Transcript Water pollution

Human impact on the
Environment
Pollution II: Water pollution
1
What is water pollution?
The pollution of water
in the streams, rivers,
lakes, and seas.
Pollutants
2
Water pollutants
Agricultural:
Manure, fertilizers, pesticides
 Domestic:
Sewage, detergents, rubbish
Industrial:
Cyanides, heavy metals ions
Others:
Crude oil and lubricant oil, hot water
3
Group discussion
1.
2.
3.
4.
5.
Manure
Fertilizers
Pesticides
Sewage
Detergents
6. Rubbish
7. Cyanides
8. Heavy metals ions
9. Crude oil
10. 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)
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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 5
Agricultural waste - Fertilizers
Source:
Excess fertilizers
farmland
leak
from
the
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
6
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
7
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
8
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
9
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
10
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
11
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
12
Crude oil and lubricant oil
Source:
leakage from oil refineries and tankers;
and illegal discharge of lubricant oil
into river or sea
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
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Effects:
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
14
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??????
15
Physical process
Biological
process
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Screening and filtering
Remove large debris from sewage
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Sedimentation
Solid particles are settles down to the bottom
forming sludge.
18
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.
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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
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