Research Of Flocculating Characteristic And Application Of An Aerobic Denitrifying Bacteria CDN1

In recent years, because of the security risks of traditional inorganic and syntheticorganic polymer flocculants in water treatment, people try to find new flocculants which aresafety, non-toxic, efficient and broad-spectrum.And as a member of them, microbialflocculants attracted more and more attention in water treatment.Objective: In preliminary work, an aerobic denitrifying bacteria CDN1was screened andfound that it could produce extracellular polysaccharide, and had good effect in kaolinflocculating. In this study, we studied the best culture conditions of this strain to produceflocculants, purificated the produced flocculants and analysis them, and investigated theflocculation mechanism as well as the influencing factors of flocculants.Methods: We studied the optimal culture conditions of strains CDN1by single factor(ventilation, temperature, medium initial pH, carbon source, nitrogen source, carbon andnitrogen ratio) in producing flocculants; analyzed the distribution of flocculants in thefermentation broth through separation measured flocculation and bacterial cultures, and thenextracted crude product of flocculants by centrifugation, enrichment and Alcohol precipitation;determined the composition of the flocculants by using the method of Molish reaction,anthrone reaction, ninhydrin reaction, the ultraviolet-visible wavelength scanning; detectedthe concentration of sugar by using Phenol-sulfuric acid method; and detected theflocculants’ flocculation mechanism by using pH adjusting pH and EDTA solution; alsoinvestigated the impact factors to flocculation by transform water environmental pH,temperature, flocculants dosage, metal ions and their concentration; detected the removal ofSS, COD, TN by cast flocculants, and add bacteria which product condensate to the sewage.Results: The optimal incubation time of strain CDN1producing flocculants is18h, andthe optimal culture conditions: culture temperature is37°C, medium initial pH is7.0,shaking speed is150r/min; the best carbon source is glucose, the best nitrogen source isyeast powder; suitable carbon and nitrogen ratio is20-40. The main component of BF-DN1are polysaccharides and nucleic acids, in which polysaccharides accounted about55%, theflocculated material mainly distributed in the supernatant of the fermentation broth.Flocculation mechanisms: BF-DN1molecular coagulant by Ca2+bridging role in ionicbonding combined with kaolin particles form of floc and then occurred flocculation andsedimentation. The optimum pH value of the water environment is7, it has good flocculationeffect at room temperature, but when above50°C, the flocculating activity decreased. Theoptimum dosage is125mg/L; calcium is the best of the flocculants coagulant aids ions, theoptimum dosage of it is0.05%(mass ratio). As for treatment sewage, the removal rate of SSis25.3%, TN is24.6%, and COD value is16.2%. When stirring at different times, as thestirring time increases, the indicators of the water has declined, but the magnitude is too smallto prove the flocculants producing bacteria to take advantage of the organic matter in the growth of domestic wastewater solution, at the same time turbidity also reduced accordingly.Conclusion: The strain CDN1is a multifunctional water treatment bacteria which candenitrification and producing flocculants. If we can develop this strain more, it will adapt tothe wastewater treatment more.