Study On The Production And Characterization Of Bioflocculant From Dehydrated Sludge

The bioflocculant which is a kind of new natural organic compounds with high molecular weight is highly valued by scientific world due to it's efficiency,harmlessness and safety.Many kinds of bioflocculants had been discovered,however, high cost culture medium limited bioflocculant's large-scale production,so lowering production cost effectively was a important problem during the bioflocculant's industrialization progress.On the basis of systematically and completely discussion about present condition and development of the bioflocculant's production around the world in recent years,this thesis thoroughly explores the producing conditions,flocculating properties,structures,constitutes,mechanism and application of bioflocculant extracted from dehydrated sludge by ultrasonicatio,cold ethanol precipitation and freezing desiccation.The contents and conclusions was as follows:The best producing conditions were 100 g/L sludge concentration, 5 mL sludge volume, sludge pH=11, 1 s-3 s work time, 1 s-2 s intermission time, 15 minite whole ultrasonic time. High disruption rate could be achieved when deionized water was played as solvent。The best separating conditions of JT06 were two volumes acetone precipitation.The bioflocculant could be found inside and outside the cell of dehydrated sludge bacteria, the inside was more than the outside. The partial properties measurement results indicated,the bioflocculant own high storage stability,hot stability and pH stability. The results also indicated,the production rate of crude products was 30 mg/g sludge.High flocculation efficiency against kaolin clay suspension could be achieved when the pH values were kept between 1.0 and 4.0, the flocculating activity could be over 97% when no flocculant aid was added. The flocculating activity was stimulated to different extents in the presence of 10 g/L Fe³⁺, Al³⁺, Ca²⁺, Mn²⁺, Zn²⁺, Mg²⁺, Fe²⁺, Na⁺and K⁺.Fe³⁺ and Al³⁺ play a better role of flocculant aid. There was specific relation between the dosage of flocculant and metal ion's concentration, the flocculating activity was enhanced with the increase of flocculant dosage and CaCl₂ concentration.The bioflocculant has a high removal ability to the heavy metals ion chrome;it could be used in suspension such as soil suspension,fine activated carbon suspension,kaolin clay suspension with high flocculating rate;it could be also used in orgnic wastewater such as fish meal wasttwate,cotton liquid with high COD removal rate.