| Azo dye is the most widely used dye in textile and dyeing industry. Azo dyes and its metabolins usually are carcinogenic, teratogenic and mutagenic, which has made a great danger to nature and human survival environment. Bacterial, which was considered to have an exuberant fertility and strong adaptability, shows bright prospect in application of textile and dyeing wastewater treatment.Through isolating by the gradient plate, we got a strain named RB5-M1 which has good decolorization ability. According to its morphological, physiological characteristics and the analysis of 16S rRNA gene analyses for strain identification,>99.86% of gene sequences in isolated strain RB5-M1 were similar to Aeromonas hydrophila compared to available gene sequences in the NCBI BLAST gene bank. Added 10 mL bacterial culture solution into 90 mL Dye-BPA medium, and cultivated in anaerobic cultural incubator (nitrogen 85%, carbon dioxide 6%),35℃, pH 8.0. The measurement of decolorization rate showed that decolorization rate performance is 94.1% for average value,99.8% for maximum value. The strain RB5-M1 can decolor reactive black 5 at 20-40℃, pH 5.0-9.0. The optimum conditions are 35℃, pH 8.0. What's more, the strain can also adjust pH value of environment and reduce pollution.When we cultivated RB5-M1 in anaerobic cultural incubator (nitrogen 85%, carbon dioxide 6%), for the first 24 hours, decolorization rate increased fast, and it was much better than in static culture and aerobic culture. For the second and third 24 hours, decolorization rate in static culture increased rapidly; after 72 hours, decolorization rate in static culture approximated the decolorization rate in anaerobic culture. From an economic cost consideration, if we can design the appropriate reactor, using this strain by static fermentation, it probably achieves the desired results as anaerobic fermentation, with the significant cost savings.When initial concentration of reactive black 5 is 50 mg/L, the growth of RB5-M1 hardly delay, the OD600 at 6h is 0.313; if initial concentration of reactive black is 200 mg/L, the lag phase will be 12h; if initial concentration of reactive black is 300 mg/L, the lag phase will need nearly 60 h. When initial concentration of reactive black 5 is 50,100,150,200,250 mg/L, kinetic processing of decoloring highly corresponded with the Monod zero level reaction model, the relative coefficient R2 is 0.9878,0.9725,0.9465,0.964 and 0.902, respectively. When initial concentration of reactive black 5 is 300 mg/L, the relative coefficient R2 of Monod zero level reaction model is close to R2 of Monod 1st level and 2nd reaction model, kinetic processing of decoloring may highly corresponded with the Monod 1st level reaction model.When stain RB5-M1 was immobilized at the condition of 30℃cooling temperature, PVA: Sodium alginate equals to 10:1,2% concentration of CaCl2,0.2% concentration of gelatin, it could form immobilized globules with higher mechanical strength and embedding biomass. When stain RB5-M1 was immobilized at the condition of 2% concentration of CaCl2,0.3% concentration of gelatin, PVA:Sodium alginate equals to 9:2,20℃cooling temperature, it could form immobilized globules with lower leakage biomass. Meanwhile, result of experiment in SBR (Sequencing Batch Reactor) confirmed the conclusion about immobilization conditions.The immobilized globules can reapply 10 times while the decolorization rate is higher than 61%, leakage biomass is less than 24.53×107 cells/mL. Immobilized globules are active in the first 30 days; decolorization rate is more than 80%. When the immobilized globules were stored more than 30 days at a low temperature (4℃), do the decoloring test immediately, the decolorization rate will be about 65%. The removal of COD, TOC and decolorization rate of reactor C1 and C2 are worse than C3. Thus it can be seen immobilized advantage decoloring bacteria to enhance the SBR process has a bright prospect in application of textile and dyeing wastewater treatment. |
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