In order to prove that perchlorate-laden resins could be bio-regenerated through direct contact with anaerobic microorganisms, two bio-regeneration systems, internal and external, were tested. Anaerobic digestion was demonstrated to be very efficient in degrading perchlorate that had been adsorbed onto A520E resin. The internal bio-regeneration test showed that the fully exhausted resins recovered about 80% of the perchlorate-exchange capacity after 4 weeks of bio-treatment in the anaerobic digester. The bio-regeneration efficiency of the external system increased with the amount of flow passed through the column. Comparison of two perchlorate breakthrough curves obtained from column test, one with virgin resin and the other with bio-regenerated resin, proved that the bio-regenerated resin could be used repeatedly to treat perchlorate in spent or waste brine. The A520E resin was very stable in the anaerobic digester and its perchlorate-exchange capacity was barely changed during 26 weeks of incubation. The most significant contribution of this research is to develop the concept of direct bio-regeneration of exhausted resins by combining physicochemical ion-exchange and biological reduction technology, especially for the removal of perchlorate.