Are on-site systems environmentally sustainable?

Abstract

Septic systems have a mixed reputation both with the Australian public and regulatory authorities. There is a general belief that they are an outdated and substandard means of on-site wastewater treatment. In this paper we explore the evidence for the sustainability of on-site systems using contamination of surface and groundwaters as primary criteria. Overall we show that despite consistent reports of a high (e.g. =20%) incidence of failing septic trenches, evidence for off-site impacts ranges from sparse to ambiguous at best. To help fill in experimental data gaps we discuss modelling results reported by both ourselves and others, that place contaminant exports (in particular N, P and faecal coliforms) in the context of likely export loads from existing land uses and increasing urbanisation.