CDI is a simple 2-step process wherein water flows between electrodes, where the electrode surfaces
are separated from the water by membranes that selectively allow positive or negative ions to pass. In
the first step, purification, saline water passes between oppositely charged electrodes which
electrostatically remove dissolved ions, leaving pure water flowing out of the cell. In the second step,
regeneration, feed water flushes through the cell at a lower flow rate, while electrode polarity is
reversed. Ions are then rejected from the electrode surface, concentrated in the flow channel, and
flushed from the cell before the cycle is repeated. Moreover, a critically important feature of the
technology is that the amount of TDS removed from the water is tunable and the process is dynamically
controlled automatically based on feed water characteristics and hence the system can easily handle
variations in feed water characteristics.
