Decolorization and Chemical Oxygen Demand (COD) Reduction of SugarRefinery Spent Ion-Exchange-Process (SIEP) Effluent by ElectrochemicalTreatment Methods

J. A. Capunitan^1,*, C. G. Alfafara¹, V. P. Migo², J. L. Movillon¹, E. I. Dizon³ and M. Matsumura⁴

¹Department of Chemical Engineering, College of Engineering and Agro-industrial Technology, University of the Philip-pines Los Baños, College, Laguna 4031, Philippines
²National Institute of Molecular Biology and Biotechnology (BIOTECH), University of the Philippines Los Baños, College, Laguna 4031, Philippines
³Institute of Food Science and Technology, University of the Philippines Los Baños, College, Laguna 4031, Philippines
⁴Institute of Applied Biochemistry, University of Tsukuba, Tennodai 1-1-1, Tsukuba City 305-0006, Japan
*Author for correspondence; e-mail: jacapunitan@uplb.edu.ph

The application of electrochemical processes, namely electro-oxidation and electrocoagulation, intreating spent ion-exchange-process (SIEP) effluent from a local sugar refinery was investigated. TheSIEP effluent had chemical oxygen demand (COD) content greater than 10,000 mg L^-1, high color(>10,000 PCU) and high salinity (about 35,000 mg L^-1). Electrolysis experiments were conducted atdifferent operating currents, and removal efficiencies for color, total suspended solids (TSS) and CODwere evaluated. Electro-oxidation at 5 A for 7 h achieved 99.9 % decolorization, 63.1% COD reductionand 90.5% TSS removal. Electrocoagulation at 5 A for 8 h resulted in 71.2% decolorization, 18.5 % CODreduction and 97.4% TSS removal. Comparison of the treatment processes yielded electro-oxidationas the better treatment option, as it gave the highest decolorization and COD removal efficiency.Moreover, the color, TSS and pH values were within the Department of Environment and Natural Resources (DENR) standards for Class C waters. Energy cost was also lower than that for electrocoagulation, requiring about PhP 740 per m³ of effluent (for operating voltage of 5 volts).