Ultra filtration is a separation process in which water and smaller size particles could pass through the membrane and large size substance such as particles, rubber and relatively high molecular will be absorbed. The micro holes on the surface could retain 3x10000-1xT0000Da substances. Water will pass the the membrane with large size molecular substance is retained. Large size material will be retained, small size such as water will pass through.    

Compared with the traditional pretreatment process, ultrafiltration has the advantages of simple system, convenient operation, small occupation, low investment and excellent water quality, which can meet the inlet requirements of all kinds of reverse osmosis devices.
The concentration polarization of ultrafiltration can be completely controlled by reasonable selection of operation conditions and cleaning process, which makes the pretreatment method more reliable.
Ultrafiltration has good removal properties for all kinds of colloid in water, so it can be considered to be extended to the pretreatment of condensate concentrate and ion exchange desalination system.
Membrane module：
Membrane number: according to water to process
Membrane model： CPO-1060
Membrane filter method： Full flow filtration
Material： PVDF
Producer： Cawnpore
Membrane wire diameter：0.7um－1.3um
Effective membrane area of a single membrane assembly：55.7m2
Common membrane flux range： 40～60L/m2·h
Membrane flux designed in this project：≤50L/m2·h
Quality Guarantee Period：3 years
Running press：0.1～0.2MPa
Running Press differential：0.01～0.1MPa
Temperature： 10～40℃
Work method External pressure type, with compressed air, inlet must be installed pressure reducing valve
Filtration cycle：15～60min
Total backwash duration：30～60s
Backwash strength of water：100～150L/M2·S
Hollow fiber ultrafiltration membrane is a very thin polymer material made of polysulfone (PS), polyether sulfone (PES), PVDF or polyacrylonitrile (PAN) with asymmetric microporous structure.
Asymmetric ultrafiltration membranes have an extremely smooth and thin (0.1 micron) inner surface with apertures between 0.002 and 0.1 micron. This inner surface is supported by an asymmetrical structure with apertures up to 15 microns.The combination of a small aperture synovial surface with a larger aperture supporting material allows for minimal flow resistance to filter the tiny particles and is less likely to block them.
Ultrafiltration is a process of cross-flow and tangential flow in which the fluid to be filtered (the feed fluid) flows along the membrane surface. This creates fluid shear conditions on the inner wall of the hollow fiber, making it difficult for contaminants to form on the membrane surface.The suspended matter in the feed solution will be concentrated and discharged as discharge solution. This tangential flow process technology makes it difficult for particles to accumulate on the surface of the membrane, resulting in long productivity during the cleaning cycle
The main characteristic of reverse osmosis system is that it has strict requirements on inlet water quality, which is mainly reflected in the sludge density index SDI value of reverse osmosis membrane fouling and blocking index. It has been proved by practice that the condition of SDI≤2 can be maintained stably for a long time only under the premise of membrane filtration technology. Therefore, ultrafiltration technology as RO pretreatment has been more and more widely used at home and abroad.

2.Long Term Running Condition
As a pretreatment equipment with the highest filtration accuracy, ultrafiltration has a very high blocking effect on organic pollutants, colloidal pollutants and suspended pollutants.
Pretreatment filtration with inlet water less than 100um.
The inlet water pressure is within the rated operating pressure; Backwash pressure is within the rated pressure.
Automatically and frequently self-cleaning.

3. Requirements for ultrafiltration elements
Larger interception molecular weight, larger water production, and lower operating pressure; Smaller interception molecular weight, smaller water production, and higher operating pressure.
The choice of operating pressure, low operating pressure will reduce the energy consumption of the system, but also can improve the stable operation of the system; 
The selection of backwash pressure will help to improve the safety performance of ultrafiltration.
Membrane materials have strong anti-pollution properties such as PVDF, polyether sulfone, etc.
When the internal pressure type is used, the washing is more thorough.
The more conservative membrane flux will contribute to the long-term stable operation of the system.