Enhanced anaerobic biodegradation of PCBs in contaminated sediments using periodic amendment of iron.

摘要

Anaerobic biodegradation of PCBs in contaminated sediments was examined using periodic amendment of iron to sediment for enhancing the microbial reductive dechlorination by indigenous anaerobic microorganisms present in the sediment. Hydrogen was supplied as the electron donor through anaerobic corrosion of elemental iron. The effect of continuous supply of hydrogen on the rate and extent of PCB biodegradation and the microbial community was investigated.;In this study, the biodegradation of 15 PCB congeners in three different contaminated marine and freshwater sediments was investigated over a period of 18 months using microcosm studies to determine the effect of initial iron dosage (with no iron recharge) and periodic amendments of iron (3 month and 6 month recharges) using the following iron dosages: 0, 0.01, 0.03 and 0.1g iron per g dry sediment. After 18 months, the greatest enhancement was achieved for the biodegradation of PCB congeners in the system using 0.01g iron per g dry sediment with 6 month recharge where the extent of biodegradation of most PCB congeners was significantly greater than that of the blank system (without iron) and the systems with larger dosages of iron. The biodegradation data revealed a greater than two-fold increase in the rate of PCB biodegradation with the periodic addition of 0.01g iron per g dry sediment (6 month recharge system) versus the blank system (without iron).;Phospholipid fatty acid analysis of the microbial community present in the sediments revealed the enrichment of Dehalococcoides species and lower microbial stress levels when the system was periodically amended with low dosages of iron thus lessening the competition from other hydrogen utilizing microorganisms like methanogens, iron reducers and sulfate reducers.;This research shows that, under ambient conditions, greater PCB degradation can be achieved at an accelerated rate ex situ by continuously supplying low levels of hydrogen to the indigenous dehalorespiring microbial community in the sediment. Therefore periodic amendment of low dosages of iron has the potential to be developed as an effective bioremediation technique to degrade PCBs in contaminated sediments.