ULTRAFILTRATION
IntroductionUltrafiltration is a membrane filtration technology. The membrane can be used to seperate small
colloids and large molecules from water and other liquids.
The ultrafiltration process falls between reverse osmosis and microfiltration in terms of the size of
particles removed, with ultrafiltration removing particles in the 0.002 to 0.1 micron range, and
typically removing organics over 1,000 molecular weight while passing ions and smaller organics.
How does it work?
Untreated water is forced against a semipermeable membrane. The membrane allows the water
molecules to pass through and screens out the colloids much like a sieve. Excess water is used
to wash the colloids off the surface and to a drain. Unlike most filtration, the sieve does not fill up
with trapped material because the colloids are to large to fit into the opening of the sieve. A good
analogy would be dumping a mixture of water and marbles(the colloids) over a window
screen(the membrane). Most of the water would pass through the screen. The remaining water
would help wash the marbles off the screen and would be sent to waste with the marbles. The
screen would not become plugged because the marbles are too large to fit into the openings.
What can this be used for?
We use this process as an alternative to floculation and filtration. This technique is not always an
appropriate alternative to floculation and filtration. We can do on site testing and lab testing to
determine how successful either of these techniques will be for a particular application.
What does a system consist of?
Because the UF filters are expensive, they are not usually sized large enough to handle peak
flows. This requires the system to have several components to allow the UF to produce water
during times of no use and store it for later peak demands.
The three basic components of the system are the UF filter (UF filter, housing, controls, pre-filter
and solenoid), storage tank with control float and repressurization pump(see picture). The
repressurization pump delivers water from the storage tank to the house. The repressurization
pump will cycle on and off to deliver the water to the water fixtures. When the water level in the
storage tank drops below the float, the solenoid valve will open and send water through the UF
filter to the storage tank.
Click here to see layout detail.
What will it cost?
The cost will depend on the flow(gpm) you require. The greater the flow the more the filters will
cost. You can expect systems to start at a minimum of $4000. If you require higher flows or have
other materials in the water that need to be removed, you can expect this price to be higher.
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