Enhanced Decolorization Of Azo Dye In Biocatalyzed Electrolysis Reactor With Sleeve-Type Configuration

Bioelectrochemical system can take advantage of the electrochemically active role and degradation role of microorganisms to remove some oxidation and reduction contaminants at electrodes, becoming a new wastewater treatment technology and providing an effective idea for solving environmental issues. Biocatalyzed electrolysis reactor, as one of the bioelectrochmeical system, can accelerate redox processes of contaminants and reduce the demand of electron donor with a relative low applied voltage, driving more and more attentions in the terms of pollutant treatment. It is necessary to solve the azo dye decolorization due to that the textile and dyeing wastewater is large amount, wide range, and difficult to control, especially in the degradation of azo dyes. Thus, this study proposed the use of biocatalyzed electrolysis technology for the degradation of azo dye, focused on key problems in the degradation, and had obtained some innovative achievements.In order to reduce the internal resistance, this study modified the reactor configuration to be a novel sleeve-type, to improve the azo dye decolorization. Results demonstrated the superiority of sleeve-type configuration from both a dual chamber and a single chamber biocatalyzed electrolysis reactor, which has obvious advantages in decolorization and reaction kinetics. The decolorization efficiency was enhanced to be higher than 98% from 50 to 700 mg/L, with high load resistance. In the single chamber reactors, results indicated that CR-DE within 11 h improved from 87.4+1.3% to 97.5+2.3%, and the internal resistance decreased from 236.6 to 42.2 Ω as modifying the horizontal deployment to be a surrounding deployment. Thus, the modified configuration with large area and small distance between anode and cathode can result in a lower internal resistance, which was beneficial to the proton exchange and electron transfer process, finally contributing to the good decolorizaiton. This would be meaningful to accelerate the popularization and final application of this biocatalyzed electrolysis technology for the practical refractory wastewaters treatment.In order to optimize the working position in the reactor, inner/outer chamber for azo dye decolorization was evaluated. Results showed that the outer chamber performed better than that inner chamber as the same cathode and cathode volume or in the increased cathode volume with decolorization efficiencies of 97.8+2.1% (7 h) and 94.0+2.3% (16 h), respectively. Current and EIS analysis indicated that the proton/electron transfer and anolyte diffusion could be improved using outer chamber as working position. Decolorization with increased volume ratio could be further improved through the strategy of increasing substrate concentration, which would provide enough electrons and decrease diffusion resistance, further improving the whole performance. It has the great potential in sleeve-type configuration application and would create more challenges for process optimization and maintenance.In order to enhance the azo dye degradation in the anaerobic sludge processes, this study embedded a modular biocatalyzed electrolysis reactor with surrounding electrode deployment into an anaerobic reactor. Reuslts showed that the system could improve azo dye decolorization. Compared to biocatalyzed electrolysis reactor, it demonstrated that the kinetic rate of decolorization in the integrated system BER-ASR (0.54 h-1) was higher than that in BER (0.39 h-1) and ASR (0.01 h-1). Biocatalyzed electrolysis module was a predominant factor in decolorization, and sludge contributed negligibly to reduction decolorization but mostly in the COD removal. These results demonstrated the great potential of integrating a BES module with anaerobic treatment process for azo dye treatment.Moreover, in order to combine the biologiacal treatment with biocatalyzed electrolysis to improve the degradation performance, three operation conditions (relative positions, catholyte flow sequences, and flow regimes) in the system were evaluated and optimized. Results showed that it was favorable to operate this integrated system under the condition of 1/4 cathode soaking into sludge with spiral distributor in down-flow direction. The decolorization efficiency of 100 and 300 mg/L at HRT=8 h was 95.3±1.7% and 79.4±2.9%, respectively. These results exhibited great potential for matching modular bioelectrochemical system with anaerobic treatment process...