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What are the stages of life cycle assesments?
extracting and processing the raw materials
manufacturing and packaging
use
disposal
What are the disadvantages of lifecycle assesments?
we can measure the use of water and energy and production of waste products
we can’t be certain how damaging they are to the environment
so you have to make estimates
What’s potable water
Water that is safe to drink
What are the water sources for fresh water?
aquifers
lakes
rivers
reservoirs
The steps to treat water
Find source of water
pass fresh water through filter beds to remove leaves and suspended particles
sterilised by chlorine, ozone or ultraviolet light
What is desalination?
reduces levels of dissolved minerals down to an acceptable level for potable water
What are the 2 ways of desalination?
distillation and reverse osmosis
however they require lots of energy making them expensive
What are the steps to sewage treatment?
screened passing through a mesh removing solids and grit
sewage settles in sedimentation tanks producing liquid effluent and sludge which sinks
sludge is digested by anaerobic bacteria
bacteria produce biogas which can be burned for electricity
digested sludge can be used as fertilisers
How can organic microorganims and organic molecules be reduced in liquid effluent?
air is bubbled through liquid so aerobic bacteria multilply
so aerobic bacteria digest organic molecules and harmful microorganisms
can be then discharged into rivers or the sea
What are the steps in phytomining?
plants are grown on land containing metal compounds needed
plants absorb metal compound and concentrate it in thier tissue
plants are harvested and burned
the ash contains a high concentration of the metal compound
extraction of metal from the compound
What are the steps in bioleaching?
uses bacteria
bacteria produces leachate
leachate contains metal compound
extraction of the metal from the compound