Assessment via discriminant analysis of soil suitability for effluent renovation using undisturbed soil columns

The use of onsite wastewater treatment systems for the treatment and dispersal of effluent is common in urban fringe areas which are not serviced by centralised wastewater collection systems. However, due to inappropriate siting and soil characteristics, the inherent failure of these systems, in particular subsurface soil treatment systems, are numerous. In order to ensure that these systems are capable of providing adequate treatment and dispersal of effluent in the long term, it is essential that the soilsʹ ability to both renovate as well as dispose of discharged effluent is adequately assessed. This paper discusses the outcomes of a research study undertaken through the use of undisturbed soil columns to assess the ability of different soil types to treat and dispose of primary treated effluent. Discriminant analysis (DA) was utilised for classification of the various soil types based on their respective physical and chemical characteristics and to identify relative changes in each soil type after an extended period of application of effluent. Ferrosol and Dermosol soils were found to provide the most satisfactory conditions for effluent renovation. Kurosol, Sodosl and Chromosol soils even though were found to provide suitable means for removing effluent pollutants, reductions in the soilsʹ permeability over time indicated that these soils may not be appropriate for long term effluent treatment. Finally, Podosol soils were found to have minimal ability to provide adequate treatment of effluent.