Screening Of High Efficient Bioflocculant-producing Azotobacter And Research Of Its Characteristics

In this experiment,the flocculant ability of 48 dizotrophic bacterial strains was screened,and the growth condition,characteristics and practical application of the high efficient bioflocculant-producing strains was performed,the results was as the follows:Of all the 48 dizotrophic bacterial strains,14 strains had obvious flocculation effect in the primary screening experiments.From those azoterbacter strains,tow high efficient bioflocculant - producing strain,i.e.HY1141 and HY241,were obtained.After determination of the optimal carbon and nitrogen source,the optimal medium and culture condition of the tested strains were screened by an orthogonal test,respectively.The results showed that the best carbon and nitrogen source of HY1141 was sucrose and N2, respectively.The optimal medium consisted of sucrose 5g/L,KH₂PO₄ 1.5g/L and MgSO₄ 0.6g/L.The optimal culture condition included rotation speed 150 r/min,culture temperature 35℃,and original medium pH 7.0,culture time 36 h.Under this condition,the highest flocculating rate of flocculants produced by HY1141 to Gaoling clay suspension is as high as 96.4%.The best carbon and nitrogen source for strain HY241 was sucrose and(NH₄)₂SO₄, respectively.The optimal medium consists of sucrose 5g/L,(NH₄)₂SO₄ lg/L,KH₂PO₄ 1.5g/L arid MgSO₄0.5g/L.The optimal culture condition included rotation speed 180 r/min,culture temperature 30℃,original medium pH 7.0,culture time 48 h.Under this condition,the highest flocculating rate of flocculants produced by HY241 to Gaoling clay suspension is as high as 96.6%.Results of flocculant performance showed that flocculating activity of two strains were extracellular metabolites,the bioflocculant has good acidic stability and thermal stability. Bioflocculant produced by strain HY1141 had good effect on dealing with acidic wastewater, while,Bioflocculant produced by strain HY241 had good effect on dealing with both acid and neutral wastewater.When treating the wastewater,the optimal quantity of the bioflocculant produced by HY1141 and HY241 was 4mL/L;the concentration of CaCl₂ added was 0.5% and 1.0%,and the proper flocculating time was 5 min and 10 min,respectively. The chemical component of the bioflocculant was analyzed;the results showed that the major component of bioflocculant was polysaccharides.In practical application,the bioflocculant produced by two strains had good effect on dealing with source water,and that produced by HY241 had the best effect.When treating source water,its flocculating rate reached to 92.8%,and COD removal rate reached to 85.0%.In addition,both bioflocculant had good effect on dealing with floods and Flotation wastewater, and HY1141 strain had better effect on treating the floods than HY241.The mixed bioflocculant had good effect on dealing with Flotation wastewater.Finally,the taxonomic position of the two strains were determined,the results suggested that HY1141 was identified as azotobacter sp.,and HY 241 was identified as enterococci sp..