MS. BOZZI-GRADE 8



Obtaining Water Quality (See Student Book pages 317–323)

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Factors Affecting Water Quality

The number of people using Earth’s fresh water is growing. That is why it is very important to have a steady supply of clean water. We also need to be aware that harmful substances may enter or be dumped into our water.

Factories that dump harmful chemicals into rivers can affect our water and our health. When it rains, garden chemicals could enter our water sources through groundwater run-off. If a sewage pipe breaks, sewage could flow into a water source. Animal

waste in a stream will affect the water quality downstream. If someone pours paint thinner down a drain, it enters the water system. Substances such as these are water contaminants. Contaminants are things that can harm humans, other animals, or the environment.

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There are three main types of contaminants:

• Biological contaminants include live organisms (those you can see, such as zebra mussels, and those you can’t see, such as bacteria and viruses)

• Chemical contaminants include dissolved substances (such as pesticides and minerals)

• Physical contaminants include materials that do not dissolve in water (such as garbage)

To protect ourselves, it is important that we treat and test our drinking water to make sure it is safe.

List three harmful things that might enter or be dumped into our water.

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Generally, fresh water needs to be treated before we can use it for drinking. Underground water and aboveground sources, like streams, rivers, and lakes, often contain harmful substances and organisms. Chemicals and particles from the air fall into our sources of water. If left untreated, these substances and organisms can make people sick or even kill them.

Circle the items in the illustration below that you think would harm the drinking water.

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Treating Groundwater Sources

Many Canadians get their water from a well. The water taken from wells is usually filtered to remove any contaminants. Some people also have the water tested by sending it to a laboratory.

Treating Above Ground Water Sources

Boiling water is one way to clean water before you drink it. Boiling will kill any harmful microorganisms in the water. However, it will not remove any chemicals

in the water. Water from wells and aboveground water sources can contain harmful chemicals that leak into the water supply from substances such as farm pesticides

and factory pollutants.

[pic] Boiling the water will help to clean it.

Why might it be safer to drink a cup of tea than a glass of drink crystals dissolved

in water?

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Water treatment can be very expensive. How much the water needs to be treated depends on how polluted it is. The cost of treatment is another reason to keep our water supply clean.

The Water Treatment Plant

Most Canadian communities rely on a water treatment plant to clean their water. Not all cities use the same methods to clean the water. However, there are some basic stages that water will go through from the moment it leaves the lake and enters the water treatment plant until the time it reaches your home.

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There are five basic states in the water treatment process.

Testing Water Quality

As water makes its way through the water treatment plant, the quality of the water is checked and tested by computers and specially trained workers to make sure it is safe to use and drink. Scientists in labs also test water samples taken from schools and hospitals to ensure that it is clean and safe.

Summarize what you have learned about water treatment and testing in the 3-2-1 organizer below.

3 Things done to our water in the water treatment plant:

2 Ways water quality is tested:

1 Question I have:

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While water looks clean and clear, it can contain unseen contaminants that are very harmful to humans.

Teaching Note: It is not safe to drink from country streams or to eat fresh snow or icicles. These can all contain chemicals that are in the atmosphere.

Key Term

contaminants: contents that can harm humans, animals, or the environment

Teaching Note: Scientists keep track of Earth’s population and its demand for resources. From 1950 to the end of the century, the world’s population grew from 2.5 billion to almost 6 billion.

11.2

Harmful substances in drinking water can make people very ill.

When it rains, chemicals sprayed on lawns drain into our water systems.

When it rains, chemicals sprayed on lawns drain into our water systems.

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