Removal of nitrates from potable water by ion exchange

Abstract

The feasibility of removing nitrates from otherwise potable water by means of anion exchange was investigated. Candidate anion exchange resins had to demonstrate a higher affinity for nitrate ions than for the other ions present (Cl⁻, HCO₃ ⁻). The distribution factor between chloride and nitrate was investigated with the anion exchange resin Amberlite-400. In studies of column operation it was found that sea water was as effective as NaCl for regeneration. The nitrate ion capacity was proportional to the nitrate ion concentration and to the TDS in the feed. Nitrate ion leakage was greater with lower levels of regeneration. An operational capacity for nitrate of 0.3 to 0.4 me ml⁻¹ was found; this capacity was not significantly affected by the presence of sulfate ion in low concentration (2 me 1⁻¹).