Preparation Of Microbial Flocculant With Dairy Wastewater And Its Research For Sludge Dewatering

With the rapid development of the global economy, the attendant environmental problems are becoming increasingly prominent. So it has aroused much attention from researchers to find a green flocculant for wastewater treatment. Microbial flocculant as a new green flocculant, which refers to a class of polymers secreted in the process of the microbial growth and metabolism, which can make the tiny particles in sewage be agglomeration, sedimentation. And compared with other traditional flocculants, microbial flocculant has the advantages of non-toxic, harmless, no secondary pollution, biodegradable. Now the study of microbial flocculant is still in its infancy, although researchers have found a lot of microbial flocculant producing bacteria and these microbial flocculants produced excellent performance, but high production cost and low microbial flocculant flocculation still limits its large-scale industrialization.This paper use a variety of media, a variety of samples to streak microbial flocculant producing bacteria and finally a mixed microbial flocculant were obtained. flocculation of kaolin suspension by the flocculant is more than 80%. The resulting liquid microbial flocculant is purified and dried to obtain a solid microbial flocculant pure extract, this purified microbial flocculant components were analyzed by forensic analysis, suggesting that the ingredients may sugars, proteins, or a mixture of carbohydrates and proteins.The carbon source was partially replaced by dairy wastewater for the microorganisms producing flocculants, and conditions of the microorganisms to produce flocculant were optimized. Firstly, transforming carbon, nitrogen, cations to determine the optimum nutrition. Followed by changing the initial p H value of the medium, temperature, speed, inoculum and when dairy wastewater as carbon source, the added amount of ethanol, Using liquid culture measure its flocculation rate of kaolin suspension to determine the best culture conditions. The results showed that the bacteria can produce flocculant using dairy wastewater as carbon source, the best nitrogen source was peptone, the best cation was a monovalent cation Na+. The best culture conditions were as follows: initial p H of 11.0, temperature of 30 ℃, speed of 160 r / min, inoculum of 2%, adding more than 2% ethanol. The flocculation activity can be up to 94.68%.By measuring changes of zeta potential in kaolin suspension before and after adding the flocculant, inferring electrical neutralization exist in this test.Microbial flocculant have a certain effect for sludge dewatering. Adjusting the p H of the sludge to be 1-12, adding the prepared flocculant, and it was found that when p H was 1-6, the resistance of the sludge decreased with the increasing of the p H, when the p H value is 6-12, the resistance of the sludge increased with increasing of the p H. The best p H for sludge dewatering is p H=6.0. On this basis of the optimum p H, adjusting the adding amount of the microbial flocculant and coagulant Ca Cl2(1%,w / v). The results showed that for 25 m L sludge, p H = 6.0, the added coagulant Ca Cl2(1%, w / v) of 3m L, the added microbial flocculant of 4m L, dewatering effect of the sludge was the best. And under the same conditions, when the adding amount of chemical polyacrylamide flocculant was 4m L for dewatering, the effect of sludge dewatering by microbial flocculant is very close to the traditional polyacrylamide flocculant.