k. 600287093
PROJECT SUMMARY
REPORT ON DECONTAMINATION OF PCB-BEARING SEDIMENTS
by
Donald L. Wilson
Chemical & Biological Staff
' Chemical & Biological Detoxification Branch
Alternative Technologies Division
Hazardous Waste Engineering Research Laboratory
Cincinnati, OH 45268
HAZARDOUS WASTE ENGINEERING RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
'' H, Environment.?] Protr-ntlori Agency
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PROJECT SUMMARY
Introduction;
Polychlorinated biphenyls (PCBs) have in the past been widely used as a
dielectric fluid in transformers and capacitors as well as in hydraulic and
heat-transfer fluid systems because of their stability and heat resistance.
During the 50 years that PCBs were manufactured and used in this country, an
estimated 400 million pounds of these chemicals entered the environment.
Because of the broad use of PCBs (ranging from transformer dielectric oils to
carbonless paper production), they are widespread in the modern environment,
especially the aqueous environment.
Although PCBs are a suspected carcinogen, their acute toxicity is consid-
ered to be non-to slightly toxic by the LD50 Method. A more significant health
impact has been linked to the incomplete combustion (burning) of PCBs. Under
certain circumstances, oxidation of PCBs form dioxins and furans, most toxic of
all man-made substances. While PCBs have long been known to be toxic, they have
only recently been acknowledged to be a general threat to the environment. The
characteristics that make PCBs such a problem is their stability and therefore,
persistence in the environment. These chemicals have been found in measurable
concentrations in waterways and sediments through the world and are widely
spread contaminants of fish and wildlife resources. The PCBs contamination
results from an era when industrial wastes were disposed of by flushing them
directly iflto waterways, local ..sewage plants or landfills.
The PCB contamination problems in New Bedford, Massachusetts (EPA Region I),
the Hudson River in New York (EPA Region II), and in Waukegan, Illinois (EPA
Region V) are reported to be the worst in the United States in terms of concen-
tration and total quantity of PCBs. It is estimated that 290,000 kg of PCBs are
contaminating 382,000 M 3(500,000 yd 3) of sediments of the Hudson River. Dur-
ing the 70's approximately 907,000 kg of PCBs were used in the New Bedford area
annually, of which an estimated 45,500 kg were improperly disposed. Also, there
are numerous industrial lagoons contaminated with large quantities of PCBs. For
example, EPA Region III reports three sites in Pennsylvania and two in West
Virginia where over 3200 2447 m3 yd3 of soil/sediments are contaminated with PCBs.
The PCBs contamination problems pose threats to both drinking water and the
fishing industry.
The only available proven technology is dredging and expensive incineration.
Land disposal of the untreated sediments has legal restrictions. Biodegradation
is a possibility, but sufficient information does not exist to design and operate
such a system. There is little experience in the application of encapsulation
technology to PCB-contaminated sediments.
Although a great amount of work has been done by many research groups in
-the area of PCB-contaminated liquids, relatively little effort has been directed
toward PCB-contaminated sediments and sludges. The EPA Regional and Program
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rnmment on the technical and economic feasibility
"oT"cKemical/ biological processes for clean-up of tnese_sediment5 and sludges^
The&tf OfTices do not have adequate data to recommend any of a number of processes
proposed or being tested/evaluated for the decontamination of sediments contain-
ing PCBs.
Assessment of Processes
Because there is little known about the application of chemical and
biological processes to the decontamination of PCBs in sediments, Research
Triangle Institute (RTI) was engaged by EPA to undertake a study to identify
the most technically feasible processes that have been proposed by research
concerns for the removal of PCBs from sediments; to identify their extent of
development, effectiveness, limitations and probable costs; and to determine
needs for their further development. The study involved three phases: identi-
fication of the most promising processes and their further development needs;
evaluation of the unit operations involved in the processes against engineering,
health, and environmental criteria for further testing and evaluation; and
definitive assessment of the recommended treatment processes using pilot systems
and contaminated sediments.
The first phase involved four steps: data acquisition, screening and selec-
tion of most technically feasible processes, development of criteria for process
assessment, and process assessment. Under step one, three major sources of data
were: EPA's file of proposals and correspondence concerning problems of PCB
contamination and possible approaches to alternative solutions; the open litera-
ture; and_ direct contacts with proponents of treatment technologies. In step
'two, the *procesVe'S''*we1"e' categorized according to- their generic technology ; so •-
that their potential performance could be judged appropriately. Processes with
undesirable aspects, for example lack of tolerance for water, were rejected
from further assessment. Criteria for assessment*, step three, were chosen which
relate to a broad range of principles of operation of diverse applied tech-
nologies, yet can be used effectively in comparing one treatment process with
another. Additional factors, specific to a technology, were included to help
portray the inherent strengths and limitations of a process. The seven crite-
ria used and three additional factors were: estimated residual PCB; available
capacity; conditions/limitations; concentration range handled; status of develop-
ment; test and evaluation data needs; estimated cost; unit operations; RCRA
waste generated; and estimated destruction/detoxification/removal efficiency.
In the final step, the processes were assessed by characterization and ranking.
Characterization provided for objective comparison of the processes. Ranking
provided a subjective comparison of the processes based on the seven criteria.
In the first phase eleven emerging alternative treatments of the sixty
four processes considered for PCB contaminated sediments were compared and
ranked. Eight candidate treatment processes showed potential as alternatives
to chemical waste landfill and to incineration. Some had been tested on soils;
but none were tested specifically on PCB contaminated sediments. Sediments of
concern differ from soils in several properties that influence the performance
of unit operations involved in the treatment processes.
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The second phase built upon the first phase of the assessment so that EPA
may have more complete information before evaluating any technology in the field
This second phase involved three steps: consulting with the treatment process
developers, technical assessment of the process, and the selection of three of
the processes for thorough test and evaluation. Consultations included visits
to the developers' facilities where further information was developed. The
most recent performance data were reviewed. The availability of the system was
determined. The visits included a checklist of needed information and criteria
for assessment of the processes. The Technical assessment was based upon the
projection of the performance and coTtjJjra large-scale treatment system of
sHffment_ capacity tQ Jtreat an esfTmated 3&Q-flflQjn3of PCB-contaminated Hudson
R'iver sedimentsin2i5__y_eajis_. Specific sample data from Hudsgj^River sediments
~ fnr
ment bv_each process assessed. The processes were compared and rated using the
results of the assessment. Based on composite ratings, three processes showing
the highest rating were recommended for test and evaluation.
The objective of the proposed third phase is to provide EPA with a defensi-
ble thorough test and evaluation of the three alternative treatments selected
in Phase 2. In carrying out this phase. EPA will arrangp tn havp pr.R-c.nntami-
n ajted sediments treated in pilot-scale processing systems selected in Phase 2 .
The~pil"ot tests will evaluatel&erf_Qjmajic£-iindTr flfLLfl concnCTonsT and win be
suj3£0£ledL- by labopatory tests. Confirmation of treatment process effectiveness
will make these processes very viable and cost-effective methods of treating
these hazardous wastes.
The following processes were studied by RTI on Phase 2 of the study:
B.E.S.T.
The Basic Extraction Sludge Treatment (B.E.S.T.) process has been developed
by the Resources Conservation Co. (RCC), 3101 N.E. Northup Way, Belleview, WA
98004. The process uses a solvent having an inverse critica solution point in
water to remove water and oily material from solid matter. It has been applied
to clean-up PCB-contaminated oily sludges at a CERCLA site (General Refining
Site, Savannah, Georgia).
Ultrasonics/Hydrogen - Ozone/UV Technology
The process is based upon simultaneous extraction and treatment of a sedi-
ment slurry with ultrasound (above 20KHz) added to increase rates of dissolu-
tion of the PCB contaminants and reduce coalescence of bubbles of gs reactants.
The treatment is achieved by either ozone/ultraviolet irradiation or hydrogen/
ultraviolet irradiation. The sediments are fed as a slurry containing about
20 wt. percent solids into a mixing tank where predetermined amounts of detergent
and sodium hydroxide are added. The conditioned mix is pumped to the reactor
where the solids are maintained in suspension while the mixture is exposed to
ultraviolet irradiation and ozone (or hydrogen) is added. During this treatment,
microscopic turbulence is produced through ultrasonics. The treated slurry is
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fed into a cyclone where the solids are removed, sampled, and tested to certify
.them for discharge. The separated water is neutralized and also tested before~
discharge.
Bio-Clean Naturally-Adapted Microbial
The Bio-Clean Naturally-Adapted Microbial process has been developed by
Bio-Clean, Inc. Bio-Clean is a company engaged in developing process systems
to clean-up, remove or destroy hazardous chemicals in the environment. The
process utilizes Arthrobacteria sp and/or other naturally-adapted microbes to
destroy PCBs (and related organics) under aerobic conditions.
KPEG with DMSO
Nucleophilic substitution with the KPEG process and the Galson Research Corp,
version (Terraclean-Cl process) was looked at as a means of decontaming PCB-
bearing sediments. The potassium polyethylene glycolate (KPEG) process has two
potential applications in the treatment of PCB-contaminated sediments: The
treatment of the sediments themselves, or the treatment of concentrated PCBs
resulting from extraction processes. The former is assessed in terms of the
Galson Modified KPEG process, that is with dimethyl sulfoxide (DMSO). The
latter application would require treatment of a relatively concentrated solution
of PCBs in a non-aqueous solvent (triethylamine, kerosene, etc.).
CFS Propane Extraction
The CFS Propane Extraction Process is a technology available from C. F.
Systems Corporation, 25 Acorn Park, Cambridge, Massachusetts 02140. The company
is a subsidiary of Arthur D. Little. As applied to PCB-contaminated sediments,
the process uses propane at ambient temperature and 1378 kPa (200 lb/in2) to
extract PCBs along with other oily organics from a water slurry of the sediment.
The treated slurry is discharged after separation from the liquid propane which
contains dissolved contaminant. The propane solution is fed to a separator
where the solvent is removed by vaporization and recycled. The contaminants
are drawn off as a concentrate for final treatment. The process has been tested
for PCB-containing refinery sludge. The PCB content of the solids component of
the sludge was reduced to-S-ppm-s— ~
Modar Supercritical Water - Oxidation
The process has been developed by MODAR, Inc., 3200 Wilcrest, Suite 220,
Houston, Texas 77042. The process utilizes water above critical conditions
(374°C and 22.1 MPa) to increase the solubility of organic materials and
oxygen and effect a rapid oxidation, destroying organic contaminants. It has
been applied to destroy PCBs in oils, and to decontaminate dioxin tainted soil.
The company has a laboratory test unit and a skid-mounted pilot test unit having
a nominal organic material flow capacity of 190 Liters/day. This unit has bee
operated at MODAR's research facility in Natick, Massachusetts and at the CECOS
International Niagara Falls site.
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In Situ Vitrification
? -» •• In Situ Vitrification was previously discussed-as a process -developed -to ' •
treat radionuclide-contaminated wastes, and subsequently tested for possible
adaptation to the treatment of PCB-contaminated soils. Submerged sediments
would be dredged before treatment. The process stabilizes contaminated soij_s
by melton into a_durable glass andcrysta'Tline form. Four electrodes are
inserted into the sediments in a square array. A~path for electric current is
made by placing a mixture of graphite and glass frit between the electrodes.
Dissipation of power through the starter materials creates temperatures high
enough to melt a layer of sediment, which establishes a conductive path. The
molten zone grown downward through the contaminated soil At the high tem-
peratures created (<1700°C) organic materials pyrolyze, diffuse to the sur-
face, and combust. Off-gases are collected, monitored, and treated.
Solvent Extraction Process
In a separate study, scientists at the New York University's Department of
Applied Science have been carrying on a three year EPA supported investigational
program on the development and evaluation of a low energy process technology
for the solvent extraction and subsequent chemical destruction of PCBs from
contaminated sediments and sludges. This is also one of the processes which was
assessed by RTI in Phase 2. This program involves experimental studies on poten-
tially more cost-effective PCB disposal alternatives to currently accepted
practices. The research activities during the first year of this program
comprised the investigation of suitable solvent extraction and supporting
equipment, identification of candidate solvents for extraction and concurrently
developed^ application and verification of analytical methodology for quantitative
determination of PCBs in contaminated sediments. Exploratory experiments were
also carried out on the extraction of PCBs from contaminated sediments obtained
from Waukegan Harbor, Illinois.
The concept of using kerosene as an extraction solvent for removing PCBs
from sludges and sediments was based on two factors: 1) the low cost of kero-
sene and 2) some work conducted on extraction of PCBs from soils (M. B. Saunders
at Oak Ridge National Laboratory, 1985). While the cost factor is a driving
force in any development, it alone cannot overcome technical impracticalities.
It became quite evident early in this study that the presence of large quanti-
ties of water in the contaminated samples presented an insurmountable
barrier to the use of kerosene in this application. A new approach to
±his difficult problem was needed and is herein presented.
The first step of the process takes advantage of the extremely low solubil-
ity of PCBs in water. In a typical PCB contaminated sediment or sludge composed
primarily of water with generally 20% total solids, virtually all of the PCBs
are associated with the sediment. Thus, the first processing step is a physical
separation of water and solids. In the second step, the PCB contaminated oil
is disociated from the sediment substrate. This is accomplished by a multi-
stage counter-current leaching with a hydrophyllic solvent. The third step is
a stripping operation in which the PCB-containing stream from above is contacted
in a liquid-liquid extractor with a hydrophobic solvent and additional water.
The two streams which leave this step are the PCBs concentrated in stripping
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solvent which proceeds to appropriate methods for final destruction, and the
hydrophyllic solvent/water mixture containing trace PCBs. The solvent/ water
mixture goes next to,a disti 11-ation-colamn-fn-which the solvent Is separated '- "
and returned to the leaching process. The water contaminated with trace amounts
of PCBs is recycled to the front of the stripping process to close the cycle.
Conclusions
Various experimental and supporting activities were carried out during the
first year of the EPA-supported research in order to develop an adequate data
base for achieving an effective low energy process for the extraction of PCBs
from contaminated sediments and sludges. Achievements from these investigations
are summarized as follows:
1. Selection of extraction and supporting equipment for a specific extrac-
tion.
2. Identification of candidate solvent systems for extraction.
3. Development of an appropriate analytical methodology for the deter-
mination of PCBs in contaminated sediments and sludges.
4. Development of an innovative process scheme for the extraction of PCBs
from sediments and sludges.
Emerging treatment processes for decontamination of sediments containing
PCBs that show potential as alternatives to incinceration and chemical waste
landfill have been identified in Phase One of an assessment study. Eleven
alternative treatments were compared and ranked using technical performance,
status of development, test and evaluation data needs, and cost as factors.
The first'eight processes sfrow potential for reduction of PCB concentrations to
the desired background levels (l-5ppm) or less, with minimum environmental
impacts and low to moderate cost. The sediments must be dredged for application
of these treatments. Based on the weighted ratings of Phase One, eleven
processes ranked as follows from highest to lowest: KPEG, LARC, Acurex, Bio-Clean,
Modar-Supercritical Water, Advanced Electric Reactor, Vitrification, OHM Extraction,
Soil ex, Composting, and Sybron Bi-Chem 1006.
At the start of the final assessment study before field tests, some former
developers indicated their processes should not be considered and some new
processes became available. Thus, in the next assessment study-Phase Two, eight
emerging treatment processes for decontamination of P£B-contaminated sediments
were evaluated as candidates for thorough test and evaluation using a test
system of sufficient size to provide performance, co-st, and seale-u-p data for a
large commercial plant. The processes assessed and listed in relative desirability
of test and evaluation include: (1) Basic Extraction Sludge Treatment (B.E.S.T.)
developed by Resources Conservation Co.; (2) UV/Ozone or Hydrogen/Ultrasonics
Technology of Ozonic Technology, Inc.; (3) Bio-Clean Naturally-Adapted Microbial
Process of Bio-Clean, Inc.; (4) KPEG (Galson) Process modified by Galson Research
Corp.; (5) Low Energy-Acetone-Kerosene Extraction Process developed by the Applied
Science Dept. of New York University; (6) Modar Supercritical Water Oxidation
.Process of Modar, Inc.; (7) CFS Propane Extraction Process of C. F. Systems Corp.;
and (8) In-Situ Vitrification Process by Battelle Pacific Northwest Research
Laboratories.
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Recommendations
While all the processes except In Situ Vitrification appear to merit
further development for this application, those three with the highest compar-
ative ratings are recommended for EPA-supported thorough test and evaluation.
These are the Basic Extraction Sludge Treatment, UV/Ozone or Hydrogen/Ultrasonics
Technology, and Bio-Clean Naturally-Adapted Microbe processes.
There is, in an evaluation of processes such as this, much uncertainty.
Additional research of the other processes is very important to fill in the
data gaps. The other processes, for example, may be more cost effective on a
smaller scale than what the study assumed or with other unit processes. The
results of the EPA funded study at the New York University have led to a novel
approach to treatment of PCB-contaminated sediments and sludges. It is
recommended that a study is needed to model, engineer and otherwise fully
characterize this process so that its full potential might be realized.
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REPORT ON DECONTAMINATION OF PCB-BEARING SEDIMENTS
by
Donald L. Wilson
Chemical & Biological Staff
Chemical & Biological Detoxification Branch
Alternative Technologies Division
Hazardous Waste Engineering Research Laboratory
Cincinnati, OH 45268
HAZARDOUS WASTE ENGINEERING RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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NOTICE
This report has been reviewed by the Hazardous Waste Engineering Research
Laboratory, U.S. Environmental Protection Agency, and approved for
publication. Approval does not signify that the contents necessarily reflect
the views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
ii
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FOREWORD
Today's rapidly developing and changing technologies and industrial prod-
ucts and practices frequently carry with them the increased generation of solid
and hazardous wastes. These materials, if improperly dealt with, can threaten
both public health and the environment. Abandoned waste sites and accidental
releases of toxic and hazardous substances to the environment also have impor-
tant environmental and public health implications. The Hazardous Waste Engineer
ing Research Laboratory assists in providing an authoritative and defensible
engineering basis for assessing and solving these problems. It's products
support the policies, programs and regulations of the Environmental Protection
Agency, the permitting and other responsibilities of State and local government
and the needs of both large and small businesses in handling their wastes
responsibly and economically.
This report describes an in-depth assessment of emerging alternative treat-
ment processes that show potential for decontaminating polychlorinated biphenyl
(PCB)-contaminated sediments and the selection of processes for thorough test
and evaluation. The comparison of these processes as to their technical per-
formance, the availability of a test system, the test and evaluation effort
required, the projected time to commercial availability, and the probable cost
of their application should be useful to EPA Regional Offices, to those con-
cerned with developing hazardous waste treatment regulations, and to those
interested in the development of new and innovative treatments.
For further information, please contact the Alternative Technologies
Division of the Hazardous Waste Engineering Research Laboratory.
Thomas R. Hauser, Director
Hazardous Waste Engineering
Research Laboratory
iii
v
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ABSTRACT
In recent years, polychlorinated biphenyls (PCBs) have been discovered
as contaminents in sediments throughout the country. Conventional and emerg-
ing waste management methods have not been evaluated for decontamination of
PCB-bearing sediments.
The EPA has initiated a research program to Identify chemical/biological
methods as alternatives to incineration and to chemical land disposal for clean-
up of PCB contaminated sediments. The overall objective of the program is to
identify, validate, and demonstrate effective and economical chemical/biological
processes for removal/destruction of PCBs in sediments. This report summarizes
research progress on chemical/biological methods development for the detoxif-
ication/destruction of PCBs in sediments.
iv
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CONTENTS
Notice ii
Foreword 1 i i
Abstract i v
Tables vii
1. INTRODUCTION 1
PCBs in Sediments 3
Solvent Extraction Process 4
Assessment of Processes 5
2. CONCLUSIONS 9
3. RECOMMENDATIONS 12
4. DISCUSSION ON EXTRACTION PROCESS 14
Selection of Equipment 14
Survey of Industrial Extraction Equipment 14
Settler Design 16
Contractor Selection 17
Experimental Studies 19
Extraction of PCBs from Spiked Water Samples 19
Quantification of PCBs in Environmental Sample 19
Characterization of Solvents 20
New Process Devel opment 21
5. DISCUSSION OF ASSESSMENT STUDY 23
Screening of Processes 23
Development of Evaluation Criteria 28
Problem Definition 28
Regulatory Factors 28
Technical Factors 28
Cost Est imates 29
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CONTENTS (continued)
Initial Assessment of Processes 31
Processes Based on Chemical Technologies 31
Processes Based on Physical Technologies 38
Processes Based on Biological Technologies 41
Initial Characterization and Ranking of Processes 45
Character^ zati on 45
Ranki ng 48
Final Assessment of Processes 53
Ranki ng Cri ten' a 53
B .E .S .T 55
Ultrasonics/Hydrogen-Ozone/UV Technol ogy 56
Bio-Clean Naturally-Adapted Microbial 57
KPEG with DMSO 57
CFS Propane Extraction 59
Modar Supercritical Water-Oxidation., 59
Low Energy Acetone-Kerosene Extraction 60
In Situ Vitrification 60
Selection of Three Processes 62
APPLICATION OF PROCESSES TO RCRA WASTES 70
VI
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TABLES
Number Page
1 Basic Classification of Industrial Contactors 14
2 Summary of Features and Fields of Application 15
3 PCB Concentration of Waukegan Harbor Sludge 20
4 Screening of PCB Treatment Processes 24
5 Unit Cost Estimates 30
6 Treatment Processes Characteristics 46
7 Treatment Processes Ranking 51
8 Acceptable and Borderline Values for Processes
Characteristics . 62
9 Overall Desirability of Immediate T and E of the Seven
Candidate Processes . . 64
VII
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SECTION I
INTRODUCTION
Polychlorinated biphenyls (PCBs) are a class of compounds that have 209
combinations of chlorine atoms attached to the biphenyl molecule. When they
^ere first introduced into the United States by the Monsanto Company in 1929,
PCBs were considered a "wonder" chemical. PCBs are clear, odorless liquids
which have thermal, biological and chemical stability, plus high dielectric
constants. These characteristics made PCBs have widespread use. Initially,
PCBs were used as dielectric fluids in capacitors and transformers. A small
amount was used in electromagnets, heat transfer and hydraulic systems. PCBs
applications spread to plasticizers in paint, adhesives, dry caulking compounds,
carbonless paper, flame retardants and fillers of all sorts.
Between 1929 and 1975, over 1.25 billion pounds of PCBs have been manu-
factured and used in the U.S., primarily in mixtures with chlorobenzenes (mostly
trichlorobenzene or TCB) known as askarel (typical 40% PCB and 60% TCB). Askarels
were used as dielectric fluids for electrical equipment and consisted of about
77% or 965 million pounds of the PCBs produced. It is estimated that 328 million
pounds remain in service in electrical systems.
These compounds were not discovered in the environment until 1966 in
Sweden and 1967 in the U.S. despite their use commercially for about 40 years.
Interest in PCBs arose because they were frequently found in fish, bird, water,
sediment and other environmental samples when such samples were examined for
chlorinated pesticide residues.
Although PCBs have long been known to be toxic, only in recent years have
they been acknowledged to be a general threat to the environment. Extensive
research>has shown a link between PCBs and chronic (longterm) effects in many
species at less than lOppm. There are well-documented tests on laboratory
animals that show PCBs cause developmental toxicity, reproduction abnormalities,
and tumors. Even though PCBs are a suspected carcinogen, their acute toxicity
is considered to be non- to slightly-toxic by the LD50 Method. Recently, there
have been additional concerns brought on by the finding of other toxic contami-
nants in PCBs and askarel fluids or linked to their incomplete combustion
(burning). These toxic compounds include polychlorinated dibenzodioxins (PCDDs),
polychlorinated dibenzofurans (PCDFs), chlorinated benzenes and other chlorinated
substances. These compounds are among the most toxic of all man made substances.
Because of these concerns, in 1971, the Monsanto Company, the sole United States
producer, terminated sales of PCBs for all but closed electrical systems uses.
Federal regulations of PCBs took several years to develop. In 1976,
Congress enacted the Toxic Substances Control Act (TSCA), PI 94-469, and included
special provisions, Section 6e, for the regulation of PCBs. In the May 31, 1979
Federal Register 44 (106), the EPA promugated rules which prohibited the manu-
facture of PCBs and their use in almost all nonenclosed applications. Since 1979,
many regulations, rules, modifications to existing .regulations, additional rules,
clarification, and re-evaluated EPA positions have been issued. The position has
moved toward the direction of tighter regulatory control. The Chemical & Bio-
logical Staff conducted a regional survey in early 1987 on the acceptable PCBs
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levels in soils and sediments. There existed some variation between the EPA
Regional Offices on the clean-up policies for spills of TCBs'on soils and
sediments. On April 2, a new policy for cleaning spills of PCBs that sets the
same standards for every region in the country was released by EPA, after two
years of negotiations among the Agency, environmental groups and industry (40
CFR, Part 761, April 2, 1987, pp 10688-10710). The policy calls for decontami-
nation of soil down to lOppm PCBs by weight in residential areas. This soil
would then be covered by a clean-soil cap. Less restricted areas calls for
clean-up down to 25ppm or BOppm. Disposal of treated soils/sediments must meet
the criteria of less than 2ppm PCBs concentration. The regulations permit PCBs
to be landfilled or burned only in special incinerators, cement kilns or boilers,
They also allow the EPA Regional Administrator to approve other alternative
technologies to be used if he finds they do not "present an unreasonable risk of
injury to health or the environment", and if their "level of performance is
equivalent to Annex I incinerators or high efficiency boilers". However, the
March 30, 1983 procedural rule on authority over alternative methods is still in
effect. Under this ruling, incinerators and alternate methods that are mobile
or of identical design and intended to be used in more than one region must
obtain approval from the Assistant Administrator for Pesticides and Toxic
Substances. Also included are certain research and development methods that
dispose of more than BOOlbs of total PCBs or PCB contaminated material. This
report discusses several alternative technologies and their abilities to meet
these regulations.
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PCBs in Sediments
Polychlorinated biphenyls (PCBs) are widely used industrial chemicals
that were never intended for release into the environment, but they have none-
theless been found in rainwater, in human tissue, and in many species of birds
and fish. PCBs are released into the environment by several means. Sewage
outfalls and industrial disposal into waterways are major sources of PCB-contami-
nation. Rivers and streams are primary means of transport for PCBs within the
environment, although the atmosphere also is a means of dispersal. It is esti-
mated that from 1000 to 2000 tons per year escaped into the atmosphere in the
1960s from plasticized materials containing PCBs, and that about 4000 tons per year
entered waterways from dumping and leakage of lubricants, hydraulic fluids, and
heat transfer fluids. Other sources include leaching from dumps and landfills,
where about half of the PCBs produced eventually end up. Once in the environment,
PCBs persist for a long time. Their physical property of low water solubility
caused the PCBs present in waterways to accumulate in sediments.
Reported the worst PCBs-sediment contamination sites in the United States,
in terms of concentration and total quantity, are: New Bedford, Massachusetts
(EPA Region I); Hudson River, New York (EPA Region II); and Waukegan, Illinios
(EPA Region V). It is estimated that 290,000 kg of PCBs are contaminating
382,000 m3(500,000 yd3) of sediments of the Hudson River. During the 70s,
approximately 907,000 kg of PCBs were used in the New Bedford area annually,
of which an estimated 45,500 kg were improperly disposed. Also, there are
numerous industrial lagoons contaminated with large quantities of PCBs. For
example, Jthe following is a partial list of PCBs removals which have occurred
in EPA Region III:
Site Name Site Location Approx. cu.yd. Contaminated
Interstate Transformer Lawrence Co., PA 200
Paoli Railroad Paoli, PA 800
Sandonelle Mercer Co., PA 600
Shaffer Equipment Minden, WV 1600
Frazier's Bottom Putnam Co., WV unknown
These PCB contaminated sites pose threats especially to both drinking
water and the fishing industry. The only available proven technology for PCB
contaminated sediments is to remove them by dredging and using incineration
which is costly. Land disposal of the untreated sediments is an option; but,
as previously noted, this option has many legal restrictions and concentration
limitations. Biodegradation is a possibility, but sufficient information does
not exist to design and operate such a system. There is little experience in
the application of encapsulation technology to PCB-contaminated sediments, plus
the large volumes involved may make it cost prohibitive.
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Although a great amount of work has been done by many research groups
in the area of PCB-contaminated liquids, relatively little effort has been
directed toward PCB-contaminated sediments and sludges. The EPA Regional
and Program Offices are being asked to comment on the technical and economic
feasibility of chemical/biological processes for clean-up of these sediments
and sludges. These Offices do not have adequate data to recommend any of a
number of processes proposed or being tested/evaluated for the decontamination
of sediments containing PCBs. The Hazardous Waste Engineering Research Lab-
oratory (HWERL) past and current research in the area of decontamination of
PCB-bearing sediments is addressed to these Agency needs.
Solvent Extraction Process
Extraction of PCBs from sediments is viewed as an attractive alternative
to either incineration or burial. Solvent extraction processes are defined
to be separation processes in which two immiscible or partially soluble liquid
phases are brought in contact for transfer of one or more components. For
PCBs removal from sediments, one phase will be the sediments containing various
amounts of PCBs. A key element in extraction, the ability of a solvent to
extract a particular solute, is measured by the distribution coefficient.
Choice of solvent must be optimized for maximum separation effectiveness. Low
energy requirements and low/moderate capital costs are some advantageous
features of extraction processes.
PCBs are soluble in most organic solvents and insoluble in water and
polyhydroxy liquids. Because of their polar nature, PCBs are more soluble
in many pdlar solvents than various "hycfrocaYbbns. The characteristics of a
good extraction solvent should include high solubility for the PCBs, also a
low solubility for oils and a considerable solvent power for water. Using
these concepts, experimental studies were initiated about 1980-84 at the
Union Carbide Corp. Nuclear Division, Oak Ridge, TN, on the extraction of PCBs
from contaminated sludges in a lagoon using a hydrocarbon as the extraction
solvent. It is understood that solvents such as hexane, furfural, triethyl-
phosphate, etc. have been investigated in the laboratory. Ultimate disposal of
the extracted PCBs was achieved by incineration. This extraction was used
essentially only for PCBs contamination in a smaller oil volume.
During early 1985, exploratory experimental studies being conducted at
HWERL showed that kerosene is a good solvent for extraction of PCBs from sedi-
ments. The Department of Applied Science, New York University, was engaged to
conduct extensive experimental studies which will develop and optimize the
extraction process. They are to demonstrate both its technical effectiveness
and economic viability with a pilot plant operation. The research activities
during the first year of this program comprised the investigation of suitable
solvent extraction and supporting equipment, identification of candidate solvents
for extraction and concurrently develop application and verification of analytical
methodology for quantitative determination of PCBs in contaminated sediments.
Exploratory experiments were also carried out on the extraction of PCBs from
contaminated sediments obtained from Waukegan Harbor, IL.
\.
.4- -
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In Situ Vitrification
- •» - In Situ Vitrifi-cation was previously discussed as a process -developed -to ' •
treat radionuclide-contaminated wastes, and subsequently tested for possible
adaptation to the treatment of RGB-contaminated soils. Submerged sediments
would be dredged before treatment. The process stabilizes contaminated sojjjs
by melton into a^durable glass andcrystanine form. Four electrodes are
inserted into tTfe sediments in a square array\A~path for electric current is
made by placing a mixture of graphite and glass frit between the electrodes.
Dissipation of power through the starter materials creates temperatures high
enough to melt a layer of sediment, which establishes a conductive path. The
molten zone grown downward through the contaminated soil At the high tem-
peratures created (<1700°C) organic materials pyrolyze, diffuse to the sur-
face, and combust. Off-gases are collected, monitored, and treated.
Solvent Extraction Process
In a separate study, scientists at the New York University's Department of
Applied Science have been carrying on a three year EPA supported investigational
program on the development and evaluation of a low energy process technology
for the solvent extraction and subsequent chemical destruction of PCBs from
contaminated sediments and sludges. This is also one of the processes which was
assessed by RTI in Phase 2. This program involves experimental studies on poten-
tially more cost-effective PCB disposal alternatives to currently accepted
practices. The research activities during the first year of this program
comprised the investigation of suitable solvent extraction and supporting
.equipment, identification of candidate solvents for extraction and concurrently
developed^ application and verification of analytical methodology for quantitative
determination of PCBs in contaminated sediments. Exploratory experiments were
also carried out on the extraction of PCBs from contaminated sediments obtained
from Waukegan Harbor, Illinois.
The concept of using kerosene as an extraction solvent for removing PCBs
from sludges and sediments was based on two factors: 1) the low cost of kero-
sene and 2) some work conducted on extraction of PCBs from soils (M. B. Saunders
at Oak Ridge National Laboratory, 1985). While the cost factor is a driving
force in any development, it alone cannot overcome technical impracticalities.
It became quite evident early in this study that the presence of large quanti-
ties of water in the contaminated samples presented an insurmountable
barrier to the use of kerosene in this application. A new approach to
this difficult problem was needed and is herein presented.
The first step of the process takes advantage of the extremely low solubil-
ity of PCBs in water. In a typical PCB contaminated sediment or sludge composed
primarily of water with generally 20% total solids, virtually all of the PCBs
are associated with the sediment. Thus, the first processing step is a physical
separation of water and solids. In the second step, the PCB contaminated oil
is disociated from the sediment substrate. This is accomplished by a multi-
stage counter-current leaching with a hydrophyllic solvent. The third step is
a stripping operation in which the PCB-containing stream from above is contacted
in a liquid-liquid extractor with a hydrophobic solvent and additional water.
The two streams which leave this step are the PCBs concentrated in stripping
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ination and possible approaches to alternative solutions proved invaluable in
directing the contacts, .for. further information,, .. . ...-.. . , _.,
A bibliography was prepared, which included approximately 100 references
containing information useful in defining potential treatment technologies and
in analyzing treatment process performance data. This bibliography was ex-
panded to 171 references by addition of treatment feasibility study reports,
process test and evaluation reports, process development proposals, and
patents. As processes were identified, direct contacts were made with the
investigators for details of their process studies.
Alternative (non-incineration) destruction/detoxification/removal (D/D/R)
processes were subjected to screening to identify those to be assessed fur-
ther. The processes were categorized according to their generic technology so
that appropriate technical screening criteria could be applied for each. This
screening yielded 11 emerging processes for further assessment. ,The selected
processes represent six different generic technologies.
Criteria used to assess the identified emerging technologies included:
residual PCB concentration in treated sediments, available capacity, condi-
tions/limitations (including range of PCB concentration handled), the develop-
mental status, test and evaluation (T and E) data needs, and estimated cost of
treatment.
The assessment of the different processes required consideration of the
characteristics inherent in the criteria. Their capability to remove PCBs
adequately*from wet contaminated sediments, the required processing time, and
process controllability~were all "considered. Available data were examined for
limits on the range of PCB concentrations that could be adequately reduced by
the process to yield a treated sediment eligible for delisting. The status of
development, whether laboratory-scale or pilot-scale, was identified. The
extent of available data - whether showing only tests of the concept or lists
of the unit processes of a pilot-scale process system - was identified. A
preliminary estimate of the cost of applying the process was developed in
conjunction with the Developer.
Because the processes identified were at various stages of development,
data deficiencies exist, and engineering judgement was used to supplement
available information.
Using the information obtained and developed, the characteristics for each
process were given subjective ratings relative to an arbitrarily-defined per-
fect process. These ratings were then weighted and summed to give a single
number that could represent the overall relative rating of each process.
The product or report from this study is entitled "PCB Sediment Decon-
tamination-Technical/Economic Assessment of Selected Alternative Treatments",
600/2-86-112, Dec. 1986 (PB87-133112/AS). Section 3 of this report describes
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the screening of alternative technologies for technical feasibility to treat
PCB-contaminated sediments. Section 4 describes the development of criteria
to assess selected processes. Section 5 describes the assessment of the
processes, including descriptions, analyses of performance potential, and cost
estimates. Section 6 summarizes the characteristics of the selected processes
and ranks them subjectively. Section 7 presents a bibliography of references
used and other relevant sources. Contacts with developers of the processes
are noted throughout the text.
In November of 1986, HWERL funded a second phase study with RTI. The
purpose of this study is to establish suitable factors for further assessment
of the candidate processes that have been identified, to review these processes
against these factors and identify additional data needs, and to provide a basis
for the selection of three processes for a defensible, thorough technical assess-
ment (including laboratory experiments and field validation) in a third phase
of assessment.
This study builds upon the first phase of the assessment so that EPA may
make better use of funds by having more complete information before evaluating
any technology in the field. Factors considered include: (a) combinations of
unit processes, for example, a solvent extraction process combined with KPEG
or incineration; (b) engineering evaluation criteria; and (c) specific data
needs for full test and evaluation of the applicability of the processes.
The study involved three phases: consultations with the treatment process
developers, technical assessment of the process, and the selection of three of
.the processes fp.r^t.hp.ro.ush.te.st. and_evaljjattpn. :,, , ^_^__ .- „
Consultations Included visits to the developers' facilities where further
information was developed. The most recent performance data were reviewed.
The availability of a system for test and evaluation was determined. The
likely future commercial availability was also determined. Preparations for
the visits included a checklist of needed information and criteria for assess-
ment of the processes. The checklist is based upon the information needs for
a permit to test application.
Technical assessment of the processes was based upon the projection of
the performance and cost of a large-scale treatment system of sufficient
capacity to treat an estimated 380,000 m3 of PCB-contaminated Hudson River
sediments in 2.5 years. Sediment characteristics that may influence the per-
formance of an alternative treatment process were considered. Specific sample
data from Hudson River sediments were used to guide the projection of operating
conditions required for treatment by each process assessed.
In this report, each process is described as it would be applied to the
treatment of sediments. Material and energy balances are applied to the extent
possible with the limited data available. Needs for further data are identi-
fied by type, estimated time, and cost for their acquisition.
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The probable cost of treatment after demonstration and approval of the
process is estimated. Cost elements given include: capital, energy, labor,
maintenance, process quality control and testing. The capital cost is recov-
ered over the 2.5 years of projected operation. Labor and profit/contigency
are estimated at uniform rates for all processes for purposes of comparative
evaluation.
Environmental and health characteristics assessed include all process feed
and waste streams, reagents, and operating hazards.
The lapsed time required to demonstrate process performance, then to design,
construct and check out a full-scale process is projected, based on needs for
additional data and requirements of the developers.
The processes are compared and rated using the results of the assessment.
Based on composite ratings, three processes showing the highest rating are
recommended for immediate test and evaluation.
This report also discusses a phase three study to determine the effective-
ness of the three selected alternative treatment processes to detoxify PCB-
contaminated sediments representative of those present in substantial quantities
in several U.S. lagoons and waterways. The purpose of this phase three effort
is to build upon the second phase of the assessment so that EPA has a defensible,
thorough test and evaluation of three alternative treatments selected in phase
two for PCB-contaminated sediments. Arrangements will be made to have PCB-
contaminated sediments treated in pilot-scale processing systems. These pilot
tests will evaluate performance under field conditions, and will be supported -
by laboratory tests.
\
8
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SECTION 2
CONCLUSIONS
Exploratory studies have established that the extraction of PCB-con-
taminated sediments can be done with readily available low cost reagents
such as acetone and kerosene. These extractions can be carried out at near
ambient temperatures and atmospheric pressures. Specific conclusions reached
from the solvent extraction investigations are summarized as follows:
0 An innovative extraction process scheme was developed to remove PCBs
from sediments.
0 Suitable extracting and supporting equipment was selected and assem-
blied for the newly designed process.
0 Appropriate analytical methodology for the determination of PCBs in
contaminated sediments was developed.
0 Leaching experiments conducted with Waukegan Harbor sludge resulted
in very high effeciencies for the solvents acetone, methanol, and
isopropanol. Kerosene showed much lower effeciencies except in the
case of dry sediments.
0 Settling experiments conducted with dry topsoil containing various
degrees of water gave the following order of settling rate: acetone-
methanol-isopropanol.
Based on the results from the leaching and settling experiments, the find-
ings from the first year of research, and taking into consideration various
physical, chemical and toxicological properties, a solvent pair has been selected.
Acetone has been chosen as the hydrophilic solvent and kerosene the hydrophobic
solvent.
Stripping experiments conducted with these two solvents, with varying
degrees of sulfate concentration, and with varying water/acetone ratios have
given very promising results. A partition coefficient between kerosene and
acetone of 30 has been obtained, which allows for the completion of the stripp-
ing operation with a very small number of stages. An even higher partition
coefficient is expected with further experimentation.
At the end of a Phase I assessment study-for alternative treatment processes
(Dec. 1986) the following conclusions were reached after evaluating sixty four
processes.
Emerging treatment processes for decontamination of PCB-contaminated sedi-
ments that show potential as alternatives to incineration and chemical waste
landfill have been identified. Eight processes -- KPEG, LARC, Acurex, Bio-
Clean, Supercritical Water, Advanced Electric Reactor, Vitrification, and
O.H.M. Extraction -- ranked highest in terms of potential for cleanup of contam-
inated sediments. The sediments must be dredged for application of these treatments,
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Of the 11 processes completely assessed and ranked, all but the Advanced
Electric Reactor (AER) are in various stages of development from laboratory-scale
through field tests. The AER is a permitted treatment based on completed trial
burns.
There is no immediately available capacity for any of the treatments.
Further data are needed in most cases to define the final system design for
the process.
9
At this stage of development,(1985-86) estimated costs for application of
the emerging treatments are less than or within the range of the costs of
chemical waste landfill, except the AER process which exceeds that of landfill.
The ranges of estimated costs (1985 dollars) on the eleven processes ranked are
as follows:
KPEG $ 211 to $ 378/m3
O.H.M. Methanol Extraction 400 to 514/m3
Advanced Electric Reactor 830 to 942/m3
Acurex solvent wash 196 to 569/m3
Bio-Clean 191 to 370/m3
Vitrification 255 to 548/m3
LARC 223 to 336/m3
Modar supercritical water 250 to 733/m3
Soilex solvent extraction 856 to 913/m3
Sybron Bi-Chem 1006 PB unable to estimate cost
Composting unable to estimate cost
Chemical waste landfill 260 to 490/m3
Incineration 1,713 to 1,826/m3
These costs are planning estimates only. In most cases, further research is
needed to provide data suitable for more definite cost estimates.
The emerging treatment processes are based on five different technologies:
one on low-temperature oxidation, two on chlorine removal, one on pyrolysis,
four on removing and concentrating, and three on microorganisms. The four
types of technologies not yielding competitive emerging processes are: chlor-
inolysis, stabilization, bottom recovery, and enzymes. A search of these
technologies yielded no suitable candidate processes.
The Phase II of the assessment study built upon the information gained
during Phase I, but was not limited to those eight processes ranked potentially
high since new ones are always emerging. The closer investigation of the eight
potential processes listed from the Phase I study and four potential processes
recently developed resulted in the following conclusions.
Seven emerging treatment processes for decontamination of PCB-contaminated
sediments are candidates for thorough test and evaluation (T and E) using a
test system of sufficient size to provide performance, cost, and scale-up data
for a large commercial plant. The processes are:
iov
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0 Basic Extraction Sludge Treatment (B.E.S.T.) Process developed by
Resources Conservation Co.
0 UV/Ozone or Hydrogen/Ultrasonics Technology of Ozonic Technology, Inc.
0 Bio-Clean Naturally-Adapted Microbial Process of Bio-Clean, Inc.
0 Potassium Polyethylene Glycolate (KPEG) with dimethyl sulfoxide (DMSO)
Process Modified by Galson Research Corp.
0 CFS Propane Extraction Process of C. F. Systems Corp.
0 Modar Supercritical Water-Oxidation Process of Modar, Inc.
0 Low Energy Acetone-Kerosene Extraction Process developed by the
Applied Science Dept. of New York University.
The processes were evaluated using as criteria:
0 The probability of cleaning sediments to <2 ppm PCBs;
0 The probable cost of treatment;
0 The relative level of Test and Evaluation effort to be supported
by EPA;
v\
0 The availability of a processing system to test; and
0 The likely future commercial availability of the process.
While all the processes merit further development, comparative simul-
taneous evaluation of their ratings on a scale of 0 to 1 gave the following
results:
Relative desirability
Process of immediate T and E
B.E.S.T. 0.62
Ultrasonics/Hydrogen-Ozone/UV Technology 0.62
Bio-Clean Naturally-Adapted Microbial 0.61
KPEG with DMS-G - 0.59
CFS Propane Extraction 0.58
Modar Supercritical Water-Oxidation 0.57
Low Energy Acetone-Kerosene Extraction 0.49
The B.E.S.T., UV/Ozone or Hydrogen/Ultrasonics Technology, and Bio-Clean
Naturally-Adapted Microbial processes have the highest ratings, and are recomm-
ended for immediate, thorough test and evaluation.
11
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SECTION 3
RECOMMENDATIONS
The result of the previous EPA funded study with NYU entitled "Develop-
ment and Evaluation of a Low Energy Process Technology for Extraction and
Chemical Destruction of PCBs from Soils and Sludges" (CR 812123-02-0) has led
to a novel approach to treatment of contaminated soils and sediments with
potentially a much broader applicability. A two year study is proposed to
model, engineer and otherwise fully characterize this process so that its full
potential might be realized. The study will, in the first year, design and
assemble a bench scale working model of the total process. The second year
will culminate in field tests at designated sites. While proof of concept
experiments have established a clear direction for these studies, this is a
complex process which must be analytically modeled to fully appreciate its
potential. Concurrently, engineering design considerations are required to
specify particular equipment. The previous study has considered equipment
which could be used for the different steps of the process. The second year
of the proposed study would address the issues of process scale-up. Equipment
selection and experiment design will follow site analyses and discussions with
the entity responsible for the site clean up.
We have been seeking a commercial sponsor for this process, and it appears
that Camp Dresser & McKee (COM), an environmental consulting firm, is interested
in the EPA/NYU process for future development as it relates to contaminated
sediments originating in New Bedford Harbor, Massachusetts.
The processes compared in Phase I of the technical/economical assessment
study conducted by RTI for HWERL were general technologies and not specific
unit processes within those technologies, nor were they developed to the point
of application to sediments, but rather PCBs in liquids or soils. Thus, a Phase
II study was started which would consider: combinations of unit processes;
engineering evaluation criteria; and specific data needs to evaluate the
applicability of processes. The assessment study is at a stage where data can
be used to commence the longer, more costly Phase III field type investigation.
The purpose of the Phase III effort is to build upon the second phase of
the assessment so that EPA has a defensible thorough test and evaluation of the
three alternative treatments selected in Phase II for PCB-contaminated sediments.
In carrying out this phase, EPA will arrange to have PCB-contaminated sediments
treated in pilot-scale processing systems selected by EPA in Phase II. The
pilot tests will evaluate performance under field conditions, and will be
supported by laboratory tests.
There is substantial justification to proceed in the near future with the
test and evaluation of these processes. The developers of these processes
have the facilities required to begin the tests. Tests can proceed one at a
time if necessary, with separate funding for each. Allowing time for permits,
12
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set up, and check-out, the results of one or more tests could be available
for consideration by those at EPA who may be appropriating funds for the
Hudson River problem. Tests and evaluations could be conducted during the
summer and fall months, when the weather is much more favorable.
13
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SECTION 4
DISCUSSION OF EXTRACTION PROCESS
Selection of Equipment
The selection of suitable contacting equipment for a specific extraction
involves complex decisions particularly so in the absence of prior data with
the same system on either a pilot plant or industrial scale operation. A
study was therefore carried out to ascertain the types of pilot plant and
industrial scale extractors available and to evaluate their applicability for
the extraction of PCBs from sediments and soils. The results of this study
ares umma ri zed be!ow.
Survey of Industrial Extraction Equipment
Industrial solvent extraction contactors emphasize equipment with counter-
current flow operational capability. One convenient classification shown in
Table 1 is that of differential and stagewise contactors. The former provide
conditions for mass transfer throughout their length, aiming to produce optimum
concentration profiles. Stagewise contactors provide for a number of discrete
stages in which the two phases are brought to equilibrium, separated and passed
countercurrent to the adjoining stages. While such contactors avoid certain
problems such as the axial mixing found in some differential contactors, the
necessity of separating the phase between each stage can add substantially to
overall size and solvent inventory.
Another major division can be made according to whether the countercurrent
flow is produced by gravity action on the density differences between the phases
or by an applied force such as a centrifuge. A summary of features and fields
of industrially employed extraction equipment is shown in Table 2 and includes
most commercial contactors in use today.
TABLE 1: BASIC CLASSIFICATION OF INDUSTRIAL CONTACTORS
Forces Producing Phase
Interdispersion
Gravity only
Pulsation
Mechanical agitation
Centrifugal Force
Differential Contactors
Spray column
Packed column
Pulsed packed column
Pulsating plate column
Rotating disc contactor
Oldshire-Rushton column
Kuhni column*
Graesser contactor
Podbielniak
Quadronic
DeLaval
Stagewise Contactors
Perforated plate column
Pulsed sieve-plate
column*
Pulsed mixer-settler
Scheibel column
ARD extractor
Mixer-settlers
Westfalia
Robatel
*Could be considered intermediate between differential and stagewise.
14
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TABLE 2: SUMMARY OF FEATURES AND FIELDS OF APPLICATION
TYPES OF
EXTRACTOR
Unagitated columns
Mixer-settlers
Pulsed columns
Rotary-agitation
columns
Reciprocating-plate
columns
Centrifugal
extractors
GENERAL FEATURES
Low capital cost, low operating and
maintenance cost, simplicity in
construction, handles corrosive
material.
High stage efficiency, handles wide
solvent ratios, high capacity, good
flexibility, reliable scale-up, handles
liquids with high viscosity.
Low HETS, no internal moving parts, many
stages possible.
Reasonable capacity, reasonable HETS,
many stages possible, reasonable
construction cost, low operating and
maintenance cost.
High throughput, low HETS, great
versatility and flexibility, simplicity
in construction, handles liquids
containing suspended solids, handles
mixtures with emulsifying tendencies.
Short contacting time for unstable
material, limited space required,
handles easily emulsified material,
handles systems with little liquid
density difference.
FIELDS OF INDUSTRIA
APPLICATION
Petrochemical,
chemical
Petrochemical,
nuclear, fertiliz
metallurgical.
Nuclear,
petrochemical,
metallurgical.
Petrochemical,
metallurgical,
pharmaceutical,
Pharmaceutical,
petrochemical,
metallurgical,
chemical.
Pharmaceutical
nuclear,
petrochemical
HETS: Height equivalent to a theoretical stage.
15
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Settler Design
The processes that occur in a settler are quite complex, and interrelated.
•- They include the mechanisms 'of coalescence'and disengagement. Coalescence is-
retarded by an increase in the viscosity of the continuous phase. Increases
in temperature promote coalescence by lowering the viscosity. Decreases in
surface tension retard coalescence because they produce a greater area of the
continuous phase. Increases in density differences between the phases promote
coalescence by increasing the force acting to bring about drainage of the contin-
uous phase film. The formation of larger drops enhances coalescence, while
smaller drops retard it. Small droplets can give considerable difficulty in
practice as they can be easily entrained in product streams where they represent
both a loss and an impurity. Small drops introduced into the feed going to the
settler are particularly troublesome.
The basic requirements of efficient settler operation have been summarized
as follows: a) minimize turbulence in a settler as this will retard coalescence
by keeping small drops in suspension, b) minimize small drops in the original
dispersion, c) keep linear velocities along the settler at a low value, and d)
employ coalescence aids such as removable baskets of packings at the inlet point
provided that they do not result in too large pressure drops.
High throughput is a most important consideration of settler design. Exten-
sive experimentation has shown that there is a maximum safe throughput for a
specific extraction in a given mixer-settler, above which quite small changes can
result in flooding. Also the throughput unit volume of dispersion decreases as
the thickness of the dispersion band at the interface increases. One approach
to the problem of increasing the throughput of a settler of given dimensions is
to divide'the overall dispersion into a number of thinner bands. The Lurgi and
I.M.I, settler designs attempt to accomplish this by using a series of trays or
plates.
An alternative approach to increasing settler throughputs is to introduce
some packing into the settler which should be preferentially wet by the dispersed
phase. A woven-mesh packing incorporating materials that are both water and
organic wetted was developed some time ago and has given quite promising results
when tested in the Davy Powergas mixer-settler. The overall unit has been
claimed to operate more than an order of magnitude better than a simple mixer-
settler. Another approach to promote throughput, by the application of centri-
fugal contactors, has been well established for many years. They offer short
contact times and efficient phase separation and are especially desirable for
applications involving either chemically unstable or slow sett-Ving systems.
The Podbielniak, De Laval and Westfalia extractors have an excellent record
of performance for such problem liquid-liquid extractions. The Luweta equip-
ment is an adaption of the underdriven centrifugal cream separator with two
or more stages mounted vertically in a single assembly. Each stage comprises
a spray disk mixer and a centrifugal separator. The ports and channels for
transfer and conveyance are carried in a stationary central tube. The more
recently introduced Robatel contactor features very short residence times for
a novel multistage design.
16
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Contactor Selection
As noted above, contactor selection is a complex task as it involves both
technical and economic considerations applied to a specific system. As a
general guide a chemically unstable system or one with slow settling character-
istics will tend to favor centrifugal equipment. If however, a system is rather
inexpensive and only a few stages are required, simple gravity columns or mixer-
settlers should be considered. If a larger number of stages are required, a
mechanically agitated column becomes a candidate. Mixer-settlers are suitable
for most chemically stable systems, but require more groundspace than do columns.
Also the holdup in mixer-settlers is greater than in columns. On the other hand,
however, these are better in accepting flow changes from stage to stage due to
the transfer of material between the phases.
Specific technical criteria for selection of extraction equipment include the
following:
Total throughput -
Number of theoretical stages -
Physical properties of system -
Type of reaction -
for typical systems, a minimum total through-
put of 50 gallons/hour of feed plus extract
phase corresponds to a column of about 10 cm
in diameter; most industrial processes require
capacities of 500 to 50,000 gallons/hour and
more.
the height of most types of vertical contactors
tends to become excessive with more than,10-)5
stages. This limitation does not arise with
horizontal equipment especially mixer-settlers,
but floor space requirements become quite large.
contactor performance is affected by viscosities,
interfacial tensions, densities, boiling and
freezing points, temperature, f1ammabi1ity,
toxicity, etc.
the effect of slow heterogeneous reactions is
always to reduce the rate of mass transfer,
hence either increasing column height or reducing
stage efficiency; interfacial area should be
increased by upping rate of agitation; slow
homogeneous reactions are quite rare in liquid
extraction.
17
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Extreme phase ratios -
Short residence time -
Ability to handle solids -
Tendency to emulsify -
Limited space availability -
the effect of a low value is to reduce the
dispersed phase holdup and hence the inter-
facial area; a high value may cause large back-
mixing; in both cases, performance decreases;
the exceptions are mixer-settlers with provi-
sions for recirculation of the separated phases
back to the mixer.
this may be required with chemically unstable
products to minimize losses and leads to con-
sideration of centrifugal reactors.
some contactors are susceptable to blockage;
the only types which can accept significant
quantities of solids are the rotory and, to a
lesser extent, the raining bucket types (as
well as mixer-settlers).
nonmechanical contactors are generally preferred
to many widely agitated types, with the excep-
tion of the centrifuge units.
mixer-settlers and centrifuges should be con-
sidered.
Special material requirements - metals applicable to all contactors, non-metals
-•--- require-s-pecial study. - - -
Radioactivity or corrosion present - special studies of safety and material
properties needed.
Ease of cleaning -
Low maintenance -
depends on contactor design and construction
material.
mechanically and pulse agitated contactors
require more careful maintenance due to shaft
timing, seals, pulsing mechanisms, etc.
18
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Experimental Studies
During the first year of the. three year research .effort a significant
portion of the work was dedicated to the establishment of analytical procedures
for the determination of PCBs in sludges. These procedures were then employed
to analyze a set of PCB spiked water samples covering the concentration range
from 2ppm to 123ppm; details are given below. Furthermore, an environmental
sample, a sludge from Waukegan Harbor, Illinois, was analyzed. Apart from these
analytical studies seven different solvents and four additives were evaluated
for their potential use in the extraction process.
Extraction of PCBs from Spiked Water Samples
Various PCB spiked water samples were analyzed in order to determine
the amounts of the PCB contaminent that could be recovered by extraction
methods. EPA Method 608 was used for the analytical work. The PCB employed
was Aroclor 1232. The experimental study also provided information on the
higher and lower levels of extractability for known amounts of this particular
Aroclor.
The analytical data show total recoveries in the order of 90% for spiked
samples containing an initial Aroclor 1232 concentration of 123 micro grams/ml
(2 extractions). Recoveries from the samples spiked with 49.5 micro grams/ml
Aroclor 1232 were 88% and 90.4% respectively and about 100% for a 24.5 micro
grams/ml sample (2 extractions). For samples with 12.2 micro grams/ml initial
concentrations recoveries were 86.5% and 87.1% respectively. The data for the
two samples with the initial very low 2 micro grams/ml concentration lack
sufficient precision to warrant consideration.
Quantification of PCBs in Environmental Sample
After the analysis of PCB-spiked water samples had been sucessfully
completed the more difficult problem of analysis of PCB contaminated environmental
samples remained to be solved. A sludge sample from Waukegan Harbor with an
approximate PCB concentration of 5000 ppm was used. After an initial separation
of the sludge gave a liquid to solid ratio of about 3:2 it was decided to
analyze the liquid and the solid fraction of the sample by two different methods.
The liquid fraction was analyzed by the EPA-Method 608. The wet solids were
analyzed following a soxhlet extraction procedure, which had been used in an
EPA sponsored interlaboratory study. (Ann L. Alford-Stevens, et al., Anna!.
Chem. 1985, Vol. 57, 2452-2457).
The sample was centrifuged for one hour at 2500 rpm and then separated
into a liquid and a wet solid fraction. Two 20 gram aliquots of the wet solid
fraction were extracted by soxhlet.
The moisture content of the wet solid fraction was determined by air drying
the sample 4 days and then vacuum drying until constant weight was established.
PCB concentrations were calculated for the liquid fraction, the wet solid frac-
tion, the dry solid fraction and for the original environmental sample. The
results are given in Table 3.
19
-------
TABLE 3: PCB Concentration of Waukegan Harbor Sludge
Liquid Wet Solid Dry Solid Integral
Fraction Fraction Fraction Sample
Extracts
1ST 9.7 13950 32442 5818
2ND 8.1 14500 33721 6046
PCB Concentration is given in mg/kg (ppm).
Moisture content of wet solid fraction was: 57%.
The mass ratio of liquid fraction to wet solid fraction was: 1.4.
The mass ratio of liquid fraction to dry solid fraction was: 4.6.
Characterization of Solvents
A qualitative experimental study was carried out to characterize certain
pertinent properties of candidate solvents for PCB extractions from aqueous
solutions. Basic criteria for the selection of an extraction solvent have
been described previously. The objective of this study was to find the solvent
system which gives a clear phase separation in a very short settling time.
Seven hydrophobic solvents with high PCB solubility together with 4 hydro-
philic solvents as additives at three different solvent to water ratios (1:9,
1:1, 9:1) were investigated. Each solvent/water system was studied without
and with additives, whereby the ratio of hydrophobic solvent to additive was
kept at 4:1 for all cases.
The different solvent systems were subjected to the following experiment:
A total volume of 50 ml of solvent/water mixture was filled in a 65 ml screw
top sampling bottle and agitated for 2 min, 10 min and 30 min. respectively.
The agitation was performed with a Burrel-Wrist-Action-Shaker, which was
operated at a constant speed of one-semi-circular-motion per second. The sep-
aration following the agitation was observed qualitatively after two minutes
and 10 minutes of settling time. The quality of the separation was character-
ized using the following criteria.
a) Quality of phase boundary
b) Degree of murkiness in either phase
c) Amount of bubbles in either phase and/or at boundary
d) Severity of emulsion formed in either phase or at boundary
20
-------
The hydrophobia solvents and the additives (hydrophilic solvents)
investigated we're:
Hydrophobic Solvents Additives
Hexane Acetone
Kerosene Carbitol
Mineral Spirits Methanol
Petroleum Ether (PE) Methylene Chloride
Toluene
Turpentine
Xylene
Of the hydrophobia solvents only Hexane, Kerosene and Toluene were combined
with additives. A total of 288 observations were made.
New Process Development
The concept of using kerosene as an extraction solvent for removing PCBs
from sludges and sediments as originally proposed was based on two factors:
1) the low cost of kerosene and 2) some work underway on extraction of PCBs
from soils. While the cost factor is a driving force in any development, it
alone cannot overcome technical impracticalities. It became quite evident
early in the study that the presence of large quantities of water in the
contaminated samples was to present an insurmountable barrier to the use of
kerosene in this application. A bold new approach to this most difficult
problem was needed and is herein presented.
This new approach is based on some well known facts about the properties
of PCBs present in sludges and sediments, some common sense about the use of
particular hydrophyllic and hydrophobic solvents and application of a stripping
operation, an existing technology, as a final step for isolation and concentra-
tion of the contaminants.
The first step of the process takes advantage of the extremely low solu-
bility of PCBs in water. In a typical PCB contaminated sludge or sediment
composed primarily of water with, for example, 20% total solids, one could •
expect virtually all of the PCBs to be asociated with the sediment in a water
medium. Thus the first processing step is simply a physical separation of
water and solids. This can be accomplished with varying degrees of efficiency
using existing equipment. Practically, the solids fraction from this separation
will contain on the order of 50% water but will most likely contain 98%+ of the
PCB content. The solid fraction and the liquid fraction from step 1 require
further treatment, however, it was managed to isolate most of the PCBs and to
reduce the sample size by about 60%. The water fraction requires subsequent
treatment which will be addressed later.
21
-------
In the second step of the process, the PCB contaminated oil must be
dissociated from the inorganic substrate. To do this, a water miscible solvent
. (hydrophyllic), acetone, was added in quantities sufficient to break the bond
between the PCBs and the solid surface. This is followed by another liquid/solid
separation. This description is for one stage of the proposed second step of
the process. The amount of PCB transferred to the solvent/water mixture depends
on partitioning between the liquid and solid phases and thus we can define a
partition coefficient and ultimately a stage efficiency. One can then predict
the number of stages required to perform a particular level of separation given
the original contamination level and the allowable level in the solid effluent.
This second step is a multistage countercurrent leaching using a hydrophyllic
solvent.
The products from the second step are: 1) a hydrophyllic solvent/water
mixture containing nearly all of the PCB contamination which requires further
treatment and, 2) a PCB free soil/solvent mixture from which the solvent must
be recovered and returned to the process cycle with the soil now being decon-
taminated and ready to be returned to the environment. A small fraction of this
clean soil is utilized in an absorption column to extract the trace amounts of
PCBs from the water effluent of step 1.
The third step of the process is a stripping operation in which the PCB-
containing stream from above is contacted in, a liquid-liquid extractor with
a hydrophobic solvent and additional water. The additional water drives the
PCBs out of the solution and into the hydrophobic stripping solvent. This step
is required to separate the PCBs from the aqueous phase which is inconvenient
for the final destruction step and also, the PCB can be concentrated in this
step further reducing the volume of contaminated sample required for handling.
The two streams which leave this step are the PCB concentrated in stripping
solvent which proceeds to final destruction either by chemical means (KPEG
Reagent) or by other appropriate methods and the hydrophyllic solvent/water
mixture containing trace PCBs. The solvent/water mixture goes next to a
distillation column in which the solvent is released and returned to the leach-
ing process described in step 2. The water contaminated with trace amounts of
PCB is recycled to the front of the stripping process to close the cycle.
Proof of concept experiments have been conducted successfully and experi-
ments are now underway to determine process criteria to further advance this
concept. Particular attention has been paid to closing the various liquid and
solid stream cycles.
22
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SECTION 5
DISCUSSION OF ASSESSMENT STUDY
Screening of Processes
The processes were screened by examining each for any undesireable aspects.
Processes with such aspects were rejected from further assessment. For example,
lack of tolerance for water by a process is undesirable because of the extensive
sediment drying it necessitates. There is evidence in the collected data that
such drying generates fine particulates that must be removed from the exit gases
of the dryers. The recovered particulates must also be decontaminated. Processes
showing insufficient tolerance for water were therefore rejected from further
consideration as a primary treatment process in favor of more tolerant alter-
natives.
Table 4 lists the sixty four processes screened, identifies those selected
for further assessment, and gives the reasons for rejection of the rest. The
processes are arranged according to the generic types of technologies upon which
they are based. The use of generic technology types guided the survey and
assessment phases of this study by providing technologies from which treatment
processes could arise. Some of the technologies (e.g., nucleophilic substitu-
tion) have provided several processes. Some (e.g., enzymes) have not yet
provided any processes. These technologies are nevertheless discussed to
describe their status, with respect to PCB-contaminated sediment treatment, so
that their potential may be considered in research planning.
A process rated "1" in Table 4 for each technology has been selected for
further assessment. As noted, eleven processes obtained this rating. Higher
•rating numbers assigned the rest of the screened processes refer to footnotes
that identify the reason for rejection of"the process for further assessment.
23
-------
technology
References
Centofantl 1971; Chen 1982; Childs 198Tf
Craddock 1982; Edwards et al. 1982;
Environment Canada 1933; Hornlg 1984;
Massey and Walsh 1985; Rogers and Kornel
1985; Rogers 1983; Rogers 1985. '
Balllod et al. 1978; Miller and
Sev1enton1ewsk1 (n.d.); Miller and Fox
1982.
Process
Evaluation3
leinical
^-temperature oxidation
•t air oxidation
ipercrltlcal water oxidation Model 1 et al. 1982.
iem1cal oxldants
onation
orlne removal
'hydrochlorlnatlon
FMC Corporation (n.d.); March 1968.<
AHsman et al. 1981; Lacy and Rice
Deschlaeger 1976; Prengle and Mauk 1978.
U.S.P. 346. 636
Chu and Vick 1985; Laplere et al. 1977.
•dueing agents
Chu and Vick 1985; Sworzen and Ackerman
1982.
icleophillc substitution
1
t
Brown et al. 1985a; Brunelle and Single-
ton 1985; March 1968; New York University
1984; Ruzz et al. 1985; Smith and
Gurbacham 1981; Sunohlo (n.d.); Sweeney
and Fischer 1970; United States Patent
Office 1984b; Weitzman11984; Weltzman
1QR4- UpU7man 1QRS ' '
Uncatalyzed, general 2
Zlmpro Process, Santa Maria, 4,13
CA Waste Site
Catalyzed
Dow Chemical Co. Patent 3,984,311 2
IT Environmental Science 2
Modar 1
Potassium permanganate plus Chromic
Add and Nitric Add 6
Chlorolodides 4,7
Ruthenium tetroxide 3,4,8
GE UV/ozonation process 2
Molten aluminum/distillation 14
Catalytic: 2,3
Nickel on kleselguhr 2,3
Pd on charcoal 2,3
Lithium aluminum hydride 2,3
Butyl lithium 2,3
Raney Nickel 2,3
Sodium 1n liquid ammonia 7,9
Nickel-catalyzed zinc reduction 7,9
Hydrazine 7,9
UV light plus hydrogen 2
Mildly acidic zinc powder,
Sweeney and Fisher (1970) 2,14
Sodium-based processes:
Goodyear, sodium in naphthalene (1980) 10
Acurex, proprietary solvent
PCBX/Sun Ohio
PPM
Ontario Hydro Power
10
10
10
10
CM
-------
IADLC t
iuiii
Generic
technology
References
Process
Potassium poly (ethylene glycolate)
based:
KPEG Terraclean-Cl
GE KOH-PEG
New York University KPEG
Bailin and Hertzler 1977; Bailin and U/V photolysis
Hertzler 1978; Bailin et al. 1978; Syntex photolytic
Craft et al. 1975; Dev et al. 1985; Thermal corona glow
Kalmaz et al. 1981; Meuser and Weimer 1982;Microwave plasma
Plimmer 1978; Rogers and Kernel 1985; RF in situ heating
Rogers 1985; Trump et al. 1979: West et al.
1983. Gamma radiation (Craft et al. 1975)
LARC
Evaluation3
ucleophilic substitution
(continued)
adiant energy
lectromechanical reduction
lorinalysis
rolysis
YSICAL
noving and concentrating
?ated Air Stripping
fraction
Jsorption.
'trlfication
Massey and Walsh 1985.
Sworzen and Ackerman 1982.
Boyd 1985; New York State Department of
Environmental Conservation 1985a; New
York State Department of Environmental
Conservation 1985b.
Electromechanical research process
Hoechst process
Goodyear catalytic hydrogenalysis
Exhaustive chlorination
Advanced Electric Reactor
Wright-Malta alkaline catalyst fuel-gas
process
Angiola and Soden 1982; Caron 1985; Gilmer
and Freestone 1978; Githens 1984; Hancher
et al. 1984; Hawthorne 1982; Lee et al.
1979; Saunders 1985; Schwinn et al 1984;
Versar, Inc. 1984.
American Toxics Disposal, Inc.
Critical Fluid Systems, C02
Furfural
Acurex solvent wash
0. H. M. extraction
Soilex process
Carbon adsorption, general
Neoprene rubber adsorption
1
11
12
3
3,4
5
9,17
18
9
1
14
9
9
9 '
1
12
14
14
15
1
1
1
13
15
tn
csj
Timmerman 1985.
nrt nrnrocc
-------
Generic
technology
References
Ghasseml and Haro 1985; Law Engineering
Testing Company 1982; Stroud et al. 1978;
Subnamanlan and Mahal 1ngam 1977; TUtlebaum
et al. 1985.
Carlch and Tofflemlre 1983; Hand and Ford
1978; Murakami and Take1sh1 1978; U.S. Army
Corps of Engineers Water Resources Support
Center 1983; Zlmmle and Tofflemlre 1978.
Bedard et al. 1985; Bumpus et al. 1985;
Clark et al. 1979; Dawes and Sutherland
1976; Furakawa 1982; Isblster et al. 1984;
Kong and Sayler 1983; McConnlck 1985;
New York State Department of Environmental
Conservation 1985a; New York State Depart-
ment of Environmental Conservation 1985b;
Rhee et al. 1985b; Rhee et al. 1985;
Unterman et al. 1985.
Catelanl et al. 1971; Rochklnd et al'.
Unterman et al 1985.
Process
Asphalt with
11me pretreatment
Evaluation3
16"
15
16
13
13
.tabllizing
ottom recovery
BIOLOGICAL
Hcroorganisms
nzymes
Z-Impremix
Sulfur-asphalt blends (K-20)
Ground freezing
Dredging
Bio-Clean
Sybron B1-Chem 1006 PB
Composting
B1o-Surf
Ecolotrol, Inc.
Wormes Biochemical's Phenobac
Rhee anaerobic degradation
No processes found
1
1
1
4,13
4,13
1,13
14
Explanation of process rating:~
1. Identified emerging sediment treatment process.
2. Destruction efficiency appears to be too low to meet environmental goals.
3. Processing time apppears to be extremely long for practical timely cleanup.
i
4. Data available for dioxln, other chlorinated compounds, or other contaminants, but not PCBs.
5. Process has been shown to destroy PCBs in gas streams only. It may be feasible for sediments, but has not been shown
to be. .!'
to
CJ
-------
TABLE 4 (continued)
6. PCBs with 5-7 chlorine atoms per molecule are not destroyed.
7. Products of partial degradation may be toxic.
8. Reagent 1s very costly/toxic or both.
9. Process costs appear to be excessively high compared with other emerging treatment processes.
10. Water destroys the reagent or Interferes with its action, thus the process would require excessive drying of sediments
and, probably, extraction in pretreatments. The process would therefore have application only as a subordinate final
step to several extraction and concentration operations.
11. This particular process was not evaluated because data were not available for assessment.
12. This process 1s an alternative to another process using the same generic technology, but 1t 1s in very early stages of
development, and data were not available for assessment.
13. This technique 1s basically applicable to preliminary operations prior to treatment or to treatment of wastestreams
(e.g., wastewaters) from chemical or physical treatments. ,
14. This process is in the concept stage and data are Insufficient to assess It for PCB-contaminated sediments.
15. This process has been found to be ineffective.
16. This technology provides only for encapsulation of the PCB-contaminated sediments.
17. This process supports Incineration of PCBs.
(
18. The process does not appear to be feasible for submerged sediments.
-------
Development of Evaluation Criteria
Problem Definition
The PCB contamination problem in the Hudson River is representative of
the type of PCB destruction/detoxification problems focused on in this study.
The New York State Department of Environmental Conservation (DEC) recently
concluded a 2-year survey of 40 miles of the upper Hudson River (1976-1977).
The survey, conducted with consultant Malcolm Pirnie, Inc. (White Plains, New
York) identified 40 spots collectively containing more than an estimated
382,000 m3 (500,000 yd3) of sediment contaminated with PCBs at concentrations
greater than 50 ppm. The depth of contamination seems to be between 0.25 and
0.45 meters. A more recent survey (1984) was made of a 5-mile reach extending
downstream 5 miles from Ft. Edward, New York. Samples from the near-shore
area showed from 40 to 60 ppm PCBs.
A pilot dredging operation, performed with hydraulic dredges between 1978
and 1979, netted 152,900 m3 (200,000 yd3) of material with seemingly little
dispersion of the contaminant downstream. The contaminated areas are located
in shallow, slow-moving waters near the riverbanks. Although DEC is investigat-
ing other disposal methods, it is expected to dredge the contaminated sediments
and bury them because of the high costs of alternatives.
.The wetness of the sediments will preclude the use of many treatment proc-
esses designed to treat PCB-containing oils using reagents that would be destroyed
or made ineffective 'in the presence of water.
Regulatory, Factors
The goal for detoxification/destruction is to have no more than 1 to 5 ppm
PCBs in the treated sediment. At present, PCB disposal is regulated under TSCA
[40 CFR 761.60 a 5 (1-111)].
The criterion of 1 to 5 ppm for a promising alternative treatment should
result in a treated sediment that is disposable without restriction.
Technical Factors
Technical factors relate to a broad range of principles of operation of
diverse applied technologies. Factors have been chosen that can be used
effectively in comparing one treatment process with another. Additional
factors, specific to a technology, have been chosen to help portray the inher-
ent strengths and limitations of a process.
The goal set for process performance is to reduce the PCB concentration in
treated sediments to background levels of 1 to 5 ppm. Several of the processes
were found to meet this goal.
28
-------
Available capacity was found not to exist for.any of the processes. How-
ever, several were developed sufficiently to permit projections of the time
required to build a facility for application of the treatment.
Conditions/limitations that were considered included tolerance for water,
required processing time, and controllability of process conditions. Those
treatments that could tolerate water up to about 40 percent would not require
a drying step with its attendant fines control problems. Those requiring only
1 day for treatment could generally show a faster rate of cleanup than those
requiring 3 days. Some biological processes required more than 3 weeks. The
treatments generally provided control of the processing conditions; however, a
few (e.g., composting) would not necessarily do so.
Concentration range handled in data developed for the processes ranged
from unknown to 3,000 ppm. Some processes had limits inherent in the tech-
nology; others had no apparent limits.
Processes were found to range from concept stage to completed field tests.
Most were in the pilot stage.
Data needs varied with the status of the process. At worst, data were
available showing tests of the concept. At best, the process had been field
tested, and only permits and checkout were needed.
Unit operations employed in each process were identified. Collectively,
the processes use 18 different unit operations. The number of operations per
process varied from two to eight, depending upon the complexity of the tech-
nology. • "...
Cost Estimates
Costs of appplying an alternative technology are very difficult to predict
because of the uncertainties regarding the potentially available new treatment
processes. Estimates of the quantities of PCB-contaminated sediments are
under review and may change significantly as a result of the reviews. In most
cases, additional information is needed regarding the yet to be proven effec-
tiveness of emerging treatment processes before the costs of their application
can be assessed accurately. Therefore, the cost estimates presented here
should be viewed as preliminary with respect to the new treatment processes.
A range of costs is given for supporting operations (dredging and transporta-
tion) to reflect differences in different geographical areas of the country.
Because the regulations permit the use of incineration or chemical waste
landfill and the application costs of these two methods are available from
firms engaging in their practice, these costs were used as lower and upper
limits with which to compare the costs of applying new alternative technology.
29
-------
The application of any treatment process can involve the need for one or
more of the following unit operations: dredging, transport, storage, landfill
disposal, land treatment disposal,-Incineration,-and/or alternative treatment.-.
Estimates have been developed for all of these so that, in any given process-
ing evaluation, the proper elements could be added to obtain an estimate of
the cost of application. The estimates were made in terms of the cost per
cubic meter of sediment treated. The sediment was assumed to have a density
of 1.68 Mg/m3.
Table 5 shows the unit cost estimates used to develop cost ranges for the
emerging treatments.
TABLE 5: UNIT COST ESTIMATES
Operation Cost, $/m3
Dredging 20
Transport 13 to 126
Storage 10
Landfill disposal . 260 to 490
Land treatment 33 to 111
Incineration 1,680
Baseline costs are taken as the range of costs for sediment removal, trans-
port, and disposal in a chemical waste landfill. This range is calculated using
the unit costs from Table 5.
Baseline costs, $/m3 = dredging cost and transport cost + disposal cost
= $20 + $13 to $126 + $260 to $490
= $293 to $636.
Incineration costs include those for dredging, transport, and incineration.
The cost of residue disposal is included in the incineration cost:
Incineration cost, $/m3 = dredging cost + transport cost + incineration
cost
= $20 + $13 to $126 + $1,680
= $1,713 to $1,826.
The costs of alternative treatments are calculated in the same way, by
summing the costs for the separate operations involved.
30
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• . Initial Assessment of Processes
The processes assessed represent six different technologies; each of which
is briefly described prior to discussing the processes to which it applies.
For the processes themselves, the depth of the summaries varies because of the
varing extent of available,, information.^ .,_,,... ,...._,._ . _., ...... ••-_-.•_*._
Processes Based on Chemical Technologies
The MODAR supercritical water (SCW) oxidation process is a relatively low-
temperature oxidation process that utilizes temperatures and pressures of super-
critical water (above 374 °C and over 22.09 MPa) to break down hazardous organics
to carbon dioxide, water, and other simple, less harmful molecules. The treat-
ment is not selective but rather applicable to a broad range of compounds.
Normally water-insoluble organics become highly soluble in supercritical water.
The water also acts to reform complex organics, and heteroatoms, including
halogens, phosphorous, sulfur, and metals, are readily precipitated as salts
when present with appropriate counter-ions.
The MODAR process as applied to soil-slurry decontamination consists of
the following steps:
1. PCB-contaminated sediments are fed as a slurry with 20 to 40 percent
solids, as determined by some continuous flow bench-scale testing and
preliminary economic studies. The slurry is pressurized to super-
critical pressure then heated by heat exchange with oxidizer effluent
generated in a subsequent step.
2. At the oxidizer, pressurized oxygen, organic fuel, preheated slurry
and oxidizer recycle are broght together. Because the water is
supercritical, the oxidant is completely miscible with the solution ' -
(i.e., the mixture is a single, homogeneous phase). Organics are
oxidized in a controlled but rapid reaction. Because the oxidizer
operates adiabatically, the heat released by combustion of readily
oxidized components is sufficient to raise the fluid phase to tempera-
tures at which all organics are oxidized rapidly. For a feed of 5
percent organics by weight, the heat of combustion is sufficient to
raise the oxidizer effluent to at least 550 °C.
3. The effluent from the oxidizer is fed to a salt and sediment separa-
tor, where inorganics and sediments originally present in the feed are
removed as a solid slurry. At 500 °C and above, the solubility of
inorganics in SCW is extremely low.
-31-
-------
4. A portion of the superheated SCW is recycled to the SCW oxidizer by a
high temperature, high pressure pump. This operation provides for
sufficient heating of the feed to bring the oxidizer influent to
supercritical conditions.
5. The remainder of the superheated SCW (with some C02) is used to
preheat the incoming soil slurry.
As a waste destruction process, the Modar concept has several advantages.
The chemical reactions that occur are carried out in a closed system, making
it possible to maintain total physical control of waste materials from stor-
age, through the oxidation process, to the eventual discharge of the products
of combustion and any associated wastes.
The Modar System has been tested for soils, and major problems in handling
this type of process feed have been identified. The components would be con-
structed from corrosion-resistant, high-nickel alloys. Projected costs of
treatment alone are $184 to $554/m3 of PCB-contaminated sediment. Dredging
would be required, as well as transport for treatment and redeposition of
treated sediments. The overall cost estimate is thus:
Cost, $/m3 = ($20 dredging) + ($13 - $126 transportation)
+ ($184 - $554 treatment) + ($33 deposition)
= $250 - $733/m.3.
Nucleophilic (electron-donating) substitution removes chlorine from aro-
matic compounds by two mechanisms, the intermediate complex mechanism and the
benzyne mechanism.' The intermediate complex mechanism consists of thef follow-
ing two steps, with the first usually rate-determining:
Fast
32
-------
The resonance hybrid formed in the first reaction is represented by the
structures within the brackets. These are shown in an alternative representa-
tion for reaction 2. The overall reaction rate is increased by the presence
of activating groups (e.g., NO, N02) on the molecule.
The benzyne mechanisms occur on aryl halides such as PCBs, which require
stronger bases than normally used because they lack activity groups on the
molecule:
NH3 + cr
or
If the aryl halide contains two ortho substituents, this mechanism cannot
occur.
Nucleophilic substitution using alkali metal hydroxides in poly (ethylene
glycol) [PEG], or poly (ethylene glycol methyl ether) [PEGM] has been shown to
remove chlorine from PCBs. Chlorine removal probably involves alkoxide reac-
tion, as illustrated by"the following mechanism:
^ ArCln + ROK -> ArCln_i OR + KC1
Chlorinated
aromatic
Potassium
glycollate
-> PEG ether
The partially dechlorinated, water-soluble reaction product may continue to
undergo dechlorination, depending on the reaction conditions.
The KPEG treatment process is identified by Gal son Research Corporation as
Terraclean-Cl. Evaluation of this process is based upon data for the Terraclean-
Cl version.
The Terraclean-Cl process involves the chemical dehalogenation of PCBs
under mild conditions. This is achieved by mixing the soil with an equal
volume of hot (150 °C) reagent in a rotating mixer such as a converted cement
mixer. Water coming in with the soil is vollatilized and recovered for later
use in the process. The reagent consists of a mixture of polyglycols and
33
-------
capped polyglycols (PEG and PEGM), potassium hydroxide (KOH), and dimethyl
sulfoxide (DMSO). The exact formulation of the reagent is varied according
to the specific soil and contaminant combination. The DMSO does not take part
in the reaction but acts as a catalyst and phase transfer agent to extract the
PCBs from the sediments.
At the end of the reaction, usually 30 to 120 min, the bulk of the reagent
(>80 percent in field tests) is decanted from the soil. A small part of the
reagent remains on the soil, along with some of the dechlorinated reaction
products. The residual reagent and dechlorinated by-products are removed from
the soil by mixing the soil with an equal volume of water and decanting the
water. This washing is done two or three times and provides >99 percent over-
all recovery of reagent. The washwater from the last wash is passed through a
bed of activated carbon, which preferentially removes the dehalogenated prod-
ucts. The contaminated carbon is burned in a PCB incinerator. The partially
dechlorinated PCB continues to dechlorinate, with >98 percent of the chlorine
associated with the PCB being recovered as KC1 under some conditions; the OMSO
acts as a catalyst and phase transfer agent by increasing both the rate of
reaction and the rate of transport of PCB from the soil into the reagent.
The total cost of application of the treatment process is estimated as
fol1ows:
Cost item Cost, $/m3
4-h cycle 8-h cycle
Capital 12.56 25.11
Reagent 25.66 25.66
Energ^ 33.20 33.20
Maintenance 1.26 2.51
Labor 22.00 44.00
Water disposal 2.20 2.20
Subtotal 96.88 66.34
Profit/contingency (50 percent) 48.44 66.34
Total 145.32 199.02
These costs do not include dredging or permitting costs. With dredging
costs of $20/m3, transportation costs of $13 to $126/m3, and final placement
costs of $33/m3, total costs in the range of $211 to $378/m3 are anticipated.
Permitting costs are a separate item and would depend on the degree of cooper-
ation given by the various regulatory bodies involved. However, the total
costs are not highly sensitive to this item because permitting costs of
$2,000,000 would only add $5/m3 to the costs of processing.
34
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Ultraviolet (UV) radiation may drive chemical reactions in PCBs. The
structure of the products of UV radiation alone are not well defined. The
-primary reaction at wavelengths greater than 290 nm is stepwise dechlorina-
tion. Photolysis experiments in methanol at 298 to 313 K for 10 to 15 h
showed that HC1 was evolved. The products contained in the menthanol solution
consisted of dechlorinated PCB and certain methanol substitution products.
The amount of methoxylated products did not exceed 5 percent of the total
amount of products formed.
UV light energy, combined with a reducing environment, has been used to
dechlorinate PCBs essentially completely in 1.5 to 2 h. Because the photo-
chemical reaction is initiated by the absorption of light energy, the irradia-
tion wavelength must match the absorption band associated with the chemical
bond of interest in the molecule and the solvent must not absorb significantly
at the irradiation wavelength. For PCBs, low-pressure mercury lamps that emit
approximately 95 percent of their energy at 253.7 nm provide adequate irradia-
tion.
Suitable solvents include water, alcohols, and hydrocarbons. However,
these have very different effects on the process efficiency and mechanism. In
heavy hydrocarbons, the dominant PCB reaction is the polymerization of the
biphenyl radicals to yield polyphenylenes. In basic alcohol solutions, a
stepwise dechlorination of the molecule occurs. This reaction occurs via the
triplet state, and the reaction rate is dependent on the lifetime of that
state. The hydrogen for the hydrodehalogenation initially comes from the
solvent. In alcohol solutions, sparged hydrogen gas increases the reaction
rate by removing triplet quenchers from the solution by combination with the
sblvent from radicals formed. In-addition to "the hydrogen, small amounts of
sodium hydroxide are added to the alcoholic solution as a chlorine scavenger.
\
These photochemical reaction conditions lead to a rapid, highly control-
lable destruction of the PCBs, yielding only biphenyl and sodium chloride as
the final products. Oxygenated derivatives, chlorinated dibenzofurans, or
chlorinated dioxins have never been observed in the gas chromatographs or the
mass spectra of the intermediates or products in the LARC degradation of PCBs.
The LARC process (Light Activated Reduction of Chemicals) uses UV light
and an optimized reducing environment to dehalogenate various chlorinated
compounds extracted from soils.
Studies were performed to determine the extraction efficiency from soil of
Aroclor 1260 using isopropanol as the extraction solvent. Isopropanol was
chosen because it is a good LARC solvent, dissolves PCBs readily, and is
relatively inexpensive.
35
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The cost of treatment using this process has been estimated (1984)
using an average concentration in-the-soil of 1,500 ppm. -Cost items include r-;-
daily operation, labor, analytical, travel, per diem, and profit. These total
approximately $157/m3 of soil. Adding costs of dredging, transportation, and
placement gives a cost range of $223 to $336/m3.
Pyrolysis is a thermal rupture of the chemical bonds of a molecule that
destroys 1t without oxidation. The energy requirements vary with the material
being processed. The use of pyrolysis requires the adoption of process designs
that provide for transport of material that can melt, char, or become sticky
during passage through a reactor. The design must provide for efficient heat
transfer to the material so that it can be heated to 2,000 to 2,300 °C.
Pollution controls are required to remove particulates and toxic components
from exit gases. Feeds to pyrolysis units must usually be predried.
The advanced electric reactor (AER) is a thermal treatment process. Pre-
treatment of the feed material is required. It must be dried to a moisture
content of less than 3 percent and ground to 35 mesh particle size.
The treatment process is based on a high-temperature fluid-wall reactor.
The reactor heats organic compounds rapidly to temperatures in the range of
2,200 °C using intense thermal radiation in the near infrared. The reactants
(in this case, nonliquid PCBs) are isolated from the reactor core walls by a
gaseous blanket of nitrogen flowing radially Inward through the porous core
walls. Carbon electrodes are heated and, in turn, heat the reactor core to
incandescence so that heat transfer is accomplished by radiative coupling from
.the core to the feed materials. The only feed streams to the reactor are the -
solid waste containing PCBs and the blanket gas (nitrogen). PCBs are destroyed
by pyrolysxis rather than oxidation. Therefore, typical products produced by
incineration such as carbon monoxide, carbon dioxide, and oxides of nitrogen
are not formed in significant concentrations. The principal products of soil-
borne PCB destruction are H2, Cl2, HC1, elemental carbon, and a granular free-
flowing solid-derived waste.
The solid feed stream is introduced at the top of the reactor by a metered
screw feeder connecting the air-tight feed hopper to the reactor. Nitrogen is
introduced primarily at two points in the reactor annulus formed by the external •
containing vessel and the porous graphite core to create the fluid wall.
Small nitrogen streams are used to sweep sight glasses, prevent oxygen
intrusion at the electrode ports, and similar nonprocess uses. Nitrogen flow
is monitored by calibrated orifices in each feed line. The solid feed passes
through the reactor where pyrolysis occurs. After leaving the reactor, the
product gas and waste solids pass through two post-reactor treatment zones (PRTZ)
The first PRTZ is an insulated vessel that provides additional high-temperature
( 1,095 °C) residence time ( 5 s), and the second PRTZ is water-cooled. It
also provides additional residence time ( 10 s), but it primarily cools the
gas to less than 538 °C prior to downstream particulate cleanup.
36
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The product gas then enters a baghouse for fine particle removal followed
by an aqueous caustic scrubber for chlorine removal. Any residual organics
and chlorine are~removed by" passing 'the 'product gas through two banks" in*
series of five parallel activated carbon beds just upstream of the emissions
stack. The organic-, particulate-, and chlorine-free product gas, composed
almost entirely of nitrogen, is then emitted to the atmosphere through the
process stack.
Solids exiting the PRTZ are collected in a solids bin that is sealed to
the atomsphere. Additional solids in the product gas are removed by a cyclone
and routed back to the solids bin. The solids collected in the solids bin are
removed by plant personnel after each test or pair of tests.
For very large volume cleanups, a cost estimate is $412/ton ($763/m3)
strictly as a budgetary cost figure and not as an absolute cost or quotation.
This amount does not include the costs of dredging, transporting soil to the
AER site, or facilities for storage of dredged soil. It also does not provide
for cost of landfilling or other disposal of the treated sediment.
The capital cost for construction and initial testing of a single 25,000-
ton/year transportable AER is approximately $4 million, not including permits
and trial burns. With six units, it would require approximately 3.5 years to
treat 382,000 m3 of sediment.
Dredging would be required, also transport for treatment and redeposition
of treated sediments. The overall cost estimate is thus:
Cost, $/m3 = ($20 dredging) + ($13 - $126 transportation)
+ ($763 treatment) + ($33 deposition)
= $829 - $942/m3.
Thionation introduces sulfur into an organic molecule to displace chlo-
rine. The possible use of sulfur reactions to degrade pollutants has not been
systematically exploited. It has been reported that, at 150-170 °C, sulfur
and sodium carbonate react with p-dichlorobenzene, removing the chlorine to
form an insoluble polymer, sodium chloride, and carbon dioxide. Limited tests
were conducted in 1986 by W. C. Von Meyer (EPA Contract No. 68-02-3992, Task 53,
Project Officer John Glaser) on a mixture of dried loam soil sparged with
mixed dichlorobenzenes (DCBs), sodium carbonate, and sulfur. The dichloro-
benzenes were added as a €-.131 g/ml solution in acetone. Reaction was carried
out in a tilted 500-ml flask fitted with a condenser and sodium carbonate
trap. The trap was required to remove hydrogen sulfide gas evolved during the
reaction. The reactants were mixed periodically by rotating the flask a
quarter turn every two hours over the 9 hour reaction period. The temperature
reanged to 88 °C, and rose in the eighth hour to 260 °C when an exothermic
excursion followed evolution of volatiles formed from the sulfur. The re-
sults, based on analyses by thin layer chromatography and gas chromatography,
were as follows:
37
-------
1,2 dichlorobenzene: 8.4 percent dechlorinated
3.4 percent volatilized . ..-..-.
1,3 dichlorobenzene: 90.8 percent dechlorinated
3.4 percent volatilized
1,4 dichlorobenzene: 91 percent dechlorinated
1.4 percent volatilized.
This is the extent of Von Meyer's investigation of the application of
thionation to contaminated soils. As part of his study, DCB's and three chlo-
rinated pesticides (Dieldrin, Lindane, and Heptachlor) were treated directly
with two reagents; sodium polysulfide in an ethylene glycol-water media, and
sulfur in ethylene glycol. With water present, the organics were all con-
sistently volatilized at the 108-114 °C reaction temperature. The sulfur-
ethylene glycol reagent degraded Dieldrin 99 percent and Lindane 90 percent.
Heptachlor was not tested with this reagent.
Thionation is in the early stages of investigation, and a process for
treatment of PCBs has not been sufficiently identified to permit further
evaluation.
Processes Based on Physical Technologies
The term "extraction" is employed to cover not only liquid-liquid extrac-
tion but also leaching of solids with organic solvents. Extraction of PCBs
from a contaminated soil or sediment is emerging as a prerequisite for most
chemical processes. PCBs are first extracted using a suitable solvent, and
the obtained PCB solution is then subjected to one of the processes for
destruction of the PCBs. Proven solvents include kerosene, methanol, ethanol,
isopropanol, furfural, dimenthyl formamide (DMF), dimethyl sulfoxide, ethylene
diamine, and Freon mixtures. Supercritical fluids such as carbon dioxide have
also been considered. Destruction of the dissolved PCBs is accomplished by a
chemical reagent such as APE6 detoxification, or the PCBs are concentrated by
distillation or adsorption on carbon to give a RCRA waste that can be incin-
erated.
"Soilex" is a process developed at the Oak Ridge National Laboratory and
reported on in 1985. Kerosene and water were determined to be the solvent of
choice. Kerosene can be recovered for recycle by steam-stripping. Soil-to-
water ratios of 3 to 5 and soil-to-kerosene ratios of 3 to 5 were found to be
best. No difference in extraction performance could be determined between 15-
and 30-min mixing times. The kerosene retention in the soil was about 25 vol
percent. A three-stage batch pilot unit operating with a 6-to-l volume ratio
experienced soil feed PCB concentrations of 180 to 350 ppm and discharge soil
levels of 6 to 9 ppm. Lower soil values could be obtained using additional
stages. The process generates a RCRA waste (concentrated PCBs) requiring treat-
ment and disposal.
38
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The "Soilex" process reported pilot plant data showing an estimated 85
percent removal of PCBs from soils using a kerosene-water mixture. The kerosene
solubilized the PCBs and attendant other oils, and the water helped break up the
soil particles. The mixture ratio found to give the most complete extraction of
PCB was one part of soil to three parts of kerosene and three parts of water.
A rough cost estimate based on increasing the number of extraction stages
to achieve desired background levels of PCBs in the treated soil, is: $856 to
$913/m3. This includes dredging, transportation, treatment, and redeposition
of the treated sediments.
In 1985, The Galson Research Corporation showed that the rate of liquid-
liquid extraction of PCBs from oils solutions by APEG reagents could be substan-
tially increased by adding dimethyl sulfoxide (DMSO) or ethylene diamine to the
hydroxide/PEG phase. The reagent with DMSO reached <2 ppm PCB after 30 min
versus about 400 min for the reagent without DMSO. Details of the APEG process
have been described under Processes Based on Chemical Technologies.
The Acurex Corporation designed and built a solid/liquid extraction process
in late 1984. A proprietary solvent is used, having been selected by comparisons
of adsorption isotherms and PCB diffusion rates into several fluids: pure hexane,
pure FC-113 (1,1,2-trichlorotrifluoroethane), a proprietary solvent blend, and
an FC-113/hexane blend. With the pure Freon and topsoil, the equilibrium was
favorable; however, it took up to 18 h for the system to reach equilibrium.
Other solvents and solvent combinations were found that reduced the time to
reach equilibrium to 30 to 40 min, a practical value.
The Acurex Corporation reported that repeated washings of PCB-contaminated
soils with Freon-type solvents reduced the residual loading to <2 ppm. The soil
types tested were sand-clay mixtures and a dark loam. PCB loadings to 1,983 ppm
were leached in an agitated extractor. The pilot soil-washing system consists
of a soil contactor, dirty and clean solvent storage tanks, a solvent reclamation
system, steam generator, and ancillary piping equipment. It also includes vent
condensers and an activated carbon adsorption system for air pollution control.
Basic estimated costs for the treatment alone range from $130 to 390/m3.
Adding costs for dredging, transport, and placement of the treated sediments
gives a total cost estimate of $196 to $569/m3.
In 1985, 0. H. Materials Company used methanol to extract PCBs from pre-
dried contaminated soils in a Superfund cleanup project at Minden, West Virginia.
The soil was reduced to <25 ppm PCB and land-farmed. It is assumed that further
reduction in PCB concentration could be achieved using more stages of extrac-
tion. The process involves slurrying the ground and predried soil with methanol,
39
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separating and redrying the treated soil, and solvent cleanup for resale. The
cleanup employs activated carbon, which is subjected to incineration (other
-- treatments could-be used) as a RCRA wastes- -The-cleaned -soil is subjected"'to--:
light land farming for degradation of any residual methanol. Wastewaters are
treated in a holding pond.
Based on the conceptual process and the experience thus far, the process
is estimated to cost $400 to $514/m3, including dredging and transport costs.
In the field application (1985), methanol was purchased at $0.69/gal ($0.18/L)
and resold at $0.23/gal ($0.06/L).
Vitrification stabilizes radioactive-contaminated soils by melting.
Large-scale tests (1985) have demonstrated the vitrification of 300 Mg per
setting. At the high temperatures created (>1700 °C), the process pyrolyzes
organic materials. The products of pyrolysis diffuse to the surface and combust,
Any off-gases must be collected, monitored, and treated. Remaining ash, along
with other noncombustible materials, dissolves or becomes encapsulated in the
melt. Natural convective currents within the molten mass help distribute the
stabilized materials more uniformly. The molten soil or sediment is allowed to
cool to a durable glass and crystalline form.
In-situ vitrification (ISV) is a patented process developed at Battelle
Pacific Northwest Laboratory for the U.S. Department of Energy as an in-place
stabilization technique. Submerged sediments would be dredged before being
subjected to this treatment. In evaluation of its potential application to
soils contaminated with PCBs, an engineering-scale in-situ vitrification test
..,-fWJth PCB-contaminated soil has been performed for the Electric Power Research
Institute to determine the fate of PCBs and their byproducts when the process
is applied.
\
The cost of using the vitrification as a technique for in-situ treatment
has been estimated by the developers. The estimate includes expenses from
four categories: site preparation and closure activities, annual equipment
charges, operational costs, and consumable supplies including electrical power
and molybdenum electrodes. These costs are estimated to be between $150 and
$330/m3 depending on electrical power rates and soil moisture content. Soil
moisture content increases the cost by requiring more energy and time to
vitrify a given volume of contaminated soil because the water in the soil must
be evaporated. The total cost of using this approach requires, for submerged
sediments, the addition of dredging, transportation, and redeposition costs.
The solidified blocks of treated sediment could not be disposed of by land
treatment. If treated at a hazardous waste facility, they could be landfilled
there. The cost of such disposal would probably be the regular charge for
hazardous waste disposal, $260 - $490/m3. The treated material is estimated to
be eligible for delisting, however, and redeposition at a lower cost should be
possible. Given that the physical form of the treated sediments will limit
somewhat the available locations for its redeposition, a cost of $72/m3 has
• been estimated. This cost is less than that of controlled, managed land
40
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treatment ($111) since the material would require no control or management.
It is greater than the $33/m3 cost of short-term land treatment. The overall
cost estimate is thus: •-•••-••--: .-•-.- ------ = =--.— -=•-.•-. ;- ..-- ._ —
Cost, $/m3 = ($20 dredging) + ($13 - $126 transportation)
+ ($150 - $330 treatment) + ($72 redeposition)
= $255 to $548.
Processes Based on Biological Technologies
Biological technologies for PCB treatment include the use of free microbes
or their enzymes. The microbes may be bacteria or fungi and may act aerobically
(or anaerobically) or facultatively. They may be indigenous microorganisms,
conventional chemical mutants, or recombinant microorganisms. Their action may
result in partial or total degradation of the PCBs. Total degradation, termed
mineralization, occurs when the metabolic products are C02, H20, and HC1. Their
action may take place within the cell (bacteria) or external thereto (fungi).
Enzymes may be applied as free-flowing solutions or bonded to a solid
substrate. The use of enzymes alone has great conceptual potential but has
not progressed very far at this time.
Thirty-four bacterial strains and five fungal strains have been shown to
have varying degrees of competence in degrading PCBs. These microorganisms
metabolize PCBs using enzymes specific to the strain. Since most enzymes are
notably specific in .their actions,-:differ.ent,,enzymes .catalyzing the reaction-of-
different PCB isomers (termed cogeners in the biotechnology literature). In
some cases, the cogener may be metabolized only partially by a particular
species, ^and a product (e.g., a chlorobenzoate) may accumulate. In a parallel
situation, another species may be able to metabolize that product further,
although the second species may lack enzymes needed to metabolize the parent
PCB. By themselves, neither species could mineralize the cogener. However,
a mixed culture might act in concert mineralizing the product resulting from
metabolism of the substrate by the other species. A consortia of more than
two species may be required to mineralize a substrate and the effective species
may be bacteria, fungi, or a mixture of the two.
Some cells cometabolize PCBs; that is, they metabolize a PCB cogener while
obtaining their carbon and energy from other sources. Such metabolism may be
partial or complete and depends upon enzymes already active in the cell.
Biological technologies include a very broad spectrum of potential
capabilities, many aspects of which are being explored. True measures of their
ultimate capabilities for PCB-destruction cannot yet be made. Recent develop-
ments in mutant and enzyme technology are described, in the following nine
paragraphs.
41
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Indigenous and conventional chemically mutated microorganisms (those found
growing naturally in diverse PCB-containing soils and sediments) have been
isolated, identified, and tested for PCB-degradation capability using an assay
mixture containing five types of cogeners selected to provide different resist-
ance to enzyme attack.
The results obtained using 25 strains, including 15 isolates and 11 unidenti-
fied field isolates (e.g., H337 is an unidentified gram-negative organism isolated
from Hudson River sediments), identify Alcall genes eutrophus H850 and Pseudomonas
putida LB400 as the best microorganisms, both being able to degrade 13 test
cogeners 80 to 100 percent. Ten additional strains of bacteria were studied by
different investigations. Of these, the Arthrobacteria degraded the most PCB
cogeners.
The degradative pathways and cogener preferences differ among the micro-
organisms. Many bacteria oxidize PCBs via chlorobenzoic acid intermediates
and often accumulate the chlorobenzoate products. The major pathway proposed
for A. eutrophus H850 involves a dioxygenase that preferentially attacks at
carboH positions 3,4. In contrast, Corynebacterium sp MB! probably employs a
more common 2,3 dioxygenase mechanism.
Genetics studies of PCB-degrading bacteria have demonstrated that some of
the effective strains contain one or more plasmids. Plasmids are stable extra-
chromosomal circular double-stranded DNA replicons that are inheritable but are
also dispensable. Mutants of H850 that have lost their plasmid have also lost
the ability to metabolize PCBs. .__-._ ...-,^ . ...... ,.. . ..„_ . ^ _.
Mutations that living cells may undergo alter the genetic message. Some-
times the alterations in the'DNA code may lead to alteration of the cell's
metabolism. Some mutations allow the cell to survive in the presence of
potentially toxic compounds. In other cases, the cell acquires the ability to
use previously unsuitable substrates. Some agents, including UV light, some
kinds of radiation, and some chemical agents, cause increased mutagenesis.
These mutations are characterized by being randomly distributed across the
DNA. Mutations can be selected by applying selective pressures to a popula-
tion, creating an unfavorable environment in which only those cells that have
adaptation may take months before the altered population is large enough to be
observed.
Limited studies on the degradation of specific chlorinated biphenyl com-
pounds by pure strains of bacteria have established some general features of
PCB metabolism. A few strains have been shown to mineralize some chlorinated
biphenyls. In most cases, bacteria can degrade one ring of a chlorinated
biphenyl but are unable to degrade the resulting chlorinated benzoates. These
compounds accumulate in pure cultures. Other strains have been shown to be
capable of completely mineralizing chlorinated benzoates (e.g., the hybrid
strain of Pseudomonas sp B13 carrying the relatively nonspecific oxygenase of
P. putida mt-2 carried on the TOL plasmid). Mixed cultures of bacteria have
been shown to mineralize PCBs with four or fewer chlorines per molecule. More
heavily substituted PCBs appear to resist degradation to a greater extent.
42
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The mechanism of hydroxylation of PCBs by bacteria has not been eluci-
dated, nor have the enzymes mediating the steps in the proposed pathways been
isolated. Two pathways have been proposed. The first involves initial
hydroxylation in~the"2,3-pdsitibh of the less substituted"ring, followed by
meta cleavage and subsequent degradation of the aliphatic portion of the
molecule to form substituted benzoic acids. Chlorines on the aliphatic car-
bons are lost during this process.
However, this may not be the mechanism for degradation of PCBs substituted
in all the ortho positions. A second pathway, based on the action of a mono-
oxygenase in bacteria has been proposed after discovery of 4-hydroxy-4'-
chlorophenyl in extracts of bacteria cultures incubated with 4-chlorobiphenyl.
More evidence corroborating this mechanism is needed. It is proposed that the
major pathway of PCB metabolism in A. eutrophus H850 utilizes a dioxygenase
that preferentially attacks at carbon positions 3,4; while Corynebacterium sp.
MB1 probably employs a more common 2,3 dioxygenase. Limited evidence on
fungal metabolism of PCBs indicates activity of a monooxygenase.
Little has been done to prepare or work with enzymes alone, separated from
the organisms, despite the conceptual attractiveness of the approach. The
separation processes for PCB-degrading enzymes are yet to be developed. Some
enzymes may be cell wall bound, requiring special handling in their prepara-
tion. At present, little is known concerning the use of enzymes alone for PCB
decontamination of sediments.
The Bio-Clean process is a biological treatment process developed by
Bio-Clean, Inc., Bloomington, Minnesota. It has been well demonstrated for
PCPs. It requires further testing with, perhaps, the use of some additional
strains of microorganisms to bring it through the pilot stage for PCBs. It is
listed here as a representative bio-process that has potential application and
can be made available commercially. It does not require pretreatment to dewater
sediments, and it does not appear to generate any RCRA wastes or emissions.
The process involves two steps: (1) extraction, sterilization, and solubilizing
the contaminants using high pH and temperature, and (2) bacterial destruction
of the contaminant. These steps generally require 3 days. Standard digesters
that can handle 22 to 28 m3 of sediment (dry bases) are used in sets of three
to provide a daily capacity in multiples of 22 to 28 m3/day.
The processing cycle requires four steps:
1. Contaminated sediment is charged to the digester, in slurry form if
so received. The final digester charge will be approximately 2/3
water and 1/3 solids. The charge is made alkaline with sodium hydroxide
(or other alkaline hydroxide), then heated to approximately 82 °C, at
which temperature it is held for one hour. The mix is agitated to
promote solubilization of the PCBs.
43
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2. After the extraction, the slurry is cooled to 30 °C, neutralized and
inoculated with a selected microorganism(s) to initiate decontamina-
tion. The slurry is kept under these conditions for 48 to 72 h as
required, until the desired degradation has been attained. The exact
time requirements must be determined by tests for each particular
decent aminant. The degradation is an aerobic process and uses sterile
filtered air for oxygen.
3. A treated batch of sediment is discharged to a dewatering pit where
the sediment is separated for redeposition. The material is sampled
and tested to determine the concentration of residual PCB prior to its
relocation. The water is also analyzed for PCBs and thus disposed of
in a manner suitable for the particular site (e.g., through sanitary
sewer systems, storm sewer systems, or percolation into the ground or
recycle).
4. At the end of the decontamination period, the cycle begins again at 1.
The estimated cost of treatment using the Bio-Clean process on floating
barges is $191 to $370/m3. This includes dredging at $20/m3, and treatment
costs at $171 to $350/m3.
The Sybron process is a conceptual process still in the laboratory scale.
Information obtained from the company was very limited, and its evaluation is
correspondingly limited. The process may be able to operate under both aerobic
conditions or anaerobic -conditions with facultative aerobes and supplements of
nitrates. Further studies, to define an anaerobic process concept and principles
have been nroposed. This process has not been developed sufficiently to permit
a description in terms of unit operations. Information provided by Sybron
includes tests of their Bi-Chem 1006 PB for removal of PCBs from a municipal
sewage sludge. Cost estimates could not be made, due to the limited available
information.
Aerobic and anaerobic composting of PCB-contaminated soil has been studied
on a laboratory scale. Experiments were carried out with soil that was intention-
ally spiked with PCBs (Aroclor 1242). Aerobic composting resulted in the great-
est decrease in PCB concentration, with an average reduction of 62 percent in
four weeks. Residual concentrations ranged from 504 to 688 ppm. Anaerobic
composting resulted in 27 to 47 percent reduction in four weeks, with residual
concentrations ranging from 825 to 1,120 ppm.
Composting would appear to require considerable work-site space to handle
the sediment, with considerable monitoring to determine the progress of the
process. Lack of control of weather and other conditions would make the proc-
ess uncertain in terms of time and effort required.
44
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— : Data for composting are insufficient to" provide" a basis for cost estimates.
Considerable extrapolation of the performance data would be required to project
process conditions for desired residual PCB concentrations.
Initial Characterization and Ranking of Processes
This subsection provides two comparisons of the alternative treatment
processes previously discussed: characterization and ranking. The character-
ization provides for objective comparison of processes. The ranking provides
a subjective comparison of the processes based on the seven criteria previously
described.
Characterization
Table 6 summarizes five characteristics of the processes: unit operations,
available capacity, conditions/limitations, concentration handled, and any
generated RCRA wastes. The unit operations employed are given, and each is
identified by a number. Generally, a greater number of unit operations will
mean a greater effect on treatment costs. None of the processes has currently
available capacity approaching that required for major cleanups. Therefore,
the time required to build capacity is listed. Construction time ranges from
12 to 24 months. Certain conditions that typify the process or limit its
versatility are given in column 4 of Table 6.
The data from studies of the processes-'were-examined for ranges of'PCB
concentrations handled to date. .Generally, the values are not limitations on
the process, but only on the data acquired. The value <300 ppm for the
Bio-Clean process may, however, be a limitation requiring process adjustment
to control.
45
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lABLt b. IKEATMENT PROCESSES CHARACTERISTICS
;i
Process t
Chemical
Supercritical water oxidation
KPEG, Terraclean-Cl
KPEG, NYU
t
LARC I
•i
Advanced electric
reactor (J.M. Huber)
Physical
0. H. Materials
methanol extraction
"Sollex" kerosene/water
Acurex solvent wash
Vitrification
Available
capacity
Unit (or time
Operations to provide)
1.4,10
1,3,4,7 (24 mo)
1.2,3,4,5,
6,7,9
1,2,5,15 (24 mo)
7,8,12,13 (16 mo)
14
•
2, 7,8, ,14
15
1,2,5,15
2,4,5,6,
10,11
8,12,14
; Conditions
and limits
20-40% solids; 374 °C,
23.3 MPa organic
content >5% or supple-
mental fuel.
150 °C, 0.5-2 h
t
i
tolerates 25% water.
2204 °C, 2,400 kWh/m3
needs predryer
,
predry to <1% moisture
26% of kerosene sol-
vent retained in soil;
3 d per batch
t
3*-12 washes, tolerates
<40% water.
Electrical power usage
Concentration
handled
>3000 ppm
500 ppm or
greater
480 ppm
>3000 ppm
>400 ppm
to 350 ppm
tested
up to 1 ,983
ppm
500 ppm
RCRA
waste
generated
None
w.w.tr.
act.
carbon
None
None
tO
PCB-loaded
carbon from
solvent
cleanup
Concentrat-
ed PCB from
still to
Incinera-
tion
Concentrat-
ed PCB's to
KPEG
None
Increases with soil
moisture: submerged
sediments dredged
and treated
-------
TABLE 6 (continued)
1 ,
Process
ological
mposting
Unit
Operations
15,16
Available
capacity
(or time
to provide)
(16 mo)
\
Conditions
and limits
i
Seasonal effects,
reaction time must
>4 weeks
Concentration
handled
1590 ppm
be
RCRA
waste
generated
Treated
material
is still a
RCRA waste
o-Clean
bron Bi-Chem 1006
1,2,17
15,17
27 m3/d avail-
able, 12 mo for
full-size
Proved for PCP, labor- <300 ppm
atory confirmed for
PCB's
Unknown Unknown
None
Unknown
Dte-Unit operations key:
1. Liquid/solids separation
2. Extraction/solubilization (liquid-solids)
3. Liquid/liquid extraction
4. Chemical reactor
5. Stripping still
6. Solvent recovery still
7. Adsorption
8. Dryer (solids
9. Dryer (liquids)
10. Filtration
11. Steam cleaning
12. Thermal reactor
13. Grinding
14. Air pollution controls
15. Landfarm
16. Inoculation/digestion
17. UV light reactor
-------
Ranking
In contrast tT> process characterization, ranking is subjective. An
attempt was made to define and determine a single number that could represent
the overall position of each process relative to an arbitrarily defined per-
fect process. To do so, factors considered were given ratings as described
below.
The goal set for process performance is to reduce the PCS concentration in
treated sediments to background levels of 1 to 5 ppm. Several of the proc-
esses were found to meet this goal. Those that showed reduction to less than
2 ppm were assigned a rating of "6". Those that attained a level between 2
and 10 ppm were assigned a "4". Those with residual concentrations greater
than 10 ppm were rated "2".
Available capacity was found not to exist for any of the processes. How-
ever, several were developed sufficiently to permit projections of the time
required to build a facility for application of the treatment. Those for
which such projections could not be made were rated "2". Those requiring 24
or more months were rated "4". Those requiring 12 to 16 months were rated
"6".
Conditions/limitations that were rated were tolerance for water, required
processing time, and controllability of process conditions. Those treatments
that could tolerate water up to about 40 percent would not require a drying
step with its attendant fines control problems. Those requiring only 1 day
for treatment could generally show a faster rate of cleanup.than those requir-
ing 3 days. Some biological processes required more than 3 weeks. The treat-
ments generally provided control of the processing conditions; however, a few
(e.g., composting) would not necessarily do so. The three conditions/limita-
tions were ranked as follows:
Conditions/limitations Rank
Tolerates to 40 percent water and treats in 1 day 6
Sediment needs to be dried 5
Tolerates to 40 percent water and treats in 3 days 4
Tolerates water and treats in >3 weeks 3
Sediment needs to be dried, treats in >3 weeks 2
Processing conditions uncontrollable 1
Concentration range handled in data developed for the processes ranged
from unknown to 3,000 ppm. Ratings were assigned based on the upper limit of
feed concentration. The ratings were as follows:
48
-------
PCB concentration treated, ppm Rank
>3,000 6
2,000 to 3,000 5
1,500 to 2,000 4
500 3
250 to 350 2
Unknown 1
Status of development ratings were "1" for no data, "2" for laboratory-
scale tests completed, "3" for bench-scale tests completed, "4" for pilot-
scale tests completed, "5" for field tests completed; and "6" for commercial
system designed and ready for construction.
Test and evaluation data needs could be rated differently, depending upon
the purpose. For indicating the extent to which a treatment process is readied
for use, the more data that are available the better. For indicating the need
to support a very promising technology that lacks sufficient progress, the poten-
tial and the data needs should be rated in combination. The ratings used here
are for the former purpose and are as follows:
Test and evaluation data needs Rank
None except permits and checkout 6
Field tests 5
Pilot tests and costs _ .._ „ . - , . u - f .
Laboratory and bench tests* " ~ "'~' ~^~ 3
Conceptual treatment process design 2
O'.D.R data, residual PCB data, RCRA waste data 1
The estimated costs were rated by comparing the range of the cost estimates
obtained with the cost of placing them into a chemical waste landfill. Treatment
processes showing the lowest estimated cost range were rated "6"; those showing
a probable cost lower than landfill were rated "4"; those showing an estimated
cost equal to landfill were rated "2"; and those showing an estimated cost range
greater than landfill were rated "1".
Overall ranking was accomplished through the use of weighting factors
assigned to each rated factor. The weighted average rank was then obtained by
summing the products of the weighting factors and the ratings and dividing by
the sum of the weighting factors. The weighting factors were:
49
-------
Factor _. Weight
Residual PCB concentration 5
Capacity 2
Conditions/limitations 3
Concentration range handled 2
Status of development 2
Test and evaluation data needs 1
Estimated costs 4
Table 7 lists five additional characteristics of the processes and the
rating developed in the ranking process. The characteristics shown here
relate to the needs for further process development, listing, and evaluation.
The listing begins with an indication of the process status in terms of stages
of development completed. The processes range in stages completed from con-
cept to pilot plant.
Based on the weighted ratings, the eleven processes rank as follows from
highest to lowest: KPEG, LARC, Acurex, Bio-Clean, Modar-Supercritical Water,
Advanced Electric Reactor, Vitrification, OHM Extraction, Soilex, Composting,
and Sybron Bi-Chem 1006 PB/Hudson River Isolates.
50
-------
TABLE 7. TREATMENT PROCESSES RANKING
Process
Chemical /physical
Supercritical water
oxidation, Modar
KPEG Terraclean-Cl
LARC
Advanced electric
reactor
Physical
0. H. Materials,
Methanol extraction
Soilex
Acurex solvent wash
Status3
Field test with
PCB liquids
Pilot tests
Lab tests
Pilot tests
Field tests under
way
Pilot tests
Pilot-scale
Estimated
D/D/R
efflclency.% D
>99.9995
>98
>90
>99.9999
97
95
(3 stages)
e
Estimated
residual
PCB, ppm
<0.1 ppb
<1 ppm
38-50
<1 ppb
<25 ppm
6-9 ppm
<2 ppm
Test & evaluation
data needs
1,2,3,4,5,6,7,
1,6
2,3,4,5,6,7
Noned
2,3,6,7
5.6,7
Identity of
Estimated
costs, $/m3
250-733
208-375
223-336
830-943
401-514
856-913
196-569
Rating0
4.58
5.42
5.26
4.58
4.16
3.26
5.21 C
(field tests
planned)
In-s1tu vitrification Pilot test of soil
Battelle Pacific
NW for EPRI
mixed solvent,
6.7
99.9
None 1n vltrl- 6
field block. 0.7
ppm 1n adjacent
soil
255-548
4.53
See footnotes at end of table.
-------
i nuui- / . y mil L i nucu /
Process
Biological
Composting, aerobic
anaerobic
Bio-Clean, aerobic
Sybron Bl-Chem 1006
Status3
Lab-scale
Lab-scale
Bench-scale
Lab-scale and
Estimated
D/O/R
efficiency ,%b
62
18-47
99.99
concept 50
Estimated
residual
PCB, ppm
504-908
825-1268
25 ppb
Test & evaluation Estimated
data needs costs, $/m3
4,5,6
4,5,6
3,5,6,7 191-370
3,4,5.6.7
Rating0
1.79
1.79
4.84
1.47
NOTE-Data needs key:
1. D/O/R data
2. Residual PCB data
3. Unit operations data
4. Bench-scale data
5. Pilot-scale data
6. Field test data
7. Cost data
8. RCRA waste
aStatus Is defined 1n terms of the types of studies completed.
bD/D/R=destruct1on/detoxif1cat1on/removal.
cThe rating was obtained as shown by the example, under Characterization.
dAER 1s fully permitted under TSCA 1n EPA Region IV for destruction of PCB,
treatment is continued until a residual of <2 ppm PCB's is obtained.
C\J
ur>
-------
Final Assessment of Processes
This part of the^final assessment, building upon the initial phase, describes
the development of criteria for the final ranking of the processes, elaborates on
description of processes previously mentioned, and discusses each new process
being assessed.
Under the "Initial Assessment of Processes" we discussed the identification
of eleven candidate processes, out of sixty four evaluated, with potential for
decontamination of PCB-contaminated sediments. Listed in rank from highest to
lowest, the top eight processes were: KPEG, LARC, EPRI (Acurex), Bio-Clean,
Modar-Supercritical Water, Advanced Electric Reactor, Vitrification and OHM
Extraction. The three processes ranked but considered non-candidates were:
Soilex, Composting, and Sybron Bi-Chem 1006. At the start of the final assess-
ment, four developers indicated their processes should be eliminated from further
consideration. These four processes were: LARC, EPRI (Acurex), Advanced Electric
Reactor, and OHM Extraction. During the course of the final assessment, four
new technologies became available: The Basic Extraction Sludge Treatment
(B.E.S.T.) by Resources Conservation Co.; the UV/Ozone or Hydrogen-Ultrasonics
Technology by Ozonic Technologies, Inc.; the CFS Propane Extraction Process
by C. F. Systems Corp.; and the Low-Energy-Acetone-Kerosene Extraction Process
by Applied Science Dept. of New York University. The UV/Ozone or Hydrogen
Ultrasonics Technology provides continuity for the radient-energy approach
previously represented by the LARC process. The other three processes provide
improved approaches to extraction technology. These eight processes, four
initial and four new, were assessed as final candidates for thorough test and
evaluation.
Ranking Criteria
The .following criteria were used for the final selection of treatment
processes for test and evaluation (pilot-field tests):
0 The likelihood that the process will acceptably clean-up the PCB-
contaminated sediments;
0 The probable cost of the application;
0 The relative level of T and E effort;
0 The availability of a processing system; and
0 The likely future commercial availability of the process.
Acceptable clean-up requires a standard. The standard selected is a PCB
concentration in treated sediments of 2 ppm or less. The regulation require-
ments related to this standard were previously discussed under the initial
assessment.
53
-------
The probable cost of treatment 1s presented as the cost per cubic meter of
sediment treated, based on a system sufficiently large to process 380,000 m3
of Hudson River sediments in 2.5 years. By focusing on a specific site and
-stze of clean-up-task,-each process could be assessed using .available data from
sampling and analyses to characterize the feed materials to the processes, and
comparative cost estimates for a specific application could be obtained. The
sediments from the Hudson River also meet the requirement for use of a variety
of soil/sediment types in testing PCB-treatment processes.
The probable cost of treatment was obtained from the developers for those
processes sufficiently supported by commercial firms, or was estimated using
as major cost elements capital costs, and operation and maintenance costs.
Treatment process requirements determined capital, energy, and maintenance
costs. Labor rates, overhead, contingency, profit, and health and safety were
costed using standard unit values for all the processes.
Maintenance was estimated at 10 to 15 percent of the capital cost, depend-
ing on the number of unit operations involved and engineering practices for
the operation. The allowance for safety equipment was generally 0.30/m3 of
sediment treated ($114,000 for the clean-up of 380,000 m3 of sediment).
The treatment system cost estimate was capitalized (recovered) over the
2.5 years of operation taken as the base period. Some developers provided
treatment costs that were correspondingly lower for subsequent applications.
Engineering costs were not included in the estimates. An additional 7 to
15 percent of the subtotal cost (before profit and contingency) should be
included to provide for engineering in the design and construction stage of
the process application.
The test and evaluation effort required has been estimated based on a
comparison of available process data with the requirements for thorough test
and evaluation. A checklist of information requirements was developed to
identify the data categories to be supplied to qualify the processes for a
permit to test. The checklist identifies the following information as basic
to assessment of each process:
1. Waste characteristics;
2. Process engineering description;
3. Sampling and monitoring plan;
4. Accident and spill prevention and countermeasure; and
5. Demonstration test plan.
54
-------
'/' For these assessments, Hudson River sediments were selected as the char-
acterized wastes. Hudson River sediment material has been classified according
to its content of clay, silt, muck, muck and wood chips, sand, sand and wood
chips, coarse sand, and coarse sand and wood chips. Sediments have been shown
to range from clay to cobbles, with the largest mass fraction being in the sand
sizes. The coarse-fractien-^0-,42 mm) of the's'ediments typfdaily contained" -"
wood chips, sawdust, shale chips, cinders, and coal fragments. The fine size
fractions contained some fragments of the above, plus sand (containing quartz
and feldspar), silt, clay, and organic material. The highest PCS concentration
was the muck with wood chips class, which typically had over 30 percent silt and
clay, high volatile solids and some small but visible wood chips. The size low-
est in PCS was medium sized sand or gravel without wood chips.
For most of the processes assessed, test systems are available from the
developer. Most developers would need financial support of the testing time
and effort. A few of the processes (e.g., Low Energy Extraction) lack a suit-
able test system, but their estimated costs of application justify their
consideration herein. The availability of a suitable test system and any condi-
tions/restrictions on its use are discussed for each process.
The likely future commercial availability of the processes vary with the
strength and extent of their sponsorship. Some developers are commercial firms
in the waste treatment business with resources committed to further commercial-
ization of their process. Some developers have a need for financial support to
achieve commercialization. In all cases, the short-term (2.5 years) effort
projected in this evaluation, and the uncertainties of further markets make the
construction of a full-scale treatment system contingent upon completion of the
T and E (with attendant EPA approval of the process) followed by a contract for
the clean-up work itself. Under these necessary conditions, all the processes
assessed would be commercially available. The estimated time required to make
them available varies from process to process; however, this has been taken
into consideration in this evaluation.
•>
B.E.S.T.
The Basic Extraction Sludge Treatment (B.E.S.T.) process has been developed
by the Resources Conservation Co. (RCC), 3101 N.E. Northup Way, Belleview, WA
98004. The company was founded in 1968 and is a subsidiary of Reading and
Bates. The process uses a solvent having an inverse critica solution point in
water to remove water and oily material from solid matter. It has been applied
to clean-up PCB-contaminated oily sludges at a CERCLA site (General Refining
Site, Savannah, Georgia).
The company has bench units to perform glassware simulations of the process,
required to establish parameters for its application to a particular sediment.
The company also has a process components test unit sufficiently large to process
91 kg of sediment feed in seven days, and a large-scale skid mounted unit designed
to process 91 metric tons per day (24 hours) of feed.
55
-------
The process Is described generally as it is applied to PCB-contaminated
'sediment, sludge, or other feed material containing solid matter, oily con-
taminants, and bound and unbound water. The feed is first pretreated with an
alkaline composition, then admixed with triethylamine (TEA) while cooling
below the critical solution temperature (CST). A single liquid phase is formed
-from which the solid matter i-s separated. The liquid is then heated to a temp-
erature above the CST, to form an amine phase and a water phase, after which
the water phase is decanted from the amine phase. The amine phase contains
substantially all of the oily material including organic contaminants. It is
processed to recover the oil and contaminants, and the TEA is recycled for the
processing of additional feed material. The pretreatment of the feed with an
alkali reduces substantially the amount of residual amine carried over into the
solid and water products.
This process is essentially ready for T and E. The program should include
three "glassware" evaluations at a cost of $3,500 each. If the glassware test-
ing is successful, a pilot test at a cost of $50,000 would then be conducted.
Total cost: $50,500, with the equipment provided by RCC. EPA would supply
the sampling and analyses, and evaluation of the results as a separate program.
The estimated cost of T and E is $148,530 (analyses - $13,030; support including
permits, sampling/testing, and report - $75,000; test operation - $60,500).
Ultrasonics/Hydrogen - Ozone/UV Technology
The LARC process, discussed under initial assessment, is not now under
further consideration by the developers (George Anspach, Atlantic Research Corp.,
5390 Cherokee Ave., Alexandria, VA 22312). Another firm (Edward A. Pedzy,
Ozonic Technology Inc., 90 Herbert Ave., P. 0. Box 85, Closter, NO 07624) has
capabilities and interest in conducting tests of PCB-contaminated sediments.
Thus, their Ultrasonics/Hydrogen-Ozpne/UV Technology Became a replacement^in -
approach for the similar LARC-UV process. This Ozonic process has been shown
to be effective in cleaning PCBs from solid surfaces.
\
The process is based upon simultaneous extraction and treatment of a sedi-
ment slurry with ultrasound (above 20KHz) added to increase rates of dissolu-
tion of the PCB contaminants and reduce coalescence of bubbles of gas reactants.
The treatment is achieved by either ozone/ultraviolet irradiation or hydrogen/
ultraviolet irradiation. The sediments are fed as a slurry containing about
20 wt. percent solids into a mixing tank where predetermined amounts of detergent
and sodium hydroxide are added. The conditioned mix is pumped to the reactor
where the solids are maintained in suspension while the mixture is exposed to
ultraviolet irradiation and ozone (or hydrogen) is added. During this treatment,
microscopic turbulence is produced through ultrasonics. The treated slurry is
fed into a cyclone where the solids are removed, sampled, and tested to certify
them for discharge. The separated water is neutralized and also tested before
discharge.
The process needs to be tested using PCB-contaminated sediments to estab-
lish the process feasibility and to determine its potential performance. The
tests would involve assessing both UV/hydrogen/ultrasonics and UV/ozone/ultra-
sonics. The total estimated T and E cost is $151,000 (analyses - $21,000;
T and E support, permits, and report - $75,000; system operation - $55,000).
56
-------
'Bio-Clean Naturally-Adapted Microbial
The Bio-Clean Naturally-Adapted Microbial process has been developed by
Bio-Clean, Inc., 201 W. Burnsville Pkwy., 11306, Burnsville, MN 55337. A
-patent is pending-on ttie-process* Bio-Clean 1s-a-company-engaged in develop-------
1ng process systems to clean-up, remove or destroy hazardous chemicals 1n the
environment. The company has a suitable bench-system to support pilot and
field tests (32-45 metric tons/day capacity), and a laboratory test system
for conducting preliminary tests to establish specific conditions for a field
test. Support would be needed for the pilot and field work. The process, once
proven, would be available from the firm.
The process utilizes Arthrobacteria sp and/or other naturally-adapted
microbes to destroy PCBs (and related organics) under aerobic conditions.
Specifics of the process have been discussed under Initial Assessment of Proc-
esses-Processes Based on Biological Technologies. Preliminary tests would be
required to adapt the biological treatment to the specific waste. The total
estimated T and E cost is $163,600 (analyses - $33,600; T and E support, permits,
and report - $75,000; system operation - $55,000).
KPEG with DMSO
Nucleophilic substitution with the KPEG process and the Galson Research Corp,
version (Terraclean-Cl process) was previously discussed as a means of decon-
taming PCB-bearing sediments. Presented here is an elaboration of that discus-
sion pertaining to recent developments in the KPEG process. Although the
Corporation identified their version of the KPEG treatment process as the
"Terraclean-Cl" process, a more descriptive name is "KPEG with DMSO", since the
DMSO is the major ingrediant in their modification to the KPEG process.
The potassium polyethylene glycolate (KPEG) process has two potential '
applications in the treatment of PCB-contaminated sediments: The treatment of
the sediments themselves, or the treatment of concentrated PCBs resulting from
extraction processes. The former is assessed herein in terms of the Galson
Modified KPEG process, that is with dimethyl sulfoxide (DMSO). The latter
application would require treatment of a relatively concentrated solution of
PCBs in a non-aqueous solvent (triethylamine, kerosene, etc.).
The process developed by the Galson Research Corporation, 6601 Kirkville
Road, E. Syracuse, New York 13057, is scheduled to demonstrate treatment of
contaminated sandy soil on Guam, and is assessed here based on data from the
Phase 1 study and new data developed to qualify for this demonstration.
Gal sort has laboratory test facilities necessary to-set process parameters
for a demonstration, and a 150 L (40 gal) pilot system. For treatment of Guam
soils, a 1.5 m3(40 gal) system will soon be constructed and available for
various demonstrations. It is this potential system for Guam soils that was
considered in this assessment study.
57
-------
As previously discussed under initial assessment of processes, the Gal son
or "KPEG with DMSO processrdestroys "PCBs by'hucleVphillc'Vubstitution/ '"Potassium
hydroxide is reacted with polyethylene glycol (PEG) of about molecular weight
400 to form an alkoxide. The alkoxide reacts with one of the chlorine atoms on
a chlorinated molecule to produce an ether and potassium chloride. Addition of
an RO-group enhances the solubility of the molecule and makes 1t less toxic.
The reaction may continue until several chlorine atoms are removed from the PCB
molecule. The reagent consists of a mixture of PEG, potassium hydroxide, and
dimethyl sulfoxide (DMSO). The DMSO acts as a solvent or phase transfer agent
to extract the PCBs from the sediments.
Equipment to be used to implement the above chemical process consists of a
carbon steel reactor (1.5 m3 capacity), storage tanks for pre- and post-
treatment bulk storage, and a carbon adsorption unit for collection and control
of gaseous byproducts of the process.
Contaminated sediment is fed to the reactor from 55 gallon drums. An
equal volume of reagent is added to the soil in the reactor. The reagent is
blended with the soil using a carbon steel bladed mixer.
During operation of the system, reagent is mixed with make-up reagent
from the reagent storage tank and recirculated into the reaction vessel
containing contaminated soil. The reaction vessel is heated and the soil and
reagent are kept mixed until the reaction is complete. Volatilized material
from the bulk storage tank and the reaction vessel are vented through a char-
coal adsorption unit. Water vapor is condensed and used as wash water. At
the end of the reaction, the slurry is pumped into a similarly vented bulk •
storage tank". The reagent is decanted, weighed, and stored for reuse. The
soil is washed twice with water to remove excess reagent, and the wash water
is held for analysis and possible treatment with activated carbon.
For this assessment study, temperature in the reaction vessel is controlled
at 150 °C as measured on the system's temperature gauges. Mixing blade speeds
are controlled between 500 to 1,500 rpm. Energy to operate the blades and heat
the reaction vessel is supplied by a diesel generator.
The treated sediment is held for analysis. If PCB concentration is greater
than 2 ppm, the sediment is retreated. Byproducts 1n the sediment will be less
than 2 ppm KPEG with DMSO plus reaction products. All of which have been proven
to be non-toxic. The total T and E cost is estimated at $196,000 (analyses -
$21,000; T and E support, reports, and permits - $75,000; system operation -
$100,000).
58
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CFS Propane Extraction
The CFS Propane Extraction Process is a technology available from C. F.
Systems Corporation, 25 Acorn Park, Cambridge, Massachusetts 02140. The company
is a subsidiary of Arthur D. Little. As applied to PCB-contaminated sediments,
the process uses propane at ambient temperature and 1378 kPa (200 lb/in2) to
extract PCBs along with other oily organics from a water slurry of the sediment.
The treated slurry is discharged after separation from the liquid propane which
contains dissolved contaminant. The propane solution is fed to a separator
where the solvent is removed by vaporization and recycled. The contaminants
are drawn off as a concentrate for final treatment. The process has been tested
for PCB-containing refinery sludge. The PCB content of the solids component of
the sludge was reduced to 5 ppm.
The company has a small portable 1-liter test unit for preliminary evalu-
ations of the potential of the process using 0.56 kg of feed, and will have a
mobile propane pilot system soon. Preliminary tests of Hudson River sediments
using the portable test unit would be conducted by C. F. Systems at their
expense. Large-scale tests would require financial support.
The technology is available for preliminary testing to establish the proc-
essing parameters and system needs for PCB-contaminated sediments. A full-
scale system would be designed based upon the results of testing using the
bench-scale unit. C. F. Systems would not be able to conduct the tests at
Cambridge, but could make the unit available for testing elsewhere. The total
estimated cost for T and E is $122,660 (T and E including permits and report
$75,000; analyses - $17,660; system operation - $30,000).
Modar Supercritical Water - Oxidation
The foodar Supercritical Water - Oxidation process is another process that
has been previously discussed under the initial assessment of chemical tech-
nologies. The process is described here based upon discussions with the
developers and data supplied by them during the final assessment.
The process has been developed by MODAR, Inc., 3200 Wilcrest, Suite 220,
Houston, Texas 77042. The process utilizes water above critical conditions
(374 °C and 22.1 MPa) to increase the solubility of organic materials and
oxygen and effect a rapid oxidation, destroying organic contaminants. It has
been applied to destroy PCBs in oils, and to decontaminate dioxin tainted soil.
The company has a laboratory test unit and a skid-mounted pilot test unit having
a nominal organic material flow capacity of 190 Liters/day. This unit has been
operated at MODAR's research facility in Natick, Massachusetts and at the CECOS
International Niagara Falls site.
The following describes the preocess as it would be applied to sediments.
If not done as part of the dredging operation, the system would need to include
a screen to remove rocks and large pebbles. A feed pump would handle the range
of sediment particle sizes up to about 2 mm diameter, at 20-40 percent solids.
59
-------
Feed to the process is controlled to an upper limit of heating value of 4187
kj/kg (1800 Btu/lb). The Hudson River sediments lack sufficient heating
value, therefore-fuel addition "will be necessary. A combination of preheat
by exchange with process effluent and fuel addition is a more cost-effective
option. A portion of the supercritical process effluent will be recycled to
the reactor by a high-temperature, high-pressure pump to raise the combined
fluids to a high enough temperature to maintain rapid oxidation reactions in
the countinuously fed reactor. Oxygen, stored as a liquid, is pumped to
system pressure, preheated, and metered into the reaction vessel. Alterna-
tively, air can be compressed and used as the oxidant. It would be best to
demonstrate viability on their bench-scale unit. This would avoid the costs
of modification of the pilot system for slurry handling and onsite demonstra-
tion until the process has been proven. To accommodate the particle-size
restrictions, the sediments may need to be pulverized and hydrosieved to
provide a feed of size less than 38 urn. The total estimated cost of T and E
is $483,000 (analyses-$8,000; T and E support including sample preparation,
permits, and final report-$50,000; operating cost-$425,000). The support
cost is high because of the anticipated effort to be expended in resolving
design and safety considerations.
Low Energy Acetone-Kerosene Extraction
The Low Energy-Acetone-Kerosene Extraction Process is being developed by
the Applied Science Department of New York University, 26-36 Stuyvesant St.,
NY, NY 10003. The extracted contaminants are concentrated for subsequent
disposal. The basic principles of the process have been confirmed experimentally
using PCB-contaminated sediments from Waukegan Harbor, Illinois.
The process is based on an EPA-funded study to develop and evaluate a low-
energy technology for extraction of PCBs and other organic contaminants from
sediments and concentrating the extract in a manner suitable for the application
of a chemical destruction process. Details of the process and the study have
been previously discussed under Section 4 (Discussion on Extraction Process).
The development of this process through field test and evaluation is estimated
by New York University to require $827,000. This includes the construction and
operation of a field-scale unit. A possible commercial sponsorship is being
actively sought which, if confirmed, would reduce this cost to an estimated
$170,000.
In Situ vitrification
In Situ Vitrification was previously discussed as a process developed to
treat radionuclide-contaminated wastes, and subsequently tested for possible
adaptation to the treatment of PCB-contaminated soils. Submerged sediments
would be dredged before treatment. The process stabilizes contaminated soils
by melting into a durable glass and crystalline form. Four electrodes are
inserted into the sediments in a square array. A path for electric current is
made by placing a mixture of graphite and glass frit between the electrodes.
60
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Dissipation of power through the starter materials creates temperatures high
enough to melt a layer of sediment, which establishes a conductive path. The
molten zone grows downward through the contaminated soil. ~At the high tem-
peratures created (<1700 °C) organic materials pyrolyze, diffuse to the sur-
face, and combust. Off-gases are collected, monitored, and treated.
The process has been developed by Battelle Pacific Northwest Laboratories,
P. 0. Box 999, Richland, Washington. Battelle has indicated that they are
performing an Eastern soils demonstration in July, 1987 at the Oak Ridge
National Laboratory site in Tennessee, and have scheduled a pilot-scale PCB
test for September, 1987.
The estimated total T and E cost is $400,000 (Analyses, $14,200; T and E
support, $75,000; test system operation, $310,800). The test system includes
exit gas, capture canopies, and pollution controls.
The estimated treatment cost for this process is higher than that for
other processes evaluated, primarily due to the cost of consumable electrodes
and electric power.
61
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Selection of Three Processes
All the processes assessed have merit. In selecting among them, a ranking
system has been employed for comparative simultaneous evaluation of all five
criteria characteristics. For each process, the desirability of immediate
thorough test and evaluation was expressed by a desirability value, Dj:
Dj = (dd
•
!og Dj.modified s 1/n (*i log d^ + X2 log d2j + x3 log d3j + ... + xn log dnj
"x
0 < d < 1
The value found for each characteristic, y, was transformed to a value of
d according to the following judgements:
Value of d
1.0-0.99 Represents the ultimate level of the characteristic y.
Improvement beyond this point would have no appreciable
value.
0.99-0.80 Acceptable and excellent. Unusually good performance.
0.80-0.63 Acceptable and good.
0.63-0.40 Acceptable. Some improvement is desirable.
0.40-0.30 Borderline acceptability.
0.30-0.01 Unacceptable. This one characteristic could lead to
rejection of the process.
-------
The scale of d so developed is a dimensionless scale to which any charac-
teristic may be transformed so that it may be interpreted in terms of its
desirability for the intended application. In this evaluation, the most cost-
effective final process was sought that could be available in the shortest
reasonable time.
Where a characteristic was assessed on some scale of measurement scale,
mathematical transformation from the measurement scale of the characteristic
to the scale of "d" was accomplished by the basic equation:
d. ..-
In this equation: y, is a value of a treatment process characteristic i;
yih is the acceptable valuable of yi ; and
is the borderline value of y .
Table 8 shows the acceptable and borderline values of y^ for each
characteristic rated.
TABLE 8. ACCEPTABLE AND BORDERLINE VALUES FOR PROCESS
CHARACTERISTICS
Characteristic
Probability of cleaning to < 2 ppm
Probable cost of treatment, $/m3
T and E effort, $/1000
Test system availability, rating
Time to pxrovide commercial system, months
Acceptable
Value3
0.9
100
300
0.9
18
Borderline
Valueb
0.3
300
900
0.3
36
ad = 0.63 for these values.
bd = 0.37 for these values.
The probability of cleaning to £ 2 ppm was rated 0.9 if such performance
had been demonstrated with soils of any type, 0.8 if such performance was
projected from test data, and 0.3 if no data were available.
The probably cost of treatment was considered acceptable if $100/m^, and
borderline if $300/m3.
T and E effort was considered acceptable up to $300,000. Values above
$900,000 were considered borderline, but could be justified if the process had
potential for lowering the cost of treatment, or rated extremely well on other
desired characteristics.
63
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Test system availability was rated 0.9 for an available company-provided
system with experienced operating staff and resources to commercialize the
process; 0.7 for an available government-provided system; and 0.3 if a suit- "
able test system were not available.
Time to provide a commercial system sized to effect cleanup of 152,000 m3
of sediment per year was considered acceptable at 18 months, but borderline if
36 months were required.
Using the values of the characteristics shown in Table 8, Equation 4 was
applied to calculate the individual ratings shown for each process in Table
9. This table also shows the overall desirability rating of the process,
calculated using Equation 1.
All the processes showed acceptable "D" values. The B.E.S.T., UV/Ozone or
Hydrogen/Ultrasonics Technology, and Bio-Clean Naturally-Adapted Microbial processes
showed the highest values, and are recommended as the three processes for immediate
test and evaluation.
While this project was under way, an alternative process selection method-
ology became available at EPA's Hazardous Waste Engineering Research Laboratory.
The methodology is available as a computer program entitled "d-SSYS, A Computer
Model for the Evaluation of Competing Uncertainties," (Klee, 1987). This method
was applied by RTI in addition to the Desirability Function approach.
The D-SSYS calculates weights for each evaluation factor using values of
weight ratios assigned, by the user. Weight ratios were assigned to emphasi-ze
the importance of the range of treatment costs and test-and-evaluation costs.
The range of ratings for probability of cleaning to <2 ppm PCBs is only 0.1
(Table 2)> indicating that all the processes might reasonably be expected to
meet the requirement. The availability of a test system was not considered as
important as the total test and evaluation cost. The time required to make a
commercial process available showed a range of only six months, and was judged
of lesser importance than the two major costs assessed. All ratios among the
five factors that resulted from these assignments are shown below as a matrix.
For example, the ratio (test system availability)/(T and E cost) is shown as
the intersection of Row 4 and Column 3 as 0.2.
64
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TABLE 9. OVERALL DESIRABILITY OF IMMEDIATE T AND E OF THE EIGHT CANDIDATE PROCESSES
probability of clean-
ing to < 2 ppm <
\ rating
3robable cost of
treatment, $/m^
J rating
r and E effort '
$1000
i rating
\vailab1lity of a
•ystem for a test
future purchase by
govern, required
future purchase by
govern, not required
d rating ::
.ikely future avall-
ibility of the process
months ';
d rating j
't
)verall desirability, D
'
L
earliest future avail.
latest future avail.
average
KPEG,Galson
0.9
0.63
160-191
0.54a
216
0.66
0.9
0.63
19.5
0.62
0.615
0.615
0.615
Modar UV/Ozone-Hydrogen
Supercritical Ultrasonics CFS
Water Bio-Clean Technology Extraction
0.8
0.59
86-136
0.62
483
0.56
0.9
0.63
21.5
0.59
0.60
0.60
0.60
l,
r
0.9 0.8
0.63 0.59
156 - 90-120
0.57 0.63
-
166 '/ 151
0.68 ; 0.69
i
,.
t'
V
>'•
0.9 ?• 0.9
0.63 i 0.63
r
•'•
19 • 21-24
0.62 0.59-0.55
*
»•
-5
' <
0.617 0.625
0.617 0.616
0.617 : 0.621
S
0.8
0.59
153-264
0.50
123
0.69
0.9
0.63
25
0.54
0.59
0.59
0.59
Low-Energy In Situ
B.E.S.T. Extraction Vitrification
0.8
0.59
133
0.59
149
0.69
0.9
0.63
19
0.62
0.623
0.623
0.623
0.9
0.63
76-83
0.65
170-827b
0.67
0.8
0.59
25
0.54
0.614
0.614
0.614
0.9
0.63
293-332
.035
400
0.59
0.8
L
t.
0.59
19-24
0.62-0.55
0.54
0.52
0.53
'Average cost used for rating.
'Cost;^)f'$170,000 1f developed by sponsoring firm
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Clean to 2 ppm
Cost
T and E Cost
Test system availability
Early com. availability
Clean
to
2 ppm .,
1
5
5
1
1.25
.XostL
0.2
1
1
0.2
0.25
T & E
Cost
0.2
1
1
0.2
0.25
Test System
Availability
1
5
5
1
1.25
Early
Commercial
Availability
0.8
4
4
0.8
1
From these ratios and the following tabular algorithm, the factor weights
(W) were generated.
Factors
Clean to 2 ppm
T and E Cost
Future commercial proc.
Test system availability
Cost
Ratios
0.2000
W
4,
1
000
25
0.2000
5,000
0.20
1.00
0.25
0.20
1
Weights. W
0.0755
0.3774
0.0943
0.0755
0.3774
2.65
The procedure for weight generation is as follows:.
0 Construct an intermediate weighting scale (the w-column) by the
following procedure. Opposite that last factor enter a "1". The
remaining numbers in this column are formed by the product of its
predecessor and Ratio value opposite it in a sort of zigzag route up
the column. For example, the first w-value, 0.20 is the product of the
second w-value (1.00) and the first Ratio-value (0.2000).
0 Total the w-values. This total is 2.65. Construct a column of
standardized weights by dividing each element of the w-column by this
total to obtain the W-column. The elements in the W-column will,
perforce, total one.
The program then scales the factor scores to obtain a linear utility func-
tion:
y1 = bg + bi (factor score)
0 < y' _< 1.
In applying the scaling procedure to the two factors "Probability of
Cleaning to < 2 ppm" and "Availability of a Test System," it is noted that
(5)
66
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these are positive factors (the higher the factor score, the better the
process) and the 'y' values are obtained by:
.score-jj - minimum
...............................................
maximum score \j - minimum score^j (6)
The other three factors are noted to be negative (the higher the factor score,
the worse the process) and the y1 values are obtained by:
maximum score-jj -
— : ............... :•: ......... - ......
maximum score-jj - minimum score^ j (7)
The yij values for the five factors by which each of the eight processes
were assessed are given in Table 4.
TABLE 4. SCALED RATINGS OF EIGHT TREATMENT PROCESSES
Clean
to
2
KPEG (Gal son)
MODAR
Bio-Clean
UV/OZ or H2/Ultrasonics
CFS Propane Extraction
B.E.S.T. s
Low Energy Extraction
In Situ Vitrification
ppm
1
0
0
0
0
0
1
1
Probable
Tr. Cost
0.59
0.87
0.67
0.89
0.45
0.77
1
0
T * E Test System
Cost Availability
0.75
0.043
0.89
0.93
1
0.93
0
0.26
1
1
1
1
1
1
0
0
Early
Commercial
Availability
0.92
0.58
1
0.42
0
1
0
0.58
Depending on the users degree of risk that he is willing to accept, d-SSYS
fits a utility function to the y1 values via the following function:
utility = y'f . (8)
The exponent f is evaluated by presenting the user with a structured lottery.
d-SSYS requires s comparison between two simple lotteries for each factor
rated.
67
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Lottery 1 =
Lottery 2 =
50% chance of most undesirable rating,
50% chance of-most desirable rating.
X value of the rating for certain.
Using probable treatment cost as an example, RTI selected for Lottery 1
50% chance of a treatment cost of $313/m3
50% change of a treatment cost of $80/m3
and an X value equal to the mathematical expectation of Lottery 1 for
Lottery 2.
(0.5 x $313) + (0.5 x 80) = $196.50/m3.
The value of $196.50/m3 on the y' scale is
$313 - $196.5
$313 - $80
= 0.5
The utility of Lottery 2 is easily determined, since it is equal to the
utility of Lottery 1:
\
(0.5)(utility of $313/m3) + (0.5)(utility of $80/m3)=
(0.5 x 0.0) + (0.5 x 1) = 0.5.
From Equation 8:
f = (In utility)/ln y'
f = (In 0.5)/ln 0.5 =
(9)
Note that if Lottery 2 had been set at a lower cost for certain, f would
have been greater than 1 and function would have been a risk-taking one, in
that one would be willing to pay more for Lottery 1 in the hope of gaining a
treatment cost of $80/m3.
68
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.< ,A The remaining utilities for each factor are then calculated using Equa-
tion 8.
^
Using the scores scaled by Equation 8, the program computes an overall
deterministic score for each treatment process as the sum of the scaled factor
scores times the scaled factor weights. Using the factor scores of Table 4
(which equal the utility when f - 1) and the weights cited above, the follow-
ing deterministic scores were obtained for the treatment processes (Table 5).
TABLE 5. DETERMINISTIC SCORES FOR TREATMENT PROCESSES
Process Score
Basic Extraction Sludge Treatment 0.8127
UV/Ozone or Hydrogen/Ultrasonics 0.8010
Bio-Clean Naturally-Adapted Microbe 0.7583
Potassium Polyethylene Glycolate, Galson 0.7434
Critical Fluid Systems (CFS) Propane Extraction 0.6214
MODAR Supercritical Water Oxidation 0.4738
Low Energy Extraction, New York University 0.4529
In Situ Vitrification, Battelle 0.2299
The highest scores were attained by the Basic Extraction Sludge Treatment,
UV/Ozone or Hydrogen/Ultrasonics Technology, and Bio-Clean Naturally-Adapted
Microbe processes, the same processes that ranked highest using the Desir-
ability Function ranking methodology. These are recommended for immediate
test and evaluation.
In the application of this ranking, probable treatment cost and test and
evaluation cost were assigned weights 4 to 5 times those of the other three
factors. This increased emphasis on the costs involved did not change the top
three processes. With different weights assigned, it would be possible to
obtain a different ranking of the processes.
69
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SECTION 6
APPLICATION OF PROCESSES TO RCRA.WASTES .
The seven processes evaluated in the final assessment have potential applica-
tion to treatment of some RCRA listed hazardous wastes, as well as for removal of
PCBs from sediments.
The B.E.S.T. process applies generally to the separation of oils, solids,
and aqueous components of hazardous wastes.. It has been applied to the clean-up
of a CERCLA site at the General Refinery near Savannah, Georgia.
The Ultrasonics/Hydrogen-Ozone/UV Technology has been applied to the treat-
ment of waste slurries from the pulp and paper industry, and to the cleaning of
many types of materials. The UV energy must penetrate the treatment media
sufficiently to reach the molecules of the hazardous compound. Filtration or
cyclone-separation may be required following extraction in order to provide a
suitable medium for treatment.
The Bio-Clean Naturally-Adapted Microbial process can be applied to any
contaminant that is extractable and biodegradable. It has been applied to the
decontamination of pentachlorophenol-bearing soils. The process requires selec-
tion and adaptation of a suitable microorganism for the compounds being treated.
Complete mineralization of the compound may be achieved, or if this is not
possible, then non-hazardous residues may be produced. The process needs to be
evaluated, using bench-scale tests, for the different hazardous materials to be
treated. -- - —.«.„.-_-•' -....--•
The Galson KPEG with DMSO process, based on nucleophilic substitution, has
been applied to "dioxins". It has potential application to a number of listed
halogenated organic hazardous wastes from both non-specific and specific sources,
for example waste numbers F020, F021, F024, F027, and K042. The treatment leaves
dehalogenated compounds as a residue, which may or may not be toxic. Further
study is required to determine the performance of the process for these additional
applications.
The CFS Propane Extraction Process has been applied to the removal and concen-
tration of oily contaminants. Hazardous solvents and oxygenated compounds are
extracted using pressurized carbon dioxide.
Ttre Modar Supercritical Water-Oxidation process can apply generally to any
organic waste that can be oxidized at supercritical conditions. It has been
applied to decontaminate dioxin tainted soil. A test unit was operated at the
CECOS International Niagara Falls site.
The Low Energy Acetone-Kerosene Extraction process is applicable to any
organic waste that can be dissolved into a hydrophilic solvent. It produces a
concentrated solution suitable for incineration or other treatment.
70
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