Study On Health Risk Assessment Method Of Chemical Contaminants In Reclaimed Water

In the grim situation with serious shortage of water resources currently, the application of reclaimed water becomes increasingly widespread and accordingly the safety issues are also increasingly prominent. To ensure the safe recycling and large-scale application of water reuse, it is very necessary to establish the model system of reclaimed water risk assessment which is suitable for China's national conditions and evaluate comprehensively the environmental risks in the process of water reuse in order to provide a theoretical basis and data support for risk management and control of reclaimed water.Fifteen typical conventional indexes and nine heavy metal indexes are selected in this paper for water quality detection of reclaimed water from the A recycling plant in Tianjin. Then lognormal distribution of the detecting results is tested for each index. Some conventional indexes with varying degrees of risk of exceeding standard limits are found thought the calculation of water quality assurance rate on the basis of distribution function derived from K-S test.According to the lognormal distribution function of each heavy metal index combined with its toxicity factors and exposure parameters, carcinogenic risk and non-carcinogenic risk are evaluated for occupational exposure and non-occupational exposure in various recycling ways including landscaping, urban greening, road spraying, architecture and entertainment water reuse by the method of Monte-Carlo. The results show that carcinogen risk of each water reuse way is within an acceptable level, but not reaching the negligible level, while non-carcinogenic risk reaches the negligible level. The proportion in the total carcinogenic risk for each heavy metal is Cr> As> Ni, among which Cr accounts for 99.72%. The proportion in the total non-carcinogen risk is As> Cr> Mn > Cu> Ni> Zn, among which As accounts for 79.92%. Among the reuse ways, the risk by the occupational exposure in landscaping, urban greening and road spraying is much bigger than the risk by non-occupational exposure in landscaping, urban greening road spray and architecture reused water.