Evaluation of the cleansing capacity of a flushing tank in (sanitary) sewer systems

摘要

In flat regions it is often not feasible to provide the necessary slope for a sewer system to be selfcleansing (especially in the most upstream parts of the network). The installation of a flushing tank, that flushes the downstream sewer system once the tank is completely filled with runoff water, can be a solution. The present paper discusses the flushing capacity of a flushing tank, based on experiments carried out at the Hydraulics Laboratory of the Katholieke Universiteit Leuven (K.U.Leuven). The flushing tank (provided by Keramo-Steinzeug, Belgium) consists of a tank of 1 m height, having a diameter of 1200 mm and a volume of about 450 liter, resulting in a flushing discharge inbetween approximately 28 and 18 l/s that lasts for at least 21 seconds. The results are presented in terms of generated shear stresses and flushing lengths, depending on the pipe slope and diameter. The analysis contains both maximum shear stresses that are obtained during a small time interval and minimum shear stresses that are obtained during a larger time interval. Whereas the first are needed to erode the deposited sediment particles, the latter are needed to transport the sediment particles along the conduit.