Study On Soft Control System Of Wastewater Disposal Plant Based Statistical Technique

City Living Sewage is one of the main water pollution resources of China. After reforming to commercial running, municipal sewage plant faces problems of uncontrolled quantity of input wastewater, operation revenue linked with disposal quality, higher standards, and stricter management objectives. Besides improving techniques, equipments and processing control system, it is also necessary for operators to improve management method when maintaining high process quality. Applying SPC(Statistical Process Control) in the environment of wastewater disposal process could provide an effective assist control to operators.The first part of this thesis described current situation of wastewater treatment in China and the current researches around it. Demand of wastewater treatment is increasing and reformation of plant has been taken for several years. It is highly required to improve treatment's management quality. Currently, most of researches in wastewater treatment are about modeling and simulation of simplified biochemical reaction, reliability of treatment equipments, reliability of network, operation cost model, etc.The second part discussed theories of SPC, Control Charts and their traits. Then the current researches about application of SPC were reviewed such as combination of SPC and EPC(Engineering Process Control), statistical process monitoring and evaluation in health care system, supply chain system and business services. Lastly, by comparing with other control theories and tools, traits of SPC and the applicability of control chart in wastewater treatment process were discussed. The third part firstly analyzed factors in the treatment environment which would influence the treatment quality, then defined "soft control" in wastewater treating process and established index system of wastewater treatment soft control system. Lastly, we designed the soft control system of wastewater treatment, giving the computation methods and running processes and preliminary analysis of possible outputs(control charts and out-of-control variables test results).To test efficiency of the system, the fourth part investigated Anhui Shucheng Wastewater Treatment Plant. By quality management software Minitab, we analyzed the production data provided by the operator and got the in-control samples and control limits of every factor. Based on these, we examined the data of first half year in 2009 and concluded that the time for equipment maintenance and fall-back state was long, output water without treatment and concentration of noxious gas( H 2S ) were many and high enough to be out of control. Some advices and plans for control were given after these conclusions.The results of applying the system proved that it can effectively test whether the factors of treatment process are out of control and also proved that the wastewater treatment soft control system could effectively provide assist control to wastewater treatment plant managers.