Research On Sediment In Combined Sewer

Water is the headspring of life, people can't live without water. City water is an important part of the infrastructure of the city, sewer system is vividly likened the vitals of the city, and it is impossible to maintain the normal operation of the city without water.During the operation of the sewer, a large number of solid particles deposit on the bottom, which reduce the pipe flow area, influence the normal operation of the sewer system, lead to sewage overflow, causing environmental pollution. The research group investigated and researched the sediments of combined sewer of Chaohu City.The research results show that sediments are prevalent in combined sewer, and the amount is significantly different in sewer of different areas. The amount is also different in two researches in one point. The deposition of the first survey on 800mm sewer is 25mm and the second is 35mm, which are both higher than the other points in one period.The physical parameters like dried mud density and particle size distribution of every research point are not the same, and the pollute parameters like organic matter, TN and TP are significantly different, and the two researches are also different in one point. Physical characteristics and pollution characteristics of sediments are connected with regional characteristics and the complex movement of wastewater in sewer. The first survey on green belt shows that more than 90% of particle size is between 0.075mm and 2.36mm, dry density is 0.2635g/cm3, organic matter content is 25.65%, nitrogen content is 12330mg/kg, phosphorus content is 3631 mg/kg, while the second survey shows that particle size is larger, dry density is 0.3644 g/cm3, organic matter content is 7.90%, nitrogen content is 3507mg/kg, phosphorus content is 3131mg/kg.Sediments are mixed to liquor, and COD, TN, NH3-N, TP and BOD5 are determined, which match to pollution characteristics of sediments.Combined sewage quality is resulted by dry weather flow, rainwater runoff and sediment erosion of sewerage, so the water quality is very complex. By test calculation, sediment erosion rate of pollutants are gained:COD is 22%, SS is 6%, TN is 21% and TP is 20%.