12.3 Water Pollution

This topic explains water pollution — how water becomes contaminated — and focuses on household wastes as a major source of pollution.

Definition

Water pollution occurs when water contains substances that make it unfit for human use or harmful to aquatic life.

Simple explanation: Water pollution is when harmful substances get into water.

Main Idea

Water is very good at dissolving substances. As water from rain and snow flows over rocks and through soil, it dissolves minerals.

The freshwater we drink or use for our daily life processes is a dilute solution containing a number of minerals. When these minerals are in sufficient concentration, water becomes unfit for human use.

• Household waste
• Agricultural waste
• Livestock waste
• Pesticides
• Oil leaks
• Detergents
• Septic tanks
• Petroleum and natural gas production

Simple explanation: Water gets polluted naturally by dissolving minerals, and also by human activities.

Core Concept

Sources of Water Pollution

Detailed Explanation

How Water Becomes Polluted Naturally

• Water is a very good solvent.
• As water flows over rocks and through soil, it dissolves minerals.
• The freshwater we drink is a dilute solution of minerals.
• When minerals are in sufficient concentration, water becomes unfit for human use.

Simple explanation: Water dissolves minerals from rocks and soil — too many minerals make it unfit to drink.

Household Wastes

• Human wastes
• Livestock wastes
• Soaps and detergents
• Paints and oil
• Food and vegetable wastes
• Garbage

Effects of household wastes:

• Although detergents have stronger cleansing action than soap, they remain in the water for a long time.
• They make water unfit for aquatic life.
• When household water containing detergents is discharged into lakes, ponds, rivers, etc., it causes the death of aquatic life.

• Chemical and bacterial contents in household water can contaminate surface and underground water.
• Bacterial contents present in water may cause infectious diseases such as:
• Cholera
• Jaundice
• Hepatitis
• Typhoid
• Dysentery

Simple explanation: Household waste — especially detergents and bacteria — pollutes water and causes disease.

Society, Technology and Science

The book provides this note:

> "Water treatment is essential for many reasons. > > Through water purification, we can avoid drinking impure and contaminated water, which causes many epidemic diseases and is unsafe for healthy life. It removes bacteria, viruses and parasites which may cause diarrhoea, dysentery, botulism, typhoid, cholera, polio, and hepatitis. It also removes heavy metals like As, Cr, and Pb which can cause long term neurological problems, kidney diseases, nausea, dizziness, and cancer. It also improves the flavor and appearance."

Simple explanation: Water treatment protects us from diseases and harmful substances.

Intermediate Level

Why Water Is Easily Polluted

• Water is the universal solvent.
• It dissolves more substances than any other liquid.
• This means pollutants easily dissolve in water and spread.
• Once dissolved, pollutants are hard to remove.

Simple explanation: Because water dissolves so many things, it's easy to pollute.

Household Wastes — In Detail

• Human wastes — contain pathogens.
• Livestock wastes — contain pathogens and nutrients.
• Soaps and detergents — contain phosphates and surfactants.
• Paints and oil — contain toxic chemicals.
• Food and vegetable wastes — decompose and use up oxygen.
• Garbage — contains plastics, chemicals, and pathogens.

Effects:

Diseases from Polluted Water

Simple explanation: Polluted water carries microbes that cause serious diseases.

Why Detergents Are Harmful

• Detergents remain in water for a long time (they don't break down easily).
• They reduce surface tension, which can harm aquatic organisms.
• They destroy the outer mucous membranes of fish.
• They damage fish gills.
• They contain phosphates that cause eutrophication.

Simple explanation: Detergents stay in water, harm fish, and cause algae blooms.

Why Water Treatment Is Essential

• Removes bacteria, viruses, parasites — preventing diseases.
• Removes heavy metals (As, Cr, Pb) — preventing long-term health problems.
• Improves flavour and appearance — making water pleasant to drink.
• Protects aquatic life — by removing harmful substances.

Simple explanation: Water treatment makes water safe for drinking and protects the environment.

Important Points

• - Water pollution: water contains substances that make it unfit for human use or harmful to aquatic life.
• - Natural pollution: water dissolves minerals from rocks and soil.
• - Household wastes: human wastes, livestock wastes, soaps/detergents, paints/oil, food/vegetable wastes, garbage.
• - Detergents: remain in water; kill aquatic life.
• - Bacteria in water: cause cholera, jaundice, hepatitis, typhoid, dysentery.
• - Water treatment is essential to remove harmful substances and improve flavour and appearance.
• - Heavy metals (As, Cr, Pb) in water can cause long-term health problems.

Remember

• - Water pollution = harmful substances in water.
• - Natural pollution = dissolved minerals from rocks and soil.
• - Household wastes = detergents, human waste, garbage, paints, oil.
• - Detergents → remain in water → kill aquatic life.
• - Bacteria → cause cholera, typhoid, hepatitis, dysentery.
• - Water treatment → essential for safe drinking water.
• - Heavy metals (As, Cr, Pb) → long-term health problems.

Common Mistakes

• 1. Thinking water pollution is only caused by industry. Household wastes are also a major source.
• 2. Thinking detergents are harmless. Detergents remain in water and kill aquatic life.
• 3. Thinking waterborne diseases are rare. They are common in areas with poor sanitation.
• 4. Forgetting natural pollution. Water naturally dissolves minerals from rocks and soil.
• 5. Thinking water treatment is unnecessary. It is essential for safe drinking water.
• 6. Thinking heavy metals are safe in small amounts. Even small amounts can cause long-term health problems.

Quick Revision

• Water pollution: water contains substances that make it unfit for human use or harmful to aquatic life.
• Natural pollution: water dissolves minerals from rocks and soil.
• Sources of water pollution (human activities):
• Household waste
• Agricultural waste
• Livestock waste
• Pesticides
• Oil leaks
• Detergents
• Septic tanks
• Petroleum and natural gas production
• Household wastes include:
• Human wastes
• Livestock wastes
• Soaps and detergents
• Paints and oil
• Food and vegetable wastes
• Garbage
• Effects of household wastes:
• Detergents remain in water for a long time and make water unfit for aquatic life; they cause death of aquatic life.
• Chemical and bacterial contents can contaminate surface and underground water.
• Bacterial contents may cause infectious diseases such as cholera, jaundice, hepatitis, typhoid, dysentery.
• Water treatment is essential: removes bacteria, viruses, parasites; removes heavy metals (As, Cr, Pb); improves flavour and appearance.

60-Second Revision

• Water pollution = harmful substances in water.
• Household wastes = detergents, human waste, garbage.
• Detergents → kill aquatic life.
• Bacteria → cause cholera, typhoid, hepatitis.
• Water treatment → essential.
• Warning: household waste is a major source of water pollution — not just industry.