Research On Producing Bioflocculant By Biogas Slurry And Its Application In Removal Of Heavy Metal Ions

Microbial flocculants get more and more attention in the water treatment becauseof its many advantages. However, the expensive medium severely restricts thedevelopment of its industrialization. In this study, a certain explorations were taken tosolve the problem of high cost of medium. The study selecting biogas slurry as cheapalternatives, on the basis of comprehensive analysis on its water quality, and through theappropriate adjustments to make the biogas slurry to be the suitable medium forflocculants-producing bacteria to grow. Optimize the fermentation conditions. Finallyexamines the flocculating agent for the decontamination of efficiency. Achieve the lowcost of medium, and at the same time, provide a new approach for the biogas slurryresource utilization.Based on the biogas slurry water quality analysis, we found that the nutrients canbe directly used by flocculation bacteria were in low concentration, and found thatdirect use biogas slurry to produce bioflocculants is not ideal, so some pretreatmentwere needed. Researches show, after centrifugal treatment, without dilution addeddirectly2g/L glucose、5g/L K2HPO4and2g/L KH2PO4and after high temperaturesterilization, the biogas slurry inoculated F+to produce MBFs (Microbialflocculants)can get the flocculating rate more than80%.Monitoring the bacteria growthand the substrate utilization in the biogas slurry medium found that flocculant producingbacteria grew in good condition in the medium and they can make full use of biogasslurry plus and itself contains nutrients. Through the quality of glucose, protein, fourkinds of volatile acid determination, found that these substances can be made full use ofby flocculant bacteria.The biogas slurry acted as fermentation medium, the environmental factors in theprocess of fermentation were studied. Firstly, by single factor experiment the change ofenvironmental factors were determined. Then, use response surface method based oncenter spin combination design (CCD) of experimental design to optimize reactionconditions. Got the regression equation whose response values is flocculating rate,analysis of variance showed that the fit of the equation is good, and the equation canexplain the experimental data well. Through the derivation of the equations, obtainedthe optimum fermentation conditions that flocculant producing bacteria F+using biogasslurry as culture medium: fermentation temperature was29.5℃、the medium initial pHwas7.5、inoculation quantity was8.5%、fermentation time was23h and the table speedwas140r/min, under this conditions we can get the flocculant rate of87.13%, theflocculant production was2.21g/L.Obtained biological flocculants was applied to simulative electroplating wastewater containing high concentration of heavy metals, Cr6+、Cu2+and Ni2+、Zn2+four kinds of heavy metal ions removal rate and adsorption unit were studied. Theresults showed that Cu2+and Zn2+has a high removal rate, more than90%; The abilityof removing Ni2+was general, the highest removal rate was66.4%; For the removaleffect of Cr6+was the worst, the removal rate was under40%. Flocculant dosage、pHvalue、reaction time and reaction temperature the four factors were studied, got theirsuitable scope.