A Combination of Ion Exchange and Electrochemical Reduction for Nitrate Removal from Drinking Water Part I: Nitrate Removal Using a Selective Anion Exchanger in the Bicarbonate Form with Reuse of the Regenerant Solution

Author： Jelínek Luděk Parschová Helena Matějka Zdeněk Paidar Martin Bouzek Karel

Publisher： Water Environment Federation

ISSN： 1061-4303

Source： Water Environment Research, Vol.76, Iss.7, 2004-11, pp. : 2686-2690

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Abstract

The process of selective nitrate removal from drinking water by means of ion exchange was studied. A commercial strong base anion exchanger with triethylammonium (−N⁺Et₃) functional groups was used in the bicarbonate (HCO₃⁻) and carbonate (CO₃²⁻) form. The aim of this study was to optimize ion-exchanger regeneration in view of the sub- sequent electrochemical reduction of nitrates in the spent regenerant so- lution. The effects of ion-exchanger form, concentration of regenerant solution, and presence of nitrates, chlorides, and sulphates in the regenerant solution were studied. The strong base anion exchanger in HCO₃⁻ form that was investigated was able to treat 270 bed volumes of model water solution containing 124 mg dm⁻³ nitrates. To achieve adequate regeneration of the saturated anion exchanger, it is necessary to use approximately 30 bed volumes of fresh 1-M sodium bicarbonate (NaHCO₃) regenerant solution. The presence of residual 50-mg dm⁻³ nitrates in the regenerant solution, treated by electrolysis, resulted in an increase in the dose of regenerant solution to 35 bed volumes and a decrease in the subsequent sorption run of approximately 13%. The volume of applied regenerant solution was high, but the consumption of NaHCO₃ for regeneration was low.