Freeze desalination as point-of-use water defluoridation technique

Abstract Freeze desalination, i.e., desalination of water by freezing it, may be an option to treat polluted water at individual household level. Taking into account the widespread fluoride contamination of Ethiopian water resources and with the reason that most households in semi-urban and urban areas do have easier accessibility of refrigerators, this study aimed to investigate the defluoridation capacity of freeze desalination and its energy consumption for different water sources. For this purpose, synthetic solutions that emulate the major ion compositions of natural waters (hereafter called simulated water), tap water, and double-distilled water to which variable concentrations of fluoride ions were added were evaluated using home-use insulated refrigerator (BEKO, RRN 2650). The effects of conditions such as initial fluoride concentration, multi-ion existence, fraction of ice frozen, volume of the container, and freezing duration were evaluated in relation to the produced ice quality. It was found that nearly 48% and 62% removal of fluoride were achieved from tap water spiked with 10 mg/L F− and 10 mg/L F− aqueous solutions, respectively, with a total water recovery of 85 to 90%. The energy consumption predicted to produce the ice from tap water spiked with 10 mg/L F− and double-distilled water alone was found to be 93.9 and 91.8 kJ/L, respectively. The results showed that freeze desalination can be a potential technique for fluoride removal from water to be used as drinking water at household level in semi-urban and urban areas as well as in colder regions