Biological regeneration of nitrate‐loaded anion‐exchange resins by denitrifying bacteria

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Abstract
For regeneration of nitrate‐loaded anion‐exchange resins large quantities of salt are needed while the voluminous concentrated brine, produced during regeneration, is difficult to dispose of. These problems can be avoided by using denitrifying bacteria in the regeneration process of the resins. Experiments showed that resins could be regenerated by a denitrifying sludge suspension containing 7 g dm−3 NaCl. However, the process proceeded slowly compared with conventional regeneration. After 24 h of regeneration the resin still contained 18% nitrate, relative to the total capacity. The breakthrough curve of a biologically regenerated ion‐exchange resin was characterized by nitrate leakage whereas nitrate breakthrough started sooner, resulting in a nitrate capacity which was only 72% as compared with a conventionally regenerated ion‐exchange column.