Performance Of A Novel MFC System Combined With Forward Osmosis For Water And Electricity Recovery From Municipal Wastewater

Integrating forward osmosis(FO)with microbial fuel cell(MFC)for simultaneous wastewater treatment,water extraction and bioelectricity generation has attracted increasingly attentions.However,most of the publications were focused on the internal FO-MFC combined system(named as OsMFC).Although the electricity generation in the OsMFC is better than the conventional MFC,the water flux level of FO membrane is much lower due to the internal concentration polarization(ICP),salinity build-up and membrane fouling.In addition,FO membrane fouling is still a great challenge to the internal configuration due to its difficultly in applying an in-situ membrane cleaning.Based on these facts,more studies are needed for better understanding the combination of MFC and FO.In this study,a novel combination of anaerobic acidification,FO and MFC(named as AAFO-MFC)was firstly proposed,and then the impacts of different FO membrane materials and conductivity conditions on AAFO-MFC system performance were investigated for selecting the optimal operating conditions.Lastly,the performance of the AAFO-MFC system was investigated under these optimal conditions for a long-term continuous operation,and the feasibility of using AAFO-MFC for achieving water reuse and bioelectricity recovery was evaluated.The main results and conclusions were summarized as follows:(1)A novel AAFO-MFC system was developed by integrating MFC with anaerobic acidification and FO membrane,and the effects of FO membrane materials on the performance of AAFO-MFC were investigated.The results indicated thatthe water quality of PES-FO membrane was better compared to the TFC-FO membrane,especially in terms of NH4+-N concentration.In addition,the TFC-FO membrane fouling tendency was severer than the PES-FO membrane due to its rougher membrane surface,which finally led to a severer flux decline of TFC-FO membrane.Based on these facts,PES-FO membrane was more suitable for the long-term operation of AAFO-MFC.(2)The conductivity conditions in the AAFO-MFC system were controlled at three levels of 4~5,7~8 and 9~10mS/cm by applying microfiltration(MF)membrane for solute discharge,and their impacts on the performance of AAFO-MFC were investigated.The results showed that conductivity had a significant influence on the FO membrane operation,MFC performance and sludge properties,while it had a slight effect on the removal of pollutants in the AAFO-MFC system.Based on these results,the optimal conductivity was in the range of 7~8 mS/cm for the AAFO-MFC system.(3)The AAFO-MFC was operated under the optimal conditions,and the feasibility of using AAFO-MFC for achieving water reuse and bioelectricity recovery was evaluated.The results revealed that the AAFO-MFC system obtained a continuous and relatively stable power generation with a maximum power density of 4.38 W/m3.The higher bio-electricity production in the AAFO-MFC system was mainly due to the accumulation of ethanol resulted from anaerobic acidification process and the rejection of FO membrane.In fact,the Desulfuromonas sp.utilized the ethanol for bio-electricity production was observed in the anode.In addition,the AAFO-MFC system produced a high quality effluent,with the removal rates of more than 97% for organic matters and total phosphorus.Furthermore,it could be found that the combined biofouling and inorganic fouling were responsible for the lower water flux of FO membrane.