Life Cycle Environmental Assessment Of Urban Drainage System

Given internationally wide problems of global warming, local flooding and environmental pollution getting worse and worse, it is an efficient way to cope with the challenge of sustainable development by exploring new urban drainage system and stormwater management concept and building measurable assessment methods. Present researches on Life Cycle Assessment(LCA) mostly focused on wastewater treatment plant, but little attention is given to the life cycle environmental impact of drainage systems. Life Cycle Assessment of urban drainage system can identify the environmental influence and key factors in different stages of life cycle and compare different kinds of urban drainage system, and can provide a measurable theoretical basement for decision makers and environmental policy makers.Based on the framework of Life Cycle Assessment, this thesis determined the system boundary of urban drainage system’s Life Cycle Assessment, which includes the obtaining and production of raw materials, construction, running and tearing down of drainage collection and transport system and wastewater treatment plant. Inventories of urban drainage system are presented from three aspects—resources, energy consuming and sewage drainage. With the analysis program of Life Cycle Assessment—Sima Pro8.0, and Impact Assessment—CML-IA baseline, choosing the domestic database of China CI and foreign database of Ecoinvent3.0, the inventory lists of urban drainage system are established and calculated based on three aspects—resources, energy consuming and sewage drainage. And then the results of assessment are analyzed and explained in integrity, contribution and sensitivity.The southwestern part of Yuelai eco-city is selected for case study. Through analysis, three systems, namely intercepted combination drainage system with sewage overflow treatment, separated drainage system with interception and LID completely separated drainage system, which are thought to be efficient in controlling urban non-point pollution and the main drainage system in the near future, are selected for assessment. The three systems for the case area were designed, respectively. And then the civil works, materials and so on were calculated and counted. Together with other data, the inventory lists were built and integrated with existing wastewater treatment plant life cycle impact assessment models. By applying Sima Pro software, the life cycle environmental impact for the three drainage systems were made.The results indicate that the intercepted combination drainage system with sewage overflow treatment has the biggest impact and the LID completely separated drainage system has the smallest impact in all of the nine assessment indicators(abiotic depletion, abiotic depletion-fossil fuels, global warming, ozone depletion, human toxicity, fresh water aquatic ecotoxicity, marine aquatic ecotoxicity, terrestrial ecotoxicity, eutrophication). For urban drainage system, Marine aquatic eco-toxicity is the predominant factor. In the stage of running in wastewater treatment plant, chemical and electrical energy consuming are racial in affecting environment. Construction and running are the two main stages of impacting environment for urban drainage collection and transport system. Chinese background database decide the accuracy of evaluation results, and it is necessary to improve local database in China.The research results can be a reference for urban drainage system selection and policy making.