Activation of an indigenous microbial consortium for bioaugmentation of soil contaminated with wood-preservation compounds

The concept of activated soil is based on the cultivation of selected biomass from a fraction of contaminated soil in bioreactors. A pentachlorophenol (PCP) based wood-preserving mixture (WPM) was used as substrate for soil activation in order to acclimate the microbial flora to several contaminants. Experiments were conducted in two 8 liter fed-batch 10%(w/v) slurry reactors, one being fed with technical grade PCP, the other with PCP based WPM. PCP, C-10-C-50, pH, microbial density activities and DNA were monitored during the 60 day activation period. The PCP analysis from reactor samples showed that maximal PCP degradation rates were similar in both reactors, going from 19 to 132 mg/L d in the soil activated with technical grade PCP, and from 22 to 98 mg/L d in the WPM activated soil. Mass balance indicates that 99.9% of PCP and 99.0% of C-10-C-50 added to the slurries were degraded. The bacterial counts showed that the concentration of PCP-degrading bacteria was not influenced by the presence of the other components in the WPM. The gene encoding PCP-4-monooxygenase (pcpB) was detected in both activated soils and amplification of 16S ribosomal genes by polymerase chain reaction and their analysis by single strand conformational polymorphism revealed that the biodiversity dropped dramatically during activation.