Study On Treatment Of Oily Wastewater By MFC-EC Combined Technology

Microbial fuel cells(MFCs)and traditional electrocoagulation(EC)were coupled to build a bio-electrocoagulation system(MFC-EC)for oily wastewater treatment without additional power supply.The system removes most of the oil,organic matter and particulate pollutants in the wastewater through EC,and the effluent goes into MFC for further degradation with generating electricity used in situ to maintain the operation of EC.The coupled system takes advantage of each technique and avoids the limitation of a single technology,having important academic value and application potential.The MFCs were acclimated by anaerobic activated sludge,with the maximum power density of 613.6±10 mW/m~2 when stable.Four MFCs with similar performance were selected to power EC,and the conditions were optimized by orthogonal experiment.The results showed that the best condition for oily wastewater treatment by EC was that when the electrode distance was 1 cm,electrode area was 24 cm~2 and the stirring speed was 360 r/min.Stacked MFC filled with EC effluent was used to power EC for oily wastewater treatment,comparing with the DC power supply.The results showed that the voltage,current and wastewater treatment performance were comparable between four MFCs linked in series and DC power supply,which were both better than four MFCs linked in parallel,indicating that the stacked MFC linked in series can be used to power EC effectively.The total removal efficiencies of COD,oil and turbidity were 72.0±1.0%,64.5±1.5%and 85.5±1.0%,respectively,when oil wastewater was treated by the two-stage MFC-EC combined system.The results were further verified by the FEEM and FT-ICR MS that the MFC-EC combined system was effective on the removal of organic matter in the wastewater.Analysis of microbial community on the MFC anode showed that the dominant genera were mainly Bellilinea,Thauera and Aminivibrio when using sodium acetate as substrate;when switching to oily wastewater as the substrate,the dominant genera were exoelectrogens(such as Exiguobacterium,Aminivibrio,Petrimonas,etc.)and petroleum-degrading bacteria(such as Acidovorax,Rhizobium,Sphingopyxis,etc.).It is suggested that petroleum-degrading bacteria in the oily wastewater was enriched on the MFC anode,and synergized with exoelectrogens for degradation of oily pollutants and electricity generation.