Knowledge Organiser: Water Treatment
Part of Water Treatment · GCSE GCSE Chemistry revision
This topic summary covers Knowledge Organiser: Water Treatment within Water Treatment for GCSE Chemistry. Revise Water Treatment in Using Resources for GCSE Chemistry with 20 exam-style questions and 15 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 13 of 13 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 13 of 13
Practice
20 questions
Recall
15 flashcards
Knowledge Organiser: Water Treatment
Key Terms
- Potable water: Safe to drink — not the same as pure water
- Sterilisation: Killing microorganisms (e.g. by chlorination)
- Distillation: Heating to steam then condensing — removes all dissolved substances but uses lots of energy
- Desalination: Removing salt from seawater — by distillation or reverse osmosis
- Sedimentation: Particles settle under gravity in tanks
Must-Know Facts
- 4 stages: Screening → Sedimentation → Filtration → Chlorination (SSFC)
- Chlorination kills bacteria and pathogens
- Potable water ≠ pure water (still has dissolved minerals)
- Desalination is expensive due to high energy use
- Sewage treatment: Primary (physical) → Secondary (biological) → Tertiary (chemical, HT)
- Sludge from sewage treatment produces methane gas for energy
Key Equations
- No calculation equations — descriptive/process topic
- Chlorination: Cl₂ + H₂O → HCl + HClO (kills microorganisms)
- Water treatment order: Screening → Sedimentation → Filtration → Chlorination
Common Mistakes
- Saying potable water is pure water: Potable water is SAFE TO DRINK — it still contains dissolved minerals and is NOT chemically pure
- Getting the treatment stages in the wrong order: The correct order is Screening → Sedimentation → Filtration → Chlorination — mixing up filtration and sedimentation loses marks
- Saying distillation is the normal water treatment method: Distillation produces pure water but uses too much energy for everyday water supply — chlorination is used for potable water treatment
- Forgetting why desalination is limited: Desalination is not widely used because it requires very high energy input — it is only cost-effective in water-scarce regions with cheap energy
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Practice Questions for Water Treatment
What does the term 'potable water' mean?
Explain what happens to the sewage sludge produced during waste water treatment, and why this process is useful.
Quick Recall Flashcards
20 questions on Water Treatment — practise free
Instant marking, adaptive difficulty, and 15 spaced repetition flashcards. Free until your GCSEs.
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