Application Of Vacuum Drainage Technology To Interception Projects In The Riverfront In Old Urban Districts

A vacuum interception simulative system was developed to solve the problemsof the traditional gravity interception projects in old urban districts in this thesis,through developing the key device, studying and selecting the pipeline properties andpower equipments. On basis of the simulative system, the experiments on hydraulicsfeatures and safety operation of vacuum interception system were carried out. Theflow pattern and conveying mechanism of vacuum pipeline were discussed and bycombining the experience form international wide, a calculation method was studied.Depend on above, a demonstration project of vacuum interception system wasdesigned and constructed in Changzhou, Jiangsu. In addition, the environment effectand engineering contribution was evaluated.(1)Electric control valve and float type/pressure inductive vacuum interfacevalve were designed; the circulation ability of valves achieved to3~7L/s and thenegative pressure loss degree and medium sensitive performance met the Europeanstandard EN1091:1996. The best suitable vacuum pipeline is HUPV Service Pipe,compressive strength>1.0MPa. The water-ring vacuum pump and non-clog sewagepump were recommended, and specific categories should be suitable for the set modeof pumping station.(2)The local servo negative pressure decides drainage capacity, batch volumeinfluences drainage time and the ratio of gas to liquid influences transport volume andefficiency. The average rate of flow is3~4L/s under the condition that the diameterof vacuum pipeline is50mm and the local servo negative pressure is above30kPa.The performance of efficiency characteristics shows that water flow andpressure-keeping interval are the main factors of vacuum pump energy consumption.Water flow is negatively correlated to consumption. When pressure-keeping intervalsets in low range, the pump will run in low consumption, adversely when shortpressure-keeping interval.(3)According to the characteristics of experiments and abroad design experience,the gas/liquid ratio, pipe diameter and system capacity were analyzed, the designcalculation formulas were suggested and a optimization design using vacuum valve local servo negative pressure anti-calculation system maintain pressure and vacuumpump station pressure-keeping interval was summarized. The results showed that thechoice of the ratio gas to liquid key parameters should depend on collecting radiusand service residents’ density. Generally, the choice range of ratio gas to liquid is2~12, the caliber DN65~250. The capacity of the system is5m in hoisting height and2500m in the horizontal distance.(4)On basis of24h outlet sewage drainage monitoring and other jobs, ademonstration project of vacuum drainage system applied on the sewage interceptionengineer was designed and constructed. The system collects sewage50~220m3withnegative pressure leakage rate <5%/h. the maximum sudden noise during systemoperates is70.3dB outdoor and91.9dB indoor, which meets the requirements ofenterprise and urban regional noise criterion. H2S and NH3were not detected at0~200ppm range around pumping station and indicated that the system did not havethe noise and smell problems. From the aspect of economic investment andinterception effect, vacuum drainage system should not applied in conventional areabut in the area of special topographical geology and so on as a beneficialsupplement of gravity drainage system.