| A bio-film electrode reactor (BER) was used as pre-treatment prior to constructed wetland-microbial fuel cell (CWMFC) in this paper, for its co-operative function of electrochemical action and biological process could improve the bioavailability of refractory organic printing and dyeing wastewater, and the removal efficiency of refractory organic printing and dyeing wastewater and the electricity prodution performance in the CWMFC were promoted. Moreover electricity energy generated by CWMFC was supplied to BER, and the BER-CWMFC system achieved the exchange of substance and energy. Azo dye reative brilliant red X-3B was used as the target pollutant in this study. The removal efficiencies and influence factors of one-piece BER and three-dimensional BER (3D-BER) were investigated. Furthermore, the electrical properties and the removal effect of X-3B by one-piece BER-CWMFC coupled system and three-dimensional BER-CWMFC coupled system were studied. The results were obtained as follows:Through the analysis of the effect of voltage on the removal of X-3B in one-piece BER, the results showed that by the co-operative function of electrochemical action and biological process the improvement of the removal of X-3B in one-piece BER was obvious when the voltage was above 0.8V. Under the voltage of 0.8V and 1.0V, the removal of X-3B was 18.36% and 35.86% higher than the control group. One-piece BER-CWMFC coupled system was built for researching. The maximum outpt voltage of CWMFC stack was 0.95 V, and the maximum output power was 0.21mW. During continuous operation voltage reversal did not occur in one-piece BER-CWMFC system. Compared to one-piece BER and CWMFC, the degradation efficiency of X-3B in one-piece BER-CWMFC coupled system increased by 34.46% and 7.16%. Through the analysis of the effect of current on one-piece BER-CWMFC coupled system, the results showed that in one-piece BER-CWMFC coupled system, the removal rate of CODcr, which ranged from 73.00% to 88.62%, and the degradation efficiency of X-3B, which ranged from 44.03% to 60.70%, in one-piece BER unit increased when the current of one-piece BER unit increased. Within the voltage of 0.2-0.6V, the degradation efficiency of X-3B in one-piece BER unit was stable. The removal rate of CODcr, which was about 75.00%, in CWMFC units was similar while the degradation efficiency of X-3B was different. The change of current caused the improvement to the degradation efficiency of X-3B in CWMFC-1 unit and inhibited the the degradation efficiency of X-3B in CWMFC-2. The degradation efficiency of X-3B in one-piece BER-CWMFC coupled system decreased slightly with the change of current.The effect of applied voltage and substance concentration on the degradation efficiency of X-3B in 3D-BER was discussed in this paper. The results showed that by the co-operative function of electrochemical action and biological process the degradation efficiency of 3D-BER to X-3B increased by about 20.00%, compared with 3D-BER which applied voltage was 0V. In the voltage range (0.5-2.0V), the the degradation efficiency of 3D-BER to X-3B was promoted similarly. Within the influent concentration of X-3B in 200-800mg/L, changes of concentration did not affect the degradation performance on X-3B in 3D-BER and the apparent internal of 3D-BER was stable. The analysis of UV-Vis and GC-MS showed that the rupture of azo bonds in X-3B molecules occurred mainly in the cathode zone and aromatic amines such as aniline were formed, however, the further degradation of aromatic amines were carried out in the anodic zone.The three-dimensional BER-CWMFC coupled system was built for studing its electrical properties and removal effects of X-3B. The results showed that three-dimensional BER-CWMFC degradated X-3B effectively at high concentration. When the concentrations of X-3B were 500mg/L and 1000mg/L, the degradation efficiency of X-3B were above 99.00%. During continuous operation, the maximum outpt voltage of CWMFC was 0.50V, and the maximum output power was 0.21mW. The degradation efficiencies of X-3B in one-piece BER-CWMFC coupled system and three-dimensional BER-CWMFC coupled system were above 97.00% Compared with one-piece BER-CWMFC coupled system, three-dimensional BER-CWMFC coupled system had more advantages in degradating X-3B wastewater of high concentration. |
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