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Environmental Pollution

3.2 Environmental Pollution
SCIENCE • Form 5 • Chapter 3: Sustainability of the Environment

3.2 Environmental Pollution

Environmental pollution refers to unwanted changes in the physical, chemical, or biological characteristics of the environment, namely air, water, and soil. It causes harm and discomfort to living organisms and leads to severe environmental issues such as flash floods.

Learning Objectives

  • Define environmental pollution and identify its four main types: air, water, land, and thermal pollution.
  • State the natural and man-made sources of environmental pollution.
  • Explain the process of eutrophication and its negative impacts on aquatic ecosystems.
  • Define Biochemical Oxygen Demand (BOD) and explain how methylene blue solution is used to assess water pollution levels.
  • Describe the purification of contaminated water using Green Technology, specifically Effective Microorganism (EM) mud balls, and the roles of microorganisms contained within them.

Relationship Between Water Pollution Level, BOD, and Methylene Blue Decolourisation Time

Compare clean water and polluted water to see how organic contamination affects dissolved oxygen, bacterial demand, and the rate of methylene blue decolourisation.

Comparison of clean water and polluted water A horizontal comparison diagram with two panels. The left panel shows clean water with high dissolved oxygen, low BOD, and a long time for methylene blue to decolourise. The right panel shows polluted water with low dissolved oxygen, high BOD, and rapid methylene blue decolourisation. Clean Water Polluted Water High dissolved O₂ Low BOD Long time to decolourise methylene blue Low dissolved O₂ High BOD Rapid decolourisation of methylene blue Few decomposing microorganisms Plenty of oxygen available Many decomposing microorganisms Oxygen is used up quickly Methylene blue stays blue longer Methylene blue loses colour faster

Short Explanation

Definition

Environmental pollution refers to unwanted changes in the physical, chemical, or biological characteristics of environmental components, namely air, water, and soil, that cause harm and discomfort to all life forms.

Environmental pollution alters our air, water, and land, creating severe imbalances in ecosystems. In water bodies, domestic and agricultural discharges add excess nitrates and phosphates, causing eutrophication, where explosive algal growth depletes dissolved oxygen.

Four Main Types of Environmental Pollution

Environmental pollution is grouped into four main types: air pollution, water pollution, land pollution, and thermal pollution.

Pollution Parameters

The Air Pollutant Index (API) is the parameter measured to determine air pollution level. The Biochemical Oxygen Demand (BOD) is the parameter measured to determine water pollution level.

Eutrophication

Eutrophication is the ecosystem response towards an increase of phosphate ions and nitrate ions, originating from detergents, fertilisers, and garbage, in an aquatic ecosystem. Excessive supply of nitrate ions causes rapid algal growth, known as an algal bloom. This reduces dissolved oxygen content in water, leading to the death of aquatic animals and plants.

Biochemical Oxygen Demand (BOD)

BOD is the amount of dissolved oxygen needed by microorganisms such as bacteria to decompose organic substances in a water resource. A higher BOD means a larger population of decomposing microorganisms in the water. Therefore, a higher level of water pollution corresponds to a higher BOD and a lower dissolved oxygen level.

Measuring Water Pollution Using Methylene Blue Solution

Methylene blue solution acts as an indicator of dissolved oxygen. In water samples with low dissolved oxygen, which are highly polluted, methylene blue decolourises rapidly. The higher the level of water pollution, the shorter the time taken for the methylene blue solution to decolourise.

Safety precaution: When adding methylene blue solution with a syringe, the needle must be placed under the surface of the water sample to prevent atmospheric oxygen from dissolving into the sample. Bottles must be sealed and stored in a dark cupboard.

Purification of Contaminated Water Using Green Technology: EM Mud Balls

Effective Microorganism (EM) mud balls are a Green Technology method used to treat contaminated rivers and water bodies in Malaysia.

Three main types of microorganisms are found in EM mud balls:

  • Lactic acid bacteria such as Lactobacillus casei — treats sewage, eliminates foul odour in water, stunts the growth of dangerous microorganisms, and facilitates the decay of organic substances.
  • Photosynthetic bacteria such as Rhodopseudomonas palustris — uses organic substances to synthesise useful substances such as amino acids and sugars for aquatic animals and plants to feed on.
  • Yeast (Saccharomyces cerevisiae) — produces substances needed for the growth of green plants.

Sources of Environmental Pollution

Pollution can come from natural processes or from human activities.

Sources of environmental pollution for each type of pollution.
Type of Pollution Sources
Air Pollution Burning of fossil and biomass fuels, automobile exhaust gases, decaying organic substances and waste. Natural sources: volcanic eruptions, forest fires, dust storms, decaying organic waste. Man-made sources: exhaust gases from motorised equipment or vehicles, blast furnaces, thermal power stations, industries, and garbage disposal sites.
Water Pollution Waste such as wastewater, domestic waste including detergents and sewage, solid waste such as rubbish, and industrial waste such as grease. Agricultural chemicals such as chemical fertilisers and pesticides. Oil spills.
Land Pollution Excessive use of fertilisers and pesticides, inappropriate management of solid waste, acid rain, nuclear waste, and electronic waste.
Thermal Pollution Deforestation, industrial activities, and fuel combustion in vehicles or machines.

Steps to Make EM Mud Balls

Follow these steps to prepare Effective Microorganism mud balls for water purification.

  1. 1Pour 1.4 kg soil and 70 g EM Bokashi or rice bran into a basin and mix well.
  2. 2Add 500 cm³ of EM solution to the mixture and mix thoroughly.
  3. 3Roll the mixture into EM mud balls.
  4. 4Line the base of a tray with newspaper and place the EM mud balls in the tray.
  5. 5Keep the tray away from sunlight or strong winds to prevent balls from drying quickly.
  6. 6Mud balls are ready for use when their surface is covered with white fungi.

Try to Answer First

Answer in your mind, then press “Check Answer”.

1

What is meant by Biochemical Oxygen Demand (BOD)?

Answer: The amount of dissolved oxygen needed by microorganisms, such as bacteria, to decompose organic substances in a water resource.
2

What happens to the time taken for methylene blue solution to decolourise as the water pollution level increases?

Answer: The time taken for methylene blue solution to decolourise becomes shorter; it decolourises faster.
3

Name two types of microorganisms found in Effective Microorganism (EM) mud balls and state one role of each.

Answer: Lactic acid bacteria (Lactobacillus casei) treats sewage, eliminates foul odours, inhibits harmful microorganisms, or facilitates decay of organic substances. Photosynthetic bacteria (Rhodopseudomonas palustris) synthesises useful substances such as amino acids and sugars from organic substances for aquatic life. Alternatively, yeast (Saccharomyces cerevisiae) produces substances needed for the growth of green plants.

Common Mistakes

  • !Confusing the parameter for air pollution with water pollution: thinking API measures water pollution and BOD measures air pollution. API is for air; BOD is for water.
  • !Misinterpreting the methylene blue decolourisation time: mistakenly thinking that polluted water takes a longer time to decolourise methylene blue. In fact, high pollution means low oxygen, so methylene blue loses its colour faster.
  • !Neglecting the syringe safety precaution: injecting methylene blue above the water surface instead of placing the needle under the surface of the water, which allows atmospheric oxygen to enter and skew results.
  • !Confusing eutrophication causes: attributing eutrophication solely to toxic industrial chemicals rather than the accumulation of phosphate and nitrate ions from fertilisers, detergents, and sewage.

Concept Misunderstandings

Misconception

High BOD means the water has a lot of dissolved oxygen.

Correct Concept

High BOD means microorganisms demand a lot of oxygen because there is a lot of organic matter to decompose. As a result, the actual dissolved oxygen available in the water is very low.

Misconception

EM mud balls purify water using harsh chemical disinfectants.

Correct Concept

EM mud balls are a Green Technology method using beneficial living microorganisms, namely lactic acid bacteria, photosynthetic bacteria, and yeast, to naturally decompose pollutants and suppress harmful bacteria.

Summary

  • Environmental pollution encompasses unwanted physical, chemical, or biological changes in air, water, and soil, grouped into air, water, land, and thermal pollution.
  • Air pollution is monitored by the Air Pollutant Index (API), while water pollution is measured using Biochemical Oxygen Demand (BOD).
  • Eutrophication occurs when excess nitrates and phosphates cause rapid algal blooms, depleting dissolved oxygen and killing aquatic life.
  • Higher water pollution corresponds to higher BOD and lower dissolved oxygen, causing methylene blue solution to decolourise in a shorter period of time.
  • Contaminated water can be treated using Green Technology through EM mud balls, which contain lactic acid bacteria, photosynthetic bacteria, and yeast to restore water quality.

Short Activity

A. Objective Quiz

1 Which of the following correctly describes the relationship between the water pollution level, BOD, and the time taken for methylene blue solution to decolourise?

2 What is the primary role of lactic acid bacteria such as Lactobacillus casei in EM mud balls?

B. Fill in the Blanks

3 The ecosystem response towards an increase of phosphate ions and nitrate ions in an aquatic ecosystem that causes rapid algal growth is known as .

 

4 During the water test with methylene blue, the needle of the syringe must be placed the surface of the water sample when adding the solution.

 

C. Drag and Drop: Match Each Microorganism or Parameter to Its Function

Drag each item to the correct function or definition. On a phone, tap an answer first, then tap a matching box. Tap the Answer Choices area to return a selected item.

Concept / Microorganism
Lactobacillus casei
Rhodopseudomonas palustris
Saccharomyces cerevisiae
Biochemical Oxygen Demand
Function / Definition
1 Treats sewage, eliminates foul odour, and stunts the growth of dangerous microorganisms
2 Synthesises amino acids and sugars from organic substances for aquatic organisms
3 Yeast that produces substances needed for the growth of green plants
4 Amount of dissolved oxygen needed by microorganisms to decompose organic matter

C. Match Each Microorganism or Parameter to Its Function

Write the correct concept or microorganism next to each function or definition.

Function / Definition Concept / Microorganism
1. Treats sewage, eliminates foul odour, and stunts the growth of dangerous microorganisms  
2. Synthesises amino acids and sugars from organic substances for aquatic organisms  
3. Yeast that produces substances needed for the growth of green plants  
4. Amount of dissolved oxygen needed by microorganisms to decompose organic matter  

Answer choices: Lactobacillus casei • Rhodopseudomonas palustris • Saccharomyces cerevisiae • Biochemical Oxygen Demand

Keywords

Environmental pollution Thermal pollution Eutrophication Biochemical Oxygen Demand (BOD) Air Pollutant Index (API) Methylene blue solution Effective Microorganism (EM) mud balls
The views expressed in the notes here are those of the contributor and don’t necessarily represent the views of Pandai.

Environmental Pollution

3.2 Environmental Pollution
SCIENCE • Form 5 • Chapter 3: Sustainability of the Environment

3.2 Environmental Pollution

Environmental pollution refers to unwanted changes in the physical, chemical, or biological characteristics of the environment, namely air, water, and soil. It causes harm and discomfort to living organisms and leads to severe environmental issues such as flash floods.

Learning Objectives

  • Define environmental pollution and identify its four main types: air, water, land, and thermal pollution.
  • State the natural and man-made sources of environmental pollution.
  • Explain the process of eutrophication and its negative impacts on aquatic ecosystems.
  • Define Biochemical Oxygen Demand (BOD) and explain how methylene blue solution is used to assess water pollution levels.
  • Describe the purification of contaminated water using Green Technology, specifically Effective Microorganism (EM) mud balls, and the roles of microorganisms contained within them.

Relationship Between Water Pollution Level, BOD, and Methylene Blue Decolourisation Time

Compare clean water and polluted water to see how organic contamination affects dissolved oxygen, bacterial demand, and the rate of methylene blue decolourisation.

Comparison of clean water and polluted water A horizontal comparison diagram with two panels. The left panel shows clean water with high dissolved oxygen, low BOD, and a long time for methylene blue to decolourise. The right panel shows polluted water with low dissolved oxygen, high BOD, and rapid methylene blue decolourisation. Clean Water Polluted Water High dissolved O₂ Low BOD Long time to decolourise methylene blue Low dissolved O₂ High BOD Rapid decolourisation of methylene blue Few decomposing microorganisms Plenty of oxygen available Many decomposing microorganisms Oxygen is used up quickly Methylene blue stays blue longer Methylene blue loses colour faster

Short Explanation

Definition

Environmental pollution refers to unwanted changes in the physical, chemical, or biological characteristics of environmental components, namely air, water, and soil, that cause harm and discomfort to all life forms.

Environmental pollution alters our air, water, and land, creating severe imbalances in ecosystems. In water bodies, domestic and agricultural discharges add excess nitrates and phosphates, causing eutrophication, where explosive algal growth depletes dissolved oxygen.

Four Main Types of Environmental Pollution

Environmental pollution is grouped into four main types: air pollution, water pollution, land pollution, and thermal pollution.

Pollution Parameters

The Air Pollutant Index (API) is the parameter measured to determine air pollution level. The Biochemical Oxygen Demand (BOD) is the parameter measured to determine water pollution level.

Eutrophication

Eutrophication is the ecosystem response towards an increase of phosphate ions and nitrate ions, originating from detergents, fertilisers, and garbage, in an aquatic ecosystem. Excessive supply of nitrate ions causes rapid algal growth, known as an algal bloom. This reduces dissolved oxygen content in water, leading to the death of aquatic animals and plants.

Biochemical Oxygen Demand (BOD)

BOD is the amount of dissolved oxygen needed by microorganisms such as bacteria to decompose organic substances in a water resource. A higher BOD means a larger population of decomposing microorganisms in the water. Therefore, a higher level of water pollution corresponds to a higher BOD and a lower dissolved oxygen level.

Measuring Water Pollution Using Methylene Blue Solution

Methylene blue solution acts as an indicator of dissolved oxygen. In water samples with low dissolved oxygen, which are highly polluted, methylene blue decolourises rapidly. The higher the level of water pollution, the shorter the time taken for the methylene blue solution to decolourise.

Safety precaution: When adding methylene blue solution with a syringe, the needle must be placed under the surface of the water sample to prevent atmospheric oxygen from dissolving into the sample. Bottles must be sealed and stored in a dark cupboard.

Purification of Contaminated Water Using Green Technology: EM Mud Balls

Effective Microorganism (EM) mud balls are a Green Technology method used to treat contaminated rivers and water bodies in Malaysia.

Three main types of microorganisms are found in EM mud balls:

  • Lactic acid bacteria such as Lactobacillus casei — treats sewage, eliminates foul odour in water, stunts the growth of dangerous microorganisms, and facilitates the decay of organic substances.
  • Photosynthetic bacteria such as Rhodopseudomonas palustris — uses organic substances to synthesise useful substances such as amino acids and sugars for aquatic animals and plants to feed on.
  • Yeast (Saccharomyces cerevisiae) — produces substances needed for the growth of green plants.

Sources of Environmental Pollution

Pollution can come from natural processes or from human activities.

Sources of environmental pollution for each type of pollution.
Type of Pollution Sources
Air Pollution Burning of fossil and biomass fuels, automobile exhaust gases, decaying organic substances and waste. Natural sources: volcanic eruptions, forest fires, dust storms, decaying organic waste. Man-made sources: exhaust gases from motorised equipment or vehicles, blast furnaces, thermal power stations, industries, and garbage disposal sites.
Water Pollution Waste such as wastewater, domestic waste including detergents and sewage, solid waste such as rubbish, and industrial waste such as grease. Agricultural chemicals such as chemical fertilisers and pesticides. Oil spills.
Land Pollution Excessive use of fertilisers and pesticides, inappropriate management of solid waste, acid rain, nuclear waste, and electronic waste.
Thermal Pollution Deforestation, industrial activities, and fuel combustion in vehicles or machines.

Steps to Make EM Mud Balls

Follow these steps to prepare Effective Microorganism mud balls for water purification.

  1. 1Pour 1.4 kg soil and 70 g EM Bokashi or rice bran into a basin and mix well.
  2. 2Add 500 cm³ of EM solution to the mixture and mix thoroughly.
  3. 3Roll the mixture into EM mud balls.
  4. 4Line the base of a tray with newspaper and place the EM mud balls in the tray.
  5. 5Keep the tray away from sunlight or strong winds to prevent balls from drying quickly.
  6. 6Mud balls are ready for use when their surface is covered with white fungi.

Try to Answer First

Answer in your mind, then press “Check Answer”.

1

What is meant by Biochemical Oxygen Demand (BOD)?

Answer: The amount of dissolved oxygen needed by microorganisms, such as bacteria, to decompose organic substances in a water resource.
2

What happens to the time taken for methylene blue solution to decolourise as the water pollution level increases?

Answer: The time taken for methylene blue solution to decolourise becomes shorter; it decolourises faster.
3

Name two types of microorganisms found in Effective Microorganism (EM) mud balls and state one role of each.

Answer: Lactic acid bacteria (Lactobacillus casei) treats sewage, eliminates foul odours, inhibits harmful microorganisms, or facilitates decay of organic substances. Photosynthetic bacteria (Rhodopseudomonas palustris) synthesises useful substances such as amino acids and sugars from organic substances for aquatic life. Alternatively, yeast (Saccharomyces cerevisiae) produces substances needed for the growth of green plants.

Common Mistakes

  • !Confusing the parameter for air pollution with water pollution: thinking API measures water pollution and BOD measures air pollution. API is for air; BOD is for water.
  • !Misinterpreting the methylene blue decolourisation time: mistakenly thinking that polluted water takes a longer time to decolourise methylene blue. In fact, high pollution means low oxygen, so methylene blue loses its colour faster.
  • !Neglecting the syringe safety precaution: injecting methylene blue above the water surface instead of placing the needle under the surface of the water, which allows atmospheric oxygen to enter and skew results.
  • !Confusing eutrophication causes: attributing eutrophication solely to toxic industrial chemicals rather than the accumulation of phosphate and nitrate ions from fertilisers, detergents, and sewage.

Concept Misunderstandings

Misconception

High BOD means the water has a lot of dissolved oxygen.

Correct Concept

High BOD means microorganisms demand a lot of oxygen because there is a lot of organic matter to decompose. As a result, the actual dissolved oxygen available in the water is very low.

Misconception

EM mud balls purify water using harsh chemical disinfectants.

Correct Concept

EM mud balls are a Green Technology method using beneficial living microorganisms, namely lactic acid bacteria, photosynthetic bacteria, and yeast, to naturally decompose pollutants and suppress harmful bacteria.

Summary

  • Environmental pollution encompasses unwanted physical, chemical, or biological changes in air, water, and soil, grouped into air, water, land, and thermal pollution.
  • Air pollution is monitored by the Air Pollutant Index (API), while water pollution is measured using Biochemical Oxygen Demand (BOD).
  • Eutrophication occurs when excess nitrates and phosphates cause rapid algal blooms, depleting dissolved oxygen and killing aquatic life.
  • Higher water pollution corresponds to higher BOD and lower dissolved oxygen, causing methylene blue solution to decolourise in a shorter period of time.
  • Contaminated water can be treated using Green Technology through EM mud balls, which contain lactic acid bacteria, photosynthetic bacteria, and yeast to restore water quality.

Short Activity

A. Objective Quiz

1 Which of the following correctly describes the relationship between the water pollution level, BOD, and the time taken for methylene blue solution to decolourise?

2 What is the primary role of lactic acid bacteria such as Lactobacillus casei in EM mud balls?

B. Fill in the Blanks

3 The ecosystem response towards an increase of phosphate ions and nitrate ions in an aquatic ecosystem that causes rapid algal growth is known as .

 

4 During the water test with methylene blue, the needle of the syringe must be placed the surface of the water sample when adding the solution.

 

C. Drag and Drop: Match Each Microorganism or Parameter to Its Function

Drag each item to the correct function or definition. On a phone, tap an answer first, then tap a matching box. Tap the Answer Choices area to return a selected item.

Concept / Microorganism
Lactobacillus casei
Rhodopseudomonas palustris
Saccharomyces cerevisiae
Biochemical Oxygen Demand
Function / Definition
1 Treats sewage, eliminates foul odour, and stunts the growth of dangerous microorganisms
2 Synthesises amino acids and sugars from organic substances for aquatic organisms
3 Yeast that produces substances needed for the growth of green plants
4 Amount of dissolved oxygen needed by microorganisms to decompose organic matter

C. Match Each Microorganism or Parameter to Its Function

Write the correct concept or microorganism next to each function or definition.

Function / Definition Concept / Microorganism
1. Treats sewage, eliminates foul odour, and stunts the growth of dangerous microorganisms  
2. Synthesises amino acids and sugars from organic substances for aquatic organisms  
3. Yeast that produces substances needed for the growth of green plants  
4. Amount of dissolved oxygen needed by microorganisms to decompose organic matter  

Answer choices: Lactobacillus casei • Rhodopseudomonas palustris • Saccharomyces cerevisiae • Biochemical Oxygen Demand

Keywords

Environmental pollution Thermal pollution Eutrophication Biochemical Oxygen Demand (BOD) Air Pollutant Index (API) Methylene blue solution Effective Microorganism (EM) mud balls
The views expressed in the notes here are those of the contributor and don’t necessarily represent the views of Pandai.
Chapter : Sustainiability of the Environment
Topic : Environmental Pollution
Form 5 Science
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