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

J. A.  Capunitan; C. G.  Alfafara; V. P.  Migo; J. L. Movillon; E. I.  Dizon; M.  Matsumura

J. A. Capunitan Department of Chemical Engineering, College of Engineering and Agro-industrial Technology, University of the Philippines Los Baños, College, Laguna, Philippines
C. G. Alfafara Department of Chemical Engineering, College of Engineering and Agro-industrial Technology, University of the Philippines Los Baños, College, Laguna, Philippines
V. P. Migo National Institute of Molecular Biology and Biotechnology, University of the Philippines Los Baños, College, Laguna, Philippines
J. L. Movillon Department of Chemical Engineering, College of Engineering and Agro-industrial Technology, University of the Philippines Los Baños, College, Laguna, Philippines
E. I. Dizon Institute of Food Science and Technology, University of the Philippines Los Baños, College, Laguna, Philippines
M. Matsumura Institute of Applied Biochemistry, University of Tsukuba, Tennodai, Tsukuba City, Japan

Keywords: decolorization, COD, spent ion-exchange-process effluent, electro-oxidation, electrocoagulation

Abstract

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 Re-sources (DENR) standards for Class C waters. Energy cost was also lower than that for electrocoagu-lation, requiring about PhP 740 per m3 of effluent (for operating voltage of 5 volts).