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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
Note 
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