Research progress on the control of sediments in the drainage pipe

The water pollution of rivers and lakes caused by the erosion of drainage pipeline sediments in rainy days has become a dilemma for the continuous improvement of water environment quality in China. An in-depth understanding of pipeline sediments and their deposition mechanism is essential for water pollution control. The formation and characteristics of pipeline sediments, the main components of microorganisms or extracellular polymeric substance (EPS), and the effects of related properties on the anti-scouring characteristics of sediments were reviewed. The results showed that the sediments in drainage pipelines were mainly formed by the sedimentation of solid particles carried by sewage, and mainly included three types, i.e. bottom coarse-grained sediments, organic layer and biofilm. Because the sediments were rich in microorganisms and could secrete EPS, the viscosity of EPS could significantly increase the scour resistance of pipeline sediments. By controlling or degrading the polysaccharide component in the EPS of the sediments, the erosion resistance of the sediments could be reduced, which was expected to provide a new idea for controlling the sedimentation of the pipelines. At present, the domestic and foreign methods for controlling the sedimentation of pipelines were mainly through offline and online hydraulic scouring or mechanical dredging. The future research direction should focus on systematically studying the erosion resistance characteristics and influencing factors of sediments in the real drainage pipe network, and then propose more effective control technology methods.