Theory Analysis And Design Method Research Of Vacuum Sewer System In Lake District

At present, because of the high expense and complicated terrain, many districts haven't laid the drain pipe. This dissertation is to develop a late-model sewer system named vacuum sewer system. It decreases the buried depth greatly through taking smaller pipe diameter and laying pipe like ladder. It can climb the hillside and is more flexible and can economize the expense.Based on the related successful experience of foreign country and the experimental research of our scientific research group, this dissertation perfects the holistic design method from user to terminal, it mainly contains three parts: valve pit, pipeline, vacuum station. The drain pipe from the users connects to the valve pit which is divided into two layers. When the wastewater in the down layer is full, the vacuum interface valve in the upper layer would open and pump the wastewater into the vacuum pipe by use of the different pressure. The vacuum pipe is laid by terrain, a lift would be set at intervals in the flat or uphill, and there is no lift in the downhill. Vacuum station is the power resource of the whole system, it mainly contains vacuum pump, drainage pump, wastewater collection tank and vacuum reserve tank. The work parameter of vacuum pump is the key point of design, the working time of it should be limited between one and half and three minutes.Based on the design method of vacuum sewer, this dissertation takes a lake district which is four square kilometers and has nearly six hundred persons as an example to design. Because of the limitation of collection radius, in order to connect every user, I separate the service area into three parts, and use three main pipes to collect wastewater. According to the real flowrate of every pipe, the main diameter of pipe is 110 millimeters and 160 millimeters. The pipe of 110 millimeters is lifted every fifty meters, 160 millimeters is lifted every 70~80 millimeters. The maximum design flowrate is 3.03 L/s, the working pressure of vacuum station is 0.03~0.05 MPa. Through calculation, the vacuum pump capacity is 110L/s, the sewage pump capacity is 3.03L/s, the sewage vessel volume is 1636.2L. The construction expense is nearly 2.2 million yuan which is lower than using gravity sewer.This dissertation develops a convenient calculating program by use of visual basic. According to the real terrain and design requirement, user needs to draw the pipe route figure, then carry the flowrate calculation, head loss calculation and judge whether the pressure value is beyond the design requirement, at last, user could calculate the related parameter of vacuum pump, sewage pump, vacuum reserve tank and wastewater collection tank.This dissertation also analyzes the pipe head loss under different hydraulic models such as single-phrase, symmetrical-phrase and departed-phrase. Based on the academic analysis, we designed a simple experimental device in order to test the coefficient of head loss formula and provide a more precise formula which based on theory and experiment. And educed some meaningful conclusion, such as when the gas-liquid velocity decreased, there was orbicular flow, columned flow and flexuous flow one after another, the frictional resistance loss increased by the increase of flowrate and decreased by the increase of pipe diameter.