Water is water, but not all water is the same. There is pure water, just combinations of two Hydrogen atoms and one Oxygen atom (H2O). Generally the closest you can get to this is distilled water. This is useful and fairly harmless, although it is hypotonic (has a lower solute concentration than do human cells) and can cause hemolysis (rupturing of red blood cells); this is usually not a major concern even if this is all that is available to drink. Using it on wounds may delay healing a bit; and it might be a problem for people with ulcers (bleeding in the stomach). But this is still way better than no water. On the other end of the scale are various degrees of contaminated water, polluted with chemicals and/or biological organisms, which can make you very sick and even kill you. Salt water can be considered in this latter class as well, even if there is nothing else in it besides the salt. In between are various types of water, all of which are potable (suitable for drinking without major harmful effects).
Determining what water is potable and what is not can be quite a challenge. If it is in a sealed container and properly labeled, then it MIGHT be OK. Labels have been known to be inaccurate (accidentally and even deliberately). If it comes from a municipal tap, then it MIGHT be OK. Just ask the people of Flint, Michigan about that. If it is from a known well, it MIGHT be OK. My dad’s well was found to contain arsenic. And if the water is from an open source, such as a stream or pond, there is a chance it might be OK, but the odds are very high that it is contaminated.
Even if some water does not have anything seriously harmful in it, there might be particulates (sand, silt, plant or insect parts and the like) which would make the water unpleasant and/or things which might be only relatively harmless.
During “normal” times, pre-packaged or professionally provided water is usually tolerable, but if the water infrastructure breaks down for any reason, all water is not to be trusted as is. Open water should always be viewed with suspicion regardless of the state of the surroundings.
There is a tremendous variety of contaminants. Some are “natural”, such a minerals in water drawn from a well, or silt from the bed of a river. Some are man-made, and leaked into surface water accidentally or even deliberately; some eventually work their way into the water table. Some are added accidentally or even deliberately by water distribution networks or packaging. For convenience, let us group contaminates into particulates, organisms, organic chemicals (contain carbon), inorganic chemicals and salt (a special case of inorganic chemical).
Determining some specific contaminates can be done with a “pocket-sized” kit, but many require chemical tests which may be a challenge for people without lab access. But you can get a compact “TDS” meter cheap which will tell you the “Total Dissolved Solids” in your water. As an example, fish tank water gave a reading of 448, tap water read 229, and reverse osmosis water read 17. We don’t know WHAT contaminants are there, but we have an idea of HOW MUCH. Some of these meters also measure “EC” (Electrical Conductivity); pure water is an insulator and it is the ions added to it which makes it conductive, so TDS and EC are closely related.
There are six common, practical philosophies of treating contaminated or suspected water. Each has its strengths and weaknesses.
There may be other methodologies which I am not familiar with, particularly large-scale, but these six would seem to be those of most interest for survival purposes.
Since no method is perfect, often two or more methods are used together.
The most common form of this is “activated charcoal”. This is carbon (charcoal) media which has been treated with Oxygen to create a myriad of tiny pores between the atoms, resulting in a massive surface area of potential chemical bonds. The carbon attracts some chemicals, particularly organic ones, and they bond to the surface (adsorption). These usually cannot be cleaned, so clog up and must be replaced fairly quickly. Also, if the carbon media is granular, some dust sneaks out, requiring a pre-flush of the filter before normal use. Because the intention is for the contaminants to bond with the carbon, we want the contaminants to be in contact with the carbon for a “long time”. Thus, the better ones of these have a slow production rate, and arguably the “best” of these uses “carbon block” technology where the media is fused together into a mildly porous solid.
You have probably heard of one common Ion Exchange device, the ubiquitous water softener. It exchanges two sodium (salt) ions for each calcium or magnesium ion. This is for non-drinking reasons, because calcium and magnesium are often better for you than salt, and tastes better too. For water purification, the process has two different beads which exchange inorganic ions to produce Hydrogen ions and Hydroxyl (OH) ions, which combine to form H2O (pure water) to replace the chemicals. Of course, the ions are used up rapidly, they are for a specific list of chemicals, and the beads need to be regenerated. And of course, this method has no effect on organisms or particulates. These are fairly rare; an example would be the MB series filters from CustomPure.com which also include carbon filtration for some of the things Ion Exchange won’t handle. They claim it can remove “sodium” which is salt, but I doubt it would be able to handle the amount of salt in salt water.
Filtration is very simple in concept. You pass the contaminated water through a medium with holes smaller than what you want to take out. As such, a key specification for any filter is what size the “holes” are. This is usually specified in “microns”, or “micrometers”. That is, one millionth of a meter. Some claim this measurement (micron) is obsolete, but it still seems to be the measurement of choice for filters. Some recent purifiers specify their size in “nanometers”, where 1 nanometer is .001 micron. Keeping with the “metric” measurements, filter capacity (how much water can be processed before replacement) is often specified in Liters (L); for a rough estimate, a Liter is approximately the same volume as a quart, so four Liters is approximately a gallon.
When comparing filters, the one with the smaller holes would seem to be the better choice. The problem is that some companies have varying sizes of holes, and claim the size of the smallest hole in their filter rather than the biggest. Since it is easier for the water to get through a bigger hole and much of it does, this can be a seriously misleading rating. In your final analysis, try to find out the actual percentage of contaminants removed. This is the most accurate way of determining filter effectiveness. Another term which can sometimes be used in a misleading manner is water “purifier”. The correct use of this term is for a unit which removes the much smaller viruses. Units which remove particulates and organisms as small as bacteria are simply to be called “filters”.
Some filters become “plugged up” quickly and are rated for a specified number of gallons (or liters), while others can be cleaned and restored to service or even are self-cleaning. Reverse osmosis (RO) is a prime example of purification and self-cleaning. It forces the water through a semi-permeable membrane and continuously washes any contaminates off of the source side of the membrane. This is a very effective system (see the TDS meter example above), but requires the water to be pressurized, and worse, the wash water now has an even higher level of contamination than it had at the beginning. In many systems, you “throw away” as much as four gallons of water for each gallon purified. I’ve heard of one household system where the wash water is fed into the hot water line rather than the drain, but I’m not seeing how the pressure in that line is overcome.
Other filters run the gamut from several layers of cloth or a coffee filter, suitable only for large particulates, to 0.01 micron (or less) water purifiers; from pocket-sized to counter-top and bigger. Since the smaller the holes, the slower the filtration and the more likely it is to clog up, often filter systems have multiple filters, starting with a pre-filter for “chunks”, course filters for large particulates, possibly some medium-sized filters and ending up with the finest filter. Smaller holes require more “energy” to force the water through the holes; this can be from gravity, or more effectively, a pump or suction.
In filters (i.e., won’t remove viruses), perhaps the most compact and simplest to use is the “Lifestraw“. This is rated at 0.2 micron, with a 264 gallon capacity. It is light, easy to carry and reasonably priced. To use it, stick the input end into contaminated water and suck the water from the other end just like from a straw. It takes a few seconds of sucking to start delivering water. There also seems to be a Lifestraw Steel model, which adds a metal body and an activated carbon filter to remove some chemicals. This latter part is replaceable, which is good because its capacity is 26 gallons, only a tenth of the main filter capability. Another popular compact option is the Sawyer Mini system. This is rated at 0.1 micron, and can be cleaned to provide up to 100,000 gallons of filtered water. It can be pressurized by squeezing a pouch of contaminated water, or used inline with a hydration pack, from a standard soda bottle, or used as a straw from an open source.
As for portable purification, an example is the pump powered MSR Guardian, rated at .02 microns and with about a 2500 gallon capacity. Another, bigger option is the Lifestraw Family, rated at .02 microns and with a 2600 gallon capacity. I found a particularly compact suction powered (straw) system which sounds promising; the Etekcity 1500L rated at .01 microns with a 396 gallon capacity, but don’t know anything about the company. They have a wide range of products, so it’s not like they specialize in water purification.
A countertop system is an option at a fixed location. An example of this is the gravity powered Big Berkey (actually, the whole Berkey family). This company doesn’t provide a micron rating since it can be misleading as mentioned above; they stand on their contamination removal percentages. Their filter cartridges have a capacity of 3000 gallons per filter element, with two to four elements installed in the system. More elements don’t filter any better, just faster. Not only is it very effective against virus (and bigger things), but many chemicals as well. And you can get an add on filter for each element which takes out Fluoride, Arsenic and a couple of other additional chemicals, with a capacity of 500 gallons per add-on filter.
Tune in for Part 2, which investigates the other four purification methods.
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