Capacitive Delonization Technology™ :: An alternative desalination solution

This paper reports on research conducted on Capacitive Deionization Technology (CDT) as an alternative to the more conventional membrane desalination technologies like reverse osmosis and electrodialysis. The main objective of the research was to develop an industrial type module and to evaluate the performance of the module for brackish water desalination. The term "industrially re-producible" refers to the fact that the module manufacturing process must be scaleable, practical and cost effective. Once a successful industrial prototype was developed, a secondary research objective was to test such a module in order to determine if CDT (TM) could compete as a potential alternative to membrane processes. The following criteria were used to compare the results from the "industrial type" CDT (TM) bench-scale unit to other membrane processes: center dot Feed and product water quality requirements center dot Energy consumption per volume water treated center dot Pre and post treatment requirements center dot Ion storage capacity of electrodes/overall desalination reaction kinetics center dot Automatic Control or Operation/Maintenance Requirements center dot Fouling and scaling tendencies. Desalination by CDT (TM) occurs when a saline solution flows through an unrestricted capacitor type module consisting of numerous pairs of high-surface area (carbon aerogel) electrodes. Carbon aerogel contains a very high specific surface area (400-1100 m(2)/g BET), and a very low electrical resistivity (<40 m Omega(.)cm). Anions and cations in solution are electrosorbed by the electric field upon polarization of each electrode pair by a direct current (DC) power source. By using the laboratory scale unit as a model, an industrial type bench scale test: unit was developed and tested as part of this research Earlier laboratory test work indicated that the intrinsic energy required by CDT (TM) to reduce the TDS of brackish water from 1000 mg/l to 10 mg/l is 0.1 kWh/m(3). These estimates assumed that 50-70 % energy recovery could be obtained via the electrical discharge