Stimulation of phenanthrene and biphenyl degradation by biochar-conducted long distance electron transfer in soil bioelectrochemical systems.

Abstract The bioelectrochemical degradation of organic pollutants has attracted considerable attention owing to its remarkable sustainability and low cost. However, the application of bioelectrochemical system (BES) for the degradation of pollutants in soils is hindered by limitations in the effective distance in the soil matrix. In this study, a biochar-amended BES was constructed to evaluate the degradation of organic pollutants. This system was expected to extend the electron transfer distance via conductive biochar in soils. The results showed that biochar pyrolyzed at 900 °C facilitated the degradation of phenanthrene (PHE) and biphenyl (BP) in the soil BES (SBES), reaching 86.4%–95.1% and 88.8%–95.3% in 27 days, respectively. The effective distance of SBESs was estimated to be 154–271 cm away from the electrode, which increased 1.9–3 fold after the addition of biochar. Microbial community and functional gene analysis confirmed that biochar enriched functional degrading bacteria. These findings demonstrate that the promotion of long-distance electron transfer and the formation of soil conductive networks can be achieved by biochar amendment. Thus, this study provides a basis for the effective degradation of for persistent organic pollutants in petroleum-contaminated soils using bioelectrochemical strategy.