| In recent years, with the rapid growth of GDP and the improvement of people’s living standard, the water consumption of our country has increased rapidly, which leads to the rapid increase of China’s sewage discharge and the problem of water eutrophication. Urban sewage treatment has become an urgent problem to be solved by the government. How to effectively deal with urban sewage is a hot and difficult point in the study. In this context, China’s sewage treatment plant has developed rapidly in order to protect the environment better and the rational use of water resources.However, there are various kinds of problems, such as carbon source, sludge age, operation management level in the traditional sewage treatment process. And because the biological wastewater treatment systems are often faced with severe external disturbance factor, and the relationship between the microbial flora and biochemical reactions that occur in the system, the system operating parameters and the final deal with the effects are very complex, relying on experience and judgment artificial operation, which is difficult to solve the contradiction between them what happened and the sewage treatment plant operating costs to make its use. Therefore, it has a great significance to the development of China’s sewage treatment plant at this stage and how to improve the operating performance of the existing sewage treatment plant, reduce operating costs, making it stable, efficient, economic operation.In order to deal with the requirement of multi-variable treatment of domestic sewage and according to the characteristics of the microorganism, this study carried on the upgrading and improvement to the existing sewage biological treatment system,and constructed a pilot plant of two-stage anaerobic, two-stage aerobic,four- stage aerobic biological treatment of domestic sewage,which was implementated with process control and the Internet technology was applied to the sewage treatment system to solve the sewage treatment process of various contradictions and problems. According to the characteristics of A~2/A~2/O~4 system, the removal efficiency of NH4+-N, TN, TP and COD in wastewater was analyzed in detail. The average removal rate was 85.46%, 75.13%, 91.24% and 86.27%, and the removal efficiency was better. And discusses the various forms of nitrogen and COD along changes in each pond, informed of COD removal was 23.13% in the anaerobic tank, COD removal was 27.46% in the anoxic tank, COD removal was 20.55% in the aerobic tank, other ways(such as secondary sedimentation tank of COD removal and COD in the sludge adsorption) removal of 14.32%.The effects of DO concentration, p H, ORP, the reflux ratio of the mixture, the change of the sludge reflux ratio on the indexes of all kinds of pollutants in the A~2/A~2/O~4 system were explored. According to the characteristics of A~2/A~2/O~4 system, the control objective, control parameters and control variables were determined, and the control parameters were p H, ORP, DO, and the control variables were mixed liquid flow rate, sludge return flow rate and aeration rate. The dissolved oxygen(DO), p H and oxidation-reduction potential(ORP) were obtained by DO、p H and ORP sensors online at each stage, which were used to regulate the sludge recycle flow rate, supernatant flow rate and aeration rate at each stage to achieve the process control of DO, MLSS and ORP at each stage and create the regulation of biological environment. Then to realize the regulation process of the organic pollutants(COD) and nitrogen removal at each stage.The feasibility of controllable parameters as the control parameters of the system is discussed, as well as the theoretical basis of the controllable variables as the control variables of the system and the corresponding control strategies are also discussed. Finally, the relevant rate equation was fitted which was based on a large number of experimental data in order to better understand the degradation process of all kinds of pollutants in A~2/A~2/O~4 system, to facilitate the establishment of process control model and improve the efficiency of the operation. |
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