EFFECTS OF HYDROCARBON ENRICHMENT ON TRICHLOROETHYLENE BIODEGRADATIONAND MICROBIAL-POPULATIONS IN FINISHED COMPOST

This study focused on the capacity of finished compost, often used as packing material in biofiltration units, to support microbial biodegra dation of trichloroethylene (TCE). Finished compost was enriched with methane or propane (10% head space) to stimulate cometabolic biodegrad ation of gaseous TCE. Successful hydrocarbon enrichment, as indicated by rapid depletion of hydrocarbon gas and measurable growth of hydroca rbon-utilizing micro-organisms, occurred within a week. Within batch r eactor flasks, approximately 75% of head space TCE (1-40 ppmv) was rap idly sorbed onto compost material. Up to 99% of the remaining head spa ce TCE was removed via biodegradation in compost enriched with either hydrocarbon. Hydrocarbon enrichment with methane or propane correspond ed to 10-fold increases in methanotrophic or propanotrophic population s, respectively. Based on growth assessment under different nutritiona l regimes, there appeared to be complex metabolic interactions within the microbial community in enriched compost. Five separate bacterial c ultures were derived from the hydrocarbon-enriched compost and assayed for the ability to degrade TCE.