Natural Sources of Water

1. Underground Water Sources
   • Wells: Holes dug in the ground to obtain water.
   • Boreholes: Deep holes drilled to lift water using submersible pumps.
   • Springs: Sources where water flows out of the ground as streams or pools.
2. Surface Water Sources
   • Includes dams, lakes, streams, rivers, seas, and oceans.
3. Atmospheric Water Sources
   • Rainwater collected from rooftops during the rainy season.

The Water Cycle

• The water cycle, or hydrological cycle, describes the continuous circulation of water between the earth’s surface and the atmosphere:
  • Evaporation: Heat from the sun causes water to evaporate from oceans, seas, and lakes.
  • Transpiration: Plants release water vapor into the atmosphere.
  • Condensation: Water vapor cools and condenses to form clouds.
  • Precipitation: Larger droplets in clouds fall as rain, running into streams, rivers, and ultimately returning to lakes, seas, and oceans.

Physical Properties of Water

• Colorless, tasteless, and odorless liquid.
• Boils at 100ºC and freezes at 0ºC.
• Density of 1 g/cm³.

Importance of Water

• Coolant: Maintains low temperatures in engines; facilitates liquefaction in distillation.
• Solvent: Universal solvent that dissolves many substances.
• Chemical Reactant: Involved in various chemical reactions in aqueous media.
• Hydroelectric Power Generation: Moving water generates electricity.
• Recreation: Used in swimming pools.
• Transport Medium: Essential for transporting people and goods via boats and ships.

Hard and Soft Water

• Soft Water: Low mineral content; easily produces soapy bubbles (e.g., rainwater, distilled water).
• Hard Water: High mineral content; does not produce soapy bubbles easily (e.g., tap water).

Types of Water Hardness

1. Temporary Hardness
   • Caused by dissolved calcium or magnesium hydrogen carbonates; removable by boiling.
2. Permanent Hardness
   • Caused by calcium or magnesium sulphates; difficult to remove, but can be treated by distillation or chemical methods.

Advantages of Hard Water

• Provides calcium ions necessary for bones and teeth.
• Coats lead pipes, preventing lead dissolution.
• Beneficial for shell formation in animals.
• Contains essential minerals for plant and animal growth.

Disadvantages of Hard Water

• Wastes soap due to scum formation.
• Causes inefficiencies in electrical appliances (e.g., kettles and boilers).
• Can block hot water pipes.
• Spoils the finish of some fabrics.

Methods of Removing Water Hardness

1. Removing Temporary Hardness

• Boiling:
  • Heating causes hydrogen carbonates to decompose into insoluble carbonates, effectively reducing hardness.
• Addition of Calcium Hydroxide or Sodium Hydroxide:
  • Adding these substances precipitates calcium and magnesium ions as carbonates, further softening the water.

2. Removing Permanent Hardness

• Distillation:
  • Water is distilled to separate it from dissolved substances. This method is costly for large-scale applications.
• Addition of Sodium Carbonate (Soda):
  • Calcium and magnesium ions are precipitated out as carbonates, softening the water.
• Ion Exchange:
  • Hard water is passed through a resin containing sodium ions. Calcium and magnesium ions are exchanged for sodium ions, which do not cause hardness.

Water Pollution

Definition: Water pollution is the introduction of harmful substances into water due to human activities, including toxic metals, plastics, pesticides, and fertilizers.

Sources of Water Pollution

1. Domestic Sources:
   • Release of human waste and sewage into lakes and rivers.
2. Industrial Wastes:
   • Effluents from industries like breweries, tanneries, textiles, and paper, which contain toxic chemicals.
3. Agricultural Wastes:
   • Excessive use of pesticides, herbicides, and fertilizers that runoff into water bodies after rains.

Effects of Water Pollution

• Causes diseases such as cholera, typhoid, and hepatitis.
• Destroys ecosystems and severely affects aquatic life by depleting oxygen levels.
• Disrupts food chains when toxins are consumed by aquatic animals and subsequently by humans.

Ways of Controlling Water Pollution

• Limit Chemical Use:
  • Avoid excessive application of chemicals in agriculture.
• Sewage Treatment:
  • Treat sewage before discharging it into water bodies to eliminate pollutants and pathogens.
• Use of Organic Fertilizers:
  • Encourage farmers to utilize farmyard manure instead of chemical fertilizers.
• Proper Latrine Construction:
  • Build pit latrines away from water sources and consider land slope to prevent contamination.
• Legislation:
  • Implement government regulations to minimize improper dumping of industrial and domestic wastes.
• Accident Prevention:
  • Petroleum companies should adopt measures to prevent oil spills into water bodies.