Biostimulation and Bioaugmentation of Anaerobic Pentachlorophenol Degradation in Contaminated Soils

The effects of bioaugmentation with a pentachlorophenol (PCP)-adapted consortium and biostimulation with glucose as a carbon source on anaerobic bioremediation of PCP-contaminated soil were investigated in terms of the initial PCP removal rate and the extent of PCP dechlorination and mineralization. Samples from two PCP-contaminated sites were prepared, put into a series of Hungate tubes, inoculated, and fed under different conditions. Chlorophenols in the tubes were monitored over a 4-month period to measure PCP transformation in the soil. In less contaminated soil (10 mg PCP/kg soil), it was found that biostimulation with glucose at 1 g/kg soil or bioaugmentation at 0.14 g volatile suspended solids (VSS)/kg soil could greatly improve PCP degradation. The best PCP degradation was obtained when both bioaugmentation and biostimulation were applied, but higher levels of glucose (2 g/kg soil) or inoculum (0.56 g VSS/kg soil) had little additional effect. The highest initial PCP-removal rate reached 8.1 μmol/kg soil-d, which is almost 20 times greater than in the unamended controls. PCP was dechlorinated to lesser chlorinated phenols with 0.6 chlorine remaining on average, and the extent of mineralization approached 70% in 4 months. In highly PCP-contaminated soil (90 mg PCP/kg soil), PCP degradation was partially inhibited, but the relative effects of augmentation, stimulation, and combined treatments were the same as in the less contaminated soil.