Analysis Of The Performances Of Microbial Fuel Cell-membrane Bioreactor System

Membrane bioreactor (MBR) has many advantages over conventionalwastewater treatment processes. It is one of the most promising wastewatertreatment processes. However, membrane fouling is the most challenging issuefacing further MBR development. Nowadays, researches on membrane foulingcontrol mainly focus on: memgrane and membrane module, operation conditions,characteristics of influent and sludge. The researches on the latter have becomepopular. The process of Microbial Fuel Cell (MFC) can effectively degradeextracellular biological organic matter (EBOM) and recover electricity. TheMFC-treated sludge has a low extracellular polymeric substances level, and thecharacteristics of the sludge change, too. After recycling the sludge to the MBR,the characteristics of the sludge may be modified, and mitigate the membranefouling.In this study, a new process for combining MBR with MFCs was establishedto mitigate membrane fouling and recover electricity. The excess sludge of MBRwas treated by MFCs, and then recycled to MBR. The combined system wascompared with the conventional MBR and the anaerobic digestion sludgerecycling MBR with respect to the performances of wastewater treatment, themembrane fouling and the characteristics of mixed liquor.First, the performances of MFC treatment were analysed. During MFCoperation, the insoluble macromolecules in extracellular polymeric substancescould be hydrolyzed into soluble molecules. The supernatant quality includingpolysaccharides and proteins increased dramatically. After operation for5days,the removal rates of the dry sludge weight and TCOD were22.50%and15.86%,respectively. The maximum output voltage of the MFC was0.45V, and themaximum output power was72.02mW/m~2.The result showed that the effluent quality of the MFC-MBR system was notdeteriorated significantly, with removal efficiencies of94%and87.3%for CODand NH4+-N, respectively. There was no significant effect on the concentration ofP in the effluent. Although the sludge activity of MFC-MBR was decreased, itdarely had effects on the effluent quality.During the92days’ operation, membrane fouling of the MFC-MBR systemwas mitigated dramatically and the chemical cleaning cycle was prolonged by35%compared with the conventional MBR.The ratios of mixed liquor volatile suspended solids (MLVSS) to mixedliquor suspended solids (MLSS) for the three systems were almost identical, in the range0.88-0.92, indicating that the inorganics from the MFCs did notaccumulate as particulates in the MBR. Compared with the conventional MBR,The sludge yield of the MFC-MBR system was decreased by16%, indicating thatMFC-MBR system had an effect on sludge reduction.Compared with conventional MBR, the recycling of MFC-treated sludge hadmodified the sludge characteristics of MBR. The smaller dissolved SVI ofMFC-MBR (100mL/gMLSS) indicated that the settleability was increased.Specific resistance to filtration and normalized capillary suction time of theMFC-MBR decreased by50%, demonstrating that the dewaterability wasimproved dramastically. The viscosity of the sludge in MFC-MBR system(2.2s·L/gMLSS) had been controlled effectively. In the MFC-MBR, thepercentage of the particles smaller than50μm was ruduced, and it has a morenarrow size distribution. The hydrophobicity of the sludge in MFC-MBR systemhad been reduced. The sludge of MFC-MBR had become more regular. Therefore,the modification of the sludge characteristics and other factors could mitigate themembrane fouling dramastically.Above all, the MFC-MBR system has good performances, allowingwastewater and sludge treatment at the same time, easing the subsequent disposalof the excess sludge. It’s application in practices has great potential to develop.