MEI Chart - Toot Toot the 150,000ppm cobalt train, page-145

My friend, arsenic and sulfides exist in practically every hydrothermal precious metal deposit around the world. There's a wide range of ways to deal with it beyond what they used to do in Cobalt, Ontario (dump it in muckpiles).

The First Cobalt plant was build in 1996 and is approved to deal with the ore. It uses a series of ponds like any other modern processing plant.

MEI, if it wanted to, could also use a relatively small concentrator circuit to turn the ore into a fine powder, then simply ship the high grade concentrate to practically anywhere (its own plant, or someone else's). The waste product in that case is generally inert and can be used as infill.

Plenty of options these days.