Lecture Notes: Potable vs. Pure Water

Key Objectives

• Understand the difference between potable and pure water
• Describe the steps to produce potable water from fresh and salty water

Introduction

• Drinking water is essential for human life.
• Not all water is safe for consumption.
• Potable water must have:
  • Low levels of dissolved salts (e.g., sodium chloride)
  • Low levels of microbes (bacteria)

Definitions

• Potable Water: Safe to drink, contains small amounts of dissolved substances.
• Pure Water: Chemically pure, contains no dissolved substances.

Sources of Fresh Water

• In the UK, rainwater is the primary source of potable water.
• Rainwater characteristics:
  • Contains low levels of dissolved substances.
  • Collects in aquifers, lakes, rivers, and reservoirs.
• All these are considered good sources of fresh water.

Producing Potable Water from Fresh Water

1. Source Selection: Use a good fresh water source, such as a river.
2. Filtration:
   • Pass water through filter beds.
   • Removes materials such as leaves and suspended particles.
3. Sterilization:
   • Kills microbes.
   • In the UK, chlorine is used.
   • Other regions may use ozone or ultraviolet light.

Challenges with Fresh Water Scarcity

• In some regions, fresh water is scarce.
• Seawater, with high levels of dissolved minerals, may be the only source.

Producing Potable Water from Salty Water

• Desalination: Reduces dissolved minerals to acceptable levels.
  • Methods:
    1. Distillation:
       • Previously studied topic.
    2. Reverse Osmosis:
       • Water is passed through membranes.
• Both methods:
  • Require large amounts of energy.
  • Are expensive to implement.

Conclusion

• The process of making water potable involves filtration, sterilization, and possibly desalination.
• Important to understand these concepts for potential exam questions.

• Additional Resources: Refer to the revision workbook for more questions and practice on potable water.