Under the City of Shanghai, 7 huge pumping stations went on line recently pumping wastewater to Pudong for final treatment before being discharged into the East China Sea. These pump stations are part of the 6th phase of Shanghai’s Waste Water Treatment Project (SWWTP) under the auspices of the Shanghai Municiple Sewage Co.
A SCADA system was installed in the new SWWTP to control, collect and monitor data from the 7 pump stations, some of which are as far as 30 miles away from the Master station. The DNP protocol is used by the Master to communicate to all the stations, which include both Allen-Bradley (A-B) and General Electric (GE) equipment.
A City in Transition
Water management is a major issue in China. Sixty percent of China’s land mass and half of its population only receive 20 percent of the nation’s water resources. In addition to this uneven distribution, soil erosion, deforestation, land conversion, excessive water usage, drought and inefficient or non-existent wastewater management have caused China’s government to recognize the vital need to address these problems in order to maintain the nation’s development.
Shanghai is located on the east coast of China, approximately 350 miles north of Taiwan. With a population of over 16 million, the wastewater disposal needs for Shanghai reached a critical level several years ago. According to Sheng Guangfan of the China Association of Environmental Protection Industry, water pollution is still a serious problem in China.
“Because of wastewater discharge without efficient purification,” writes Guangfan, “more than one third of the rivers in China have been polluted. Water in 90% of our cities is polluted seriously and water sources in about 50% of our key cities and towns cannot meet standards for drinking water.”
Beginning in 1993, plans to build a new wastewater treatment plant in Shanghai were discussed and in 1998 the Shanghai Waste Water Treatment Project was begun. In January of 1999, General Electric International began the construction of the central monitoring control system for the second phase of the project, which included a centralized master control station and a total of 34 remote stations located throughout Shanghai, including Pudong.
The Master station, using MITS’ MOSAIC data acquisition and control technology, communicates to both Allen-Bradley and General Electric hardware. Many water control systems are PC-based and require a high level of manual intervention, but the MITS system is highly automated. While monitoring the passage of water, automatic adjustments can be made to make the most efficient use of energy and pumping equipment and pinpoint problems in emergencies.
DNP Protocol Specified
Immediately following the installation of the central control system, Rockwell Automation in Shanghai was contacted to bid on the installation of the SCADA system. In order to communicate with the end devices, the DNP protocol was specified.
DNP (Distributed Network Protocol) is an open communication protocol developed to achieve interoperability among systems specifically in the electric utility, oil & gas and water/wastewater industries. This non-proprietary protocol, available worldwide, was designed to optimize the transmission of data acquisition information and control commands. It is a highly efficient and reliable communications protocol between substation computers, RTUs, IEDs and master stations. DNP is also a layered protocol, featuring time stamping and True Report by Exception (TRBE).
Since both General Electric and Allen-Bradley equipment were used in the plant, a DNP interface was needed to allow them to communicate with all of the DNP compatible end devices. Rockwell Automation Shanghai contacted their Water Industry Solution Center in the United States and were advised to contact ProSoft Technology.
“We have a strong partnership with Rockwell, which has given us access to proprietary licenses,” said Doug Sharratt, CEO for ProSoft. “This allows us to offer products tightly integrated into A-B hardware platforms.”
“Since ProSoft’s DNP module has two communication ports, SWWTP were able to install a PLC5 backup system as well as a redundant communication system,” said Lenus Hong, Asian Regional Sales Manager for ProSoft Technology. “DNP Port 1 is connected to the Master Station via lease lines, while Port 2 allows a modem dial up connection. If communications should go down on Port 1, the Master still has dial up capabilities.”
Phase 6 of the Shanghai Wastewater Treatment Plant is now operational. Plans are now being made to expand this system to cover the areas surrounding Shanghai.