The Effect Of Residence Time On The Pollutants Generation Of Different Raw Water In Secondary Water Supply And It’s Control Measures Research

Secondary water supply is an important segment to supply safe drinking water. Becausedrinking water stay for a long time during storage in secondary water supply, water qualitydeterioration obvious. It’s meaningful to study the effect of residence time on contaminants insecondary water supply, and give appropriate control measures.The article takes water quality of secondary water supply as research object. Drinkingwater from different distribution network was sampled to take simulation experiments. Afterstoring some time, water quality was monitored. Then, the effect of different raw waterquality and water using temperature on water quality of secondary water supply werediscussed. The main conclusions are as follows:(1) As the residence time extended (48h inside), total chlorine free residual chlorinedeclining, the total bacterial count increasing, oxygen consumption also decreasing in varyingdegrees, and turbidity value no changing. Total chlorine, free residual chlorine, and totalbacterial count exceeded standard. The time length of water quality exceeded standard weredifferent because of different water quality of raw water.(2) The bigger the initial residual chlorine value is, the faster the residual chlorineattenuation rate is, and the residual chlorine attenuation coefficient remains unchanged. Thehigher the water temperature is, the faster the residual chlorine attenuation is, and the residualchlorine attenuation coefficient becomes bigger. When the residual chlorine value remainedhigh, oxygen consumption has no effect on residual chlorine attenuation. When residualchlorine value decreased into a low level, the higher the oxygen consumption is, the faster theresidual chlorine attenuation is. In48h residence time, total bacteria count was significantlynegatively correlated with residual chlorine and oxygen consumption. The increasing ofoxygen consumption will speed up the residual chlorine attenuation and provide matrix forbacteria growth. The higher the water temperature is, the more the bacteria is. The experimentalso showed that as long as residual chlorine keep in high value, the total bacteria countmaintain qualified.(3) As the residual time extended, ammonia concentration decreased，nitrite and nitrateconcentration increased. Nitrification happened in secondary water supply. If oxidation degreeis high, nitrification is not signification. Nitrification promoted residual chlorine attenuationand bacteria growth.(4) When temperature reached100℃, all bacteria in drinking water was killed. Watersamples belong to soft water. Temperature of water has no effect on hardness. Organic compounds were monitored using GC/MS. There were28organic compounds in water in23℃. With temperature increasing, the number of organic compounds decreased(5) The article put forward control measures for preventing water polluted in watersecondary supply. Control measures included water tank or pool reforming, addingdisinfection facilities (micro electric disinfection) and using new water supply way. The watertank or pool should be reasonable designed and use new materials. The environmental healthshould be managed around the water tank or pool. Micro electric disinfection technology usedfor disinfection in secondary water supply has simple equipment, stable disinfection effect,continued disinfection ability and economical. No negative pressure technique canceled watertank or pool in secondary water supply, so drinking water isolated from air in most of time.The pollution chance was reduced. The technique can use municipal water supply pressure, soit can save energy.