Studies On The Production And Flocculation Characteristics Of Complex Bioflocculant

Microbial flocculants (MBF) are a kind of special substances with high molecular amount that are produced by microorganisms. They can flocculate suspended solids, cells, and colloidal solids. With the advantages of high efficiency, innocuity and biodegradability, more and more attention has been paid to MBF recently.So far, the research on the MBF has mainly focused on the small scale experiment phase in the lab of screening strains which can produce flocculant and sewage treatment by the fermentation broth, but mostly referred to the single strain and with the problem of difficulty in screening the strains, the high cultivating cost and the unclarity of the flocculation process. Recently, in order to improve the activity of the flocculant and cut down the cultivating cost, complex bioflocculant has been paid more and more attention to.The study firstly screened a single strain which can produce MBF, and in term of the mechanism of Effective Mircoorganisms, the complex bioflocculant with higher flocculation activity than MBF produced by a single strain were constructed. Then the optimization of its cultural conditions and the flocculation characteristics of the complex bioflocculant with best flocculation activity were studied. In the end, the application of the complex bioflocculant in wastewater treatment was examined in the paper.Thirty-seven strains were screened and isolated from soil from campus and active sludge, including twelve bacteria stains, eleven mildew strains, seven epiphyte stains, and seven actinomyces stains. There are 20 strains with flocculation activity whose flocculating rate is above zero(E₂(%)>0) in these thirty-seven strains. In term of the mechanism of Effective Mircoorganisms, the fifteen strains with(E₂(%)>20% were mixed one by one with the same proportion and then were cultured in certain condition. The flocculation activity of the complex bioflocculant that we constructed is much higher than MBF produced by a single strain. The complex bioflocculant with high flocculating rate above 80% are produced by mixed strains XJ12 and ZJ6, ZJ6 and MJ9 and ZJ7 and MJ10, whose flocculating rate are 86.6%, 84.9% and 85.7% respectively. The optimization cultrural conditions of the Complex biofloccultant XZ produced by XJ 12 and ZJ 6 are the cultural time 48-56hours, the cultrual temperature 30℃,the initial cultural medium pH 7.5 and the rotation speed 160rpm.The solid complex biofloccultant obtained is about 0.99g by organic solvent extraction, and the production of complex biofloccultant can be 3.96g/L.The flocculating activated substances distributed mainly in supernatant, which contains protein and amylose. The characteristics of the complex biofloccultant XZ were studied in the paper, it indicated that the complex biofloccultant XZ has the characteristics of high thermo-stability and pH stability. The best flocculating condition is pH 7.0, the dosage of complex biofloccultant XZ to 4.0g/L kaolin suspension 2.0mL/100 mL, the optimization dosage of 1% CaCl₂ 200mg/L.The complex bioflocculant XZ application result indicated that it has a certain removal of the SS and chroma in the domestic sewage and it also can flocculate the sludge, it can accelerate the speed of sludge sedimentation, improve the characteristic of sludge sedimentation and reduce the SV and SVI of activated sludge.