Comparative life cycle assessment in wastewater treatment plants: scenario analysis with OpenLCA

Although they play a crucial environmental role, wastewater treatment plants (WWTPs) also generate environmental impacts due to resource consumption and waste production. Therefore, the application of the life cycle assessment (LCA) methodology is of fundamental importance for a comprehensive analysis of the impacts associated with these systems. This work aims to perform an LCA of a tertiary-level WWTP, consisting of an anaerobic reactor followed by activated sludge, in order to select the most sustainable scenario. Open Source Life Cycle Assessment (OpenLCA) was the software used, along with the Ecoinvent, BIOENERGIEDAT₁8, ELCD, and NEEDS databases. The reference methods for calculating impact categories were CML-IA and ReCiPe. Three scenarios were simulated: CTBase, CTSolar, and CTReuse. All models considered the operation and maintenance (O&M) phase. The CTBase scenario assumed the WWTP operates as it currently does (electricity from hydropower), the CTSolar scenario operated entirely on solar energy, and the CTReuse scenario established the reusing of 25% of the treated effluent. The functional unit (FU) adopted corresponded to the volume of wastewater treated over 15 years of O&M of the WWTP. For both methods applied, the CTSolar scenario was the most environmentally advantageous. The amount of gases emitted in the CTReuse scenario during the transportation of treated effluent to reuse points increased negative impacts and consequently environmental degradation across various categories, making it the least sustainable scenario.