Abstract

This study investigates the relationship between bacterial communities and water quality parameters in commercial laundry greywater (GW), aiming to support its potential for urban reuse. Two laundries using different detergents were compared: Laundry A used conventional powder detergent, while Laundry B employed an ecological alternative free of phosphates and sulfates. Water samples were analyzed using a combination of physicochemical characterization, high-throughput DNA sequencing, and statistical methods. Results revealed that Laundry B exhibited chemical oxygen demand (COD) and turbidity levels 4.0 and 3.0 times higher than Laundry A, respectively. In contrast, concentrations of phosphate, sulfate, and ammonium in Laundry A were 27, 8, and 69 times higher than in Laundry B, indicating the impact of detergent composition on water quality. Both GW sources exceeded reuse guidelines for turbidity and fecal coliforms, indicating the need for treatment before urban application. Bacterial community composition also differed. Aeromonas and Pseudomonas predominated in Laundry A (> 40 %), while Citrobacter and Rabinella were prevalent in Laundry B (>37 %). Alpha diversity (Chao 1 index) was 56 % higher in Laundry B, suggesting that detergent type plays a key role in shaping microbial communities. This study is among the first to link detergent composition with pollutant concentrations and microbial profiles in commercial laundry GW, offering new insights into treatment solutions. A sequential system combining green roofs or filtration with disinfection is recommended for safe urban GW reuse.