Phosphorus release screening and recovery pathway selection from dairy processing waste activated sludge

This study developed a multi-criteria decision-making framework using weighted scoring analysis (WSA) to compare phosphorus recovery pathways from dairy processing waste activated sludge (WAS). Four phosphorus-release technologies were screened experimentally, while the downstream performance of struvite, vivianite, and apatite recovery was evaluated using literature-derived data. Integrating technical, operational, economic, and socio-environmental criteria weighted by an international expert survey, anaerobic digestion (AD) combined with struvite crystallisation was the highest-ranked pathway. Among the release conditions tested, anaerobic digestion produced the highest release of 0.45 µm-filterable phosphorus (∼48% efficiency). While struvite recovery is the operational benchmark, vivianite recovery offers economic potential due to its high value in the battery industry. Sensitivity analysis underscores the robustness of the anaerobic digestion and struvite crystallisation configuration, particularly under socio-environmental and operational priorities. The results suggest that under the adopted framework, AD-based pathways may provide a more balanced basis for phosphorus recovery than the hydrothermal alternatives considered.