The R&D Center for Eco-material and Eco-chemistry at the Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, has designed an uninterrupted anti-disturbance separation device working on the principle of reverse flocculation and ultrafiltration. The device is specially designed for the extraction of protein from potato juice waste water and utilization of potato starch processing waste water.

The removal rate of chemical oxygen demand (COD) of the device is as high as 80% and the removal rate of turbidity is above 85%. The water discharged from the device meets the third grade of national wastewater discharge standard (GB8978-1996) and irrigation water quality standard (GB5084-92) and can be used to irrigate and wash the raw materials for potato starch processing.

Using the device, clean water can be discharged uninterruptedly while the flocs deposit, thus realizing uninterrupted dehydration. Moreover, crude protein containing 70% water can be recovered.

The independent intellectual property right of the device and 3 Chinese invention patents concerning related technologies have been obtained.

The researchers at the Center have also successfully prepared 2 highly efficient and low-cost clay-based flocculants specially used for the treatment of potato starch processing waste water. The flocculants have the functions of flocculation, adsorption and filtration through polymer cross-linking.

As for the dehydration of protein, the researchers have designed a solar energy based room temperature heat pump drying device with double heat-collecting and double heat preservation functions. With it, crude protein containing 70% water can be changed into crude protein powder containing 80% protein.

The development of the device and related technologies is of great economical, social and biological significance. For a potato starch processing enterprise with the production scale of 10 000 tons, if 80 000 tons of potato juice is processed every year and 13kg crude protein can be recovered from each ton of waste water, with this technology, 936 0000 RMB output value can be increased and 70 000 tons of water can be saved. And 80 000 tons of waste water can be prevented from polluting the environment.

Background information:

The period from September to October is the peak time for harvesting and processing potato in the north part of China. A large amount of waste water will be produced while processing the potato starch. The concentration of potato juice is high, the discharge amount is great in quantity and the COD value is 30000-50000mg/L. Moreover, the potato juice contains around 2% protein. If not treated timely, the waste water can lead to erosion. Direct discharge can lead to the eutrophication of the water body.

Due to the short processing period, great quantity in discharge amount and low temperature of the environment, traditional treatment techniques can not be satisfactory. Moreover, with traditional separation techniques, the extraction rate of protein is low.