DOI: 10.14457/tu.the.2020.1036
title: Decolorization and cod reduction of the effluent from biogas chamber by advanced electro-Fenton process

description: This thesis studies the decolorization and chemical oxygen demand (COD) reduction feasibility of the effluent from the biogas chamber by the advanced electro-Fenton (AEF) process, which generates powerful hydroxyl radicals that can degrade the highly colored compound (melanoidin) and concentration of organic matter in the effluent.Electro-Fenton process (traditional electro-Fenton (TEF) process) can produce hydroxyl radicals (•OH) by the continuous electro-generation of hydrogen peroxide (H2O2) on the cathode via oxygen reduction and the addition of ferrous (Fe2+), which can oxidize most refractory organic pollutants in biogas effluent efficiently. The advantage of electro-Fenton process compare to the Fenton process, the electro-Fenton process include producing hydrogen peroxide (H2O2) without adding an expensive H2O2 reagent into the system and easily monitoring electricity. However, from the thesis results, the traditional electro-Fenton (TEF) process showed low efficiencies of the decolorization and COD reduction. In order to reveal the play role of foam nickel can produce superoxide anion (•〖O_2〗^-) to react with hydrogen peroxide (H2O2) for generating hydroxyl radicals which enhance degradation efficiency. Therefore, the advanced electro-Fenton (AEF) process by adding foam nickel in the traditional electro-Fenton (TEF) process was introduced to treat the effluent from the biogas chamber to achieve the most effective color and COD removal efficiencies. The studied parameters were also investigated to find the optimum condition in this thesis by using the advanced-electro-Fenton process which included initial pH (2-11), initial ferrous concentration (0.5-9 mM), applied voltage (1.0-4.0V), and reaction time (0-300 minutes) under ambient temperature.According to the experimental results, the advanced electro-Fenton (AEF) process proved to be the most effective treatment process for decolorization and COD reduction, compared with advanced electrochemical (AEM) process, traditional electro-Fenton (TEF) process, and advanced electro-Fenton process without applied voltage (AEF_0V). The optimum condition for decolorization and COD reduction by the advanced electro-Fenton process was observed at the initial pH of 3, the initial ferrous concentration of 3 mM, the applied voltage of 2.0V, and 120 minutes of the reaction time. The efficiency of decolorization was found to be 87.6±0.5%, in which the color value was reduced from 14,250±250 to 1,767±58ADMI. The efficiency of COD reduction was 73.7±1.1%, in which COD value was dropped from 5,067±230 to 1,335±112 mg/L. It can be concluded that the advanced electro-Fenton (AEF) process is an effective process for decolorization and COD reduction of the effluent from biogas chamber. Nevertheless, this treated effluent needs to be further treated to reduce color and COD values to less than 300 ADMI (American Dye Manufacturers Institute) and 120 mg/L to comply with the standard of wastewater discharged regulated by the Pollution Control Department (PCD), Thailand.