Shanghai Zhonghan Electric: Wastewater Treatment Plant PLC Control System Project Case

I. Project Overview

A municipal wastewater treatment plant sought to upgrade its operations to enhance efficiency, ensure consistent effluent quality, and cut maintenance costs. To achieve this, the plant entrusted Shanghai Zhonghan Electric with the design, manufacturing, programming, and on-site commissioning of a comprehensive automation control system. The core objective was to deliver precise, fully automated control over the entire wastewater treatment process, ensuring reliable performance and stable, uninterrupted operation. At the heart of this solution was a customized PLC control system, engineered to meet the plant’s unique operational demands and integrate seamlessly with existing infrastructure.

II. Core Project Scheme & Configuration

(A) Control Core Configuration

The PLC control system was built around the Siemens S7-1500 series PLC (CPU 1516-3PN/DP), selected as the central control unit for its high performance, reliability, and scalability. This system was designed to handle approximately 800 I/O points (DI, DO, AI, AO), providing comprehensive signal monitoring and control across all process units, including screening, aeration, sludge recirculation, and clarification. The architecture adopted a distributed model featuring 1 Main Station and 3 Remote Stations, ensuring robust coverage of the plant’s sprawling layout. Communication between the main and remote stations utilized industrial Ethernet over fiber optics, delivering exceptional anti-interference performance and stable data transmission even in the plant’s harsh, electrically noisy environment.

(B) HMI & Hardware Configuration

To complement the PLC control system, the project included a fully integrated hardware and monitoring setup. The host monitoring system was powered by Siemens WINCC 7.5, offering advanced features such as real-time process flow visualization, historical data logging, alarm management, automated reporting, and remote control capabilities. The custom-built PLC control cabinet was constructed from high-quality cold-rolled steel with electrostatic spraying, achieving an IP40 protection rating to withstand the humid, corrosive conditions typical of wastewater facilities. A MCGS (Kunlun Tongtai) touchscreen was installed on the cabinet door, enabling local on-site operation and monitoring for quick adjustments and troubleshooting. Inside the cabinet, high-profile brand components were meticulously arranged with neat wiring, strictly adhering to international electrical safety standards to guarantee long-term system reliability.

III. Service & Implementation Process

Shanghai Zhonghan Electric delivered a full-cycle, one-stop service to ensure the project’s success:

• Scheme Design: Our team conducted thorough on-site research to map the plant’s processes, developed detailed electrical schematics, and designed both the touchscreen and host computer interfaces for intuitive operation.
• Manufacturing & Assembly: The PLC control cabinet was fabricated to exact specifications, integrating the MCGS touchscreen and assembling all internal components, including the Siemens PLC, power supplies, and communication modules.
• Software Development: Custom PLC control logic was engineered to automate core processes, from initial screening to final effluent discharge. WINCC and MCGS operator interfaces were configured to provide operators with clear, actionable insights into system performance.
• On-site Commissioning: Senior engineers were deployed to complete on-site wiring checks, network debugging, and system integration testing, ensuring the PLC control system communicated flawlessly with field devices such as pumps, valves, and sensors.
• Training & Delivery: Comprehensive operation and maintenance training was provided to the client’s team, covering system navigation, troubleshooting, and routine care. All technical documentation, including schematics, manuals, and software backups, was delivered to complete project acceptance.

IV. Project Achievements

Following commissioning, the PLC control system enabled fully automated and intelligent control of the entire wastewater treatment process. The system delivered stable equipment performance, rapid fault detection and response, and significant reductions in manual labor costs, eliminating the need for constant on-site adjustments. Effluent quality consistently met and exceeded regulatory standards, even during peak flow periods, demonstrating the PLC control cabinet’s ability to adapt to dynamic operational conditions. The project was completed on schedule and within budget, earning high praise from the client for its reliability, ease of use, and positive impact on operational efficiency.

V. Project Summary

This wastewater treatment plant project stands as a testament to Shanghai Zhonghan Electric’s expertise in PLC control system design, equipment manufacturing, and on-site commissioning. It showcases our ability to deliver customized, high-performance solutions tailored to the unique challenges of municipal environmental infrastructure. Moving forward, Shanghai Zhonghan Electric will continue to deepen its presence in environmental automation, leveraging advanced technologies like the PLC control system to drive the intelligent, efficient, and sustainable development of the wastewater treatment industry worldwide.