The design of storm drainage storage tanks for self-cleansing operation
Ellis, David R.
PublisherUniversity of Manchester
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The use of storage tanks in sewerage systems has increased in recent years. The primary functions of such tanks are to attenuate flow and to retain pollutants within the sewer system. The main problem is to provide storage and effective separation of gross and suspended solids without incurring poor self - cleansing and associated high maintenance costs. The size of the required storage volume is dependant on the purpose for which the tank is to be used, but the end product of any design analysis is a fixed volume of storage. This project has involved the development of fullscale and laboratory computer controlled monitoring systems for the purpose of flow visualisation and digital imaging and for the comparative assessment of the sediment removal performance of different geometric configurations of overflow and storage tank. These systems used sophisticated control procedures and the latter had the facility to generate a flow hydrograph of any shape and duration and to superimpose on this hydrograph a pollutograph of synthetic cohesive sediment of any distribution. A wide variety of tanks have been constructed, mainly rectangular in plan shape (some circular), but both online and off-line and with and without an overflow structure. The use of benching to the chamber floor and the inclusion of a dry-weather flow channel were common but not universal features.