Evaluating wastewater treatment infrastructure systems based on UN Sustainable Development Goals and targets

Abstract

A multi-criteria comparison of algal-based and activated sludge-based wastewater infrastructure systems based on 30 process parameters derived from the UN Sustainable Development Goals (SDGs) is presented to assess their environmental, economic, social, and overall sustainability. The classical high-rate algal ponds (HRAP) and an emerging mixotrophic algal system (A-WWT) were selected as algal-based systems; and the conventional activated sludge (CAS) system and the membrane bioreactor (MBR) system, as activated sludge-based systems. Visual PROMETHEE outranking software was adopted to determine the preference scores and ranking of the four systems under twelve distinct scenarios/priorities. The mixotrophic A-WWT emerged as the preferred technology in environmental, economic, and overall sustainability aspects resulting in net positive preference scores (0.40, 0.53, and 0.36, respectively). The MBR system outperformed all the other technologies from the social sustainability perspective due to its lower footprint and better-quality effluent including significant pathogen removal. Even though HRAP was preferred over the CAS system in the context of environmental sustainability (preference scores of −0.22 in HRAP vs −0.27 in CAS), preference scores for them were similar in the context of economic sustainability (−0.33 for HRAP and CAS), and lower from social (−0.14 in CAS vs −0.67 in HRAP) and overall sustainability (−0.22 in CAS vs −0.34 in HRAP) perspectives. Scenario-based assessments indicated that preference ranking is strongly dependent on the decision maker’s priorities. Good agreement between the findings from this study with literature reports adds credence to the validity of the proposed process parameters. Parameters and the method proposed herein could be useful in evaluating wastewater treatment technologies from a sustainability perspective.