SCIENCE

- In Canada, fresh water is pumped from wells, lakes and rivers, or stored in reservoirs.

-In nature water usually contains toxins and impurities.

Water treatment- the process of making water safe for desired uses( drinking/bathing).
-Water is hardly ever pure. Even when it is colourless, odourless and clear, it can still contain toxins.
Toxin- something that is toxic/dangerous

Water Treatment Process
1) Metal screen removes large objects like rocks, garbage, sticks and leaves.
2) Alum is added to make clumps  that stick to waste. Thus the waste (floc) is formed when solids stick to the clumps. This happens in a large tank.
3) In a settling tank, the floc settles to the bottom and the water floats to the top.
4) A sand and charcoal filter removes any remaining waste  solids and floc from the water.  The water is now clear, colourless and odourless.
5) Chlorine and ozone are added to the water to kill micro organisms like bacteria.
6) Treated water is stored in sealed containers.

Water can also be treated by:
-Reverse Osmosis - mechanical pressure forces water through a membrane that acts as a filter trapping everything but water particles. This is usually used with water wells and not with municipal water. 
-Ultraviolet radiation that kills viruses, bacteria and other microorganisms. 
- Adding water softening chemicals removes calcium and magnesium. These chemicals found in rock cause the water to be hard. Hard water is not dangerous but it leaves a deposit on water pipes, kettles and on your hair. 
-Boiling kills disease causing organisms.