Sarat Kannepalli^1,, Kenneth W. Farrish¹

A laboratory bioremediation study was conducted on perchlorate contaminated soils from the Longhorn Army Ammunition Plant (LHAAP), Karnack, Texas, USA. In this study, the effects on perchlorate bioremediation of five carbon substrates, fertilization and prior exposure to the contaminant by the native soil microorganisms were explored in microcosms over a five week period. Biostimulation of native soil microorganisms to degrade pollutants is widely practiced as it increases the rate of natural attenuation, which is otherwise slow. The five carbon substrates studied were: chicken litter, biosolids, yeast extract, sodium acetate, and cornstarch. Among the five carbon sources, unfertilized chicken litter treatment in unsterilized soil was quickest in reducing perchlorate. In these flasks, perchlorate concentrations fell below detection limit from an initial mean concentration of 220 mg/L by the end of first week. There was a significant negative effect (p < 0.05) of fertilization in chicken litter treatments on perchlorate degradation. In unsterilized condition, unfertilized chicken litter treated flasks reduced perchlorate quicker than the fertilized treatments. In fertilized treatments there was a significant effect (p < 0.05) of soil sterilization on perchlorate degradation. Chicken litter treatments with unsterilized soil degraded perchlorate to below detection limit quicker (< 2 weeks) than chicken litter with sterilized soil (4 weeks). The results suggest that application of inexpensive carbon substrates such as chicken litter without the need for addition of chemical fertilizers may be a feasible remediation strategy in perchlorate contaminated soils with large active, native microbial populations.

bioremediation, biostimulation, perchlorate, soil contamination, carbon amendments, native soil microorganisms