| As the rapid development of economic society and the quickening of the process of industrialization,chemical wastewater,brewery wastewater, domestic sewage and livestock wastewater are discharged of large amount, in recent years,with all kinds of wastewater and sewage treatment process technology for development by leaps and bounds, and sewage is an important part of water reuse, so the processing of sewage is particularly important. Sewage water contains large number of nitrogen and phosphorus, and the nitrogen and phosphorus do great harm to the environment. The eutrophication stimulates the plants and algae in the excessive growth of surface water, consumes oxygen in water, cause severe environmental pollution and ecological destruction.It not only causes the economic loss,but also does harm to people’s health.Since the1980s, with the process of China’s urbanization, oxidation ditch process with advantages of simple process,running stability, flexible operation mode, management convenience, low treatment cost that becomes the first choice of sewage treatment plant process in small and medium-sized cities in recent years. Properly speaking, the oxidation ditch does not belong to special biological nitrogen phosphorus removal process,but in recent years the appear of Carrousel oxidation ditch, Orbal oxidation ditch, integrated oxidation ditch and their improved technology that set up the appropriate for oxygen anaerobic period, anaerobic period,oxygen period to get good nitrogen and phosphorus removal results.CASS(Cyclic Activated Sludge System) is a kind of improved type of sequencing batch reactor, has the obvious function of nitrogen and phosphorus removal results, and is suitable for requirement of nitrogen and phosphorus removal of the urban sewage and some industrial wastewater treatment. It has advantages of stable treatment effect, seldom causing sludge inflation, process simple, less premise, s low cost investment and operation, resistance of impact load and good nitrogen and phosphorus removal results. It has been more and more applied, with broad development prospects in recent years in China. With the rapid development of China’s environmental protection industry and the deepening of the scientific research, CASS processes to its own unique advantages in theory and production application that will be realized in the big breakthrough.In order to promote oxidation ditch and CASS technical research development, especially in the processing of the application of the urban sewage, this topic uses the practical production process for the testing site in Xingsha,Changsha. It has a comprehensive study of the first-stage oxidation ditch process and a secondary CASS process work performance and has a test to oxidation ditch and CASS process. It focuses on operation conditions on the two process of the nitrogen and phosphorus removal effect and provides direct design basis for application process.On the basis of the existing research, this paper discusses the oxidation ditch process and CASS technology of the urban sewage treatment effect. The test is taken under the same conditions of water inlet and different process of the treatment effect for nitrogen and phosphorus. The results show that under the conditions of water inlet, the concentration of COD,SS,NH3-N,TN,TP are respectively684mg/L,303mg/L,24.5mg/L,32.6mg/L,10.7mg/L The removal rate of COD,SS,NH3-N,TN,TP are respectively96.9%,98%,88.4%,81%,68.3%for oxidation ditch and the removal rate of COD,SS,NH3-N,TN,TP are respectively96.6%,96.8%,84.4%,68.1%,76.3%for the CASS process.The effluent concentration of COD,SS,NH3-N,TN satisfy the level one emission standards of Comprehensive Sewage Discharge Standard (GB18918-2002). The two stage processes are not very ideal to remove the TP. According to this instance, This paper mainly discusses the influencing factors of phosphorus removal, and puts forward the feasibility reports in order to improve the effect of phosphorus removal and improve process operation. |
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