Waste water and ground water must be treated to make the water potable or sate to drink.
Stages in water treatment
1) Sediimentation- large insolule particles sink to the otton of a tank
2) filtration-small insoluble particles are removed by filtering through beds of sand
3) Chlorination- chlorine gas is bubbled from the water to kill microbes.
Potable drinking water must have:
- low levels of contaminating substances
- low levels of microbes.
Fresh water can come from reservoirs, lakes and rivers. it is likely to contain:
- objects such as leaves and twigs
- insolubes solids such as particles of soil