Compost Science and Utilization, 9(4):274-283 (2001) BIOREMEDIATION OF A PCB-CONTAMINATED SOIL VIA COMPOSTING

Polychlorinated biphenyls (PCBs) were widely used in the past and now contaminate many industrial and natural areas. In this study, a PCB-contaminated soil from a former paper mill was mixed with a yard trimmings amendment and composted in field scale piles to determine the effect of soil to amendment ratio on PCB degradation. Temperature, oxygen concentrations, and a number of other environmental parameters that influence microbial activity during composting were monitored. The PCBs in contaminated soil had a concentration of 16 +1 mg/kg dw and an average of 4 chlorines per biphenyl. The soil was composted with five levels of yard trimmings amendment (14 % to 82 % by weight) in pilot scale compost piles (25 m3) turned once per month. Results showed up to a 40 % loss of PCBs with amendment levels of 60 % and 82%. Congener specific PCB analysis indicated that less chlorinated PCB congeners (1-3 chlorines per biphenyl) were preferentially degraded. Bench-scale studies indicated that less than 1 % of the PCBs in the contaminated soil were volatilized from composts during incubation with forced aeration at 55 ° C. In conclusion, PCB loss observed during the composting of the PCB-contaminated soil appeared to be largely due to biodegradation and not volatilization. Effective bioremediation of aged PCB-contaminated soils may require coupling of composting with additional remediation technologies to reduce levels of PCB congeners with greater than 4 chlorines