Day 5 – Water Purification

• Water purification is important for providing clean, drinkable water for communities.• There are many different things to consider when

purifying water.

Distillation

• Distillation relies on the idea that when you boil water you leave behind any dissolved solids. This removes inorganic pollutants.• It does NOT work for things like gasoline or

pesticides, which also boil with the water.

Filtration

• You can filter water with something like sand or charcoal, which removes many fine particles including organics.• This is similar to the way the ground filters water

going into wells.

Disinfection

• Bacteria and viruses are small. So small they can make it through filters.• The easiest way to disinfect water is to boil it for

ten minutes.• Iodide tablets (KI) will also kill all bacteria, and

99.3% of viruses.

Precipitation

• You can use precipitation to remove metal ions that you know are in your water.• The issue with this is that you need to replace any

ion with another one.• This can be solved by using ions we consume every

day like sodium or potassium carbonate.• You just need to filter out the precipitate once you

make it.

pH

• The pH of water is important to animals and plants.• Normal water has a pH of 7 (neutral).• Acids have a lower pH (0-6) and can be corrosive to

metals and many other substances.• Bases have a higher pH (8-14) and are called

alkaline or caustic.

pH

• Adding an acid to a base (or vice versa) results in neutralization.• The H+ from the acid reacts with the OH- from the

base to make water.• We can use indicators or pH paper to determine the

pH of water.

NaOH + HCl H2O + NaCl