Potential mechanisms for bioregeneration of perchlorate-containing ion-exchange resin

• A conceptual model for biodegradation of resin-attached perchlorate is proposed.
• Chloride ion is likely the desorbing agent of resin-attached perchlorate in bioregeneration.
• Decreasing the resin bead size has a positive effect on the resin bioregeneration process.
• Resin bioregeneration is mass-transfer controlled rather than bio-kinetic controlled.
• Macroporous resins are more effectively bioregenerated when compared to gel-type resins.

Ion-exchange (IX) is the most feasible technology for perchlorate removal from drinking water. Reuse of resins present challenges, however. Selective resins are non-regenerable, and are incinerated after one time use, while non-selective resins, when regenerable, produce a waste stream that contains high concentration of perchlorate that must be disposed of. A process to bioregenerate spent resin containing perchlorate with perchlorate-reducing bacteria (PRB) has been recently developed. In this research, potential mechanisms for bioregeneration of resin-attached perchlorate (RAP) were investigated. Batch bioregeneration experiments were performed using gel-type and macroporous-type resins. Various initial chloride concentrations and various resin bead sizes were used. The results of the bioregeneration experiments suggested that chloride, i.e. the product of perchlorate biodegradation, is more likely the desorbing agent of RAP; and increasing the concentration of chloride enhances the bioregeneration process. Both film and pore diffusion were found to be relevant with respect to the rate of perchlorate mass-transfer to the bulk liquid. Bioregeneration was found to be more effective for macroporous than for gel-type resins, especially in the case of macroporous resins with relatively small bead size in the presence of higher chloride concentration.

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