Environmentally Compatible Disinfection of Drinking Water

Echthausen Water Works supplies twenty communities with some 20 million cubic meters of drinking water. Wasserwerke Westfalen GmbH is a subsidiary company of both Dortmunder Energie- und Wasserversorgung GmbH and Gelsenwasser AG, and is the largest producer of drinking water in the German state of North Rhine-Westphalia. Ingo Becker, managing director of Wasserwerke Westfalen GmbH, said that all water works would need to install additional treatment stages in the next few years in order to meet future drinking water quality requirements, and that most of these stages would involve physical processes. This would involve an investment of approximately 20 million Euros at each location.

Five Barrier M 3800 type UV plants have been installed in Echthausen. They have replaced the previous chlorine dioxide stage, and complete the water treatment. Rob van Esch, the Siemens project manager, explained, "UV plants are often more effective than other disinfection processes, particularly against spore forming microorganisms which can encapsulate." In addition to that, the taste of the drinking water remains unchanged, and the operational handling of chemicals is eliminated.

The UV plants are operated in parallel, and have an average of 2,200 and a maximum throughput of 4,000 cubic meters of water per hour. Each plant can be separately controlled to match requirements. The continuously variable control of the intensity of irradiation delivers exactly the required "dose". Electronic control gear ensures high efficiency: combining the safest possible disinfection with energy-saving operation.

The Simatic PCS7 process control system is used to control the plants. This enables the UV disinfection stage to be seamlessly integrated into Wasserwerke Westfalen's overall control concept, which is also based on PCS7. The peripheral equipment is connected by ET200 signal modules and communications via Profibus are also integrated. The UV plants can be operated either with the WinCC HMI system from the local Echthausen works control center or from the control center in Hengsen.

The main reasons for winning the order were the integrated control concept, and Siemens's ability to offer both the design engineering and the construction of the plant.