Microbial Dechlorination of Hexachlorobenzene by Untamed Sediment Microorganisms in Taiwan

Abstract

To test the inherent hexachlorobenzene (HCB) dechlorination ability of indigenous consortia in Taiwan, microbes from four non-HCB-contaminated river sediments were collected and directly introduced to dechlorination experiments without any acclimation and enrichment. In natural sediment-extracted waters, when amended with 5 g/L of yeast extract, all four sets of sediment microorganisms initiated HCB dechlorination after 60 days. Without yeast extract, there were only two sets of microbes-dechlorinated HCB during a 150-day incubation period. On the other hand, in the artificial synthetic media amended with 5 g/L of yeast extract, all microbes from four sediments showed HCB-dechlorinating activity after 45–60 days of lag phases and completed dechlorination in latter 30 days. In all HCB-dechlorinated sets, dechlorination was accompanied by significant methane generation and the drop of oxidation-reduction potential (ORP). The results indicated that there were HCB-dechlorinating consortia grouped by the indigenous microorganisms in the river sediments of Taiwan, even though these sediments had not been contaminated by HCB before. In addition, the dechlorination could occur when the environmental conditions were suitable for the dechlorinating consortia to be enriched, and then the ability for HCB decomposition was built up.