Exposure assessment of treated greywater reused for irrigation

Abstract

The aim of the study was to assess the risk of exposure of treated greywater reused for irrigation. It consisted of untreated and treated greywater quality analysis and heavy metal exposure assessment. After treatment with a local conventional stabilization pond, parameters such as BOD, COD, Zn, and Pb dropped to 35.63, 9.95, 0.011, and 0.001 mg/L, respectively. Total coliform and fecal coliform decreased to 23,417 and 5,666 MPN/100 mL, respectively. These results showed almost all detected contaminants in treated greywater were minimized and did not exceed Thailand’s standard and World Health Organization guidelines. After that, treated greywater was reused for irrigation. There were three vegetable plots: treated greywater, tap water with fertilizer, and tap water. There were seven edible plants, four leafy and three fruiting vegetables, cultivated in each plot. Zn, Pb, Cd, Cu, and Hg were detected depending on the kind of plant; for example, the maximum concentration was found in leafy vegetables. However, the concentrations of contaminants did not exceed the Codex standard for contaminants and toxins in foods and Thailand’s standard. Risk characterization showed no risk with a hazard quotient far less than 1. Therefore, treated greywater reuse could be considered to promote sustainable water management in the community.