12.1.2 Quality of Water from Natural Resources

This topic explains that water from natural resources contains many dissolved substances — some beneficial and some harmful.

Definition

Water from natural resources such as lakes, streams, and underground rivers can contain many dissolved substances that can be beneficial or harmful.

Simple explanation: Natural water is never pure — it contains different substances, some good for us and some bad.

Main Idea

Water from natural sources is not pure. It contains dissolved substances that can be:

• Beneficial — helpful or necessary for life
• Harmful — dangerous to health or the environment

The quality of water depends on what is dissolved in it.

Simple explanation: The quality of natural water depends on what substances it contains.

Core Concept

Beneficial vs Harmful Substances

Detailed Explanation

Beneficial Substances in Natural Water

• Where do fish and other marine life get their oxygen? Water contains dissolved oxygen.
• This oxygen is responsible for the survival of aquatic organisms.

• Natural water can contain metals such as iron, sodium, potassium, magnesium, calcium, manganese, zinc, and copper.
• Some of these metals are necessary for life.
• For example:
• Iron is necessary for the production of hemoglobin in the blood, which carries oxygen to the cells.
• Zinc, copper, and manganese activate enzyme activity for the proper functioning of biological systems.

Simple explanation: Dissolved oxygen keeps fish alive; minerals like iron and zinc are essential for human health.

Harmful Substances in Natural Water

1. Toxic metal compounds: - Some metal compounds are toxic (e.g., lead, arsenic, mercury).

• Plastic waste can pollute water bodies.
• This is a serious threat to aquatic life and ecosystems.

• Wastewater can enter natural water supplies.
• Wastewater carries pathogens, bacteria, viruses, and other harmful substances.
• These pollutants pose a serious threat to humans and aquatic life.

• Natural water sources can contain harmful microbes such as bacteria, viruses, and parasites.
• These can cause waterborne diseases such as:
• Diarrhea
• Dysentery
• Cholera
• Stomach upsets

• Fertilizers add nitrates to water bodies through agricultural runoff.
• High concentrations of nitrates in drinking water cause health risks, especially for young children.

• Phosphates in fertilizers and detergents can enter water bodies through runoff.
• High concentrations of phosphate can cause eutrophication.
• This can cause harmful algae blooms and oxygen depletion in water bodies.
• Detergents used in water systems can destroy the outer mucous membranes that protect fish from bacteria and parasites.
• In addition, detergents can also damage their gills.

Simple explanation: Harmful substances in water include toxic metals, plastics, sewage, microbes, nitrates, and phosphates — all of which can harm health and the environment.

Intermediate Level

Why Dissolved Oxygen Is Important

• Aquatic organisms (fish, insects, plants) need oxygen to survive.
• Oxygen dissolves in water from the atmosphere and from photosynthesis by aquatic plants.
• If oxygen levels drop too low, fish and other organisms die.

Simple explanation: Fish need oxygen just like we do — they get it from dissolved oxygen in water.

Why Essential Minerals Are Important

Simple explanation: Minerals in water are essential for many body functions.

Why Harmful Substances Are Dangerous

Simple explanation: Harmful substances can make water unsafe for drinking and harm aquatic life.

What Is Eutrophication?

Eutrophication is the process where a water body becomes enriched with nutrients (especially nitrates and phosphates).

• Nutrients enter the water (from fertilizers, detergents).
• Algae grow rapidly (algae bloom).
• Algae die and decompose.
• Decomposition uses up oxygen in the water.
• Oxygen depletion kills fish and other aquatic life.

Simple explanation: Too many nutrients cause algae to grow, which then die and use up all the oxygen, killing fish.

Waterborne Diseases

Simple explanation: Waterborne diseases are caused by harmful microbes in water.

Important Points

• - Water from natural resources contains dissolved substances — both beneficial and harmful.
• - Beneficial substances:
• - Dissolved oxygen (for aquatic life)
• - Essential minerals (Ca, Mg, K, Fe, Zn, Cu, Mn)
• - Harmful substances:
• - Toxic metal compounds
• - Plastics
• - Sewage
• - Harmful microbes
• - Nitrates from fertilizers
• - Phosphates from fertilizers and detergents
• - Water quality depends on what is dissolved in the water.
• - Water treatment is needed to remove harmful substances.

Remember

• - Beneficial substances: dissolved oxygen, essential minerals.
• - Harmful substances: toxic metals, plastics, sewage, microbes, nitrates, phosphates.
• - Dissolved oxygen → keeps aquatic life alive.
• - Essential minerals → needed for health (Fe, Zn, Cu, Mn, Ca, Mg, K, Na).
• - Harmful microbes → cause waterborne diseases.
• - Nitrates → health risks for children.
• - Phosphates → cause eutrophication.

Common Mistakes

• 1. Thinking natural water is pure. Natural water contains many dissolved substances.
• 2. Thinking all dissolved substances are harmful. Some are beneficial (oxygen, minerals).
• 3. Confusing the harmful effects of nitrates and phosphates. Nitrates → health risks; phosphates → eutrophication.
• 4. Thinking sewage only carries human waste. It also carries pathogens, bacteria, and viruses.
• 5. Forgetting that plastics harm aquatic life. Plastic waste pollutes water bodies and harms animals.
• 6. Thinking minerals in water are unnecessary. Essential minerals like iron, zinc, and calcium are needed for health.

Quick Revision

• Water from natural resources (lakes, streams, underground rivers) can contain many dissolved substances that can be beneficial or harmful.
• Beneficial substances:
• Dissolved oxygen: responsible for the survival of aquatic organisms.
• Essential minerals: iron, sodium, potassium, magnesium, calcium, manganese, zinc, copper — some are necessary for life (e.g., iron for hemoglobin, zinc/copper/manganese for enzyme activity).
• Harmful substances:
• Toxic metal compounds: harmful to health.
• Plastics: threaten aquatic life and ecosystems.
• Wastewater: carries pathogens, bacteria, viruses.
• Harmful microbes: cause waterborne diseases (diarrhea, dysentery, cholera, stomach upsets).
• Nitrates from fertilizers: health risks, especially for young children.
• Phosphates from fertilizers and detergents: cause eutrophication, algae blooms, oxygen depletion; detergents damage fish mucous membranes and gills.

60-Second Revision

• Beneficial: dissolved oxygen, essential minerals.
• Harmful: toxic metals, plastics, sewage, microbes, nitrates, phosphates.
• Dissolved oxygen → keeps fish alive.
• Essential minerals → needed for health.
• Harmful microbes → waterborne diseases.
• Nitrates → health risks for children.
• Phosphates → eutrophication.
• Warning: natural water contains both beneficial and harmful substances.