The difference between water purification versus filtration is that purification eliminates viruses, whereas filtration does not. Most purifying systems use a chemical component to destroy viruses in addition to regular filtration.

Goals
Filtration and purification seek to remove chemical contaminants and disease-causing organisms from your drinking water. The most common pathogens fall into three major groups: protozoa, bacteria and viruses.

Filters and purifiers remove chemical contaminants using carbon in a process called adsorption whereby contaminants bond to the carbon and are sucked out of the water.

Protozoa, bacteria & viruses
Generally, the greatest concern is killing those nasty little critters that live in water and wreak havoc on the human body. Protozoa, such as Giardia and Cryptosporidium, are the number one threat; followed by viruses like hepatitis A; and finally bacteria like E. Coli.

Filters remove the larger microorganisms, protozoa and bacteria, but no filter is small enough to remove viruses. “[It’s] impossible to filter anything less than 0.2 microns*,” says Eric Miller, Sales Representative to MSR (Mountain Safety Research), “so viruses must be killed with chemicals.”

Purifiers use a chemical disinfectant—iodine being the classic example—to eliminate viruses. To be called a purifier, a treatment must be registered with the U.S. Environmental Protection Agency (EPA) and meet stringent standards.

Who needs purification?
Anywhere you’re recreating in areas that see heavy human traffic—popular trails or campsites—there is the chance that viruses lurk. Purifiers are ideal in these situations.

While viruses are generally not as big a concern in the U.S. backcountry, protozoa like Giardia and Crypto are pervasive, albeit to different degrees. Filtration eliminates these protozoa efficiently.

If you’re traveling to developing countries where waterborne viruses are more common, a purifier is a wise choice; the most popular being the First Need Deluxe.

Traditional chemical treatments like iodine often impart a foul flavor to the water, and can take up to 45 minutes to work. Aqua Mira is an excellent alternative, and though not officially classified as a purifier by the EPA, it will eliminate the majority of waterborne pathogens. Used in conjunction with a water filter such as the MSR MiniWorks, this is a very effective purification system.

An interesting alternative to chemical purification comes in the EPA approved Hydro Photon Steri-Pen. Look for other cutting-edge alternatives from MSR this fall.

 

* A micron equals 1/1000 of a meter. The smallest item visible to the naked human eye is 25 to 30 microns. Protozoa are as small as 2 microns, bacteria 0.25 and viruses a miniscule 0.01.