Assessment of high density of onsite wastewater treatment systems on a shallow groundwater coastal aquifer using PCA

Onsite wastewater treatment systems are common throughout the world, including Australia, with approximately 17% of the Australian population relying on these systems to treat and ultimately dispose of wastewater. Systems which are properly sited, designed and managed are an effective way of providing the necessary treatment of wastewater. However, incidence of onsite system failure is common, and this is further compounded in areas where high densities of systems are established. The density of systems is not appropriately assessed in the siting and design stage. Various factors, such as site and soil characteristics and climate, can influence the treatment efficiency, and this is more critical in high density areas. Principal component analysis was used for assessing chemical and microbiological data from shallow groundwater below a high density of onsite treatment systems. The results of this study confirmed that high system densities can significantly impact shallow groundwater systems. Additionally, changes in spatial and climatic conditions, as well as the type of onsite system, can also influence the quality of groundwater. Copyright © 2004 John Wiley & Sons, Ltd.