Intelligent Control Of The Chemical Wastewater Treatment

Treatment of chemical wastewater is different from that of sanitary sewage, with the inflow of device wastewater and more stable water flow. Taken the pulverized coal gasification as the example in the aspect of water quality, its inflow water COD>1000mg/L, and NH4>200mg/L, which are triple of those for sanitary sewage. When we adopt the conventional methods for treatment, it is difficult for the outflow water quality to reach the national standard. Therefore based on the two-stage A/O(Anoxic/Oxic) high-efficiency nitrogen-removal technique, the method of separate control respectively for technique and control index is proposed, whose effect is better than the method by using a single complex intelligent algorithm to implement once control for technique and control indexes.According to the development and application features of different wastewater treatment systems, based on the analysis of internal biochemical reaction mechanism of activated sludge wastewater treatment, the A/O technique is analyzed, mathematical model is built and analyzed which is based on the ASM(Activated Sludge Model)proposed by IAWQ, and finally the best control index of DO(dissolved oxygen)is 1.6mg/L are obtained with in the allowable bound of technique requirements with the outflow water quality as the constraint condition. Meantime, based on the best control index, the fuzzy control strategy is proposed aiming at the uncertainty and big lag of DO control, and moreover the control effects of PID and fuzzy PID are compared through the MATLAB simulation to determine its strong robustness. Finally according to the practical engineering requirements, PLC controller is used to design the intelligent control system through the TCP/IP communication protocol,and meantime according to the established fuzzy table, the sequencing of incremental fuzzy PID is realized by PLC controller, and the related report forms 、monitoring system are realized in upper computer WinCC(Windows Control Center), The wastewater treatment control system is completed in the end.The system was implemented and debugged at a chemical sewage plant in NanJing. Logical control of the system is good, and the control effect of traffic and DO is good after the fuzzy PID control. The level of system automation is improved.