Potential changes in soil properties following irrigation with surfactant-rich greywater

The use of insufficiently treated greywater (GW) for irrigation is becoming increasingly common, a practice mistakenly considered safe. Concentrations of surfactants found in greywater effluents range from 0.7 to 70 mg L⁻¹ and on average are higher than concentrations in raw domestic wastewater. However, there is little information regarding the environmental impact of surfactants. Pollutants such as boron, salt, and faecal coliforms are also commonly found in greywater but are not the focus of this study. The capillary rise in sand that was pre-treated with a laundry detergent solution was lower than that in sand pre-treated with fresh water, and exhibited hydrophobic properties. As with the capillary rise, a flow pattern typical of hydrophobic soil was noted when the imbibition of fresh water into sands pre-treated with laundry detergent solution was tested. It is suggested that surfactant accumulation in the soil due to greywater irrigation can create water-repellent soils, thereby affecting their flow patterns and productivity.