0:00:08.064,0:00:10.611
Take a look at the water in this glass.

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Refreshing, hydrating, and invaluable[br]to your survival.

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Before you take a sip, though,

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how do you know that the water inside[br]is free from disease-causing organisms

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and pollutants?

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One out of ten people in the world[br]can't actually be sure

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that their water is clean [br]and safe to drink.

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Why is that?

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Inadequate sanitation,

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poor protection of drinking water sources,

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and improper hygiene

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often lead to sewage [br]and feces-contaminated water.

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That's the ideal breeding ground[br]for dangerous bacteria,

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viruses,

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and parasites.

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And the effects of these pathogens[br]are staggering.

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Diarrheal disease from unsafe water is one[br]of the leading causes of death

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around the world for children under five.

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And according to a U.N. report from 2010,

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microbial water-borne illnesses killed[br]more people per year than war.

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Proper treatment processes, though,[br]can address these threats.

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They usually have three parts:

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sedimentation,

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filtration,

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and disinfection.

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Once water has been collected[br]in a treatment facility,

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it's ready for cleaning.

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The first step, sedimentation,[br]just takes time.

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The water sits undisturbed, allowing[br]heavier particles to sink to the bottom.

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Often, though, particles [br]are just too small

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to be removed by sedimentation alone

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and need to be filtered.

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Gravity pulls the water downward through[br]layers of sand

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that catch leftover particles [br]in their pores,

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prepping the water [br]for its final treatment,

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a dose of disinfectant.

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Chemicals, primarily forms [br]of chlorine and ozone,

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are mixed in to kill off any pathogens

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and to disinfect pipes [br]and storage systems.

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Chlorine is highly effective in destroying[br]water's living organisms,

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but its use remains government-regulated

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because it has potentially harmful[br]chemical byproducts.

0:02:04.801,0:02:09.040
And if an imbalance of chlorine occurs[br]during the disinfection process,

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it can trigger other chemical reactions.

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For example, [br]levels of chlorine byproducts,

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like trihalomethanes, could skyrocket,[br]leading to pipe corrosion

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and the release of iron, copper,[br]and lead into drinking water.

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Water contamination from these[br]and other sources

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including leaching,

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chemical spills,

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and runoffs,

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has been linked [br]to long-term health effects,

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like cancer,

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cardiovascular and neurological diseases,

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and miscarriage.

0:02:39.493,0:02:41.704
Unfortunately, analyzing the exact risks

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of chemically contaminated [br]water is difficult.

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So while it's clear that disinfectants[br]make us safer

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by removing disease-causing pathogens,

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experts have yet [br]to determine the full scope

0:02:52.234,0:02:55.035
of how the chemical cocktail [br]in our drinking water

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really impacts human health.

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So how can you tell whether the water[br]you have access to,

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whether from a tap or otherwise,

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is drinkable?

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Firstly, too much turbidity,

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trace organic compounds,

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or high-density heavy metals like arsenic,[br]chromium, or lead,

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mean that the water [br]is unsuitable for consumption.

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A lot of contaminants, [br]like lead or arsenic,

0:03:19.805,0:03:21.867
won't be obvious without tests,

0:03:21.867,0:03:23.805
but some clues, like cloudiness,

0:03:23.805,0:03:25.816
brown or yellow coloration,

0:03:25.816,0:03:27.073
a foul odor,

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or an excessive chlorine smell

0:03:29.687,0:03:32.518
can indicate the need [br]to investigate further.

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Water testing kits can go a step further

0:03:34.666,0:03:39.887
and confirm the presence of many different[br]contaminants and chemicals.

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With many types of contamination,

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there are ways of treating water where [br]it's used instead of close to its source.

0:03:45.941,0:03:50.127
Point-of-use treatment has actually[br]been around for thousands of years.

0:03:50.127,0:03:55.598
Ancient Egyptians boiled away many[br]organic contaminants with the sun's heat.

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And in Ancient Greece, Hippocrates[br]designed a bag

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that trapped bad tasting [br]sediments from water.

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Today, point-of-use processes usually[br]involve ionization

0:04:05.857,0:04:07.579
to lower mineral content.

0:04:07.579,0:04:10.389
They also use adsorption filtration,

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where a porous material[br]called activated carbon

0:04:13.347,0:04:17.870
strains the water to remove contaminants[br]and chemical byproducts.

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While it's not always an effective[br]long-term solution,

0:04:20.819,0:04:25.499
point-of-use treatment is portable,[br]easy to install, and adaptable.

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And in regions where large-scale[br]systems are unavailable,

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or where water has been contaminated[br]further along its journey,

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these systems can mean the difference[br]between life and death.

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Clean water remains a precious[br]and often scarce commodity.

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There are nearly 800 million of us who[br]still don't have regular access to it.

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The good news is that continued[br]developments in water treatment,

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both on a large and small scale,

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can alleviate a lot of unsafe conditions.

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Implementing proper systems where[br]they're needed

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and paying careful attention[br]to the ones already in place

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will fulfill one of the most basic[br]of our human needs.