As part of the EPA Arsenic Removal Technology Demonstration Program, a 540-gal/min (gpm) ion exchange (IX) system proposed by Kinetico was selected for demonstration at Vale, OR to remove arsenic and nitrate from a groundwater supply to meet their respective maximum contaminant level (MCL) of 10-ig/L and 10-mg/L (as N). This report documents the activities performed and results obtained from a 3.5-year long demonstration study that evaluated the performance of IX technology for arsenic and nitrate removal, determined the required system operation and maintenance (O&M) and operator skills, characterized the residuals produced by the technology, and determined the capital and O&M cost of the technology. This demonstration study was divided into three periods: Study Periods I and II and an interim period between the two. Study Period I (extending from September 19, 2006, through January 14, 2008) evaluated the originally proposed Purolite Arsenex II anion exchange (AIX) resin. Because of its deteriorating performance due to organic fouling and difficulties in restoring its exchange capacity after resin cleaning, a dual resin approach was identified and implemented in the interim period to address the relevant issues. In February 2009, Arsenex II resin was replaced with Purolite PFA300E resin, which was overlain with an organic scavenger, Purolite A850END. The performance of PFA300E/A850END was evaluated in Study Period II from February 10, 2009, through March 22, 2010.