Evaluating the long term behaviour of soils under effluent dispersal using soil columns

Abstract

Soils only have a finite capacity for the removal of wastewater pollutants and with time this capacity could in fact decline. Once this capacity is exceeded or there is neglect of subsurface conditions, excessive transmission of pollutant loads to the natural environment is inevitable resulting in environmental and public health impacts. Not all soil types have the capacity to provide adequate treatment and dispersal of sewage effluent. The ability of the soil medium to remove pollutants and transmit effluent is one of soils’ more important characteristics and one which a successful on-site sewage treatment system is significantly dependent. For continued long term application to be successful it is essential that infiltration and drainage characteristics of soils do not decline. Also critical is how the long term application of nutrients and cations has affected the soils and whether any leaching of these occur. This paper compares the outcomes of detailed field studies with physico-chemical data collected from a continuing long term undisturbed soil column study where typical soils of South East Queensland have been subjected to sewage effluent application over a period of 2 years to determine whether prediction of long term behaviour of sub-tropical soils is achievable.