Fouling Mechanisms And Its Controlling Methods Of Forward Osmosis Membrane In Osmotic Microbial Fuel Cell

The osmotic microbial fuel cell(OsMFC)applying forward osmosis(FO)membrane instead of the proton exchange membrane in the traditional microbial fuel cell(MFC).OsMFC can simultaneously achieve water reuse and bioelectricity recovery during wastewater treatment.In this case,it has attracted increasing interests.Compared with the MFC,the OsMFC has better electricity generation and effluent quality.However,due to the introduction of FO membrane,OsMFC remains some inevitable problems such as membrane fouling and reverse salt diffusion,which results in a lower water flux,shore operating time and low low electricity generation.These problems has retarded the development and application of OsMFC.Based on these facts,we focused on the fouling mechanisms of FO membrane and its controlling methods in the OsMFC.In this study,the operating performance and the electricity production performance of the OsMFC and the mechanism of FO membrane fouling were investigated.Based on the analyses of FO membrane fouling,the fouling controlling methods including silver nanoparticles(AgNPs)and the copper nanowires and activated carbon modified the thin film composite polyamide FO membrane(CuNW/AC-TFC)was proposed.The main results and conclusions were summarized as follows:(1)MFC were integrated with FO membrane to build the OsMFC process,and its performance and fouling mechanisms of FO membrane were investigated.The results indicated that the OsMFC had a well power generation performance including the max output voltage and power density of 400 mV and 3.45 W/m~3,respectively.In addition,the OsMFC had better removal of organic matters and total phosphorus(TP)with removal efficiency of99.8%and 98.6%,respectively.Although the OsMFC had better effluent water quality,the serious membrane fouling resulted in rapid decline of water flux.The results of membrane fouling analyses suggested that the bioflouling was responsible for the lower water flux of FO membrane.(2)Due to the inhibition of silver nanoparticle(AgNPs)on the growth of microorganisms,the TFC FO membranes were modified by AgNPs for alleviating the membrane fouling.The results showed that the OsMFC with the modified FO membrane by AgNPs had a better power generation(3.67 W/m~3)compared with a traditional OsMFC,and also had the similarly better removal for organic matters and TP.Moreover,owing to the enhanced salt rejection of the modified FO membrane,it had a better removal for ammonia nitrogen.The water flux decline of the modified FO membrane decreased,indicating a mitigation of membrane fouling.It could be attributed to a better fouling resistance of modified FO membrane with better hydrophily and more negative charge,and the direct destroy to the microorganisms and proteins formed on membrane surface by AgNPs.(3)A new OsMFC system was developed by a conductive FO membrane as cathode electrode.The results revealed that the new OsMFC had a little worse power generation(1.74W/m~3)because the catalytic effect of activated carbon is inferior to platinum carbon,resulting in the deterioration of the conversion of organic matter to electricity.And the increased internal resistance of conductive FO membrane results in poor output power.In addition,the new OsMFC also had a better effluent water quality,and the removal efficiency of organic matters and TP was more than 94%.The reduction of FO water flux was less in the new OsMFC,suggesting the conductive FO membrane with better fouling resistance.Most of the foulants were located on the surface of the conductive FO membrane,which belongs to reversible fouling,while the residual foulants in the membrane pore were irreversible.