FLOW AND POLLUTANT MEASUREMENTS IN A COMBINED SEWER SYSTEM TO OPERATEA WASTE-WATER TREATMENT-PLANT AND ITS STORAGE TANK DURING STORM EVENTS

Urban storm drainage is considered using an integrated approach taking into account all parts of the sewer system: pipes, storage tanks, ove rflows, treatment plant and receiving waters. This paper presents an e xperimental research in Boran-sur-Oise (France) where continuous measu rements are carried out in the combined sewer system (catchment area 6 1 ha), in the storage tank (245 m(3)) and in the treatment plant (3000 p.e.). One of the objectives is a comprehensive knowledge of effects of storm events on treatment plant process and efficiency. Catchment s ewer system, storage rank, treatment plant and measurements are descri bed. Results for an autumn rainfall are given as an example. Many impa cts on the treatment plant are observed. Despite the lend increase com pared with dry weather periods, especially for TSS and ammonia, the pl ant efficiency remains satisfactory. Short-term and long-term impacts are distinguished. New rules for storage tank operation are proposed t o avoid hydraulic plant overloading and to use the stormwater solids-s ettling properties. These rules will be tested in the future to verify their compatibility with receiving water quality requirements. Measur ements in upstream sewer system could also be used in the future to op erate stormwater treatment systems during storm events.