DNA chain made up of water
Water Knowledge

Water Knowledge 101

What is water?


  • Water is a necessity. No living thing can survive without water.
  • Up to 70% of the human body is made up of water.
  • Most of the tap water is contaminated.
  • Despite going through municipal water treatment plants, tap water contains many contaminants and impurities.
  • Water authorities also need to add some harmful substances (like chlorine and aluminium sulphide) for disinfection purpose).
  • Although it poses no immediate threat to life, it is hazardous to health in the long run.

Water Source in HK

18 reservoirs in HK + Dongjiang water
from Quangdong province

Water Treatment

Dosing with chemicals
Addition of hydrated lime to control pH
Use of chlorine for disinfection
Addition of fluoride for dental protection
Drinking Water

3 Main Contaminants in Tap Water

3 Main Contaminants in Tap Water

Contaminants insoluble in water

  • asbestos, arsenic, heavy metals (aluminium, cobalt, chromium, moscovium, mercury, lead, cadmium, manganese, silver), rust, sand

Biological Contaminants

  • escherichia coli, cystomycetes, plankton

Chemical Contaminants

  • Soluble solids:
    Chloride, Sulfate
  • Volatile Organic Compounds:
    chlorine, ammonium chloride, chloroform, chlorinated hydrocarbon, trihalomethanes, pesticides, carbon tetrachloride, trichloroethylene, xylene

How can we stay healthy if we take in these contaminants every day?

pH Value of Water

pH Value of Water
  • pH is a measure of how acidic/basic water is
  • The range goes from 0 to 14, with 7 being neutral. pHs of less than 7 indicate acidity, whereas a pH of greater than 7 indicates a base
  • pH is really a measure of the relative amount of free hydrogen and hydroxyl ions in the water. Water that has more free hydrogen ions is acidic, whereas water that has more free hydroxyl ions is basic
  • Excessively high and low pHs can be detrimental for the use of water
  • High pH causes a bitter taste, water pipes and water-using appliances become encrusted with deposits, and it depresses the effectiveness of the disinfection of chlorine, thereby causing the need for additional chlorine when pH is high
  • Low-pH water will corrode or dissolve metals and other substances

Water Hardness

Water Hardness
  • The simple definition of water hardness is the amount of dissolved calcium and magnesium in the water
  • Hard water is high in dissolved minerals, largely calcium and magnesium
  • Depending on the hardness of your water, after using soap to wash you may have felt like there was a film of residue left on your hands
  • In hard water, soap reacts with the calcium (which is relatively high in hard water) to form “soap scum”
  • When using hard water, more soap or detergent is needed to get things clean, be it your hands, hair, or your laundry