Potable water and who has it Cambridge IGCSE Environmental Management revision
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In plain words
Water straight from a river can carry twigs, mud and bacteria that kill. Four steps turn it into water you can drink without a second thought. Whether those steps reach your tap depends a great deal on where in the world you were born.
8 things to know
- Potable water is water that is safe to drink.
- Screening: the water passes through metal screens that trap large objects, such as leaves, twigs and litter.
- Sedimentation: the water is held still in a tank, so that small solid particles sink to the bottom.
- Filtration: the water passes through beds of sand and gravel, which trap the fine particles that remain.
- Chlorination: chlorine is added to kill bacteria and other microorganisms that cause disease.
- Water-rich regions have more than enough rain, rivers or ground water for their people. Water-poor regions do not, because rainfall is low or the population is large.
- Urban and rural regions differ. Cities usually have treated, piped water, because many people share the cost. In rural areas people may depend on wells and rivers, and may walk a long way to fetch water.
- There are global inequalities. In wealthy countries almost everyone has potable water, and sewage is treated. In poorer countries many people have neither, and untreated sewage reaches the water that people drink.
Worked example
River water is cloudy with fine mud and contains harmful bacteria. Explain which stages of treatment deal with each problem.
- Sedimentation lets most of the mud settle to the bottom of the tank.
- Filtration through sand and gravel removes the fine particles still in the water.
- Chlorination kills the bacteria. Clear water is not safe until this is done.
Tips and tricks
- Learn the four stages in order: screening, sedimentation, filtration, chlorination. Filtration does not remove bacteria. Chlorination kills them.
- Potable does not mean pure. Potable water still has harmless dissolved substances in it. It means safe to drink.
It lands in your notebook with its questions as flashcards.
Potable water and who has it: 6 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
What is potable water?
Safe, not pure.
Which stage removes leaves and litter?
Screens catch the large objects first.
What happens in sedimentation?
Still water lets the particles settle.
Why is chlorine added?
Bacteria in water cause diseases such as cholera.
What is the water passed through during filtration?
The gaps between the grains trap fine particles.
A village in a water-rich region still has no potable water. What is the most likely reason?Stretch
Having water and having safe water are different things.
Quiz
6 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
3 questions, 8 marks. Write your answers on paper, then check them.
Potable water and who has it
Cambridge IGCSE Environmental Management 0680 · 8 marks · papermunch.org
Name ______________________________ Date ______________
Define the term potable water.[1]
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Water that is safe to drink.
State the four stages of water treatment, in order.[4]
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Screening, sedimentation, filtration, chlorination.
Suggest why people in rural areas of poorer countries often have less access to potable water than people in cities.[3]
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Any three: homes are spread out, so piped water costs more for each person; there is less money for treatment works; people rely on wells and rivers that may be polluted; sewage is often not treated, so it contaminates the water.
Answers: Potable water and who has it
- 1. Water that is safe to drink.
- 2. Screening, sedimentation, filtration, chlorination.
- 3. Any three: homes are spread out, so piped water costs more for each person; there is less money for treatment works; people rely on wells and rivers that may be polluted; sewage is often not treated, so it contaminates the water.