Comparative Assessment of Solar Distillation of Graywater with and without Boiling for the Production of Distilled Water

Quispe-Collao M.A.; Chaparro-Montoya E.E.; Gomez-Aguilar Y.D.; Lozano-Marreros J.; Cahuapaza-Morales A.; Muñante-Carrillo K.A.; Tirado-Rebaza L.U.M.; Vera-Alcázar M.M. · Nature Environment and Pollution Technology (2026) · DOI: 10.46488/nept.2026.v25i02.d1834

Resumen

Water scarcity in dry urban areas has led to increased use of graywater for potential reuse. Among affordable water treatment methods, solar distillation stands out as an appealing option; however, there is limited documentation on its performance with actual effluents and a direct comparison between boiling and non-boiling configurations. In this study, we compared the solar distillation of domestic graywater using two setups: (i) a boiling system, comprising a CK-002 solar cooker connected to a black-painted copper still, copper coil, and condenser, and (ii) a non-boiling system, featuring a single-slope glass-covered solar still. Graywater was collected from five households in Tacna, Peru, with 5-liter batches treated over 11 h on sunny days. The study recorded distillate volume, physicochemical parameters (pH, conductivity, turbidity, nitrates, nitrites, sulfates, BOD₅, and COD), metal concentrations, and microbiological indicators such as fecal coliforms, Escherichia coli, and heterotrophic bacteria. Results indicated that the boiling distillation produced 2,790 mL of distillate, while the non-boiling system yielded 1,725 mL, a statistically significant difference (α = 0.05). Physicochemical analysis showed significant differences only in turbidity, conductivity, and nitrates, with the non-boiling system demonstrating superior removal (>90%). Total metal removal was 98.63% (reducing from 445.03 mg L-1 to 6.06 mg L-1) in the boiling setup and 98.56% (to 6.37 mg L-1) in the non-boiling. Microbiological testing revealed both systems effectively reduced contaminants: fecal coliforms by 99.76%, heterotrophic bacteria by 99.99%, and E. coli by 98.04%. Overall, solar distillation-whether boiling or not-substantially decreases microbiological pathogens and metals. Nonetheless, due to the persistence of certain organic compounds, such as biodegradable organic matter that exceeds Peruvian environmental standards, solar distillation is best used as a barrier step within a treatment chain designed for limited reuse or combined with additional treatments to meet regulatory limits.

Instituciones: Universidad Nacional de San Agustín de Arequipa; Universidad Nacional Jorge Basadre Grohmann; Escuela de Posgrado Newman