Potable Water (Cambridge (CIE) IGCSE Environmental Management): Revision Note

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

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

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