1
Q
explain the changes in the earth’s early atmosphere to form the earth today (6)
A
- volcanic activity released water vapour
- water vapour condensed to form oceans
- carbon dioxide dissolved in oceans decreasing carbon dioxide
- carbonated produce sediments
- carbon locked up in sedimentary rock
- algae and plants evolve
- absorb carbon dioxide by photosynthesis
- also releases oxygen
- carbon locked up in fossil fuels
2
Q
describe how sewage is treated to remove organic matter (4)
A
- screening/ grit removal (filter to remove large solids)
- sedimentation to produce sewage sludge and effluent
- anaerobic digestion of sludge
- aerobic biological treatment of effluent
