The Yangshupu Water Treatment Plant in Shanghai, China is one of the oldest and largest drinking water plants in the country. Shanghai Waterworks Shibei Co. Ltd. operates the plant, which was built in 1883. The Yangshupu plant serves approximately 2.5 million people in Shanghai and the surrounding areas and treats 1.5 tons of drinking water daily.
Shanghai Waterworks upgraded the facility's drinking water disinfection technology in the 1950s. The agency realized it needed to upgrade the plant's chlorination/liquid feed systems 40 years later, to increase treatment efficiency and to meet new national and local public drinking water standards.
Solution made ready
Chevalier, the Hong Kong-based engineering firm that worked on the project, contacted Siemens Water Technologies in 1998. Siemens was familiar with the facility, as it had provided chlorination equipment for the original plant. For the latest plant upgrade, Siemens provided three kinds of technology for chlorination, liquid feed systems and water quality analyzers from the Wallace & Tiernan product line. The facility added more disinfection equipment in 2005.
In total, Shanghai Waterworks installed eight 50-200 evaporators, 25 V2000 chlorinators, eight 60-225 ammoniators, and 21 Micro/2000 water quality analyzers. Twelve of the chlorinators are used pre-chlorination; the remaining 13, for post-chlorination. Likewise, half of the evaporators are being used for pre-chlorination while the other half are used for post-chlorination.
The system operates under a vacuum produced at the aspirator-type injector. Vacuum is transmitted to the V2000 control unit and then to the vacuum-regulating valve. Gas enters the vacuum-regulating valve from the evaporator, which has evaporated liquid chlorine into gas. A diaphragm in the vacuum regulator senses vacuum on one side and atmospheric pressure on the other side. A spring-loaded stem maintains a proper vacuum ahead of the V2000 unit and permits gas to flow under vacuum to the chlorinator.
Still under vacuum, gas enters the control module where flow rate is measured through a rotameter and is controlled at the V-Notch. Gas passes to the injector where it is dissolved in the water stream, and the resultant solution is discharged to the point of application. Water quality analyzers then measure and monitor chlorine residual in the plant's piping system and control the chlorinators' output to a given set point.
Results positive
Installing the disinfection systems increased chemical dosing capacity as well as plant capacity. They also improved the safety of using chlorine equipment. The analyzers allow Shanghai Waterworks accurate residual monitor and control, which has improved water quality. Maintenance costs have also greatly decreased since installing the equipment.
Thanks in part to its disinfection system upgrade, the Yangshupu Water Treatment Plant began meeting all of the 88 parameters set forth in China's “Urban Water Quality Standard,” long before the June 1, 2005, deadline. The disinfection systems will also help Shanghai attain U.S. EPA or the present European municipal water quality standards by 2010, as part of the city's water quality plan.
