chem geek Posted February 8, 2008 Report Share Posted February 8, 2008 This thread is in response to this post that asks about chlorine-resistant Cryptosporidium. Crypto, as its sometimes called, is a protozoan cyst (technically an oocyst) which means it is in a very tough outer layer that is resistant to chlorine and is like being in hibernation. Giardia is another example and is also tough to kill though is not quite as resistant to chlorine, though it's still pretty darn resistant. Both of these get into water from the intestinal tracts (so fecal matter) of infected persons and such persons generally have diarrhea which is the primary symptom when getting this pathogen. The cysts do NOT reproduce in water -- they only reproduce when inside the intestinal tract of an infected individual. You basically have to punt in this situation as you're not going to absolutely prevent it in terms of quick transmission. In practice, it's more of a concern in commercial and public pools since there are so many people that are exposed from one person who ignores the "don't swim if you're sick" rule. Maintaining proper chlorine levels does help, but not by very much. Some quoted CT times for Crypto and Giardia from the CDC are shown here and note that this is for chlorine with NO CYA in the water. The Giardia CT is 45 while the Crypto CT is 9600. The normal chlorine level in pools and spas that use CYA is roughly equivalent to 0.1 to 0.2 ppm FC if there was no CYA in the water. This means it would take from 4 to 8 hours to kill Giardia, but over a month to kill Crypto. Even if one did not use CYA at all, it would take around 7 ppm FC for 24 hours to kill Crypto ("killing" meaning to the level to become non-infectious). In practice, there aren't that many outbreaks of Crypto so something about the combination of facts of CT value, how few oocysts it takes to become infected, and the low incidence rate doesn't make sense. I suspect there is more Crypto out there in pool water than people realize, but some other factors keep it from being a more frequent problem. If there is an outbreak or a suspicion of Crypto, then probably the easiest way to kill it is by using a disinfectant such as chlorine dioxide. Ozone and UV are other alternatives. Then again, take a look at the list of outbreaks in this report and see some ozone/chlorine systems (but these are large pools so it takes a while to turnover the water through an ozonator). So this would be one reason to have an ozonator in a spa, but realistically the chances of getting Crypto in a small spa are almost nil unless you frequently throw large parties with irresponsible guests (though it only takes just one such guest). As for the commercial/public pool and spa industry, I think they are leaning towards UV systems since those seem to be the most reliable at killing a variety of pathogens including Crypto with minimal side effects and at reasonable cost (at large scale). Richard Quote Link to comment Share on other sites More sharing options...
Hillbilly Hot Tub Posted February 9, 2008 Report Share Posted February 9, 2008 This thread is in response to this post that asks about chlorine-resistant Cryptosporidium. Crypto, as its sometimes called, is a protozoan cyst (technically an oocyst) which means it is in a very tough outer layer that is resistant to chlorine and is like being in hibernation. Giardia is another example and is also tough to kill though is not quite as resistant to chlorine, though it's still pretty darn resistant. Both of these get into water from the intestinal tracts (so fecal matter) of infected persons and such persons generally have diarrhea which is the primary symptom when getting this pathogen. The cysts do NOT reproduce in water -- they only reproduce when inside the intestinal tract of an infected individual. You basically have to punt in this situation as you're not going to absolutely prevent it in terms of quick transmission. In practice, it's more of a concern in commercial and public pools since there are so many people that are exposed from one person who ignores the "don't swim if you're sick" rule. Maintaining proper chlorine levels does help, but not by very much. Some quoted CT times for Crypto and Giardia from the CDC are shown here and note that this is for chlorine with NO CYA in the water. The Giardia CT is 45 while the Crypto CT is 9600. The normal chlorine level in pools and spas that use CYA is roughly equivalent to 0.1 to 0.2 ppm FC if there was no CYA in the water. This means it would take from 4 to 8 hours to kill Giardia, but over a month to kill Crypto. Even if one did not use CYA at all, it would take around 7 ppm FC for 24 hours to kill Crypto ("killing" meaning to the level to become non-infectious). In practice, there aren't that many outbreaks of Crypto so something about the combination of facts of CT value, how few oocysts it takes to become infected, and the low incidence rate doesn't make sense. I suspect there is more Crypto out there in pool water than people realize, but some other factors keep it from being a more frequent problem. If there is an outbreak or a suspicion of Crypto, then probably the easiest way to kill it is by using a disinfectant such as chlorine dioxide. Ozone and UV are other alternatives. Then again, take a look at the list of outbreaks in this report and see some ozone/chlorine systems (but these are large pools so it takes a while to turnover the water through an ozonator). So this would be one reason to have an ozonator in a spa, but realistically the chances of getting Crypto in a small spa are almost nil unless you frequently throw large parties with irresponsible guests (though it only takes just one such guest). As for the commercial/public pool and spa industry, I think they are leaning towards UV systems since those seem to be the most reliable at killing a variety of pathogens including Crypto with minimal side effects and at reasonable cost (at large scale). Richard Thanks, I had asked about this because Sea Klear has a product they are pushuing, the PRS system that they state will remove crypto and that it is the only EPA approved product that traps algea, crypto, e coli and giardia in the filter. Was wondering thoughts on this, more information etc. I have been reading about some outbreaks out west that have been an issue. Worry that over time germs will become more and more resistant to sanitizers, such as we have to antibiotics. Scary thoughts! Quote Link to comment Share on other sites More sharing options...
chem geek Posted February 10, 2008 Author Report Share Posted February 10, 2008 The link is here to SeaKlear PRS and it's really interesting. One of the biggest problems with Crypto is that it's cysts are so small that they don't get trapped in the filter. With Giardia, a good filter can often trap it. So having a product that enhances filtration and specifically consolidates or attaches to Crypto is a good thing. I just hope it's not "just another clarifier" that they are touting saying it traps Crypto when it might not be much better than a high quality clarifier. It would be good to have a scientific reference of the product actually doing what they claim. Quote Link to comment Share on other sites More sharing options...
wireman Posted February 12, 2008 Report Share Posted February 12, 2008 I'm not overly concerned bout crypto in my hot tub lol! Now if I was filling it from a slow running stream in the woods.. Quote Link to comment Share on other sites More sharing options...
waterbear Posted February 12, 2008 Report Share Posted February 12, 2008 I'm not overly concerned bout crypto in my hot tub lol! Now if I was filling it from a slow running stream in the woods.. Actually, if a bird pooped in your spa while it was open that could introduct cyrpto into the water. (and this does happen!) Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.