Screening Of A Microbial Flocculant Producing Strain And Study On Its Flocculating Property

Microbial flocculant is the use of biotechnology.which comes from microorganisms or their secretions of extraction, purificationtion to get a safe, efficient, a new type of water treatment agent and natural degradation. Including the use of microbial flocculant of cell wall extracts,and the use of flocculant, microbial cell wall metabolism products directly obtained by flocculant flocculant and cloning of microbial cells. Flocculant substances produced by microorganismsmostly consists of glycoprotein, mucopolysaccharide, protein, cellulose, DNA and other polymers,.In most cases the relative molecular weight is more than 105. The most accepted mechanism of flocculation is hydrogen bond, ionic bond bridge theory which thinks that the flocculant molecular with hydrogen bond, ionic bond and Fan Dehua force, the particles are close to each other, net bridge structure stable precipitate formed between the particles, to get the flocculation completed.Secondly are the electrically neutral theory and the mechanism of chemical reactions. Influence of specific flocculant and colloidal particles, composition, structure, conformation and charge of various reaction conditions on them is very important. The flocculation effect is mainly affected by the following characteristics:flocculant, the surface charge of colloidal particles, reaction temperature, pH and metal ions in the reaction system.(1) We isolated strains of flocculant producing microorganism, from the river sludge and paper mill sludge in sewage outlet. We identified as aeromonas by morphological physiological and biochemical characteristics identification, and named it as 2-19.(2)The growth regularity and flocculating activity was associated positive. Freeze drying product flocculant 0.065g from 100mL fermentation liquid,named WK2-19. Using phenol sulfuric acid method, carbazole reaction, Coomassie brilliant blue protein staining respectively analysis of flocculant in crude polysaccharide content, the content of uronic acid, protein content, the results were 65.8%.16.7%,4%,. The main components of flocculant is the possession of a small amount of polysaccharide, protein ratio. By Fourier transform infrared spectroscopy analysis of the functional groups. We find that it has the typical carbohydrate derivatives the C-O.absorption peak of-NH bond in glycoprotein. In addition to the main functional groups.it contains of C-O,-OH,-NH, C-H,=CH2 and CH3 etc.(3) In order to obtain high flocculating activity,we delelop the single factor experiment on flocculation system:the flocculant dosage is 4mL, the most suitable condition of flocculation is, stirring speed 250r/pm, stirring time 5min, reaction temperature 30 C, the optimum pH is between 6-8. CaCl2 is the most suitable coagulant, adding 2% CaCl2 flocculating activity reached the highest 89.7%. As a test of different cationic coagulant Mg2+, Ca2+, Al3+, Cu2+ has a promoting effect on the flocculation process.