Comparative Analysis of Integrated Treatment Trains for Residential Light Graywater Reclamation

ABSTRACT Water scarcity driven by climate change and urbanization has intensified interest in decentralized water reuse systems, particularly for residential light graywater (LGW). However, treatment performance data remain scarce, limiting policy development in Colombia. This study compares two integrated bench‐scale graywater treatment trains (GWTT) for LGW reclamation using a synthetic mixture of personal care products and secondary effluent to mimic household contaminants. GWTT1 combined sedimentation, slow sand filtration, ultrafiltration membrane, and ultraviolet disinfection, whereas GWTT2 integrated sedimentation, ozonation, granular activated carbon (GAC) filtration, and UV disinfection. GWTT2 achieved higher organic removal, with 99.6% turbidity and 78% chemical oxygen demand reduction, compared with 95.9% and 71.9%, respectively, for GWTT1. Linear regression indicated that GAC‐to‐biologically activated carbon maturation in GWTT2 (slope of 2.64 percentage points per sampling event, R 2 = 0.74) enabled passive performance gains without operational intervention. Despite a 7% increase in heterotrophic bacteria from GWTT2 biofilm detachment, GWTT1 provided more consistent microbiological control, reducing total coliforms by 91% and E. coli by 96%. These findings support the development of residential water reuse regulations in Colombia by addressing gaps in Resolution 1256 of 2021 and identifying operational trade‐offs for decentralized implementation.