using resources Flashcards
what are the two types of desalination
reverse osmosis and distillation
what is the difference between potable water and pure water
potable water is drinking water, contains minerals and ions,
pure water= no ions just h20
list criteria for potable water
ph between 6.5-8.5
no micro organisms
levels of dissolved substances need to be low
list examples of surface water
lakes
reservoirs
rivers
treating fresh water,
what are the three steps
passed through wire mesh
through bed of sand and gravel
sterilised to kill micro organisms
why is freshwater passed through wire mesh
to filter out bigger objects ie twigs
why is freshwater passed through sand and gravel bed
because that filters out smaller bits
what are the three ways to kill micro organisms in fresh water
bubbling it through chlorine gas
exposing it to ozone
exposing it to ultra violet light
define desalination
removing salt from seawater
pros and cons of reverse osmosis
pros
quicker
cons
expensive-high water pressure requires to pass through
pumps can be corroded due to salty water
how does reverse osmosis work
water is passed through permeable membrane, only water molecules allowed through, larger molecules get trapped
sources of waste water
domestic (shows/toilet)
agricultural system
industrial (factories)
how sewage treatment works
screening and grit removal
sedimentation to produce sewage sludge/effluent
biological breakdown of microorganisms
how is the effluent broken down
biological breakdown of micro organisms, effluent is under aerobic conditions, air is pumped into the tank supplying it with oxygen. the microbes in the effluent tank can break down the organic matter by aerobic digestion
how is sludge broken down
biological breakdown of microorganisms by aerobic digestion, tank is kept sealed so no air gets in. this process produces methane which can be burned as an energy source
