Biological groundwater treatment for hexavalent chromium removal at low chromium concentrations under anoxic conditions.

The objective of this work is to evaluate biological groundwater treatment systems that will achieve hexavalent chromium removal from groundwater at hexavalent chromium (Cr(VI)) groundwater concentrations in the 0-200 μg/L range under anoxic conditions. The effect of type of organic substrate added as feed to the groundwater treatment system (milk, sugar and cheese whey), the effect of different concentrations of chemical oxygen demand added in the feed (100, 150 and 200 mg/L) and the effect of different hydraulic residence time (1.7, 0.