Could you be in compliance with AAMI regs (chemical analysis) and still have bacteria travel across RO membranes? Not sure how it works. I know a 99% reject will allow some things through but I thought bacteria were too big to go through.
<Brett>
Posted
I don't think any bacteria goes through the membrane unless you have a major hole in it.
Bacteria and endotoxins can get through the membranes. If you have say a count of 100cfu going into the RO and 99% rejection then most likely you may have 1cfu on the RO output. That is also part of the reason that ultrafilters are used to catch any of the bacteria that may have got into your loop before it goes out to the stations.
Bacteria is too big to go through a perfect RO membrane...unfortunately, there is no such thing as a perfect RO membrane. If you feed your RO membrane 50 cfu/ml bacteria, that is 189,250 cfu/gallon. If you feed your RO 10 gpm, your membranes are exposed to 1,890,000 colonies of bacteria per minute. If the RO membrane removed 99.9%, the RO membrane is still passing 1892 colonies per minute.
The Water Guy - Florian Services
Posts: 490 | Location: Chicago | Registered: 24 January 2005
Ok, with Florian's last post in mind, how many of you culture your output of your pretreatment, as in the water going to your RO systems? Do you think is necessary? If so how often? What level would be acceptable? Unacceptable? What do you do to correct it if you do have an unacceptable level?
The only time we really "CULTURE" our pre-ro system, is if we are having a bacteria problem and need to find out where it is coming from. We do however, culture post-carbon (pre-ro) to see just how foul'd the secondary carbon is. Keep in mind that it is not mandatory that you do this, but if you do, the acceptable ranges would be just like anything else 200 cfu/50 cfu 2 eu/1 eu. You also ask what do you do to correct it.. The only thing you can do to correct it, pre-ro, is to redraw, notify medical director, and if at all necessary = rebed.
John H.
NOTE: This is my professional OPINION. You should be cautious about taking advice from a forum.
I don't know how it works, but I'm pretty sure if you culture your tank (carbon or softener) that does not see chlorine, you will probably not know what's really in it bacteria wise until (or if) you were to disinfect and dislodge all the bio-film. Until they figure out a way to disinfect the tank, best to try and get the flow rate as high as possible. JMHO
