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.