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

Abstract

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 9000mgL−1) and current densities (41.7, 83.3 and 166.7mA 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 pre-treated TOPW (COD 1000mgL-1 and current densities of 3.87 and 5.65mA 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 3000mgL−1 at 166.7mA 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 5.65mA 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.