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Scientific Foundations of Bioremediation Current Status and Future Needs

This report is based on an American Academy of Microbiology colloquium held April 10-12, 1992 in Iowa City, Iowa. The colloquium was supported by the Department of Energy, the Environmental Protection Agency, and General Electric Corporation.
Washington (DC): American Society for Microbiology; .

The proceedings of the colloquium on the “Scientific Foundations of Bioremediation: Current Status and Future Needs” represents a continuation of a newly-initiated program of the American Academy of Microbiology to provide summary statements on timely and important scientific issues for scientists, specifically those issues with broad implications for society at large. The colloquium represents a convergence of recognition of a need for an evaluation of the scientific underpinning of bioremediation, a subject of intense public interest, and a need for bioremediation to be applied to problems of pollution such as that arising from the recent oil spill in Alaska. A request from the Public and Scientific Affairs Board of the American Society for Microbiology for a document addressing the scientific foundations of bioremediation served as the galvanizing force for initiating the colloquium.

The colloquium undertook as its charge to gather together a group of internationally recognized experts in the multidisciplinary fields which have an impact on bioremediation. The group of experts which was brought together evaluated the current state and future needs of the science underlying the technology of bioremediation. An excellent consensus was derived as to the currently available information and that which should be gathered to ensure progress in bioremediation as a scientifically based alternative for dealing with the problems of environmental pollution. The findings of this colloquium will be of great value to governmental agencies and certainly will serve scientists in the field of environmental biotechnology well as a seminal document for the rapidly developing field.

The American Academy of Microbiology wishes to thank David Gibson and Gary Sayler for organizing and conducting an outstanding meeting. In addition, Carol Colgan and Peggy McNult, Academy Staff, worked many long hours to ensure the success of the meeting. Most importantly, the Academy owes a debt of gratitude to all those colloquium participants who gave so graciously of their time and expertise to bring this project to a successful conclusion. This document represents their ideas, advice and recommendations, an effort of which they can be proud.

Rita R. Colwell

Chair, Board of Governors

American Academy of Microbiology

Front Matter

Colloquium Steering Committee

David T. Gibson (Co-Chair), University of Iowa

Gary S. Sayler (Co-Chair). University of Tennessee, Knoxville

Ronald M. Atlas, University of Louisville

David Pramer, Rutgers University

Board of Governors American Academy of Microbiology

Rita R. Colwell (Chair), Maryland Biotechnology Institute, University of Maryland

Albert Balows, Alpharetta, Georgia

Alice S. Huang, New York University

Edwin D. Kilbourne, Mount Sinai School of Medicine

Randall K. Holmes, Uniformed Services School of Medicine

Julius Schachter, University of California, San Francisco

Richard A. Finkelstein, University of Missouri

Colloquium Participants

Ronald Atlas, University of Louisville, Louisville, Kentucky

Michael Bagdasarian, Michigan State University, East Lansing. Michigan

Tom Baugh, Environmental Protection Agency, Washington, D.C.

Ananda M. Chakrabarty, University of Illinois, College of Medicine, Chicago. Illinois

Rita R. Colwell, University of Maryland, College Park, Maryland

James G. Ferry, Virginia Institute of Technology, Blacksburg, Virginia

Madilyn Fletcher, Department of Energy, Washington. D.C.

David T. Gibson, University of Iowa, Iowa City, Iowa

Robert A. Goldstein, Electric Power Research Institute. Palo Alto. California

Leslie Grady, Jr., Clemson University, Clemson, South Carolina

Michael Griffiths, Laboratory of the Government Chemist, Middlesex, England

Geoffrey Hamer, Institute of Aquatic Sciences and Water Pollution Control. Zurich. Switzerland

Frederick L. Hedberg, U.S. Air Force, Boiling Air Force Base. Washington. D.C.

George D. Hegeman. Indiana University, Bloomington. Indiana

Gary M. Klecka, Dow Chemical Company, Midland. Michigan

Hans-Joach Knackmuss, Institute Fur Mikrobiologia Der Universitat Stuttgart, Stuttgart, Germany

Mary E. Lidstrom, California Institute of Technology, Pasadena, California

William R. Mahaffey, Ecova Corporation. Redmond, Washington

Kevin C. Marshall, University of New South Wales, Kensington. Australia

Perry L. McCarty, Stanford University, Stanford, California

Frank Mondello, General Electric Corporation, Schenectady, New York

Ronald H. Olsen, University of Michigan Medical School, Ann Arbor, Michigan

Gene Parkin, University of Iowa, Iowa City, Iowa

David Pramer, Rutgers University, Piscataway, New Jersey

Suresh C. Rao, University of Florida, Gainesville. Forida

Gary S. Sayler, University of Tennessee. Knoxville, Tennessee

Jerald Schnoor, University of Iowa. Iowa City, Iowa

Jim C. Spain. U.S. Air Force, Tyndall Air Force Base. Florida

Joseph M. Suflita, University of Oklahoma, Norman, Oklahoma

Anne O. Summers, University of Georgia, Athens, Georgia

Kenneth N. Timmis, National Research Center for Biotechnology, Braunschweig, Germany

Ronald Unterman, Princeton Research Center. Lawrenceville, New Jersey

Robert J. Watkinson. Shell Biosciences Laboratory, Sittingbourne, Kent, England

Peter A. Williams, University of Wales. Bangor, Gwynedd, Wales

Ralph S. Wolfe, University of Illinois, Urbana, Illinois

Lily Y. Young, New York University Medical Center, New York, New York


The proceedings of the colloquium on the “Scientific Foundations of Bioremediation: Current Status and Future Needs” represents a continuation of a newly-initiated program of the American Academy of Microbiology to provide summary statements on timely and important scientific issues for scientists, specifically those issues with broad implications for society at large. The colloquium represents a convergence of recognition of a need for an evaluation of the scientific underpinning of bioremediation, a subject of intense public interest, and a need for bioremediation to be applied to problems of pollution such as that arising from the recent oil spill in Alaska. A request from the Public and Scientific Affairs Board of the American Society for Microbiology for a document addressing the scientific foundations of bioremediation served as the galvanizing force for initiating the colloquium.

The colloquium undertook as its charge to gather together a group of internationally recognized experts in the multidisciplinary fields which have an impact on bioremediation. The group of experts which was brought together evaluated the current state and future needs of the science underlying the technology of bioremediation. An excellent consensus was derived as to the currently available information and that which should be gathered to ensure progress in bioremediation as a scientifically based alternative for dealing with the problems of environmental pollution. The findings of this colloquium will be of great value to governmental agencies and certainly will serve scientists in the field of environmental biotechnology well as a seminal document for the rapidly developing field.

The American Academy of Microbiology wishes to thank David Gibson and Gary Sayler for organizing and conducting an outstanding meeting. In addition, Carol Colgan and Peggy McNult, Academy Staff, worked many long hours to ensure the success of the meeting. Most importantly, the Academy owes a debt of gratitude to all those colloquium participants who gave so graciously of their time and expertise to bring this project to a successful conclusion. This document represents their ideas, advice and recommendations, an effort of which they can be proud.

Rita R. Colwell

Chair, Board of Governors

American Academy of Microbiology

1. Introduction

Bioremediation can be defined as a process that uses living organisms or their catalysis to enhance the rate or extent of pollutant destruction. In this context, bioremediation can be considered as a viable component of hazardous waste management technology. The major goal of waste management is to reduce the exposure of organisms or receiving environments to the effects of environmental contaminants. As bioremediation is currently practiced, the predominant organisms in use are microorganisms (bacteria and fungi), but potential developments of the technology also include the use of algae, plankton, protozoa, plants, and controlled or assembled ecosystems.

1.1. Scope of the Hazardous Waste Problem

In the United States over the next 30 years, it is estimated that hazardous waste remediation and site restoration costs may approach $1.7 Trillion1. This upper estimate is based on the number of existing sites (currently in excess of 50.000 sites identified and several hundred thousand leaking underground storage tanks, 2,3), new site discovery, stringency of target cleanup levels and endpoints, and utilization of effective but expensive technology, such as incineration. These estimates do not include numerous non-point sources of environmental contamination derived from industry, agriculture, and municipalities that are not classified as hazardous wastes. Even more problems and costs are associated with the former Soviet Bloc and other industrialized and lesser developed countries.

Lost estimates suggest a viable market for waste treatment technology, but also raise serious concerns with ability-to-pay” and economic pressure requiring re-evaluation of clean up goals. Yet, in the U.S., where 40,000,000 citizens live within four miles of a superfund site4, there is likely to remain strong, if not increasing, support for site clean-up and restoration.

1.2. Selecting the Bioremediation Option

There are several different technologies available for the treatment of contaminated sites and groundwaters. For example, incineration, air-stripping, pump and treat systems, and bioremediation. In many cases, these different techniques can be integrated to achieve ultimate destruction of site-specific contaminants. Bioremediation is expected to play a major role in integrated waste management technology. However, to date, the selection of bioremediation as a treatment option has been limited in frequency and scope.

As for any waste treatment technology, bioremediation must be able to compete with or complement other treatment alternatives. Selection of treatment alternatives is most often based on criteria of effectiveness, implementability, and cost of the process. Innovative technologies are often rejected in favor of more mature or proven technologies. This is due partly to insufficient knowledge of one or more of the above criteria. Unfortunately, for many applications bioremediation is considered innovative even though effectiveness may have been demonstrated at the laboratory scale or in related waste treatment applications. In many cases there is enormous pressure for immediate site or spill clean-up mandated by public concern, toxic hazard, or regulatory or litigatory pressure. However, these influences do not permit the site investigation or bioprocess optimization that is necessary for selection of a competitive technology. If process and/or site-specific research, development, and demonstration have not been accomplished in advance, it is unlikely that bioremediation will be selected as a treatment-of-choice

1.3. Site and Contaminant Complexity

In practice, the implementation of treatment options is limited by the nature and complexity of the site in need of remediation. As a consequence, no single treatment technology is universally applicable to all cases. This is true for physical-chemical as well as biological remediation approaches. In addition, most technologies suffer similar physical-chemical environmental limitations of pollutant partitioning, sorption, mass transfer, and delivery and mixing of remains and catalysts. The implementation of bioremediation introduces another level of complexity especially under in situ conditions, that involves ecological interactions with oilier organisms either contributing to or interfering with the bioremediation process.

The complexity of hazardous and contaminated sites is often compounded by the presence of many different contaminating chemicals. Contaminated environmental matrices can include surface soil air, subsurface vadose and saturated soils, surface and ground water, bricks and mortar, structural steel, rubble, conveyor belts, synthetic and cellulosic polymers, tires, drums, plant debris, etc. Variability of chemical contaminants both within and among sites can also be extreme, ranging from crude petroleum, refined fuels, and nearly pure solvents to complex mixtures of organic compounds, metals, acids, bases, brines, and radionuclides Movement, partitioning, and compartmentalization of such materials is differentially controlled by the physical properties of the chemicals, soil chemistry, hydrogeology, vegetation, temperature, tide, wind, and human and animal disturbance.

Often, specific contaminants must be recompartmentalized from water to activated carbon or from soil to a desorbant solvent or gas phase to achieve remediation. Such requirements may be more or less difficult to implement for specific pollutants and may be inefficient as a long-term remediation solution. A classic example is pump and treat technology for contaminated ground water which, for practical purposes, can become an “infinite” pump and treat technology in general, the ultimale objective is the complete destruction of the offending contaminants or their conversion to innocuous products. This usually leads to the selection of an incineration process in some final stage of treatment together with a major increase in treatment cost. While an above ground biological treatment could be a cost effective alternative to incineration, it would not solve the solubility/mass transfer problems limiting the technology. However, as a destructive technology the potential exists to use in situ bioremediation to attack the source problem in the groundwater compartment.

Given the magnitude of global hazardous waste and environmental contamination problems and the existence of several treatment processes, there is a compelling need to evaluate the role of bioremediation in contributing to the reduction of both the extent and cost of these problems. To accomplish this, it is necessary to examine the fundamental scientific knowledge base of the technology, current use and limitations of the technology, and the near and future prospects for development, improvement, and implementation.

2. Fundamental Scientific Knowledge Base

2.1. Historical Perspective

One of the most attractive technical features of bioremediation is the broad and flexible capability of microorganisms to destroy or detoxify chemicals in a variety of environmental matrices. This is accomplished by taking advantage of the natural roles microorganisms play in ecosystems where they are responsible for the decomposition of organic matter and biogeochemical nutrient cycling. For example, much of the natural “bioremediation” that occurs on earth proceeds rapidly, completely, and without human intervention. Microorganisms return to the mineral state about 90% of the organic matter in the biosphere. They constitute the bulk of the biomass on the earth's surface and are probably the best studied of organisms that function in the mineralization process. In the case of agricultural wastes, municipal sewage, and industrial wastewater biotreatment, human intervention to hasten mineralization and detoxification has occurred for many years. Most major population centers in Europe and North America have a wastewater and a waste sewage sludge treatment facility of some kind that employs microbial communities under controlled conditions, both aerobic and anaerobic, to cleanse the water of organic materials and remove inorganic materials by technologically speeded-up action in a reasonably well-understood engineered process.

As the chemical industry developed in the late 19th and 20th centuries, increasing amounts of synthetic chemicals have teen added to the stream of human wastes. The ingenuity of the chemists has been such that some of these compounds (e.g., preservatives, biocides, etc.) are dissimilar to those produced by living organisms, and many were deliberately “designed” to be resistant to biological attack and mineralization. This has resulted in a significant problem in the cycling of waste materials and the novel occurrence and accumulation of significant levels of toxic and difficult-to-mineralize forms of waste in waste streams and the environment.

It has been axiomatic in microbial ecology that any chemical can be degraded by some microbial population from the great metabolic diversity within microbial communities in nature. This principle of “microbial infallibility” is constantly being challenged by man's inventiveness to produce novel chemical structures that have no close analogues in biochemical history and thus can result in their persistence in the environment.

2.2. Biochemical, Molecular, and Ecological Foundations of Bioremediation

Since the late 19th century, a large body of knowledge has accumulated about the fate of organic and inorganic matter in the biosphere and the role of microbes in mineralization. During the early 20th century, the detailed biochemical mechanisms functional in the microbial geochemical cycles were studied and clarified. During the 1930s. ’40s and ’50s, many details of pathways involved in mineralizing complex and slowly degraded materials were studied, and the importance of biochemical pathway regulation in this process was first appreciated.

Much of this earlier effort required simplification using the pure culture strategy and recovery of microbial species from individual sole carbon source enrichment cultures. The results from major research in this area have provided fundamental knowledge that forms much of the basis for bioremediation. For example:

  • The fundamental insight into the diversity of degradative populations in the environment.
  • The knowledge that xenobiotic mineralization has largely evolved from biochemical pathways associated with catabolism of naturally occurring compounds.
  • The existence of central intermediatory metabolites in biodegradative pathways.
  • The biochemical transformation of pollutants that do not serve as growth substrates (co-metabolism), such as trichloroethylene (TCE) degradation by methane-producing and methane,-, phenol-, toluene- and ammonia-utilizing bacteria, and degradation of chloroethenes by bacteria grown with methylalkenes.
  • The role of oxygenases in the degradation of a wide range of biosynthetic and xenobiotic compounds.
  • The mechanisms of uptake and detoxification of metals and inorganics.
  • The knowledge of regulation and induction of specific biodegradative pathways.
  • The existence of specific catabolic plasmids in environmental populations promoting biodegradation.

Research stemming from investigations into the environmental fate of pollutants has made major contributions in terms of the isolation of individual strains that can degrade specific compounds. However, it is envisaged that many applications of bioremediation technology will involve interactions between different groups of microorganisms. In these cases, the microbial community is the active agent within bioremediation systems, and the process is concerned with the optimization of the catalytic capability of the community. The desired biocatalytic activity may be derived from a stimulation of the indigenous microbial population or by the introduction of organisms with the necessary catabolic functions. The environmental compartments considered can be “intensive” (the highly controlled and contained systems of reactors) or “extensive” (the wider and open environmental systems concerned with open waters, sediments, soils and aquifers). The selection of the appropriate microbial community for the process will be dependent upon the chemical and physical nature of the contaminating material as well as the environmental compartment itself.

While the failure of microbial communities to promote biodegradation under certain environmental constraints is recognized, it is generally accepted that microorganisms can degrade most anthropogenic compounds, including those of natural origin, but released to the environment in greater abundance by the activities of man (e.g., polycyclic aromatic hydrocarbons from fossil fuel use), and also strictly synthetic organic compounds (xenobiotics). Some important examples of microbial activities in the environment are as follows:

  • The ability of microbial communities/consortia to metabolize and mineralize substrates poorly degraded by pure cultures (e.g., chlorinated aromatic hydrocarbons and alkylbenzene sulfonates).
  • Anaerobic reductive degradation pathways and demonstration of specific reductive dehalogenation reactions (e.g., polychlorinated biphenyls).
  • The oxidative degradation of pollutants under anaerobic conditions (e.g., aromatic hydrocarbons).
  • The existence of microbial communities with potential for remediation of pollutants in deep subsurface sediments, marine, and extreme environments.

The above examples clearly demonstrate the versatility of microorganisms with respect to the degradation of organic compounds. However, it should be noted that the situation is presently much more complex for metals, metalloids, and radionuclides which can only be converted to the base element, methylated, precipitated, volatilized or complexed with an organic ligand., but will always remain the same metal.

The elucidation of metabolic pathways used by microorganisms for the degradation of natural and xenobiotic compounds has been important in developing a quantitative basis for bioremediation in the field. This collective knowledge results in general agreement as to the existence of biodegradative populations being present in most environments. However, it is clear that biodegradative capacity is not universally distributed among all species or for that matter in strains within a given species. As a consequence, degradation of pollutants may be controlled by temporally and spatially heterogeneous mixed populations acting as consortia. In some environments, this contributes in part to the phenomenon of adaptation prior to the onset of degradation, a lag phenomenon which may be controlled at the biochemical, genetic or population level. Under anaerobic conditions, consortia mediating reductive dehalogenation and degradation may well be the major exception.

Given that the vast majority of microbial metabolic processes have yet to be described, it is expected that new routes for the biodegradation of anthropogenic compounds will be discovered. However, if unity among biological systems is accepted, it is also expected that novel routes to the same biochemical endpoint will be the norm.

2.3. Environmental Biotechnology

Collectively, the fields of microbiology, ecology, and engineering provide the foundation for environmental biotechnology. The major objective of this interdisciplinary research area is to provide new and improved strategies for the development and implementation of bioremediation processes. Knowledge of the principles and practices of molecular biology has expanded our current understanding of ongoing processes associated with bioremediation. Molecular technology has shown utility in the description of general genetic mechanisms for adaptation to new environments and elucidation of the composition of genetic elements at the level of DNA. These accomplishments have contributed to the elucidation of biodegradative pathways and factors which control the activity and specificity of such pathways. However, the technology has not yet provided explanations for the adaptation of individual microorganisms to the occurrence of novel compounds: much work remains to be done in this area.

Recent advances in biotechnology provide the capacity to modify organisms at the molecular level for improved degradative performance and have contributed new tools for analysis and monitoring of complex environmental processes. These advances relative to developments in bioremediation include:

  • Patent award for the first genetically-engineered organism, developed specifically for bioremediation.
  • Pathway construction to enhance the biochemical completeness of degradation and spectrum of substrates degraded.
  • Changing regulation of biodegradative operons to achieve more efficient process control.
  • Providing nucleic acid probe and molecular sensor technology for environmental diagnostics and site characterization.

3. Bioremediation Process Performance and Credibility

The fundamental knowledge base and available analytical tools provide exceptional insight into the biological basis of bioremediation processes. While there are differing levels of sophistication and use of the knowledge base in proving the credibility of a bioremediation process, scientifically there is the demand that the biological basis of a field remediation process needs to be verified.

It has been difficult to extrapolate results from laboratory based biodegradation experiments to bioremediation in the field There are also major differences in the comparative interpretation of laboratory biodegradation data with results that indicate apparent bioremediation in the field. These differences relate to the complexity of the field system under investigation and the analytical chemistry and controls that can be extended to complex environmental systems. Only with the general availability of improved analytical methods and instrumentation (e.g., capillary GC/MS and radioisotopes for tracer studies) has it been possible for environmental scientists to provide analytical confirmation and mass balance computations required for the precise verification of biological degradation. Even in well controlled laboratory experiments, competing physical-chemical processes (e.g. photolysis, sorption, volatization, and stripping) complicate the verification and kinetic interpretation of biodegradation.

At present, if is unlikely that closed mass balances can be achieved for all field bioremediation processes. However, the biological nature of the process can be verified as can the effect of engineering intervention on the microbial communities responsible for bioremediation. There is a need for methods to insure that pollutants are not merely being transferred to another compartment not subject to analytical monitoring.

3.1. Current Applications and Research Directions

Numerous examples exist where bioremediation has been practiced at the demonstration and commercial levels. Some pertinent examples include both in situ and on-site treatments, as well as in reactor and in place treatment approaches. These include:

  • land application of petrochemical wastes
  • enhanced indigenous bioremediation of crude oil-contaminated beaches
  • above ground bioreactors for contaminated groundwater
  • in situ stimulation of biodegradation for contaminated groundwater and soils
  • activated sludge and fixed film treatment of pentachlorophenol (PCP) and creosote wood
  • preservative wastes
  • biomass-mediated removal of metals from groundwater and refining process waste water

The SITE Program has also collected in summary a broad description of additional innovative bioremediation process5. Some of these include integration with other treatment processes. For example:

  • surfactant and solvent extraction coupled with reactor treatment
  • soil slurry reactors
  • nutrient blending and soil pile treatment
  • thermal desorption and reactor treatment
  • bioventing

Bioremediation has been successfully applied to sites contaminated with gasoline from leaking underground storage tanks, creosote from the wood-preserving industry as well as industrial solvents. Natural compounds such as petroleum hydrocarbons and other substances derived from plant material are generally biodegradable. The biochemistry involved in the catabolism of all the components of gasoline (aliphatics and BTEX), phenols, cresols, and non-halogenated solvents has been described in detail. All of these compounds can be mineralized under aerobic conditions by the metabolic pathways initiated by oxygenase enzymes. The specificity, regulation, genetics and kinetics of these pathways are known in considerable detail. Recent research has led to similar understanding of the biodegradation of many chloroaromatic, nitroaromatic, and chloroaliphatic compounds. For example, chlorobenzoates, chlorobenzene, methylene chloride, dichloroethane and substituted phenols have been studied extensively, and the aerobic degradation pathways for these compounds are known in detail.

Current research is directed toward achieving comparable understanding of the biodegradation of polycyclic aromatic hydrocarbons, trinitrotoluene, and chlorinated aliphatic solvents such as TCE. Anaerobic degradative mechanisms, removal of metals, degradation of mixtures, and degradation under field conditions are also the subject of current research that can be expected to yield applications in the near term.

3.2. Information Needs

At least two information bases are required for the application of bioremediation technology. One information base requires quantitative knowledge of the parameters needed for optimization of the engineering process. The second requires a broader knowledge of the interactions involved in natural microbial communities. While the first can be viewed as a scale-up need, the second can be considered necessary in order to reduce environmental complexity to ecologically and functionally important variables that may help to unify our ability to predict and control in situ biodegradation and bioremediation.

3.3. Engineering Framework

From an engineering perspective, the overriding concern is the ability to predict with some certainty the outcome of bioremediation. This is necessary because of regulatory requirements and the need to design the most cost effective process.

Many current bioremediation applications are extensions of technologies used for decades in the treatment of municipal sewage or industrial wastewater. Other current applications of bioremediation rely on stimulation of indigenous microorganisms. However, the presence of requisite microbes is necessary but not sufficient for effective bioremediation Successful technology also depends on an understanding the contaminated environment and on proper application of the fundamental principles of microbiology. A number of key factors for successful bioremediation are listed below.

  • Site characterization - Adequate characterization of a contaminated site is essential for effective bioremediation The nature (single compound, mixture, dissolved or free phase), spatial distribution, and concentration of the contaminants are likely to dictate the utility of biological approach for remediation of a site. Geological features (soil type, porosity, stratigraphy, etc) and hydrogeology (location of the water table, direction of flow, etc.) often dictate the ability to provide adequate nutrients needed to enhance natural degradation rates. In addition, the presence of inhibitors such as metals may impair or modulate biological activity. At present, the microbiological information needed for process selection is often neglected during site characterization.
  • Biodegradability of the contaminants - The nature of the organic contaminants often provides an indication of the utility of bioremediation. The range of compounds which can be degraded by microorganisms is very large. In addition to those listed above, microorganisms are known to degrade a wide variety of pesticides, herbicides, industrial chemicals, solvents, fuels, metallic compounds, etc. As currently practiced, bioremediation is most effective for contaminants that serve as sole carbon sources for growth of microorganisms. In addition to an understanding of the biodegradability of the contaminants, knowledge of biochemical mechanisms (and the regulation of gene expression) involved in degradation are often useful in designing the system and may suggest how to manipulate the environment to enhance the activity of the indigenous microbes. For example, are the contaminants known to be more effectively degraded under aerobic or anaerobic conditions? Consideration should also be given to the need for co-substrates, as well as how the presence of mixtures of organic compounds will affect the rate and extent of biodegradation. Of equal importance is an understanding of the kinetics or rates of degradation which determine whether degradation is sufficiently rapid to allow for timely bioremediation of a site.
  • Microbiology - The successful application of bioremediation technology is dependent on an understanding of microbial capabilities and interactions in the environment. For example, it must be known whether the organisms capable of degrading the contaminant(s) are widely distributed in the environment and if there are microorganisms pivotal to biodegradation that are not enumerated from contaminated sites using current procedures (e.g., viable but not culturable). It is also important to know if there are global regulation patterns responding to non-substrate environmental signals which intervene in gene expression and affect biodegradation. In many cases, a variety of microorganisms may be known to degrade the compound. Alternatively, the presence of a unique microorganism or community may be required. An understanding of the regulation and genetics of biological activity is important e.g. will the contaminant serve as an inducer for the requisite enzyme systems. In certain cases, adaptation of the community may be required.
  • Environmental and nutritional factors - A variety of environmental factors, e.g., temperature, pH, ionic strength, redox status, arc known to influence biodegradation rates. If the environmental conditions are not conducive to biodegradation, can they be altered or manipulated? The provision of essential nutrients has often been a key feature of successful bioremediation of contaminated sites. In addition to carbon, heterotrophic microorganisms are known to require a variety of inorganic nutrients for growth. For many current applications, provision of adequate levels of dissolved oxygen or other electron acceptors and nutrients has been sufficient to enhance microbial activity. The environment may also control the availability of the contaminant to the microorganisms. At the present time, there is some controversy as to whether adsorption of organic compounds on surfaces inhibits or enhances biodegradation rates.

3.4. Limitations of Current Knowledge

It should be obvious from the above discussion that the application of bioremediation at a site must address both the heterogeneous nature of the environment, as well as the complexities inherent in using a biological process. Not all sites can be effectively treated using bioremediation. However, there are strong indications that when the fundamentals are applied correctly, bioremediation can be an effective means for remediation of environmental contaminants.

Microbiology plays a major role in bioremediation. However, the fundamental knowledge in microbiology is unevenly divided among biochemistry, genetics, and ecology depending upon the nature of the chemicals to be treated. As was previously indicated successful bioremediation is most easily demonstrated for those chemicals that actually support microbial growth. Consequently, there is reasonable confidence that pollutants such as BTEX. gasoline, and diesel hydrocarbons can be removed under in situ conditions from most environments. It is not coincidental that the existing knowledge of biodegradation for these chemicals is fairly complete and that genes for their biodegradation are rather broadly represented in the microbial community. Maximizing community activity through nutrient supplements and terminal electron acceptors such as O2 brings about a general increase in microbial biomass and activity with concurrent bioremediation. To a lesser extent, this is also true for petroleum and wood-preservative chemical waste, but success can be readily limited by the environmental compartment, lesser degradative potential within the community, and more significant rate limiting effects of solubility and bioavailability. While many halogenated aliphatic and aromatic chemicals can be subjected to bioremediation, there is limited confidence in the ability to predict a successful outcome of the process. Coinciding with this more limited predictability is that degradative mechanisms may be incomplete, co-oxidative or even result in misrouting of toxic metabolites to biochemical pathways thus inactivating degradation. Furthermore, degradation may be more readily accomplished by less controllable aerobic and anaerobic consortia, and the needed genetic information may be only infrequently available in the community unless longer term adaptation is permitted. Non-specific enhancement of community biomass may only result in producing a large non-productive biomass which does not contribute to the degradative process.

3.5. Information Needed to Advance Current Technology

The above differences in bioremediation potential are recognized by the science and engineering community. They have been the subject of several symposia and workshops There is a current demand that bioremediation should be more effective and predictable for major classes of hazardous wastes and contaminants. As a result, serious attention has been paid to the requirements for scale-up and procedures that can overcome critical limiting factors affecting kinetics and process effectiveness. The Bioremediation Action Committee6 has succinctly identified high priority research areas to meet these current challenges, summarized as follows.

  • Overcoming problems of bioavailability
  • Development of new process designs for reactor and in situ bioremediation
  • Scale-up and pilot demonstrations of laboratory processes
  • Development of novel and innovative processes

A recent bioremediation workshop at Rutgers University7 focused on the issue of scale-up from the laboratory to the field, pointing out the needs for:

  • integrating multi-disciplinary efforts on bioremediation assessment
  • Adequate site characterization to meet bioremediation needs
  • Realistic target clean-up goals and criteria
  • Accepted methods and criteria for treatability assessment
  • Identification of rate limiting factors
  • Providing for the availability of a full range of treatment options
  • Adequacy of information for modeling purposes
  • Enhanced process monitoring and mass balance applications
  • Development of cost-effective site-sampling and analysis
  • Development of an improved and accessible database

4. Opportunities for Enhanced Technology

Microbiologists and engineers understand their respective roles in the development of effective and cost-efficient bioremediation processes. They also recognize the need for more information in areas that relate to bioremediation. For example, it is clear that the engineering community needs to identify the minimum information required for process optimization, but it is also clear that engineering of bioremediation requires more detailed microbiological knowledge than normally required for conventional waste biological treatment. It is also clear that major new opportunities exist to develop and apply ecological knowledge biochemical mechanisms and manipulation of their expression to greatly enhance existing and novel in situ processes.

4.1. Improving Process Performance

In general, all organic compounds can be arrayed on a spectrum of degradability that ranges from readily mineralized to totally undegradable. Examples of the latter class of compounds are some polymeric compounds, perfluoroalkyl compounds, and fluorocarbon ethers. Basic research causes us to continually reassess our concepts of biodegradation. For instance, until very recently PCBs and TCE were generally thought to be relatively undegradable. Today they are prime targets for bioremediation (see below). Aromatic compounds were long thought to be non-degradable under anaerobic conditions; now it is known that photosynthetic, fermentative, sulfate-reducing, and denitrifying bacteria can degrade them anaerobically.

Biodegradation of non-growth supporting pollutants is a significant process that must be considered in engineering design and the subsequent application of bioremediation technology for specific pollutants. For example, trichloroethylene (TCE) is a widely distributed subsurface contaminant of groundwater that is degraded by monooxygenase and dioxygenase enzymes which are induced by substrates that are structurally unrelated to TCE. There is a wide range of microorganisms which possess the ability to synthesize oxygenases that degrade TCE. These include organisms that can grow with methane, phenol, toluene, and ammonia. These observations have provided a specific biochemical too! to treat chlorinated solvents.

The efficient utilization of this approach in the field is restricted by a lack of knowledge of the basic principles underlying the phenomenon. Por example, what can be used as an alternative growth substrate specific for the desired organism in order to selectively sustain its existence in the subsurface over other indigenous organisms? For the methane monooxygenase system, for example, 300 moles of methane are required to mediate the transformation of 1 mole of TCE, and the use of methane as a growth substrate is limited by its solubility. For the toluene monooxygenase system in Pseudomonas strain G4, a constitutive mutant has been selected which is beneficial since toluene is not needed for growth and sustenance once the organisms have been put in place in the subsurface or when treatment is in a reactor.

As mentioned previously, reductive dehalogenation is another significant microbial process that has relevance to bioremediation technology. It is only recently that the pure culture studies necessary for understanding these processes has been initiated. Several strictly anaerobic methanogenic and sulfidogenic communities have been shown to mediate dehalogenation of chlorinated alkanes and alkenes that contain 1 or 2 chlorine substituents. Desulfomonile tiedjei is the only available anaerobic model organism which has been shown to reductively dehalogenate, 3-chlorobenzoate. This latter system is, thus far, specific for the 3-chlorobenzoate molecule. The former systems, may be active because of high levels of vitamin B12-like coenzymes in the organisms, a newly observed phenomenon with much to be understood. Nonetheless, the contaminants which potentially can be attacked by such mechanisms range from chloroform to chlorobenzenes to PCBs and dioxins. It is possible that sequential anaerobic/aerobic treatments may lead to extensive mineralization of these problematic contaminants.

4.2. Molecular Improvements in Degradative Capacity

Recent advances in molecular biology allow the regulation of gene expression and the substrate specificity of enzymes to be altered. The expression of catabolic genes is often closely regulated, and degradative activity in the environment can be adversely affected by presence of repressors or the absence of inducers. This can be overcome by replacement or modification of the endogenous promotor(s) so that gene expression is not dependent on the presence of specific compounds or environmental factors. Depending upon circumstances, constitutive expression or activation of degradative genes in response to temperature, chemicals or specific environmental factors can be obtained. Under the appropriate conditions, these alterations can significantly enhance the degradation potential of the organism resulting in a more effective process at lower cost. Pertinent examples of relevant use of genetic engineering technology to enhance bioremediation include:

  • Controlling toluene monooxygenase mediated TCE degradation by placing enzyme induction under temperature regulation to overcome the requirement for a chemical inducer. Such strains would seem to have immediate applications in confined reactor treatment systems.
  • Expanding the range of degradative performance of Pseudomonas strains by introduction of TOL and NAH plasmid degradative genes to permit degradation of chlorobenzoates, phenols and chlorosalicylates.
  • Exploring the use of gene sequence specific alterations to expand the substrate specificity of enzymes involved in PCB degradation.
  • Examining the possible alteration metabolic pathways to avoid the build-up of toxic products such as chlorocatechols which inhibit the degradation of wood processing wastes.

Genetic engineering has resulted in astounding improvements in performance of industrial microorganisms which are utilized in bioreactors in conventional biotechnology. In these cases, environmental conditions are precisely controlled and matched with the characteristics of the organisms in order to optimize catalytic activity. It is anticipated that such advances can be also applied to bioremediation processes carried out in bioreactors. The efficacy of genetic modifications that lead to enhanced performance in bioreactors may, however, be lower in natural environments where conditions can be less well controlled, particularly where the modification does not relate to faster catabolism of a pollutant growth substrate. Therefore, much needs to be learned before a high degree of predictability is attained on the consequences of specific genetic changes for performance in the environment. Microcosms and reactor systems will be instrumental in assessing the utility and optimizing genetic strategies to increase biodegradation performance in the environment.

4.3. Problems with Multicomponent Mixtures

The design of a process to meet a specific bioremediation objective requires knowledge of the kinetics of biodegradation. It has been possible to use simple kinetic expressions of the Michaelis-Menten or Haldane form to express the impacts of the concentration of organic compounds on microbial specific growth rates. Unfortunately, it is currently impossible to write kinetic expressions depicting the effect of specific growth rate on the concentration of a single organic constituent in a multicomponent system. As a consequence, in the absence of extensive treatability data, it is impossible to design a biological treatment system of any type, whether above ground or in situ, to achieve a predictable degree of destruction of an individual organic pollutant in complex mixtures.

The inability to predict the outcome of multicomponent substrate biodegradation stems directly from a lack of fundamental knowledge of how microbes respond to mixtures of organic substrates, either singly or in complex mixtures. For example, little is known about the regulation of enzyme levels under low growth rate conditions where bacteria are simultaneously degrading several organic compounds. Consequently, it is very difficult to begin to draw generalizations about responses that can be depicted mathematically in simple kinetic expressions.

As described earlier, molecular techniques exist for expansion of the range of substrates degraded by individual organisms. However, naturally-occurring strains such as Pseudomonas strain JS150 have been found to degrade up to 150 individual contaminants. If the biochemical understanding of the sequential or simultaneous nature of enzymatic reactions in such strains can be achieved, it is likely that kinetically-engineered processes can be designed that take advantage of the biochemical abilities of the organisms.

4.4. Problems of Contaminant Concentration

Two general situations are in need of study, and they represent the opposite poles of a continuum. As mentioned above, information is required that relates to the simultaneous degradation of several compounds that are all present at low concentrations. In particular, there is a need to know the factors responsible for the regulation of enzyme production and activity under these conditions. For example, if a single bacterial species is growing on two or more compounds at a low specific growth rate, there is no information on changes in the quantities and activities of key enzymes relative to the same organism growing at the same specific growth rate on only one of the compounds. These effects cannot be expressed mathematically in the relatively simple terms needed for process engineering. Likewise, when two or more species are present, it is not clear whether specialists predominate over generalists or what approach might be taken to express the kinetics mathematically. These problems may seem rather naive, but they suggest the almost total lack of information on a topic that is fundamental for engineers to design systems to achieve specific outcomes relative to individual contaminants.

At the other extreme, information is needed about degradation of compounds at higher concentration, although more is known here. For example, significant information is available for regulatory mechanisms such as catabolite repression and mathematical models are available that approximately describe the system response, although they are complex. Less well developed is knowledge about growth inhibition by high concentrations of inhibitory materials, particularly in mixtures. Mathematical models are available that can depict the impact of an inhibitory material on the growth rate of bacteria growing on a noninhibitory substrate. It is currently impossible however, to predict and describe antagonistic or synergistic effects of mixtures of inhibitors.

5. Technology Development-Exploiting the Exploratory Research Base

Research accomplishments over the past decade have provided new insights that are cause for an optimistic outlook that future exploratory research can make major new contributions to bioremediation. This optimism is based on several factors:

  • Exploratory research is being directed specifically toward problem areas limiting bioremediation.
  • There is a consciousness of a real need to scale-down environmental complexity to relevant and realistic laboratory simulations.
  • Major environmental and ecological processes most likely to affect bioremediation have already been identified as critical knowledge gaps.
  • Revolutionary new molecular technology is becoming available for the development of environmental and ecological bioremediation processes.
  • Innovative reactor designs are being considered for specific optimization of cometabolic and consortia-mediated bioremediation.

Major contributions that will enhance our current understanding of bioremediation processes will be generated by fundamental research on the biochemistry, genetics and ecology of bacteria fungi, algae, plankton, protozoa, and plants. These results will improve current remediation processes and aid in development of new technology.

5.1. Knowledge Gaps Affecting Integration of Disciplines in Bioremediation

It is clear that the potential of microbes for bioremediation is both enormous and enormously underexploited. However the efficient utilization of microbes is limited by significant knowledge gaps. These include the need to improve the performance of biological catalysts and the creation of new ones to improve their predictability in open systems and to improve monitoring and assessment procedures. Major research areas and exploratory questions that cut across disciplines include:

5.1.1. Microbial biofilms and activities at interfaces.

As a predominant growth form, biofilms may be manageable, and exploratory research is needed to determine maintenance of exogenous or indigenous degradative microorganisms in biofilm communities and the ability to use these organisms to enhance bioremediation or reduce toxicity.

There is a need to define the roles and applications of biosurfactants, emulsifiers, and exopolymers in bioavailability and immobilization of hydrophobic contaminants and metals In addition, it would be important to know il biosurfactants can be modified to create synthetic “adapters” that increase the rate of transport and degradation of pollutants.

Exogenous surfactants and other agents used to mobilize contaminants may be exploited to transport and disperse degradative organisms from biofilms, yet there is little information on these processes and potential applications.

Nutrients may be supplied in the gas phase rather than in a saturated aqueous environment to overcome mass transfer problems and avoid anaerobic conditions; however, this remains an underexploited area of environmental research.

The extent the biofilms act synergistically with surface-catalyzed phenomena on clay minerals or alumina and ferric oxides to facilitate degradation remains largely unknown. Reactions at catalytic mineral surfaces, in addition to reactions catalyzed by enzymes, may play a role in the degradation of perfluoroalkyl compounds and fluorocarbon ethers which are poorly soluble in organic and aqueous solvents. It is also possible that steric constraints in porous minerals may result in the formation of different metabolites to those produce under unconstrained conditions.

Knowledge from such research will have obvious in situ bioremediation consequences, but can also lead to new bioreactor designs and may demonstrate the potential for solid phase biocatalysis.

5.1.2. Microbial responses to multipollutant mixtures.

Microbial communities are generally confronted simultaneously by a multitude of organic and inorganic substrates, yet the selection and kinetics of multiple substrate uptake and utilization are virtually unknown.

The resistance or detoxification mechanisms for organics, inorganics, and metals that allow microbial communities to thrive in the environment is grossly underrepresented in our current knowledge, and the extent to which these detoxification mechanisms can be exploited to sequester, immobilize, concentrate or recover chemicals and metals that inhibit or are kinetically resistant to degradation is poorly developed.

Studies on the construction of metabolic pathways that avoid the build-up of contaminants due to metabolite misrouting are in their infancy. The same can be said for the potential use of anaerobic and aerobic consortia and/or co-meta holism as a pretreatment for mineralization of mixed organics.

5.1.3. Dynamics of microbial community structure and function.

Communities demonstrating qualities of homeostasis and robustness may be highly resistant to change. It is important to determine if new degradative activity can be introduced and maintained in such communities without constant engineering management.

Currently, it is nearly impossible to determine if dynamic conditions or induced perturbations (e.g., biocides) create conditions for the maintenance or loss of new degradative capabilities in microbial communities.

Stress responses (e.g., temperature, O2, metals. UV. etc.) exist that can be exploited to manage or control at the molecular or population level the growth and degradative activities of organisms within a community.

Dynamic conditions can be manipulated (e.g., aerobic-anaerobic gradients), yet it remains to be determined if activities such as oxygenase-dependent and reductive pathways can operate discretely in time and space to maximize degradation.

The extent to which specific and selective metabolic inducers or growth substrates can be used to control the activity or optimize biomass production of degradative organisms in mixed communities has yet to be fully investigated.

5.1.4. Site characterization, process monitoring, and optimization.

Biological characterization can provide immediate knowledge of the capacity of a site for bioremediation as well as provide a source for novel biodegradative processes and organisms.

The application and need of powerful new techniques of molecular biology (DNA RNA probes, bioluminescent reporters, etc.) for in situ diagnosis of degradative capacity and for on-line process performance monitoring and control requires definition and clarification.

New genetic potential and biochemical mechanisms remain to be discovered and exploited for novel process development, molecular engineering, and advanced monitoring and control.

Potential exists for plant or rhizosphere induced dynamics to influence site microbial activities, and organismal and molecular strategies can be developed to use plants to manage near surface soil contamination.

5.1.5. Integrating molecular genetics and physiology with environmental needs.

There is a major need for clear communication of the powerful developments in modem biology, both tools and knowledge, in environmental problem solving. However, applications for this information are also highly dependant on problem definition.

There is clear potential for the development of designer genes and genetic operons for biodegradation and bioremediation purposes. These developments are dependent on fundamental research.

Future applications will require the development of extensive data bases on the sequences of genes that are responsible for the synthesis and control of enzymes that degrade pollutants. Studies on the three dimensional structures of these enzymes will be required for molecular modeling and gene construction that will lead to the production of enzymes with superior degradative abilities.

Further fundamental research on the genetic and physiological basis of gene regulation and expression, response to environmental parameters and stress factors will make major contributions in the prediction of degradation kinetics, the development of accurate simulation models, and the construction of modified strains.

At present, there are no procedures available for predicting gene exchange and evolution of biodegradative pathways in the environment. This information is needed in order to accurately develop and assess approaches for facilitating the adaptation and evolution of environmentally relevant processes in individual microbial species and communities mediating bioremediation.

5.2. Model Development

The major research issues discussed above must be framed in the context of eventual engineering use. In this area, there are major simulation model limitations that prohibit predicting process performance and extrapolation. While complex models have been developed, then use has been constrained by major problems of parameter estimation. Several difficulties exist with the assumptions that are made by modelers in the absence of specific quantitative information. Frequently, models assume that one organism degrades one substrate, and one differential equation is developed for each, given a Vmax and Km value from batch/chemostat experiments or from published sources. Or, it is assumed that each transformation reaction is caused by a constant fraction of total biomass, based on energy flows. In either case, measurement of biomass and bioactivity of specific organisms is problematic. Perhaps, molecular tools can be used to solve this problem. If the model assumes a different Vmax and Km value for the suite of total biochemical reactions possible (i.e., permutations of m organisms degrading n substrates), it quickly becomes a large problem with great difficulty in measuring and verifying the necessary parameters. Still, a more complicated model may not necessarily address such important issues as microbial adaptation, kinetic effects of varying electron acceptors, and toxic intermediate products.

Prediction of the efficacy of bioremediation needs a wholly new approach involving mixed culture mixed substrates. Kinetic models must be developed and coupled to existing hydrogeochemical transport models to make predictions (forecasts) of the potential success in using bioremediation technology.

5.3. Ecological Verification and Process Credibility

A site-related research question is the need for “scaled-down” and accurate simulations for evaluating and verifying bioremediation. Perhaps the most important factors lending to undermine user confidence in bioremediation technology are the lack of adequate performance standards. Practitioners must collect the necessary data to convince clients as well as the larger scientific community that some beneficial process has actually occurred as a result of their efforts. A corollary may also be that any ecological impact associated with the technology will be slight. If proof of bioremediation attempts can be gleaned with time and attention to the framework outlined below, the extrapolation of biodegradation information between sites with similar contamination will be facilitated.

Implicit in the above, is the development of environmentally relevant test systems with which to evaluate remediation scenarios. The design of such test systems requires some appreciation for the salient site characteristics likely to influence the success of the remedial approach. Even a cursory examination of site characteristics (e.g., soil type, toxic inhibitors, degradative potential, etc.) may lead to an appreciation of site limiting factors. If remediation is still deemed feasible, potential scenarios can be evaluated under more environmentally realistic conditions.

Past experience shows that natural environments are variable such that the distribution of contaminants, microorganisms, and microbial activities are typically heterogenous. This variation should not be noted and then promptly ignored; instead, an effort should be directed toward the development of statistically appropriate sampling technology to evaluate environmental data in a meaningful and interpretable fashion.

Several lines of evidence are required to demonstrate the efficacy of bioremediation technology. It may be possible to demonstrate that the mass of contaminant decreased as a result of a bioremedial action; this determination must be made relative to abiotic fate processes and untreated controls. While the calculation of adequate contaminant mass balances may prove difficult, other options are still available. For example, it may often be easier to monitor and demonstrate the consumption of essential nutrients, inducers, co-substrates or electron acceptors that are employed as part of the remedial effort. Alternatively, other evidence for microbial activity can be provided from measurements of uniquely biological end products, such as CO2, CH4, N2O. H2S and others relative to control areas. Similarly the search for and detection of metabolic intermediates known to be associated with the metabolism of the contaminant can be targeted. The detection of such intermediates in the treatment areas but not in the untreated areas would forcefully argue for a bioremedial response. Other uniquely biological responses, such as the selective removal of chemicals, congeners, enantiomers, etc., relative to the other chemical fractions that are deemed more recalcitrant materials may be indicative of success.

Evidence for the successful application of bioremediation technology can be seen in the response of the specific microorganisms or genes responsible for the bioremediation activity under consideration. It is possible that advances in molecular techniques will allow the monitoring, perhaps on-line, of such events (i.e., growth or activity of organisms or the expression of specific genes associated with degradation) with increasing accuracy. Such responses need to be evaluated relative to background or control regions of the environment.

5.4. Non-indigenous Organisms

It is generally believed that non-indigenous organisms, whether native or engineered, cannot be established in specific environments for remediation purposes. This concept is based on little fact and less research. Evidence does exist that such organisms can persist in groundwater microcosms, in reactors, and in subsurface soil in the field. However, the question of persistence, especially of genetically engineered microorganisms, remains an area of uncertainty.

Given the fact that indigenous degradative organisms may be in low abundance, a situation that may not be optimal for process performance, the use of non-indigenous organisms becomes a wide open science and engineering research question. Excellent molecular tools, engineering simulations, and ecological models exist that can be taken advantage of to explore the use of such organisms, which to date has been hindered by intellectual, emotional, and regulatory constraints. The opportunity to capitalize on rapidly advancing biological technology may be severely limited if these constraints are not overcome

6. A Need for Site Directed Research and Performance Verification

A major problem in the development of bioremediation technology is the lack of field sites that are well-characterized with respect to contaminants, geohydrology, and geochemistry; such sites are urgently needed for understanding the natural events that are taking place and also for the transfer technology developed in the laboratory to field conditions. An integrated interdisciplinary approach is essential for the application and verification of bioremediation, and this can only be achieved under environmental conditions. Although some sites may already exist, their openness and flexibility of use is unlikely to support more than a few efforts in the bioremediation community.

7. Conclusions

  • Bioremediation as a group of technological processes is supported by a broad science base. There is no reason to believe that it is universally effective. Effectiveness is largely related to the class of chemicals to be degraded and the specific environmental or reactor design in which bioremediation is attempted.
  • Predictability of process performance cannot be made with a high level of confidence. In some cases, predictability is limited by the lack of biological information, in other cases by lack of accurate parameter estimation and availability of appropriate models.
  • Modem biotechnology has been responsible for the rapid advances in the sciences supporting bioremediation. Most of these advances have yet to be incorporated into engineering practice
  • There is great optimism for future scientific advances in the discovery and development of novel bioremediation processes and biological agents and in understanding the environmental regimes and control parameters that can enhance the use of bioremediation for in situ applications.
  • There costs a vibrant science and engineering research base which is supported, albeit inadequately, by a variety of agencies to promote immediate process applications as well as longer term exploratory research.
  • The knowledge base developed for the bioremediation of soils, and groundwater will have a beneficial effect in terms of the development of biological processes for the prevention of pollutant release and the recycling of wastes (i.e., metal recovery).
  • There is a need to orient aspects of bioremediation research to modern biotechnically integrated science and engineering effort using defined field demonstration sites as vehicles for integration.
  • There is a need for realistic economic analyses, of costs and cost saving, in the use of bioremediation as compared to other systems for hazardous waste management and to promote research, development, and demonstration of the next generation technology. Given the magnitude of the cost of hazardous waste management and the potential savings bioremediation may create, it can be anticipated that the current investment in bioremediation research is very far from the inflection point on a diminishing return curve.

These conclusions and recommendations are strengthened by those of other conferences and workshops which over the past decade have emphasized the potential for a dramatically expanded knowledge base, the need for cross-disciplinary integration and research training in the biotechnical areas supporting bioremediation, and the enormous potential for engineering the microbial community using the rapidly advancing knowledge and technology of molecular biology.

The White House Presidential Initiative for Biotechnology for Fiscal Year 93 represents an opportunity for the development of a basic and applied strategic research plan for bioremediation8. Environmental biotechnology related research is expected to increase by $14.7M over current funding of $68.6M. Past funding activity placed about 70% of these resources in bioremediation and treatment biosystems research which would translate to approximately S9M in new resources. While these resources are modest given the magnitude of the problem, they can be used to initiate a coordinated interdisciplinary research effort to fill major gaps in knowledge relating to bioremediation. Significant supplemental and continuing funding will be required to develop the technology fully and to utilize the expanding knowledge base of modern biology to advance not only bioremediation, but also related innovative technology.

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Copyright 1992 American Academy of Microbiology.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Bookshelf ID: NBK561280PMID: 32865937DOI: 10.1128/AAMCol.10Apr.1992


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