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-

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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.