Reuse of Domestic Greywater for the Irrigation of Food Crops

As global water resources decline, reuse of domestic greywater for the irrigation of home gardens is quickly becoming widespread in many parts of the world. However, the sanitary implications of reusing greywater to water edible crops remain uncertain. This study examined the benefits and risks associated with domestic greywater reuse for the purposes of vegetable garden irrigation. Untreated (settled only) and treated (settling and slow sand filtration) greywater collected from a family home was analyzed for basic water quality parameters over a period of 8 weeks. During that time, both greywaters were used to irrigate individually potted plots of lettuce, carrots, and peppers in a greenhouse. Tap water was used as control. Upon maturity, plants were harvested and the edible portions tested for fecal coliforms and fecal streptococci, common indicators for the presence of pathogenic microorganisms. Heavy metals were not detected in the greywater, but both fecal coliforms and fecal streptococci were present in high levels, averaging 4 × 105/100 mL and 2,000/100 mL of greywater, respectively. Despite these high counts, no significant difference in contamination levels was observed between crops irrigated with tap water, untreated greywater, and treated greywater. Fecal coliform levels were highest in carrots and fecal streptococcus levels were highest on lettuce leaves. However, contamination levels for all crops were low and do not represent a significant health risk. Plant growth and productivity were unaffected by water quality, owing to the low N, P, and K levels of the greywater. These results reinforce the potential of domestic greywater as an alternative irrigation source.

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