Degree Name

Doctor of Philosophy


Department of Civil and Mining Engineering


Most small rural and remote Aboriginal communities in Australia rely on conventional septic tank systems (CSTS) for on-site wastewater treatment and disposal. The operational conditions of these systems are often not investigated for cHmate, performance and user suitability. Also, little or no consideration is given to soil conditions, flow fluctuations, and shock loadings in their design. This work was aimed at investigating the performance of the existing CSTS and if required, develop new waste disposal systems for Aboriginal communities. To evaluate the performance of CSTS installed in remote and/or rural Aboriginal communities, it was necessary to obtain raw data on the flow patterns, site conditions, system design, local codes and wastewater quantity and quality from source to disposal. The Pipalyatjara community in South Australia was selected for this investigation. This community is located in a long narrow valley of the Tomkinson Ranges about 750 km south west of Alice Springs. The research work was carried out in three phases. Phase 1. As there was no data available on wastewater characteristics in remote Aboriginal communities, the initial focus was on field data collection and evaluation of existing CSTS performance and this was carried out from November 1995 to May 1996. Three systems were chosen for continuous data collection and another three were allocated as stand-by units to overcome vacant occupancy in one or more of the monitored households due to high mobility of people within and between Aboriginal communities. An on-site fully functional new water quality laboratory was established in the Pipalyatjara conmiunity. Soil percolation and permeability tests were conducted to assess site conditions, and continuous flow measurements were recorded to estimate water consumption and wastewater flow rates. Grab and composite wastewater/water samples were collected every four hours and analysed for various water quality parameters. Grey and black waters were monitored separately. The existing CSTS appeared to be undersized (tank and disposal area) as indicated by occasional high household population which resulted in high hydraulic (2-5 times what is encountered in urban areas) and organic loading (2 - 3 times the typical urban values) of the soakage trenches. This in turn led to an observed increase of wastewater ponding in the soakage trenches. Further it has been found that the grey water generation rate is 92% of the wastewater flow which is significantly different from typical urban value of 70%. m