Screening Of Dye-Decolorizing Bacterium And The Conditions Of Dye Decolorization

Among industrial wastewater, dye wastewater from textile and dyestuff industries is one of the most difficult to treat. This is because dyes usually have a synthetic origin and complex aromatic molecular structures which make them more stable and more difficult to be biodegraded. It is reported that there are over 1000 commercially available dyes with a production of over 7 × 105 metric. Among these dyes, azo dyes are the most widely used ,they account for 60% of the total number of dyes structures known to be manufacture. Beause color in wastewater is highly visible and affects esthetics, water transparency and gas solubility in water bodies, and especially because many dyes are made from known carcinogens, such as bezidine and other aromatic compouds . dye wastewater have to be treated.Due to the low biodegradability of dyes, conventional biological wastewater treatment systems are inefficient in treating dye wastewater. Dye wastewater is usually treated by physical- or chemical- treatment process, however ,these technologies are usually inefficient in the removal of color ,costly and little adaptable to a wide range of dye wastewater.In recent years, a number of studies have focused on some microorganisms which are able to biodegrade and biosorb dyes in wastewater, A wide variety of microorganisms capable of decolorizing dyes are reported, and they are some bacteria, fungi, and algae. 17 decolorizing strains screened from the wastewater of the 3th chemical factory of baoding were identified as Bacillus,Kurthia,Corynebacterium^eromnas and Salmonella,Klebsiella. We studied on the decolorizing conditions of these strains and the results showed that:① These strains have a large range of temperature endurance. When the temperature is between 31℃ and 37℃,some strains have the best decolorizing result, such as A,B, C, C3, D3, D4, D5 , D6, E, G, F and HD-1. When the temperature increased, the decolorization rate increased for C2, D1, D2, D7 and when the temperature is 40℃, they have the best decolorizing results.② These strains have some decolorizing ability when the pH is beteen 5 and 9. Different strains have different optimum pH,the optimum pH of A, B, D3, D6 and D7 is 9.0;C1, D1 and D4 is 8.0;while 7.0 is the optimumpH of C2, C3, D5, E, HD-1,G and F.③ These strains are sensitive to oxygen, and oxygen inhibit the decolorization rate.Decolorization of dyes by these strains was typically initiated by azoreductase-catalyzed cleavage of azo bonds. And then corresponding amines were formed. We screened a bacteria J18,identified as pseudomonas,which could grow depending on the Hydroxy phenylamine as the soly nitrogen and carbon sources. We made a bacterial cinsortium by mixing strain H and J18 to investigate the degradation of the intermediate aromatic amine. We found that they are further degraded under aerobic or anaerobic conditions by J18.There are many dyes and all kinds of intermediate in the wastewater. In order to investigate the results of decolorizing dyestuff wastewater, we mixed A, D2, H, G>,HD-1 and J18 to make a consortium to investigate the decolorization rate of mixed dyes and dyestuff wastewater. We found that the decolorization rate was 87.3% and 77.4% respectively; COD(chemical oxygen demand) removal rate was 66.7% and 54.3%,respectively.