2.3 and 2.4 Water Treatment/Water Issues

Question 1

Name the order of processes the of water treatment

Answer 1

• sedimentation
• filtration
• disinfection

Question 2

What can be used to improve the taste of water?

Answer 2

Water filters

Question 3

Why is disinfection important?

Answer 3

It kills microbes in the water

Question 4

What is often used to kill microbes in drinking water?

Answer 4

Chlorine

Question 5

What 2 things do water filters usually contain?

Answer 5

• carbon

* an ion exchange resin

Question 6

Why is the ion exchange resin important in water filters?

Answer 6

Removes some soluble substances and silver or another substance to prevent the growth of bacteria

Question 7

How can pure water be made?

Answer 7

Distillation

Question 8

Explain why distillation is not used to treat mains tap water

Answer 8

It requires a large amount of energy to boil the water so would be very expensive to do on a large scale

Question 9

What must drinking water not contain to be classified as drinking water?

Answer 9

Doesn’t have to be pure but must not contain anything that will harm us

Question 10

What does sedimentation do for water treatment?

Answer 10

Removes insoluble particles, like twigs and leaves

Question 11

What does filtration do in water treatment?

Answer 11

Removes smaller particles, like mud and dirt

Question 12

What does chlorination/disinfection do in the water process?

Answer 12

Adds chlorine to kill bacteria so it is safe for humans

Question 13

Why do we use distiller water in experiments?

Answer 13

So there are no other ions to interfere with the experiment

Question 14

Name 2 alternatives for chlorination

Answer 14

• use uv lights

* use ozone instead

Question 15

Why do some people dislike the idea of chlorination?

Answer 15

It is a risk to their health as too much chlorine is poisonous

Question 16

What can we buy to remove chlorine before it leaves the tap?

Answer 16

Filters that absorb the chlorine

Question 17

Name 5 advantages to fluoridation of the water supply

Answer 17

• no harmful effects except fluorosis
• 30% reduction in cavities in teeth
• helps protect teeth of people with bad dental hygiene
• bacteria for tooth decay causes heart disease so fluorine prevents that too
• only added in tiny amounts

Question 18

Name 5 disadvantages of fluoridation of the water supply

Answer 18

• causes fluorosis (white porous streaks on teeth) which is reflected in your bones
• no significant benefit so why take risks
• ethically wrong to give people treatments they haven’t consented to
• excess fluorine affects brain and causes learning difficulties and Alzheimer’s
• can’t control people’s intakes

Question 19

What should drinking water contain low levels of?

Answer 19

Dissolved salts and microbes