Effect of laundry greywater irrigation on soil properties

Abstract

In this study, surfactant-rich laundry greywater is used to investigate the changes of different soilproperties such as, hydraulic conductivity, pH, Electrical Conductivity (EC) and pressure-saturationrelationship. A series of soil column (composed of several PVC rings) experiments was conducted under unsaturated condition for different greywater concentration. In each experiment, pH, EC andhydraulic conductivity were measured. At the end of each experiment, the column was dismantledand moisture content in each ring was measured gravimetrically and the soil suction in each ring wasmeasured from the reference groundwater table. The breakthrough curves with EC value and themeasured value of pH at the column outlet revealed that the greywater with higher concentrationreach the column outlet faster because of increased hydraulic conductivity. In separate experiments,soil hydraulic conductivity was tested and found steadily increasing with greywater concentration.Pressure saturation curves showed that the capillary rise decreases sharply with greywaterconcentration due to the reduction of surface tension but remain constant after certain concentrationwhich may be referred to the Critical Micelle Concentration (CMC) of surfactants contained in thelaundry detergents.