Raw incinerator bottom ash is fed to a wet operated jig or wet screen classifier, which separates the fines fraction (- 2mm) as a slurry. The fine incinerator bottom ash fraction, containing most of the precious metals is then transferred to the fine slag treatment plant (FSTP). In the first step the slurry is processed through low-intensity magnetic separation to remove fine iron. This step allows for the production of a saleable Fe concentrate for special smelting applications. The non-magnetic slurry proceeds to gravity concentration in a low and high gravitational field in series, whereas the low-G stage targets the recovery of fine copper and the high-G stage targets precious metal recovery.

Three separate concentrates are produced and dewatered in bags. These concentrates are either sold directly to smelters or processed through a subsequent cleaning step. The reject stream is dewatered and can be landfilled with minimized remaining metals content.