A field centre obtains fresh water from a river. The untreated water contains suspended, insoluble soil particles and harmful microbes. The water passes through filter beds and is then sterilised using ultraviolet light.
After maintenance, one of the two treatment stages fails.
| Test | Before treatment | After treatment |
|---|---|---|
| Suspended insoluble particles | Present | Present |
| Harmful microbes | Above the safe level | Below the safe level |
Explain which treatment stage has failed and explain the effect of omitting the other treatment stage.
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.