What is Membrane Flux?
Simply defined, membrane flux refers to the amount of liquid that can be treated over a defined time.

In other words, flux represents the processing capacity of a filtration membrane. It can be used for any type of membrane (microfiltration, ultrafiltration, nanofiltration and reverse osmosis). In general, to know the flux of a membrane, you must rely on the manufacturer's specifications.

What is the purpose of a membrane flux?

There are many reasons why it is important to know the flux of a membrane. Generally speaking, it can be used to help you decide which type of membrane to choose for your situation. In other words, if you know the flow rate you need, you will know that a type of membrane may or may not provide your needs.

Knowing the flow rate of your membranes can also help you identify abnormal fluctuations in your water production. If your systems have membranes that can produce 30 gpm, a decrease in flow could mean a problem within the system or a change in the water.

What can affect membrane flow?

There are several parameters that can affect the flow of a membrane. One can think of contaminants found in the water. For example, the presence of silica tends to cause membrane fouling. This example is valid if it is water that is being treated, but if it is a denser liquid that is being treated, the flow can also be affected. 
Secondly, the treatment system itself can have an impact on membrane flux. For instance, the operating pressure will greatly affect the output.

In addition to these criteria, there are other characteristics specific to the membranes that affect their flux. These include the materials used, the filtration surface, the spacing between the membrane layers, the pore size, etc.

How to calculate the flux of a membrane 

Although the production rate of a water treatment system is often expressed in gallons per minute, membrane flow is generally expressed in gpd/ft2 (gallons per day per square foot)
 Let's assume your water treatment system produces 50gpm (gallons per minute). 

  • (50 gallons x 60 minutes) x 24 hours = 72,000 gallons per day

Your system has 10 membranes each with 400 square feet of treatment area. 

  • 10 x 400 = 4000 sq. ft. 
  • 72,000 / 4000 = 18gpd/ft2

By following these steps, you will be able to know the flux of your membranes. As mentioned above, for new membranes, we recommend that you refer to the manufacturer's specifications.

in FAQ
What is a Dielectric Material?
Dielectric materials are various materials that resist electrical currents.