☰ Year plan · Science

Water, downstream and the schoolyard

Week 16 · Theme 3 Protecting Our Planet, Unit 3 Our Earth’s Resources: Get Started, Unit Project Preview, Concept 3.1 Hydrosphere and Biosphere Interactions (A) · 3 lessons
1

Water that is used twice

Discovery Education Science P5: Term 2, Unit 3, pp. 1–2
GoalDescribe how used water can be cleaned and used again, and name ways to save water.
New words
wastewater · water that has been used at home, at school or in a factorygreywater · used water from sinks, showers and washing machinesirrigate · to give water to farm fields and crops
Explanation

Every living thing needs water. People use it to drink, cook, wash and play, and farmers use it to grow food. The water we have used is called wastewater. Used water from sinks, showers and washing machines is greywater. It can be filtered and cleaned in a treatment plant and then used again for other jobs, such as watering farm fields and trees. In Egypt, a very large treatment plant cleans water that is then used to irrigate farms. This water is cleaned for fields, not for drinking. Earth’s fresh water is under pressure from pollution, waste and a changing climate, so using water twice helps. We can also save water: turn off the tap while brushing your teeth, mend leaking taps, take quick showers, and never pour waste into rivers or canals.

Worked examples
Where the water came fromGreywater?
showeryes
washing dishesyes
washing machineyes
toiletno
Not all used water is greywater. Water from sinks, showers and washing machines is greywater. Water from the toilet is not.
tap running: about 12 Ltap off: a glass of water
A tap runs about 6 litres of water every minute. If Marwan brushes his teeth for 2 minutes with the tap running, he uses about 6 × 2 = 12 litres. If he turns the tap off while brushing, he uses only a little from a glass.
homestreatment planttrees watered
A farm near a city waters its trees with treated water from the treatment plant instead of using fresh water from the Nile. This leaves more fresh water for people to drink.
Class activity

Water diary (a grown-up helps). For one day, make a tally mark each time you use water: drinking, washing, flushing, cooking, watering plants. Mark the uses that make greywater. Then write two ways your family could save water, and talk about whether bottled water is needed when safe tap water is available.

Practice
1
What is greywater?
2
What can cleaned wastewater be used for in Egypt? Is it for drinking?
3
A tap runs 6 litres each minute. How much water runs in 3 minutes?
4
Name two ways to save water at home.