Multiplier benefits of integrating household-scale water-efficient sanitation technologies with centralized water resource-recovery facilities

Here, we demonstrate using mechanistic process modeling that integrating household-scale water-efficient sanitation technologies (WEST), especially household reinvented toilets (HRT), which process either just black water (b-HRT) or both gray- and black water (gb-HRT), with existing sewered water resource recovery facilities (WRRFs), unlocks substantial and synergistic reductions in energy consumption and operating costs. The primary mechanism of achieving such benefits is the redistribution of influent organic and nutrient loads, which directly lowers operational energy demands. Further system optimization significantly improves both energy and monetary savings across all WEST-WRRF combinations and coverage levels. Our findings reveal a systems-level opportunity to reconfigure sanitation infrastructure for resilience, circularity, and equity, not by expanding centralized treatment but by mobilizing household interventions as infrastructural leverage points in the global sanitation-energy nexus.