations, and



paint residues.



Throughput/Capacity



     1,UOO - 25,000 gallons/day of liquid organic wastes can be processed



in a kiln depending upon the size of the kiln and the percentages of the



primary fuel replaced by the waste fuel.

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COST PER UNIT OF WASTE PROCESSED



     Costs can vary from zero,  reflecting a  company's  accepting  a  very



high energy waste solely for its fuel  value, to some 20 to 25 cents  per



gallon.



ENVIRONMENTAL DATA



     Assessments conducted by EPA and  others have produced mixed results



on the environmental and health effects of combusting waste chemicals  in



cement kilns.  However, they indicate  that when a kiln is  operated



properly, its emissions are comparable to those of a well  operated



incinerator, and meet emissions standards for incineration.



Anticipated Date of Commercialization



     Technology is currently being utilized on a commercial basis.  An



estimated 3.5 million tons of waste went to industrial processes in



1981 U).



INCINERATION OF HAZARDOUS HASTES IN POWER BOILERS



     Under RCRA, the regulations and specific process performance standards for



hazardous waste incineration do not apply to the use of combustible  hazardous



waste as fuels in energy recovery operations such as power boilers.   In  part



because of this regulatory situation and because of the obvious  attractiveness



of reclaiming energy from waste, significant quantities of liquid hazardous



waste are disposed of in industrial boilers.  EPA studies  have estimated that



3.5 million tons of hazardous wastes were disposed of in this manner in  1981,



more than twice the amount disposed of in incinerators that year  (1).
                                      10

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1,800
300
8,100
14,200
400
15,900
9,200
1,800
46,000
37,300
2,000
57,700
5,200
1,500
11,500
2,200
11,300
11,300
     There are currently about 400,000 boilers of all  types  in  the U.S.

including industrial,  commercial,  residential  and off-site power.   Of

these boilers, about 240,000 can be classified as industrial  installations.

This figure includes boilers of all  types  and  all  sizes.  Table 1  breaks

down the industrial  boiler population by fuel  type and size.


                                    Table  1

          Capacity (BTU/HR) of Industrial  Boilers by Fuel Type  (1975)

Fuel Type                   < 106          10^ and < 107        > 107

Stoker Coal
Pulverized Coal
Residual Ui1
Distillate oil
By-Product Gas
Natural  Gas


     Most of these boilers are very small  natural  gas or  oil-fired firetube

or cast iron units used for space heating.  Such installations  are generally

package units and do not easily lend themselves to either waste firing or

to the fuel blending required in waste co-firing.  However,  examination

of Table 1 shows that there are about 43,000 industrial boilers in the

U.S. with capacities larger than 10 million BTU's per hour.   These larger

boilers have the greatest potential  for use in hazardous  waste  destruction

processes.

     It is more the rule than the exception that large organic  chemicals

producers operate one or more boilers on the plant premises.  Some of

these plants use boilers for on-site destruction of organic  chemical

wastes; the number of boilers used is not  known.
                                       11

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Suitable Wastes



     Boilers are generally capable of accepting any  lowly  halogenated



liquid organic waste stream.  It is possible to burn up to 3% halogenated



wastes, but usually because of corrosive waste streams only approximately



1% halogens are burned.



Process Throughput



     Depends on the size of the boiler.  A large boiler using organic



wastes to replace 25% of the feed would consume 500  gallons per day of



waste.  However, studies have indicated that 10% of  the feed is more



typical.



Cost Per Unit of Waste Processed



     No specific cost figures were located.  However, given that most



waste that is burned in boilers  is burned on-site and replaces conventional



incineration, the additional cost is minimal compared to providing for a



separate facility for incineration of the waste.



Anticipated Date of Commercialization



     Burning waste in boilers is widely practiced.  The EPA has estimated



that 1300 boilers utilized hazardous waste as fuel in 1981 (1).



Environmental Data



     The Agency is presently supporting a large research program to obtain



environmental effects information on burning wastes  in boilers.  Field test



data have shown that boilers can achieve waste destruction efficiencies



comparable to those of incinerators.  Current evaluations are underway to



determine emissions from boilers operating at less than optimum conditions.
                                      12

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EMERGING ALTERNATIVE TECHNOLOGIES



     Currently there are many new processes  in various  stages  of



development for treating and destroying all  types of hazardous waste.



Some of these processes are essentially improvements on conventional



treatment and destruction methods.  Examples of such are fluidized bed



incineration, which is considered by many to be an improvement over



conventional incineration.  Other processes  represent entirely new approaches



to waste treatment.  The former group are included with conventional



methods and not addressed, and the latter considered emerging  technologies.



     The processes discussed in this section were compiled from responses



to two national solicitations for new hazardous waste treatment ideas,



from several literature reviews, and from contact with  experts in the



field.  This procedure identified many processes that represented new



approaches to hazardous waste treatment and  destruction.  However, only a



few of the processes identified were determined to be relevant to this



study, i.e. designed for liquid organic wastes and sufficiently close to



commercialization to significantly affect within the next five years  the



waste management practices of the Country as a whole.  A list  of  the



processes reviewed for this study is attached as Appendix A.  Those



processes determined to be emerging processes relevant  to this study  are:



     0  High Temperature Electric Reactor



     0  Molten Salt Reactor



     0  Plasma Arc
                                     13

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     0  Wet Oxidation
     0  Supercritical  Water
     0  Molten Glass Incineration
     It should be noted that none of these alternatives are able to destroy the
full  range of wastes now handled by  conventional  incinerators.

                            Candidate  Waste  Streams

     The following waste streams were  identified  as  candidate  streams  for
treatment by alternative technologies.  This selection  was  based  on  EPA  data
indicating that these waste  streams  represented the  highest volumes  incinerated
in the U.S. in 1981.

EPA Waste #                        Description
DUU1                 Hazardous waste that exhibits characteristic of ignitability
D002                 Hazardous waste that exhibits characteristic of corrosivity
DOU3                 Hazardous waste that exhibits characteristic of reactivity
F001-F002            Spent halogenated solvents
FU03-F005            Spent non halogenated solvents
K049                 Slop oil  emulsion solids from the  petroleum  refining  industry
KUbl                 API separate sludge
                     PCB's
                                     14

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                                    TABLE 3



                     ALTERNATE TECHNOLOGY VS WASTE STREAMS

Incineration
Industrial
Processes
Boiler
Co-combustion
High Temp. Electric
Reactor
Molten Salt
Plasma Arc
Wet Oxidation
Molten Glass
Supercritical H?0
D001 D002 D003
XXX
X
X
X
X
X
X
X
X
F001-002
X
X

X
X
X
X*
X
X*
F003-005 K049 K051 PCB
X XXX
XX X
X
X X
X
X X

X X

*  In Aqueous Solutions
                                     15

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HIGH TEMPERATURE ELECTRIC REACTOR



     This process utilizes a vertical  reactor heated by  electrodes  implanted



in the walls to pyrolize organic wastes.  The process is offered by two



companies, Thagard Research, which developed the process,  and Huber



Corporation, which acquired rights to the process and introduced several



modifications.



     The process utilizes a reactor with a core enclosed by porous  refractory



material.  Carbon electrodes implanted in the wall  of the reactor heat



the reactor core to radiant temperatures.  Heat transfer is accomplished



by radiation coupling from the core by means of a gaseous blanket formed



by flowing nitrogen through the walls of the core.   In the process  organic



compounds are rapidly heated to temperatures in the range of 3800°  -



440U°F and destroyed.



     In the Huber process product gas and waste products pass through



two port  reactor treatment zones which provide for additional exposure



to high temperatures and for product gas cool down.



Suitable  Wastes



     The  process is primarily designed to pyrolize organics attached to



particulates  such as carbon black or soil.  However, the developer claims



that recent tests have shown the process is also effective for liquid



refractory waste streams  such as carbon tetrachloride.



Throughput/Capacity



     The  Huber  unit will process from 75 to 125 pounds of contaminated



solids per minute.  Hard  numbers are not available  for pure  liquids.



However,  capacity would be  less.
                                      16

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Costs
     Costs information is not available.   However,  the Huber Corporation
claims the cost of operating a unit is comparable to conventional  incineration.
Anticipated Date of Commercialization
     Mid summer 1985.
Environmental  Data
     Huber recently completed a test of the process which showed that  DRE's
far in excess of the 99.99% RCRA requirements can be obtained.
MOLTEN SALT
Process Description
     Molten-salt destruction is a method of burning organic material while,
at the same time scrubbing in situ any objectionable byproducts of that
burning and thus preventing their emission in the effluent gas stream.
This process of stimulating combustion and scrubbing is accomplished  by
injecting the material to be burned with air or oxygen-enriched air,
under the surface of a pool of molten sodium carbonate.  The melt is
maintained at temperatures on the order of 90U°C, causing the hydrocarbons
of the organic matter to be immediately oxidized to carbon dioxide and
water.  The combustion byproducts, containing such elements as phosphorous,
sulfur, arsenic and the halogens, react with the sodium carbonate.  These
byproducts are retained in the melt as inorganic salts rather than being
released to the atmosphere as volatile gases.  In time, inorganic products
resulting from the reaction of organic halogens, phosphorous, sulfur,
etc., build up and must be removed from the molten bed to retain its
ability to absorb acidic gases.  Ash introduced by the waste must be
removed to preserve the fluidity of the melt.  An ash concentration in
the melt of about 2U% by weight provides an ample margin of safety to
maintain melt fluidity.
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Suitable Wastes



     The Molten Salt process is designed for solid and liquid waste streams.



It is especially applicable to highly toxic wastes and to highly halogenated



waste streams.  Waste streams with high percentages of ash and non-combustibles



are not very good for the system since such waste makes it necessary to replace



the molten bed more often.



Process Throughput



     A new pilot scale facility capable of processing 80 to 200 pounds of



waste per hour has recently been constructed.  No commercial scale units have



been built to date.



Costs Per Unit Processed



     No cost data available.



Anticipated Date of Commercialization



     This process has been demonstrated successfully with many different



liquids and slurries, and is currently available for commercial use.  No



commercial units are currently operational.



Environmental  Impacts



     A variety of chemical wastes have been successfully incinerated in



bench-scale molten salt combustors.  Destruction efficiencies for organic



chemicals, pesticides and chemical warfare agents ranged from 99.99% to



99.999999%.  Tests were performed by Rockwell International for the State



of California  (2).



PLASMA ARC TECHNOLOGY



     One of the emerging technologies receiving much attention is plasma



arc technology, which is a process using the extremely high temperatures



of plasmas to  destroy hazardous waste.
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     A plasma is a substance consisting of  charged  and  neutral  particles



with an overall charge near zero.  A plasma arc is  generated  by electricity



and can reach temperatures up to bO.OUQOF.   When applied  to waste  disposal,



the plasma arc can be considered as an energy conversion  and  energy



transfer device.  The electrical energy is  transformed  into a plasma.   As



the activated components of the plasma decay, their energy is transferred



to the waste materials exposed to the plasma.  The  wastes are ultimately



decayed and destroyed as they interact with the decaying  plasma.



     In a mobile prototype of a patented process, a five  hundred kilowatt



plasma device is fitted to one end of a stainless steel reaction chamber



and mated to a hollow graphite core to form an atomization zone.  Residence



time in this atomization zone is approximately five hundred micro-seconds.



The reaction chamber serves as the equilibration zone where the atomized



species recombine to form new simple non-hazardous products.    This  zone



is equilibrated at a temperature range of 1200-1800 Kelvin and the residence



time in this zone is approximately one second.  All hardware  is designed



to be located within a forty five foot long moving van  type trailer.



Suitable Waste Streams



     Plasma arc technology is designed for highly toxic liquid waste streams,



The operation of the process is not significantly impacted by the degree  of



halogenation of a waste stream.



Process Throughout



     A unit currently being demonstrated through partial  support of  the



Agency will process 600 Ibs. of waste per hour.  This unit is sized  to be



operated commercially.
                                      19

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Cost Per Unit of Waste Processes



     Cost figures not  available.



Analytical Date of Commercialization



     A commercialization scale unit  is to be operating within  1-3 years.



Environmental Data



     No environmental  data from a  commercial  scale  unit is  currently



available.  A current  demonstration  in the State of New York is to produce



information on destruction efficiency, and characterization of emissions.



MET AIR OXIDATION



Process Description



     Wet air oxidation is a process  for oxidizing organic contaminants  in



water.  Wet air oxidation refers  to  the aqueous phase oxidation of dissolved



or suspended organic substances at elevated temperatures and pressures.



Water, which makes up  the bulk of the aqueous phase, serves to modify



oxidation reactions so that they  proceed at relatively low temperature



(350°F to 650°F) and at the same  time serves to moderate the oxidation



rates removing excess  heat by evaporation.  Water also provides an excellent



heat transfer medium which enables the wet oxidation process to be thermally



self-sustaining with relatively low  organic feed concentrations.



     An oxygen-containing gas, usually air, is bubbled through the liquid



phase in a reactor used to contain the process, thus the commonly used



term "wet air oxidation"  (WAO).  The process pressure is maintained at  a



level high enough to prevent excessive evaporation of the liquid phase,



generally between 300 and 3000 psi.
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     A wastewater stream containing oxidizable  contaminants  is  pumped  to



the system by means of a positive displacement-type pump.  The  wastewater



passes through a heat exchanger which  preheats  the  waste by  indirect heat



exchange with the hot oxidized effluent.   The temperature  of the  incoming



feed is increased to a level  necessary to support the oxidation reaction



in the reactor vessel.  Air and the incoming liquid are injected  into  the



reactor where the oxidation begins to  take place.   As oxidation progresses



up through the reactor, the heat of combustion  is  liberated, increasing



the temperature of the reaction mixture.   This  heat of oxidation  is



recovered by a heat exchange that utilizes the  incoming feed.  Thus  it is



thermally a self-sustaining operation.  After energy removal, the oxidized



effluent, comprised mainly of water, carbon dioxide, and  nitrogen is



reduced in pressure through a specially designed automatic control  valve.



     Of all variables affecting wet air oxidation,  temperature  has the



greatest effect on reaction rates.  In most cases,  about  300°F  is the



lower limit for appreciable reaction,  about 4B2°F  is needed  for reaction



to the 80 percent reduction of Chemical Oxygen  Demand (COD)  range, and at



least 572°F is needed for 95 percent reduction  of  COO or  better reaction



within practical reaction time.



     The use of catalysts have been evaluated for  improving  the destruction



efficiency of WAO.  However, there are no commercial application  of UAO



utilizing a catalyst at the present time.
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Suitable Wastes



     The process is designed primarily for very  dilute  aqueous  wastes



which are too dilute to incinerate economically  yet too toxic to treat



biologically.  WAO also has application for inorganic compounds combined



with organics.  It is not very effective in oxidizing highly refractory



chlorinated organics.



Process Throughput



     An existing unit is being demonstrated on various  waste streams in



California.  This unit can process up to 10 gallons per minute.



Cost Per Unit of Waste Processed



     A cost range of b cents to 1U cents/gallon  of waste processed is  cited



by one of the developers of a wet oxidation process. These costs are for



the 1U gallon per minute system.  Costs for larger systems are not available.



Anticipated Date of Commercialization



     Technology is available now.  Wider adoption could occur within the



next two years, however, application would be limited to aqueous wastes



that cannot be economically incinerated.  Adoption will also depend on



the destruction efficiency and whether post treatment is required.



Environmental Effects



     Limited environmental data from bench-scale tests  is available.



However, the USEPA-ORD, under a cooperative agreement with the State of



California, is currently evaluating a full-scale (10 GPM) unit (3).  All



of the full scale tests have not been completed; wastes being tested



include:  cyanide wastes, phenolic wastes, sulfide wastes, non-halogenated



pesticides and solvent still bottoms.
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MOLTEN GLASS INCINERATION



Process Description



     The integral  part of this process is an electric furnace approximately



22' long and 3' wide that has a pool of molten glass covering the bottom.



This type of furnace is used extensively in the glass manufacturing  industry



to produce glass.   When used as a waste incinerator the extremely high



temperatures in the combustion chamber destroy organic waste streams.



     Waste materials, both combustible and non-combustible,  are charged



directly into the  combustion chamber above the pool of molten glass.  The



waste can either be contained in fiberboard boxes, or uncontained in loose



form.  Electrodes  immersed in the pool maintain the temperature of the



pool of molten glass above 2300° (1260°C).  Combustible waste are oxidized



above the pool, and inorganics and ash fall onto the pool  where they are



melted into the glass.  Combustion off gases pass through  ceramic filters



which are themselves charged into the molten glass when they are no



longer effective.



Suitable Wastes



     Any combustible waste is acceptable.  Degree of halogenation is not a



consideration.  However scrubbers will be required for HC1 emissions.



Process Throughput



     Since this technology is used in the glass manufacturing industry,



existing units are capable of processing from 10U pounds per hour to 21,000



pounds of raw materials per hour.  However these have not  been demonstrated



as devices for destroying hazardous wastes.
                                     23

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Cost Per Unit of Waste Processed



     No cost figures were available.



Environmental Effects





     Although no actual  data on hazardous waste is  available,  the fact



that the unit uses ceramic filters for air emissions and encapsulates the



inorganic residues in a glass slag seems to indicate that environnental



emissions would be minimal and at least comparable to incineration.



However, this remains to be tested.



SUPERCRITICAL WATER



Process Description



     In the supercritical water process an aqueous waste stream is subjected



to temperatures and pressures above the critical point of water, i.e. that



point at which the densities of the liquid and vapor phase are identical.



(For water the critical point is 379°C and 218 atmospheres).  In this super-



critical region water exhibits unusual properties that enhance its capability



as a waste destruction medium.  Because oxygen is completely miscible with



supercritical water, the oxidation rate for organics is greatly enhanced.



Also inorganics are practically insoluble  in supercritical water.  This



factor  allows the inorganics to be easily  removed from the waste streams.



The  result  is that  organics  are oxidized extremely  rapidly and the resultant



stream  is virtually free of  inorganics.



     A  patented process has  been developed that  incorporates the properities



of  supercritical  fluids to  oxidize organic contaminants  in aqueous streams.
                                      24

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     The following is a brief summary of the process.



     a.  Waste is slurried with make-up water to  provide  a  mixture  of  5



         percent organics.  The mixture is heated using  previously  processed



         supercritical  water and then pressurized.



     b.  Air or oxygen is pressurized and mixed with  the  feed.   Organics  are



         oxidized in a rapid reaction.  (Reaction time is less  than 1  minute.)



         For a feed rate of 5 percent by weight of organics,  the heat  of



         combustion is sufficient to raise the oxidizer effluent to 500°C.



     c.  The effluent from the oxidizer is fed to a salt  separator  where



         inorganics are removed by precipitation.



     d.  Waste heat from the process can be reclaimed to  provide sufficient



         energy for power generation and high pressure steam.



Suitable Waste Streams



     Supercritical water processes are designed for aqueous waste streams



with high levels of inorganics and toxic organics.  The  system's capability



for treating aqueous waste streams with high percentages  of halogenated



material has not yet been demonstrated.



Process Throughput



     A unit is currently being demonstrated to treat  from 1,000 to  2,000



gallons per day of aqueous wastes.



Cost Per Unit of Waste Processed



     No cost figures are available.



Anticipated Date of Commercialization



     The developer of the system claims that commercial  scale units will



be available in 1-3 years.
                                      25

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Environmental  Impact



     Bench scale tests on a variety  of hazardous  materials  have  indicated



ORE's of 98.5 to 99.8.  A demonstration unit is currently being  evaluated



by industry, and will  generate environmental data for a larger unit.





BIOLOGICAL TREATMENT



     Biological treatment encompasses the use of living organisms  or  their



by-products, such as enzymes, to effect destruction or detoxification of



hazardous waste.  Procedures ranging from acclimation to genetic engineering



are used to develop appropriate organisms to accomplish the degradation



process.  In most cases a "reactor" of some type is constructed  to provide



a suitable environment for the required biochemical reactions.   The



reactor may be as simple as a storage lagoon or as complex as a  fermentation



tanks, with ability to control temperature, pH, moisture, nutrients,



oxzygen, off-gases, mixing with the waste and/or separation from the



treated material.   Land treatment and composting are low tech applications



of biological  treatment.  Most biological treatment systems are suitable



only  for treatment  of  very dilute aqueous wastes  (organic content <1% by



weight) or  for detoxification of contaminated  soils or sediments, especially



when  the  detoxification  can  be accomplished while  leaving the soil or



sediment  essentially  in place.  No  significant use of  biological treatment



for  combustible  liquid hazardous wastes  is  anticipated in the foreseeable



future.



      The  potential  environmental impacts of biological  treatment are numerous



and  sometimes  difficult  to predict.  Biological  processes tend  to be slow,



thus  contaminants  with even  low to  moderate volatility can  be transferred
                                      26

-------
to the atmosphere from lagoons, composting facilities, land treatment or



spray irrigation.  Pollutant transfer by air stripping is  an important



concern in any aerated biological treatment process.  Even very low



levels of some toxic compounds may remain in biological  treatment  residuals



could warrant regulation.  The pollutants are too dilute to be effectively



used as a food source by suitable organisms in activated sludge,  composting,



anaerobic digestion or land treatment systems.  The eventual use  or



disposal of the biological  residuals thus becomes a hazardous waste



concern.  The complexities of biological processes result  in frequent



upset or out of control  conditions and corresponding reductions in pollutant



removal efficiencies.  Such excursions could not be tolerated when treating



hazardous wastes.  Finally, estimating the environmental impacts  of



introducing genetically engineering organisms into the open environment



is a difficult and controversial  problem.  It is unlikely  that biological



treatment based upon genetically engineered organisms will rapidly develop



for commercial use.



Chemical Treatment



     Major chemical treatment processes applied to hazardous waste include



chemical oxidation or reduction,  hydrolysis, neutralization and photolysis.



Precipitation as a separation technique may be accomplished by using one



or more of these treatment processes.  Common applications for hazardous



waste treatment are oxidation of  phenol or cyanide in aqueous wastes,



neutralization of corrosive wastes such as pickling liquors or caustic



wastes, and detoxification of contaminated soils.  Combustible liquid



hazardous wastes are generally not good candidates for chemical treatment,



although dehalogenation may in special cases result in the recycling or



recovery of a waste.
                                      27

-------
Cost and environmental  impact are important considerations  in  applying



chemical treatment technology.



     The cost of reactants can be significatn if large quantities  of the



target pollutant are to be processed.  Often, large doses of reactants



are necessary to destroy even low concentrations of hazardous  constituents,



because of interference from non-hazardous components or, as is often the



case with ozonation, the difficulty of effectively mixing the  reactants



with the waste to achieve stoichiometric amounts of oxidant.  For  example,



the necessity of using large doses of degalogenating chemicals on  dioxin



contaminated soils presents a current research problem of how the



dehalogenation reaction can be enhanced to effectively use near stoichiometric



amounts of reactants.



     Operational and capital costs are also a factor.  Energy  requirements



and thus costs increase as additional temperature and pressure are



required.  As a result, capital costs also increase because high temperature,



pressure and corrosivity mandate the use of exotic construction materials.



     Chemical treatment poses several problems with regard to environnental



impact.  The safety of reactions which produce heat or emit gases can be



a significant problem.  Also, the reaction by-product may be hazardous.



The process may also cause disposal problems, because adding chemicals to



waste often increases the amount of material ultimately requiring disposal.



Eventhough these detoxified  residuals are non-hazardous, their disposal



would be costly and could present a public relations problem.



     Therefore, in terms of  cost and environmental impact,  incineration



of combustible hazardous waste will continue to have advantages over



chemical processes currently  being used or under  development.
                                       28

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                               REFERENCES

 EPA 530/SW-84-005, April  1984; "National Survey of Hazardous Waste
 Generators and Treatment, Storage and Disposal  Facilities Regulated
 under RCRA in 1981".

 EPA/California Cooperative Agreement R808908, August 1981; "Molten
 Salt Destruction Process:  An Evaluation for Application in California",

 EPA/California Cooperative Agreement Project, "Demonstration of
 Wet Air Oxidation of Hazardous Waste", Proceedings of Tenth Annual
 EPA Hazardous Waste Research Symposium, April 1984.
                                   32
GPO 914-025

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