Overview

As the sub-center of Nanjing's new urban area, the economic development and urban construction of XX District has entered a period of rapid growth. With the rapid development of the economy, the environmental problems in the area have become increasingly prominent. At present, most of the industrial wastewater and domestic sewage in industrial parks are directly discharged into water bodies without treatment, seriously polluting the ground and groundwater systems, affecting people's lives and health, and restricting the development of cities. At the same time, people are increasingly demanding environmental protection. Therefore, the construction of sewage treatment plants has become a top priority.

According to the city plan, the scale of XX sewage treatment plant is divided into two stages: the first phase is 40 thousand m3/d, and the second phase is 80 thousand m3/d. The whole production area has coarse grid, lifting pump room, fine grid, cyclone grit tank, biochemical tank, sludge storage tank, sludge dewatering room, blower room, drainage pump room and other auxiliary buildings. The process flow chart is as follows:

　　Process flow chart of sequential batch activated sludge

Design of control system

　　System structure diagram

This system uses NA400 PLC as the core of the control station, a total of 6 sets, namely 1# biochemical pool, 2# biochemical pool, 3# biochemical pool, 4# biochemical pool, blower room, lifting pump room. Each PLC is equipped with a touch screen, NA400 comes with 485 ports, directly communicates with the touch screen via Modbus, to achieve on-site operation, convenient and economical.

Considering that the distance between control stations is far apart, the network transmission rate and bandwidth provided by optical fiber transmission are much higher than twisted pair. Optical fiber transmission is not subject to EMI, RFI, lightning strikes and other interference, and fully meets the requirements of industrial-grade network performance and reliability.

NA400 series CPU comes with Ethernet port and optical fiber switch to form a TCP/IP ring network, which saves communication modules and is economical and reliable.

The on-site control station communicates with the on-site control sub-stations of various manufacturers through the field bus. Collect field data, detect and process various production process parameters such as water quality, flow rate, dissolved oxygen, liquid level, etc. and power parameters such as current, voltage, power, power, etc. At the same time, monitor and control the working status of each production equipment.

NA400 series PLCs are widely used in various industries, with reliable performance and can meet various control needs. As a self-designed domestic medium-sized PLC, the continuous improvement and improvement of product performance is bound to replace foreign products in the near future and become the pride of the Chinese people.