Which Filtration?

For many, converting to filtered tap water has become a way of life. It is a way to live greener, reducing our carbon footprint from the days of thoughtless plastic bottled water usage. Avid hikers and backpackers often know the ins and outs of chemical water treatment to remove bacteria and parasites, as well as filtering for a cleaner taste and less sediment. However, for most people, deciphering the many types of filtration methods and deciding which is the best choice for a given location, even homes and offices, can be daunting.

Most of us remember distillation from secondary school chemistry. Water is boiled, cooled, and re-condensed, leaving behind contaminants. However, this method uses a great deal of energy when compared to its alternatives, and also doesn’t remove pesticides or other organic matter. The resulting water has a flat taste, lacks valuable mineral content and is acidic enough to warrant storage in glass containers. This is certainly not the best filtration, but effective when other methods are not an option.

De-ionization might be even less desirable in some situations, however. It doesn’t remove particles as well as distillation, but the resulting water might taste better and be safely stored in plastics for longer.

More familiar in recent years, primarily due to its neutralizing effect on taste, is carbon filtration. It removes odors and chlorine as well, but not heavy metals or dissolved solids. While activated carbon can remove chemicals, gasses and sometimes microorganisms, it doesn’t soften the water and leaves behind heavier metals, and sometimes, carbon “fines”, a fine powder. For that reason it is best combined with the method which most leading water bottling plants rely on -- reverse osmosis. It is the most cost-effective way to remove 90% or more of water contaminants.

Ridding water of lead, asbestos, radium, dissolved organics, turbidity and pesticides, reverse osmosis can also offer the best protection against plutonium and strontium. Though the latter are rarely found in drinking water, they can be a concern for those who live near nuclear power plants.

So, while the variety of water filtration methods can be confusing, it has yielded a number of inventions that are improving drinking water across the globe, where filtered municipal tap water is a goal that won’t be realized for decades to come. The LifeStraw, a large straw tube which uses layers of filtering, from textile filters, to iodine beads and a carbon filter, allows even the dirtiest water to be consumed safely in remote locations.

References:

express.howstuffworks.com/lifestraw2.htm

The Backpackers Field Manual by Rick Curtis

wikipedia.org/wiki/Purified_water