Extending the Wupper River Association's Large Treatment Plant at Buchenhofen for State-of-the-Art Technology

Abstract

The Buchenhofen treatment plant operated by the Wupper River Association treats wastewater from 700 000 PE, roughly half of which is from industrial sources, using a conventional activated sludge process without specific nutrient elimination. There is a management plan for the receiving waters of the treatment plant, the Lower Wupper. The main classes of use for these waters are specified in the plan. Use for recreational angling imposes the strictest limits for these waters, entailing a demand for water quality class II and imposing correspondingly stringent requirements on the purification capacity of the Buchenhofen treatment plant. The Institut für Siedlungswasserbau, Wassergütewirtschaft und Abfalltechnik of the University of Stuttgart has been commissioned to evaluate realistic treatment objectives in the treatment plant and to prepare concepts for extending the plant to provide advanced treatment. The most effective form of nitrogen elimination for the advanced concept has proved to be a single-stage activated sludge process with nitrification and pre-denitrification, while the most effective method of eliminating phosphorus is simultaneous precipitation followed by flocculation filtration. Tests have shown that large activated sludge tanks are not in themselves sufficient to ensure advanced nitrification without occasional peaks. Good on-line process monitoring and control are also necessary, as is buffering of inflow peaks. A filtration stage will be added to the plant, coming on line in 1992. Advanced biological treatment based on results from a commercial-scale pilot plant should be completed by 1996. Total costs for extending the whole plant are estimated at more than DM 130 million.