Selection of sewage treatment systems based on Multicriteria Analysis - Evaluation of different preference structures

ABSTRACT The main perspective of this work is the selection of sewage treatment systems for the Pardo river hydrographic basin, a watercourse located in the southern region of the state of Espírito Santo, Brazil, by using a Multicriteria Analysis, considering two different preference structures. Minimum Biochemical Oxygen Demand removal efficiencies were used as pre-selection criteria. The treatment systems hierarchy involved a set of environmental, technological, operational and social criteria. To conduct the Multicriteria Analysis, the ELECTRE II method was used. The results indicated that the imposition of standards for effluents led to the selection of activated sludge treatment systems variations, mainly for denser population centers. The incorporation of the watercourses self-purification capacities reduced the treatment effort within the basin, leading, for different urban centers, to the selection of stabilization ponds or Upflow Anaerobic Sludge Blanket reactors treatment systems variations. The preference structures analyzed, however, led to the selection of different treatment systems for different urban centers and sewage discharge conditions, with more pronounced variations for localities presenting smaller populations.摘要 本研究的核心视角为：采用多准则分析（Multicriteria Analysis）方法，结合两种不同偏好结构，为位于巴西圣埃斯皮里图州南部的帕尔杜河（Pardo river）水文流域遴选污水处理系统。本研究以最低生化需氧量（Biochemical Oxygen Demand，BOD）去除率作为预筛选准则，污水处理系统的评价层级涵盖环境、技术、运维及社会等多维度准则，本次多准则分析采用ELECTRE II方法开展。研究结果表明，落实污水排放标准要求后，适配人口密集城镇的最优方案为活性污泥（activated sludge）处理系统变体；纳入河流水体自净化能力后，流域内整体处理负荷得以降低，针对不同城镇中心，可选用稳定塘（stabilization ponds）或上流式厌氧污泥床（Upflow Anaerobic Sludge Blanket，UASB）反应器处理系统变体。不过，本次分析所采用的两种偏好结构，会根据不同城镇中心与污水排放条件遴选差异化处理系统，在人口规模较小的区域，方案差异更为显著。