Automatic Control System Of CAST Process For Wastewater Treatment

According to the shortage of freshwater both with the enhancement of environment protection, the importance of wastewater treatment is becoming more and more obvious. Now, the Activated Sludge Process, a kind of wastewater treatment with complicated mechanism, non-linear and varying, has been extensively utilized in the industrial and municipal wastewater treatment. In order to improve the running result, we should first know about the mechanism , and then upbuild the advanced real time auto-control system in wastewater treatment plant.The tradition control way can't be applied in the process due to the lack of the accurate math model of the process and the sensors which can reflect process parameters directly. The paper applies the fuzzy control which is one of intelligence control methods to CAST process of wastewater treatment to improve the efficiency, decrease the consume of energy and avoid sludge expanding.The main contributions and research work are as follows:1. Analyzes the necessity of wastewater treatment and the status of wastewater treatment in our country. Comparing with the other country, points out the development trend for wastewater treatment in our country.2. The development of control strategy in activated sludge process are reviewed detailed.3. Introduce the principle and process of activated sludge process, and make detailed introduce for it's typical technics(CAST); then expatiate the selecting standard for technics of wastewater treatment plant.4. In allusion to the problems of great inertness, long-time lag and some uncertainty, which are ubiquitous in the system of CAST technics, the idea of intelligent fuzzy control is introduced. Based on simple fuzzy controller, it modifies quantization curves and anti-quantization by measuring current states to adjust the process of digital fuzzy quantization and anti-fuzzy quantization. This makes the new fuzzy controller regulates automatically within minor error dimension so at last realizes high precision control of dissolved oxygen.5. An auto-control system project used in wastewater treatment plant based on Ethernet and PLC is introduced; and for the pumping station, using spell ideology, and introduces the software realization using PLC.The successful application indicates that the control satisfies the technology requirement and control requirement of the process of CAST technics wastewater treatment.