Life cycle assessment case study: Tertiary treatment process options for wastewater reuse

ABSTRACT Tertiary treatment process (including filtration and/or disinfection) is necessary to obtain a water quality suited for high‐quality reuse from wastewater treatment. Industrial pilots representing small real‐size treatment units were set up downstream of a conventional secondary treatment of a wastewater treatment plant in the South of France and their performance followed for 2 y. Life cycle assessment (LCA) methodology is used to compare the environmental impacts of different treatment processes. Five tertiary treatment trains were studied: 1) sand filtration (SF) + storage followed by ultraviolet (UV) dynamic reactor disinfection (SF‐UVD), 2) sand filtration + UV batch reactor disinfection (SF‐UVB), 3) ultrafiltration (UF), 4) ultrafiltration and UV batch reactor disinfection (UF‐UVB), and 5) microfiltration (MF) and storage followed by dynamic UV disinfection (MF‐UVD). The chosen functional unit is “To supply 1 m3 of water with a quality in compliance with the highest standard of the French reuse regulations.” The combination of SF with UV disinfection or the use of UF alone was found to be equivalent in terms of environmental impact for most of the midpoint indicators chosen. Combination of UF with UV disinfection was significantly more impacting because the electricity consumption was nearly doubled. This study was conducted on an industrial pilot; it may thus be representative of industrial facilities implemented to treat higher water flows. Integr Environ Assess Manag 2017;13:1113–1121. © 2017 SETAC Key Points Life cycle assessment (LCA) was used as a decision‐support tool to determine the best treatment process option for wastewater reuse. The combination of sand filtration with UV disinfection (SF‐UVD and SF‐UVB) or the use of only ultrafiltration (UF) was found to be equivalent in terms of environmental impact for most of the midpoint indicators chosen. The operation phase is the major contributor to the environmental impacts, mainly due to the origin of the electricity required.