A coastal holiday resort produces potable water from a lake and from sea water. The table shows the treatment processes and the energy needed.
| Water source and process | Treatment | Energy needed (kWh per m3\mathrm{m^{3}}m3) |
|---|---|---|
| Lake water | screening, sedimentation, filtration, chlorination | 0.5 |
| Sea water, existing process | filtration, reverse osmosis | 4.0 |
| Sea water, alternative process | distillation | 18.0 |
During the dry season, the resort produces 500 m3500\ \mathrm{m^{3}}500 m3 of potable water from the lake and 300 m3300\ \mathrm{m^{3}}300 m3 from sea water each day. The volume produced from each source would stay the same if the alternative sea-water process were used.
Statement 1: Replacing chlorination with a second filtration stage would remove the sterilisation stage from the lake-water treatment.
Statement 2: Sea-water treatment uses at least 85% of the total energy used to treat water each day.
Statement 3: Changing the sea-water process from reverse osmosis to distillation would reduce the resort's daily energy use.
Which statements are correct?
Statements 1 and 3 only
Statements 1 and 2 only
Statement 1 only
Statement 2 only
109 exam-style questions on OCR GCSE Chemistry 6.3 Interpreting and interacting with earth systems, covering 6.3.1 Formation and evolution of the atmosphere, 6.3.2 The greenhouse effect and climate change, 6.3.3 Sources and problems of atmospheric pollutants, and 6.3.4 Producing potable water. Each one has a worked solution and a mark scheme showing where the marks go.