Tuesday, March 5, 2013

What is the difference between Ultra-Filtration UF and Ultraviolet UV?

Question I have is:  What is the difference between UF and UV systems?   I was told by a neighbor that both remove bacteria, but UF does not require electricity.  Which is better for my situation?  I have a shallow well and I am worried than when it rains, I may be getting bacteria into the well from our barnyard area.  Thanks in advance,

Salem, OR

Russ -  this is a good question, both can remove bacteria (disinfect your water) under the right conditions.  Ultra-Filtration or UF, is a very fine membrane that filters water down to 0.02 microns or less, effectively straining out all bacteria.   Ultraviolet sterilizers (“UV”) are light sterilizers and kill bacteria by inactivating the DNA in the bacteria cells.  The bacteria are not removed, but they are so damaged by UV light, that they cannot reproduce and therefore are considered harmless.

Under some conditions the bacteria may not be all 100% inactivated and they can redevelop later in your pipes.  The water must be very clean and generally low in minerals for UV to be effective.  

Homeowners occasionally inquire about the difference involving UF and UV sterilizers for killing of bacteria in wells and springs. The primary distinction is that UV kills bacteria but doesn't remove them, while UF is able to physically block them. While Ultraviolet relies upon electrical power to work, UF does not require electrical power. In the event of a storm event, boil-order, or other unexpected emergency a UF can continue to remove bacteria, whereas an Ultra violet system won't.

A very effective approach if you know your water is contaminated with harmful bacteria is a two stage approach:  UF followed by UV as a back-up.  The UF removes turbidity, making the water very clear and prepares it for the UV.  The UV then sterilizes the water of any viruses that may be present.

For water high in minerals, sediment and bacteria, a backwashing sediment filter is used, followed by a water softener, then UF, and then UV sterilizer.  See this diagram of a typical installation:

UF filters look like strands or fibers and have hollow cores. The surface of the membrane serves as a physical barrier to turbidity and pathogens. The use of thousands of these fibers incorporated within every system provides adequate surface area to provide on-demand flow rates of 10 gallons each minute per standard size 4 x 40 " membrane. Each UF membrane contains millions of 0.015 micron sized pores. As an example, the Cryptosporidium as well as Giardia cysts, two common types of parasitic organisms are approximately 8 to 13 microns long and are oval in form. Some new UF systems on the market have been independently tested by certification organizations to block 99.999 percent of bacteria and 99.999 percent of viruses.99.999 percent of bacteria and 99.999 percent of viruses.

UFL-440 UF: 10 GPMVizion UFL-440 Ultrafiltration System: 10 GPM

UFL-440 UF: 10 GPMThe UFL-440 system uses a permanent pressure vessel and a replaceable ultra filtration cartridge that is automatically flushed by a pulse controller.  Dimensions: 11.5 x 6 x 47 inches. Operating weight 42 lbs. 10 gallon per minute capacity. 100-240 V. 1 NPT inlet and outlet connections; 3/4 NPT drain connection. Max operating pressure 100 psig. Max operating temperature 104 F. Nominal pore size .015 microns. pH range 3-10.




We recommend you have your water tested to see if this system is appropriate for your application.  Please send us a water analysis or check out one of our low cost well water testing options.