| Microbial flocculants (MBF) is a kind of high molecular substance which is producedby microorganisms. It can make good settlement of solid particles, bacterial cells andcolloidal particles which are less settlement in the liquid. The flocculation effect ofMBF is good and easily biodegradable. In addition, it is security, no secondarypollution and attracted widespread attention.Seven strains were screened from sewage treatment plant which had flocculationactivity. Through the test on activity of the fermentation flocculation broth, we foundthat three strains had high flocculation activity, and Preliminary appraisal for:1#bacteria,3#mycete and4#yeast.The results of the study showed that the culture medium composition and culturecondition had important influence on the growth of microorganism. By single factorexperiment and orthogonal experiment to analyze the factors impacted on the growthof microorganism. Results showed that the optimal culture composition and cultureconditions of1#bacteria,3#mycete and4#yeast as follows: Glucose concentrationwas7g/L,15g/L,9g/L;(NH4)2SO4concentration was0.26g/L,0.3g/L,0.24g/L; theinitial pH value was8,7,7.5; the best rotation speed was160r/min and the optimalincubation temperature was30℃,34℃,32℃.Through the analysis of orthogonalexperiments we known that (NH4)2SO4concentration made great effect on thegrowth of1#bacteria and3#mycete while4#yeast was most affected by rotationspeed. Therefore, in the practical application, we should explore the best trainingenvironment of different micro-organisms to ensure the efficient microbial growth.Results of flocculant performance showed that microbial flocculants and CaCl2hadthe best dosage amount. Especially after the addition of CaCl2, the medium of thethree bacteria flocculation rate was greatly improved. Temperature and pH value alsohad certain effect on the flocculation system. Control the pH of the flocculationsystem within the range of7-10, the flocculation rate remained above86%, whenpH>10, flocculant still had certain flocculation activity, but pH<6, flocculation effectwas very poor. In addition, different flocculant produced by different microorganismhad dissimilar sensitivity of the temperature. Study found that the microbial flocculants producd by three strains had good thermal stability and wide application.Through the analysis of the bond between flocculant and kaolinite particles,flocculent form and ultraviolet scanning, we found that the main ingredients ofmicrobial flocculants were protein and nucleic acid substances, combined with ionicand the main role of the flocculation process was chemical bridge league.The test of actual wastewater showed that the microbial flocculant produced by3strains had better removal rate on SS up to90.34%. Before and after the treatment ofwastewater, the CODcr value, chroma value and turbidity values reduced to a greatlevel. |
