The Development And Application Research Of Microbial Flocculant

Based on the research results of our subject, the developmental research of the substitutive medium for the flocculant-producing strain Aspergillus M-25 has been carried out through a series of experiments, and a substitute of medium has been developed. When the fermentation liquid of the substitute is used to clarify Kaolin suspension (4000mg/L), the flocculation efficiency can reach 99.5%, topping the czapeksmedium by 2.5%, and the cost of medium reduce 54.1%.We have investigated the influence of sterilization or not on the producing of flocculant by M-25. The results indicates that, even if no sterilization, the flocculation efficiency still can reach 91.7%, and the producing rate of flocculant is 0.65g/L, just 0.12 g/L lower than that of under the sterilization condition. The flocculation efficiency is changing basically, and above 97% after enlarging the scale of shaking bottle sterilization culture of strain M-25 from 50mL to 500mL. This proves that strain M-25 has a good enlarging ability cultured in shaking bottle.The results of hemicontinuous culture experiment of the strain M-25 show that the flocculation efficiency of the fermentation liquid is above 91% in the first four times of updating the medium, from the fifth time, the flocculation efficiency begin to drop rapidly. After adding proper amount of spore (a ring/100mL) into the shaking bottle while updating the medium, the flocculation efficiency can be steady and above 90%.The extraction experiment of the microbial flocculant (MBF) has been carried out by acetone sediment in the low temperature, and the extraction rate is 0.77g/L. However, there is a disadvantage of serious flocculating activity losses by this method. So we explored another method of preserving the fermentation liquid directly: Regulating the pH of fermentation liquid between 1.0 and 2.0, sealing and keeping it in photophobic at the normal atmospheric temperature. Applying the microbial flocculant to deal with wastewater of sauce factory, pharmacy factory, and municipal sewage, the removal efficiency of COD can reach 77.5%, 66%, and 80.4% respectively. After mixed with Al2(SO4)3, the removal efficiency of COD can reach 79.8%, 76.7%, and 90.8% respectively. Finally, to improve the treatment efficiency of the enhanced primary treatment technics of municipal sewage, the strain M-25 has been put into the sludge of the enhanced primary treatment. The experimental results show that the average removal efficiencies of COD, SCOD, SS of the technics added the strain can reach 63.7%, 35.2% and 74.2%, improved respectively by 9.2%, 7.2% and 12.6% than the ordinary technics, and the technics added the strain has a greater ability of shock-resistant than ordinary technics. This proves the strain can acclimatize itself to the enhanced primary treatment technics of municipal sewage, and enhances the action of microbial flocculation-adsorption and improves the treatment efficiency. It is verified that the strain M-25 could produce a certain amount flocculate materials when cultured not under the specified conditions, and play the function of flocculating and subsiding. This offers a new way for the application of the microbial flocculant of M-25.