Multi-criteria decision analysis of decentralized wastewater technologies

Increasing water scarcity and climate variability are accelerating interest in decentralized water treatment strategies to enhance urban water resilience and support circular economy objectives. However, selecting appropriate technological configurations remains a complex decision-making challenge due to trade-offs among technical, economic, social, and resource recovery criteria. This study develops an integrated Multi-Criteria Decision Analysis (MCDA) framework that combines the Analytic Hierarchy Process (AHP) with the contextualized indicator structure of the Decision-Making for Sanitation and Resource Recovery Systems (DMsan) platform. The framework evaluates five decentralized wastewater treatment configurations: two vacuum-based systems with different anaerobic schemes (V1, V2), two conventional toilet-based systems with aerobic and anaerobic processes (C1, C2), and one source-separation system using urine-diverting toilets (UD). To capture different planning priorities, nine decision scenarios representing alternative policy and implementation contexts are analyzed. The assessment incorporates 21 indicators grouped into 4 criteria. The results reveal three distinct technological suitability profiles. The vacuum-based configuration V2 shows the most balanced performance and ranks highest in scenarios prioritizing operational resilience, social acceptance from a management perspective, and low operating costs. The conventional configuration C2 is preferred in scenarios dominated by financial feasibility and minimized capital investment. In contrast, the source-separation configuration UD outperforms other alternatives when circular economy objectives and maximum nutrient recovery are prioritized. The results demonstrate that technological suitability is strongly context-dependent and highlight the value of multi-scenario MCDA for supporting the planning and design of resilient and circular decentralized urban water systems.