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 0.2 m3 bioreactor. Neutralized electroplating wastewater with Cr(VI) concentration of 17-81 mg L−1 was fed into the bioreactor (0.11-0.33 m3 h−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 0.02 mg Cr(VI) L−1 and 1 mg total Cr L−1 were always obtained. Performance of the bioreactor was not affected by fluctuations in pH (6.2-8.4), Cr(VI) (17-81 mg L−1), nutrient (liquid pineapple waste, 1-20% v/v) and temperature (30-38 °C). Standby periods of up to 10 days can be tolerated without loss in activity. A robust yet effective biotechnology to remove chromium from wastewater is thus demonstrated.