An expert-based AHP decision framework for prioritizing greywater reuse integration criteria in sustainable urban development

This study develops a decision-support framework for integrating greywater reuse into sustainable urban environments using the Analytical Hierarchy Process (AHP). The study prioritizes multi-scale criteria that influence greywater system implementation and translates them into a practical planning tool. A structured literature review identifies four main criterion groups (urban, infrastructure, environmental, and architectural) and twenty-three sub-criteria. The study analyzes expert judgments from a panel of sixteen specialists through AHP pairwise comparisons, eigenvector weighting, and consistency validation. The results demonstrate that infrastructure is the most significant criterion (0.4125), followed by urban factors (0.3526), with environmental and architectural dimensions ranking lower. At the sub-criteria level, ventilation and permeability, infrastructure resilience, and sub-surface irrigation networks are identified as the most influential variables. These priorities form a multi-scale operational framework structured around urban baseline assessment, smart infrastructure integration, and building-scale ecological execution. An evidence-qualified benchmarking using four international case studies demonstrates the framework's capacity to distinguish between spatial readiness and operational implementation capability. The findings indicate that district-scale infrastructure and urban morphology, rather than building-level design alone, primarily determine greywater system performance. A principal limitation is the reliance on expert-based judgments, which may require further validation through real-world monitoring and broader geographic sampling.