Anaerobic - Aerobic Wastewater Treatment System Design

City sewage treatment is the primary solution of the water pollution problem around the city. This paper describes the application of the SIEMENS S7-200Smart and S7-300PLC in a city sewage treatment project. By using communication and centralized system, the system status of the entire treatment line could be monitored and controlled real-timely, and the precision of every phase are guaranteed. This system improve the efficiency of the aeration significantly, and save large amount of the electrical energy than the tradition way, the labor intensity of workers is reduced at the same time, so this system has a high practicality.This subject designs the automatic control system of the city sewage treatment, mainly focused on:First, each process of the city sewage treatment is generally introduced in this paper. The control system is mainly consist of pretreatment system, flocculation and neutralization system, uplifting pump, Anaerobic fermentation phase, transportation unit, Aerobic fermentation phase, detectors and sensors.Secondly, Designed the control scheme according to the process of the city sewage treatment. The control system is divided into two grades, LCP and MCP. The LCP adopt a new listing module, SIEMENS S7-200SMART as it’s controller to collect and output the digital and analog signal, to monitor the status of the high pressure air generation phase, including ON/OFF control, alarm control, and the precise control of the flow. MCP controls all the4LCPs, realize the main PID control loop, and communicate with the Kingview and LCP. Through Kingview interface, the operator can control all the phases, and monitor all the parameters on the IPC.Thirdly, system control programs were designed, including PLC program, HMI program and IPC program. System has manual/remote/automatic operation modes.Lastly, accomplished system debug. According to the control scheme of water desalination, we debugging the hardware equipment, software program and IPC interface.This city sewage treatment system fully fulfilled client’s demand. The output water meet the national sewage level II, it can be used as freshwater for agriculture and industry. Besides, it has a good practicability and high efficiency.