Electrocoagulation treatment of cork boiling wastewater

Abstract

Electrocoagulation (EC) was studied as an alternative treatment for Cork Boiling Wastewater (CBW). EC was performed in a bench-scale reactor, using aluminum and stainless-steel electrodes and a sodium chloride solution was used to increase conductivity. Different values of current density, electric tension and electrolyte concentration were tested to assess treatment efficiency and operational costs. The tested procedures achieved removal efficiencies of 93.5%, 82.5%, 88.9% and 99.0% for chemical oxygen demand (COD), total carbon (TC), total nitrogen (TN) and total suspended solids (TSS), respectively, using an electric tension of 15 V. Some experiments after 20 min reached the maximum COD removal, showing that reduction of the operation time can be feasible to maximize cost-efficiency. The prediction of COD removal in a batch treatment based on initial NaCl concentration was investigated during a reactional period of 60 min, demonstrating that higher electrolyte concentrations promote COD removal. Langmuir, Jovanovic Monolayer and Multilayer models were applied and studied to predict the effect of current density and total aluminium mass on COD removal efficiency after 60 min of reaction. The Jovanovic Multilayer model predicted the operating performance for the removal of COD from CBW with higher accuracy when considering the current density. Operational costs for 60 min of electrocoagulation reactional periods have been determined in correlation with current density, in terms of cost per m3, €/COD removed, €/TN removed, €/TC removed, and €/TSS removed. Costs vary between 2.78 and 25.35 €/m3 with 27.6% and 93.8%, respectively. Electrode wear was higher than predicted, suggesting that about 14% of the mass loss should correspond to chemical dissolution. Results show that higher current density and electrolyte concentration reduces electrode wear time but increase overall pollutant removal.

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