Ultra filtration is membrane separation process whose separation principle is the screening, the pressure is the impetus. The filtration precision is between 0.005 and 0.01, which can effectively remove particles, colloids, bacteria, heat source and polymer matters in the water. It can be widely used in the separation, concentration and purification of materials. Ultra filtration process has no phase transformation, operated under normal temperature, which is very suitable for separation of thermosensitive substances, it also has the good temperature resistance, acid-base resistance and oxidation resistance, it can be used continuously under the temperature of below 60℃ and the PH of 2-11.
II. Classifications of ultra filtration membrane
According to the structure, we can classify ultra filtration membrane into plate and frame (plate-type), hollow fiber, ultra filtration membrane, pipeline, rolling type and so on. Thereinto hollow fiber ultra filtration membrane is the most advanced ultra filtration technology among them. The external diameter is 0.4-2.0mm, the internal diameter is 0.3-1.4mm, the hollow fiber pipe wall is full of micropores, the apertures depend on the molecular intercepted, the molecular weight intercepted can reach to more than hundreds and thousands. The raw water moves the outside and inner cavity of hollow fiber, it can be divided into external pressure and internal pressure hollow ultra filtration membrane. Ultra filtration is the dynamic filtration process, the matters intercepted will be discharged with the concentrated solution, so that it will not block surface of membrane, and run in the long-term.
III． Application of ultra filtration technology
The early industrial ultra filtration was applied to the sewage and waste water treatment. During the 30 years, with the development of ultra filtration technology, now it has been widely used in food, beverage, dairy, biological fermentation, biomedicine, pharmaceutical chemicals, biological preparations, Chinese traditional medicine preparations, clinical medicine, printing and dyeing wastewater, sewage treatment of food, resource recovery, environment engineering and so on.
IV．Advantages of ultra filtration equipment
A. The components of ultra filtration membrane use the world famous membrane, in order to ensure that the organic membrane components are the best, and the interception performance and membrane flux.
B. The system has a high recovery, and products are the best, which can realize the high-efficiency separation, purification and concentration of materials.
C. The treatment process has no phase-change, there is no harm to material components, and the process of separation, purification and concentration are done under the normal temperature, it is particularly applicable to the treatment of thermosensitive substances, it also can avoid high temperature damaging the bio-active substances, and keep the bio-active substances and nutrient content in the raw material system.
D. The system has low energy consumption and short production cycle. Compared with conventional technology equipments, this equipment has the low run cost, the production cost is reduced greatly, and the economic benefits have been enhanced.
E. The system has the advanced design, high integration, compact structure, small covering area, simple and convenient operation and maintenance as well as low labor intensity.
F. The system adopts sanitary pipe valves, the field is clean, which meets the specifications and requirements of GMP or FDA.
G. According to the clients’ specific requirements, the control system can be customized, which combines the advanced control software. Monitor the operation parameter of the important technology online, to avoid the misoperation, keep the system running in the long-time.
V. The attentions of using hollow fiber ultra filtration membrane
A. The filtration system needs to be sterilized regularly. The ultra filtration membrane can intercept bacteria, but not kill them. We cannot promise that there is no bacterium after the long-time useage, one bacterium can cause the large number of bacteria, even though the ultra filtration membrane has the best interception performance, which can affect the water quality directly. For examples, the finished products of mineral water have the semi-transparent, filamentous and white flocculus streptomyces group, the phenomenon is leaded by the polluted system. Therefore, the filtration system and run environment must be sterilized regularly. The sterilization cycle depends on raw water quality. To the ordinary tap water in the city, the sterilization cycle is between 7~10 days in summer, in winter the cycle is 30~40 days, in spring and autumn the cycle is 20~30 days. When the surface water is the source of water supply, the sterilization cycle would be shortened. We can use the 500~1000mg/L sodium chlorate solution one time, or the 1% hydrogen peroxide solution circulating flow to sterilize, or else we can just soak it into water for half an hour.
B．Because each ultra filtration module will be added protection liquid before leaving the factory, protection liquid should be flushed thoroughly, thus we can wash it with low pressure (0.1MPa) water for 1 hour, then wash it with high pressure (0.2MPa) for 1 hour, regardless of low pressure or high pressure, all the water bleed valves of effluent must be opened. When we use the effluent, we should check and verify whether there is the fungicide in the water.
C. When we should handle ultra filtration module with care, and pay more attention to its protection. Because ultra filtration module is the precision equipment, we use and install it carefully, handle it with care, let alone the damage. If the module is out of service, it should be clean firstly, and then use 0.5% formaldehyde solution to sterilize and seal it tightly. In the winter, we should have an antifreeze treatment, or the modules would be scrapped.