Water Purification Systems

by Ric Hubbard • March 27, 2024

Last time, we talked about the common dangers that might be found in water. This time, we are going to take a look at some of the modern systems to make water safe for drinking, and next time we’ll take a look at primitive and improvised methods and tools.

First, let’s clear up some terminology: filtration vs. purification. Filtration removes impurities from the water using a fine physical barrier, a chemical process, or a biological process. It does not necessarily remove all contaminants.

Purification, on the other hand, aims to remove or destroy all contaminants that might exist in water. Filtration generally relies on a physical barrier that allows water molecules to pass through, but catches and prevents impurities from going through. Purification uses various methods to kill biological threats and separate non-biological contaminants from water molecules.

Modern filtration methods will provide safe water if your concerns are bacteria, viruses, and other biological threats (provided that the organisms are not too small). Advances in materials have made filters that can strain out smaller particles and are more efficient than in past years. Let’s take a look at some of the systems available.

Filtration Systems

Reverse Osmosis Water Filters: A system that uses a semi-permeable membrane to separate water molecules from larger contaminant molecules. It uses pressure to overcome Osmotic Pressure, the minimum pressure which needs to be applied to a solution to prevent the inward flow of its pure solvent across a semipermeable membrane3. This removes chemical species as well as biological contaminates, including removing the salts from salt water, producing potable water.

An RO system works by putting the water under enough pressure to cause the water molecule to move through the filter’s membrane, leaving other molecules behind in the “brine” and collecting the “solvent,” the water in this case, filtered and useable.

RO systems are most often used in large scale systems for home and business because of the expense often associated with them, although you can find portable pump filters to take camping or to bug-out. An RO system is the most reliable way to desalinate sea water after distillation. For the prepper, it is more common to use under sink or countertop filters in the home or retreat.

Carbon Filters: Activated carbon, or activated charcoal, is a form of carbon that is processed to have an abundance of low-volume pores with a large surface area for adsorption, the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface4. One gram of activated carbon has a surface area in excess of 32,000 sq ft, allowing for the removal of large amounts of contaminants.

Activated Carbon is relatively inexpensive to produce, making these filters an affordable choice. It is most often encountered as part of a system, and not as a complete system in itself. When contaminated water passes through the carbon, contaminants stick too and are held in the pores while the water molecules continue through the filter, tasting and smelling better. In most cases, it then goes through another type of filter.

Ceramic Filters: Ceramic filters are another type of filter that rely on porous elements to strain contaminates larger than the pores. These filters are effective against bacteria, protozoa, and microbial cysts. These designs are often impregnated with silver to help kill or deactivate bacteria and prevent the growth of algae or mold.

Ceramic filters are not effective against chemicals, so most designs include an activated carbon filter as part of the system. They are also not effective against viruses so a system to kill viruses or a stage in the filter that deactivates viruses is necessary. This type is a fairly inexpensive filter type and is a common type for preppers.

Hallow Fiber Membrane: This is a newer type of filter membrane that is becoming popular. These filters are comprised of bundles of tubes that are microporous, each with millions of pores that are 0.1 micron or smaller. Water flows through these tubes and is forced out through the micropores. With pores this small, bacteria, protozoa, and viruses are filtered out of the water making it safe.

These filters have the advantage of being effective against microbes without being affected by other contaminants in the water—such as salts, pH value, or color. They are also effective in turbid water. Additionally, these systems are usually one of the lowest-cost choices on the market.

Purification Systems

Heat: It is regularly suggested that we carry stainless steel, single walled water bottles as part of our camping or bug-out kits. These are meant to be used to boil water in, to kill biologicals and make water safe. While on the move, these bottles or your cook kit can effectively fill this role, and some redundancy is a good thing.

For larger capacity production, some kind of distillation system can be an effective choice. I am seeing more and more system choices appear from the likes of Amazon.com. Using heat is the most basic way to kill microbes. Boiling will kill biologicals but will not remove chemicals. Distillation will remove some chemicals, as long as the boil point is lower than water, so it cannot be relied on to completely remove chemical contaminates.

Chemical Purification: There are a handful of chemicals that can kill biologicals and have been used successfully for many years. While they are not harmful, they are still chemicals and I feel more comfortable not putting them in my body, especially when there are other choices.

Iodine, chlorine dioxide, chlorine bleach, and ion exchange resins are all chemical purifiers that are effective against biological threats and which are inexpensive. If you decide to use them as part of your water plan, you should have an activated charcoal filter available to manage these chemicals after killing off the biological threats.

Ozonation: This method has been around for quite some time but, thanks to companies like Roving Blue, it is becoming available to regular users. I carry a Roving Blue O-Pen with me every day in my go-bag.

These systems work by producing and introducing ozone into water. This ozone, in turn, kills biological threats in water before dissolving back into oxygen within a few minutes. The system has its drawbacks in that it requires electricity, so plan on making arrangements to charge it in the field.

Ultraviolet Light: UV Light is an electromagnetic light that falls between visible light and X-rays, exists in sunlight, and is produced by a number of manmade devices. Short-wave UV light is ionizing and damages DNA. This effect is why UV devices are useful for sterilizing just about anything, including water.

By exposing water to UV light, biologicals are killed off and the water becomes safe, but again it has no effect on chemicals. You will still need something to filter out dangerous chemicals and suspended solids.


As we can see, there are a number of devices and systems that will produce safe water. In the end though, you might have to use a combination of devices to create a complete water system for emergencies.

All systems can fail, so it is important that you develop the skills to improvise a way to purify water. In a future article, I will look at improvised and primitive water purifying methods that will ensure that you will always have access to clean water.

Sources: Water Filter, Wikipedia – https://en.wikipedia.org/wiki/Water_filter
Water Purification, Wikipedia – https://en.wikipedia.org/wiki/Water_purification
3Osmotic Pressure, Wikipedia – https://en.wikipedia.org/wiki/Osmotic_pressure
4Adsorption, Wikipedia – https://en.wikipedia.org/wiki/Adsorption
Water Filter Guru – https://waterfilterguru.com/purified-vs-filtered-water/
Ceramic Filters, Wikipedia – https://en.wikipedia.org/wiki/Ceramic_water_filter

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