Robust PROMETHEE II screening of nutrient recovery technologies for cleaner production in wastewater treatment

Wastewater nutrient recovery can support cleaner production by reducing dependence on primary fertilisers, but early-stage technology shortlisting remains difficult when evidence is drawn from heterogeneous studies and stakeholder priorities differ. This study develops a PROMETHEE II screening framework for seven pilot-to-near-market nutrient recovery configurations in wastewater treatment plants, covering air stripping, chemical precipitation, ion exchange with regeneration, and electrochemical systems. The alternatives are compared using a compact first-stage criterion set: total cost, potential climate-substitution benefit, and recovery efficiency, all expressed per unit of nutrient recovered. Ranking stability is examined across 405 PROMETHEE II runs combining three preference-function scenarios, five stakeholder weighting profiles, and 27 threshold combinations. The results do not identify a universally superior technology, but rather robust candidates within the assessed dataset, retained criteria, and modelling assumptions. Electrochemical struvite recovery is the most stable high-performing option, remaining in the Top-3 in all runs and ranking first in 65.2%, with 90% recovery efficiency and 3.30 kg CO 2 e avoided per kg nutrient. Air stripping on digestate ranks first in 34.8% of runs and represents the strongest cost-oriented candidate, with the lowest unit cost (€1.78 kg −1 ) and 90% efficiency, provided that concentrated digestate streams are available. The framework converts heterogeneous techno-economic evidence into reproducible early-stage shortlisting evidence, while final implementation requires site-specific techno-economic, regulatory, agronomic, operational, market, and life-cycle assessment.