Removal of benzo[a]pyrene from soil in a novel permeable electroactive well system: Optimal integration of filtration, adsorption and bioelectrochemical degradation

A novel closed-circuit permeable electroactive well (CPEW) was constructed to remove benzo[a]pyrene (BaP) from soil. BaP was removed sequentially through interception, adsorption and further biodegradation on a graphite felt, which acted as a filtration layer and also a bioanode. The removal efficiency of absolute BaP amount in CPEW was 52.52 +/- 4.23%, higher than 44.94 +/- 2.69% in the control (open-circuit PEW, OPEW). Physical adsorption and biodegradation accounted for 66.31 +/- 4.15% and 33.51 +/- 1.58% of BaP removed from soil in CPEW, and 86.26 +/- 5.21% and 13.57 +/- 1.29% in OPEW at 50 d. Bioelectrochemical process greatly enhanced the biodegradation efficiency of absolute BaP amount from 6.13 +/- 0.49% (OPEW) to 17.63 +/- 1.49% (CPEW). High abundances of Gammaproteobacteria and Clostridia on the anode of CPEW could significantly enhance electrons transfer and thus improve BaP biodegradation. Moreover, Vibrionaceae (belonged to class Gammaproteobacteria) possibly played an important role in electron transfer. Based on the function predication analysis, the bioelectrochemical process could enhance the BaP biodegradation through increasing metabolic rates instead of changing metabolic pathways. Conclusively, CPEW, efficiently integrating filtration, adsorption and bioelectrochemical degradation, is a promising easy-to-implement in situ remediation technology for soil, sediment or groundwater contaminated with refractory organics.