How can you survive the apocalypse? Part Two: Water

Okay, so now you’ve sorted out the cosy shelter where you’re going to hunker down and ride out the collapse of civilization, it’s probably time you took care of your number one physical need: clean drinking water.

The bad news is with nobody home at the district water plant and your local supermarket overrun with flesh-eating zombies, turning on the tap or glugging bottles of Evian isn’t going to be an option anymore.

So where can you get your aqua vitae?

First off, we all know we can’t drink salt water (remember Waterworld?), but why is that? The answer lies in the process of osmosis. This is the movement of water from a less concentrated solution to a more concentrated solution through a partially permeable membrane–such as a cell wall. Your cells have a fairly low salt content. If they are surrounded by fluid with a high salinity–like they would be if you drank salt water–then there will be a net movement of water molecules out of your cells in an attempt to balance these concentrations. Unfortunately, this means you will dehydrate and eventually die.

No glugging from the sea then. Where do we find fresh water? Three main places: surface water, rain water, and ground water. Out of these three sources, ground water is the most naturally clean due to being filtered through the very Earth, but wherever you find your water it will still be advisable to undertake a number of steps to remove all contaminants.

The elements that make the water unsafe come in two varieties: pathogens and impurities. A simple filtration through a cloth or shirt sleeve will remove some of the larger impurities of grit and dirt, but to get rid of all of them and the pathogens a number of other methods will be required. If creating a fire is not a problem, then boiling your water will ensure all pathogens are killed. Of course, if you’re surviving at altitude due to a nanoplague outbreak that kills all warm-blooded life below 10,000 feet, you’ll need to add extra cooking time due to the boiling temperature being lower. If fire’s not an option, leaving the water standing for several days will allow impurities to settle out and most pathogens to die. In hot climates a combination of solar radiation and heat will kill the bacteria. Simply seal the water in a glass bottle half-painted black and lie it in on its side on aluminium roofing in the sun for the day.

And, if you’re really stuck in Waterworld with no “dry land”, then you can always knock-up a solar distillator that will cleanse the water of salts, pathogens, and impurities in one fell swoop. In its simplest incarnation a tray of impure water sits sealed beneath an angled piece of glass. Exposure to the sun evaporates the water leaving free of salts and impurities, and killing the pathogens. The water then condenses on the surface above after which it runs down the inside of the glass by the action of gravity, collecting in a trough. Simples.

Kevin Costner might’ve had webbed feet and gills, but I didn’t rate his DIY skills as I never saw his solar still . . .

Now you’ve had a refreshing–and safe–draft of the best drink on the planet you’re probably getting hungry. Tune in next week for giving your apocalyptic dinner a scientific once over!

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