Study On The Safety Guarantee Of Drinking Water Source

The safety of drinking water is closely related to daily life,and the safety of drinking water source is the basic guarantee of drinking water safety.In recent years,more and more attention has been paid to the safety protection of drinking water source in Jiangsu Province.Changzhou is located in the Yangtze River Delta region and one of the important cities in Jiangsu Province.To ensure the safety of the drinking water source of Changzhou is a powerful guarantee for implementing the ecological civilization construction of Jiangsu Province and winning the battle of pollution prevention and control.Four drinking water sources in Changzhou from 2017to 2019（Yangtze Weicun water source,Daxi Reservoir water source,Shahe Reservoir water source and Changdang Lake Sudu water source）were taken as the research objects.The risk sources around drinking water sources were investigated,and the safety of water quality and quantity was evaluated,and targeted protection measures were put forward.Through visiting and investigating the risk sources around the water source protection area,the research results show that there is no human interference in the first-level protection area of the water source,and there are also some risk sources such as agricultural pollution,life pollution and ship pollution in the second-level protection area,quasi-protection area and around the protection area.Single index method,entropy weight comprehensive health index method and water quality health risk assessment were used to evaluate the water quality safety of drinking water source in Changzhou.The concentration fluctuation of 6 conventional indexes（permanganate index,dissolved oxygen,total phosphorus,total nitrogen,ammonia nitrogen,five days biochemical oxygen demand）in 3 years and the proportion of water quality categories were analyzed.The results showed that the total phosphorus and total nitrogen in Changdang Lake Sudu water source exceeded the standard,and the maximum values of index concentration were 2.4 times and 0.86 times of the standard limit ofⅢfor surface water,respectively.All the indexes in the other three water sources met the standard of surface water.In addition,permanganate index and five-day biochemical oxygen demand of Changdang Lake Sudu water source were potential indexes exceeding the standard,while total nitrogen of Daxi and Shahe Reservoirs water source was potential indexes exceeding the standard.The entropy weight comprehensive health index of the four water sources was Yangtze Weicun water source（0.645）,Daxi Reservoir water source（0.694）,Shahe Reservoir water source（0.679）and Changdang Lake Sudu water source（0.438）,and the corresponding water quality safety and health grades were good,good,good and medium.The total health risk value of water source at different exposure dose levels ranged from 6.34×10^-5 to 8.16×10^-5 a^-1.According to the health risk range recommended by the US Environmental Protection Agency,there is a certain risk in the water source.In the non-carcinogenic risk assessment,the single item risk values of fluoride,nitrate,copper and lead were high.The single risk value of three chemical carcinogens in carcinogenic risk assessment was hexavalent chromium>arsenic>cadmium.The current,near and long term（2025 and 2030）water security of Changzhou was evaluated by means of data collection and field investigation.The evaluation results show that the water security of Changzhou can be guaranteed at present,and there are hidden dangers of high load water supply in water source area in 2025 and 2030.It is predicted that the operating load of the existing water source area will reach 93.58%in 2030.Based on the investigation of risk sources around the water source area,the results of water quality safety assessment and water quantity safety assessment,the problems existing in the drinking water source area of Changzhou were summarized and targeted protection measures were put forward,so as to provide some reference and suggestions for the protection of river-type,reservoir-type and lake-type water source areas.