| 9 flocculant-producing bacteria have been selected from the activated sludge by screening, with a flocculating rate over 72%. After reselecting, 2 of them were obtained with higher flocculating activity and better stability, named as E-9, A-l respectively. Through the observation of the character of individual form and the colony form, as well as the oxidase and a series of physiological and biochemical experiments, E-9 was identified as E.coli.The best culture conditions of strain E-9 were found by sole factor test ,they are: ethanol as the optimum carbon source, soybean powder as the optimum nitrogen source, with the best concentration 15ml/L,12.5g/L respectively, initial pH 6.0-7.0, 30癈, and 60-72 hours for cultivation, while E-9 is a facultative anaerobic, the ventilation flow can be ignored. For A-l, its cultivation time was 48-60 hours.Ethanol and soybean powder are helpful in flocculation to the microbial-flocculants. When the flocculants produced by E-9 were used to clarify 4g/L kaolin suspension at the dosage of 1ml /L, the flocculating rate amounted to 97-99.5%, while its dose was about 1/15 of the ferment media, its price, about 52%. High flocculation efficiency could be achieved when the pH values were kept in between 5.0-8.0, the concentration of kaolin clay suspension was2-4g/L. Metal ion such as Ca , Mg facilitates flocculation activity of microbial-flocculants, and the available range of Ca2+ is 0.2-0.5g/L.The experimental results showed that the flocculants produced by two strains mainly exist in the supernatant and they were synthesized during the cell growth. For E-9, the growth dynamic curves of flocculating microbial were slightly different from theproduction dynamic curves of microbial-flocculants, which means that the production time of microbial-flocculants tends to lag behind. The flocculants produced by E-9 could be kept without losing activity when the temperature was between 30 and 60 , pH values were in between 2.0-8.0.
|
PDF Full Text Request