Ion exchange with denitrified brine reuse

An innovative brine reuse process reduced salt consumption and waste discharge by more than 90 percent compared with conventional ion exchange. Ion exchange with chloride‐form anion resin is recommended as a best available technology for removing nitrate from drinking water. Disposal of spent regenerant brine remains a difficult problem, however. A pilot study focused on a new ion exchange process with batch biological denitrification and reuse of the spent brine. Spent regenerant brine from regeneration of the nitrate‐loaded ion exchange column was denitrified in a sequencing batch reactor using methanol as a carbon source. After denitrification, the spent brine was filtered, compensated with NaCl, and reused. Brine denitrification and reuse proved feasible only when using the nitrate‐selective triethyl‐ and tributyl‐amine resins. Compared with the conventional ion exchange process, brine reuse reduced the salt consumption and waste discharge by more than 90 percent.