Reductive Dechlorination of 2,3,4-Chlorobiphenyl by Biostimulation and Bioaugmentation

Abstract

Abstract

Dechlorination ability of indigenous microorganisms from seven stream sediments collected around Bangkok and its vicinity in Thailand was tested by amended with seven polychlorinated biphenyl congeners (PCBs) including 2,3,4-chlorobiphenyl (234-CBp), 22′5-CBp, 24′5-CBp, 22′35′-CBp, 22′45-CBp, 23′44′5-CBp, and 22′34′5′6-CBp. After 2–22 weeks of incubation, 234-CBp dechlorination could be initiated and dechlorinated to 24-CBp in all seven sediment slurry without any further enrichment, with dechlorination completed within 28 weeks. This is the first evidence indicating that 234-CBp dechlorination consortium actually existed in the natural streams of Thailand and could perform the 234-CBp dechlorination in the fresh sediment slurry without any nutrient amendment. The lag phase of 234-CBp was shortest in the sediment slurry collected and prepared from the Hua Lum Poo Canal (HLP), which was sporadically contaminated with hexachlorobenzene. In biostimulation experiments, HLP nutrient-strengthened sediment slurry was amended by yeast extract, mineral nutrients, acetate, lactate, and pyruvate, but no significant enhancement was found for 234-CBp dechlorination. It implied that the present substrates and nutrients at this site were sufficient to sustain the activity of 234-CBp dechlorination consortium. In bioaugmentation experiments, sediment slurry from HLP that possessed higher dechlorination potential was introduced to another five less effective sediment slurries for 234-CBp dechlorination tests. Results indicated a significant acceleration to those important slurries, and revealed a promising application for the in-situ remediation of PCB contamination in Thailand that might be expanded to worldwide application.