Technical implications of light greywater production and quality for decentralized treatment and reuse: A case study in Bucaramanga, Colombia.

Decentralized light greywater (LGW) treatment and reuse can help mitigate urban water scarcity, yet data on its characteristics at the household level in Latin America remain scarce, limiting system design and implementation. This study assessed LGW quantity and quality in a representative household in Bucaramanga, Colombia, and analyzed its implications for decentralized treatment and reuse. Potable water consumption and LGW production from showers and hand basins were monitored over 98 and 124 days, respectively, with 27 LGW samples collected for quality analysis. Results showed that LGW production was 33.83 ± 4.10 (L/person)/day, accounting for 21% of household potable water consumption, with no significant differences across days of the week. Showers contributed 94% of LGW, while hand basins accounted for 6%. The volume of LGW was sufficient to meet toilet flushing demands (10% of potable water consumption) and could also support other accepted uses, such as floor cleaning and garden irrigation. LGW quality exhibited high variability, low nutrient content (6.37 ± 1.84 mgN/L and 0.74 ± 0.33 mgP/L), high organic matter concentrations (COD: 879.68 ± 163.51 mg/L; BOD: 387.92 ± 92.08 mg/L), and fluctuating fecal coliform levels (1.87 × 10 ± 4.03 × 10 CFU/100 mL), influenced by personal care product use and hygiene practices. Effective treatment systems must accommodate water quality fluctuations and incorporate processes to remove suspended solids, turbidity, dissolved organic matter, oil and grease, and pathogens. This study identified three key technical implications of LGW production and quality for household-level treatment and reuse systems in decentralized settings.