The flotation circuit consists of three flotation columns running in parallel. The flotation columns are used as roughers with the concentrate produced going to the final concentrate stream. Filtration - Prior to being dispatched to the Gidji Roaster for further treatment, the final concentrate from the flotation circuit must be washed to remove excess salts which have a detrimental effect on the roasting process. The concentrate is stockpiled to await transport to the Roaster. High rate thickeners are an integral part of the process at the Fimiston plant due to the requirement of the various unit processes to have differing pulp densities to work efficiently.
Thickeners also play an important part in the water balance of the plant.
Consumption of water throughout the plant is very high, so every effort must be made to reclaim process water wherever possible. Reclaimed water is used at the Fimiston Mill. The waste slurry from this is then pumped to the tailings dam for disposal. There is, however, a significant amount of recoverable gold remaining in the ore after flotation. The gold tends not to be directly associated with the sulphide minerals in the ore and can therefore be recovered by conventional carbon in leach processing.