| The Saccharomyces cerevisiae is used as a microbial flocculant producing bacteria. A high active bacterial colony one has been screened by culture, enrichment and activities testing, and its flocculating properties, chemical composition and flocculating mechanism were researched.The experimental results are shown that the best culture time is between 3 and 4 days, and flocculating is 30min. For a testing solution of 50ml, the suitable amount of microbial flocclulant is 2~4ml, and flocculating ration can be up to 88.4%. CaCl2 can promote the flocculating activity of MBF. The best pH values of water sample is 7~10. Activity of MBF was still higher after heating at 30℃~ 80℃in water, so MBF possess good thermal stability.MBF can partially remove suspended matter in domestic sewage, and the flocculating ratio was attained to 62.4%. The highest flocculating ratio against Cr(Ⅵ)in wastewater is 82.3% when its initial concentration is 100mg/l.Elementary analysis indicates that the element proportion of C:H:O:N:S in MBF is 262:386:124:34:1, which contain some carbohydrate. The analysis results of charge effects,ionic bond and physiological structure proved that MBF has good flocculation when the water is neutral or weak alkaline. Because MBF is sensitive to some chemical reagent, it can be thought that MBF and kaolin are connected by ionic bond. It indicted that there is adsorption bridging action in flocculating process. Ca2+ accelerates bridging adsorption action, and promotes the flocculating activity of MBF .So the functionary mechanism of MBF is mainly adsorption bridging action.
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