D

Chapter 1 Water Chemistry (1)

WATER CHEMISTRY

Lesson Objectives

  • Describe the composition, properties, physical and chemical reactions and processes in water.

  • Determine the different pollutants in water and their effects caused by technological activities.

  • Design municipal water purification and/or waste water purification.

Key Concepts

Properties of Water

  • Composition: Water (H2O) is a pure substance, a compound made of hydrogen and oxygen.

  • Natural State: Although abundant, water is rarely found in its pure form; often it must be created or purified.

Pollutants in Water

  • Water from various sources (natural springs, wells, tap) may contain trace amounts of minerals, bacteria, pesticides, and other contaminants.

  • Distillation can remove these impurities, eliminating over 99.9% of dissolved minerals.

Distillation Process

Setup Components

  • Thermometer

  • Distilling flask

  • Burner

  • Condenser

  • Receiving flask

  • Cool water in and water out

Distilled Water

  • Defined as water from which all dissolved substances are removed through evaporation and condensation.

  • While safe to drink, distilled water may have a bland taste due to the absence of essential minerals like calcium, sodium, and magnesium.

  • Overhydration can occur if consumed excessively, potentially disrupting the body's mineral balance.

Uses of Distilled Water

  • Ideal for uses requiring high purity including:

    • Medical tools and procedures.

    • Lab tests to ensure accuracy.

    • Cosmetic production.

    • Automotive applications.

    • Mixing with infant formula.

Risks of Distilled Water

  • The lack of electrolytes might lead to a deficiency in essential micronutrients.

  • Flat taste may result in reduced water consumption, affecting hydration and metabolic functions.

  • Increased urine output might lead to electrolyte imbalances.

Tap Water

Characteristics

  • Tap water is typically treated for safety, involving chlorine disinfection and filtration.

Treatment Methods

  • Bleaching Powder: Used for disinfecting, effectively killing a significant percentage of bacteria present in the water.

  • Aluminum Sulfate: Forms a gel-like precipitate to coagulate fine particles in water, improving clarity.

  • May intentionally contain fluoride to aid dental health.

  • Varies in mineral composition depending on the source (e.g., well water).

Filtered Water

  • Involves running tap water through filters to remove chlorine, bacteria, and other chemicals.

  • Most bottled water undergoes some form of filtration.

Purified Water

  • Defined as water that is mostly free of microbes and chemicals, but may still contain some minerals.

  • Must meet EPA standards, allowing no more than 10 parts per million of total dissolved solids.

Water Purification Processes

  • Reverse Osmosis: Utilizes a semi-permeable membrane to remove salts and impurities.

  • Deionization: Removes salt and mineral ions.

  • Distillation: Involves boiling water and then condensing it to remove contaminants.

Bottled Water

Types

  • Alkaline Water: Higher pH levels from electrolytic processes.

  • Fluoridated Water: Contains added fluoride for dental health.

  • Mineral Water: Sourced from mineral springs, containing natural minerals.

  • Spring Water: Flows naturally to the earth's surface.

  • Sterile Water: Meets strict sterilization standards.

FDA Regulations

  • Bottled water must be produced under sanitary conditions and monitored for safety, ensuring it is safe to drink.

Differences Between Hard and Soft Water

Hard Water

  • Contains high concentrations of minerals, particularly calcium and magnesium, leading to scale and deposits.

  • Hardness can complicate cleaning and reduce appliance efficiency.

  • Generally safe to drink; can contribute beneficially to dietary intake of required minerals.

Soft Water

  • Lacks essential minerals or has them removed (typically contains only water molecules).

  • Rainwater and distilled water are generally soft, free of minerals.

  • Softened water replaces excess minerals with sodium, potentially impacting health benefits from drinking water.

Issues with Hard Water

  • Requires more soap and cleaning agents for washing due to poor lathering capability.

  • Can lead to the formation of scale in appliances, particularly water heaters.

  • May contribute to skin issues over time due to mineral deposits.

Water Softening Process

  • Uses ion exchange to eliminate hard water minerals.

  • Sodium is introduced to soften water but can reduce some health benefits present in hard water.

  • Safe drinking levels of sodium must be monitored, generally under 200 ppm is considered safe.

Conclusion

  • Understanding water chemistry is essential for effective water purification practices and knowledge of water quality.

  • Different types of water and their treatments have significant implications for health and domestic use.