Studied On The Techonology Of Composite Flocculant Between MBFGA1 And Polyaluminium Chloride

A bacterial strain, numbered GA1, which can produce bioflocculant with high flocculating activity was screened from soil by means of the common bacteria screening and purification method and was identified according to its morphological, physiological and biochemical characters, as well as 16S rDNA sequence homology comparison, and DQ166375 is its GenBank accession and its name is Paenibacillus polymyxa GA1 CCTCC M 206017.The response surface methodology (RSM), involving five factors such as dosage of MBFGA1, polyaluminium chloride (PAC) and CaCl2, pH , top speed of stirring and two responses such as flocculent rate and granularity of floccules, was employed to study the treatment of kaolin suspensions by the compound flocculant of MBFGA1 and PAC, which was produced by Paenibacillus polymyxa GA1, and PAC. The camera was applied to take photographs of the flocs while they move downward in the settling column, and then measured the granularity of floccules by the image analysis software. By response surface analysis, the two quadratic models for the five factors were established with flocculent rate and granularity of floccules as the target responses. The coefficients of determination (R2) equal to 0.7449 and 0.8029 respectively, and indicate that they all have a significant property. The optimal flocculent condition obtained from the two desirable responses, flocculent rate as 100% and granularity of floccules as 0.7mm, which deduced from the frequency of responses, were MBFGA1 dosage of 99.75mg/L, PAC dosage of 121mg/L, CaCl2 dosage of 27mg/L, pH 7.3 and top speed of stirring as 163rpm respectively. The application of Zeta potential measurement and scan electron microanalysis provided a better approach to analysis the characteristic and mechanism under different flocculent conditions, and we can get the conclusion that PAC has more capability on changing the potential of colloid and MBFGA1 is good at absorption and bridge effect. The residual Al concentration and species distribution of the kaolin suspension treated by the compound flocculant was measured using fluorimetry. Results indicated that PAC had the highest concentration of the residual Al which included the total Al concentration at 9.012mg/L and the inorganic mono-Al, the main toxicity-leading species, at 0.392mg/L. However the compound flocculant between MBFGA1 and PAC can efficaciously improve this situation. The concentration of the total Al and the inorganic mono-Al reduced to 59.1% and 44.6% respectively compared with using PAC only. The compound of two kinds of predominance makes a significant sense on enhancing flocculent rate, reducing flocculent costs and decreasing secondary pollution.