[Flocculating capability and mechanism of bioflocculant produced by Paenibacillus polymyxa GA1]

MBFGA1, which was produced by Paenibacillus polymyxa GA1, was used to investigate its flocculating capability in the following waste water, the liquid of kaolin, soil suspended liquid, coal-washing wastewater and the landfill leachate with orthogonal experiments, the inspection of granularity and the scanning electron microanalysis. Meanwhile the anthrone reaction and infrared spectrum are also applied to identify its main component. In the optimal flocculating conditions obtained from the orthogonal experiments, the flocculating rates of the liquid of kaolin, soil suspended liquid, coal-washing wastewater and the landfill leachate were 99.53%, 99.50%, 98.2% and 75.60%, respectively, and the sedimentation velocities of the above four kinds of flocculants were 0.03 m/s, 0.025 m/s, 0.025 m/s and 0.005 m/s, respectively. In addition, the distribution of granularity has changed after flocculation. The size of the average granularity of soil became bigger after flocculation, and reached over 10 microm, but for the other three kinds of granularity just the opposite phenomenon has occurred, and their sizes were all less than 10 microm. From the photos of scan electron microanalysis of four types of granules, it could be drawn that there were no obvious differences in the appearance. It was the same adsorptive mode between MBFGA1 and different flocculating particles, that is the function of electrovalent bond, tested by EDTA, HC1 and urea. The main component of MBFGA1 was polysaccharide, which was determined by anthrone reaction, and it contained a lot of carboxyl and hydroxyl groups examined by infrared spectrum analysis. From the above results, it could be presumed that MBFGA1 can be the best flocculant for the granule-highly-concentrated waste water and the dominative flocculating mechanism of the flocculant was mechanism of adsorption-bridge.