Jul 4, 2005 at 3:32 pm #1216329
I used this system last year–worked great(didn’t get sick at any rate)–the one problem is that for the bigger beast like Cryptosporidium or giardia–it takes 4 hrs. to kill–which makes it less desirable while on the trail-I have heard that a coffee filter can filter out the bigger beasts–which would make the system make sense again if that were the case. Any thoughts?Jul 4, 2005 at 5:58 pm #1338697
for what it’s worth, based upon what i’ve read about the pore size of typical coffee filters, in theory it should work. i’ve read that some coffee filters have pore sizes in the 4 micron range. Whose & what type wasn’t specified. This really surprised me when i read that. i, naively, would have guessed that the pores would have been much, much larger.
[note: i can’t find the website now – it was a municipality website giving instructions for filtering water in case of a catastrophe. the reasons for filtering were for protozoans & suspended particles. site recommended chemical disinfection also – for viruses & bacteria. to me this sounds like a fairly reliable source, but i’m still skeptical w/o reading more from other sources.]
however, 2 micron filters are often recommended for filtering protozoans. both giardia & crypto are larger than 4 microns however. why the discrepancy in sizes? don’t know. safety margin perhaps? manufacturing issues related to uniform pore size in filters???
however, i don’t know that coffee filters are manufactured such that it is guaranteed that all pores in the filter are small enough to filter out the protozoans you mentioned. their intended purpose is to filter coffee, not protozoans. perhaps ALL pores in a filter are small enough (no larger than 4 microns), but this is probably only a manufacturing side effect & NOT the intended design.
i haven’t found any info on the web that provides sufficient info on coffee filter manufacturing & testing for these purposes.
for myself, i tend to be cautious, & often overly cautious, i’m not going to risk it using just a coffee filter without some better info than what i’ve been able to locate thus far.
i would use coffee filters for a pre-filter or a sediment filter, but would only rely on it to filter protozoans (at this ponit w/o further reliable info) in an emergency if no better method were available. but…hey…that’s just me – the old ‘worrywart’Jul 4, 2005 at 7:40 pm #1338698
Thanks for your insites Paul–Did a little more research–Cryptosporidium can actually fold itself down into the 1 micron range and avg size is 3-4 microns, Giardias a bit bigger–
and like you–I’d rather take no chances–
I did read where the Miox has a 95% rate with Cryptosporidium after 30 min.
99.9 after 4 hours
Obvious plus with Miox is the size 3.5 oz. size plus can treat up to whatever capacity you want–quickly with little effort.
It will take care of 99.9% of Giardia after 30 min.
Guess I am thinking that up high out of a stream–30 minutes should be plenty.
And if you are traveling with others–you can treat a couple of gallons of water each evening and have enough for the following day.Jul 4, 2005 at 11:52 pm #1338701
“up high” – not much in the way of livestock & humans & therefore, contamination. your chances are better than mine (Northeast & down-lo) of finding water that does not req. treatment.
“1 micron range” – when you get a spare moment, can you please post back with the website that info came from. 1 micron seems a tad small. remember, sometimes the little buggers might have one dimension that is small (e.g. thickness), but another dimension (their width, for example) is too large to permit them to pass through a filter’s pore. i’m NOT doing a ’bout-face here & advocating a coffee filter, i’m just being a little nit-picky & making a point on the 1 micron.
pjJul 5, 2005 at 2:04 am #1338702
@skaarupLocale: Cold, wet and windy Scandinavia
On this site there is a review, but look further down the page where there is a forum. The marketing manager Katie Bolek from Miox corp., which provide all the tech stuff for MSR, answer a lot of question and provide a lot of info on this product.
This is one of her answers, most are not this techinical.:-)
Qoute from Katie Bolek:
“Since we’re starting with only water (H2O) and salt (NaCl) as feed stocks, we know that any compound created has to be some combination of those 4 elements. These are the known or possible electrolytic reactions at the anode of the mixed-oxidant cell:
2 Cl- = Cl2 + 2e-
2H2O = O2 + 4H+ + 4e-
HOCl + H2O = ClO2 + 3H+ + 3e-
O2 + H2O = O3 + 2H+ + 2e-
The major reaction at the cathode is electrolysis of water:
2H2O + 2e- = H2 (gas) + 2OH-
The bulk solution can also undergo hydrolysis, which does not involve a transfer of electrons:
Cl2 + H2O = HOCl + Cl- + H+
HOCl = OCl- + H+
Here are what those chemical terms mean:
Cl2 = chlorine
O2 = oxygen
ClO2 = chlorine dioxide
O3 = ozone
H2 = hydrogen gas
OH- = sodium hydroxide
HOCl = hypochlorous acid (the more effective disinfecting component of chlorine)
OCl- = hypochlorite ion (the less effective disinfecting component of chlorine) “
Unquote from Katie Bolek.Jul 5, 2005 at 3:07 am #1338703
Minor correction: OH- is not sodium hydroxide. It is a hydroxy group which when combined with a sodium atom will yield NaOH (sodium hydroxide) which is a strong base with a high pH.Jul 5, 2005 at 10:04 am #1338706
Hi Paul-here is the web site I got the info from and a quote regarding the Crypto size
“Also, because Cryptosporidium is pliable, it can fold down to one micron in size, thus slipping through most public utilities filtration systems. The only water treatment devices that can effectively filter Crypto are those certified for submicron filtration (less than one micron).”Jul 5, 2005 at 4:25 pm #1338708
@ryanLocale: Northern Rockies
Please have a look at the current issue of Backpacking Light Magazine (Issue #2) for an in-depth research article about the efficacy of Miox vs. iodine tablets vs. chlorine dioxide solution (Aqua Mira).Jul 5, 2005 at 4:29 pm #1338709
thanks for your speedy reply. i’ve been out of the microbiology field for some time now (30+ yrs). however, i might be mistaken here, but maybe i’m recalling correctly.
i read the article. good info. wish it were a little clearer on a few points. i don’t like to read into things or assume. i think there might be some confusion about the 1 micron issue & the “flexible” issue – at least in my mind.
perhaps this (i.e. “flexible”) is true of what is called the sporozoite stage which is what is released when an ingested cyst ruptures in the small intestine of the host organism. the sporozoite invades the cells lining the small intestine & begins anew the life cycle of this lil’ critter. at this stage they are certainly “flexible” & sorta’ resemble tiny microscopic worms.
i’m not sure, but i don’t think that the thick-walled cyst stage which is released in the feces of an infected animal is “flexible”. however, having said that, just b/c the wall is thick does not necessarily mean inflexible. it is this thick-walled cyst stage that is ingested in the water & in turn causes an infection. the thick walled cyst is approx 4 microns in diameter, if i recall correctly, (it’s not really spherical however), but i may not be remembering this accurately. i suppose we could do a web search maybe that would turn up something more. the thick wall is necessary to at least allow survival as the cyst passes through the hostile environment of the stomach.
however, i guess it’s better to be safe than sorry.Jul 6, 2005 at 8:19 am #1338719
Hello all – I just read everyone’s comments to date. A filter must indeed be 1 micron or smaller to be rated for removal of Cryptosporidium. A coffee filter (or MSR’s “Mug Mate” — http://www.msrcorp.com/cookware/mugmate.asp) would be good for removing particulate material, but not good enough for removal of protozoan cysts like Giardia and Crypto.
Regarding filtering water in case of a catastrophe, here are a couple of links provided on a different forum for a process called “slow sand filtration”:
Typically, municipalities treating surface water will first use a “coagulant” chemical to settle out solids in the water, then filter the water, and then treat it chemically for inactivation of viruses and bacteria.
Regarding time required with the MSR MIOX Purifier, the purifier will actually inactivate all bacteria and viruses within 15 minutes and will inactivate the protozoan cyst Giardia within 30 minutes. The EPA’s Guide Standard & Protocol for Microbiological Purifiers requires a 99.9% (3 log) removal of protozoan cysts. Inactivation of the more resistant Cryptosporidium parvum oocyst is NOT required in the EPA Purifier Protocol. Regardless, in order to measure high levels of inactivation, a very high initial level of oocysts must be used. In independent testing on the MSR MIOX Purifier, the government-qualified BioVir Laboratories started with 100,000 Cryptosporidium oocysts. This excessive concentration of Cryptosporidium would be highly unlikely to occur in natural waters. A 3 log (99.9%) removal of 100,000 oocysts would reduce the viable organisms to 100 oocysts. The MSR MIOX Purifier actually achieved more than 10 times the standard for protozoan cysts, accomplishing a 4 log (99.99%) removal in 4 hours, which equated to less than 10 viable oocysts, even in the “dirtier” test water.
In earlier, non-related studies conducted by the University of North Carolina (which is not a government-qualified lab for purifier protocol testing), the MIOX solution achieved a 95% removal of Cryptosporidium in 30 minutes. Individual consumers can use their own judgment to determine how long to wait — if their immune system is compromised, or they are camping at a site that is likely to be highly contaminated, they should wait the full 4 hours to ensure 99.9% removal of Cryptosporidium. Giardia, viruses, and bacteria will be removed after 30 minutes.
I will have to pick up Issue #2 of Backpacker Light to read the review!Jul 6, 2005 at 9:44 am #1338721
Did a websearch since my recollection was not certain.
From the CFSAN (U.S. Food & Drug Administration Center for Food Safety & Applied Nutrition ) website webpage on Crypto:
“Infectious dose–Less than 10 organisms and, presumably, one organism can initiate an infection.”
Sounds like a 4 log reduction may not be sufficient. However, having said that, I would think that the “one organism” quote above may be dependent upon the individual’s immune system response to the invading critter. However, since it isn’t stated I’m not going to assert that.
Also, from the same webpage: “The infective stage of the organism, the oocyst is 3 um (sic) in diameter or about half the size of a red blood cell. The sporocysts are resistant to most chemical disinfectants, but are susceptible to drying and the ultraviolet portion of sunlight.”
Score one for UV-C purification methods if anyone is keeping score or interested.
Another “fun fact” to know & tell: ” Serological surveys indicate that 80% of the population has had cryptosporidiosis.”
It doesn’t say the sample/population size used in the study, or the demographics of those contained in the study – too bad.
“Intestinal cryptosporidiosis is self-limiting in most healthy individuals, with watery diarrhea lasting 2-4 days. In some outbreaks at day care centers, diarrhea has lasted 1 to 4 weeks.”
The good news for non-immuno-comprised individuals.
“To date, there is no known effective drug for the treatment of cryptosporidiosis.”
This info is a little out of date as there is at least one drug now having “fast track” FDA approval. [read it yesterday on the web, but did not bookmark the webpage]
Here’s the complete URL (now i won’t have to go by my memory any longer – looks like a pretty informative website).
================================Jul 6, 2005 at 10:29 am #1338725
I read an interesting article in the December 2003 Backpacker magazine. It stated that the average infectious dose of Cryptosporidia is about 132, but this figure can vary widely from person to person and from organism to organism. This average value of 132 comes from a study done at the University of Texas Medical School, which found that the necessary level of Cryptosporidium to infect 50% of the volunteers ranged from nine to 1,049 cysts! Fortunately, concentrations in the backcountry are usually too low to make people sick. The same article states that in a 2003 study of 600 water samples from six municipal watersheds, 4% tested positive for viable crypto cysts. The average concetration was only .0068 cysts per liter, meaning that a person would have to drink 1,500 liters of contaminated water over a 24 hour period to ingest an infectious dose! If this is the case, a more than 4 log reduction should be sufficient.Jul 6, 2005 at 1:20 pm #1338731
FDA vs. University. At this point, I’ll go with the FDA until I can find out more about the specifics of how the FDA arrived at <10 as a number causing infection.
Good to know about the levels found in “backcountry” water. How was this determined? I hope the article was not considering municipal watersheds as “backcountry” water. In my area not too many watershed areas get runoff from farm land. Those concentrations came from municipal watersheds, right? Not water passing through farmlands, is that correct? If so, then they may not be representative of relatively low land areas with nearby farmlands or fed by water passing through farmlands. Am i understanding this correctly?
Not sure what the connection is between your refs to municipal water concentrations & the 4 log reduction. If i understood correctly, these were two diff unrelated studies. The muni conc may not be representative of that encountered in the backcountry. Am i missing the point here?Jul 6, 2005 at 2:43 pm #1338734
I would imagine that the FDA is talking about a minimum threshold for Crypto. This would be the most conservative route, considering that the lowest level of infectivity discovered even in the University study was 9 cysts – right on track with the FDA’s statement of less than 10 organisms representing an infectious dose.
The municipal watershed results previously mentioned were from a different study, conducted by America Water, that Backpacker magazine is referencing. In the actual Backpacker magazine study, they utilized Bio Vir Laboratories to check for the presence of Giardia and Crypto in “a variety of wilderness water sources around the country”, rather than municipal watersheds. The sources were sampled three different times between April and July. Here are the sources:
1. Greenwater River (Norse Peak Wilderness, WA) – 0 positive hits
2. Renard Lake (Rainbow Lakes Wilderness, WI) – 0 positive hits
3. White Pine Lake (Wasatch-Cache National Forest, UT) – 1 positive for Crypto, but not viable (unable to cause illness)
4. Neversink River (East Branch, Catskills, NY) – 1 positive for Giardia, but not viable
5. Wet Beaver Creek (Wet Beaver Wilderness, AZ) – 1 positive for Giardia, but not viable
6. Merced River (Yosemite National Park, CA) – 2 positive for Giardia, but not viable
7. Chattooga River (N. of Ellicotts Rock Wilderness, NC) – 2 positive for Giardia – the only sample still VIABLE. (The concentration of cysts here was 1.5 per liter, far below the infectious limit of 10 organisms).
As you can see, occurrences in the backcountry do tend to be at very low concentrations. The only viable sample occurred in N.C., and rather than the 100,000 cysts utilized in the EPA Guide Standard & Protocol for Microbiological Purifiers, there was only 1.5 cysts per liter! Thus, a 4-log removal would be overkill, literally, for the typical level of cysts encountered in the wilderness.
Basically, in the EPA Microbiological Purifier Protocol, they investigate “worst-case” water, represented by a more challenging high pH and low temperature, and then spiked with humic acid and high turbidity before a very large number of microorganisms are added. This water is actually far more contaminated than most waters you would find in the backcountry.
You may also be interested to know of a study conducted by the U.S. military before the purifier was commercialized. Here is a link to a photo of one of the water sources they treated: http://www.miox.com/images/H2O_Source_A_02_small.jpg
As you can see, it’s pretty filthy water, yet the purifier was still effective at inactivating the microorganisms. Essentially, the MSR MIOX Purifier was designed to handle worst-case waters. Most wilderness waters are fairly innocuous compared to the rigorous tests that the purifier underwent.
Please let me know if you have any more questions!
KatieJul 6, 2005 at 3:54 pm #1338735
Many thanks for the clarification.Jul 6, 2005 at 6:08 pm #1338743
Thanks Katie for your detailed comments. As for me–I’m sticking with the Miox—It’s ease of use–lightness–and the ability to purify larger quantities of water quickly are all pluses.
In higher elevations (9,000′ plus) dealig with mtn. streams as a source of water–my read would be to go with the 30 minute formula- Lower elevations or outflow from highly suspect sources–I’d go with the 4 hour scenario.
And that is simply my opinion based on the facts that I have heard.
RonAug 11, 2005 at 12:13 pm #1340178
Thad G FentonParticipant
@ntexhikerLocale: North Texas
Ryan, your magazine article compares Aqua Mira and Miox, but what about Katadyn brand Micropur tablets? Do you have a conclusion as to how this form of treatment would perform against biofilm, compared to Aqua Mira and Miox?Sep 21, 2005 at 5:38 pm #1341882
Data on crypto infectivity varies widely depending on the strain being tested (the same goes for its susceptibility to chemical treatment). The first paper below quantifies three different strains; the second makes the most thorough attempt I’ve seen to quantify risk while taking this variety into account. Bottom line is that wilderness travellers are at VERY low risk, but these might make interesting reading.
Okhuysen, Pable C., et al. 1999. “Virulence of three distinct Cryptosporidium parvum isolates for healthy adults.” Journal of Infectious Diseases. 180: 1275-81.
Messner, Michael J. et al. 2001. “Risk assessment for cryptosporidium: a hierarchical bayesian analysis of human dose response data.” Water Research. 35 (16): 3934-3940.
The following article was the first I’ve seen that identifies a mean infectious dose; it’s superceded by the ones above, but is still intersesting and often quoted.
Dupont, Herbert L. et al. 1995. “The infectivity of cryptosporidium parvum in healthy volunteers.” New England Journal of Medicine. 332 (13): 855-9.
I’m having trouble finding the article Ryan mentioned comparing Aquamira to Miox. Can anyone point me in the right direction?
NeilSep 21, 2005 at 5:50 pm #1341883
@naturephoto1Locale: Eastern Pennsylvania
The article to which Ryan is referring is in the print magazine Backpacking Light Magazine (this is available as an additional subscription), in the current issue (issue #2).
RichSep 22, 2005 at 1:59 am #1341886
thanks for the post.
So…when you’re drinking backcountry water how do you know which strain of crypto might be in it? is it the “good”, the bad, or the ugly???
>>”wilderness travellers are at VERY low risk”
might want to change to read wilderness travellers with healthy immune systems. a number of factors can affect the state of a person’s immune repsonses. based upon the “tone” (you seem much more educated in these matters than i) of your writings, i don’t think i need to mention this to you.
i find it’s dangerous to generalize (we all do it – we just notice when the other person does it). in medicine, each patient needs to be individually evaluated, hence the need for a patient’s med. hist. generalizations just help us to sleep easier if we convcince ourselves that we are on the “safe side” of the statistics. generalizations can also keep us up all night if we think that we are on the wrong side of the statistics. too often we don’t use statistics properly, i.e. we apply them to situations that were not covered by the experiment/study.
my very naive guess is that there is a world of difference in water quality between the high Rockies and the lower woodlands in the Northeast (many farms and water sources which pass through farmland). but hey…that’s just me – i sure don’t have any statistics on this. it’s just a naive guess.
can you provide web links to the articles you mentioned in your posts, otherwise, as refs, they don’t help much since the info is not readily accessible to many who will read your post. i searched for one of the articles and could only find abstracts with no substantive info. i sure would like to read them and learn something.
when you say “supeceded”, i’m guessing you mean by date of study and perhaps also the quality of experimental/study design. if quality of the experimental/study design, what makes the studies just a few years newer, better? CDC has even newer info – 1999-2002 on Crypto. CDC is still sticking with a lower limit of 10 oocysts in healthy persons. for the northeast (even here, farm & population density varies drastically), i have no idea how often it might be present in backcountry waters.
also, one question i still have relates to a prev. poster’s comment, viz. that crypto can “fold” itself down to 1micron. was this the infectious oocyst stage (sort of like an “egg” – typically 3-5microns in size – may contain something like 3 or 4 merozoites)? or was it the merozoite stage (these “hatch”, so to speak, in the intestine & begin moving about – this stage is more elongated)?
i sure do have more questions, than answers on this, and related, matters. any further info would be appreciated. many thanks, pjSep 28, 2005 at 8:20 am #1342140
We are old-timers who are re-entering the backpacking world. In our old days we just looked upstream to see if there was a dead racoon or the like and if not we drank from any swift clear stream. Now we have a katadyn micropur, but our daughter’s friend swears by just plain 4% chlorine bleach, one drop per cup, wait 30 minutes. He has successfully hiked the AT, the Colorado trail, New Zealand using just bleach. We can’t seem to find much on this online. We’re leery of iodine because of thyroid concerns. Anyone know about bleach and giardia/crypto?Sep 28, 2005 at 4:50 pm #1342167
I am marketing director at the water treatment company MIOX Corporation and just saw your post. I wanted to let you know that bleach has no effect whatsoever against Crypto, and although it can inactivate Giardia, it typically takes 4 hours. Also, one drop per cup may not suffice if there are other “oxidant-demanding” materials in the water, such as sulfides or ammonia.
In reality, your daughter’s friend is going to be safe in most cases since protozoan cysts like Crypto and Giardia are more rare than bacterial contamination like E. Coli (which is readily wiped out by bleach). Regardless, there are other technologies out there that provide more thorough treatment and a better guarantee that ALL microorganisms have been inactivated.
One of these is the MSR MIOX Purifier, a 3.5 ounce handheld device that inactivates ALL classes of microorganisms with a 30-minute wait period for Giardia. To read more information and commentary from users, you can visit the forum at http://stuff.silverorange.com/archives/2004/september/msrmioxpurifier.
There are also handheld filtration pumps that include purification to treat all classes of organisms. One of these is the Sweetwater Purification System. The pump itself filters out the protozoan cysts and bacteria, while the bleach addition eliminates viruses. The advantage to the Sweetwater system is that it removes solids from the water and provides more rapid treatment, but the user has to manually pump the water through the filter. The system is also bulkier than the MIOX Purifier, which is an important consideration when backpacking.
Good luck on finding the best system for your needs!Sep 29, 2005 at 1:53 am #1342188
i would like to add one comment here. no…not my usual ones on microbiology so, y’all can breathe easier. (well maybe just one small one – i.e., small for me).
The Sweetwater Filter is the easiest to use pump i have ever used. while the handle folds very flat for stowing, when put in its “in use”/pumping position provides excellent leverage (aka “mechanical advantage”). again, very easy to pump. also, it appears to pump on both the up and down strokes – you gotta’ love those wiley mechanical engineers hard at work. sorry, i’ve never read nor do i count the number of strokes required to pump a liter of water. it’s so easy compared to some other filter pumps i’ve used, that even this OCD, type-A, anal-retentive old man doesn’t feel the need to count them (ok. ok. truth be told, i have counted them, but only once – not anymore – please, don’t ask how many pumps). i don’t even think about “how many more pumps until i fill the bottle” – i find it that easy to pump. of course, there’s always gravity filters (no pumping req’d) like Katadyn’s Camp filter and ULA’s WaterAmigo, or any easy to make “homegrown” varieties – see the product catalog of this website.
ok, as was mentioned, it’s relatively heavy at ~11oz (i think – please don’t trust my memory, i usually don’t, so it should be verified).
finally, last comment, if one wishes to indulge a bit of paranoia and envision water that has every possible nasty microorganism and tiny critter in it that could make one sick (very unlikely, to say the least), then i believe the only sure-fire way to purify the water is to use a sub-micron filter (e.g. the sweetwater filter is a sub-micron filter, as are many others) and then either some type of chemicals to inactivate/denature the viruses remaining after filtration, or one of the two UV-C purifiers currently on the market (these work great on clear water). second best, a 1-2micron cyst filter (i know some of you will say that crypto will still get by – i think that this might be a debatable point – confusion arises due to size differences of the various life cycle stages/forms of crypto, viz , but let’s not get into that here – if someone is interested, start another thread for this purpose) & then use chemicals, or UV-C purification – this will get both the viruses and the bacteria that get by the cyst filter.
for my part, i just use Aqua Mira (repacked in smaller, lighter dropper bottles) – a chemical method, somewhat similar to the also excellent MIOX product mentioned previously.
debates will rage as to which is better AqM or MIOX – both have their good points.
however, if you filter first, then it’s just down to viruses (and taste – ok. baceteria possibly if you’re just using a cyst filter). perhaps, at this point, then, it’s a “coin toss” – AqM, MIOX, or UV-C – they all work well against viruses and bacteria in clear, non-turbid water.
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