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Water Rights: A Quick Course in Filtration Education
By Martin Vilaboy

Filtering mountain water in early Spring
Portable water treatment suppliers used to spend significant time and energy warning backcountry travelers about the possibility of microscopic contaminants even in what appears to be clean water. But today, most people don't even trust the H20 that pours straight from the tap. No matter where you live or visit in the United States, it seems like the locals emphatically state how their municipal water is rated the worst in the country.

Currently this country is in a craze for clean water, and even casual campers and travelers are expressing serious concerns over tap water in hotel rooms, rest stations and campsites. These folks traditionally have turned to bottled water for security, but a recent study by the National Resources Defense Council shows how bottled water may not be any safer than tap, while costing consumers as much as 10,000 times more per gallon.

The changing attitude toward drinking water means increasing questions about water purification, with concerns well beyond just backcountry water conditions. In turn, a wider selection of products is now available.

To help you understand these new products, and to answer your basic water safety questions, we provide this quick review of water treatment technology.

Choose Your Poison

A logical place to start a discussion on water treatment is with the reasons why we need these systems in the first place--the little critters and compounds that infect our water supply. There are basically two categories of contaminants to consider: chemical contaminants, such as metals and agricultural pesticides, and waterborne pathogens, the disease-causing microorganisms known affectionately as germs.

While a few chemical contaminates are deposited naturally, they are typically the result of agricultural run-off or industrial by-product. This, of course, is not an issue when recreating up in the mountains, far from the nearest processing plant, but it can be a problem for urbanites that play just outside of town or downstream from a mine or tailing pile. However, even in the worst scenarios exposure is limited. Most waterborne toxins have a cumulative effect on the body, meaning the damaging effects build up in a person's body throughout a lifetime. In recreation situations, the concentration levels are usually too low and exposure terms too short to pose an immediate health concern. But then again, it all adds up.

Ingesting just one microscopic waterborne pathogen, on the other hand, can make a person violently ill in a matter of hours; so most filter companies focus primarily on microorganism removal and, secondarily, on chemical reduction. In most cases, waterborne pathogens use an animal or human body as a host, whereby they rapidly reproduce. A person may ingest only a couple of microorganisms, but after getting sick, could defecate several million. The little creatures that cause us alarm come in three general categories: protozoans, bacteria and viruses.

Protozoans are hard-shelled, single-celled parasitic cysts ranging in size from 2 to 100 microns. (One micron equals one-millionth of a meter. Please see the section "Micron Management" below.) The largest of the waterborne pathogens, protozoans are the easiest of the three to remove from water by filtration, but some can be difficult to kill via iodine, chlorine or the like because of a protective shell that resists chemical water treatments. The two most common and publicized protozoans are Giardia lamblia and Cryptosporidium.

Probably the most prevalent parasite in American waterways, giardia cysts range in size from 8 to 12 microns but have been known to squeeze through holes that are 5 to 6 microns in diameter. Giardiasis is contracted by drinking water that an infected animal or human has used as a toilet. The disease is characterized by a weeklong bout of diarrhea, which usually manifests five to seven days after ingestion, along with possible bouts of abdominal cramps, fatigue and weight loss. Although most mammals can carry giardia cysts, the primary offenders are beavers and muskrats because they spend most of their time in and around the water. Floating along in cool water, a giardia cyst can survive up to three months, and consuming as few as one to 10 cysts can make a person ill.

Cryptosporidium is slightly smaller than giardia, able to pass through a 3-micron hole. After ingestion, it takes two to four days for crypto to make you ill, and the symptoms of cryptosporidiosis are almost identical to giardiasis. Also similar to giardia, crypto is transmitted through a fecal/oral path (deer, elk and cattle are known carriers), and can survive for several months in cold water. Unlike giardia, chemical treatments like iodine or chlorine cannot be used to effectively treat crypto. It must either be boiled or physically filtered out of the water.

Bacteria are the next smallest of waterborne pathogens, with some measuring as small as 0.2 micron. A few of the more familiar bacteria include Escherichia coli (E.coli), Shigella and Salmonella. Here again, bacteria are transmitted through a fecal/oral path, potentially leading to diseases ranging from diarrhea and dysentery to cholera and typhoid fever. Some bacteria are found only in human feces, while others can be present in both domestic and wild animals. Larger bacteria, like salmonella (0.6 micron), can be removed by filters with an adequate pore size. Smaller bacteria require the work of a purifier, rolling boil or chemical treatments.

Viruses are the tiniest microorganisms but are arguably the most problematic. It was traditionally assumed that viruses were not a concern in North America, but recent studies counter that assumption, and today, most experts believe that viruses pose more of a waterborne threat than bacteria. Sporting a diameter as thin as .004 micron, viruses are too small to be effectively removed by filtration, requiring the use of heat, chemicals or a purifier. Also transmitted by the consumption of fecally contaminated water, most viruses typically lead to temporary intestinal problems, but some can cause more serious diseases like hepatitis and meningitis. At this point, the more severe viruses have a very low occurrence rate in North American waters.

Get it Out Of My Glass

Now that we know what can infect the water, it's time to look at the various methods for cleaning it up. Besides boiling, which is still the most effective method, (although not the most efficient since it takes time and spends valuable stove fuel) there are three areas from which to choose: chemical treatments, filters and purifiers.

As far as portable treatments, the most commonly used chemical is iodine. Safe and simple, iodine attacks and kills just about any critter one will encounter, bacteria, viruses and protozoans. It will even neutralize some chemical contaminants. It does not, however, protect against cryptosporidium, which has recently proven to resist most, if not all, chemical treatments.

The PUR Explorer water purifier

Iodine is available in tablets, liquid or crystal form, and although it is a favorite among old-school backpackers, there are a few drawbacks. First off, iodine must sit in treated water for up to an hour, depending on water temperature, before it can be consumed. Secondly, iodine will do little or nothing to change the appearance or taste of murkier waters, and iodine can even make the water taste worse. Fortunately, some companies supply neutralizers that mask the iodine flavor.

Typically made of ceramic and/or fiberglass, filters work by physically trapping individual particulars, much the same way as a colander strains spaghetti. In most instances, water is forced through an element consisting of a network of nooks and passageways. The smaller the passageways or pores of the filter element, the more intestinal enemies they trap and kill. To make things simple, the pore size of a filter element also is measured in microns. Pore sizes of filters sold in outdoor stores range from 0.2 to 2.0 microns.

Filters with a pore size as low as 0.2 are sometimes referred to as microfilters. The number 0.2 is significant because it indicates that a filter should protect against just about every known protozoan and bacterium. This is more than sufficient in the defense against crpyto and giardia, but nowhere near small enough to cut down rotavirus (as low as .070 micron), Norwalk virus (as low as .027) or most of their virus buddies.

Unfortunately, defending against minuscule viruses is not as easy as reducing pore size to .004 micron. A filter's element can only be so tight before the flow rate becomes immeasurable. Trying to filter water through pores measuring .004 micron is equivalent to pushing water through a brick. So when the possibility of encountering viruses exist, it's time to consider a purifier.

A purifier is essentially a filter that is proven to remove or neutralize 99.99 percent of viruses, as well as 99.9999 percent of bacteria and 99.9 percent of protozoans. Purifiers bypass the pore-size problem by combining filtration with either a chemical treatment or proprietary secret that work to either remove or poison the tiniest microorganisms. Since purifiers add some steps to the process, they can cost more and often require more maintenance than non-purifiers. But for the consumer who wants to be absolutely sure she is drinking clean water, the extras shouldn't be much of an obstacle.

Complete protection from all microorganisms is not the only kind of security a user gets from choosing a purifier. In order to be called a purifier, a system must be registered with the EPA and pass the guidelines mentioned in the previous paragraph. At this time, regular filters do not face similar requirements.

A normal filter with a pore size of 2 microns or less can be made to perform like a purifier with the help of a little iodine added to fight off viruses and smaller bacteria, or the addition of an iodinated cartridge, which is often sold to upgrade filters.

Pump or Squeeze

After choosing the level of protection, the next step is picking the format. Up until recently, portable water treatment systems required either the power of gravity or hand pumping to force water through a system. Because of new technologies that have improved flow rates, filters and purifiers now can be housed within the neck of an ordinary sports flask.

The water bottle systems offer added convenience, cleaning water with a simple squeeze of a hand and unsurpassed freedom, providing an individual with a quick drink without the hassle of external tubes and extra containers. On the downside, sport flask systems were created to quickly re-hydrate an individual, and are not efficient for serving large groups or cleaning all the water needed for typical campsite chores. In those instances, a pump is still the way to go.

In the end, there are basically two major considerations when choosing a water treatment system: ease of use or repair and effectiveness. However, there is only one reason to carry the system: to protect your health against microbiological and chemical contaminants. Therefore, a product's effectiveness should ultimately influence the final determination.

Every brand and model has avid supporters and harsh detractors, so personal preference will be a factor. But regardless of preference, a design is adequate only if it works to avoid cross-contamination between inlet and outlet fittings, is maintained in the field, is rugged and reliable and provides clean and refreshing drinking water. If not, you better be ready to boil.

Micron Management

A micron is a unit of measurement used to gauge the minimum diameter of a microscopic particle. One micron equals one-millionth of a meter or .00004 inch. To put it into perspective, the diameter of a human hair ranges from 50 to 150 microns.

Microns are also used to measure the pore size of a filter. A filter's pore size indicates which particles it will trap and kill and which particles it will allow to pass through into your drinking glass. For example, if a filter has a micron rating of 0.4, it is effective against any particulars of that size or larger.

Micron ratings (or pore sizes) are given as nominal, average or absolute. Nominal ratings mean a filter will remove up to 80 percent of organisms that size or larger. An average rating indicates the average size of all the pores, meaning some will be smaller and others larger than the given number. An absolute pore size means no pore in the entire filter element is larger than that number. To be entirely safe, consider only absolute ratings when choosing a filter or purifier.


Martin Vilaboy is the Editor-In-Chief of Outfitter Magazine, an outdoor industry trade publication for outdoor retailers.


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