Synergism of Life Cycle Assessment and Sustainable Development Goals Techniques to Evaluate Downflow Hanging Sponge System Treating Low-Carbon Wastewater

Abstract

While recent researchers have focused on optimizing the operational conditions of low-carbon wastewater treatment processes, they have not sufficiently evaluated the sustainability of such systems. This study is the first to assess the performance of a low-carbon wastewater treatment facility using an integration of techno-economic and life cycle assessment (LCA) criteria accompanied by several sustainability indicators. A downflow hanging sponge (DHS) reactor was operated at a hydraulic retention time of 3.4 h, an organic loading rate of 3.8 kg COD/m3 sponge/d, and 24–35 °C (scenario_1). Another two DHSs were operated in parallel, i.e., a 50% influent bypass (scenario_2) and 260 mg/L charcoal addition (scenario_3), providing carbonaceous matter to maintain the nitrification/denitrification pathway. Employing the DHS’s scenario_3 could fulfill most of the SDGs regarding the environmental (e.g., COD and nitrogen removals) and socio-economic (e.g., reliability, labor, and health and safety) targets. The LCA tool also confirmed the superior environmental benefits of scenario_3, concerning effluent quality, GHG emissions, and sludge generation. The synergistic interaction of LCA and SDGs approaches ranked the proposed DHS modifications as scenario_3 > scenario_1 > scenario_2. Hence, the current study provided an innovative strategy that could be employed to assess the sustainability of wastewater treatment systems worldwide.