Nitrate removal of brackish underground water by chemical adsorption and by electrodialysis

Nitrate content has increased in Morocco, especially in underground water of agrarian areas. Several processes including degradation processes and separation processes can remove nitrate from water. Two separating processes were studied to remove nitrate from brackish underground water: adsorption on industrial animal waste and electrodialysis equipped by anion monovalent membrane. The results show that a desired product water quality can easily be obtained by electrodialysis contrary to chemical adsorption which requires a great reactional surface.

The two tested processes showed their capacity to remove nitrate from brackish water. With the electrodialysis equipped by ACS monovalent membrane a desired drinking water respecting the standards can be easily produced from brackish water. The principal disadvantage of this technology is the destiny of the removed concentrate nitrate. The reduction of nitrate by adsorption on natural chitosan is possible but requires an important reactional surface which makes difficult its industrial realisation. The kinetics of nitrate removal by chitosan for this case of water composition is 12 mg-NO3 per gramme of adsorbent with a retention time of 10 min. However, this process can serve to reduce the concentrate nitrate for the electrodialysis reject. Moreover, it permits the valorisation of an industrial animal waste by its utilisation in agriculture as a fertilizer.