The ENR® Process – Electrodialytical Nitrate Removal
The electrodialysis process enables specific, partial desalination and has been employed for many years for the desalination of sea- and brackish water. On this basis, in co-operation with the Vienna University of Agricultural Sciences, WABAG has developed the ENR®-process for the denitrification of groundwater.
The most important advantages of the process are:
- Nitrate selectivity
- A low general level of desalination
- Reduction of hardness
- Limited space requirement
- Simple operation and quick start-up.
A large-scale ENR® plant with a capacity of 3,450 m3/d was started-up in Austria during 1997. The nitrate concentration in this case has been reduced from 150 mg/l to < 50 mg/l.
During electrodialysis, salts are separated via ion exchanger membranes by means of an electrical field. Raw water passes through a stack of alternately placed anionic and cationic permeable membranes. The membrane stack is fixed between electrodes, which generate a direct current field. Due to the alternating selectivity of the membranes, cells are formed, some containing diluted water with a low level of salinity, and others filled with concentrated water, which is rich in inorganic salts. Thus, low-nitrate drinking water is produced together with a small amount of concentrate with a correspondingly high nitrate content.