Screening Of High Efficient Bioflocculant-Producing Bacteria And Analysis Of Its Aspects

In the field of water preliminary treatment system, interests are focused on bioflocculant, since it is non-poisonous, non-harmful, and bio-degradeable easily, and there is no secondary pollution produced. Bioflocculant has been used widely in the world and its good flocculating effect has been proved. The bioflocculant producing bacterial strains have been isolated and studied in this thesis.(1) 141 strains from 30 soil samples and active sludge were isolated and purified, and one high effective bioflocculant-producing strain, namedâ… -3, was screened.â… -3 was identified as Enterobacter sp., and has never been reported before.(2) Bioflocculant produced byâ… -3 was determined; the results showed that the bioflocculant was secreted out of the bacteria. The growth curve ofâ… -3 and the bioflocculant producing dynamics indicated that the activity of flocculating increased withâ… -3 growing. When cultivated 24-30 hours, the flocculating rate of bioflocculant got to the highest, and the flocculating rate was 99%.(3) Cheap, convenience culture materia used to ferment strainâ… -3 has been studied. The optimum conditions of flocculant production of strainâ… -3 was determined through orthogonal experiment. The results suggested that the optimum conditions were: 150g/L sweet potato as carbon source, 1.5g/L urea as nitrogen source, the flocculating rate was about 91%; meanwhile, the optimum cultivating conditions was: original culture pH was 9, the culture capacity was 30ml, and rotate speed was 180r/min, and the flocculating rate was 95.5%.The optimum flocculating conditions was: adding 10 ml/L of flocculant ferment liquid, keeping kaolin solution pH 8, then the flocculating rate reached to 98.1%. metal ions such as Na⁺,Ca²⁺,Fe³⁺ solution didn't have any effect on flocculating. Furthermore,â… -3 strain could use domestic animal wastewater to produce bioflocculant, and the rate of flocculating rate was 71.5%; when adding 0.5g sugar into the domestic animal wastewater, the flocculating rate was 87.5%.(4) The chemical composition of bioflocculant was analyzed preliminarily; the results showed that the bioflocculant was consisted of polysaccharides(64.9%), a little amount of proteins(9.1%); and the other components(26%) was not clear.(5) The bioflocculant used to treat rock material wastewater, domestic animal wastewater and the floodwater to remove the suspended substances was studied. The results showed that flocculanting rate was 98.4%, 39% and 99%, repectively; which suggested that bioflocculant have good flocculating effect, and the flocculanting course was fast; hence, the bioflocculant will have broad application prospects in practice.