1. Human impact on the Environment
Pollution II: Water pollution

2. What is water pollution?
The pollution of water in the streams, rivers, lakes, and seas.
Pollutants

3. Water pollutants Agricultural: Domestic: Industrial: Others:
Manure, fertilizers, pesticides
Domestic:
Sewage, detergents, rubbish
Industrial:
Cyanides, heavy metals ions
Others:
Crude oil and lubricant oil, hot water

4. Group discussion Manure Fertilizers Pesticides Sewage Detergents
Rubbish
Cyanides
Heavy metals ions
Crude oil
Hot water
You have to find out:
Where does it from? (Sources)
What is its effects to the environment? (Effect)
How to minimize the problem? (Solutions)

5. Agricultural waste - Manure
Source: Animals faeces from farms
Effects: Increase organic nutrients in water  algae and bacteria to grow  oxygen content decrease  algae die and decomposed by bacteria  toxic substances and bad smell produces
Cause diseases such as dysentery 痢疾
Solutions: Law enforcement to band illegal discharge of animal faeces
Collect agricultural waste and treat

6. Agricultural waste - Fertilizers
Source: Excess fertilizers leak from the farmland
Effects: Increase inorganic nutrients in water  algae  oxygen content decrease  algae die and decomposed by bacteria  toxic substances and bad smell produces
Cause diseases
Solutions: Avoid using excess fertilizers or using those not easy being dissolved in water to avoid leakage

7. Agricultural waste - Pesticides
Source: washed from the farmland
Effects: causes death of animals and plants  increase number of bacteria for decomposition  toxic substances and bad smell produces
absorbed by animals or plants in the water  accumulate in its body  passed to another animals when being eaten  accumulate in the food chain and attain a higher level in higher trophic level  cause death of high predators
Solutions: avoid using man-made pesticides, using natural pesticides to minimize the effects

8. Domestic waste – wastes from man
Source: Faeces and urine from man
Effects: Increase organic nutrients in water  algae and bacteria to grow  oxygen content decrease  algae die and decomposed by bacteria  toxic substances and bad smell produces
Cause diseases
Solutions: Law enforcement to band illegal discharge of wastes
Treat waste water before discharged

9. Domestic waste - Detergents
Source: from domestic washing process
Effects: contains phosphates ions  promote algal growth in water  oxygen content decrease  algae died which promote the bacterial growth for decomposition  toxic substances and bad smell produces
Cause diseases
Solutions: treat waste water before discharged

10. Domestic waste - Rubbish
Source: dump from ships
Effects: bacteria grow on surface  produce bad smell and cause health problems
cause damage to the engine of the ships when passing by
Solutions: Law enforcement for dumping of rubbish into rivers and seas

11. Industrial waste - Cyanides
Source: from the industrial waste
Effects: highly toxic, only small amount can cause death of many animals and plants
contaminate drinking water and cause death to human
Solutions: Law enforcement to the industrial waste discharge
Collect industrial waste for chemical treatment before discharge

12. Industrial waste – heavy metal ions
Source: from electroplating factories
Effects: Algae absorb heavy metal ions  accumulate in algae  passes to animals when being eaten  accumulate in the food chain and attain a higher level in higher trophic level  cause death or problem of high predators, especially human
Solutions: Law enforcement to the industrial waste discharge
Collect industrial waste for chemical treatment before discharge

13. Crude oil and lubricant oil
Source: leakage from oil refineries and tankers; and illegal discharge of lubricant oil into river or sea
Effects: spread out in large area  prevent oxygen dissolve in water  cause death of plants and animals in water
stick onto feathers of water birds  make them difficult to fly and cause body heat loss  cause death of water birds
Solutions: Law enforcement to avoid illegal discharge of lubricant oil

14. Hot water Source: from cooling facilities of factories and power plant
Effects: Increase water temperature  lower solubility of oxygen in water  cause death of organisms in water because of suffocation
Solutions: Build the factories or power plant in area that are of less number of species of organisms, or shores with common species only to minimize the effect of biodiversity

15. Waste water treatment Divided into three main process:
Physical process – for large debris
Biological process – for organic matters
Chemical process – for inorganic matters
Unfortunately, most of the countries, including HK, only do the first two processes, but not the chemical process. Although the water look clean and clear, is it really clean??????

16. Physical process
Biological
process

17. Screening and filtering
Remove large debris from sewage

18. Sedimentation
Solid particles are settles down to the bottom forming sludge.

19. Fermentation
Organic matters in the sludge were broken down by anaerobic bacteria. Methane gas 沼氣 will be produced burn as fuel. The solid remains will dried and can be used as fertilizers.

20. Decomposition
Organic matters in the sewage will be decomposed by decomposers. The liquid will passed through filter before discharged to remove microorganisms.
Air is pumped into the sewage, supply oxygen to the decomposers