Study On Biological Stability Of Drinking Water And Pollution Index In Distribution System

This dissertation focuses on research the biological stability of raw water, effluent from each water treatment units and distribution system water, and water pollution in distribution system at different cities of Yangtze Delta, including Shanghai, Hangzhou and Zhenjiang. The following contents have been studied comprehensively: the method of assimilable organic carbon (AOC) measure; the biological stability of raw water in Yangtze Delta; the removal characteristics of AOC by purification technology and process; the variability of AOC concentrations in water distribution system(WDS); the establishment and testify of the new method to evaluate the water pollution in WDS.During the research, the method of AOC measure has been improved. The 100mL Erlenmeyer flask with ground-glass stopper are introduced to instead of using 45mL borosilicate glass vials with TFE-lined silicone septa. Moreover, the volume of sampling water is increased from 40mL to 100mL, the number of water samples reduced from 9 to 6 correspondingly. The improved method of AOC measure decrease the test working intensity which will be in favor of further application.The DOC average concentrations in raw water from Yangtze River (Zhenjiang) and Qiantangjiang River (Hangzhou) were about 1.74 and 2.18mg/L respectively. The AOC average concentrations were 102 and 113ug/L, which shows its biological stability was at critical zone. However, the DOC and AOC average concentrations in raw water from Huangpujiang River were about 5.83mg/L and 188ug/L, which shows its biological stability was more serious. A lot of experiment results have testified there are close relationships between AOC and DOC concentrations in raw water from Yangtze Delta. The removal characteristics of AOC by conventional treatment process, O₃-BAC advanced treatment process and membrane separation treatment process were system studied, which provides the important reference to produce biological stability drinking water, develop new water treatment process and renovate present water treatment process.It worked out the theoretical calculation formula of AOC concentration in distribution system water, and proposed the corrected models for detecting the variability of AOC in distribution system water in accordance with free chlorine or chloramines disinfection as well. Based on the investigations and analysis of residual chlorine and AOC concentrations in distribution system water, it suggested that, in order to effective control the regrowth of microorganism in WDS, the concentrations of free chlorine should be higher than 1.0mg/L, and the chloramines should be higher than 1.5mg/L when the AOC concentrations in finished water was higher than 100ug/L.It's the first time that the new evaluation method on water pollution in distribution system was proposed and established, which named distribution system water pollution index (DSWPI). As a general criterion for evaluating water quality,...