3.2 Environmental Pollution

Types and Sources of Environmental Pollution

• Environmental pollution refers to unwanted changes in the physical, chemical or biological characteristics of environmental components, that is, air, water and soil.
• It causes harm and discomfort to all life forms and environmental issues such as flash floods.

Air pollution

• Natural sources: volcanic eruptions, forest fires, dust storms and decaying organic waste.
• Man-made sources: burning of fossil fuels and biomass; exhaust gases from motorised equipment or vehicles; blast furnaces; thermal power stations; industries; and garbage disposal sites.
• Burning fossil fuels or biomass and the decay of organic substances or waste release greenhouse gases and toxic gases such as sulphur dioxide.

Water pollution

• Wastewater and domestic waste such as detergents and sewage.
• Solid waste such as rubbish.
• 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.
• Electronic waste.

Thermal pollution

• Deforestation.
• Industrial activities.
• Fuel combustion in vehicles or machines.

Level of Water Pollution from Domestic Waste

• Air Pollutant Index (API) is an air pollution parameter measured to determine the air pollution level.
• Biochemical Oxygen Demand (BOD) is a water pollution parameter measured to determine the water pollution level.
• Eutrophication is the response of an ecosystem to an increase of phosphate ions and nitrate ions from detergents, fertilisers and garbage in an aquatic ecosystem.
• Excess nitrate ions cause rapid algal growth.
• Eutrophication reduces the oxygen content in water and can cause 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:
  • more microorganisms are present;
  • more dissolved oxygen is needed for decomposition;
  • the water pollution level is higher.

Activity 3.5 — Determining water pollution level

• Aim: Determine the water pollution level in different water samples.
• Materials: 0.1% methylene blue solution and 200 cm³ each of tap water, river water, distilled water and pond water.
• Apparatus: Four reagent bottles with covers, syringe, watch and measuring cylinder.

Method

1. Fill reagent bottles A–D with 200 cm³ of tap water, river water, distilled water and pond water respectively.
2. Use a syringe to add 1 cm³ of 0.1% methylene blue solution to each bottle; keep the syringe needle below the water surface while adding it.
3. Close all bottles and keep them in a dark cupboard.
4. Observe every 30 minutes and record the time taken for the blue colour to decolourise.

Interpretation

• A shorter decolourisation time indicates a lower amount of dissolved oxygen in the sample.
• In polluted water with little dissolved oxygen, methylene blue decolourises rapidly.
• Higher pollution level → shorter decolourisation time.
• The most polluted sample is the one in which methylene blue decolourises in the shortest time.
• Distilled water should show the longest time or no decolourisation during the activity because it contains the least organic matter and fewest microorganisms.

Purification of Contaminated Water Using Green Technology

• Effective microorganism mud balls (EM mud balls) are a Green Technology method used to treat polluted rivers in Malaysia.
• Effective microorganisms comprise three types:
  • Yeast, Saccharomyces cerevisiae: produces substances needed for the growth of green plants.
  • Lactic acid bacteria, Lactobacillus casei: treats sewage, eliminates foul odour in water, stunts the growth of dangerous microorganisms and facilitates the decay of organic substances.
  • Photosynthetic bacteria, Rhodopseudomonas palustris: use organic substances to synthesise useful substances such as amino acid and sugar for aquatic animals and plants to feed on.

Activity 3.6 — Making EM mud balls

• Materials for 10 mud balls: 1.4 kg soil, 70 g EM Bokashi or rice bran, 500 cm³ EM solution and newspaper.
• Apparatus: Tray, watering can and basin.

1. Pour the soil and EM Bokashi into a basin and mix well.
2. Add the EM solution and mix thoroughly.
3. Roll the mixture into EM mud balls.
4. Line a tray with newspaper and place the mud balls on it.
5. Keep the tray away from sunlight and strong winds to prevent rapid drying.
6. Use the mud balls when their surfaces are covered with white fungi.
7. Place the EM mud balls in a polluted water resource for treatment.