Paques and Umicore have demonstrated the feasibility of biological treatment of the highly complex Hoboken wastewaters in a 1 m 3 /h pilot plant at Umicore Precious Metals, Hoboken, Belgium.
In the first step arsenic was precipitated from copper smelter effluent as As 2 S 3 using biogenic produced H 2 S. Other metals such as copper, lead and cadmium were also removed as MeS to concentrations well below the discharge levels.
Subsequently, sulfate and nitrate were removed to low concentrations (<300 mg/l and < 5 mg/l respectively) in high rate engineered bioreactors. Sulfide produced in the sulfate reduction process was recycled to step 1 for metals precipitation.
Selenite/selenate was partly removed in the sulfide precipitation step, whereas the excess was biologically reduced and removed as selenium to concentrations <0.2 mg/l.