Assessment of Environmental and Public Health Risk of On-site Wastewater Treatment Systems

On-site wastewater treatment systems are common throughout Australia, with most systems located in the urban fringe and rural regions. The number of on-site treatment systems is increasing rapidly as these areas undergo more intensive development. Consequently, there is a significant increase in environmental and public health risks associated with these systems. This has lead to the recognition of the need for the articulation of treatment standards and criteria which are flexible and robust to satisfy specific public health and environmental requirements. Currently, these concepts are not being widely applied in on-site treatment of wastewater. A research project was undertaken to identify and assess the environmental and public health risks associated with on-site wastewater treatment systems in an area within the Gold Coast region, Southeast Queensland, Australia. A detailed surface and groundwater investigation including nutrient and microbiological analysis and modeling studies were undertaken to identify and assess the risk of contamination from nutrients and pathogenic organisms discharged from on-site systems. This also included the assessment of the potential risks in relation to high densities of on-site systems. High levels of nutrients, in particular nitrate, has been found in an unconfined shallow aquifer within the study area, directly below high densities of systems. Similarly, high fecal coliforms have also been observed in various locations throughout the area. Therefore, it crucial that the impact of high densities of on-site systems on shallow groundwater is appropriately assessed in order to minimise the potential risks to the environment