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An Overview of Water Purification Methods

Critical But Plentiful—A Commodity Taken For Granted

I’m sure you remember your High School science teacher telling you how the body is over 80% water and how three fifths of the earth’s surface is covered with water.  It seems to be everywhere.  It’s so common and in such profound supply we take it for granted.   Our generation has grown up with water delivered to nearly every household in the country via an elaborate network of piping systems.  Every home has it available in an unending supply.  There’s always been plenty of water to wash the car, wash the dog, fill the pool, water the lawns and spray at your neighbor.   And yet, ironically, during times of crisis, clean, drinkable water is the first thing to disappear.


Your Municipal Water Supply Is Fragile

A lack of clean water can be devastating to you and your family more quickly and more severely than even a lack of food. Without water for both drinking and continued good sanitary practices in food preparation and for bathroom excursions (which will inevitably be much less sanitary than normal), debilitating sickness could rampage through your household with little hope of prompt medical attention. That is a highly likely but, avoidable, disastrous scenario.


As an example of just how vulnerable our municipal water systems can be consider the case study of Milwaukee, Wisconsin a few years ago.  The runoff from a cattle pen entered a stream feeding the municipal water supply.  Cryptosporidium, present in the runoff, was impervious to formerly conventional water treatment methods (chlorination in this case) and ultimately infected a total of 450,000 people with various gastrointestinal disorders.  A total of 110 people with impaired immune systems actually died as a result of the contamination (84 were HIV positive and the balance were all receiving chemotherapy).


Depending on the nature of the crisis, often the only safe water to drink is that which you have either stored or that which you have prepared yourself.  The effects of the ingestion of contaminated water during times of crisis are something you must avoid at all costs.  This is no time to be sick.


As common and as benign as water seems to be, that does not make it simple to store for long periods of time.  Water has the ability to encourage bacterial growth if not properly prepared.  Bacterial growth in water over long periods of time not only contributes to odor and bad taste, but it can also make the water toxic to drink. 


Storing an adequate supply of water in a manner in which it will be readily available for emergency purposes presents a unique problem set:


Problem #1—Water is absolutely essential for life

Of all the things you can do to make the aftermath more comfortable for you and your family; most of them are optional rather than urgently critical.  Water is not one of them.  In extraordinary circumstances, the human body can go for weeks without food, but it will expire in a matter of only a few days without water.  Long before this, however, even after only eight hours, dehydration can handicap you with extreme headaches, cramping, nausea and even hallucination.  A crisis situation is not the time to challenge your body with one more source of stress with the associated drop in your energy, alertness and decision-making capabilities.


Problem #2—The body requires a lot of water

The amount of water lost from the body averages about 2.5 liters (about 2 quarts) per day at a minimum.  Exposure to high temperatures, dry air and physical exertion can all serve to increase the loss of body fluids above this level.   Thus, to supply a family of four with just the minimum requirement of drinking water for a period of a month totals about 60 gallons—the approximate equivalent of the ubiquitous 55-gallon drum.  Adding in enough for basic hygiene and cooking can easily double this requirement to over a hundred gallons.


Based on the usage guidelines used above, a good estimate is to plan for at least 4 quarts (1 gallon) per day for each member of the family for basic survival.  Therefore, for a typical family of four the amount of water to be prepared and stored for a week of self-sustenance would be about 28 gallons.  That would be roughly 6 of the typical 5-gallon jugs you might use for camping.  Six jugs just for a week.  That takes up a lot of space.


Problem #3—Stored water can grow bacteria

Because water has the ability to serve as a breeding ground for bacterial growth, water must be properly prepared and treated for long term storage by disinfection.  Then prior to use, this stored water must be rendered drinkable.


Problem #4—Stored water has a shelf life

Because of the potential for water to grow bacteria or become stale, it is generally recommended to changeout your stored water every six months.  Given all the other priorities in daily life, and from surveys and basic observation, it is clear that only the most dedicated and disciplined members of our population have a regular program to provide this rotation.


Your Options:

There are a number of possibilities for assuring a supply of emergency drinking water.  Each approach has its own advantages and disadvantages.  Many of these factors will be determined by where you live and the nature of your lifestyle.


If ever there was an area full of hucksters and sales hype the area of residential water treatment is it.  But in spite of the outrageous and fantastic marketing claims, many of these systems are actually quite effective.  But in order to sift fact from marketing enthusiasm any discussion of water purification is only rendered meaningful in the context of a discussion of the types of contaminants that can be present in water in crisis situations.  It is only with a full understanding of what you are up against can you intelligently deal with the challenge and properly understand, evaluate, and appreciate the technology available in some of the new systems that are available.


Contaminants can be divided into seven key areas:

  • Microbiological organisms
  • Microscopic plant life (algae)
  • Organic chemical compounds
  • Inorganic chemical compounds (chlorine, sodium fluoride)
  • Salinity (salt/sea water contamination)
  • Radioactive particulates
  • Esthetics (taste, color, smell, clarity)


Microbiological Organisms:

The principle source of contaminants in this category will be from sewage cross contamination.  The microorganisms can include:

  • E-coli
  • Salmonella family including S.Typhosa (of typhoid fever fame)
  • Cholera
  • Klebsiella terrigena
  • Shigella.


Next will be the larger protozoa (1 micron in size and above) such as:

  • Giardia Lamblia
  • Entamoeba
  • Cryptosporidium
  • Tapeworms


Treatment Method:  Filtration

All of these contaminants are effectively removed with 0.4 micron or finer absolute filters. 



What filtration cannot remove are viruses due to their exceptionally small size.  Fortunately most viral infections are respiratory rather than waterborne.  These include:

  • Polio myelitis virus, Type 1
  • Rotavirus Strain SA-11
  • Hepatitis


Treatment Method:  Disinfection

Viruses are usually attacked effectively with either chlorine treatment, ozonation, an iodinated filter medium or through the use of UV sterilizers.


Microscopic Plant Life:

The most common form of this contaminant includes the various forms of algae.  You will probably recognize it from the green film that grows on the inside of your aquarium glass when the water goes out of balance.  This is a result of warm water, in the presence of both oxygen and sunlight.


Treatment Method:  Filtration & Disinfection

The growth of algae is controlled by removal via filtration and is prevented with disinfectants like chlorine or iodine or through the use of UV sterilization.


Organic Chemicals:

By definition, organic chemicals are those relating to compounds of carbon and therefore include such chemicals as gasoline, diesel fuel, pesticides and many complex chemical compounds found in conjunction with chemical plant spills.  They will also be one of the weapons of choice for a terrorist bent on contaminating a municipality’s water supply.


Treatment Method:  Adsorption

Organic chemical removal from water uses a mechanism known as “adsorption” and is usually accomplished with activated charcoal or carbon filter blocks.  Most advertised water treatment systems contain charcoal filters for this purpose.  The most important thing to realize is that the mechanism of adsorption is a finite method.  That is, the filter can only adsorb up to a certain amount of pollutant effectively until it must be either replaced or re-generated.


Inorganic Chemicals:

Chlorine, sodium fluoride, asbestos and fiberglass fibers are the most common contributors in this category.  However the heavy metals such as lead, arsenic, mercury and cadmium can also be present.  Fortunately, by using sub-micron filtration as used for bacteria and with adsorption as used for organics, these compounds should not be much of a problem.


Treatment Method:  Filtration/Adsorption Combination


Salinity (Salt Water Contamination):

It is ironic that while over 80% of the earth’s surface is comprised of water, most of it is salt water in nature.  This is probably the toughest one of the contaminants because of its near total dissolution into the water.


Salt (sodium chloride) is known as a dissolved mineral.  Other dissolved minerals include, calcium (calcium carbonate), potassium (potassium chloride), iron (iron oxide), and various compounds of sulfur.


Treatment Method(s):  Distillation, Reverse Osmosis, Ion Exchange

The most common method to remove dissolved minerals is via distillation.  These systems are energy intensive which does not make them necessarily the best choice during times of crisis when energy may be at a premium. 


Instead, dissolved minerals can also be removed from water through a process called reverse osmosis. These systems are widely used on ocean-going pleasure boats and cruise ships and involve a system that forces sea water through a semi-permeable membrane under high pressure.


Additionally, the ion exchange process can also be used wherein a special filter containing certain minerals in resin form will preferentially acquire the sodium ions.  These systems are somewhat more expensive on an ongoing basis, requiring regeneration or replacement of the ion exchange resins.


Radioactive Fallout:

Consisting principally of Iodine-131, Strontium-90 and Cesium-137, these will be air/wind-borne particles in the size range from 0.1 microns up to about 10 microns.   Iodine-131 is considered the isotope of primary concern because of the body’s affinity for it.  The thyroid gland wants to absorb iodine in any form and as fast as it can find it.   


Treatment Method:  Filtration

As these pollutants are particulate in nature, their removal is accomplished by sub-micron filtration.  Contrary to popular belief, they do not render the water itself radioactive.  Rather, the water is radioactive solely due to the presence of the radioactive particulate.


Esthetic (taste, color, smell, clarity):

By now it should be apparent that all of these characteristics are a result of the presence of the various contaminants described above.  Color, opacity (referred to as turbidity) is generally due to the presence of dust or dirt particles characteristic of asbestos fibers or heavy metals. 


Treatment Method:  Filtration & Adsorption

Smell is affected by the presence of both the organic and the inorganic chemicals such as the chlorine smell you detect when you smell your pool water.  Both color and smell can also be affected by any of the contaminants from dust to bacteria to the larger protozoa and various forms of algae.



With the above understanding in place it should serve to help to explain why many of the more common beliefs about water purification are not totally correct.


How many times have you heard people say they were going to boil water to purify it?  The American Red Cross of all people actually suggests that by boiling questionable water for 5-10 minutes it will be fit to drink.  You can now see that this will do nothing to remove fibers, heavy metals, diesel oil, or radioactive dust.


Or how about Halazone, Globaline or iodine tablets (Tetraglycine Hydroperiodine) or “Javel” or Potassium Permanganate?  The commonly held belief is to simply drop a tablet into a canteen and the water is fit to drink.  Once again you can see that this method does not address the whole problem.  With what you now know, how do you feel about just running your questionable water through a particle filter?  Organic chemicals will simply pass right through.


Based on the foregoing analysis of the universe of contaminants and the associated treatment methods, effective water treatment methodology can be simplified and summarized by the acronym “FADD.”


                F = Filtration

                A = Adsorption

                D = Disinfection

                D = Demineralization


This will make it easier for you to remember in the future when you are evaluating any commercial water filtration systems.  Depending upon your raw feed water source, you are looking for systems that incorporate elements to accomplish at least each of the first three key functions.  The fourth function, demineralization, is added for comprehension of the need to remove the salt if sea water is your supply source.


The Ideal Water Treatment System:

The question has often been asked, “If you were going to put together the ultimate water purification system from the ground up, what would be the key elements that one would assemble?”


Step 1—Pre-Filter:

This filter is very large pore size and catches what are called boulders.  Essentially, the visible mud, dirt, hair, lint and other large debris is captured at this step with a relatively inexpensive filter membrane that can be changed often.   The pre-filter’s key purpose is to protect the more expensive elements of the filtration/treatment system from debris and premature saturation.


Step 2—Disinfection:

Any living organisms, plant life, yeasts, and fungus must be killed before they are captured or you are simply creating a pile of growing virulence in your filter media.  There are several ways to do this.  The simplest and most reliable method is to use an ultraviolet (UV) sterilization module.  Commercial facilities perform this step either by introducing chlorine or through ozonation (ozone injection). 


Manufacturers of camping filters will use a specially treated filter and thus combine this step with Step 3 below.  Filters of this type are either treated by impregnation with either iodine or a silver compound.  Recall that silver is exceptionally toxic to micro-organisms.  This prevents so-called “grow-through” of the bacteria (mitosis).


Step 3—Desalination (Optional):

If there is a chance that you will be challenging your purification system with water containing dissolved salt, this step will remove all dissolved minerals.  This step typically requires fairly significant fluid pressures and may require the addition of a booster pump in the circuit.


Note:  If you include this step, it will preclude the need for Step 6, indicated below.


Step 4—Micro-Filtration:

This absolute filter is sized down to as low as 0.05 microns and will filter out just about any form of particle that could conceivably be in the water.


Step 5—Organic Compound Removal:

The water is now ready to have both organics and inorganics removed.  The astute observer will notice that any chlorine or iodine that may have been introduced in Step 2 is now being removed.  That’s precisely what we want at this stage.  Neither chlorine nor iodine is particularly tasteful and with the water already disinfected, their usefulness has been outlived.


There are actually two methods at your disposal to perform this operation.  The first is adsorption via activated charcoal.  The second is through the use of a high power ultraviolet system that literally breaks down organic compounds into their fundamental hydrogen and carbon elements.


Step 6—Dissolved Mineral Removal:

Through what is called a mixed bed of ion exchange resin any dissolved minerals are removed.


Very few camping filters contain this feature.  In fact, their instruction book will specifically state to assure not to attempt to use their filter for sea water purification.  As long as your supply is not contaminated with sea water, a camping style filter will work fine. 


Based on the ideal, now let’s look at a few commercially available purification products and see how they match up with their features.


The “Hiker” Microfiltration System

As an illustrative example of a commercially-available, convenient system, let’s consider a product called “The Hiker” by a company called “PuR/Katadyn.”


The Hiker can be purchased for about $60.00.  It weighs about 11 ounces and is roughly 3” in diameter and about 7” long, making it easy to carry.  It features a built in pump that you actuate by hand to suck in feed water and push it through the filtration elements.  Since no electrical power is required, it is ideal for international travelers, campers, hikers and bicyclists.  It also makes it ideal for your automotive emergency kit or even in your home emergency kit.


Purified water output is at a rate of about a quart per minute and its filtration elements are good for up to 200 gallons depending upon the quality of the feed water.  Be aware that if the feed water you start with is heavily contaminated with organics or particulate, the filter element will load up quickly.


It uses the following treatment steps:

  • Pre-filter (in the form of a float that contains a 1 micron filter element)
  • Carbon block adsorber
  • Ceramic filter
  • Iodine-impregnation of the ceramic filter (for disinfection of biological pathogens)


As can be seen, it contains features to fulfill all of the first three of the basic elements.  The only contaminant this system will not remove is dissolved minerals such as salt from sea water.



Here’s a purifier that can render water from any source safe to drink.  Bulk water from a lake, a pond, the gutters, swimming pools or spas, even mud puddles can be made potable.


Leading Edge Technology:

Each year, thousands of new products and breakthrough technologies vie for the attention of editors at Popular Science magazine.  But only the best of the best—those products that inspire awe, envy, and admiration—are awarded inclusion in their category, “Best of What's New.”  Two years ago, the MSR Corporation won the Grand Award in the new General Innovation category for this purifier.  The MIOX Pen has been the recipient of dozens of other awards for technological achievement.


Principles of Operation:

The MSR MIOX Purifier makes water microbiologically safe using ordinary salt and an electrical current.  A small amount of oxidant solution is made by dipping the top of the pen in water or placing a small amount of water in the top of the pen.  Then a tiny amount of ordinary table salt is added.  Shake, and add the solution to water.  Proprietary patented technology creates the tiny batch of an oxidant solution which is mixed with your water to destroy microorganisms.


Alternatively, you can make the solution ahead of time and keep in a small bottle.  MIOX uses a chemical reaction called electrolysis to create a powerful disinfectant that will destroy biological contaminants in your water.  It is more effective against microorganisms than chlorine or iodine.  It also features a safety indicator so you can be sure your treated water is safe to drink. 


It is suggested that you add a package of cheap coffee filters to store with your MIOX in case you ever need to purify water with visible debris in it.



The MIOX is compact, rugged and submersible.  It purifies water without iodine; no health risk or unpleasant iodine taste.  The powerful dose of mixed oxidants it creates is then added to untreated water, inactivating all viruses, bacteria, Giardia and Cryptosporidium.


The purifier will treat approximately 300 liters of water on one set of batteries. The purifier can be used over and over, making water treatment an inexpensive procedure.


MIOX uses a chemical reaction called electrolysis to create a powerful disinfectant that will destroy biological contaminants in your water.

  • More effective against microorganisms than chlorine or iodine
  • Destroys viruses and bacteria in 15 minutes, giardia in 30 minutes and cryptosporidia in 4 hours
  • Features a safety indicator so you can be sure your treated water is safe to drink
  • Comes with 1 ounce of salt to treat 300+ liters of water; 2 lithium CR123 batteries; 50 test strips; instruction book; reference card; storage bag
  • MIOX is compact, rugged and submersible
  • Purifies water without iodine; no health risk or unpleasant iodine taste


MSR MIOX kills viruses. The large, expensive filters don't work on viruses.  The MSR MIOX kills everything, including hard-to-kill and nasty Cryptosporidium.  It does large amounts.  This purifier is used by our troops in Iraq and Afghanistan.  Mixed oxidants eliminate chlorine taste and odor, do not react with chloramines to cause foul-smelling compounds, improve taste and odor from algae and lake turnovers, precipitate iron that can cause an earthy taste or odor, and they oxidize sulfides, effectively removing the "rotten egg" taste and smell of H2S.

An important feature of using simple salt as the disinfectant source is that salt has an infinite shelf life, so the purifier will still function even if stored without use for a long period of time.  The lithium batteries have a 7-10 year shelf life. 


The disinfectant will inactivate a number of common pathogens, including E. coli, Giardia, and Cryptosporidium, as well as chemical and biological warfare agents.  The purifier has passed the EPA Guide Standard and Protocol for microbiological purifiers, achieving more than 10 times the level of inactivation required, even in the EPA's "worst-case" water.


Even Effective Against Chemical/Biological Warfare Agents

Dugway Proving Ground, a U.S. Government laboratory, has been testing the MIOX mixed-oxidant solution since the year 2000 on biological and chemical warfare agents.  Findings show high efficacy against all agents, including Anthrax spores.  Mixed oxidants achieved up to 99.99% inactivation of the spore, depending on the dose and contact time.

The mixed-oxidant solution also effectively destroyed the bacteria associated with Plague and the viruses associated with smallpox and polio.  Mixed oxidants were also extremely effective against the nerve agents Soman (GD) and V-Agent (VX) and the blister agent Lewisite (L).


The X-Pack:  Grab & Go Evacuation Kits, Automotive Kits, Apartment Dwellers

Instead of trying to store bulk water and preserve it, one option is simply to be prepared to purify water when the time comes.  One unique product to do this is a system called the “X-Pack” made by Hydration Technologies, Inc., was originally developed for our troops fighting in the Middle East.  It is the ideal portable water purification system.


The Technology:

The X-Pack consists of a plastic pouch with two compartments in it separated by what is called a semipermeable membrane.  You use it by filling the one side with dirty, contaminated, or suspect water.  You then add to the other side a specially-formulated syrup from a small bottle supplied with the kit.  This syrup is formulated much like the concentrate for a typical sports drink like Gatorade in that it contains various salts and sugars that are used to provide the “osmotic pressure” needed to draw the water molecules through the membrane.


Once charged, the X-Pack will produce 1.75 liters of the equivalent of a sports drink containing about 4% sugar (this compares to Gatorade at 6% and soda pop at 12%) in about 8 hours.  Thus, it can be re-filled three times a day and produce a total of over 5 liters of hydrating drink per day. 


Each X-Pack is good for a total of ten days of use after first use.  This limitation is based on the useful estimated time before bacterial growth overwhelms the membrane and begins to breakthrough to the clean side.


The membrane has a pore size of 3-5 Angstroms which is 100 times smaller than the smallest pathogens.  It is capable of blocking bacteria, viruses, heavy metals and can even reduce the concentration of salts and most pesticides.


Storage & Shelf Life:

Each X-Pack is guaranteed for a minimum 3 year shelf life when stored below 90˚F.  It can be stored safely at temperatures ranging from -40˚F up to 160˚F without damage.


Purification Performance:

The effectiveness of the filtration can be summarized as follows:


Contaminant                                         Rejection Rate

Bacterial Pathogens                             99.99%  

Radioactive ions                                  100%

Chemical Warfare Agents                  95%

Pesticides                                              95%

Odors                                                     95% (See Note 1)

Heavy Metals                                       85-90%

Salt                                                         not currently effective (See Note 2)


If your bulk water supply is substantially salt use their alternate product called “SeaPak” from Hydration Technologies, Inc., which is designed specifically for salt water purification.



  • Portable and ready for evacuation.
  • Ideal for both home and car.
  • No empty water bottles to exchange.
  • No need to learn about water purification, storage, or containment.
  • No moving of heavy 5-gallon water jugs around the house.
  • The technology does not use any of the traditional chemicals for purification
  • The technology selectively pulls water molecules through the membrane instead of using a pump to forcefully push all compounds against a filter membrane and letting only water get through.



  • This is a water purification method and not a water storage method, thus requiring the ready availability of bulk water.
  • Note that it produces a liquid similar to a sports drink rather than simply clean fresh water.
  • Time consuming—requires 8 hours per batch.


Sea-Pack Emergency Portable Desalination System

SeaPack removes pure water from the sea and transforms it into a drink that is high in calories to provide life-sustaining energy.  The passive system is portable, compact, easy-to-use and low in cost.  During an emergency situation at sea, reliability and simplicity are vital.  SeaPack makes a survival drink from any available water supply—salt water, brackish water—even muddy water.


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