Ch.2.5

Question 1

In Hong Kong, about 70% of the fresh water we use comes from _________________ ___________. The remaining 20% to 30% comes from _____________ collected in _____________.

Answer 1

Dongjiang water, rainwater, reservoirs.

Question 2

The water from both main sources of water is treated in _________ ___________ __________before it is supplied to the _________.

Answer 2

Water treatment works, public.

Question 3

1. Water (Dongjiang water and rainwater) is first _____________ through screens to remove large objects (eg fish, leaves and rubbish).
2. ______________ is added to the water and mixed in a rapid mixing chamber.
   * This makes the _________ impurities in water stick together
   * The water then passes into a ______________ tank, where insoluble impurities sink
   * The sediment is collected and removed
   
   3. After sedimentation, the water is filtered through layers of sands and gravel in a _____________ tank
      
      • Small and suspended insoluble impurities that remain are thus ______________
   4. _____________ is added to kill microorganisms
   5. ______________ is added to water to eat prevent tooth decay

Answer 3

Filtered, alum, insoluble, sedimentation, filtration, removed, chlorine, fluoride

Question 4

The water treatment process in Hong Kong involves _____________, _____________, adding ___________/ ___________ to kill microorganisms and adding ______________ to prevent tooth decay.

Answer 4

Sedimentation, filtration, chlorine/ ozone, fluoride