Study Of Bioflocculant Excreted By Aspergillus Sojae Cultivated By Waste Water

Bioflocculant is one kind of secondary metabolite excreted by some microorganisms that has the characteristics of high flocculation effect, nontoxicity and degradability. In recent years, the study of bioflocculant has become a popular topic. The key research of this paper involved two aspects as follows: 1, Low-cost culture media such as bean curd-farm wastewater were applied to culture Aspergillus sojae. 2, Bioflocculant excreted by Aspergillus sojae was applied to the field of dewatering sludge. The purpose of research was to reduce production cost of bioflocculant and to broaden the application scope of bioflocculant.Among semisolid medium, extract medium of low-cost substrate, waste-water medium, the cost of waste-water medium was lowest but its culturing effect was best. Sauce waste water, beer waste water, rice vermicelli waste water, bean curd-farm wastewater, mixed waste water by beer wastewater and bean curd-farm wastewater, mixed waste water by bean curd-farm waste water and rice vermicelli waste water were all suitable to culture Aspergillus sojae, and the highest flocculation rates for their cultured supermatant were 69.7%, 76.8%, 90.1%, 98.9%, 96.5%,99.1%, respectively. Specific resistance experiments showed that bioflocculant had a better dewatering property for excess sludge than polyacrylamide. The moisture content of filter cake from dewatering sludge by bioflocculant was 81.77% and the turbidity was 0.78 NTU. The number of moisture content was 1.02% lower than PAM's and 8.05% lower than blank control sample. The results of acute toxicity test and accumulative toxicity test showed that bioflocculant excreted by Aspergillus sojae was nontoxic to fish.