Simultaneous removal of nitrate and hardness ions from groundwater using electrodeionization

Nitrate concentrations in groundwater frequently exceed permissible levels for potable water in intensive agricultural regions. It is critical to develop highly efficient techniques for the removal of nitrate at low cost, without the addition of chemicals. In this study, we report on an advanced and efficient approach, referred to as electrodeionization (EDI), for effectively removing and concentrating nitrate with low energy consumption. An additional merit of this process was that hardness ions, such as Ca2+ and Mg2+, were also simultaneously removed from the dilute compartment and recovered in concentrate compartment. Furthermore, the limiting current was systematically investigated and the impacts of different applied currents, water flow rates, and ratios of cationic and anionic exchange resins on the performance of nitrate removal were studied. When treating actual groundwater samples, the EDI system exhibited an excellent removal rate for all ions (>90%) under a low and constant cell voltage. The results confirmed that the EDI process is suitable for the continuous and highly efficacious removal and recovery of nitrate and hardness ions in ground water.