Treatment of table olive processing wastewaters using electrocoagulation in laboratory and pilot-scale reactors

Electrocoagulation-(EC) is investigated as an alternative, cost-efficient, method for the treatment or post-treatment of table olive processing wastewaters (TOPWs). Experiments were performed in both laboratory and pilot-scale reactors using aluminum and iron electrodes. Different initial chemical oxygen demand (COD) concentrations (3000, 5000 and 9000 mg L-1) and current densities (41.7, 83.3 and 166.7 mA cm(-2)) were tested in laboratory-scale experiments to determine maximum COD and color removal from untreated TOPWs. Pilot-scale experiments were also conducted using biologically pretreated TOPW (COD 1000 mg L-1 and current densities of 3.87 and 5.65 mA cm(-2)) to ensure an efficient post-treatment process. Aluminum electrodes were found to be more efficient in reducing COD and color than iron electrodes in both laboratory and pilot-scale experiments. In laboratory-scale experiments the maximum COD and color removal (approximately 50% and 100%, respectively) was recorded for the lowest initial COD concentration of 3000 mg L-1 at 166.7 mA cm(-2). In the pilot-scale reactor the maximum COD and color removal observed was 42.5% and 85.3%, respectively, for the current density of 5.65 mA cm(-2). Lower energy and electrode consumption was recorded when working with aluminum electrodes and optimum results were obtained with the lowest initial COD and current density values tested. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.