综合生命周期环境影响与地区差异的农村污水处理设施适宜性评价

国家十四五规划中明确提出改善农村人居环境，稳步治理农村黑臭水体。农村污水处理是治理农村黑臭水体，提升农村人居环境的主要措施。我国农村污水处理现状不容乐观，污水处理设施选择混乱、闲置率高、造成有限资源、财力和人力的浪费。如何因地制宜选择适宜的农村污水处理设施，目前缺少一套行之有效的判断标准和评价体系。目前针对农村污水处理设施优选评价主要集中在经济效益与生命周期分析，在涉及地形地貌、人口密度、经济发展和环境影响的多目标优化的农村污水处理设施评估研究较少。 本论文针对两种典型的离网式和小集中式农村污水处理设施进行生命周期评价，评估环境影响，核算经济成本。建立以经济成本、环境影响、技术性能和运营管理为约束条件的农村污水处理设施适宜性评价体系。利用AHP-TOPSIS结合的方法，针对以经济发展水平、地形坡度和人口密度差异的全地域农村场景进行农村污水处理设施的优选排序，决策出不同场景下的最优农村污水处理设施。同时针对优选指标权重进行敏感性分析，研究建设投资费用、全球变暖潜势、处理效果和管理难易四个指标权重变化对于排序结果的影响。最后以湖南省为例，计算湖南省县级区域的农村污水处理设施适宜性区域分布。 研究结果表明：两种污水处理设施运营阶段环境影响大于建设阶段，集中式污水处理设施更具有环境友好性，离网式污水处理设施的环境影响总负荷是集中式污水处理设施的3.26倍；人口密度大/经济发展水平高/地形坡度小的区域更适合集中式污水处理，人口密度小/经济发展水平低/地形坡度大的区域更适合离网式污水处理；在人口密度大/经济发展水平低的区域建设投资费用指标权重对于优选结果影响较大，在人口密度大/经济发展水平高的区域全球变暖潜势和处理效果的指标权重对于优选结果影响较大；计算湖南省县级区域的农村污水处理设施适宜性分布，湖南省县级区域中53.4%的地区适宜离网式农村污水处理，36.1%的区域适宜小集中式农村污水处理，6.5%的区域为全城市污水处理。论文研究结果在一定程度上可以解决农村污水治理效率问题，为农村污水治理项目建设的决策者提供参考依据。

In the 14th Five-Year Plan, it is clearly proposed to improve the rural living environment and steadily control the black and odorous water bodies in rural areas. Rural sewage treatment is the main measure to control the black and smelly water body in rural areas and improve the rural living environment. The present situation of rural sewage treatment in China is not optimistic. The selection of sewage treatment facilities is chaotic, and the idle rate is high, resulting in the waste of limited resources, financial resources and manpower. How to choose the appropriate rural sewage treatment facilities according to local conditions is lack of a set of effective criteria and evaluation system. At present, the optimal evaluation of rural sewage treatment facilities mainly focuses on the analysis of economic benefit and life cycle, and there are few researches on the evaluation of rural sewage treatment facilities involving the multi-objective optimization of landform, population density, economic development and environmental impact. In this paper, two types of typical off-grid and small centralized rural sewage treatment facilities are evaluated for their life cycle, environmental impact is evaluated and economic cost is calculated. A suitability evaluation system for rural sewage treatment facilities is established with economic cost, environmental impact, technical performance and operation management as constraints. Using the combined method of AHP-TOPSIS, the rural sewage treatment facilities are selected and sorted according to the different rural scenes with different economic development level, terrain gradient and population density, and the optimal rural sewage treatment facilities are determined under different scenes. At the same time, sensitivity analysis was carried out for the weight of the selected indicators to study the influence of the weight changes of the four indicators, including construction investment cost, global warming potential, treatment effect and management difficulty, on the ranking results. Finally, taking Hunan Province as an example, the regional distribution map of the suitability of rural sewage treatment facilities in Hunan Province was studied. The results show that the environmental impact of the two sewage treatment facilities in the operation stage is greater than that in the construction stage, and the centralized sewage treatment facility is more environmentally friendly. The total environmental impact load of the off-grid sewage treatment facility is 3.26 times that of the centralized sewage treatment facility. The area with high population density/high level of economic development/small terrain slope is more suitable for centralized sewage treatment, while the area with small population density/low level of economic development/large terrain slope is more suitable for off-grid sewage treatment. In the regions with high population density and low level of economic development, the index weights of construction investment cost have a greater influence on the optimization result, while in the regions with high population density and high level of economic development, the index weights of global warming potential and treatment effect have a greater influence on the optimization result. The suitability distribution of rural sewage treatment facilities at the county level in Hunan Province was calculated. In the county level of Hunan Province, 53.4% of the areas are suitable for off-grid rural sewage treatment, 36.1% of the areas are suitable for small-centralized rural sewage treatment, and 6.5% of the areas are suitable for whole-city sewage treatment. The results of this paper can solve the problem of rural sewage treatment efficiency to a certain extent and provide a reference for decision-makers of rural sewage treatment projects.