The high rate bio-oxidation of minerals in tanks has received a great deal of interest over the last decades. So far, aerated stirred tank reactors, which are common in the mining industry, have been used for these processes. However, as we are dealing with a biological system, it makes sense to apply reactor types that are especially designed for biotechnological applications. PAQUES has extensive experience with high rate biotechnology in reactors. The Circox((R)) air-lift loop reactor was especially designed for biological processes and is characterised by high mass transfer rates and good mixing. At present, a full-scale sulphate-reducing reactor is running in which metals precipitation results in 20% solids concentration in the gas-lift reactor. From in-house desk studies and experimental work carried out on pilot plant scale and full scale, it is concluded that the Circox((R)) air-lift loop reactor is a viable alternative to stirred tank reactors for the bio-oxidation of minerals. The main advantages of the air-lift loop reactor over the conventional stirred tank reactor are lower capital and operational expenditures and the ease of scale-up.