Reactive dyes have been problematic compounds in textile effluents as they are water soluble. Textile effluents also have a high organic load in the scouring and desizing processes. However, textile wastewater is nearly complete decolorization under anaerobic conditions. Therefore, this research investigates the decolorization and kinetics of reactive dye (C.I. Reactive Red 120) in different carbon sources by partially granulated anaerobic mixed culture. Three sizing agents, namely acrylic size (AS), polyvinyl alcohol (PVA) and modified starch (MS) were used as carbon sources which the COD concentration of 1200 mg/l. Batch test experiments were employed by mixing the 1.8 g MLVSS/l of mixed microorganisms in the solution containing each carbon source and dye and then incubated in incubator at 371 C for 324 hours. Results revealed that two steps of decolorization was found when used AS and PVA as carbon sources. The first step showed high rate of decolorization, while the second step showed low rate of decolorization. The maximum decolorization for AS, PVA and MS as carbon sources were 89.25, 88.74 and 93.97 %, respectively when the dye concentration of 60 mg/l were applied. The k values and color removal rate of decolorization with MS was higher than AS and PVA as carbon sources, respectively. This is because, the MS as carbon source was simple structure compared to AS and PVA. Additional experiments on the effect of dye concentration, using MS as the carbon source, revealed that degradation of RR 120 followed first-order kinetic. The decolorization rates increased with the decreasing dye concentrations of RR 120. On the other hand, the zero-order kinetic of decolorization respect to AS as carbon source, and then the zero-order kinetic of decolorization respect to PVA as carbon source in lowest dye concentration of 20 mg/l. In conclusion, the anaerobic biodegradation of textile wastewater containing MS can be achieved, and that enhancement of azo reduction through addition of MS (electron acceptor) carbon source.

Keywords - Anaerobic treatment; Decolorization; Kinetics; Reactive dye

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About the Authors:

Sunantha Laowansiri and Soydoa Vinitnantharat are associated with Division of Environmental Technology, School of Energy and Materials, King Mongkuts University of Technology Thonburi, Thungkru, Bangkok, 10140, Thailand.

Pawinee Chaiprasert is associated with Division of Biotechnology, School of Bioresources and Technology, King Mongkuts University of Technology Thonburi, Thakam, Bangkhuntien, Bangkok, 10150, Thailand.

Sung-Ryong Ha is associated with Department of Urban Engineering, Chungbuk National University, Keshindong Heudukgu Cheongju, Chungbuk, 361-763, Republic of Korea.