| Wastewater Reuse by Evapotranspiration

In many areas of Western Australia, the soil was extremely impermeable with high clay and silt contents causing applied water to pond on the surface. In such situations conventional septic tank with soil absorption systems frequently failed when effluent moving into the disposal field was not absorbed by the soil quickly enough to prevent its rise to the surface. The only alternative currently used in such situations was a reticulated sewage collection system which was very costly, inevitably consumed vast amounts of water in remote Aboriginal communities and frequently failed due to lack of maintenance.

Evapotranspiration (ET) systems had potential for use in those areas where soil absorption fields failed. The systems cost considerably less and required potentially less maintenance than reticulated systems (McGrath et al., 1991). An ET system disposed of effluent by soil evaporation and plant transpiration rather than soil percolation - as occurred in conventional leach drains. The disposal field essentially comprised a layer of gravel for distribution of effluent below a layer of coarse sand through which capillary action to the surface occured and in which plants grew.