Enhanced Anaerobic Biodegradation of PCBs in Contaminated Sediments Using Periodic Amendments of Iron

摘要

Biodegradation of PCBs occurs via reductive dechlorination due to thepresence of indigenous anaerobic microorganisms in contaminated sediments. Reductivedechlorination of PCBs in contaminated sediments under naturally reductive conditionsoccurs slowly over a long period of time. The addition of elemental iron results in anaerobiccorrosion of iron in water thus generating hydrogen gas (H_2) which may thenenhance the microbial reductive dechlorination of PCBs in sediments. In this study, theenhanced anaerobic degradation of PCBs in field-contaminated sediments has beenevaluated using periodic amendments of iron.The biodegradation of PCBs in sediment was carried out in microcosm studies forlake sediments using several sets of biodegradation experiments to determine the effect ofinitial iron amendment (with no iron recharge) and periodic iron amendments (with threemonthand six-month iron recharge periods) on PCB biodegradation in sediment usingthe following iron dosages: 0, 0.01, 0.03 and 0.1g/g [g iron per g dry sediment]. Theconcentration of PCBs in sediments was monitored with time for PCB congeners 18, 31,44, 52, 87, 101, 138, 153, 170 and 180, and for Aroclors 1221, 1232, 1242, 1248, 1254and 1260. After eighteen months, greater biodegradation of PCBs in sediment occurredfor the system with 6-month periodic amendments of iron using 0.01 g/g recharge of ironwhere nearly a two-fold increase in dechlorination (based on chloride production) wasobserved versus the system with no iron amendment (blank).