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Primary General Studies: Water Treatment and Public Health (Paper 2 (intermediate))
Primary General Studies: Water Treatment and Public Health (Paper 2 (intermediate))
This is the intermediate paper, adding process order, sewage treatment and percentage calculations.
Direct answers Write out the full process before comparing options, and for percentages find the part first, then the remainder.
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 is the correct order of the four main treatment steps?
- FoundationWhat happens to the sludge that collects at the bottom of a settling tank?
- FoundationWhat is usually the first step in sewage treatment?
- IntermediateWhat does secondary sewage treatment rely on to break down organic matter?
- IntermediateWhat does a higher turbidity reading mean?
- IntermediateWhy must drinking water mains and sewers be kept completely apart?
- ChallengeA works produces 350,000 cubic metres a day and loses 12 per cent in the process. How much is actually supplied?
- ChallengeA household uses 520 litres a day and saves 15 per cent by showering instead of bathing. What is the new daily use?
- ChallengeThe city uses 2,500,000 cubic metres a day and flushing takes 32 per cent. How much goes to flushing?
- Error redoError clinic: a student lists the steps as disinfection, filtration, coagulation, settling. Why does that fail?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Coagulation, settling, sand filtration, then chlorination. | Particles are enlarged first, settled next, filtered out after that and disinfected last, so a different order fails. |
| 2 | It is pumped out, dewatered, then sent to landfill or another facility. | Sludge is mostly water, so dewatering cuts the volume and the transport cost. |
| 3 | Screening out large rubbish and solids. | Large debris blocks pipes and pumps, so removing it protects the equipment that follows. |
| 4 | Micro organisms working in an aerated tank. | Aeration supplies oxygen so microbes can break organic matter into simpler substances. |
| 5 | More suspended particles, so the water is less clear. | High turbidity shields microbes from disinfection, so treatment works keep it low. |
| 6 | So sewage cannot seep into drinking water and cause cross contamination. | A cross connection lets pathogens in sewage reach tap water and can cause outbreaks of gut illness. |
| 7 | 308,000 cubic metres. | 350,000 times 0.12 is 42,000 lost, and 350,000 minus 42,000 is 308,000. |
| 8 | 442 litres. | 520 times 0.15 is 78 litres, and 520 minus 78 leaves 442 litres. |
| 9 | 800,000 cubic metres. | 2,500,000 times 0.32 is 800,000, which is why flushing is a target for saving water. |
| 10 | In that order flocs clog the filters and unsettled water makes disinfection useless. | Coagulation and settling must come before filtration, and disinfection belongs at the clean end of the works. |
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 →
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