Environmental performance of a full-scale wastewater treatment plant applying Life Cycle Assessment

Abstract Life Cycle Assessment (LCA) was applied to estimate and analyze the environmental impacts from the construction and operation phases of a full-scale wastewater treatment plant (WWTP) located in the municipality of Lauro de Freitas, Bahia, Brazil. The WWTP process consists of the association of an Upflow Anaerobic Sludge Blanket (UASB) reactor followed by four constructed wetlands (CWL) and a disinfection step. The functional unit was defined as one cubic meter of treated effluent during the useful life of this WWTP (20 years). The LCA was carried out using SimaPro® software and the Centre of Environmental Science (CML) assessment method. The environmental impacts during construction phase were mainly from the wooden forms for concrete and the use of reinforcing steel. During the operation phase, the chlorine used as effluent disinfectant caused the greatest impacts in the abiotic depletion and acidification categories. Macronutrient concentrations present in the treated effluent and the methane generated also caused significant environmental impacts during the WWTP’s useful life. The results obtained highlight the importance of the application of a methodology like LCA to assist in decision-making with regard to the implementation, construction and operation of a WWTP.

摘要：本研究采用生命周期评估（Life Cycle Assessment, LCA）方法，对位于巴西巴伊亚州劳罗迪弗雷塔斯市的一座大型污水处理厂（Wastewater Treatment Plant, WWTP）的建设与运行阶段的环境影响进行估算与分析。该污水处理厂的处理工艺为上流式厌氧污泥床（Upflow Anaerobic Sludge Blanket, UASB）反应器串联四座人工湿地（Constructed Wetlands, CWL）及一道消毒工序。本研究将功能单元定义为该污水处理厂20年服役周期内，每立方米处理后出水。本次生命周期评估采用SimaPro®软件与环境科学中心（Centre of Environmental Science, CML）影响评价方法开展。建设阶段的环境影响主要来源于混凝土木模板与钢筋的使用；运行阶段中，用作出水消毒剂的氯在非生物资源消耗与酸化影响类别中造成了最大的环境负荷。此外，处理出水中的宏营养素浓度以及产生的甲烷，在该污水处理厂的全服役周期内也带来了显著的环境影响。本研究结果凸显了采用生命周期评估这类方法辅助污水处理厂规划、建设与运行相关决策的重要性。