Capacitive Deionization (CDI) is an electrochemical technology for removing charged species like ions of salt from water. Fundamentally it works on “capacitive ion storage”, a phenomenon where in response to energy applied as voltage or current across CDI electrodes, ions of salt are accumulated and stored capacitively as electrical double layers (EDL) at the surfaces of CDI electrodes (similar to a capacitor or battery). Since the accumulation of ions is dominated by physical phenomena (no chemical reaction), it is a reversible process with systems based on CDI technology being characterized by low energy requirements, reduced maintenance and a long service life.

Stockholm Water Technology AB (SWT) has patented (pending) a unique membrane-less CDI system architecture using three-electrodes to reduce system power consumption and improve operational flexibility. This enables SWT products to control the ion content of treated water at ~30% lower input power (<1 kWh/m3 water) and 40% higher water recovery (70% – 80% recovery) compared to other widely used water desalting technologies like reverse osmosis (RO). The low power requirements allow the CDI systems to be powered by commercial solar cells or batteries for remote and portable applications. SWT products are chemical free and can be custom-sized using their novel multi-modular architecture to provide flexibility in terms of quality and quantity of water to be treated at low CAPEX and OPEX.