Electrodialysis for removal of chromium (VI) from effluent: Analysis of concentrated solution saturation

Electrodialysis (ED) was used as a sequential treatment of a hybrid anaerobic bioreactor to evaluate the saturation of the concentrated solution flow in its efficiency. The chromium (VI) in the anion form (Cr2O72-) at initial concentrations of 10, 65 and 100 ppm were used in feed streams. The operating flows were of 20, 60 and 60 L h(-1) for electrolyte, feed and concentrated solution, respectively. The current limit used was of 0.03 A. The chromium (VI) removal was approximately 99% +/- 0.5% with 75 min of operation. For an initial volume of effluent equal to 76 L the final volume of wastewater concentrated solution was equal to 4 L, with a maximum concentration of chromium (VI) of 570 ppm. The results showed that with this concentrated solution it was not possible to remove the ion Cr2O72- in the feed even with clean membranes, that is, the concentrated solution concentration can be considered a limiting variable of the electrodialysis.