| Safety is the most important subject to water supply, which includes two aspects, hydraulic safety and water quality safety. The major purpose of this study is to build an overall concept of water supply safety by considering water transmission- water distribution- water users as a system.The hydraulic safety of water transmission system was studied in this study as a part of the project named "Long-distance Water Transmission from Mopanshan Reservoir to Harbin City", while the water quality safety of water distribution system was studied as a part of the national "863" research project.Detailed studies on gas gathering and exhausting mechanism in long-distance transfer pipeline were conducted, and critical angle of the pipeline was also estimated by analyzing the mechanism of trapped air pocket formation. The results of calibration on 221 air valves installed along Mopanshan long-distance transfer pipeline showed that the locations of these air valves were appropriate and water hammer could not be occurred by air bag. Due to rough terrain, various U-tubes with different spans and levels were inevitable, which may result in oscillation even the destruction of the pipelines. Based on oscillation mechanism of hydraulic drop, a new concept of hydraulic stable transition was developed and it was recommended that flow test should be increased from 0.4 m3/d to 5.5 m3/d gradually. Finally, successful flow test was obtained by using the developed method. Moreover, roughness coefficient n value (0.0116) for PCCP pipe used was also calculated by actual measurement, which was lower than (reduced by 10.8%) current n value (0.013~0.014), and will provides an important basis in the design and operation for other similar projects.In this study, a transient flow model of long-distance water transfer system was developed, and motion equation and continuity equation were used for the simulation of water hammer in water transfer system. By using inverse theory and characteristic method, water hammer calculations of Mopanshan long- distance transfer pipeline were carried out under different working conditions. The simulation results showed that valve closing time should be longer than 32.3 minutes at the worst working condition. This value was applied to valve closing operation of Mopanshan long-distance water transmission and satisfied results were obtained. In addition, a relationship between opening extent and friction coefficient of valve (RKV DN600) was calculated and measured, which has laid the foundation for hydraulic safety simulation.The mechanism of "growth ring" in distribution system was comprehensive analyzed and studied. The results of the study indicated that "growth ring" is the results of joint activities of the chemical corrosion, physical deposition and biological reaction. The smaller diameter could result in bigger contact rate of water in pipeline with "growth ring". Aged pipeline and longer water age could result in contamination of water quality in distribution system. In this study, statistical analysis on the distribution pipelines of big, mid and small cities in Chine was carried out. The results indicated that in most cities the velocities in distribution pipelines were in lower levels, which may cause the contamination of water quality. Analysis of variance was used to analyze the influence of each factor and the interaction between the factors on the THMs formation. The result showed that the chlorine dosage variation had the greatest impact (55% in influence) on the formation of THMs. Therefore, reducing the chlorine dosage is of great significance to reduce the formation of THMs. Finally, the hybrid chlorine decay dynamics model was developed, and model solution methods were examined, then Lagrange algorithm method was developed for simulating the decay of residual chlorine.In accordance with current situations in water quality, water quantity and pressure of distribution systems in China, a new method-distribution blocking system (DBS) for network planning, design, and reconstruction was developed in this study. The new method was applied in the water quality simulation of water distribution system in a city, and results showed that the average water age and residual chlorine decay in the distribution system were reduced by 20.1% and 12.6%, respectively. Moreover, the pressure ranges in the distribution system trended to be more equal and average pressure in the distribution system could be reduced by 12.1%. Consequently, water leakage quantity could be reduced by 13.8% by using the developed DBS method. |
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