Risk Assessment And Management For Municipal Reclaimed Water Reuse

The reclaimed utilization of urban wastewater is an indispensable way for solving the crisis of urban water resource. Based on the broad experimental studies and risk assessment of different reclaimed water utilization, this dissertation makes a systematic study on the risk management system of reclaimed water by integrating an example of reclaimed water utilizing project in one district, which provides a scientific foundation for risk management of reclaimed water in theory and practice.On the basis of risk assessment theory, this dissertation integrates the practical utilizing ways of reclaimed water and uses the toxicology and aerosol chemical methods.etc, to make studies on the risk mutagenicity, heavy metals and persistent organic pollutants (POPs), fish-farming and volatile organic compounds(VOCs) of reclaimed water. The assessment result provides the practical foundation for the construction of the risk management system. The results of toxicology experiments indicate that the mutagenicity of reclaimed water is not found, the contents of harmful chemicals, such as heavy metals and POPs, are rather lower, and the human health risk level of heavy metals is much higher than that of the acceptable level 10-6. Moreover, the heavy metals and pesticide within the fish bred in reclaimed water are lower than the contents limit proposed by the State Food Safe Provision. The total risk of five kinds of heavy metals intake will surpass the acceptable level. In addition, the aerosol chemical method is applied to the study of the health risk of VOCs emitted from the artificial waterfall using reclaimed water, and the mathematical analysis methods, such as: the cluster analysis and principal component analysis are introduced to the risk management of reclaimed water. When reclaimed water is used for the artificial waterfall, the total risk value of VOCs in the air around is obviously increased than that of the background. The non-occupational exposure risk is still lower than the acceptable level of public health risk. While the lifetime risk for occupational workers in the wastewater treatment plant surpasses the acceptable public health risk level (10-5). Based on the risk assessment, this dissertation establishes a risk management system of urban reclaimed water aiming at a sustainable utilization of water resource by integrating the risk management theory. According to the principles of completeness, maneuverability and independence, it sets up an index system of risk assessment of reclaimed water, including the index of health risk, eco-environment risk and wastewater utilization. In addition, it applies the fuzzy mathematics theory to making a comprehensive assessment on the utilizing risk of reclaimed water in the research object, which supplies a foundation for the establishment and development of the risk management system of urban reclaimed water.