Study Of Sidestream Oxic-settling-anaerobic Process For Excess Sludge Reduction

At present, activated sludge process is widely used in biological wastewater treatment in the world. But there is a serious problem that the technology will produce plenty of excess sludge to handle. So it is very significant that reducing the amount of the excess sludge in the process of waste water treatment will reduce the secondary pollution and lighten the burden of the sequential treatment and disposal. Based on different sludge reduction technology researching in both domestic and overseas, a brand new sludge reduction reactor-side stream OSA process that is modified from conventional OSA process has been proposed. In this paper, the performance of treating wastewater and influence factor in side stream Oxic-Settling- Anaerobic process has been studied.In this paper, the Yobs caused by sludge concentration(MLSS),sludge retention time(T)and ratio of side stream return flow sludge (n) were studied by single-factor method at first. It shows that the improvement of MLSS, T and n can result in the decline of Yobs. It also shows that the improvement of MLSS, T can result in the decline of ORP. By the orthogonal method, it shows the sludge production yield has a linear relationship with MLSS, T and n: Yobs=-0.011MLSS-0.002T-0.001n +0.302. It also shows the sludge concentration is most considerable factor; the ratio of side stream return flow sludge is least.The reduction sludge of side stream OSA process has been studied. Comparing by CAS process and OSA process, the sludge production of side stream OSA process reduces by 42%, 6% respectively. Comparing by OSA process, the quantity of sludge reduction per litre rises 60%. The efficiency of sludge reduction improved significantly. It supplies a way to reduce the cost of sludge reduction by diminishing the volume of anaerobic tank.As the reduction of sludge, the effect of wastewater treatment has been stabilized. It shows the effect of side stream OSA process is equivalent with OSA process. Comparing by OSA process, the removal ratio of COD and SS has been improved. Comparing by CAS process, the removal ratio of TN and TP has been increased 40.56%,34.61% respectively. The study suggested that the sludge settling performance and activity is equivalent with OSA process, better than CAS process.