Biogroup   EOS Remediation: Your Natural Solutions

Welcome to the
Bioremediation Discussion Group
Home Page






The BioGroup includes over 2,400 members worldwide, including environmental consultants, industry representatives, regulators, researchers, educators, students, and others with diverse backgrounds in education and experience. Due to the complex biogeochemical processes that control biotransformation, BioGroup membership is open to environmental engineers, hydrogeologists, soil scientists, microbiologists, environmental chemists, and all who wish to contribute to this important topic. For information on joining the BioGroup, please select "Membership Info". For member comments about the BioGroup, please select "Member Comments".

Bioremediation has proven to be an important remediation technology because it:

  • Harnesses naturally-occurring biogeochemical processes;
  • Destroys or immobilizes contaminants rather than transfers them from one environmental media to another; and
  • Conserves limited financial resources due to shortened cleanup times and/or lower capital expenditures relative to many other remediation technologies.
Additional information on bioremediation is provided below and in BioLinks.


Common Soil Bacteria Pseudomonas Aeruginosa
Bioremediation of unconsolidated materials, bedrock, groundwater, and other media contaminated with synthetic organic/inorganic compounds is an emerging technology that can cost-effectively treat many sites. Bioremediation is defined by the American Academy of Microbiology as "the use of living organisms to reduce or eliminate environmental hazards resulting from accumulations of toxic chemicals and other hazardous wastes" (Gibson and Sayler, 1992). The technology is approved by the United States Environmental Protection Agency, Environment Canada, and other regulatory agencies worldwide. Applied research is underway at public and private facilities worldwide. Links to numerous research facilities are included at BioLinks.

Intrinsic (passive) bioremediation of many synthetic organic compounds is carried out by indigenous microorganisms, principally heterotrophic bacteria, that transform contaminants to intermediate products or innocuous end products, or immobilize them. In many cases, contaminants such as petroleum hydrocarbons serve as sources of organic carbon and electron donors (assimilation). In other metabolic processes, contaminants such as trichloroethene may serve as electron acceptors (reductive dehalogenation), or may be transformed by fortuitous co-metabolic processes that offer no added benefit to microbes from the reactions (co-oxidation). These processes occur within a wide range of hydrogeologic settings, and biogeochemical interactions among formations, microorganisms, and contaminants control attenuation pathways and rates.

Electron Theory
Courtesy of Daniel Gallagher, Ph.D., Virginia Tech
The objective of a bioremediation program is to immobilize contaminants (reactants) or to transform them to chemical products no longer hazardous to human health and the environment. For certain cases in which contaminants pose no significant risk to sensitive receptors (e.g., water supply wells, surface water bodies), intrinsic bioremediation may be an appropriate strategy. For other cases in which receptors are at risk, an enhanced (engineered) bioremediation strategy may be necessary. Enhanced bioremediation can be performed in-situ (e.g., biosparging; bioventing, Figure 1; hydrogen peroxide/inorganic nutrient amendment) or ex-situ (e.g., land farming, biopiles Figure 2a and 2b), depending on a variety of site-specific factors and the constraints imposed by site usage. In many instances, biostimulation activities may be limited to electron acceptor (e.g., molecular oxygen, nitrate, etc.) amendment, however, in other cases inorganic nutrient amendment or pH adjustment may be required. Typically, indigenous microbes are capable of effecting transformation because they are acclimated to the contaminant as well as their microniche; however, research is currently underway at a number of facilities using exogenous, specialized microbes or genetically engineered microbes (GEMs) to optimize bioremediation. This approach, referred to as bioaugmentation, may be appropriate for ex-situ bioremediation projects, but has yet to be proven effective in-situ.

Courtesy of Jiri Damborsky, Ph.D.
Bioremediation is not a panacea for soil and groundwater contamination. A successful, cost-effective bioremediation program is dependent on hydrogeologic conditions, contaminant signature, microbial ecology, and other spatial/temporal factors that vary widely. Biotreatability studies are necessary components of the program so that remedial design data are collected cost-effectively. Biotreatability studies are performed to evaluate whether site conditions are conducive for bioremediation. Typical elements include, but are not necessarily limited to, the following:

  • Literature reviews to assess biodegradability using both hard copy publications and on-line resources such as BioReferences, University of Minnesota's Biocatalysis/Biodegradation Database, and Selected Water Resource Abstracts of the USGS;
  • Screening studies to obtain biodegradation indicator parameter data such as electron acceptors/donors, oxidation-reduction potential, and pH;
  • Microbiological assays to assess microbial growth conditions, degrader population densities (Figure 3), and presence of enzymes capable of destroying contaminants of concern; and/or
  • Microcosm studies to evaluate bioremediation potential under controlled conditions. Please refer to Figure 4a and 4b for examples of laboratory-scale microcosm study setups for the unsaturated zone, and to Figure 5 for an example of a laboratory-scale microcosm study setup for the saturated zone.

During implementation of bioremediation programs, performance monitoring plays a key role in evaluating treatment effectiveness. Biodegradation monitoring objectives are generally to evaluate contaminant attenuation over time and protect sensitive receptors.

Bioremediation programs that address these factors will have the greatest likelihood of success and will conserve limited financial resources. Properly executed, bioremediation can expeditiously destroy or immobilize environmental contaminants in a manner that is protective of human health and the environment.

Gadd, G.M., 1993,
Trends in Biotechnology, Elsevier Science, v. 11, p 348

References Cited

Gibson, D.T., and Sayler, G.S. 1992. Scientific Foundations of Bioremediation: Current Status and Future Needs. American Academy of Microbiology, Washington, D.C., USA

Jorgensen, B.B. 1989. Biochemistry of Chemoautotrophic Bacteria. In Schlegel, H.G. and Bowien, B. (editors), Autotrophic Bacteria, Science Technology Publishers, Madison, Wisconsin, USA, p. 117-146