This week’s question was asked by a niece.

QUESTION: How do water purifiers like Brita or Kangen work?

ANSWER: Water purifiers have two goals. First, purifiers remove bad “bugs” like cryptosporidium and giardia. These bad “bugs” can lead to diarrhea and severe stomach cramps. Secondly, purifiers take out heavy metals such as lead, copper, mercury and cadmium.

People purchase water filtering systems to provide safe and good-tasting water. They also want to save money by not buying bottled water. There are a myriad of water purifiers on the market. We’ll examine two that are available in most department and hardware stores and that use differing methods.

Brita water filters turn regular tap water into filtered drinking water. Brita sells both a “pitcher” and water faucet attachment that uses a porous block of activated carbon as the filtration system. Activated carbon is an all-purpose filtering system in many industrial applications. Eventually the charcoal’s ability to filter is maxed out at around 40 gallons, and the filter must be replaced. If the filter is not replaced periodically, bacteria will grow in the filter. Brita gets rid of chlorine, lead, and mercury. Brita is a big seller.

The Kangen is another popular home unit. Kangen features a large easy-to-read display, has a high output rate, and is self-cleaning. It is a high-end item, and the unit can be quite pricey. Sodium chloride and sodium hypochlorite solutions contribute ions to the water. These chemicals must be added to the unit on a regular basis. The operator can choose water to be slightly acidic or a bit alkaline. The filter contains calcium sulfite. Kangen, like Brita, has cornered a good share of the water purifier market.

Osmosis is a natural process. How does it work? Let’s say we have two different concentrations of salt water separated by a membrane. Salt would be a minor component (solute), and the major component (solvent) would be water. Water will go through the membrane from low salt concentration to high salt concentration. This will continue until the salt concentration is the same on both sides of the membrane.

Reverse osmosis, as the name implies, is just the opposite. It is the process of forcing a solvent (water) from a region of high solute (salt) concentration though a membrane to a region of low solute (salt) concentration. This is done by applying a high pressure against the membrane. Reverse osmosis is another technique to provide clean drinking water for the home. These systems have a longer life and provide large quantities of water in very little time.

Reverse osmosis is a wonderful process, providing tons of fresh drinking water by desalting the sea. Since 1977, Cape Coral, Florida, has been receiving all its drinking water from the salty sea water of the Gulf of Mexico. At one point, the Cuban government cut off water and electricity to the United States Naval Bay at Guantanamo Bay (Gitmo). Now the base gets its water from a desalination plant.

Astronauts on the lunar landing missions used carbon or charcoal filters to drink water coming from the fuel cells that produced electricity. Water coming from the fuel cells was so pure it did not have any taste. It is a good balance of minerals that gives water its taste. The astronauts preferred Tang orange juice instead of the spacecraft’s water.

How much water should you drink? When I was a kid, the saying was eight glasses per day. Many health experts agree that we should be drinking enough water to keep ourselves properly hydrated, which means that your urine should be relatively clear and plentiful.

What does WebMD say? “All liquids help you stay hydrated. Water is usually the best choice, because it’s free (if you’re drinking tap water) and has no sugar or calories. But most healthy people can get enough fluid through the beverages they consume every day. These can include water, fruit juices, coffee, sodas, iced tea and other drinks.”

Mayo Clinic: “How much water should you drink each day? It’s a simple question with no easy answer. Studies have produced varying recommendations over the years, but in truth, your water needs depend on many factors, including your health, how active you are and where you live. Everyone has heard the advice, ‘Drink eight eight-ounce glasses of water a day.’ That’s two quarts or half a gallon, which isn’t that different from the Institute of Medicine recommendations. Although the ‘eight-by-eight’ rule isn’t supported by hard evidence, it remains popular because it’s easy to remember. Just keep in mind that the rule should be re-framed as: ‘Drink eight 8-ounce glasses of fluids a day,” because all fluids count toward the daily total.’”

In the United States, water delivered by public water supplies is regulated by the Environmental Protection Agency. Bottled water is regulated by the Food and Drug Administration. These two agencies have different standards for the water that they regulate. In general, EPA’s quality standards are higher because it is sent out to a much larger number of people. However, FDA does have strict standards of purity and labeling that must be met by all manufacturers of bottled water.

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Larry Scheckel is a retired Tomah High School physics teacher.