Performance Evaluation and Reuse Potential of an On-Site Residential Greywater Treatment System for Sustainable Urban Water Management

Rapid urbanization has intensified the imbalance between water demand and freshwater availability, emphasizing the need for decentralized and sustainable water reuse solutions. This study evaluates the performance and reuse potential of an on-site residential greywater treatment system designed for sustainable urban water management. The treatment process consisted of initial settling followed by dual-stage multimedia filtration using two filter storage units (FSU-I and FSU-II). The filtration media comprised sand, activated carbon, zeolite, fine gravel, and coarse gravel, operated under six experimental phases at hydraulic loading rates of 14.00 and 24.00 m³/m²/day. Sodium hypochlorite (NaOCl) was applied as a final disinfection step prior to reuse. The system demonstrated high treatment efficiency, achieving average removal efficiencies of 95.65 ± 1.95% for turbidity, 82.34 ± 5.84% for biochemical oxygen demand (BOD₅), 96.78 ± 1.87% for total suspended solids (TSS), 76.35 ± 4.11% for chemical oxygen demand (CODₜ), and 98.69% for Escherichia coli . The treated effluent met reuse standards for non-potable applications such as landscaping, peri-urban agriculture, construction activities, city cleaning, and recreational uses. Implementation of the system resulted in an estimated 65% reduction in daily freshwater consumption, corresponding to an approximate 39.69% decrease in residential water expenditure. Overall, the findings demonstrate that decentralized residential greywater treatment systems can significantly enhance urban water sustainability and support smart city water infrastructure.