中文（繁體）
中文（简体）
English
Primary General Studies: Water Treatment and Public Health (Paper 4 (error clinic))
Primary General Studies: Water Treatment and Public Health (Paper 4 (error clinic))
This paper repeats the concepts and calculations that go wrong most often, focusing on disinfection, cross contamination and saving figures.
Direct answers Check units and rounding first, then compare with the note; if a question fails twice, reread that section.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 20 |
| Difficulty mix | Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1 |
| Chapter | Chapter: Primary General Studies: Water Treatment and Public Health |
| Level | P5 |
02 Questions (10 items)
- FoundationCan water collected in a reservoir be drunk straight away?
- FoundationWhat does the sand filter do in the treatment train?
- FoundationHow does boiling differ from chlorination?
- IntermediateAt least how long should hands be rubbed when washing?
- IntermediateWhich diseases can spread through contaminated water?
- IntermediateAfter a supply cut, why let the tap run before using the water?
- ChallengeA works handles 500,000 cubic metres a day. How much in one week?
- ChallengeDaily use per person falls from 130 litres to 110 litres. How much does a family of four save a day?
- ChallengeA reservoir holds 24,000,000 cubic metres and 800,000 is used daily. How many days will it last?
- Error redoError clinic: why is the claim that clear water has no bacteria wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | No. It must be treated and disinfected at a treatment works. | Catchment water carries silt, microbes and impurities, so it is only stored until it is treated. |
| 2 | It traps the fine suspended solids that did not settle. | The sand bed is physical filtration only, so killing germs still needs chlorine or boiling. |
| 3 | Both kill germs, but boiling happens at home while chlorination keeps protecting the water from works to tap. | Chlorine leaves a residual that lasts along the mains, while boiling treats only the water already drawn. |
| 4 | At least 20 seconds. | Soap needs enough rubbing time to remove pathogens from the hands, then rinse and dry them. |
| 5 | Gut infections such as cholera and typhoid. | Pathogens enter the water source with sewage, and drinking untreated water then causes infection. |
| 6 | To flush out water that has been sitting in the pipes before drinking or cooking with it. | Stagnant water can pick up rust and microbes, and running the tap gives steadier quality. |
| 7 | 3,500,000 cubic metres. | 500,000 multiplied by 7 gives 3,500,000. |
| 8 | 80 litres. | Each person saves 20 litres, so four save 80 litres, which is about 29,200 litres a year. |
| 9 | 30 days. | 24,000,000 divided by 800,000 gives 30. |
| 10 | Pathogens are invisible, so clear water can still carry germs and must be disinfected and boiled. | Turbidity is only one indicator; microbes must be tested for, so looks cannot settle the question. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
Drinking water goes from reservoir through coagulation, settling, sand filtration and chlorination while sewage gets screening, settling and aeration in a separate system, with residual chlorine and boiling as the last defence.Tutor Registration →
Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.