LA Graywater Recycling: UCLA Cost-Benefit for Homes

This study from the University of California, Los Angeles, Civil and Environmental Engineering Department conducts a detailed cost-benefit analysis of onsite graywater recycling systems in single-family and multifamily homes, using the City of Los Angeles as a case study in an arid urban region. It evaluates economic drivers for adoption, focusing on water savings, energy reduction, and environmental benefits. Key findings show that graywater recycling reduces potable water demand by 27% in single-family homes (from approximately 3,570 L/day to 970 L/day, displacing 50% of irrigation water) and 38% in multifamily dwellings. At 10% participation citywide, it cuts water supply and treatment energy by 43,000 MWh/year, potable water demand by 2%, and wastewater treatment load by 3%. Even at 1% participation, energy savings reach 4,300 MWh/year. The analysis includes precise metrics on system costs, payback periods, and scalability. For single-family homes, systems handle laundry and shower water diversion, with filtration and treatment to meet reuse standards for irrigation. Multifamily implementations show higher efficiency due to shared infrastructure. Practical details cover installation costs, maintenance, and regulatory considerations in water-scarce areas. The study emphasizes greywater's role in enhancing urban water resilience, with data-driven projections for broader adoption reducing overall municipal water imports and treatment burdens. It provides actionable insights for policymakers and homeowners, including sensitivity analyses on participation rates and water pricing impacts on ROI. Methods involve lifecycle costing, energy audits, and hydraulic modeling, confirming net benefits in high-water-cost regions.