Potable Water (Cambridge International IGCSE Environmental Management)

What is potable water?

• Potable water is water that is safe to drink

  • Contains no harmful microorganisms or toxic chemicals

• Potable water must be clean, clear and treated before people can use it for drinking or cooking

• Safe drinking water is essential for health, preventing diseases such as cholera and diarrhoea

Exam Hint Students sometimes think 'potable water is clean water', but this is too vague. Examiners seek the exact idea that potable water is safe to drink, meaning it contains no harmful pathogens or pollutants.

Stages in water treatment

• Water from rivers, lakes or reservoirs may contain dirt, organisms and pollutants

  • It must be treated to make it potable

• Water treatment uses several stages to remove solid particles, microorganisms and harmful chemicals

Screening

• Screening—passing water through large metal bars or meshes

  • Removes big objects such as leaves, sticks, plastics and rubbish

• Prevents damage to pumps and machinery in later stages

Sedimentation

• Water is left to stand in settling tanks (also known as sedimentation tanks)

  • Heavy particles such as sand and soil sink to the bottom

• Forms a layer of sludge, which is removed

• Reduces the amount of solid material that enters the filters

Filtration

• Water passes through layers of gravel, sand and sometimes activated carbon

  • Traps smaller particles such as clay, organic matter and microorganisms

• Produces much clearer water before disinfection

• Activated carbon can remove chemicals and odours

Chlorination

• A small amount of chlorine is added to kill harmful bacteria and viruses

  • Ensures the water is safe to drink

• Chlorine continues to protect the water as it travels through pipes to homes and buildings

Stages in the treatment of water

Availability of potable water

• Potable water is not available equally around the world

  • Some regions have plentiful fresh water, while others struggle with shortages

• Differences depend on climate, population, infrastructure, and access to sewage treatment

• Understanding these inequalities helps explain why some areas face water stress while others do not

Water-rich and water-poor regions

• Water-rich regions have high rainfall, many rivers or large lakes

  • Examples include tropical regions with heavy seasonal rainfall
  • Abundant surface and groundwater make the water supply more reliable

• Water-poor regions have low rainfall, dry climates or frequent droughts

  • Large parts of semi-arid and arid regions experience long dry seasons
  • Water scarcity makes it harder to provide sufficient safe drinking water

• Even water-rich regions can face shortages due to pollution events or poor water management

Urban and rural regions

• Urban regions often have better access to treated potable water

  • Cities usually have piped water systems, treatment plants and sewage networks
  • More investment in infrastructure allows a reliable water supply

• Rural regions may rely on wells, rivers or unprotected sources

  • These sources are more easily contaminated and may not be treated
  • Lack of pipes and treatment facilities makes access inconsistent

• People living in rural areas may have to travel long distances to collect water

Global inequalities in water availability and sewage treatment

• Wealthier countries have advanced water treatment plants, storage systems and safe sewage disposal

  • This ensures reliable access to clean, safe drinking water

• Low-income countries may lack infrastructure for pumping, treating or storing water

  • People may depend on unsafe streams, ponds or unprotected wells

• Poor sewage treatment leads to polluted water sources

  • Increases diseases such as cholera and diarrhoea

• Wealth affects water access: communities with more resources can build wells, buy bottled water or install filtration systems

  • Poorer communities often cannot

Exam Hint In longer answers, it is important to demonstrate the connection between water availability and health outcomes. Linking poor water access to diseases demonstrates deeper understanding and gains higher-level marks.