Isolation, Identification And Decolorization Study Of The Strain For AZO Dye Decolorization

With the difficulty of dye wastewater treatment increasing, it is significant of isolation of efficient strain for dye decolorization from sludge and soil and its application in projects. An efficient strain S8 with azo dye reactive black 5 decolorization ability was screened from anaerobic sludge of AAO used in printing and dyeing wastewater treatment. It was purified and determined through PCR amplification and 16S rDNA sequence. The growth curve and standard curve of OD-dry weight concentration of strain S8 were drawn. The strain S8 were cultured in different pH, temperature, inoculated volume, broth content, oxygen supply and nitrogen sources, taking OD600 as measurement, in order to study their effect on the growth of strain S8. The experimental results showed that the decolorization rate of strain S8 to RB5 after 25h was 85%, it was identified as Enterobactor, the lag phase of strain S8 was 0-4h, log phase was 4-12h, stationary phase was 12-20h, decline phase was after 20h. The optimal growth conditions of strain S8 were pH 9-10,30℃, inoculated volume 5%, broth content 20%, aerobic condition, peptone as nitrogen source.The decolorization conditions of strain S8 was studied through single factor experiment and orthogonal experiment to fix the optimal combination of temperature, pH, inoculated volume and broth content. Then under the optimal condition, the effect of different external carbon source and nitrogen source, external carbon source concentration, initial dye concentration, salinity and existence of metal ions on the decolorization of strain S8 for RB5 were discussed. The results showed that the optimal combination of basic decolorization conditions was 30℃, pH 6, inoculated volume 8mL/100mL, broth content 100mL/250mL conical flask. The strain S8 could utilized glucose, sucrose, D-fructose, D-galactose and beef extract, peptone, NH4Cl. When the glucose concentration was at 4g/L, the strain S8 had the highest decolorization rate for RB5. The limit of initial dye concentration born by the decolorization system was between 200 and 400mg/L, while the limit of salinity was between 2% and 3%.1.2mmol/L of Mg2+ concentration,2.0mmol/L of Mn2+ concentration and 1.0mmol/L of Ca2+ concentration could maximized the decolorization rate. The low concentration of Fe3+(low than 1.0mmol/L)would not inhibit the decolorization, and the inhibition of decolorization was obvious when the Zn+ concentration was more than 0.1mmol/L.Broad spectrum of strain S8 was studied using azo dyes, anthraquinone dyes, thiphenylmethane dyes and metal complex dyes. The declorization of 16 zao dyes with different molecular structures under anaerobic condition was studied. Adsorption and degradation were studied separately in order to explore the effect of substituent species on the aromatic ring on degradation decolorization. The results showed that the strain S8 had efficient broad spectrum of decolorization for other kinds of dyes.—OCH3 substituted on aromatic ring hindered decolorization,—Cl substituted had no effect on degradation decolorization, both—NHCOCH3 and—SO3H substitutent promoted degradation decolorization, and—SO3H substituted were more easily decolorized than—COOH substituted. Moreover, the existing of heterocyclic and metal ions contained in dye structure enhanced the toxicity of dyes and hindered their decolorization.The high-efficient decolorization strain for Reactive Black 5 was immobilized using calcium alginate embedding method. The optimum condition of immobilization was determined by orthogonal experiment. The effect of influent pH, temperature, initial dye concentration and times of reuse on the behavior of decolorization of RB5 were investigated. The effect of external carbon source concentration and salinity on the treatment effect of stimulated dye wastewater was investigated by dosing immobilized particles. The results showed that the optimum condition of immobilization was sodium alginate(3%), CaCl2(2%) and the ratio of biomass to embedding agent(2:1). The optimum pH and temperature of decolorization were 8 and 30℃respectively. The immobilized pellets had the characteristic of low temperature resistance, high dye concentration tolerance and reuse, but its hardness decreased under the condition of strong base, high temperature and multi-using. The decolorization effect of dye wastewater by immobilized bacterial was better when the concentration of glucose as external carbon source was 1 g/L. The inhibition of salinity on decolorization of immobilized strain was smaller. The addition of immobilized pellets in anaerobic reactors promoted the removal rate of dyes.