10. Using resources (potable water, waste water treatments)

Question 1

What are the three criteria for water to be considered potable?

Answer 1

• levels of dissolved substances (eg. salts) must be fairly low
• the pH must be between 6.5 and 8.5
• There must be no microorganisms

Question 2

What is potable water?

Answer 2

water that is safe to drink

Question 3

Where does the UK get most of its potable water from?

Answer 3

fresh water sources (rainwater)

Question 4

Why is potable water not pure water?

Answer 4

because potable water contains dissolved substances

Question 5

What are usually 3 sources of fresh water?

Answer 5

• aquifers
• rivers
• lakes

Question 6

What is surface water?

Answer 6

Water that is exposed to the air, it includes rivers, lakes and reservoirs

Question 7

What is ground water?

Answer 7

Water that is found under the ground, such as in aquifers

Question 8

What are the benefits of relying on fresh water?

Answer 8

• it is easy to access
• it is replaced frequently

Question 9

What are the 3 stages of treating fresh water?

Answer 9

1. First, pass the water through wire mesh. This will filter out any large objects like leaves
2. Secondly, pass the water through a bed of sand and gravel. This will filter out smaller things, like bits of rocks
3. Lastly, sterilise the water to kill any microorganisms

Question 10

What are the 3 ways to sterilise water by killing microorganisms?

Answer 10

• bubbling chlorine gas through the water
• exposing it to ozone
• exposing it to ultraviolet radiation

Question 11

What is desalination?

Answer 11

the extraction of potable water from sea water

Question 12

What are the two main techniques that can be used in the desalination of water?

Answer 12

• simple distillation
• reverse osmosis

Question 13

What is a drawback of using desalination to get potable water?

Answer 13

it requires a lot of energy, so is very expensive and it contributes to global warming

Question 14

True or false. Waste water treatment is easier than desalination?

Answer 14

true

Question 15

What are the different sources of waste water?

Answer 15

• domestic
• agricultural
• industrial

Question 16

What do sewage and agricultural waste water require the removal of?

Answer 16

organic matter and harmful microbes

Question 17

What do industrial waste water require the removal of?

Answer 17

organic matter and harmful chemicals

Question 18

What are the steps in the treatment of sewage?

Answer 18

1. Screening - the sewage is passed through gratings and meshes to remove anything large
2. Sedimentation - the sewage is left to sit in a settlement tank so that the heavier particles settle at the bottom as sludge, while the lighter particles settle at the top as effluent
3. Aerobic digestion - air is pumped through the effluent to supply the bacteria with oxygen
4. Anaerobic digestion - the sludge is sealed in a container to prevent the entry of air, which ensures anaerobic respiration

Question 19

What does the anaerobic respiration of sludge produce?

Answer 19

methane

Question 20

True or false. Anaerobic digestion of sludge results in fertiliser that can be spread on fields?

Answer 20

true, as it is nutrient-rich