AQA Trilogy Chemistry - C12 The Earth's Resources

Finite Resources

• resources that will run out if we exploit them

• e.g. fossil fuels

Renewable Resources

• can be replaced as we use them

• e.g. biofuels

Potable Water

• water safe to drink

Distilliation

• liquid is heated into a gas and then condensed

• can be an expensive process due to the large amounts of energy required to heat it

Desalination

• converting salty water to potable, useable water by removing dissolved mineral salts from water

Reverse Osmosis

• membranes are used to separate dissolved salts from salty water

• the membranes can remove 98% of dissolved salts from seawater

• no heating required

• energy still required to make the high pressures needed

Sewage Treatment

• screening - large solid objects are removed

• primary treatment - solid sediments settle out from the mixture and the sludge is piped to a storage tank for further treatment

• secondary treatment - useful bacteria feed on an remaining organic matter and harmful microorganisms and break them down aerobically, then the tank is aerated

• final treatment - the useful bacteria settle at the bottom of the tank and removed

Treating Sewage Sludge

• it is digested anaerobically by microorganisms