The Research Of Characters Of Urban Sewage Treatment Plant Sludge In Northern China Winter And Operational Optimization

For cold regions in northern China, the treatment effect of municipal sewage treatment plant is poor when winter comes, and it is difficult for the effluent to meet the discharge standards. By simulating operation mode of traditional activated sludge process in actual engineering, extracellular polymeric substances(EPS), triphenylte trazolium chloride-dehydrogenase activity(TTC-DHA), oxygen uptake rate(OUR) of microorganism, microbial changes under microscopy were investigated in lab, as temperature went down from 15 ℃ to 3 ℃. The change patterns of sludge characteristics were revealed, thus effective optimal operation scheme could be put forward, facing operation problems of domestic wastewater treatment plant in winter of northern China.Simulation experiments revealed that, under cold condition, EPS in sludge decreased as temperature went down to 11℃. Sludge bulking causing by filamentous microorganism appeared at 9℃, meanwhile EPS increased. Although the EPS remained stabilized after the expansion, protein, a component of EPS, decreased as temperature dropped. As temperature dropped, Polysaccharide content decreased in ESP before sludge bulking appeared, but increased in ESP after sludge bulking, TTC-DHA declined as temperature went down, which had similar change pattern with OUR especially at 13℃. When temperature dropped to 11℃ and below, TTC-DHA and OUR changed slightly, which indicated that low temperature condition has little affect upon these factors. Microbial population varied as temperature kept dropping. The sludge became teeming with filamentous microorganism at 11℃, and filamentous microorganism was dominant at 9℃, while protists cut down with a low metabolic rate. Sludge bulking went on as temperature dropped from 9℃ to 3℃.An operational optimization plan is proposed to municipal sewage treatment plants according to the change patterns of sludge characteristics. Initially, OUR alerting device should be set up and the polysaccharide content in EPS should be monitored. Furthermore, operation load as well as aeration should be reduced appropriately. Finally, excess of aeration before sludge recycling would help improve sludge activity and control the negative impact caused by sludge bulking, therefore increase treatment performance.