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

## TL;DR

This study evaluated a residential system that recycles rainwater and greywater, showing it can save up to 51% of potable water and maintain good water quality even during dry seasons.

## Contribution

The study demonstrates the feasibility of integrated rainwater and greywater recycling in reducing potable water use and maintaining water quality over long periods.

## Key findings

- The system achieved average potable water savings of 41% over 16 months.
- Water quality parameters met reuse standards with turbidity below 5 NTU and no thermotolerant coliforms.
- The system remained operational for six months without rainfall, showing high resilience.

## Abstract

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.