Removal rates of electrolytes commonly found in brackish groundwater by means of electrodialysis reversal desalination

Abstract

This thesis tested and analyzed the removal rates of six different electrolytes: NaCl, Na2SO4 , MgCl2 , K2SO4 , Ca(NO3 )2, and CaSO4 when using electrodialysis reversal (EDR) desalination. A bench top EDR set-up was designed and built, and this set-up was used to desalinate feed water with initial concentrations of about 1000 ppm of each of the electrolytes. The tests ran until the diluate stream reached a concentration of 415 ppm. These results were then compared to a mathematical model that predicts the electrolyte removal behavior, and the experimental results did align with the model. When the mathematical model was used to estimate the electrolytes' behaviors for beginning concentrations of exactly 900 ppm, it was shown that the ranking of electrolytes with highest to lowest removal rates is NaCl (38.8 ppm/min when the diluate concentration is 415 ppm), K2SO4 (36.0 ppm/min), CaSO4 (33.6 ppm/min), Na2SO4 (33.4 ppm/min), MgCl2 (32.7 ppm/min), and Ca(NO3)2 (31.8 ppm/min).