With the rapid development of cities, environmental problems become more and more important. Wastewater is the main factor that destroys the environment. At present, the automatic control system of sewage treatment in China is relatively backward, the cost of sewage treatment remains high, and the quality of treated sewage discharged by sewage treatment plants is unstable. Therefore, how to establish an effective automatic control system, optimize the operation effect and reduce the operation cost is of great significance.

This paper introduces the basic process and flow of urban sewage treatment, and designs a set of sewage treatment system based on PLC control through research.

This paper first introduces the hardware structure, working principle and basic principles and steps of design of PLC control system, and then takes SBR sewage treatment process as an example to illustrate the application of PLC in sewage treatment process. Firstly, according to the requirements of sewage treatment, the electrical control and automatic control circuits of the equipment are designed, which mainly include the start and stop of the equipment, status signals, fault signals and signal acquisition. Finally, the PLC control system is designed according to the process requirements, including the selection of PLC, the allocation of system resources and the programming of PLC according to the sewage treatment process.

Keywords: sewage treatment, SBR, PLC