Enhanced treatment of Fischer-Tropsch (F-T) wastewater using the up-flow anaerobic sludge blanket coupled with bioelectrochemical system: Effect of electric field

•The BES-UASB coupled system was established for enhanced F-T wastewater treatment.•The electric field added could promote granulation and conductivity of sludge.•The Geobacter and Methanosarcina enriched in the BES-UASB coupled system.•The promoting DIET mechanism highly depended on assistance of electric field.

The coupling of bioelectrochemical system (BES) with an up-flow anaerobic sludge blanket (UASB) was established for enhanced Fischer-Tropsch (F-T) wastewater treatment while the UASB (control group) was operated in parallel. The presence of electric field could offer system a more reductive micro-environment that lower the ORP values and maintain the appropriate pH range, resulting in the higher chemical oxygen demand (COD) removal efficiency and methane production for BES-UASB (86.8% and 2.31 ± 0.1 L/(L·d)) while those values in control group were 72.1% and 1.77 ± 0.08 L/(L·d). In addition, the coupled system could promote sludge granulation to perform a positive effect on maintaining stability of pollutants removal. The high-throughput 16S rRNA gene pyrosequencing in this study further confirmed that the promoting direct interspecies electron transfer (DIET) between Geobacter and Methanosarcina might be established in BES-UASB to improve the syntrophic degradation of propionate and butyrate, finally facilitated completely methane production.

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