Study On The Specificity And The Cationic Modification Of Co-carbon Bioflocculant Produced By Klebsiella Sp.NIII2

Microbial Flocculation is a kind of large molecules secondary metabolites, which is produced by microorganisms in the process of grow. With the advantages of non-toxic,no secondary pollution, the high flocculating activity, easily biodegraded, thus there is a broad application prospect in the fields of wastewater treatment. A problem which needs to be settled is how to improve the fermentation stability of the microbial flocculation produced by Klebsiella sp. NIII2, yield and its activity. In order for the above purpose,this paper launches the related research work, which has the practical significance.Using the co-carbon source fermentation to make the microbial flocculation have a high yield and high activity with the analysis instruments of infrared spectrum,scanning electron microscope, laser particle size analyzer tester, Zeta potential meter,algae and so on, This thesis studied the structure and performance relation of the glycoprotein flocculation produced by Klebsiella sp. NIII2, and modify the flocculation produced by Klebsiella sp. NIII2 though the cationic modification method. The results of the studies got as follow:(1) The co-factor source of succinic acid, acetic acid, lactic acid is good to improve flocculant production and performance because it is easy to make Klebsiella sp. NIII2 produce base. The succinic acid is significant of the base production, make the yield and carbon conversion rate of the microbial flocculation improved to 10.37 g/L and 43.48%;With the calcium ions, the microbial flocculation of 8.0 mg/L has a removal of 97.3% to kaolin SS. The high protein/sugar ratio(33%), high content of sialic acid and high molecular degree of polymerization is the main reason to guarantee its highly active.(2) When Klebsiella sp. NIII2 takes advantage of co-factor source fermentation the medium optimization results of its high yield is as follows,: With 20 g/L sugar, 5 g/Lsuccinic acid, sodium nitrate(nitrogen source) 2.5 g/L, sodium sulfate(sulfur source) 48mg/L, magnesium ion concentration 2.0 mmol/L, adjusting the initial pH to 7.5, the yield can be up to 10.87 g/L in harvesting microbial flocculation of the 72 h fermented liquid fermentation. The glycoprotein ratio of the microbial flocculation is up to 35%under the optimization condition.(3) With Klebsiella sp. NIII2 producing the glycoprotein microbial flocculation,the shortage of magnesium ion can significantly reduce the production, its glycoprotein ratio and activity; Sulfur source is also an important factor, the influence of sulfur oxidation state is good for producing highly active flocculation.(4) The cationic modification conditions of the glycoprotein microbial flocculation produced Klebsiella sp. NIII2 is for: 10 g dry microbial flocculation, 0.015 mol cationic etherifying agent(CTA), CTA and sodium hydroxide mole ratio of 1.2, 20% water,70 ℃ reacting for 2 h. Under this condition, the Zeta potential of the cationic modifying flocculation is up to +31.5 mV. Without the coagulant, the cationic modifying flocculation of 4 mg/L can make 2 g/L kaolin samples clear, be increased by38% compared with no cationic flocculation to SS removal rate, and the burden of high electricity algae also have a good processing effect.