Studies on the resistance developed at different stages in an electrodialysis stack operated in parallel-cum-series flow pattern

The experimental results obtained during desalination of brackish water having total dissolved solid (TDS) of 6560 ppm in an electrodialysis (ED) stack containing 42 cell pairs of cation and anion-exchange membranes (IEMs) with an effective area of each membrane being 80 cm2 have been described. A parallel-cum-series flow pattern in six stages containing 9, 8, 7, 7, 6, and 5 cell pairs, respectively, has been employed in all the experiments, which have been carried out at different flow rates and under a fixed voltage of 70 V. During the experiments, the resistance developed in each stage is measured. The resistance per cell pair increases slowly upto fourth stage and then sharply to the end stage. It was possible to achieve an 84.76% reduction in TDS at a flow rate of 2.4 l/h with a current efficiency of 75.25% and energy consumption of 1.0 kWh/kg salt removed.