CYCLODEXTRIN EFFECTS ON THE EX-SITU BIOREMEDIATION OF A CHRONICALLY POLYCHLOROBIPHENYL-CONTAMINATED SOIL

The possibility of enhancing the intrinsic exsitu bioremediation of a chronically polychlorinated biphenyl-contaminated soil by using cyclod extrins was studied in this work. The soil, contaminated with a large array of polychlorinated biphenyls and deriving from a dump site where it has been stored for about 10 years, was found to contain indigenou s cultivable aerobic bacteria capable of utilising biphenyl and chloro benzoic acids. The soil was amended with inorganic nutrients and biphe nyl, saturated with water, and treated in aerobic batch slurry- and fi xed-phase reactors. Hydroxypropyl-beta-cyclodextrin and gamma-cyclodex trin, added to both reactor systems at the concentration of 10 g/L at the 39th and 100th days of treatment, were found to generally enhance the depletion rate and extent of the soil polychlorobiphenyls. Despite some abiotic losses could have affected the depletion data, experimen tal evidence, such as the production of metabolites tentatively charac terized as chlorobenzoic acids and chloride ion accumulation in the re actors, indicated that cyclodextrins significantly enhanced the biolog ical degradation of the soil polychlorobiphenyls. This result has been ascribed to the capability of cyclodextrins of enhancing the availabi lity of polychlorobiphenyls in the hydrophilic soil environment popula ted by immobilised and suspended indigenous soil microorganisms. Both cyclodextrins were metabolised by the indigenous soil microorganisms a t the concentration at which they were used. Therefore, cyclodextrins, both for their capability of enhancing the biodegradation of soil pol ychlorobiphenyls and for their biodegradability, can have the potentia l of being successfully used in the bioremediation of chronically poly chlorinated biphenyl-contaminated soils. (C) 1998 John Wiley & Sons, I nc.