NCD980602163_19830418_Warren County PCB Landfill_SERB C_Letter to Susan L. Peele re PCB treatment information-OCR

Ronald H. Levine, M.D., M.P.H.
DIVISION OF HEALTH SERVICES
P.O . Box 2091
Raleigh, N.C. 27602-2091
Susan L. Peele
422 Cobb UNC-CH
Chapel Hill, N. C. 27514
Dear Ms. Peele:
April 18, 1983
STATE HEALTH DI RECTOR
As requested in your letter of April 6, 1983, the questions
have been answered on the enclosed sheet. For more detailed
information I would recommend that you sec ure from the Department
of Crime Control & Public Safety a copy of the Environmental Impact
Statemen½which answers your questions in much more detail.
Pl ease let us know i f we can provide additional information.
RHL/OWS:sms
Enclosure
Sinceu ely, .
Rona~~~. M.P.H.
State Health Director
Division of Health Services
Jomes B Hunt, Jr/ Soroh T Morrow, MD , MPH ST A TE OF NORTH CAROLINA DEPARTMENT OF HUMAN RESOURCES GOVERNOR SECRET ARY
Developments and the Potential for Biological Treatment
of Hazardous Wastes
Gary S. Sayler, Ph.D.
Associate Professor
Department of Microbiology and
The Graduate Program in Ecology
The University of Tennessee
Knoxville, TN 37996
Report To:
The Committee of Science and Technology
Subcommittee on Investigations and Oversight
United States House of Representatives
May, 4, 1983
Environmental pollutants, potentially hazardous to human health and ecosystem
function, are frequently classified as "Xenobiotic" chemicals. Xenobiotics in this context
generally are defined as man made (anthropogenic) materials derived from chemical
synthesis or natural chemicals released as products or by products from industrial
sources in concentrations significantly higher than those produced from natural sources.
The general chemical structure and physical properties of xenobiotics of anthropogenic
origin makes them "foreign" as compared to natural chemicals in the environment and
accounts for their sometimes toxic properties and persistence in the environment. This
persistence is a result of chemical stability and their foreign nature which makes them
unrecognizable as chemical substances to be broken down (or decomposed) by the activity
of microorganisms. The purpose of this report is to describe current research at the
University of Tennessee, Knoxville dealing with the microbiological decomposition
(biodegradation) of xenobiotics and to discuss the convergence of knowledge on
biodegradation with emerging genetic technologies that may enhance the biological
destruction of hazardous environmental contaminants.
Research in the Department of Microbiology and the Graduate Program in Ecology
,
2
at the University of Tennessee, has focused on the biodegradation of xenobiotics
designated as priority pollutants with particular emphasis on polychlorinated biphenyls
(PCBs). PCBs are recognized as hazardous environmental pollutants of global distribution
and concern. These chlorinated organic molecules were marketed as complex mixtures
with wide ranging industrial applications and commercial use. Over their 50 year
production and use in the United States approximately five pounds of this material was
produced for every man, women and child. While it has been estimated that one-half
of the total PCB produced (opp. 1.4 billion pounds) is still in service, nearly 500 million
pounds have entered the environment and, of that, 300 million pounds is presently in
land fills.
PCB are true xenobiotic pollutants with no known counterparts produced in nature.
This foreign nature and extreme renvironmental chemical stability has led to their
resistance to biodegradation (biological recalcitrance) and resulting accumulation in the
environment. Previous studies on the microbial biodegradation (primarily bacterial)
have indicated that highly chlorinated PCBs are impervious to biological attack and
that even low chlorinated PCBs are only subject to incomplete biodegradation under
laboratory conditions. Our recent research has demonstrated that natural bacteria in
uncontaminated reservoir environments are also capable of incomplete biodegradation
of the lesser chlorinated PCBs. However, our more recent research has demonstrated
that, in PCB contaminated reservoir sediments, bacterial populations exist that carry
out the complete biodegradation of the lowe r chlorinated PCB residues as well as some
polybrominated biphenyls (PBB). The results of this study indicate that environmental
contamination may exert a selective effect for the development of novel biodegradative
capabilities among bacteria exposed to prolonged PCB contamination in natural
environments. Essentially, we may be able to view the process of evol ution of
biodegradative capacities,
I •.
,
3
Recently, another investigator at the University of Illinois has demonstrated that genetic
selection for new degradative capabilities can be produced in laboratory cultures exposed
to high levels of PCB stress. This selection termed "molecular breeding" also resulted
in bacterial strains capable of biodegradation of the lesser chlorinated PCB. Both our
research and that mentioned above indicate that the genetic determinant of these new
biodegradative capabilities is found on "plasmid" DNA within the bacterial cell.
Plasmids are pieces of DNA separate from the chromosome of the bacterial cell
and are not required by the cell to support life sustaining processes. Since their
relatively recent discovery, it has been shown that many exotic functions performed
by bacteria are determined by the existence of Plasmid DNA. In addition, plasmids
represent a mechanism of genetic exchange between bacterial cells, which are normally
asexual, and using recombinant DNA technologies have also been employed to genetically
f
manipulate or modify living cells. Consequently, plasmids involved in the biodegradation
of PCB and other environmental contaminants are ideal candidates for enhancing
biodegradative abilities among bacteria.
In addition to our isolation of bacteria capable of degrading the lesser chlorinated
PCB, we have also demonstrated that sunlight can sensitize PCB molecules with a
resultant five fold net increase in that rate at which they are biodegraded. Furthermore,
these same bacteria also demonstrate a profound ability to accumulate PCB residue
which may be precedent to biodegradation and potentially useful in localizing or
concentrating PCB in waste streams or contaminated environments.
In conjunction with EPA and NIH sponsored research on the biodegradative fate
of PCB in the environment, cooperative research is being conducted with an industrial
primary EPA contractor on a project to predict the fate of priority pollutants in
industrial waste treatment processes. In this integrated project, university -industry
scientists and engineers are studying the parameters that determine the rates of specific
4
pollutant removal in activated sludge waste treatment. Industry investigators are
determining rates and factors effecting the physical absorption and volatilization
(stripping) of pollutants, while we ore describing the biological factors determining the
rate and extent of bio-degradation of the pollutants. This EPA project has a significant
role in developing predictive methods to determine the fate of pollutants in conventional
waste treatment. Equally important is the role this project plays in determing the
ability of waste treatment engineering designs to efficiently capitalize on the potential
development of microorganisms designed for specific applications in biological waste
treatment. Specific factors being examined in this study include: determining the
selectivity and specificity of biodegradative processes in complex matrices of industrial
waste, the concentration of pollutant to which microorganisms are actually exposed
when competitive factors such as volatilization effect a waste system, the time required
(
to adapt a biological population to a specific waste and stability of that population
over time. Factors such as these are of fundamental importance in determining the
potential for biological degradation of pollutants in the environment or waste treatment
facilities.
Advances in the biological treatment of hazardous pollutants are expected to
develop from two frontiers that are being brought together by efforts of the EPA and
other federal agencies, industry, and the academic community. These frontiers are the
accurate description of the factors effecting biological degradation of pollutants and
determination of the biochemical and genetic mechanisms responsible for the
microbiological degradation of xenobiotics.
Potential advances in the area of biological treatment of hazardous pollutants
are expected to develop from a more comprehensive understanding of the biochemistry
and genetics of biodegradative mechanisms, and environmental factors effecting
biodP-gradation. Application of this knowledge to biological waste treatment systems
. ,
5
for hazardous pollutants will require a greater understanding of the strengths and
weaknesses of conventional and novel engineering designs. In this regard a greater
level of integration between basic science of biodegradation and engineering systems
is required in order to fully develop efficient biological treatment technologies. Recent
EPA efforts in this area promises to draw upon university and industry strengths in
order to unravel these complex interactions.
During the past decade considerable research evidence has been developed by
academic scientists that numerous environmentally persistant pollutants can be partially
or completely degraded by microorganisms under defined laboratory conditions. The
challenge has been to determine what factors limit biodegradation in the environment
which result in the observed persistence of the pollutant. Many physical-chemical
factors, such as binding to soil particles or lack of available oxygen, as well as biological
(
factors, like biochemical repression on inhibition by other organic molecules and
competition among microorganisms for available nutrients, have been identified as
factors limiting biodegradation. With the more recent discovery that genetically distinct
determinants (plasmids) may respond to and mediate the biodegradation of xenobiotic
contaminants, such as PCB and 2-4 D (2-4 dichlorophenoxy acetic acid, herbicide), it
is possible to suggest that the reported partial metabolism of the parent dioxin molecule
may evolve through plasmid mediated mechanisms or that this basic metabolism can
be subjected to genetic manipulation.
A greater emphasis is needed on basic research into the occurrence of novel
biodegradative microorganisms, their biochemistry and genetics. Relatively few
microorganisms have been studied in sufficient detail to fully exploit their utility in
biological waste treatment. No one or two bacterial species can be developed to
degrade all classes of xenobiotics. In addition relatively few xenobiotics have been
comprehensively examined to determine if possible biodegradative strategies exist, or
.. .
6
can be developed or enhanced. This emphasis should include both focusing ideas and
resources on conventional and novel biodegradative processes and integration into an
efficient waste treatment design.
In summary, persistent xenobiotic molecules may be biologically degraded under,
select or defined, laboratory or environmental conditions. For some xenobiotic, such
as PCB, this biodegradative capability may have recently arisen as an evolutionary
response to prolonged bacterial exposure to the xenobiotic. For a few well defined
(biochemically and genetically) microorganisms it is possible to alter or enhance
biodegradative capabilities. Rapid advances in biodegradation research can be attained
with new genetic information providing insights into the biochemical and environmental
aspects of biodegradation. To fully exploit these advances a continued effort must be
sustained to integrate scientific qnd engineering knowledge in developing biological
I
waste treatment technologies.