Degradation and utilization of EPS from excessive activated sludge by interaction of electrogenesis and light stimulation

Sticky and gel-like extracellular polymeric substances (EPS) could provide the protective shielding and prevent the microbial cellrupture and lysis as well as increase the difficulty of excessive activated sludge (EAS) biodegradation. Microbial fuel cells (MFCs) are able to accelerate the degradation of EPS and gain electric energy recovery from wastewater simultaneously. In order to discover the role of light stimulation on MFC performance, four reactors were operated in dark (SD), in LED light (SL), in electrogenesis (ED) and in combination of electrogenesis and light (EL), respectively. EPS characteristic, electrochemical performance and anodic microbial community structures were investigated and compared. The results showed that single light stimulation distinctly improved the total EPS especially polysaccharides content in soluble EPS, and Pseudomonas (31.85% relative abundance) as well as Acinetobacter (10.2% relative abundance) became the dominant genera. Single electrogenesis mainly promoted degradation of negatively charged proteins, which was further proved by the enrichment of typical proteolytic and amino acids fermented bacterial genera like Proteiniphilum and Cloacibacillus. Furthermore, the electrochemical activated Petrimonas and syntrophic Syntrophomonas occupied the dominant position indicating the existence of interspecific electron transfer. Moreover, the predominance of Acinetobacter (44.2% relative abundance) and Escherichia/shigella (7.09% relative abundance) in EL reactor implied the synergetic improvement of electrogenesis and light stimulation. In the interaction effect, light stimulation optimized the electricity generation and proteins degradation of MFC.