Long-Term Evaluation of Water Quality and Quantity in a Residential Integrated Rainwater and Greywater Recycling System with Simultaneous Storage and Treatment

The present study assessed the operational performance of an integrated rainwater and greywater recycling system (IRGRS) installed in a single-family residence in the town of Rio Verde, central Brazil. The methodology included evaluating both the quantity and quality of water produced by the system over a 16 month monitoring period, with a specific focus on contrasting climatic conditions (well-defined rainy and dry seasons). Operational adjustments were made to the treatment process to improve system performance. The IRGRS integrates rainwater harvesting and greywater pretreatment via a constructed wetland, continuous aeration, cartridge filtration, and ultraviolet disinfection. Water quality parameters remained within national and international reuse standards, with turbidity consistently below 5 NTU, COD under detection limits (<5 mg·L^-1), and thermotolerant coliforms absent. The system achieved average potable water savings of 41% (minimum 28% and maximum 51%), ensuring self-sufficiency even through six consecutive months without rainfall. Operational stability was confirmed, with low maintenance requirements and reliable performance of treatment components. The study challenges the conventional recommendation of daily greywater disposal, showing that treated greywater can maintain microbiological quality and expand reuse potential. Integrating rainwater and greywater into a single reservoir reduced infrastructure footprint and enhanced system resilience, offering a sustainable alternative for water conservation in regions with pronounced wet and dry seasons.