Research On Deposition Characteristics Of Sewers Pollutants

This article has taken the sewer networks system of Xi’an and Kunming as the object of the research. The existing problems of sewers and the deposition of pollutants in the sewers are investigated, also the variation of sediments and the factors which were related to the sedimentation are analyzed, by adopting sonar detection and the pipeline robot. Many comparison investigations such as the existence and formation of sediments have been taken in the different city. The characteristics and physicochemical properties of sewer sediments is discussed in this paper.The results showed that the sedimentation problem in Xi’an and Kunming is on a serious level. The sediments exist within 80% sewers in the investigated area of the typical cities. Solids in the combined sewer system is easier to accumulate than separate storm sewer system. The average sedimentation in different type of sewers have different characteristics, i.e. Branch sewer>Sub-main sewer>Main sewer. The thickness of sediments in branch and sub-main sewers was 3-4times higher than the main sewers, sedimentation blockage problem was easy to occur in the branch sewers, while the average sedimentation in main sewers was usually below 15%, which indicated the better drainage situation. The sewers which have the small diameter are easy to be blocked, pollutants in the branch and sub-main sewers are easy to accumulate than main sewers. Sediment condition of different cities is closely linked to the drainage system, water quality conditions, rainfall intensity, rainfall factors such as time and space distribution.In addition, physicochemical properties of the pollutants of sediments is different in various area, so we investigated and collected the sewer sediments from residential area, service area, cultural district, and business district. The particle size, density, organic matter content(VSS/TSS) and pollutant content of the sediments were analyzed by experiment. The results showed that there were different characteristics for the sediments located in different areas. The size of the sediments was business district > cultural district > residential area > service area. As for VSS/TSS, the relationship was residential area > cultural district > business district > service area. It was negatively correlated with the dry density and positively correlated with the water content. The content of sediment showed significant differences in different functional areas. The size of COD was residential area > cultural district > service area > business district, and the size of TN goes residential area > cultural district > business district > service area. As for TP, the size of was residential area> service area > cultural district > business district and TP are more likely to combine with the small particle. The content of heavy metals in business district was the biggest in all functional areas.