Application And Study Of Compound Bacteria Of Mold-saccharomycetes In Disposing Cassava Starch Wastewater

As a main crop of Guangxi province, most of the cassava was processed into starch and other industrial products. Wastewater yielded during production, it contained a amount of organic matters and the acidity value is very high, which could easily cause serious water and air pollution if it directly discharged. At present, biochemical process was widespread used in disposing cassava starch wastewater at home and abroad and have achieved some results, however, the wastewater was not disposed thoroughly, and the organic was not used effectively and did not turn waste into wealth.In the process of disposing simulating cassava starch wastewater, immobilization mold, which could degrade organics from macromolecule to micromolecule, was used in the prior period. In later period, dark red saccharomycetes grew by using organic micromolecule in the wastewater and recycled the saccharomycetes, which reached the purpose of continuing to dispose cassava starch wastewater. In this experiment, on one hand, mold and saccharomycetes could be used to dispose organic wastewater, and CODcr was decreased enormously; on the other hand, recovery saccharomycetes containing amounts of single-cell protein which could be used as animals feed, and could achieve economic benefits. The experimental results showed that:(1) Simulating cassava starch wastewater was disposed by using aspergillus niger, aspergillus oryzae and rhizopus in the same conditions, selected aspergillus niger as the better mold; the optimum culture conditions were inoculation concentration 10mL/100mL fluid nutrient medium, pH 6.0, stirring speed 1 lOr/min and temperature was 30℃.(2) Aspergillus niger was used to dispose the cassava starch wastewater, the optimum culture conditions were the dosage of activated carbon powders 2.0g, pH 6.0, 100rpm and temperature was 30℃. In these technical conditions, cassava starch wastewater was disposed for 72hr, the degradation of CODCr was 88.9%, which had proved that practice cassava starch wastewater could be disposed by immobilization Aspergillus niger.(3) Candida tropicalis and dark red saccharomycetes were used to dispose the simulation cassava starch wastewater in the same conditions, Using dark red saccharomycetes as the preferred yeast to dispose wastewater, the optimum culture conditions was 100mL medium, inoculation concentration 15mL, pH 5.0, stirring speed 160.0rpm and temperature was 30℃, the thallus grew well and the wet weight of thallus could reach 37.8g/L(4) the optimum conditions of dark red saccharomycetes for disposing cassava starch wastewater were:the seed age was 24h, inoculation concentration was 15mL/150mL wastewater, origination pH value was 4.0, liquid volume in flask was 150.0mL/250.0mL, stirring speed was 160r/min and the temperature was 30℃.In these technical conditions, cassava starch wastewater was disposed for 48hr, the degradation of CODCr was 51.5%. The wet weight of thallus was 33.6mg/L. It showed that dark red saccharomycetes could be used to dispose cassava starch wastewater.(5) Using the combined technology of free dark red saccharomycetes and immobilization aspergillus niger to dispose wastewater, the addition time of dark red saccharomycetes was at the time of 16th hr of immobilization aspergillus niger disposing wastewater, the fermentation total time was 60hr. In these technological conditions, the degradation rate of CODCr of fresh cassava starch wastewater could reach 96.5%, the recycling dry weight of thallus was 4.2g/L, the total protein level was 1.2g/L. The experiment showed that dark red saccharomycetes and immobilization aspergillus niger could be used to dispose fresh cassava starch wastewater, not only degraded the CODCr of wastewater but also achieved the single cell protein through recycling saccharomycetes.