Treatment of Bypass Wastewater Using Novel Integrated Potassium Ferrate(VI) and Iron Electrocoagulation System

Abstract

Bypass wastewaters in excess of plant capacity require in-plant wastewater treatment strategies capable of lessening the contamination magnitude prior to their discharge into water bodies. This study introduces a novel hybrid potassium ferrate(VI)–iron electrocoagulation system for the treatment of bypass wastewater. To understand the synergistic effect of the hybrid system, the response surface methodology and the Box Behnken design were utilized based on four preselected variables (current density, potassium ferrate(VI) dosage, interelectrode distance, and time). The current density and potassium ferrate(VI) dosage and their interaction were found significant in achieving a higher soluble chemical oxygen demand (sCOD) removal and faster ferrous (Fe2+) oxidation. The addition of 0.10 mM potassium ferrate(VI) to the electrocoagulation cell operated for 45 min at a 22 mA/cm2 current density and 15 mm interelectrode distance increased the sCOD removal efficiency from 39.71% to 63.57%. Moreover, the addition of 0.1 mM potassium ferrate(VI) to the previously stated electrocoagulation cell conditions decreased the percentage of Fe2+ to the electrochemically supplied total iron (Fet) from 34.02% to 4.63%. The oxidation effect provided by the addition of potassium ferrate(VI) to the iron electrocoagulation cell increased the sCOD removal by about 10%. In addition, the pH increase that resulted from the dissociation of potassium ferrate(VI) promoted favorable conditions to quickly oxidize the Fe2+ ions generated at the iron anode to form the favorable Fe(OH)3 precipitates. The experimental results clearly demonstrated the synergetic effect of the coupled processes for the removal of sCOD from bypass wastewater.