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

Abstract

The enzymatic reduction of Cr(VI) to Cr(III) by Cr(VI) resistant bacteria followed by chemical precip- itation 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 LÀ1 was fed into the bioreactor (0.11–0.33 m3 hÀ1). Complete Cr(VI) reduction to Cr(III) was obtained immediately after the start of bioreactor operation. Together with the ?occulation, coagula- tion and ?ltration, out?ow concentration of less than 0.02 mg Cr(VI) LÀ1 and 1 mg total Cr LÀ1 were always obtained. Performance of the bioreactor was not affected by ?uctuations in pH (6.2–8.4), Cr(VI) (17–81 mg LÀ1), 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.