Before you take a gulp of water, try to mentally trace where that water that just gushed out of your taps has been: How did it go from that weird-tasting raindrop to the clear, odorless water that is sitting in your glass now?
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Safe drinking water is a privilege Americans often take for granted — until a health crisis like the one in Flint, Mich., happens that makes us think about where it comes from and how we get it.
Our drinking water comes from lakes, rivers and groundwater. For most Americans, the water then flows from intake points to a treatment plant, a storage tank, and then to our houses through various pipe systems.
The most common steps in water treatment used by nearly every utility company:
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A typical water treatment process. Annette Elizabeth Allen for NPR hide captiontoggle captionAnnette Elizabeth Allen for NPR
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(Top) Older pipes can be treated with a chemical to prevent corrosion and contamination of the water supply. (Bottom) When Flint, Mich., changed its water source, it didn't treat the water to prevent corrosion of the pipes, which contributed to high lead levels in the water. Annette Elizabeth Allen for NPR hide captiontoggle captionAnnette Elizabeth Allen for NPR
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In farming communities across the country, water can be contaminated by fertilizer and livestock. Annette Elizabeth Allen for NPR hide captiontoggle captionAnnette Elizabeth Allen for NPR
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There are two methods plants may use for desalination. One, used by Carlsbad, is called reverse osmosis; it forces water through semipermeable membranes under very high pressure.
The other is a thermal process that heats the water to form water vapor, which is then condensed and collected as freshwater, leaving the salt behind.
Waterborne Diseases Can Happen Anywhere
According to the Centers for Disease Control and Prevention, there were 32 cases of drinking-water associated outbreaks from 2011 to 2012, the most recent time period for which they have been reported.
Most of it was Legionellosis, a disease typically spread by water droplets in the air. The remaining cases were associated with bacteria and viruses that can be killed by chlorine. To prevent such outbreaks, CDC emphasized the importance of ensuring a sufficient level of disinfectant, such as chlorine, is present in the water from the time it leaves the treatment center to when it arrives in our pipes.
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Some utilities use ozone as a disinfectant to kill bacteria and viruses, a method some say is more effective than the usual route of using chlorine. Ozone is bubbled into the water in huge tanks, destroying illness-causing microorganisms. It also gets rid of taste and odor in the water.
Milwaukee, Wis., started using ozonation after an outbreak of Cryptosporidium in 1993 killed 69 people and sickened up to 403,000 residents. It was one of the largest outbreaks caused by a contaminated public water source, according to the CDC.
Some States Try To Protect Their Water At The Source
Watersheds are the areas where rivers, lakes and ponds drain into, and they're a source of drinking water. Some cities, such as Seattle and New York, are famous for the regulations and programs they put in place to protect their watersheds.
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New York City gets its water from multiple watersheds that are well-protected. The quality of the water is so good that it does not need to undergo filtration at the treatment plants. Frank Whitney/Photographer's Choice/Getty Images hide captiontoggle captionFrank Whitney/Photographer's Choice/Getty Images
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Although the water doesn't go through filtration, it is still disinfected with chlorine and ultraviolet light, with the usual sludge of chemicals added to control pH and prevent corrosion.
The EPA regulates approximately 155,000 public water systems in the country, requiring utilities to conduct tests according to schedule and submit water quality data. On the other hand, over 15 million Americans rely on private wells — water quality from this source is not regulated by the EPA, but might be under state rules.
From the lake to the tap, water goes through many steps to become safe for us to drink. It is a crucial process that requires constant monitoring, and — as both history and current events show — it's one that can be easily threatened by bacterial outbreaks, natural disasters and human activity.
How do they make water safe to drink?
After filtering, add a disinfectant such as iodine, chlorine, or chlorine dioxide to the filtered water to kill any viruses and remaining bacteria.
How is water made safe for drinking Class 4?
Boiling water kills the germs present in the water. So, water can be made safe for drinking by boiling.
How can you tell if water is safe to drink?
HOW TO CHECK FOR YOUR DRINKING WATER'S SAFETY: 7 EASY AND QUICK WAYS.
CHECK WATER FOR ANY SIGNS OF CLOUDINESS. ... .
WASH WITH SOAP AND WATER AND CHECK FOR A SLIMY TEXTURE. ... .
CHECK FOR THE WATER'S COLOR. ... .
CHECK FOR ANY UNUSUAL OR STRONG SMELL. ... .
CHECK WITH YOUR WATER COMPANY. ... .
USE THE EPA'S DRINKING WATER WATCH PROGRAM..
Could we drink water straight from the ground?
Never drink water from a natural source that you haven't purified, even if the water looks clean. Water in a stream, river or lake may look clean, but it can still be filled with bacteria, viruses, and parasites that can result in waterborne diseases, such as cryptosporidiosis or giardiasis.