What Is Ultrafiltration Membrane And How Does It Work?

by Dr. Jonathan Doyle - Updated March 02, 2021
Ultrafiltration(UF) is a physical filtration process that uses home water pressure to push water through the semipermeable membrane to get rid of particles larger than membrane pore size in water.
The ultrafiltration membrane utilized during the filtration process is a kind of hollow fibers with pore size ranging between 0.01 to 0.1 micron, which is several thousand times smaller than a human hair.
While water feeds in, the particles larger than the pore size would be retained on the surface of the membrane, whereas water and beneficial minerals that are smaller than the pore size would pass through and become the drinkable water.
One highlight of the ultrafiltration membrane is that it does not remove all the dissolved minerals. This could be considered a pro if the home water TDS is at a good level since a certain amount of the retained minerals are beneficial to our health. Yet, it would be a shortcoming if the source water has a high TDS level, as overmuch TDS would significantly affect the water taste.
So, you’d better check your home water TDS level before you buy a UF system.
According to an authority review conducted by the United States, Canadian, World Health Organization (WHO) and European Community (EC), the US recommended maximum TDS level is 500 mg/L.
If your home water TDS level has already exceeded this value, we suggest you choose a reverse osmosis system that could significantly reduce TDS.

What contaminants does the UF membrane remove?

The UF membrane is very effective in reducing rust, sediment, chlorine taste and odor, benzene, crypto, bacteria; it could also partially reduce algae, chloride, copper, lead, mercury; whereas it has no effect on chemicals and TDS.

Frequently asked questions about the UF membrane

Does Ultrafiltration Need Electricity?

Unlike the reverse osmosis filtration that needs a pump to push water past the membrane by increasing water pressure, ultrafiltration could work well with standard home water pressure. Therefore, most of the ultrafiltration system does not require electricity.

What’s the difference between ultrafiltration and reverse osmosis?

Ultrafiltration and reverse osmosis are all physical filtrations that use pressure to push water through the semipermeable membrane, and block impurities larger than the membrane pore size at the outer surface of the membrane.
The main difference between them is filtration accuracy. The ultrafiltration membrane pore size ranges from 0.01 to 0.1 microns, whereas the reverse osmosis membrane has a more fine pore size of 0.0001 microns. Thus the RO membrane could remove impurities that are much finer, such as TDS.
Given the difference in pore size, RO systems usually need a pump to increase pressure, while ultrafiltration systems can work well with standard home water pressure. That explains why most RO systems need electricity supply but UF systems don’t need it.

What’s the difference between UF filtration and UV filtration?

UF removes impurities larger than the pore size by filtering them out. UV only works for microorganisms like viruses and bacteria in water by killing them with UV light.

Different types of ultrafiltration systems

There are many kinds of UF filters on the market to meet different customers’ needs, like the whole house filter, which installed at the point of entry where water comes into your home from a municipal supply. As well as point of use filter, like under-sink UF water filter and portable water filter straw.

Whole House Ultrafiltration Systems

The whole house ultrafiltration system is a point-of-entry water filtration system that serves the entire home, including the water tube, faucet, shower head, etc.
With the 0.01-micron UF filter, it could eliminate different kinds of impurities and contaminants for the whole home and greatly increase the service life of the tubes, faucets, and any other filters present down-line.
But the drawbacks of the whole house systems are that they usually need to be installed when you build the house. Furthermore, they are not comparatively affordable, most of which cost several thousands of dollars. However, point-of-use ultrafiltration systems only take a few hundred dollars or even less.

Under-sink Ultrafiltration System

Under-sink UF membrane filters are very popular for homes and families for the budget-friendly price and excellent filtration performance. Let's take Waterdrop smart under-sink UF system and inline under-sink UF water filter for example.

Smart Under-Sink UF System

The smart under-sink filter smart under-sink ultrafiltration system has a very similar appearance to the RO system. It also takes multi-stage filters and has a smart filter life indicating system on the front panel.
It uses polypropylene, activated carbon as pre-filters to remove most of the large eye catchable impurities including colloids, sediments, rust, absorb chlorine taste and odor, fluoride as well as most VOCs in water.
After that, the water would be filtered by the UF membrane filters with a pore size of 0.01 micron, where the bacteria, superfine rust and sediments, lead and other heavy metals would be removed. The filtered water then followed by another activated carbon filter to improve the taste and eventually flow to a dedicated faucet for home drinking, cooking, etc.
The main difference between the smart UF under-sink system and the modern RO system is the filtration efficiency——the UF filter cannot remove the superfine dissolved minerals in water as discussed above.

Under-Sink Inline Ultrafiltration Water Filter

The inline ultrafiltration water filter is a more compact filtration system compared with the smart UF water filter.
It takes an all-in-one design that puts different filter materials like a polyester membrane, activated carbon block, KDF, UF membrane all together in one composite filter to get rid of the harmful substances.
Benefit from the all-in-one design, the inline filter takes very little space under the counter and especially fits for small apartments, RVs, etc. Just connect it between the tap water input and output faucet, you will be accessible to refreshing, clean water from the tap at the minute.

Portable Water Filter Straw

Ultrafiltration membranes can also be used in portable water filters for drinking water directly from rivers, lakes, and other water resources outdoors.
Also takes an all-in-one design, the portable water filter straw is a four-stage filtration made out of pre-filter fabric, UF membrane, activated carbon filter and post polyester membrane.
Though the filter itself has a smart frame, the filtration efficiency is powerful. Most of the harmful substances such as chlorine, rust, colloids, sediments, bacteria and heavy metals could be effectively reduced from the raw water.
The compact design allows you to put it in your backpack and takes it everywhere, making it possible for you to access safe water anywhere, anytime.


It is important to understand the working principle of the filtration system before choosing a product. Only in this way, you could understand what kind of filtration works best for your water and whether the system could meet your needs or not. I hope this article would be useful in helping you make the right choice.




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