Effect Of Electrochemical Regulation On The Community Composition And Metabolism Of Anode Biofilms

The microbial electrochemical systems（MESs）demonstrate advantages as a novel biological wastewater treatment technology for enhanced organic contaminants removal while generating electricity.However,the substrate mechanism of anode biofilm under electrochemical regulation is still unclear.Further improvement of microbial degradation rate is also important.In order to construct a high-efficient regulation mechanism,it is essential to reveal the metabolic response and community composition characteristics of the anode biofilm under electrochemical regulation.Based on the three-electrode systems,the characters of anode biofilm with persistent exogenous bacteria interference were analyzed.The chemical oxygen demand（COD）degradation were simulated with first-order（background COD remove）and zero-order reaction（anode-respiring COD remove）to explore the influence of electrochemical factors on mature biofilms.Statistically,background COD degradation rate（k_b）generally exhibited a positive linear correlation（R²=0.7822）with current,accelerated by increased current.The increment of background COD degradation related with increasing current（ΔCOD_b-Cur.）accounted for a relatively stable proportion of 33%in overall COD increment.The start-up potential affected the metabolism and composition of system biofilm.The higher COD removal(>1500 mg L^–1)was obtained with higher k_bduring 0-3 h at-0.1 V(0.230 h^–1)and 0 V(0.241 h^–1).With glucose as substrate,high potentials（above-0.1 V）formed thicker biofilms than low potentials（-0.2 V and open circuit potential）,leading to stratification and functional differentiation.The inner layer enriched anode-respiring bacteria（ARB）,while the outer layer enriched fermentation bacteria and separated exogenous bacteria as a transition layer,degradating substrate progressively.Constant potiential promoted the enrichment of ARB.The Pseudomonas（2.52%）and Acinetobacter（6.52%）were key bacteria in sodium acetate cultured anode biofilms,while Lactococcus（26.27%）dominated in glucose cultured biofilms.COD loading regulated interspecific relationship.The ARB and non-ARB successively exhibited competition(100-500 mg L^–1)and synergy(500-1500 mg L^–1)with increasing COD concentration,before being restricted by excessive COD loading(above 1500 mg L^–1).