Potable Water

Potable Water

• Definition: Potable water is safe to drink but is not necessarily pure (only H2O).

• Criteria for Potability:

  • Low levels of dissolved substances.

  • pH of 6.5 to 8.5 (not too acidic or alkaline).

  • Absence of microorganisms (bacteria, fungi).

Sources of Potable Water

• Fresh Water: Countries with adequate rain supply can access fresh water.

  • Examples:

    • In the UK, rainwater collects as surface water (lakes, rivers, reservoirs) and groundwater (aquifers).

• Surface Water vs Groundwater:

  • Surface Water: Accessible, frequently replenished by rain—vulnerable to evaporation.

  • Groundwater: Alternative source, especially in warmer areas where surface water may dry up.

Treatment of Fresh Water

• Treatment Steps:

  1. Filtration through wire mesh to remove large debris (e.g., twigs).

  2. Further filtration through sand and gravel for smaller solids.

  3. Sterilization to eliminate harmful microbes:

     • Methods include bubbling chlorine gas, exposing to ozone, or using ultraviolet light.

Desalination Process

• Need for Desalination: Essential in arid regions (e.g., Middle East) where fresh water is scarce.

• Techniques:

  • Distillation:

    • Similar to simple distillation, involving boiling salty water to collect and condense water vapor.

  • Reverse Osmosis:

    • Saltwater is passed through a membrane that allows only water molecules to pass, trapping ions and larger molecules.

• Challenges:

  • Both techniques are energy-intensive and costly, making large-scale water production impractical.