water treatment

Question 1

1. sedimentation

Answer 1

water allowed to remain stable to let suspended solids settle

Question 2

2. screens

Answer 2

metal grills used to remove floating veg, plastics, paper

Question 3

3. aeration

Answer 3

water sprays or bubbles are used to ensure a high dissolved oxygen content and remove organic matter and metals which cause a bad taste and smell

Question 4

4. flocculation

Answer 4

such as aluminium sulphate are added to neutralise clays particles to make them settle

Question 5

5. filtration

Answer 5

sand filters may be used to remove any suspended bacteria

Question 6

6. activated carbon filters

Answer 6

particles of activated carbon remove organic chemicals like pesticides and those that cause bad tastes

Question 7

7. sterilisation

Answer 7

using chlorine, ozone, UV to kill pathogens

Question 8

8. pH control

Answer 8

pH adjusted using crushed lime

Question 9

9. ion exchange

Answer 9

toxic ions removed using ion exchange resins (polymer beads or particles of zeolite) or to remove calcium and magnesium for softer water

Question 10

10. fluoridation

Answer 10

added to improve dental health

Question 11

11. reverse osmosis

Answer 11

saline water is filtered at a very high pressure through a partially permeable membrane of small polyamide tubes. huge energy needed so its expensive

Question 12

12. distillation

Answer 12

water boiled by heating and reducing pressure. steam that is produced is condensed and collected