| Bioflocculant is a kind of biological metabolic substance produced by microorganism which has the ability of flocculating. Its main components are glycoprotein, amylum, protein, cellulose, DNA etc. Bioflocculant is efficient, nontoxic, biodegradable readily and without pollution to the environment. The studies of bioflocculants are gaining more and more attentions.1. We detected the change of microbe quantity of sewage basin, aeration basin, sewage preliminary basin, sewage effluent and activated sludge in Hohhot sewage disposal plant. Microbe quantity was activated sludge, aeration basin, sewage basin, sewage effluent, sewage preliminary basin from more to less. Bacterium is dominant in Microorganism.2. We selected 10 strains with high flocculating activity from Hohhot sewage disposal plant.Two strains of them with higher flocculating activity were do further research and named as X-1 and X-2. X-1 and X-2 were considered as Klebsiella sp. by assaying physiological and biochemical characteristics and 16SrDN A sequence.3. Glucose was the best carbon source of X-1 and X-2, X-1 was 20g/L and X-2 was 15g/L. Beef extract was the best nitrogen source of X-1, when 0.5g/L it had the highest flocculating activity. Other optimum cultural conditions of X-1 were:K2HPO4 5g/L, KH2PO4 2g/L, NaCl 0.1g/L, MgSO4 0.05g/L, KNO3 0.2g/L.The initial pH value of the medium was adjusted to 7.5, and the strain X-1 was cultured at 30℃and shaken at 160 r/m in a rotary shaker for 32 hours.Yeast extract was the best nitrogen source of X-2, the best dosage was 1.0g/L.Other optimum cultural conditions of the strain X-2 were:K2HPO4 3g,KH2PO4 2g,NaCl 0.1g, MgSO4 0.2g, FeCl2 0.1g in 1000mL distilled water. The best condition for X-2 were:the initial pH was 7.5, Temperature was 30℃, and shaken at 160 r/m in a rotary shaker for 6 hours.4. We studied some biological characteristics of the two strains. X-1 and X-2 were gram-negative bacteria.In the X-1's growth cycle, the highest rate of flocculation appeared in stable phase,32h cultured. In the X-2 growth cycle, the highest rate of flocculation appeared in logarithmic phase, that is, when cultured 6h.5. X-1 could play the highest flocculating activity and its flocculating rate was 93.57%, when 0.5% kaolin suspension system in 100mL. And pH was 8, the temperature was 25℃, to add 800μL 10% CaCl2 as coagulant,32h cultured of the 600μL X-1 fermenting liquor,150r/m lmin,50r/m 2min, standing for 30min.When pH of the kaolin suspension was 7, the reaction temperature was 25℃,10% CaCl2 was 600μL, the amount of X-2 liquid was 500μL 6h cultured, stirring the same way as X-1 for the X-2, flocculation rate of X-2 was to 92.82%,that was the highest flocculation rate of X-2.6. After centrifugation, we found that the flocculating activity of substances of X-1 and X-2 both mainly existed in the supernatant. The flocculants produced by X-1 and X-2 relatively had high thermal stability, as the temperature increased the flocculation rate decreased slightly. To a certain extent, times of bacteria passages and storage time had effect on the flocculation rate. The more passages bacteria were, the lower flocculating activity was. The longer preservation species was, the lower flocculation rate was.7. We found that X-1 and X-2 acted on sewage together, sewage disposal consequence was better than X-1 or X-2 acted alone.
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