Caracas is a bustling city, stocked with high-rises, art centers, universities, zoos, and beautiful parks. It has also, through a period of astounding government mismanagement, become unable to provide water to its residents.
All across Venuzuela, citizens who can afford it are having to drill their own wells in the cities. Poorer people are scraping by with trucked-in water or very intermittent service. Read about it here.
One problem is that the water sources that are available in big cities are generally very nasty, filled with every kind of contaminant. As I was considering how I as a prepper would get by if that was the only water available, I settled on my choice of purification method: Distillation.
Why distillation?
There are lots of ways to purify water: distillation, filtration, reverse osmosis, chemical treatments, ultraviolet light. No one does a perfect job; all have their strengths and weaknesses. I’ll get into that more in a later post. I settled on distillation for my ‘make water that’s contaminated with a wide variety of nasty things drinkable’ choice for two main reasons:
Distillation handles a wider array of contaminants than most methods. Everything infective, including bacteria, protists, viruses, and even prions is either killed or left behind in the dregs.
Distillation removes most organic chemical contaminants, such as residues of most oils and solvents, gasoline, pesticides, herbicides. It also removes salts, so it gets rid of dangerous heavy metals including lead and mercury. That’s most of the stuff I’d worry about being in the water. (1) I’d be confidant in drinking distilled water from my pond, or even a random ditch.
The method is prepper-friendly. A still can be produced from a wide array of materials that are all around us. It doesn’t take any specialized components such as the membranes critical to reverse osmosis. It’s easier to do with electricity of course, but can be done using other heat sources.
The design of stills is also such that you’d know if something bad had happened. If a filter fails, your first hint might be that you caught a disease; but if a still’s coil fails the leak will be a dead giveaway.
How does distillation work?
In distillation, you have some fluid you want to purify — such as water. You heat the fluid, capture the vapor that comes off, and cool the vapor to make it re-condense to fluid again and collect the result.
When you first start heating, while you’re below the boiling point of the water, the first things to vaporize are chemicals with lower boiling points. The very first fluid that condenses is rich in these low-boiling-point contaminants, so you throw that first bit of fluid away. If I were collecting rain run-off in a city, there would be a whole lot of residues of oils, gasoline, and other unpleasant organic compounds in that very first sampling, and I’ve now gotten rid of most of those.
Once you reach the boiling point of water, most of the vapor is water molecules. The fluid that recondenses is now very much improved water. I’d collect that and feel free to use it for any use without further treatment if need be.
It tastes rather flat (since appropriate additives like some salt and oxygen improve water’s taste), but it’s good stuff. Since I heated the water to boiling, I also destroyed any microbes, including the hard-to-filter viruses, that were in my original collection.
The last bit of fluid (I always went with about 10% of the starting volume when I was doing this professionally) is enriched with things that have higher boiling points than water. This includes the toxic heavy metals.
I’m sure my collection water from the city also had way more lead and such than I wanted to drink, so the last bit of fluid gets discarded.
How could a prepper make a setup for distillation?
What you really need is:
- A big container for the starting fluid that’s got a sealable top to which you can attach a coil or tubing.
- A way to heat that big container
- Coils or tubing that the vapor flows through while it’s cooling and recondensing
- A collection container at the far end of the coil or tubing
This will give you the basic idea: Chamber to heat in, vapor collection and cooling, fluid collection.
You can get a setup easily by buying a moonshine still, but there are a million different ways to get the essential components, so if you know what you’re trying to do you could make a still from a wide range of scrounged components.
This is an example of a moonshine still one can buy. You’d want more copper coils between the original and collection chambers for better efficiency.
The cooling is most efficiently done by having the coils run through cool water. If you don’t have that water to spare, though, you can just build longer coils. Copper is great for coils because of its inert composition (it won’t add anything back to the water) and it’s great heat exchange (for quick cooling), but lots of other options would work. It might not be as efficient, but it’d work.
What are the downsides of distillation?
No one method does a perfect job of purification. Distillation has three main weaknesses.
One is that any contaminant that has a boiling point similar to water is not effectively removed; it ends up in the vapor with most of the water. This means that a random selection of organic molecules might not get removed very well. Due to the underlying chemistry, you’ll never remove 100% of any contaminant by this method.
All microbes will be killed by the boiling, but the occasional heavy metal ion or organic molecule will get caught up in the vapor and end up in the distilled water. Removal of most components ranges from ‘pretty good’ to ‘only a trace remains’ but never goes to ‘completely clean’. As water supplies go, that’s usually fine; but it is a consideration.
Another downside is the energy investment. It takes a lot of energy from some source to heat all that water. That’s a minor flaw in some circumstances but a fatal flaw in others.
The last downside is portability. You’re not going to be hiking out of anywhere with your still on your back. For on-the-go purification, you have to look at other options.
1) Drinking water treatment: Distillation. 2018. University of Nebraska Extension. http://extensionpublications.unl.edu/assets/html/g1493/build/g1493.htm