How environmentally significant is water consumption during wastewater treatment? Application of recent developments in LCA to WWT technologies used at 3 contrasted geographical locations

Abstract

Environmental impact assessment models are readily available for the assessment of pollution-related impacts in life cycle assessment (LCA). These models have led to an increased focus on water pollution issues resulting in numerous LCA studies. Recently, there have been significant developments in methods assessing freshwater use. These improvements widen the scope for the assessment of wastewater treatment (WWT) technologies, now allowing us to apprehend, for the first time, a combination of operational (energy and chemicals use), qualitative (environmental pollution) and quantitative (water deprivation) issues in wastewater treatment. This enables us to address the following question: Is water consumption during wastewater treatment environmentally significant compared to other impacts? To answer this question, a standard life cycle inventory (LCI) was performed with a focus on consumptive water uses at plant level, where several WWT technologies were operating, in different climatic conditions. The impacts of water consumption were assessed by integrating regionalized characterization factors for water deprivation within an existing life cycle impact assessment (LCIA) method. Results at the midpoint level, show that water deprivation impacts are highly variable in relation to the chosen WWT technology (water volume used) and of WWTP location (local water scarcity). At the endpoint level, water deprivation impacts on ecosystem quality and on the resource damage categories are significant for WWT technologies with great water uses in water-scarce areas. Therefore, our study shows the consideration of water consumption-related impacts is essential and underlines the need for a greater understanding of the water consumption impacts caused by WWT systems. This knowledge will help water managers better mitigate local water deprivation impacts, especially in selecting WWT technologies suitable for arid and semi-arid areas.

Keywords: Freshwater scarcity; Life cycle assessment; River basin scale; Wastewater treatment; Water consumption; Water stress index.