Reuse of Laundry Greywater in Irrigation: Potential Changes in Soil Parameters

Abstract

Laundry greywater is potentially surfactant-rich and thus have significant impact on soil hydrologic properties. This study investigates the potential changes of soil hydrologic parameters following irrigation of laundry greywater in two types of soils. The soil parameters investigated include hydraulic conductivity, pH, electrical conductivity (EC), porosity, bulk density and capillary pressure-saturation relationship. A soil column composed of several PVC rings was used for greywater irrigation. The experiments were conducted under unsaturated condition for different synthetic greywater concentration. In each experiment, pH, EC, hydraulic conductivity, soil porosity and bulk density were measured. At the end of each experiment, the column was dismantled and moisture content in each ring was measured gravimetrically and the soil suction in each ring was taken as the distance from the reference groundwater table. The breakthrough curves with EC and pH measured at the column outlet revealed that the greywater with higher concentration reach the column outlet faster because of increased hydraulic conductivity. The soil hydraulic conductivity was found steadily increasing with greywater concentration for both soils. Pressure saturation curves showed that the capillary rise decreases with greywater concentration due to the reduction of surface tension. However, the residual water content in soil B was found higher than soil A following greywater irrigation.