Low aqueous solubility electron donors for the reduction of nitroaromaticsin anaerobic sediments

Studies are presented investigating the ability to enhance aryl nitro-reduc tion processes in sediments through electron donor addition. In particular, high molecular weight (starch and guar gum) and/or low aqueous solubility electron donors (oleic acid) were studied, since they should be less prone to diffusive loss to the water column after addition to contaminated areas. For comparison, complimentary studies were conducted with water-soluble el ectron donors (acetate and dextrose). The ability to enhance activity was m easured by methane production and reduction of either nitrobenzene or 1,3,5 -trinitrobenzene to aniline or dinitroaniline. The results demonstrate that all electron donors resulted in increased methane production after a lag p hase. The highest level of methane production and the shortest lag phase in uncontaminated sediment microcosms was observed in acetate-fed systems. So rption studies of all electron donors showed that starch was partitioning t he least into the water phase. In microcosms containing nitrobenzene, trini trobenzene and acetate, methane production did not occur and nitro-reductio n was not observed. Conversely, the addition of dextrose or starch yielded methane production and aryl nitro-reduction with each contaminant tested. N either nitrobenzene nor trinitrobenzene was significantly reduced in HgCl2- killed controls. From these studies, it appears that starch may be well sui ted for applications of in-place, anaerobic sediment bioremediation. (C) 19 99 Elsevier Science B.V. All rights reserved.