Research On Water Quality Survey And Health Risk Assessment

At present,centralized water supply is widely used in Chinese cities and towns,and the quality of drinking water is effectively guaranteed.However,with the pollution of water sources,the aging and corrosion of water supply network,and the mismanagement of high-rise secondary water supply facilities,the quality of tap water in residents’ homes has been widely concerned.Therefore,the quality of terminal drinking water needs to be continuously monitored before strict and targeted management measures can be formulated to ensure the water quality safety.This paper,based on a survey on water quality control in a research area of Xiamen city from 2009 to 2017,investigated and analyzed the water quality situation of residential drinking water,and evaluated the possible health risks to human body caused by key pollutants.It mainly includes the following two parts:1.According to the national standards related to drinking water,the quality qualification of each monitoring indicator was investigated,and the water quality qualification rate and its variation rule of tap water and secondary water supply in different stages,seasons and streets were compared.A total of 933 samples of domestic drinking water from 2009 to 2017 were monitored,among which 618 were taken from tap water and 315 were from secondary water supply.It was found that 457 samples of tap water and 174 samples of qualified water were qualified,which indicated the qualification rates for them were 73.95 and 55.24%,respectively,and the overall the qualification rate of the quality of drinking water was 67.63%,within the average level of Xiamen city in the same period.It was also found that the main unqualified indexes were free residual chlorine,turbidity and iron,and their qualification rates were 76.53%,91.21% and 93.89%,respectively.There was no significant difference between the qualification rates of drinking water quality in different seasons,indicating that the water quality of annual water supply in the study area was stable.The water quality qualification rate of streets close to the water plant was significantly higher than that of streets far away from the water plant(x2=6.48,p<0.05),indicating a significant decrease in water quality in the water conveyance process.From 2016 to 2017 the chromium concentration in the tap water was significantly higher than that in the ex-factory water,and the difference was significant(t=3.67,p<0.01),indicating that the finished water was polluted by chromium when it was transported to the users through the faucet,but the specific reasons need further investigation and study.2.The possible health risks caused by drinking water and skin contact were evaluated in 10 indicators including arsenic,cadmium and chromium in the water quality from 2012 to 2017,using the “four-step” health risk assessment model recommended by the United States Environmental Protection Agency(USEPA)The results showed that the health risks caused by drinking water to the population from 2012 to 2017 exceeded the maximum acceptable level recommended by the Netherlands National Institute of Public Health and Environment and other institutions(1 ×10-6/a),and the maximum annual health risk was 6.66×10-6/a.The carcinogenic health risk was much higher than the non-carcinogenic health risk,and the children’s health risk was higher than that of adults.Arsenic was the only carcinogenic pollutant in the evaluation results and also the main source of health risk.Although the average concentration of arsenic in drinking water of each year reached the standard,the carcinogenic health risk of arsenic in drinking water for both adults and children exceeded the maximum acceptable level from 2015 to 2017,indicating that even the trace arsenic pollution in drinking water might still cause certain carcinogenic health damage to the population.As for the non-carcinogenic pollution index,only when fluoride was at the maximum concentration,the non-carcinogenic health risk value for children caused by drinking water was higher than the negligible level,with the highest risk value being 1.30×10-8/a.Bathing was the main way to cause the health risk of skin exposure,and the health risk caused by other wading activities was extremely low.However,the results of this study showed that the health risk caused by skin exposure to drinking water was lower than the negligible level,so it would not cause the carcinogenic and non-carcinogenic health damage to the population.In addition,there was a significant difference between the health risk value calculated by using the population exposure parameters recommended by EPA and the result calculated by using the recommended value in China(t=3.90,p<0.01).Using the calculation results of the EPA recommendation,the health risk value of the adult population was 10.95% higher than the recommended value of China,while the health risk value of the child population was only 66.03% of the recommended value of China,which would lead to the increase of false positive rate of health risk evaluation results of the adult population and reduce the sensitivity of the child population.In addition,the uncertain factors in the process of water quality monitoring and health risk assessment were analyzed and discussed,and the following suggestions were put forward: 1.We should improve the ability to detect water quality in basic units.2.Chlorination stations should be set up in appropriate areas to improve the qualified rate of water quality.3.We should strengthen supervision of secondary water supply units.4.Authorities should take measures to control arsenic in water.The safety and changes of drinking water quality can be understood through the study of the monitoring results of drinking water quality.By studying the possible health risks of drinking water to different populations,scientific basis can be provided to adjust corresponding regulatory measures in time.Therefore,the research methods and results of this study are of great significance and reference value for guaranteeing the quality and safety of drinking water.