Development of a Microbial Consortium from a Contaminated Soil That Degrades Pentachlorophenol and Wood-Preserving Oil

Abstract

An indigenous microbial consortium capable of degrading pentachlorophenol (PCP) and petroleum hydrocarbons (C10-C50) was produced from a soil contaminated with wood-preserving oil. Two 10-L stainless steel soil slurry (10% w/v) bioreactors were operated in fed-batch mode. To verify the growth and efficiency of PCP degraders in the presence of other contaminants, one bioreactor was fed with a PCP-based wood-preserving mixture (WPM) and a second reactor was fed with technical-grade NaPCP. During the 90-day period of activation, PCP, C10-C50, Cl−, pH, and dissolved oxygen levels were monitored. The microbial community was monitored using specific most probably number (MPN) bacterial counts and mineralization tests. PCP degradation rates increased similarly in both reactors, from 19 to 132 mg/L-d in the NaPCP reactor, and from 41 to 112 mg/L-d in the WPM reactor. Contaminant loss calculations showed that 99.5% of PCP and 92.5% of C10-C50 added to the WPM reactor were biodegraded. It also revealed that 83% of polychlorinated dioxins and furans were removed. PCP-degrading bacteria increased from 7×102 to 1.6×106 bacteria/mL in both reactors, and petroleum hydrocarbon degraders increased from 1.7×102 to 3.4×108 bacteria/mL in the WPM reactor, indicating that the activity of PCP degraders was not inhibited by the presence of microorganisms growing on petroleum hydrocarbons.