THE USE OF BAUXITE RESIDUE TO CONTROL DIFFUSE PHOSPHORUS POLLUTION IN WESTERN AUSTRALIA — A WIN–WIN–WIN OUTCOME

The Department of Agriculture, Western Australia has been working with Alcoa World Alumina Australia Ltd for more than ten years investigating the potential to use bauxite residues as soil amendments for the poor, acidic, sandy soils of the Swan Coastal Plain.

Regional waterways, especially the Peel Inlet and Harvey Estuary, have historically been susceptible to nuisance algal blooms fed by phosphorus in run-off from farmland and urban areas. While the incidence of algal blooms has recently been substantially reduced in the estuary system by the construction of a new channel to the Indian Ocean known as the Dawesville Channel, the main feeder river systems are now experiencing substantial algal blooms. The major mechanism for the reduced algal growth in the estuary is an increase in the salinity of the water body and, to a lesser extent, the flushing of phosphorus into the Indian Ocean. These mechanisms have limited effect in the rivers away from the influence of the new channel. While the incidence of nuisance algal blooms in the estuary has declined, this approach has not reduced the amount of nutrients flowing through the catchment and entering the waterways.

Extensive laboratory, field and catchment-scale trials have repeatedly shown the ability of soil amendment with fine bauxite residue (now trademarked in this context as Alkaloam) to reduce the leaching of nutrients to sensitive regional waterways by up to 75%, while at the same time, increasing pasture productivity by up to 25% (up to 200% in well-controlled experimental situations). This is now widely acknowledged as the only land management option developed globally which has been shown to reduce non-point-source phosphorus export immediately upon application. Alkaloam is now available on a commercial basis to landholders in the Peel-Harvey Catchment and is seen as an exciting solution to a significant land degradation problem. This paper examines the effectiveness of Alkaloam in retaining phosphorus, increasing plant production and assisting in minimising waste production from refineries — win–win–win.

The project has previously won a State Landcare Award and was a finalist in the National Landcare Awards. It has also recently been recognised by a Department of Agriculture Technical Excellence and Innovation Award and was a finalist in the 2001 WA Premier’s Awards for excellence in Public Sector Management.