The typical EDI installation has the following components: electrodes, anion exchange membranes, cation exchange membranes, and resin. The simplest configurations comprise three compartments. To increase production intensity or efficiency, the number of compartments or cells can be increased as desired.
Once the system is installed and feedwater begins to flow through it, cations flow toward the cathode and anions flow toward the anode. Only anions can go through the anion exchange membrane, and only cations can go through the cation exchange membrane. This configuration allows anions and cations to flow in only one direction because of the selectivity of the membranes and the electrical forces, rendering the feedwater relatively free of ions. It also allows for the separate collection of cation and anion concentration flows, creating the opportunity for more selective waste disposal, recycling, or reuse; this is especially useful in the removal of heavy metal cations.