Nitrate Removal from South Dakota Ground Water by Nitrate-selective Ion Exchange Resins

Several communities in eastern South Dakota are currently facing the high nitrate concentrations in their water supplies. The experimental research on nitrate removal by ion exchange process using nitrate-selective resins was completed to develop meaningful engineering information so that it may be used by engineers to help alleviate high nitrate in the water supplies. In this research, large-scale laboratory ion exchange columns were operated with three nitrate-selective resins (Ionac SR-6, IMAC HP 555S, Purolite A- 520E) and one conventional resins (Amberlite IRA-402). The resins were exhausted with three different high nitrate ground waters each having different degrees of sulfate and nitrate composition. The resins were then regenerated with 6% sodium chloride. Their regeneration characteristics were evaluated and compared. IMAC HP 555S was found to be the most effective resin for nitrate removal. Nitrate/(Nitrate+Sulfate) ratio in milliequivalents of the three ground waters used in the research were 0.26, 0.49, and 0.64. Experimental results showed that when the sulfate concentration is greater than the nitrate concentration in the groundwater, nitrate-selective resins were more effective than conventional resins. When sulfate and nitrate concentrations are approKimately equal and at relatively low concentrations, then the resin with a good regeneration characteristics and large total exchange capacity may be considered. When nitrate content is greater than sulfate content in the ground water, then more careful evaluation is required on various factors such as brine use factor and percent of anion recovered during regeneration. From this research HP 555S and IRA-402 performed equally when the nitrate concentration was higher than the sulfate concentration