Selection Of High-Effective Decolouring Bacteria And Research On Decolourization Of Azo Dyeing Wastewater

Among industrial wastewater, dyeing wastewater from printing and textile industries is one of the most unmanageable wastewater. The reason is that dyes usually have a synthetic origin and complex aromatic molecular structures, which are hard to biodegrade. In recent years, it is reported that there are over 1000 kinds of commercially available dyes with a production of over 7×10~5 ton. Among these kinds of dyes, azo dyes are the most widely used, they account for 60% of dyes known to be manufactured.Considering dyeing wastewater containing Reactive Black 5(RB5) as the subject in the study, which is belong to azo dyes, 10 high-efficient decoloring strains are separated under aerobic condition when the other 10 strains under anaerobic condition. Thereamong, No.16 strain and No.19 strain have higher decolorization capacity. No.16 strain is further screened as the optimal decoloring strain. On the basis of the configuration and physiological and biochemical characteristics of the strain, the strain is primarily identified as Rhodopseudomonas palustris by way of introducing conventional bacterium assessment method. The bacterial 16S rRNA gene sequence analysis of No.16 strain shows that it is most close to the standard strain of Rhodopseudomonas palustris with 97% of identity. Therefore, the No.16 stain is certain to be Rhodopseudomonas palustris, it is named as Rhodopseudomonas palustris W1.The research shows that strain W1 decolorize Reactive Black 5 by means of biological co-metabolism. Sodium lactate is the optimal additional carbon resource of the study, the optimal concentration is 2g/L. Ammonium chloride is the optimal nitrogen resource, the optimal concentration is 1g/L. Strain W1 has a adaptive and resistive capability of pH and salinity in environment. It can keep the higher activeness of decolorization and degradation under light anaerobic circumstance of pH 5~10, dark aerobic circumstance of pH 6~11 and circumstance of high salinity. Most of dyes can be decolorized by the stain. However, COD of wastewater is degraded with worse efficiency by strain W1, we can introduce photosynthetic bacteria/activated sludge process to improve the efficiency of COD degradation.According to the analysis of UV-Vis absorption spectrum and LC-MS spectrum, the decolorization mechanism of Reactive Black 5 is mainly that cracking reaction, which produce aromatic amine as an intermediate product, happen on the azo-bond of dyes. Decoloriztaion of Reactive Black 5 was first order kinetics when initial concentration of dye ranged from 50 to 500mg/L under light anaerobic condition. The correlation between specific decolorization rate and initial concentration of Reactive Black 5 can be interpreted by Michaelis-Menten model. The Michaelis constant Km=348.20mg/L and the maximum specific decolorization rate Vmax=80mg/(L.h).