Management of salinity and sodicity in a land FILTER system, for treating saline wastewater on a saline-sodic soil

The FILTER (Filtration and Irrigated cropping for Land Treatment and Effluent Reuse) technique was developed to provide a sustainable system for treatment of saline sewage effluent on naturally occurring saline and/or sodic soils. Potentially, it can also be used to ameliorate soils that are salinised by inappropriate application of saline effluent on soils with impeded drainage. The FILTER technique involves using the nutrient-rich effluent for irrigated cropping combined with removal of excess water from the root-zone through a subsurface drainage system, during wet weather and winter periods when evapotranspiration demand is low. This paper describes the changes in salinity and sodicity in FILTER plots used for land application of saline sewage effluent on a heavy clay soil with restricted drainage, at the Griffith City Council sewage works site. The field experiments consist of trials conducted on four 1-ha plots, over an 18-month period. The pre-FILTER soil chemical characteristics and their changes with FILTER operations were measured. In addition, the volumes and the chemical properties of the effluent applied and subsurface drainage water passing through the soil were monitored. These data are used to explain the salinity and sodicity changes within the FILTER soils, and their potential effects on soil stability. Management options to minimise salinity and sodicity to provide a sustainable system are suggested. Additional keywords: wastewater treatment, SAR, ESP, soil hydraulic properties, controlled subsurface drainage.
Introduction Conventional systems of land application of wastewater on soils with restricted internal drainage, which occur extensively around urban areas in south-eastern Australia, could lead to soil degradation through waterlogging [...]