Hydraulic conductivity response of soils to synthetic laundry greywater

Abstract

Laundry greywater is an important water resource that may be used for irrigation of residential lawns and gardens. The extent of reuse of this resource is dependent on the hydraulic properties of soil. This project was undertaken with the aim to experimentally determine the extent to which soil properties and the properties of laundry greywater (e.g. pH, EC and ion composition) influence saturated hydraulic conductivity using three soil types sourced from Toowoomba, Bundaberg and Surat regions of Queensland, and synthetic greywater made from powder and liquid laundry detergents (PLD and LLD). To determine how hydraulic conductivity of these soils is affected when exposed to laundry greywater, simultaneous comparison was made using tap water (TW). For all experimental work, three replicated soil cores of the three types of soils were exposed to three types of water (TW, PLD and LLD). Additional measurements included evaluation of suspended colloids and ions in the leachate collected during hydraulic conductivity measurements. Results show that hydraulic conductivity of all soils relating to this experiment are lowered substantially. Results show that hydraulic conductivity is lowered substantially when the soil cores are irrigated with either of the two laundry detergents, particularly with the powder laundry detergent. A reduction in hydraulic conductivity of up to 98% resulted from the irrigation of soil cores with the synthetic greywater. The threat of contamination of groundwater is reduced due to the filtering and purification of the greywater during drainage. This process removed harmful salts and sodium from the irrigation water. However these will accumulate with sustained irrigation and lead to poor soil quality due to dispersion and salinity. Direct reuse of synthetic laundry greywater is not sustainable on these types of soils