Street sweepings are loaded into a reception hopper and fed by conveyor to a heavy-duty machine, called the AggMax. This separates bits of stone from soil and contaminants.
Water is added to wash the waste in the AggMax. Organic material and any other lightweight wastes are removed from the surface water, and are then screened, dewatered and transported to a bay for composting.
Large particles of the washed aggregate (greater than 6mm) are dewatered and deposited in a bunker. This aggregate can be reused in road building or mixed with salt and used for gritting roads.
Remaining material (less than 6mm) is collected and pumped to a variable-concentration hydrocyclone, which separates sand from finer silt.
The sand is discharged onto a dewatering screen and then to a sand bunker. This sand can be used in the manufacture of concrete, as pipe-bedding material by utilities, or in other projects.
The silt (measuring less than 75 micron) passes directly into an AquaCycle thickener. When mixed with a small volume of chemical flocculants and coagulants, the fine silt particles stick together.
Then in the AquaCycle tank, this material rapidly coagulates, producing a thick sludge that settles at the bottom.
Process water overflows the top of the tank to a recycled water storage tank for re-use within the system.
The sludge is then pressed to a produce a filter cake. A clay-type material, this is rich in nutrients and can be blended with soils in land remediation projects.