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Primary General Studies: Water Treatment and Public Health (Paper 1 (basics))
Primary General Studies: Water Treatment and Public Health (Paper 1 (basics))
This is the basics paper, focusing on where water comes from, what each treatment step does and simple use calculations.
Direct answers Separate trapping from killing first, then do the multiplication and subtraction with units written clearly.
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)
- FoundationWhat are the main sources of Hong Kong’s drinking water?
- FoundationWhat is the main job of alum added in a treatment works?
- FoundationCan the sand filter kill bacteria in the water?
- IntermediateWhy is chlorine added to treated water?
- IntermediateAfter water comes to the boil, how long should it keep boiling before drinking?
- IntermediateWhat water is used for flushing toilets in some parts of Hong Kong, and why?
- ChallengeA treatment works handles 400,000 cubic metres a day. How much does it handle in seven days?
- ChallengeEach person uses 130 litres a day. How much does a family of four use each day?
- ChallengeA reservoir holds 49,000,000 cubic metres and 19,000,000 is drawn off. How much is left?
- Error redoError clinic: someone says water is completely safe to drink straight after the sand filter. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Water collected in local reservoirs plus Dongjiang water imported from Guangdong. | Rainfall is heavy but the catchment area is limited, so imported water tops up the local supply. |
| 2 | It makes tiny suspended particles clump into larger flocs. | Bigger flocs settle in the settling tank and are then trapped by the sand filters. |
| 3 | No. It only traps suspended solids. | The gaps in a sand bed are far larger than bacteria, so disinfection or boiling is still needed. |
| 4 | To kill bacteria and viruses and to leave a chlorine residual that protects the water in the pipes. | Chlorine disinfects by oxidising, and the residual keeps guarding the water on its way to the taps. |
| 5 | At least one minute. | One minute of rolling boil kills most disease causing microbes, and untreated water should always be boiled. |
| 6 | Seawater, because it saves scarce fresh water. | The seawater supply has its own pipes kept separate from drinking water mains to avoid cross contamination. |
| 7 | 2,800,000 cubic metres. | 400,000 multiplied by 7 gives 2,800,000, so every digit must be kept. |
| 8 | 520 litres. | 130 times 4 is 520, and the higher the use per person the harder the reservoirs must work. |
| 9 | 30,000,000 cubic metres. | 49,000,000 minus 19,000,000 is 30,000,000, that is thirty million cubic metres. |
| 10 | The sand filter only traps solids and does not kill germs, so disinfection and boiling at home are still needed. | Each treatment step has its own job and none of them can replace disinfection. |
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.