A field centre has access to four sources of water. Samples from each source were tested.
The field centre needs to produce potable water from one of these sources. It wants to minimise treatment demand and energy use.
| Source | Dissolved salts in g/dm3\text{g/dm}^3g/dm3 | Suspended solids in mg/dm3\text{mg/dm}^3mg/dm3 | Organic matter in mg/dm3\text{mg/dm}^3mg/dm3 | Harmful microbial colonies in 1 cm3 |
|---|---|---|---|---|
| P: upland lake | 0.08 | 12 | 3 | 40 |
| Q: river downstream from a settlement | 0.15 | 95 | 28 | 800 |
| R: household waste water | 0.50 | 140 | 65 | 2400 |
| S: coastal sea water | 35.00 | 6 | 2 | 25 |
Which source should the field centre select?
Use the data to explain why this is the most suitable source, why the other sources have greater treatment demands and how the selected water should be treated.
87 exam-style questions on AQA GCSE Chemistry 10.1 Using the Earth's resources and obtaining potable water, covering 10.1.1 Using the Earth's resources and sustainable development, 10.1.2 Potable water, 10.1.3 Waste water treatment, and 10.1.4 Alternative methods of extracting metals. Each one has a worked solution and a mark scheme showing where the marks go.