Electrocoagulation of disperse dyebath wastewater: Optimization of process variables and sludge production

Abstract

This study was conducted to investigate the effect of initial pH, current density, and electrolysis time on process performance in terms of decolorization and chemical oxygen demand (COD) removal from disperse dyebath wastewater (DDW) by mono-polar parallel laboratory scale electrocoagulation (EC) process. COD reduction of 51.3% and decolorization of 92.8% were obtained with operating cost of 0.19 €/m treated wastewater for Al-Al electrode pair, while 90.5% of decol-orization and 49.2% of COD reduction were obtained with operating cost of 0.203 €/m treated wastewater for an Fe-Fe electrode pair. The amount of sludge production were highly related to type of the electrode materials. At the3 optimum conditions, the amount of sludge produced were 0.18 kg/m and 0.28 kg/m for Al-Al and Fe-Fe electrode pairs, respec-tively. High decolorization can be explained by the hydrophobic nature of the disperse dye, while limited COD removal3 3 was observed due to the high dissolved organic matter of the DDW based on auxiliary chemicals. Energy, electrode, and chemical consumptions and sludge handling were considered as major cost items to find a cost-effective and sustainable solution for EC. The contribution of each cost items on operating cost were determined as 10.0%, 51.1%, 30.5% and 8.4% for Al-Al, and they were also determined as 9.0%, 38.0%, 40.5% and 12.5% for Fe-Fe, respectively. COD reduction and decolorization were fitted to first-order kinetic rule.