Environment Risk Assessment Of Sewage Sludge Application In Agricultural

Agricultural use of sewage sludge is one way of sewage sludge land applications, referring to a sewage sludge disposal way to effectively utilize the sewage sludge after harmless treatment on agricultural lands. During the process of sewage sludge agricultural use, poisonous and harmful substances such as heavy metal, persistent organic pollutant and pathogen in sewage sludge may cause secondary environmental pollution to underground water, soil, and the like, endangering the environmental safety and public health. In order to ensure the environmental safety and realize the safe disposal and cyclic utilization of sewage sludge, it is necessary to carry out environmental risk assessment on the agricultural use of sewage sludge.The works carried out in this thesis are mainly on the following three aspects:1. During the environmental risk identification of agricultural use of sewage sludge, the environmental risk identification field of sewage sludge agricultural use is enlarged for the first time, not only identifying the harmful substances in the sewage sludge, but also including the natural environment factors and social environmental factors during the agricultural use of sewage sludge into the range of risk identification. Detail elaborations on the principle, basis, method and flow of risk identification are presented. Finally, eight evaluation indexes are screened out on three aspects of technical risk, use of risk and management risk to structure a set of comprehensive evaluation index system.2. Facing the versatility and complexity of environmental risk on agricultural use of sewage sludge, the comprehensive evaluation theory is used in this thesis to build the risk assessment model by introducing the theory and method of project risk management. In addition, the Analytic Hierarchy Process is used to identify the index weight and the method of voting by experts is adopted to identify the membership of evaluation index to evaluation set. Finally, the risk level of evaluation objective is calculated by comprehensive calculation of index weight and evaluation matrix. The comprehensive evaluation method, on the basis of limited references, realizes the fully use of experts’experience and opinions, and solves the problems of insufficient quantitative data as well as the versatility and complexity of risk factors.3. This thesis, taking the county region the author staying in as the case study, makes evaluations on the environmental risk of agricultural use of sewage sludge within the study region and discusses the evaluation results by utilizing the foregoing structured risk evaluation index system and evaluation model and referring the regional background information. Moreover, it also makes detail analysis on evaluation results and point outs the factors of key control and countermeasures should be taken.The risk evaluation index system and risk assessment model built in this thesis can provide reference for environmental risk management research and practice on agricultural use of sewage sludge, provide ideas and methods for risk managers and policy makers to formulate environmental risk management measures on local conditions, and ultimately makes a positive contribution to promoting the coordination between economic and environmental benefits of agricultural use of sewage sludge.