Environmental Chemistry Part III: Water Chemistry and Water Pollution

Chapter 10: The Chemistry of Natural Waters

• Introduction to Water Chemistry
  • Importance of water to life and the challenges of maintaining clean water.
  • Global supply and demand trends.
  • Key chemical processes in natural waters: redox reactions, acid-base reactions, and solubility dynamics.
• Global Water Supply and Usage
  • Statistics on water use in domestic, agricultural, and industrial sectors.
  • Water scarcity and the concept of "virtual water" in goods production.
  • Sources of fresh water: groundwater, lakes, rivers (less than 0.01% of Earth's water).
• Water Chemistry Basics
  • Understanding concentrations: ppm, ppb, and their relevance in water quality.
  • Dissolution of gases (Henry's law) and volatile organic compounds in water.
• Oxidation-Reduction Chemistry in Natural Waters
  • Dissolved oxygen (O₂) as the key oxidizing agent.
  • Reactions and solubility affected by temperature and pollutants.
  • Concepts of Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD).
• Water Stratification
  • Seasonal thermal layers in lakes: epilimnion (aerobic) vs. hypolimnion (anaerobic).
  • Impacts on dissolved oxygen and nutrient distribution.
• Key Processes and Phenomena
  • Decomposition of organic matter: aerobic (to CO₂) and anaerobic (to CH₄).
  • Acid mine drainage: oxidation of FeS₂ (pyrite) and its environmental impact.
  • Water pollution by heavy metals and remediation strategies.

Chapter 11: Pollution and Purification of Water

• Sources and Types of Pollution
  • Domestic, industrial, and agricultural pollutants.
  • Nutrient overloading, eutrophication, and algal blooms.
• Water Purification Methods
  • Physical methods: sedimentation and filtration.
  • Chemical methods: chlorination, ozonation.
  • Biological methods: biofiltration and wetlands.
• Green Chemistry Approaches
  • Enzymatic processes (e.g., pectin lyase in cotton scouring) for wastewater treatment.
  • Reducing BOD and COD through innovative techniques.

Chapter 12: Toxic Heavy Metals

• Key Heavy Metals in Water Pollution
  • Focus on five heavy metals historically linked to pollution.
  • Sources, toxicity, and pathways into water systems.
• Impact and Mitigation
  • Bioaccumulation and effects on ecosystems and human health.
  • Treatment technologies: adsorption, precipitation, and ion exchange.

Teaching Notes

• Use visual aids like pE–pH diagrams, species distribution graphs, and global water flux charts to explain dynamic processes.
• Include case studies (e.g., acid mine drainage, lake stratification events) to highlight real-world relevance.
• Assign problem-solving exercises to reinforce concepts like COD calculations, redox reaction balancing, and the effects of stratification.
• Encourage discussions on green chemistry innovations for reducing environmental impact.