Abstract : The objective of this demonstration was to test and validate weak base anion resin ion exchange (WBA IX) technology using established performance objectives in order to obtain permitting and certification from the California Department of Public Health (CDPH) as an approved perchlorate treatment technology. This 1000 gallon per minute system was constructed by Applied Research Associates, Inc. (ARA) to treat groundwater at the Rialto No. 3 well site in the Rialto-Colton, CA area under Environmental Security Technology Certification Program (ESTCP) Project No. ER-200312, Perchlorate Removal, Destruction, and Field Monitoring Demonstration. Because perchlorate concentrations at Rialto No. 3 are elevated, this site is considered to be an extremely impaired source as defined by the CDPH 97-005 Policy Memorandum. ARA worked with water utility and regional CDPH representatives to obtain all of the necessary permits to conduct the test and demonstrate performance. The quantitative performance objectives are: meeting perchlorate regulatory standards; demonstrating posttreatment capability; minimizing process waste, demonstrating spent regenerant treatment; minimizing perchlorate bleed from regenerated vessels; demonstrating treatment flow rates; validating operating costs and future system scalability. Additionally, qualitative performance objectives included demonstrating the ability to model resin treatment capacity for drinking water applications and demonstrating effective system control during operation.