Assessment of pilot-scale water purification module with electrodialysis technology and solar energy

Abstract

In this research, an autonomous power module for the purification of brackish water (TDS=5482mg/L) with high concentration of arsenic (2.04mg/L) was successfully designed, constructed and tested. The energy supply for the module is provided by solar power and includes an electrical energy storage system composed of lithium ion batteries. The purification process combines ion exchange and adsorption technologies (column filtration system) with an electrodialysis (ED) system. Different configurations or process sequences were studied to determine the best operating conditions of the system. The salt removal efficiency and specific electricity consumption (SEC) were determined at each stage. It was found that the process that combines all technologies is more efficient than just using ED for the removal of arsenic and salts. The ion exchange step removes the divalent cations, whereas most of the arsenic is adsorbed in the adsorption column system increasing the removal efficiency in the electrodialysis stage. This combined process reduces the time of desalination and the consumption of electricity during the ED. The lowest specific electricity consumption was 2.16kWh/m3 for the ED and 5.46kWh/m3 for the global system. Salt removal exceeded 95% and in the majority of tests, the arsenic removal was more than 99.9%. The power module with the water purification system has a versatile design that allows working with different salts concentration either for the treatment of water from river or underground, effectively removing arsenic. Our proposed solution is an alternative to the conventional technologies for arsenic removal and the results of this study should be useful for the design of other large-scale water desalination systems.