Potable water is water that is safe to drink. Describe how groundwater from an underground source is treated to make it potable.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
1. Groundwater is first passed through a filtration system to remove insoluble particles, solid debris and other suspended matter.
2. Before filtration, the water undergoes sedimentation or settlement, allowing larger particles to sink and be removed.
3. The filtered water is then sterilised or disinfected, typically with chlorine or UV light, to kill microorganisms, bacteria and other pathogens.
4. Finally, the treated water is tested to ensure it meets safety standards, with acceptable levels of dissolved substances, making it potable and safe to drink.
2. Before filtration, the water undergoes sedimentation or settlement, allowing larger particles to sink and be removed.
3. The filtered water is then sterilised or disinfected, typically with chlorine or UV light, to kill microorganisms, bacteria and other pathogens.
4. Finally, the treated water is tested to ensure it meets safety standards, with acceptable levels of dissolved substances, making it potable and safe to drink.
Examiner tips
- Use the exact terms: filtration, sedimentation, sterilisation, disinfection, potable water.
- Show the sequence: filtration → sedimentation → disinfection → quality check.
- Mention that the final step is to meet required quality standards.
- Keep each point short and to the point to match the 4‑mark structure.
Common mistakes
- Confusing filtration with disinfection, or vice versa.
- Omitting the sedimentation step or not specifying that it removes larger particles.
- Failing to state that the final water must meet safety standards or acceptable dissolved substance levels.
Mark scheme (4 marks)
- Filtration is used to remove insoluble particles / solid particles / debris
- Sedimentation / settlement allows larger particles to sink / settle out before filtration
- Sterilisation / disinfection is carried out to kill microorganisms / bacteria / pathogens
- The treated water must be safe to drink / have acceptable levels of dissolved substances / meet required quality standards
Key terms in this question
Related
- All Eduqas GCSE Chemistry revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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