Pilot-scale removal of chromium from industrial wastewater using the ChromeBac™ system

The enzymatic reduction of Cr(VI) to Cr(III) by Cr(VI) resistant bacteria followed by chemical precipitation constitutes the ChromeBac™ system. Acinetobacter haemolyticus was immobilized onto carrier material inside a 0.2m3 bioreactor. Neutralized electroplating wastewater with Cr(VI) concentration of 17–81mgL−1 was fed into the bioreactor (0.11–0.33m3h−1). Complete Cr(VI) reduction to Cr(III) was obtained immediately after the start of bioreactor operation. Together with the flocculation, coagulation and filtration, outflow concentration of less than 0.02mg Cr(VI)L−1 and 1mg total CrL−1 were always obtained. Performance of the bioreactor was not affected by fluctuations in pH (6.2–8.4), Cr(VI) (17–81mgL−1), nutrient (liquid pineapple waste, 1–20%v/v) and temperature (30–38°C). Standby periods of up to 10days can be tolerated without loss in activity. A robust yet effective biotechnology to remove chromium from wastewater is thus demonstrated.