Study On Enhancing The Biological Denitrification Effect Of Low Temperature Domestic Sewage By PVA Gel Ball Filler

Because the winter temperatures in northern China are relatively low,biological nitrogen removal from domestic sewage is difficult to guarantee.removal method was proposed.The cyclic activated sludge biological treatment process(CASS)has become the most commonly used sewage treatment process in the northern region because of its advantages of small area,simple operation,good performance of activated sludge,and good effect of microorganism removal of organic matter.However,all of its processing is concentrated in a single CASS reactor,resulting in a single activated sludge in the reactor.The ability to handle organic matter(COD,ammonia nitrogen,and total phosphorus)is limited,especially for removal of ammonia nitrogen in low temperature.Therefore,there is a high requirement for effective removal of nitrogen from CASS in low temperature.Polyvinyl alcohol(PVA)is a polymer material widely used in the textile industry.In this study,PVA gel beads were prepared by gel method and used as filler in CASS reactor.This filler not only had the characteristics of general hydrogels,but also had strong mechanical properties,low toxicity,and a density close to that of water.There are more pores inside,which is favorable for the growth of bacteria including denitrifying bacteria.In low temperature,PVA gel balls can increase the concentration of denitrifying bacteria,at the same time can avoid the expansion of sludge,thus effectively overcome the problem of denitrification effect caused by declining metabolism of denitrifying bacteria.First,the PVA gel balls were prepared.From the experimental data analysis,the mass ratio of PVA to boric acid was 10:0.1,and the heating temperature was 80°C.The water absorption capacity of the that has been prepared was 62 g/g,a density was 1.02 g/cm~3,and a tensile strength was 47 MPa,and PVA gel ball filler has the best properties.Second,the PVA gel balls filler had been prepared were added into the CASS reactor and the CASS reactor was started.After the sludge matured,CASS System with PVA Gel Balls were optimized and the removal efficiency of ammonia nitrogen was studied.The optimum operation in CASS actor added PVA gel balls as follows:temperature was(6-15°C),continuous water intake,aeration was 2h,precipitation was1h,influent amount was 5L,reflux ratio was 300%,other conditions was suitable.Last,compared the processing capacity of tradition CASS reactor with the processing capacity of CASS reactor wich was added PVA gel balls,especially the removal of ammonia nitrogen rate.The experimental results show that with the added of PVA gel ball filler the CASS reactor had a good denitrification effect,the removal rate of ammonia nitrogen was about 74%,and the denitrification efficiency of traditional CASS was about 64%.However,the denitrification efficiency of conventional CASS was about 64%,which indicated that the PVA gel ball filler can enhance the CASS ammonia nitrogen removal effect by at least 10%.This method is a new way to solve the biological denitrification effect of domestic sewage in low temperature of northern China and find a new research for the development of CASS.