Ultrafiltration

What is ultrafiltration?

Ultrafiltration is a pressure-driven membrane technology to remove (colloidal) particles, sediment, turbidity, bacteria and viruses. Depending on the molecular weight, UF will also remove a wide range of the humin and humic acid range and suspended iron particles. Ultrafiltration is commonly used in the treatment of surface water, rain water, well water, borehole water, seawater and municipal drinking water.

Ultrafiltration is originally created using membranes from kidney dialysis and involves a similar process that takes place in the kidneys on a daily basis. Kidneys are filtering the blood from the urine and let the fluid with harmful particles through so that they can leave the body of a person. Similar techniques are used during the ultrafiltration method for surface water.

There are various industries in which ultrafiltration is used as a separation method. Examples are:

• Food and beverage industry
• Off shore industry
• Healthcare
• Agricultural
• Pre-treatment for nanofiltration or reverse osmosis (e.g. for seawater desalination)

The ultrafiltration process

The process of ultrafiltration as a separation method is worldwide used in water purification systems. During the ultrafiltration process, water will be pushed through the 0.02 μm pores of the  membrane wall from the inside to the outside whilst removing suspended solids, particles, viruses and bacteria out of the water. This ultrafiltration process is also called Reversed Osmose. The remaining particles on the inside of the membrane can be easily removed from the inner membrane via an automatic forward and backward flushing device. The efficiency for reduction of bacteria with the ultrafiltration process is 99.9999% (Log 6) and for viruses the membranes have been tested LOG 4 on MS2-phage.

Since the ultrafiltration membrane is a physical barrier, there will be filtration with any given pressure. PB advises to use a pressure between 2 and 6 bars. A higher pressure might cause leaking membranes. To be assured of an integer system, PB has developed an APT unit which can be applied on UFKS and AquaproteQ systems. The APT will test the integrity of the membranes every 24 hours and will automatically by-pass a leaking module.

Benefits of Ultrafiltration

• With ultrafiltration, all dirt particles, bacteria and viruses are filtered, which reduces the growth of biofilm. The eventual product of ultrafiltration is clean and safe (drinking) water.
• The filtering effect is always active, regardless the power supply. Therefore it is a very effective and sustainable way of water filtration.
• A water purification system with ultrafiltration is maintenance-friendly. Every 24 hours the gatekeeper systems test themselves for membrane ruptures. If a breakage occurs, an alarm will be issued and our employees will visit you as soon as possible.

Important aspects

An important aspect of ultrafiltration is that fouling the membrane means that less water can be purified. This also means that the membranes have to be replaced more quickly. To prevent membranes from clogging quickly, the membrane installation must be pre-treated. The pre-treatment of the membrane installation is also essential for reverse osmosis, micro- and nanofiltration. However, there is no standard pre-treatment recipe. Because every type of water is different, an optimal pre-treatment for every water type is determined by the consultants of PB.

A revolutionary system: 7 Bore Membrane

As a result of the open foam structure of the membrane, the ultrafiltration system can be operated with a very low pressure and high fluxes. In addition to a high chemical and biological resistance, the revolutionary 7 Bore membrane has a very high mechanical stability. The 7 Bore membrane, with 7 capillaries in each fiber, is much stronger and can sustain high-pressure water surges more easily than conventional single bore membranes. With our unique 7 Bore membrane PB has set a new standard in ultrafiltration technology.

Decrease of water quality during transportation

Many drinking water companies around the world are using Reversed Osmose technology during their ultrafiltration process. Because of the fact that Reversed Osmose will also remove the minerals and salt from water, they will perform a remineralisation step afterwards. As soon as the water leaves the drinking water plant, the quality is very high and healthy.

Unfortunately many pipelines will decrease the water quality during transportation, making Point Of Entry filtration a must in many countries around the world. Especially in old cities with old pipelines and a lot of construction sides.

Ultrafiltration features

PB uses a membrane with a nominal pore size of 0.02 microns for ultrafiltration. Thus, can be used as a separation method when particles with a pore size of larger than 0.015 microns have to be removed from (drinking) water.

• Max NTU 30
• MWCO 100-150 kDa*
• Max COD 12mg/l
• Max TSS 50mg/l**

* 75 kDa membranes available
**alternative membranes 300mg/l available