THE CHARACTERISTICS OF AN IN-SEWER EROSION EVENT ? OBSERVATIONS FROM ENVIRONMENTALLY CONTROLLED ANNULAR FLUME - op internet

This paper provides an overview of a collaborative project recently completed at WL Delft Hydraulics. It describes tests in an annular flume, in which sewer sediment deposits could be formed under carefully controlled and monitored environmental conditions and then subjected to a test series in which the bed shear stress was progressively increased. The characteristics of the eroded sediment were then closely monitored. The sediment deposits were formed using two different types of sewer sediment. The deposits in the reported experiments were formed using real in-sewer sediments, from a catchment in the UK (Dundee) and from a catchment in the Netherlands (Loenen). During the erosion tests, total and volatile suspended solids concentration, particle size distribution of the eroded sediment, and COD and DO levels were all recorded. In addition, the biodegradability of the eroded sediments were also analysed using a respirometric method. This provided the most detailed data set covering the physical and biochemical aspects of an erosion event associated with insewer sediments ever recorded. The bed surface topography was also measured so that the influence of the deposit formation condition on bedforms could also be examined.