The Decoloration On Azo Dye In A Membrane Bioreactor By Genetically Engineered Strain

Azo dyes are widely used for printing, papermaking, cosmetic industries as well as textile dyeing because of their chemical stability, ease of synthesis, and versatility. Release of azo dyes into the environment from the effluents of dye-utilizing industries mentioned above has become a major concern in wastewater treatment.The characters and harms of dye wastewater are summarized in this paper. Some conventional methods of wastewater treatment cannot effectively decolorize water contaminated by azo dyes. Four aspects are included in the paper, the optimal conditions of decoloration on Acid Red B; the study on decoloration in a membrane bioreactor (MBR) by E. coli JM109 (pGEX-AZR); the optimal conditions of decoloration on Direct Blue; the study on decoloration in a sequence membrane bioreactor (SMBR) by E. coli JM109 (pGEX-AZR).The optimal conditions of decoloration on Acid Red B are: influent concentration of Acid Red B is 500 mg·L^-1, the initial biomass is 1.0 g·L^-1, pH 7.0-8.0, glucose concentration is 1.0 g·L^-1. In this study an anaerobic membrane bioreactor (MBR) using gene engineering strain E. coli JM109 (pGEX-AZR) is used for the decoloration of Acid Red B solutions. The results from the study show that, the bioreactor with E. coli JM109 (pGEX-AZR) has a high capacity for decoloration. The decoloration efficiency and COD_Cr degradation rate exceed 95 % and reached 68 %, respectively. As in the continuous operation, the biomass increases from 0.58 g·L^-1 to 0.82 g·L^-1, and then remains stable at about 0.4 g·L^-1. Influenced by the bacteria activity, EPS changes with the biomass. The pH value falls from 6.5 to 6.2 in the beginning, and remains stable at 6.6. The membrane is washed for the first time after 27 days, and the water membrane flux can recover 92 %. The period of the bioreactor processing is 26 days.The optimal conditions of decoloration on Direct Blue B2RL are: initial concentration of B2RL is 400 mg·L^-1, the initial biomass is 5 g·L^-1, pH 7.0⁸.0, glucose concentration is 0.5 g·L^-1. Under this optimal conditions, the bioreactor SMBR with E. coli JM109 (pGEX-AZR) has a high capacity for decoloration of B2RL. The decoloration efficiency and COD_Cr degradation rate exceed 90% and reached 62 %, respectively. As in the continuous operation, the biomass remained at about 3.90 g·L^-1. Both EPS and the activity of enzyme change with the biomass. The period of the bioreactor processing is 25 days.