Comparative treatability studies for the decolorization and chemical oxygen demand (COD) reduction of sugar refinery Spent Ion-Exchange-Process (SIEP) effluent
2007
Capunitan, J.A.
The application of electrochemical process, namely electro-oxidation and electroflocculation, as well as the conventional coagulation-flocculation process in treating Spent Ion-Exchange-Process (SIEP) effluent from a local sugar refinery was investigated. SIEP effluent has chemical oxygen demand (COD) content greater than 10,000 ppm, high color (greater than 10,000 PCU) and high salinity (about 35,000 ppm). Electrolysis experiments were conducted at different operating currents, and removal efficiencies for color, total suspended solids (TSS) and COD were evaluated. Electro-oxidation at 5 A for 7 hours achieved 99.9 percent decolorization, 63.1 percent COD removal and 90.5 percent TSS removal. Electroflocculation at 5 A for 8 hours resulted to 71.2 percent decolorization, 18.5 percent COD removal and 97.4 percent TSS removal. In the conventional coagulation-flucculation process, ferric chloride, alum and calcium oxide were applied at different dosages. The maximum decolorization efficiency achieved was only 56.7 percent, at the 25-g/L ferric chloride dosage. Comparison among the treatment processes yields electro-oxidation as the best treatment option, as it gave the highest docolorization and COD removal efficiency. Moreover, the color, TSS and pH values were within the DENR [Department of Environment and Natural Resources, Philippines] standards for Class C waters. Energy cost was also lower than that for electroflocculation, requiring only Php 738.8 per cu m effluent (for operating voltage of 5 v).
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