Water Pasteurization?

Q

Quirt

Joined
Oct 10, 2005
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I'm really surprized I haven't seen more threads or any threads (unless I just missed them) on Water Pasteurization using either fuel source methods (wood or fuel stoves) or solar ovens.

I've been very slowly warming up to the concept after having all my wilderness authority figures, instructors, schools and mentors, hammer into my head for over 40 years, to the point of paranoia, that one needs to fully boil water to drink/cook with it.

And now my graduate degree Microbiologist friend and fellow wilderness bum is saying I only need to now warm my water up to 65-66 C (150 F) for 6 minutes in order to pasteurize the water making it safe to drink, thus using less fuel or no fuel at all to make water safe and usable.

It is my understanding a rolling boil kills everything whereas pasteurization kills all of the "evil" bacteria, viruses, and other microbes but doesn't kill everything.

Talk to me on what you've learned, know about this theory and also what methods you're using for pasteuization (assuming you are) or if you think this is junk science and not worth discussing.

PS I'm not in anyway advocating or promoting this at all; I'm just wanting to learn more and either to validate or refute this theory of making water safe to drink/cook.
 
You are right, lots of varying information on the subject which I think goes beyond what is in the water, i.e., hygiene.

Nonetheless, the number I have heard is 185 degrees. Whether it is 150 or 185, a boil let's you know you hit 212, so unless you have a thermometer AND a watch, boiling is the indicator.

You may appreciate this video I posted in another thread yesterday...

[youtube]0GUTZS7QBPs[/youtube]
 
Yes indeed, boiling is indeed the best method of indicating when you've achieved the correct temp and to produce the most effective method of making the water safe. For Pasteuration one needs a thermometer or a WAPI device (Water Pasteurization Indicator) to indicate when the approprate temp has been achieved. This method is probably not practical for everyday wilderness (recreation) use but could be useful if in an urban survival situation when fuel is scarce or the environment is so hostile one doesn't want to compromise where one is located or knowing what you're doing (Hey everyone, look over here! I've got a fire so I might have some water, food, and other things worth stealing and killing me over).

Since I travel extensively great distances from home base for my work, I thought this might be something to explore further in the event of a catastrophic failure and I'm a long ways from home and do not have access to unlimited fuel or cooking means to clean my drinking water. Solar while quiet, odorless, and stealthy takes time to construct and to work. While it isn't ideal, it is another tactic to squirrel away in my bag of tricks "just in case."

My other option is to drop by my WSS brothers house for a helping hand assuming I'm in your region!

There is more on this site - http://solarcooking.org/pasteurization/metcalf.htm
 
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One reason for the conflicting information on water temperature is that water boils at 212 F at sea level, but 186.4 at 14,000 feet. Also, giardia and crypto are harder to kill, thus the recommended higher temps. cryptosporidium is a supercyst and is only killed by boiling. Iodine and chlorine can be ineffective at killing it.
 
In the world of microbiology there is a concept referred to as "infectious dose" and it is the minimum nunber of organisms (bacteria, viruses, etc.) that will produce an infection in most people... Most people with intact immune systems can fight off "small" numbers of bacteria, viruses, etc. Almost nothing in the real world is sterile. We all get minor penetrating injuries (with "clean" penetrators) from time to time and yet most of these wounds never get "infected". That is because the number of bacteria introduced is below the infectious dose...

What the infectious dose is varies from organism to organism. Some bacteria have very low infectious dose numbers... I read (years ago) that the infectious dose for the bacterium that causes typhoid fever is 200 organisms... you can fit 200 organisms on a piece of dust or the point (not the head) of a very sharp pin. The infectious dose for Hepatitis B virus for penetrating injuries is so small it can't be measured (last I looked). If you get poked with a needle that came from an active hepatitis B patient (and you are not already immune (because of previous infection or vaccine) and don't good medical care), your probablity of coming down with hepatitis is 100%! The infectious dose for most organisms is much higher than the numbers for typhoid or Hepatitis B.

Pasturization doesn't kill all (100%) organisms (of any given species) but it does kill most - up into the 90%+ range. Whether it is good enough to make water safe is based on the number and specific species of microorganism contaminants. If a water source is contaminated with the typoid fever bug, I'll guarantee that pasturization is NOT adequate to prevent infection (fortunately, typhoid fever is rare in the US). Since it essentially impossible to know how many and which types of bugs are in the untreated water that you have access to, merely pasturizing it (i.e. not boiling it) equates to taking an unquantifiable risk. I think you should only use pasturization as a last resort... if it is the best you have, use it but otherwise, boil questionable water when able. If the water source is "good" it needs no treatment - when I was younger, I used to fish for trout in beautiful, crystal clear, spring fed creeks in the mountains... on more than one occasion, I drank unteated water straight from the creek. I have never gotten sick as a result... Looking back, I now realize that I was taking an un-necessary risk and would probably not do that in the future... Then again, I used to eat raw clams/oysters too... I don't do that any more either...

I hope this was helpful... ;)
 
Codger_64 said:
cryptosporidium is a supercyst and is only killed by boiling. Iodine and chlorine can be ineffective at killing it.
Click to expand...

UV will inactivate crypto, but I'm not sure how effective the little hand-held units are at making this happen.
 
Anyone ever try the Aquapak ? looks interesting.

http://www.spheralsolar.com/products/AquaPak.html

In laboratory testing the AquaPak killed 99.99% of the pathogens that were present in the water. The pack achieves this by using solar energy to get the temperature of the water inside over 65 degrees C. The pack can take 4 to 5 liters of water at a time and it can take around 2 hours to reach pasteurization temperatures, simply fill it with water and lay it down flat in the sunlight. The pack can be refilled many times a day, allowing it to pasteurize enough water for a family of four to use in countries with bright, hot days.
Click to expand...

[youtube]NCB1yfNHIQU[/youtube]
 
This is a good topic.

I look at it like this, if meat is safe to eat after it reaches an internal temp of 165 or so, so should water after a few minutes. Meat sits at 165 to 180 degrees for a few minutes in an oven. It's not like it climbs to 212 degrees before you can get it out, so it's probably sitting at 165 or so for a few minutes or more killing everything in it.

So my logic is high temps for a short time, or low temps for a little longer time and either way is safe.

If we can't get a boil out of the water, we let it go five to ten minutes above 165 and we have never been sick. Do you cook meat until it hits 212 degrees? No, because you will dry it out as the moisture boils out of it.

Also, as soon as it hits a boil, it's done. It's pointless to let it go for several minutes in my opinion, because it has already been above 165 for some time already.



One thing I have done a couple weeks ago, is I made a suggestion to Swiss Army Knives to make a high temp thermometer to check water temps, and make it with a point so it can be used at as meat probe to check internal temps while cooking on the trail. I can't really tell if something is done in low light or darkness, so a high temp cooking thermometer would be great.
 
How much more fuel do you think you will use to get your water to 212 degrees for 30 seconds than you use to get it to 150-185 degrees for 6 minutes? Not to mention, as was stated earlier you need to have a thermometer and watch to pasteurize it.
 
As I stated earlier...probably not a lot of application for recreational useage. But if in a particularly urban longer-term survivial situation for many people fuel consumption becomes a real concern. So the use of Solar can produce pasteurization while it cannot bring to a rolling boil.

I proposed this not as a subsitute but rather as a consideration as a "uh-oh, we have a problem here" alternative IF fuel becomes an issue and if living in a hostile environment where fire, smoke, and light can and will compromise one's safety and survivial.
 
I'm surprised no one has mentioned this yet...no need for all that fancy gear...all you need is a clear plastic PET bottle.

Wikipedia "solar water disinfection". After you read the article go to the references and links at the bottom of the page and do some reading. It's no theory...it's used around the world. It's a verified and effective method.
 
Forgive the long post but I wanted to comment on some of the information here.

Greybeard said:
How much more fuel do you think you will use to get your water to 212 degrees for 30 seconds than you use to get it to 150-185 degrees for 6 minutes? Not to mention, as was stated earlier you need to have a thermometer and watch to pasteurize it.
Click to expand...

Water needs to be at a roiling boil for at least 1 minute (3 minutes above 6,500-ft.) to be considered safe according to the CDC.

I think pasteurization is effective but using it to conserve fuel may not be practical. For it to be reliable and safe the rules must be followed which would require a thermometer. I'm also not certain that the 150-185 degrees for 6 minutes is sufficient. I'll do some more research.

Boiling is probably safer and more reliable because is easy to see when a rolling boil has been achieved instead of depending on a thermometer.

Codger_64 said:
One reason for the conflicting information on water temperature is that water boils at 212 F at sea level, but 186.4 at 14,000 feet. Also, giardia and crypto are harder to kill, thus the recommended higher temps. cryptosporidium is a supercyst and is only killed by boiling. Iodine and chlorine can be ineffective at killing it.
Click to expand...

Actually iodine and chlorine are extremely effective disinfectants and capable of "inactivation" of both crypto and giardia when used appropriately. Chlorine is used in most municipal water treatment plants as the primary disinfectant and is dosed to the distribution systems in small amounts to prevent bacterial regrowth.

Using any oxidant as a disinfectant will require the combination of an effective dose and adequate contact time. The effective dose and contact time are dependent on the pH, alkalinity and temperature of the water. Most of the available water purification tablets claim inactivation of crypto but do require a contact time in excess of 4 hours.

JCavSD said:
UV will inactivate crypto, but I'm not sure how effective the little hand-held units are at making this happen.
Click to expand...

I agree, UV is very effective. It disrupts the DNA/RNA of the organisms which leaves them unable to reproduce and therefore cause any harm. The catch is that again, inactivation requires an effective UV dose for an adequate contact period. The effective dose depends greatly on the clarity (or more specifically the "UV Transmittance") of the water. In my opinion, I don't think that the current UV products on the market are foolproof enough to reliably provide adequate treatment in the varying conditions that they will be used.

For me it comes down to wanting to be safe than sorry. I carry water purification tablets in my kits and will continue to do so. They will be effective as long as the directions are followed.

If I need to heat water to make it safe I will probably boil it for at least twice the recommended time! :thumbup:
 
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Dr. Bob Metcalf is the director of Solar Cooking International and a leading scholar on this science. He has written and published extensively.

http://solarcooking.org/pasteurization/metcalf.htm

For those of you throwing temps around, here are the temps he has listed:

Worms, Protozoa cysts (Giardia, Cryptosporidium, Entamoeba) = 131 F

Bacteria (V. cholerae, E. coli, Shigella, Salmonella typhi), Rotavirus = 140 F

Hepatitis A virus = 149 F

He commented that 1 minute at these temps is 90% effective and when sustained at these temps for a full 6 minutes it will take it to 5 log or 99.999% effective.

Here is a summary of his study/research including the table where I found the temp data - http://solarcooking.wikia.com/wiki/Water_pasteurization

Again, I'm not advocating anyone try this or use this method. This is only information that one could squirrel away in the back of one's brain and use as an "in the event of an emergency break glass and use . . . " Myself, personally, I'm still boiling, filtering, and UV'n. But I'm also experimenting with the solar technology and this technique so I can use it if I ever need too - and let's hope I never do need too!
 
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