A CDI performs ‘capacitive deionization’ which removes ions from water. The CDI treats water by passing it past or through electrodes that have an electrical potential difference. Thereby anions and cations adhere to the oppositely charged electrodes. Ions accumulate on the electrodes during the adsorption cycle to produce a desalinized water outlet stream. During the desorption cycle the adhered ions are released from the electrodes and discarded in a concentrated waste stream.
PhD, Professor
⚙ Functional materials
⌂ Dept. Materials and Nanophysics
Inlet water from RAS enters the CDI and passes through the electrodes (brown bars). Anions (green dots) will adsorp to the positively charged electrode and cations (red dots) will adsorp to the negatively charged electrode. Notice that the water effluent therefore contains fewer ions than the inlet water. The water outlet returns the purified water to the RAS.
The water inlet closes and new tap water is instead cycled through the CDI. By switching the polarity of the electrodes the adsorped ions (originating from RAS water) will desorp into the tap water and ultimately be discarded as waste water. Thus, ions are removed from RAS with minimal water losses.
