On the challenge of developing wastewater treatment processes: capacitive deionization.

Due to the increasing worldwide water scarcity associated with the climate change there is the need to increase the injection of wastewater into the overall water cycle. As a consequence wastewater treatment is within the largest energy use sector in many developed countries. In recent years, capacitive deionization (CDI), which is based on the principle of electrosorption of ions on charged high surface area electrodes, the same as charging and discharging an electrochemical double-layer capacitor, has been reported to be a promising technology which is an alternative to other classical water treatment methods such as reverse osmosis (RO) and evaporation processes. We see that this technology is gaining increased scientific interest since 2006. However, not too many publications indicate the feasibility of the kWh/m3consumption in CDI systems for brackish water treatment (500–30,000 ppm). The common assumption proposes that the main problem may be the ions adsorption capability of the electrode material during discharging. However, in energy efficiency terms, desorption processes may be even more difficult since experience diffusional complications mainly when high currents are used. This presentation will provide an overview of current strategies for operating these systems aiming to improve energy recovery and lead this process to the point of making these systems an option for use in water treatment plants. [ABSTRACT FROM PUBLISHER]