Thursday, April 28, 2011

Survival Resources 10: Safe, Clean Water

When I was writing about 'Needs', I did a post on Water (5/10/09) where I mentioned 'the rule of three': "you can only live 3 minutes without air, you can live 3 days without water, and you can live 3 weeks without food." Recently I repeated a similar rule in my post on Wilderness Survival (Survival Resources 8, 3/11/11), "A person can go a few minutes without air, a few days without water, and a few weeks without food..." What these rules don't tell you is that if you do drink water and it's contaminated, you could be very sick for several days, or even die.

Unless you can figure out a way of capturing rainwater in a container that is absolutely clean, then the water you are drinking may well contain stuff that's really not good for you. The issue isn't so much about finding clean water; the issue is how to clean the water you have so it is safe and drinkable.

There are two ways water can be contaminated, and so there are two different ways to clean it. The first way that water can be contaminated is by water borne pathogens. There are many organisms that live in water that can cause diarrhea or worse.

A major method for treating infected water is called SODIS or solar water disinfection. This method uses clear plastic (PET or polyethylene terephthalate) bottles which are filled to three-quarters with the water in question, shaken (to aerate), and then completely filled. Water that is turbid (not clear) should be filtered until clear before doing this. The bottle should be placed at an angle on a reflective metal surface (a corrugated metal roof is ideal) for six hours on a sunny or partly cloudy day, or for two whole days if the day is mostly to completely cloudy. This method is used on a world wide basis for safe drinking water.

The second source of contaminants for water is chemical--heavy metals, organic compounds, and even the chlorine that municipalities add as a method of water purification. The question of the health hazards of chlorine is controversial. The American Chemistry Council insists that the amount added to drinking water is safe, but other sources (especially from companies that sell water filters) disagree. Wikipedia notes: "Disinfection by chlorination can be problematic, in some circumstances. Chlorine can react with naturally occurring organic compounds found in the water supply to produce compounds known as disinfection byproducts (DBPs). The most common DBPs are trihalomethanes (THMs) and haloacetic acids (HAAs). Due to the potential carcinogenicity of these compounds, drinking water regulations across the developed world require regular monitoring of the concentration of these compounds in the distribution systems of municipal water systems." The woman who taught me water and soil testing when I took RUST (see my post on RUST, 7/13/10) was adamant about the dangers of carcinogenic substances in chlorinated water.

SODIS is no help with chemical contaminations--here some type of filter is needed. The most common is some sort of 'charcoal filter'--the commonly sold Britta filters are an example--and there are many more expensive, sophisticated types out there.

The combination of using SODIS to disinfect the water and a filter to get rid of chemicals should result in safe, drinkable water. There are other methods that work as well (such as solar stills). For more information on making sure water is safe, see the chapter on Water in When Technology Fails by Matthew Stein. (I reviewed When Technology Fails on 12/13/10 at the beginning of this series.)

(I want to thank my friends at DIO Skillshare for giving me much of this information.)

Quote of the Day: "Until roughly ten years ago, no one ever considered it unsafe to drink directly from mountain streams. You could stretch out on the bank of a high mountain meadow creek and just push your face into the water to drink. ... But no longer can we ... drink even a drop before purifying it without running the risk of getting sick." - Kathleen Meyer


Austan said...

Thanks for writing a clear and simple explanation of water issues. Since moving, I notice a huge difference in the water here from what we were expected to drink downtown. Though it's the same source, the plumbing here is not 120 years old, which is potentially a contaminant in itself. I couldn't keep up with the weekly changing of the filter there!

MoonRaven said...

You are on target about plumbing as a contaminant. Many great sources of water have to go through lead pipes or pipes with lead solder--leading, of course, to lead in the water.

I hope many things are better in your new place. Thanks for the comment.

Hans said...

'm really confused when it comes to getting clean and safe water to drink. I've read that most water from lakes and rivers in Sweden (my home country) is safe to drink but then I've read that you should NEVER drink water straight from a river or a lake, NOWHERE. As for cleaning the water I've read that boiling is all you need to do, but then I've read that that might actually make the water more toxic, in some cases, if there's a certain type of algae in the water. I've also read about this natural type of filter you can make on your own, by charcoal, pete and moss but then I've read that that might make the water dirtier in some cases. Then I've read that doing both is the best way but I've also read that not even by both filtering it and boiling it you'll get safe water. Then I've read that in my country, Sweden, we have probably the safest tap water for drinking in hte whole world and now I read that tap water might not be safe to drink because of the chlorine. Needless to say, I am more than confused. Humans have been around for thousands of years so there got to be some way of making that water safe to drink or otherwise we would have been an extinct species long time ago. Could anyone help me out here? There seems to be a lot of different opinions, even among scientists.

MoonRaven said...

You raise a lot of good issues. Unfortunately, I'm not a scientist and I'm not sure of all the answers here.

Two pieces that I think are correct: if you've got tap water that is otherwise really good, running it through a charcoal filter should remove the chlorine, and if you have some way of capturing rainwater directly into a clean vessel, that should be pretty safe to drink (unfortunately, not absolutely, with industrial contaminants, even the rain isn't pure water).

To respond to why humans have survived this long,first, a lot of these contaminants are because of our recent industrial age, and second, biological contaminants have been around a long time and are responsible for many epidemics (such as cholera) that have wiped out huge parts of the population in the past.

Still, I think with collective work and creativity we can deal with these problems.

Thanks so much for your thought provoking comments.