The Study On Sediment Deposition And Sewer-sediment Control In Combined Sewers

The urban sewer sediment not only influences transportation space but alsoincreases the flow resistance, thus affects the flow-carrying capacity of pipe. Whensediment accumulates to a certain level, it will even cause blockage and have animpact on the normal running in sewerage system.This paper studies on the combined sewer system in the old Guangzhou cityalong the banks of Xinhepu River. Before the study on pollutant characteristic ofsediment and sediment control technology, we did a preliminary investigation forcondition of sediment in the relating sewers.The investigation results indicate that:(1) sediment is ubiquitously present inurban sewers, it is found deposited on catchment surfaces, in gully pots and in drainsand sewers;(2) there are nearly75%sewers in which sediment deposited. There aredifferent degrees of deposition found in different areas. The more seriously polluted,the more sediment;(3) we also find that pipe gradient, pipe diameter and its materialinfluence the deposition condition significantly.Through the study on physical and chemistry characteristic of the sediment incombined sewers, it shows that the size of most sediment is below0.25mm, whichaccount for about60%degradable organic matter,70%phosphorus and70%nitrogenlocated in them.This subject divides sediment control technology into three categories: thesource control、sewer sediment cleaning and optimal design of drainpipe networks. Bycomparing the relative performance of four sewer cleaning techniques and combiningwith domestic and international status of sewer cleaning, appropriate methods wereproposed for the local sewer cleaning in Guangzhou to control sewer sediment incombined sewer systems.So far, studies on sewer sediment are relatively less in China, we are lagging farbehind from other developed countries in relating subjects. The subject providestechnical support for the effective sewer cleaning projects, operation management,reducing pollution load of the overflow in rainy days and maintenance of urbandrainage systems.