C14.2 - Water safe to drink

Question 1

What is water?

Answer 1

Water is a vital and useful resource

Question 2

Water is a vital and useful resource.

What do we use water for?

Answer 2

Water is a vital and useful resource

We use it for agriculture and in industry

Question 3

Water is a vital and useful resource.
We use it for agriculture and in industry.
What is water, as a solvent and as a coolant?

Answer 3

Water is a vital and useful resource
We use it for agriculture and in industry
Water is an important raw material, as a solvent and as a coolant

Question 4

Water is a vital and useful resource.
We use it for agriculture and in industry.
Water is an important raw material, as a solvent and as a coolant.
Other uses of water

Answer 4

Water is a vital and useful resource
We use it for agriculture and in industry
Water is an important raw material, as a solvent and as a coolant
Other uses of water are for washing and cleaning and drinking

Question 5

Potable water

Answer 5

Potable water is water that is fit to drink

Question 6

What is a major issue all over the world?

Answer 6

Providing people with water that is fit to drink (potable water) is a major issue all over the world

Question 7

In countries such as the UK, what does rainwater do?

Answer 7

In countries such as the UK, rainwater falls to the ground, replenishing our supplies of fresh water in rivers and lakes

Question 8

In countries such as the UK, rainwater falls to the ground, replenishing our supplies of fresh water in rivers and lakes.
What does it also do?

Answer 8

In countries such as the UK, rainwater falls to the ground, replenishing our supplies of fresh water in rivers and lakes
It also seeps down through soil and rocks to underground sources of water called aquifers

Question 9

Aquifers

Answer 9

Aquifers are underground sources of water

Question 10

In countries such as the UK, rainwater falls to the ground, replenishing our supplies of fresh water in rivers and lakes.
It also seeps down through soil and rocks to underground sources of water called aquifers.
How can fresh water be obtained from these porous underground seams of rock?

Answer 10

In countries such as the UK, rainwater falls to the ground, replenishing our supplies of fresh water in rivers and lakes
It also seeps down through soil and rocks to underground sources of water called aquifers
Fresh water can be obtained from these porous underground seams of rock by drilling a pipe down to form a water well

Question 11

What does rainwater itself do as it falls to the ground?

Answer 11

Rainwater itself dissolves some gases from the air as it falls to the ground

Question 12

Rainwater itself dissolves some gases from the air as it falls to the ground.
Then, what happens?

Answer 12

Rainwater itself dissolves some gases from the air as it falls to the ground
Then, once in contact with solid land, it will dissolve soluble substances as it passes over them

Question 13

Rainwater itself dissolves some gases from the air as it falls to the ground.
Then, once in contact with solid land, it will dissolve soluble substances as it passes over them.
So what will water from natural sources always contain?

Answer 13

Rainwater itself dissolves some gases from the air as it falls to the ground
Then, once in contact with solid land, it will dissolve soluble substances as it passes over them
So water from natural sources will always contain dissolved minerals (salts), as well as microorganisms from soil and decaying matter

Question 14

Rainwater itself dissolves some gases from the air as it falls to the ground.
Then, once in contact with solid land, it will dissolve soluble substances as it passes over them.
So water from natural sources will always contain dissolved minerals (salts), as well as microorganisms from soil and decaying matter.
What must happen to the levels of both these impurities?

Answer 14

Rainwater itself dissolves some gases from the air as it falls to the ground
Then, once in contact with solid land, it will dissolve soluble substances as it passes over them
So water from natural sources will always contain dissolved minerals (salts), as well as microorganisms from soil and decaying matter
The levels of both these impurities must be reduce to meet strict safety standards for drinking water

Question 15

What do the best sources of fresh water contain?

Answer 15

The best sources of fresh water contain low levels of minerals and microbes to start with

Question 16

Where is about 97% of the water on Earth found?

Answer 16

About 97% of the water on Earth is found in its oceans

Question 17

About 97% of the water on Earth is found in its oceans.

What is this?

Answer 17

About 97% of the water on Earth is found in its oceans

This is not potable water

Question 18

Describe the 1st step of the treatment of water from a reservoir to make potable water

Answer 18

The 1st step of the treatment of water from a reservoir to make potable water:
At the reservoir - As the water enters the water treatment works, it passes through a screen
This is made from bars of metal placed close together
These catch large objects, such as leaves and twigs

Question 19

Describe the 2nd step of the treatment of water from a reservoir to make potable water

Answer 19

The 2nd step of the treatment of water from a reservoir to make potable water:
The settlement tank - sand and soil settle out

Question 20

Describe the 3rd step of the treatment of water from a reservoir to make potable water

Answer 20

The 3rd step of the treatment of water from a reservoir to make potable water:
Aluminium sulfate and lime are added to the water
Small particles of dirt clump together so that they sink to the bottom of the water
The sludge that collects like this is dumped in a landfill site, where it forms mud

Question 21

Describe the 4th step of the treatment of water from a reservoir to make potable water

Answer 21

The 4th step of the treatment of water from a reservoir to make potable water:
The water is passed through a special filter made of fine sand and gravel
This removes any remaining particles of mud or grit, so the water is clean

Question 22

Describe the 5th step of the treatment of water from a reservoir to make potable water

Answer 22

The 5th step of the treatment of water from a reservoir to make potable water:
Although the water now looks clean, it may still contain harmful bacteria
A small amount of chlorine is added to the water to kill any bacteria in the water
Alternatively, ozone can be added or UV light used

Question 23

Describe the 6th step of the treatment of water from a reservoir to make potable water

Answer 23

The 6th step of the treatment of water from a reservoir to make potable water:
The pH of the water is checked and corrected so that it is neutral
It is then stored in large tanks and service reservoirs ready to be pumped to homes, schools, offices, factories, ect

Question 24

When water is taken from rivers or reservoirs, made to store fresh water, what has to happen?

Answer 24

When water is taken from rivers or reservoirs, made to store fresh water, it has to be treated to make it safe to drink

Question 25

When water is taken from rivers or reservoirs, made to store fresh water, it has to be treated to make it safe to drink.
What techniques does this treatment involve?

Answer 25

When water is taken from rivers or reservoirs, made to store fresh water, it has to be treated to make it safe to drink
This treatment involves techniques such as:
1. Passing the untreated water through filter beds made of sand and gravel to remove solid particles
2. The addition of chlorine or ozone to sterilise the water by killing microorganisms or, without adding chemical sterilising agents, by passing ultra-violet light through the water

Question 26

In the UK, what is there sufficient of to satisfy the needs of the population and industry?

Answer 26

In the UK, there is sufficient rain and natural supplies of fresh water to satisfy the needs of the population and industry

Question 27

In the UK, there is sufficient rain and natural supplies of fresh water to satisfy the needs of the population and industry.
However, where can obtaining enough potable water be difficult?

Answer 27

In the UK, there is sufficient rain and natural supplies of fresh water to satisfy the needs of the population and industry
However, in countries with much drier climates and with few sources of natural fresh water, obtaining enough potable water can be difficult

Question 28

In the UK, there is sufficient rain and natural supplies of fresh water to satisfy the needs of the population and industry.
However, in countries with much drier climates and with few sources of natural fresh water, obtaining enough potable water can be difficult.
What do some of these places have to do?

Answer 28

In the UK, there is sufficient rain and natural supplies of fresh water to satisfy the needs of the population and industry
However, in countries with much drier climates and with few sources of natural fresh water, obtaining enough potable water can be difficult
Some of these places have to use sources of water that we would not consider

Question 29

How can water from any source, even seawater or salty water from the marshes, be made pure?

Answer 29

Water from any source, even seawater or salty water from the marshes, can be made pure by distilling it

Question 30

Water from any source, even seawater or salty water from the marshes, can be made pure by distilling it.
However, what is distillation?

Answer 30

Water from any source, even seawater or salty water from the marshes, can be made pure by distilling it
However, distillation is an expensive process

Question 31

Water from any source, even seawater or salty water from the marshes, can be made pure by distilling it.
However, distillation is an expensive process.
Why is this?

Answer 31

Water from any source, even seawater or salty water from the marshes, can be made pure by distilling it
However, distillation is an expensive process
This is because of the energy costs involved in boiling large volumes of water, even though reduced pressure is used in a desalination plant

Question 32

Flash distillation

Answer 32

Flash distillation is the process when water boils below 100 degrees Celsius, under reduced pressure
This saves on some energy costs

Question 33

Desalination

Answer 33

Desalination is converting salty water to potable, usable water

Question 34

Where is desalination used?

Answer 34

Desalination is used in the Middle East in some oil-rich nations and on some islands with no natural sources of water apart from occasional rainwater

Question 35

What process besides distillation can be used to desalinate water?

Answer 35

Besides distillation, a process called reverse osmosis can also be used to desalinate water

Question 36

Besides distillation, a process called reverse osmosis can also be used to desalinate water.
What does reverse osmosis use?

Answer 36

Besides distillation, a process called reverse osmosis can also be used to desalinate water
Reverse osmosis uses membranes to separate the water and the salts dissolved in it

Question 37

Besides distillation, a process called reverse osmosis can also be used to desalinate water.
Reverse osmosis uses membranes to separate the water and the salts dissolved in it.
What can the membranes do?

Answer 37

Besides distillation, a process called reverse osmosis can also be used to desalinate water
Reverse osmosis uses membranes to separate the water and the salts dissolved in it
The membranes can remove 98% of dissolved salts from seawater

Question 38

Besides distillation, a process called reverse osmosis can also be used to desalinate water.
Reverse osmosis uses membranes to separate the water and the salts dissolved in it.
The membranes can remove 98% of dissolved salts from seawater.
What is involved?

Answer 38

Besides distillation, a process called reverse osmosis can also be used to desalinate water
Reverse osmosis uses membranes to separate the water and the salts dissolved in it
The membranes can remove 98% of dissolved salts from seawater
There is no heating involved, so it uses less energy than distillation

Question 39

Besides distillation, a process called reverse osmosis can also be used to desalinate water.
Reverse osmosis uses membranes to separate the water and the salts dissolved in it.
The membranes can remove 98% of dissolved salts from seawater.
There is no heating involved, so it uses less energy than distillation.
However, what is still needed?

Answer 39

Besides distillation, a process called reverse osmosis can also be used to desalinate water
Reverse osmosis uses membranes to separate the water and the salts dissolved in it
The membranes can remove 98% of dissolved salts from seawater
There is no heating involved, so it uses less energy than distillation
However, energy is still needed to pressurise the water passing through and corrosion of pumps by salty water is also a problem