Application of electrodialysis for the treatment of almond industry wastewater

Abstract

In this work, electrodialysis has been proved to be a suitable technique for decreasing the conductivity of a real wastewater from an almond industry, which has been previously treated by electrocoagulation (EC) and electrooxidation (EO). A seven-cell electrodialyzer, with total active membrane area of 1400 cm2, was employed and several parameters, as the limiting current density, were determined. A method for measuring voltage across the membranes was developed, in order to control membrane fouling. The method consisted of capillaries inserted into the solution compartments and connected to a high impedance voltmeter. A study of the reuse of the concentrate solution was made, and it was stated that it can be concentrated 10 times. The treatment of the wastewater was performed at different voltages (7–16 V) to reach values of conductivity of the diluate of 0.5 mS cm−1. After that, the scaling up to a pre-industrial scale was performed by using a 70-cell electrodialyzer, with total active membrane area of 3.5 m2. The process was performed by applying voltages of 20–70 V and a final conductivity of the diluate of 0.5 mS cm−1 was achieved. The electric energy consumption was calculated in every case.