Urban Sewage Treatment Plants Running Simulation And Regulation In Low Temperature

In northern China, due to low temperature in winter, performance of biological urban sewage treatment plants becomes worse with sludge bulking, and effluent quality is often beyond the discharge standard. The treatment efficiency, sludge settle ability, sludge bulking, operation control, etc. –were investigated based on simulation run of domestic wastewater treatment plant at low temperature in lab. The change patterns of COD, TN, NH3-N, NO3--N, TP, and other regular testing indexes, and of sludge settle ability, and of physicochemical and biochemical characteristics of microbial community were studied, as temperature went down from 15 ℃ to 3 ℃. Relation of sludge bulking to temperature was also discussed. Hence relation of sewage treatment operation conditions to effluent quality was revealed. Thus ideas, suggestions and schemes could be offered to municipal sewage treatment plant in northern China in winter.In the process of simulated city sewage treatment plant running at low temperature, reaction process using the traditional activated sludge method. The sludge was bulked when temperature dropped to 9℃, in order to guarantee the normal operation of the reactor, taken to stop water, aeration, increase the sludge back flow and other measures.Results as follows can be found basing on the study of removal efficiency. COD removal efficiency was high, and COD in effluent had little change as temperature went down from 15 ℃ to 3 ℃, showing a strong resistance to impact. TN removal efficiency increased as a whole. Organic nitrogen removal efficiency has no significant change and maintained at a higher level while temperature decrease, the removal rate of NH3-N was comparatively high and may had maximum saturation value. A downward trend in effluent NO3--N and declined more swiftly in 9℃ and 3℃, TP in influent and effluent sewage had a similar change trend and the effect is not idealistic on removal.The sludge settle ability took a turn for the worse during the test running as temperature came down. And of the sludge bulking was type of filamentous bulking which is caused of high proportion of filamentous bacteria in microbes or EPS secreted massively. With measures adopted to adjust running mode to choke off sludge bulking can keep the operation in a steady way.The corresponding suggestions were put forward for municipal sewage treatment plant in winter of northern China according to the issues were found in simulation test.