Study On The Treatment Of Potato Starch Wastewater And Method For Cod Removal In Utilization Technique Of Potato Starchy Residue

In China, annual starch production has increased to more than 10 million tons, which results in over 3.4 million tons of potato residue waste and 20 million tons of starch wastewater discharge. Potato residue waste is not easy to store and transport, it will go bad in short time, and cause serious environmental pollution when left untreated. Meanwhile, starch wastewater gives off an unpleasant odor and Chemical Oxygen Demand (COD) of the waste is more than 30000mg/L, this type of highly concentrated organic wastewater is very difficult to treat. Institute of Microbiology, Harbin Institute of Technology has invented"Utilization technique of potato starchy residue": an aerobic fermentation process to produce single-cell protein (SCP) from potato residue and juice waste. This research improves and optimizes the utilization technology further to improve efficiency and reduce cost in the actual production.On the one hand, we do the research in the treatment of organics in the potato starch wastewater, including flocculation method, heating method, and fermentation method. The result shows: 42% of the crude protein in the starch wastewater flocculating deposite, which treated with CaCl2. Treating with heating method of 70℃, the COD removal efficiency of the starch wastewater is above 80%. After 48h of aerobic mixed fermentation, the COD in the potato residue waste is about 1700mg/L with a removal efficiency of above 90%.On the other hand, we improve and optimize the fermentation process indexed by COD in the final fermentation effluent, and the optimization includes: fermentation time, inoculums, amount of inoculation, temperature, and aeration rate. The result shows: in the 165t air-lift bioreactor, after 6~7d of fermentation, COD removal efficiency in the final fermentation effluent is about 60%. Under the condition of 500mL shaking culture, after 6d of fermentation, the maximum COD removal is 66%, when a mixed inoculum is used as the seeding solution, which includes Bacillus pumilus, Candida utilis, Aspergillus niger, Trichoderma harzianum, T. viride, and T. koningii. Under the condition of 500mL shaking culture, after 6d of mixed fermentation, COD removal efficiency of the 1/2000 and 1/1000 amount of inoculation system are 70% and 76%, respectively. Under the condition of 500mL shaking culture, 28℃is the optimum temperature for mixed fermentation, and after 6d, COD removal efficiency is about 71%. In the 1500mL homemade air-lift bioreactor, the best aeration rate is 0.1vvm, and after 6d of mixed fermentation, COD removal efficiency is about 55%.