| what can the sludge be used for | fertilisers in farming |
| NA | NA |
| what is potable water | water that is safe to drink |
| what is the difference between potable and pure water | pure water contains no dissolved substances like salt whilst potable water contains very little amounts of dissolved substances |
| what are the steps to achieving potable water using a clean water source like a river | -collect the water
-pass the water through filter beds to remove any leaves and suspended particles
-sterilise the water to kill microbes |
| what potential things could we use to sterilise water with | chlorine, UV, ozone |
| what process does sea water have to go through in order to be potable | desalination |
| what does desalination do | reduces levels of dissolved minerals down to an acceptable level for potable water |
| in what ways can desalination be carried out | distillation, reverse osmosis |
| what is the disadvantage of these processes | they require a large amount of energy and therefore makes them very expensive |
| go through the process of treating waste water | -sewage is screened by passing thru a mesh removing solids and grit
-sewage is allowed to settle in large sedimentation tanks which produces a liquid effluent and a sludge that sinks to the bottom
-the sludge gets digested by anaerobic bacteria
-the liquid effluent contains a large amount of organic materials and harmful microorganisms so air is bubbled thru it to allow aerobic bacteria to multiply and digest the harmful matter |
| how can anaerobic digestion of the sludge be a good source of electricity | biogas is produced which can be burnt for electricity |
| what can the sludge be used for | fertilisers in farming |
