Treatment of highly toxic cardboard plant wastewater by a combination of electrocoagulation and electrooxidation processes

Abstract

The objective of this study was to investigate the removal efficiencies of the electrochemical treatment systems as an alternative for the treatment of cardboard plant wastewater (CPW). In accordance with this purpose, CPW was treated by electrocoagulation (EC) with Al electrodes and the effects of current density (CD), operating time (t), and initial pH (pHi) were investigated. The results showed that EC at optimum treatment conditions (CD: 7.5mA/cm2, pHi: 7.0 and t: 60min) have limited removal efficiencies for total organic carbon (TOC; 17.1%) and chemical oxygen demand (COD, 14.2%), on the contrary of turbidity (98.7%). Due to the low TOC and COD removal efficiencies, a secondary treatment was needed and the electrocoagulated effluent was subjected to electrooxidation (EO) by using a boron doped diamond (BDD) electrode for investigating the effect of CD, t, pHi and electrolyte concentration (Ce). Higher TOC (83.7%) and COD (82.9%) removal efficiencies were obtained by EO under the optimum treatment conditions (CD: 100mA/cm2, pHi: 7.2, Ce: 5.0g/L Na2SO4 and t: 180min). In addition, a toxicity test was carried out to the raw and treated wastewater under the optimum operating conditions. This study demonstrated that the combination of EC and EO have a satisfactory potential for real industrial wastewater with a high organic content, suspended solids and toxicity.