boil water to clean it

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poussin

Joined
Jan 28, 2003
Messages
95
Hello.

Assuming you have no water-cleaning pills, I was wondering how long you have to boil water to make it drinkable (I mean, you know, without getting in trouble with your guts after...), assuming it comes from a very small stream which flowed through some small villages before, loading up with some sewage water.

Thanks.
 
Theoretically, water is safe as soon as it comes to a rolling boil.

The catch is in the physics of what you are trying to do, namely rip all the bugs to crap with heat. You are essentially trying to denature their proteins and destroy their other bodily structures and kill them.

If you get some of the water in your pot to boil, there may still be small pockets of cooler water where the germs can survive. Boiling for some period of time, say, 3 minutes, assures that all of the water has reached a temperature lethal to whatever bugs may be in there.

Another catch is altitude. Water boils at lower temperatures at high altitude. The implication is that the lower temps are not AS lethal to the germs, so they must be exposed for a longer time to assure their deaths.

Still another problem is viruses and other simple pathogens. They denature sure enough when boiled, but they reconstitute as soon as the temperature drops. These guys have to be ripped apart chemically, with something like iodine or bleach.

Scott

PS: Sewage will almost certainly contain a lot of viruses. If you drink boiled effluent water, you will probably get hepatitis, but not e-coli.
 
donutsrule :D no worry, around the place I go fishing, people have barely heard of electric fridges, and if they need water some of them just tell their wife to go and bring a bucket back from the well. I think some of them do not suspect the existence of energy sources other than wood and animal heat, so they have not shoveled through their mountains looking for Uranium yet.
 
Boiling in a pressure cooker will benefit several ways. The temperature will be higher, the pressure greater, boiling time is reduced, and less water is lost in the boiling process..

Like donutsrule said, boiling does not remove anything from water. It will denature proteins, many but not all permanently. But it will not remove any chemicals except low pressure volatile organics. In other words, it will drive off alcohols and esthers and some other stuff, but it also drives off some of the water, which brings us to the down side:

Boiling makes water dirtier. The water may indeed become sterile, but after boiling off 5 to 30% of the water, the concentration of sediments, dirt, heavy organics, minerals like lead and uranium, and many poisons, if present to begin with, will be at higher concentrations after the boiling process. Water that had pollutants below EPA concentrations may now have them above the magic line. The bugs may be dead, but any poisons produced or carried that are not deactivated by heat, as in the basic food poisoning bug, will just increase in concentration.

I remember reading about a group of people stranded on an island in sight of a major US city for a couple of days. Saltwater all around. They were burning 3 bon fires continuously to signal for help. They had no potable water. They were sopping dew off of the grasses. Seems to me that all they needed was tubing and a "lid" with a hole in it to distill the seawater in any cup or pot. Efficiency was not an issue, the fuel was burning anyway, and lots of cool seawater to cool the tubing......
 
Bleach (sodium hypochlorite) will help with some of the non-biologics. A non-toxic example, you can remove dissolved Iron from your water by oxidizing it with bleach. The oxidized iron comes out of solution as a dust. I don't know a lot about the chemistry involved, but I suspect you can remove most of those contaminants with an oxidizing agent such as bleach.

The trade-off is that heavily oxidizing organic contaminants (microbes and tannins - plant color) can create trihalomethanes, which are carcinogens. In the water treatment business, activated charcoal is used to remove them in systems where bleach is used for disinfection.

Scott
 
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