STREAMS: An open-source screening life cycle assessment tool for UASB-based wastewater treatment — Inventory development and case-study application in a tropical setting

Wastewater treatment plants consume energy and emit greenhouse gases, and in tropical and subtropical regions, where upflow anaerobic sludge blanket (UASB) reactors prevail, the destination given to the biogas largely determines the climate burden. The environmental performance of UASB reactors coupled with trickling filters (TF), vertical-flow constructed wetlands (VF-CW) or polishing ponds (PP) has not been compared through a single transparent inventory. This study delivers a gate-to-gate operational life cycle inventory for these configurations and their by-product routes; STREAMS, an open-source web application built on that inventory; and a case study of ten operational scenarios at a full-scale WWTP in Campo Grande, Brazil. Impacts were assessed across seven categories using ReCiPe 2016 Midpoint (H) with Ecoinvent 3.9.1 in the Brazilian regionalization. Data quality was scored with the pedigree matrix and propagated through Monte Carlo iterations under dependent sampling. Replacing the open flare with enclosed combustion and energy recovery reduced global warming by 56% to 92%, although no scenario reached a net credit once the gas engine conversion efficiency was applied. A trickling filter raised global warming by a factor of 1.6, whereas a VF-CW reduced freshwater eutrophication by 55% at thirteen times the land requirement. No configuration performed best in every impact category: UASB with VF-CW and an enclosed flare is indicated where phosphorus discharge governs, and UASB-only with an enclosed flare where climate mitigation governs. The inventory and the source code are open, so utilities can repeat the comparison with local data.