Many water treatment plants that utilize groundwater will be burdened with additional expenses in order to meet the new Maximum Contaminant Level of 10 :g/L for arsenic. The objective of this project was to develop an inexpensive treatment option for arsenic removal, suitable particularly for small communities, by extending and optimizing the Fenton chemistry that already occurs during iron removal at many drinking water treatment plants. Improvement of the efficiency of arsenic (III) oxidation to arsenic (V) by hydrogen peroxide addition and addition of more iron to furnish more hydrous ferric oxides (HFO) for adsorption of the arsenic allow removal of arsenic from 40 to 5 :g/L (compared to 30 :g/L during normal iron removal) in high-DOC (13 mg C/L) groundwater, while increasing chemical costs only slightly, and requiring no large capital equipment costs.