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J. Great Lakes Res. 16(3):337-338Internat. Assoc. Great Lakes Res., 1990
EDITORIAL
BIOLOGICAL REMEDIATION OF CONTAMINATED SEDIMENTS
Chad T. JafvertEnvironmental Research Laboratory
U.S. Environmental Protection AgencyAthens, Georgia 30613
The current state-of-the-science of biological remediation of contaminated sediments was discussedin a recent workshop. Special emphasis wasdevoted to remediation alternatives for sedimentswithin the Great Lakes basin. The workshop, held17-19 July 1990 in Manitowoc, Wisconsin, wassupported by the U.S. EPA, through the Assessment and Remediation of Contaminated Sediments (ARCS) Program, and by EnvironmentCanada. More than 60 scientists from state andfederal agencies, academia, and the private sectorfrom the United States, Canada, and The Netherlands participated. For the purpose of the workshop, the sediments of primary interest were thosewithin the Areas of Concern identified by theU.S.lCanada International Joint Commission'sGreat Lakes Water Quality Board. Most of the 42Areas of Concern are located in harbors, bays, orriver mouths; 25 are located within U.S. waters, 12within Canadian waters, and 5 within internationalchannels. Remedial Action Plans currently arebeing developed for these areas under the 1987revision of the Great Lakes Water Quality Agreement. A major purpose of EPA's ARCS Programis to evaluate remediation alternatives for the riskassessment and cleanup of these sites with specialemphasis given to five sites. These five are Ashtabula River, Ohio; Buffalo River, New York; Sheboygan River, Wisconsin; Grand Calumet River,Indiana; and Saginaw River and Saginaw Bay,Michigan. Two of these five overlap EPA Superfund sites to some extent.
During the workshop, presentations were madedescribing site characteristics of the five primaryU.S. Areas of Concern and for Hamilton Harbour,Ontario. Major contaminants within these andother Areas of Concern include polychlorinatedbiphenyls (PCBs), polycyclic aromatic hydrocar-
337
bons (PAHs), and various heavy metal species. Thetoxicity and recalcitrant nature of these compounds have caused serious environmental concern. Moreover, these classes of contaminantspresent serious and rather complex treatabilityproblems for essentially all remediation technologies (including biological processes). However, anobvious advantage of properly engineered biological treatment is that complete mineralization of theorganic contaminants can occur, thereby permanently removing these compounds from theenvironment.
The remainder of the workshop was devoted todiscussing related laboratory and field studies andthe applicability of biological remediation processes for these contaminants. Workshop presentations and discussions underscored the fact that biological remediation technologies for these classesof compounds are in rapid development, and insome situations may warrant evaluation as a component(s) in remediation strategies, especiallywhen confined disposal options are leading alternatives. For PCB mixtures (aroclors), anaerobicreductive dechlorination, shown by several investigators to occur in both historically contaminatedsediments at various sites and in laboratory spikedsediments, results in the same molar concentrationof PCBs with fewer average chlorines per molecule. While this process reduces toxicity alone, further aerobic treatment, believed to be partially acometabolic process, may result in complete mineralization. For PAH compounds, aerobic microbial and fungal decomposition is fairly well documented, whereas biological treatment of sedimentsfor the remediation of metal species has been considered only recently. In related areas, however,microbially mediated precipatation and/or dissolution reactions of metal species have been effec-
338 c. T. JAFVERT
tively utilized. An example of this is the treatmentof acid mine drainage by artificial wetlands.
The purpose of all bioremediation strategies is toenhance these processes, which occur by specificorganisms or a microbial consortium by controlling nutrient and oxygen (or other terminal electron acceptor) supply, by controlling the concentration of organic or inorganic microbialinhibitors, by reducing competitive biological orchemical reactions, and in some cases, by increasing the microbial availability of the contaminants.Generally, these and other controlling factors canbe evaluated at the bench-scale level. A standardized testing protocol that could be used as a guideline and quality control measure for such benchscale treatability studies would be useful toscientists designing and performing these studies,
as well as to those who must evaluate the results. Inmany cases, variations in the controlling factorsare major reasons for the site (or sediment) specificnature of biological treatability successes, and possibly can be flagged at the bench-scale level.
Extrapolating these bench-scale results to thefield requires knowledge and input from diversedisciplines, including biology, chemistry, geochemistry, engineering, toxicology, hydrology, and statistics. It is also clear that before we embrace biological remediation as the answer to all ourcontaminated sediment woes - or on the otherhand, label these technologies as totallyimpractical- results of several field-scale demonstrations must become available. As with any technology, experience leads to refinement and a betterdefinition of practical limits.