DO Research On A~2O System Nitrogen And Phosphorus Removal And Microbial Community Structure Affect

Population growth and economic development increased human demand for water and quality requirements, leading to increasingly serious water pollution, has become one of the important factors hindering the development of the global economy. Water eutrophication phenomena deteriorate water quality, in serious condition, cause the water black and smelly. An important element cause eutrophication phenomenon is nitrogen and phosphorus, and their removal has been the focus of water treatment experimental study. Research system operating parameters and microbial community structure, can provide strong theoretical basis for its optimization process.People change the concentration of dissolved oxygen in the aerobic reactor system of A-A-O process, make the average concentration of dissolved oxygen is4.5mg/L、3.5mg/L、2.5mg/L、1.5mg/L,0.5mg/L. By analyzing influent and effluent water quality and DNA molecular markers,Study the changes in the concentration of dissolved oxygen to denitrification and phosphorus removal and microbial community structure of the A-A-O sewage treatment system.In this study, the methodology used in the A-A-0process activated sludge microbial community structure is identification denaturing gradient gel electrophoresis (PCR-DGGE) The advantage of this method:mutation detection rate, a small amount of sample, non-isotopicsimple, fast, and can detect multiple microorganisms.Investigated dissolved oxygen concentration on the influence of the denitrification function and nitrobacteria community, The results show that:nitrosation and nitration function of A-A-O system and the dissolved oxygen concentration is proportional to the dissolved oxygen, concentration greater than or equal to2.5mg/L, NH4+-N removal rate of more than85%. The dissolved oxygen concentration decreased affect nitrification functional bacteria community structure and Shannon diversity index, with decreasing concentration of dissolved oxygen, AOB Shannon diversity index decreased, but the decline is not obvious. When the dissolved oxygen concentration greater than or equal to2.5mg/L,, the Nitrospira species in the activated sludge is rich, but with the reduction of dissolved oxygen concentration, Shannon diversity index gradually decreases. When the dissolved oxygen concentration below2.5mg/L, Nitrospira accounted NOB dominant position.Investigated the A-A-0process Phosphorus Removal and denitrification and phosphorus removal bacterial community structure in the test, the results showed that: the removal rate of phosphorus decreased and the removal rate is about40%. AAO process to maintain a high rate of nitrogen and phosphorus removal, the dissolved oxygen in the aerobic reaction zone average concentration should be in the1.5mg/L or more. With the lowering of dissolved oxygen concentration of the aerobic reaction stage, activated sludge SVI is worse;filamentous bacteria in activated sludge occurs micro-expansion when the dissolved oxygen concentration is low, the effluent water is clear. Changes in the concentration of dissolved oxygen affect the DPB community structure and Shannon diversity index. DPB flora Shannon diversity index was significantly reduced in the process of the reduction of the concentration of dissolved oxygen. Reduction of dissolved oxygen concentration affect the metabolic activity of the DPB flora, to some extent, Affect phosphorus removal process.when the concentration of dissolved oxygen in the activated sludge is greater than1.5mg/L, DPB species is rich, phosphate removal in more than90%.With the reduction of dissolved oxygen concentration, the Shannon diversity index gradually reduced,shows:low dissolved oxygen concentrations significantly inhibited the DPB flora.Comprehensive consideration, A-A-O process to maintain a high rate of nitrogen and phosphorus removal, the DO in the aerobic reaction zone should be at1.5mg/L or more.