Study On New Treatment Techniques Of Potato Starch Waste Water

Potato is an essential crop in the world and it has a high nutritional value. Except as food it also plays a significant role as ingredients in industrial potato starch production. Recently, potato industry grows rapidly in China where potato starch production reaches 40 tons annually, from which about 300 tons of potatoes is needed and about 800 tons of waste water is released. Technical waste water from potato starch processing is the main waste water resource, which contains protein (0.9-2.1%), carbohydrates and several organics, its COD (Chemical Oxygen Demand) about 10000-40000 mg/L. Protein in the waste water will undergo natural fermentation, release some bad odor gases (e.g. Hydrogen sulphate, Ammonia, Indole, etc). At the same time it also promotes microbial growth that cause depletion of DO (Dissolved Oxygen) in the water, hence the water become muddier and it becomes a serious environment pollutant. Physical, chemical and biological methods are used to treat the waste water, both domestic and international. Waste water from the potato starch production was treated by combination of physical-chemical and biological methods. After a series of physical-chemical treatment which included protein precipitation, heating, centrifugation, decolorization, filtration and hydrolysis, the waste water was further treated by using biological enzyme Glucose Oxidase. Both of free and immobilized Glucose Oxidase were used in this biological enzyme treatment. Absorption followed by crosslinking with glutaraldehyde was chosen as the immobilization method and bamboo fibre was selected as the immobilization supporter. In this biological treatment immobilization condition and several factors which effect Glucose Oxidase activity such as pH, temperature, enzyme amount and reaction time were investigated.The result demonstrated that under pH 4.0 protein precipitation,90℃heating for 1h, decolorization using 1% activated charcoal in the physical treatment, about 30% sugar and COD of the waste water was removed and its appearance was very transparent as clear water. After this treatment, the waste water was further treated by enzyme Glucose Oxidase, free as well as immobilized one, under pH 6.0-7.0 and temperature 30℃for 1-2d. Eventually, after both methods were carried out, its sugar was declined about 95%, and the COD was removed approximately 85% from the initial waste water.