Monitoring of Desulfitobacterium frappieri PCP-1 in pentachlorophenol-degrading anaerobic soil slurry reactors

Anaerobic biodegradation of pentachlorophenol (PCP) was studied in rotative bioreactors containing 200 g of PCP-contaminated soil and 250 ml of liquid medium, Reactors were bioaugmented with cells of Desulfitobacterium frappi eri strain PCP-1, a bacterium able to dehalogenate PCP to 3-chlorophenol. C ells of strain PCP-1 were detected by quantitative PCR for at least 21 days in reactors containing 500 mg of PCP per kg of soil but disappeared after 21 days in reactors with 750 mg of PCP per kg of soil. Generally, PCP was c ompletely removed in less than 9 days in soils contaminated with 189 mg of PCP per kg of soil. Sorption of PCP to soil organic matter reduced its toxi city and enhanced the survival of strain PCP-1. In some non-inoculated reac tors, the indigenous microorganisms of some soils were also able to degrade PCP. These results suggest that anaerobic dechlorination of PCP in soils b y indigenous PCP-degrading bacteria, or after augmentation with D. frappier i PCP-1, should be possible in situ and ex situ when the conditions are fav ourable for the survival of the degrading microorganisms.