Modified sand for the removal of manganese and arsenic from groundwater

Manganese (Mn) and arsenic (As) are common natural groundwater contaminants and are present at concentrations much higher than the recommended drinking water guidelines. In this study, laboratory investigations were carried out to evaluate the effectiveness of three different types of manganese oxide (MnO2)-coated media in removing manganese and arsenic from water. While all media types were found to be very effective in removing dissolved manganese, the flow rate or contact time was found to have a significant impact on manganese removal. Removal of manganese with 'synthetic' manganese-coated media changed from 30% at a flow rate of 8.0 (ml/min)/cm(2) to almost 100% at flow rates of about 1 (ml/min)/cm(2). Manganese removal was found to increase with increasing manganese content of the filter media and with increasing manganese in the influent water. Removal of arsenic (III) (As3+) in manganese oxide-coated filter media was found to be strongly dependent on pH and phosphate (PO43-) concentration. Removal of arsenic decreased from about 80% at pH 7 to almost nil at pH 9. Arsenic removal decreased from 75% in the absence of phosphate to 2.3% in the presence of 10 mg/l phosphate. Results show that manganese oxide-coated media can efficiently remove both manganese and arsenic.