The Production Of Microbial Flocculant And The Research Of Its Flocculating Mechanism

With the development of industry and the improvement of the people's living standard, there become more and more strict on the use of water treatment reagent. But all the most popular flocculants now used in water treatment including iron salu aluminum salt and polyacrylamide flocculant inevitably induce to the second pollution. Moreover, the use of aluminum salt and polyacrylamide flocculant would lead to latent threat to people's health. All of these limit the application scope and the development of these traditional flocculant.Bioflocculant is the important sort of the crude macromolecular flocculant. It has such advantages: no toxicity, no second pollution, many sorts of microorganism that can produced bioflocculant, be easy to achieve industrialization through biology engineering, can bio-decompose organic pollutant while flocculate the suspension and colloid.The content of this research include: screening the microorganism that can produce bioflocculant from the microorganism sample, select the best microorganism to optimize its culture condition that can increase the flocculating activity to the utmost; in order to see about his flocculating activity, then using the bioflocculant flocculate the kaolin suspension and compare the flocculating results with the PAC HPAM; On the basis of the bioflocculant has excellence flocculating activity , distill and purify the bioflocculant from the culture mediunu give qualitative analysis of its ingredient and reach its flocculating mechanism.The studies include the enrichment culture of the microorganisms that can produce bioflocculant and their screening suggest that they are broad exist in the soil and active sludge. Screening 13 microorganisms that can produced bioflocculant from 44 strains. In order to do in-depth research, select 1 microorganism and named BF3-3. Its bioflocclant named MBF3-3.The studies of the best culture condition of BF3-3 suggest the best culture condition of BF3-3 including: culture time is 24h, culture temperature is 30,rotation speed 170r/min, the dosage of the culture (in 250ml flake) is lOOml.The gradients of BF3-3's culture medium is: sucrose 40g, sodium nitrate 0.5g, yeast extract 2g, MgSO4 7H2O 0.25g, KH2PO4 0.5g, initial pH 7.5.The studies ofMBF3-3 flocculate the kaolin suspension suggest that the added metal ion can remarkable improve the flocculating effects. The effect of different ions added is: A1C13> MgCl2>CaCl2> NaCl> KC1. BF3-3+Mn+ has good flocculating results at pH: 3.3-7.5, HPAM at pH:3~l 1 and PAC only at pH: 10-11.5 while its effects far below the former two. In actual dosage aspect, BF3-3 is the least, HPAM is the second, PAC's is far more than the former two.The studies of MBF3-3's flocculating activity suggest that the effective component inMBF3-3 is polysaccharide. This polysaccharide doesn't have-COOH, but mainly has -COO-. The flocculating mechanism of MBF3-3 is absorption-bridging. MBF3-3's-COO-increase its solubility and lengthen its available molecular length, thus intensify its absorption-bridging effect.