Phosphorus Removal Effect And Microbial Community Structure Analyses In The EBPR System

Enhanced biological phosphorus removal (EBPR) process is one of the mosteconomic and effective techniques and therefore widely applied in wastewaterbiological phosphorus removal. In this study, a lab-scale Sequencing batch reactor(SBR) was set up and operated to enhance biological phosphorus removal, theremoval efficiency and its microbial community structure were determined.In the start-up process, the anaerobic phosphorous release emerged on the12thday, After26days, the phosphorous removal efficiency raised to90%. Most of thephosphorous was released within30min of anaerobic stage and the phosphorous wasabsorbed within30min of aerobic stage. TOC was mainly removed at the anaerobicstage. After6weeks operation, the phosphorous and TOC removal efficiency reachedto97.8%and97.5%, respectively, the ratio of phosphorous content and the dry sludgereached to13.5%.The sludge has good settleability. MLSS remained at2600-3000mg/L,MLVSS/MLSS kept at about0.75，SVI varied at120-150mL/g，88%of the particles diameter ranged between the0.02-0.2mm. The abundant and mature microbe phasepromised removal effect.The Nile Blue staining was more specific than the Sudan black staining for thePHB. The DAPI staining and the Neisser new staining for the poly-P were proper thanother staining methods. PHB content reached198.3mg/g MLSS detected by GC.After digested by HClO4, the poly-P content of sludge was determined to be138.4mg/g MLSS.In situ hybridization process with PAOs probes was optimized. FISHdemonstrated that38.7%microbes in the sludge were Betaproteobacteria,13.9%microbes in the sludge were Rhodocyclus spp., and slight GAOs existed in the system.The change of community structure from the start-up to stable stage was illustrated byPCR-DGGE. Phylogenetic tree proved that microbe population belong toα-proteobacteria、β-proteobacteria、γ-proteobacteria、Rhodococcus sp.、Pseudomonassp. and Uncultured organism. 10PAOs strains were isolated from the stable EBPR system, and4strains(PAO-1, PAO-2, PAO-3, PAO-5) have higher phosphorous removal ability. Throughthe morphology observation, physiological and biochemical analysis, and molecularbiological identification, PAO-1, PAO-5were identified to be Shewanella, andPAO-2, PAO-3were Aeromonas.