In September 2003, the City of Phoenix commissioned the nation's first full-scale arsenic removal facility for potable water. The U.S. Environmental Protection Agency (USEPA) is lowering the maximum contaminant level (MCL) for arsenic from 50 parts per billion (ppb) to 10 ppb effective January 2006. In response to this change in the standards, the City decided to build a full-scale Arsenic Treatment Facility (ATF) as a demonstration project and identify operational issues prior to implementing the technology at the City's 15 well sites that have an arsenic concentration greater than 10 ppb. The demonstration facility was built at Well 280 which has a capacity of 2.5 MGD and contains a 1.0 MG reservoir, sodium hypochlorite generator, and booster pump station for pressure zone 9. Due to the water quality and ease in operation, the City chose to implement an adsorption process using granular iron media (GIM). GIM is a throw-away media which after exhausted may be hauled to a non-hazardous waste landfill. At the pH range of Well 280, the process requires no chemical addition other than chlorine to disinfect the media. The process is fairly simple to operate and includes a pre-filter (50 micron mechanical screen), two 14-foot diameter steel contactors with media, rate of flow control valves, equalization basin, spent media drain area, PLC, and several valves and flowmeters. This paper discusses operational issues from this demonstration project that will result in improvements made to the treatment process. Includes figures.