Study On The Effect Of Extracellular Polymeric Substances On MFC Electricity Generation And Pollutants Removal

Membrane fouling is one of the key factors restricting the application of membrane bioreactors.Extracellular polymeric substances（EPS）is the main component of membrane foulant.It contains abundant organic matter and has great potential as external carbon source.Microbial fuel cell（MFC）can generate bioelectricity while treating wastewater.EPS is difficult to be biodegraded and can not be directly used as carbon source for MFC.In this study,EPS was used as the substrate for MFC,different hydrolysis methods and hydraulic retention time（HRT）were selected to optimize the operation condition.On this basis,the influence of different EPS dosage on the power generation performance and pollutant removal efficiency was further investigated.The main results of this study were as follows:（1）Three parallel systems with different hydrolysis methods,namely anaerobic hydrolysis,MFC anode and microbial electrolysis cell（MEC）,were constructed,described as hydrolysis-MFC,dual-anode MFC and MEC-MFC.With open circuit as the control,the operation performance was investigated when the HRT in hydrolysis chamber was 3 d,2 d and 1 d,respectively.With the decrease of HRT,the average voltage of hydrolysis-MFC,dual-anode MFC and MEC-MFC increased,and the COD removal efficiency improved.When the HRT was 1 d,COD removal efficiency of these MFC systems were over 90%,At the same time,protein,polysaccharide and humic acid could also be well removed,and the effluent concentration was less than 2 mg/L,but there was no significant difference in the removal efficiency between MFC systems.It was found that dual-anode MFC had the highest electricity production（26 m V）and maximum power density（2.110 W/m³）.Carbon source could be better utilized in this system.The result of BOD₅/COD showed that the biodegradability of the mixed solution was improved after the hydrolysis chamber treatment of hydrolysis-MFC and MEC-MFC,while the biodegradability was almost unchanged after the treatment of dual-anode MFC.More biodegradable organic matter was used to generate electricity in the hydrolysis chamber of dual-anode MFC.（2）The study of EPS dosage showed that when the influent COD concentration increased from low concentration（about 450 mg/L）to medium concentration（about 800mg/L）and high concentration（about 1000 mg/L）,the output voltage of dual-anode MFC increased first and then decreased.The COD removal efficiency decreased from 95.03%to84.52%and 81.66%.The concentrations of protein,polysaccharide and humic acid in the effluent also increased with the increase of those in influent concentration.At different influent concentration,the removal efficiency of TN in dual-anode MFC was not well.At low and medium influent concentration,the main component of TN in effluent was nitrate nitrogen,while at high concentration,it was organic nitrogen.The BOD₅/COD result showed that,compared with the anode area,the hydrolysis chamber of dual-anode MFC was more favorable to using biodegradable organic matter to generate electricity,thus the output voltage of the hydrolysis chamber was higher.（3）The result of high-throughput test of MFC anode biofilm under different hydrolysis methods showed that Proteobacteria,Bacteroidetes and Firmicutes were the main exoelectrogen in the anode biofilm of MFCs,and the effect of current could promote the enrichment of specific exoelectrogen.Further analysis of the horizontal structure of the genus found that Pseudomonas and Acinetobacter were the main bacterial genus for EPS degradation and electricity generation in MFC.The increase of the relative abundance of Acinetobacter and Desulfovibrio could enhance the power generation of the dual-anode MFC.