Study On Reactive Dyes Degradation In The Bioelectrochemical Anaerobic System

Anaerobic sludge with high degradation capacity for the dye- C.I. Reactive blue 5 (RB5or K-GR) was cultivated. An integrative bio-electrochemical anaerobic system with anaerobic sludge and electrolysis was constructed. In this system, graphite was used as the material of cathode and anode electrode. Under mesophilic temperature (35±1℃),the degradation effect and decolorization kinetics of reactive brillent blue K-GR,reactive brillent red C.I. Reactive Red 20(RR20or KD-8B) and mixed dye including above two kinds of dyes were investigated in the bio-electrochemical anaerobic system through batch experiments. The decolorization of K-GR, KD-8B, mixed dyes and actual dye wastewater by an electricity-UASB ( upflow anaerobic sludge basket) reactor was also studied under optimum operation conditions. The probable decolorization mechanism of these dyes in the bio-electrochemical anaerobic system was preliminarily discussed by means of UV-vis, FT-IR and GC-MS analysis methods.(1)The optimum conditions for 100 mg/L K-GR decolorization in the bio-electrochemical anaerobic system were pH 8.0, current intensity 30 mA, sludge concentration 3 gVSS/L and switching continuously. The color removal rate of over 90% could be obtained under the condition.(2) The decolorization rate of K-GR and KD-8B was obviously improved in the bio-electrochemical anaerobic system. Compared with single anaerobic microorganism and single electrolysis treatment systems, more than 15% decolorization rate could be improved in the system with the same influent and operation conditions.(3) In above three treatment systems, the decolorization process of K-GR and KD-8B both obeyed the first-order reaction dynamics. Under the optimum operation condition, the dynamical constants k1of K-GR and KD-8B in the bio-electrochemical anaerobic system were 23.9×10^-2h^-1 and 32.7×10^-2h^-1 respectively. When mixed dyes were treated, the dynamical constants k1 of K-GR and KD-8B were 17.7×10^-2h^-1 and 4.16×10^-2h^-1 respectively.(4) During continual operation, when the dye concentration of K-GR, current intensity were 100 mg/L and 30 mA respectively, switching 12 h and halting 14 h continuously, bio-electrochemical anaerobic system could significantly improved the COD and color removal rate of K-GR, KD-8B and mixed dye wastewater; The color removal rate could be improved more than 15% compared with original UASB reactor. (5) Based on analysis results of UV-vis, FT-IR and GC-MS, decolorization of K-GR and KD-8B were realized mainly by cleavage of conjugate structure of anthraquinone and azo bond respectively in the bio-electrochemical anaerobic system. During the decolorization, many intermediate products with the structure of benzene ring and cricoid unsaturated structure were produced. Moreover, many unsaturated or saturated hydrocarbons could be produced by cleavage of benzene ring.