Understanding Water Properties, Pollution, and Purification

Posted on Mar 10, 2025 in Geology

Water Properties

Capillary Action

When a glass tube with a small inner diameter (capillary tube) is placed in a container of water, the water rises within the tube. This occurs because the adhesive force between water molecules and the glass is stronger than the cohesive force between water molecules.

Viscosity

Viscosity is a measure of a liquid’s resistance to flow. A higher viscosity means the liquid flows more slowly. Viscosity decreases with increasing temperature because viscosity is directly related to the attractive forces between liquid molecules.

Water Pollution

Natural Pollution: This occurs when water flows through the air or ground, picking up minerals and other substances.

Artificial Pollution: This is caused by human activities, primarily due to waste disposal, detergents, organic matter, industrial discharge, and agricultural runoff.

Water Eutrophication

Eutrophication is a natural aging process of stagnant water with excess nutrients and accumulating decomposing organic matter at the bottom.

Changes During Eutrophication

Biological Changes:

  • Significant increase in phytoplankton.
  • Dramatic growth of blue-green algae while other types disappear.
  • Increased bacterial activity.
  • Sickness and death of aquatic animals.

Physical Changes:

  • Accumulation of dead plants and animals at the bottom, slowing water flow.
  • Water becomes brown and smelly.
  • Color changes: red, green, yellow, or brown.

Chemical Changes:

  • Low dissolved oxygen, negatively impacting aquatic life. When oxygen levels drop to 2 mg/l, all animals die.
  • Increased concentration of nitrogen compounds, phosphates, and other chemicals.

Treatment of Contaminated Water

Primary Treatment: Removal of Large Solids

  1. Screening: Separating large solids.
  2. Sedimentation: Large particles settle by gravity, removing up to 35% of pollutants.
  3. Bacterial Degradation: Aerobic bacteria use oxygen to decompose organic matter.

Secondary Treatment: Removal of Dissolved Organic Matter

  1. Further Sedimentation: Removing remaining solids.

Tertiary Treatment: Removal of Dissolved Toxic Substances

  1. Chemical Treatment: Removing heavy metals and other toxic substances through chemical processes, resulting in 98% pure water.
  2. Disinfection: Adding chlorine gas to eliminate microorganisms.

Water Purification

Stages:

  1. Sieving: Preventing the passage of solid objects.
  2. Pre-chlorination: Adding Cl2 to eliminate microorganisms.
  3. Flocculation: Adding chemicals like Al2(SO4)3 to remove suspended solids.
  4. Sedimentation: Particles from flocculation settle to the bottom.
  5. Filtration: Filtering through sand and stones to remove impurities.
  6. Chlorination: Adding chlorine gas to prevent contamination by pathogenic bacteria.
  7. Fluoridation: Adding fluorine to prevent tooth decay.