- home use
- flushing toilet
- watering plants
- central heating systems
- irrigation in agriculture
- industrial uses
- raw material
Water dissolves most ionic compounds and some (but not most) covalent compounds.
Why must it be treated?
Drinking water must be free from poisonous salts or harmful micro-organisms that cause or carry disease. Water is essential for life all over the world.
Most of our water comes from reservoirs which have been filled from rivers and groundwater. Government agencies keep an eye on the pollution levels of the reservoirs but all the water must still be treated before it can be safely used for drinking.
Industry sometimes requires water that is purer than domestic levels so that machinery is not clogged up.
How is it treated?
You will need to learn this in detail for the exam.
- water is pumped through filters, which removes some of the larger pieces of debris such as twigs, leaves and rubbish
- the water is filtered through sand beds which filter out even smaller particles
- chlorine is added to the water to kill germs
- sulphur dioxide is added to remove the chlorine
- sometimes fluorines are added to improve teeth
- water is pumped out to your homes
Water treatment is expensive. When we waste water, it goes down the drain and must be re-treated before it passes through your tap again. Therefore, when we waste water, we waste money.
Reservoirs only fill up when it rains. In summer, it sometimes goes without raining for a few weeks, which can lead to droughts and water shortages.