Removal of pollutants by tomato plants during reuse of laundry greywater for irrigation

Abstract

Laundry greywater is considered as a valuable, reusable water resource for irrigation of household gardens and amenity areas around the world. Public health risks arising from exposure to greywater during irrigation are relatively low compared with other wastewater, but long term use of laundry greywater may lead to accumulation of sodium and surfactants in soil affecting crop productivity and environmental sustainability. In this work, we compared growth, biomass and uptake of several essential nutrients and sodium for a tomato crop using tap water and laundry greywater. Observations and measurements of growth over a period of nine weeks and sixteen irrigation events indicated no adverse effects of greywater over tap water on growth. Salts and surfactants in greywater had modest influence over soil water retention and evapotranspiration. Final destructive measurements of plants at flowering indicated similar or significantly higher accumulation of biomass for greywater than tap water irrigated plants. The concentration of P and Na in greywater irrigated plants were 1.4-1.8 times the concentration of tap water irrigated plants. Per cent increase in uptake of P, Na and Fe by greywater over tap water irrigated tomato was 46, 83 and 86, respectively. Since accumulation of sodium in soils from disposal of greywater can be environmentally hazardous, efficient removal of sodium by tomato with reuse of greywater in this study illustrate that plants tolerant to greywater irrigation can reduce soil pollution arising from accumulation of sodium.