Analysis of effects of an objective function on environmental and economic performance of a water network system using life cycle assessment and life cycle costing methods

Abstract

Water network synthesis has been used to conserve water resources and reduce economic costs. In this study, all contributors to environmental burdens and economic costs of water network systems were estimated to analyze the effects of objective functions on their environmental and economic performances. A total freshwater flowrate-minimized water network system (FWNS) and a total freshwater cost-minimized water network system (CWNS) were independently synthesized. Life cycle assessment and life cycle costing were performed to evaluate and compare the environmental and economic performances of the two water network systems. The CWNS was more environmentally and economically friendly than the FWNS because the CWNS was synthesized by minimizing the consumption of deionized water, which has higher unit cost and unit environmental effect scores than industrial water. Also this study demonstrated that the consumption rates of freshwater and electricity, as well as their unit environmental effect scores, should be used as principal contributors and weighting factors for the formulation of an objective function to generate the most environmentally friendly water network system, while the costs of piping and freshwater, as well as their unit costs, should be included to generate the most economically friendly system.