A Do-It-All Water Purifier?

[Douglas Frick]

> When using the filter, do you plan to treat the water with chemicals (i.e. iodine or chlorine, or chlorine dioxide)?

I plan to use the filter where I'm mostly just worried about protozoans and bigger bugs. If viruses or small bacteria, such as Lepto, are a concern then I will use the purifier instead. Either way I can have water immediately without adding chemicals.

Your Seychelle solution works fine, but it does interfere more with the natural taste of the water than a filter/purifier. I haven't used a Seychelle so I can't compare the difficulty of sucking water, but I found the Sawyer Filter to be reasonably easy and the Sawyer Purifier, not. The purifier wouldn't be too bad for sipping from a hydration bladder, but I wouldn't want to use it when I could only drink on rest breaks. I plan to use a gravity-fed Sawyer Purifier in a group situation where I have all night to process several gallons of water.

[paul johnson]

Douglas, for over three decades, Millipore [brand] filters have been used by diagnostic microbiologists performing water quality analysis. I personally used them one summer when working full-time in a one-man (i.e., me) soil and water testing (chem & micro testing) lab.

A Millipore filter is NOT a labyrinth filter. It is just a thin layer of material through which, typically, 100ml of water to be tested is "sucked" into a flask via a vacuum pump. Any little critters remain on the top side of the filter element and grow there when the filter material is placed in a small petri dish containing nutritional media. A grid is imprinted on the top of the Millipore media to make counting of colonies easier.

The ABSOLUTE pore size of a standard millipore filter is 0.45 microns in size. Coliform bacteria are the indicator organisms that are looked for.

For some types of fecal colliform testing, a 0.7 (0.75???, sorry, i forget – i have "old-timers") micron absolute pore filter is sometimes employed.

To keep it short and simple, to main types of "counts" are produced, viz. "Total Coliform" and "Fecal Coliform". E. coli is a fecal coliform.

Also, please remember in the "wild", so to speak (including some wet cultures, but not agar slants and dishes – so making wet preps from a colony picked off of agar is not the best way to get "wild" sizing info), some bacterial cells can grow larger than they do when cultured on agar.

A labyrinth filter is supposed to be designed so that the effective pore size is smaller than the absolute pore size. Of course, this is due to the circuitous/torturous (sp???) path that the water (and organisms) must take through the material forming the mechanical barrier filter.

Now, i really don't know about the Sawyer. If it's NOT a mech. barr. filter, then my comments wouldn't apply. If fact, if it's based on dialysis membranes, then it's probably closer to the Millipore in nature than a labyrinth filter (unless there are multiple offset layers of membrane in the Sawyer???).

Does this info set you mind at ease any? If not, please reply and educate me – if you don't mind.

Also, do you have any idea about the precise nature of the Sawyer filter material and also the construction of the Sawyer filter element? I don't.

Sorry, i don't recall the nominal dimensions (length and diameter) of Lepto.

[Jay McCombs]

ben, to improve flow and decrease sucking force I keep my bladder in one of the side pockets on my pack. That way when I want more than a sip of water I can reach back and add a little squeeze/pressure to the bladder to decrease my need for sucking. Gets harder to do this easily as the bladder gets closer to empty though.

[Douglas Frick]

>Also, do you have any idea about the precise nature of the Sawyer filter material and also the construction of the Sawyer filter element?

PJ, the Sawyer Filter (and Purifier) is a mechanical barrier filter. They describe it as a "Hollow Fiber Membrane (HFM). Very thin hollow porous tubes with uniform pore sizes. They offer a very large surface area in a very small volume. The pore size can be controlled to the extent that virus removal is possible." However, they do not give the pore size for the filter (or purifier).

>Does this info set you mind at ease any? If not, please reply and educate me – if you don't mind.

Not really, because they didn't test the filter with fecal coliform. Their research data states that they used Klebsiella terrigena as the test bacterium (as well as the much larger organisms Giardia and Crypto). They give the organism size for Klebsiella as 2-4um, which is quite large. (Google gives sizes for that organism down to 0.5um.) Thus the filter's pore size could be as large as 0.5um to 2um, which might pass E. Coli (Google gives E. Coli's size as 1um long by 0.1um wide). It might stop smaller bacteria but that isn't supported by the provided lab research or documentation.

>Sorry, i don't recall the nominal dimensions (length and diameter) of Lepto.

Lepto is a 10-20um long 0.1um diameter spirochete which can pass though a 0.2um filter. A filter with absolute pore size of 0.1um, or a purifier or sterilizer, is recommended.

That's why I'm hesitant to trust the Sawyer Filter alone to stop bacteria, based on the information they provide. It should have no trouble stopping protozoans, protozoan cysts and bigger nasties.

[EndoftheTrail]

Doug – thanks for the feedback.

Jay — That's exactly what I do as well. I connect the tubing to my Seychelle and then to the Platy bladder — then place it upside down in my pack's side mesh pocket. This creates a continuous amount of pressure. However, I still have to suck on it noticeably harder to get water flowing — as compared to a setup without the Seychelle.

Would be interesting to compare the Sawyer filter to the Seychelle…

[paul johnson]

E. coli has a diameter much larger than 0.1 microns. If it were only 0.1microns in diameter this would make the flagellar motor area of the bacteria nearly half the diameter of the bacterial cell and this is NOT the correct proportion – maybe 1/10 of the diameter is a more reasonable value, IIRC.

I've seen it literally many hundreds of times under microscopes. I'd say often larger than 0.5microns, but my memory isn't clear on the precise size – it's simply been too long and my memory is not so good anymore. It's certainly less than 1micron in diameter, however. I've seen it less than 0.5microns in diameter, but on cultured agar. I don't ever recall measuring one as only 0.1microns in diameter.

E. coli is regularly counted on Millipore filters. An accurate count wouldn't be possible if the vast majority of the E. coli (and other coliform organisms) managed to slip through the 0.45 diameter Millipore filter. This would make no sense at all, since COUNT is an issue, not merely PRESENCE.

Furthermore, E. coli is a fecal coliform (the most prevalent one in some mammals, IIRC) and can be collected by 0.7micron filters. Again, if it were just 0.1micron in size, using a 0.7micron filter to collect it (and other fecal coliforms) would make no sense at all.

I suspect that Google reference is a "typo", or just plain wrong.

I recall Lepto is a spiral shaped organism that is highly motile. I think it can even be a tad longer than you stated, but your length range is certainly acceptable. Do you live in an area that is known to harbor Lepto in water sources (Hawaii is one known area for instance)? Domesticated and Feral dogs can also be infected and in turn infect water sources. Not sure about wild canines, but if i were forced to wager a guess, i'd vote for them also as resevoirs for the Lepto organism (but this is just a semi-educated GUESS on my part).

EDIT:
Since you mentioned Google. I decided to do a search. Hits had ranges all over the place. This jogged my memory a bit. Often, a bacterial cell will get thinner when it is about to divide. Checking some of the hits showed sizes down to 0.1microns. These seemed to be from webpages that were, IMHO, less reputable, e.g., so-called "Encyclopedia" type of websites (HOW STUFF WORKS – which i've found errors in before in other areas of science, e.g. physics). Other websites, some dealing with molecular biology, had diameters up around 0.8microns. I repeat that i've NEVER seen E. coli only 0.1microns in diameter – nowhere close to that. Most of the sites that i checked had diameters larger than 0.5 and several listed 0.8 as the diameter. Both of these numbers make sense since fecal coliforms (E. coli being one of them) is regularly captured by 0.7micron (0.75micron ??? can't remember precisely) Millipore filters.

I'm really skeptical of some of the info that can be found on the web. For example, the mean time between cell divisions for E. coli are all over the place and differ markedly in many cases from what we actually measured in experiments. However, rarely was the temperature that the bacteria were incubated at mentioned. So, a real comparison couldn't be made. I'd have to assume it was 37C/98.6F though as this is a very, very common incubation temperature.

[Denis Hazlewood]

Ben,
I don't know any "do it all" system. Too many variables. But… Take a look at the Timberline. I believe it weighs 5 oz. I have paid as low as $21.00 for them and replacement filters are about $15. With serious backwashing and maintenance they give me about 3 or 4 years service. I have been using them as my primary water treatment since 1991.

[EndoftheTrail]

Hi Denis:

Thanks… I'll check it out.

You look mighty happy in that Big Sky tent of yours! :)

[Douglas Frick]

>I suspect that Google reference is a "typo", or just plain wrong.

That certainly could be the case (which is why I mentioned the source). I think I diluted my point by mentioning E. Coli. My point was that their test used a bacterium that their lab claimed had a size of 2-4 microns, which is REALLY BIG, although they used a 0.2u filter to collect it. Other sources suggests that that bacterium could be as small as 0.7 microns or 0.5 microns, but that would leave me making claims beyond their lab report. If E. Coli can be collected by 0.7 micron filters, and if their test bacterium is as small as 0.5 microns, then it appears that the filter could stop E. Coli. But why the heck can't they just state the pore size? It's not our job to figure it out…

>I recall Lepto is a spiral shaped organism that is highly motile. I think it can even be a tad longer than you stated, but your length range is certainly acceptable. Do you live in an area that is known to harbor Lepto in water sources (Hawaii is one known area for instance)?

Lepto is helix-shaped, so that 10-20u typical length could be stretched to 60u. Yes, I recently left Hawaii after living there for 15 years, and I'll be visiting there again soon (and hopefully often). Thus my desired filter characteristics are probably more stringent than normal. Anyway, I'd take the purifier just to be safe.

[paul johnson]

Ben,

Well as close as we can get to a do it all filter (filter, purifies, removes some chems/odors; not dissolved salts though as there isn't any reverse osmosis).

First Needs [pump] Purifier – filters, purifies, and removes some chem. taste. Heavy at about 16 or 18 ounces – i forget.

Katadyn ExStream and ExStream EX (be careful there is a similar appearing, other than color which may change from model year to model year) and cheaper Katadyn filter bottle.

ExStream uses iodized gel stage to nail the little buggers that get past the 0.3 micron (IIRC) filter stage. Also, uses activated charcoal stage for some chems/odors. Note the cheaper filter bottle lacks the iodized gel stage, but has the other two stages.

ExStream hold ~21oz and the EX about 34oz, IIRC. Just fill and sip.

First third of volume, easy to squeeze out. Second third, squeeze and suck. Third staqe, squeeze real hard, suck real hard (don't let them lungs get sucked back into the bottle!!!). This is great piece of exercise equipment for building up grip/forearm strength. A genuine dual-use piece of gear!!!

The ExStream weighs about 7oz and the EX version about 7.5oz.

[EndoftheTrail]

Thanks, PJ. I've given up on my quest for the "do it all" purifier — at least for now. Models that can do it all are invariably bigger and heavier, and require lots more sucking power!

Given my dislike for the taste of iodine and chlorine, I now use a combination of (1) Micropur tablets (to kill the smaller stuff) and (2) Seychelle in-line filter (to kill the bigger stuff and remove chlorine and other taste).

The only thing that's less than ideal right now is that more sucking is required with the Seychelle — but it is still pretty do-able.

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