A pilot study was conducted to compare the effectiveness of ozone and potassium permanganate for iron and manganese precipitation for a natural groundwater in Queens, New York. The oxidants were tested under various contact times, dosages, and pH levels. In addition, ozone testing included an evaluation of byproduct formation of aldehydes and bromate, and biostability sampling. Ozone was found to be the more effective oxidant. It required a lower dosage, less contact time, and no pH adjustment of the groundwater (natural pH is 6) prior to oxidation. Byproduct formation and biofouling of the downstream membranes and water piping were also not an issue during the testing. Includes 11 references, tables, figures.