Transcript Water and Its Pollution Lecture 9

Lecture 9
Water and Its Pollution
A Glimpse Into Water’s Unique
Properties
Liquid water dissolves a variety of compounds
-
known as the universal solvent
-
is easily polluted by water-soluble
wastes
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in living organisms: carry dissolved
nutrients; flush waste products
Main Uses of Water
1. Domestic Use
domestic and municipal use account for
6 - 8% of worldwide withdrawals
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improved water supply helps reduce
diseases
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humans are approx. 70% water
Main Uses of Water cont’d
2. Industrial Use
worldwide withdrawals of water for
energy production & industrial
processing is ~ 23%
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most water is used for cooling &
cleaning
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it takes 100,000 gallons (380,000 litres)
to make an automobile
Main Uses of Water cont’d
3. Agricultural Use
consumes the greatest quantity of fresh
water
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globally ~ 69% of the water withdrawn
is used for irrigation
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irrigation water efficiency is < 30%
Main Uses of Water cont’d
4. Transport
- use of seas and rivers
- e.g., river barges, freight ships
Main Uses of Water cont’d
5. Recreation / Tourism
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use of seas and rivers
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e.g., rafting, canoeing, snorkeling,
swimming, river-boat casinos, scuba
diving, cruise ships
WHERE IS OUR WATER STORED?
Watershed
- also called drainage basin or catchment area
- areas of land that drain into bodies of water
Surface Water
- precipitation that does not soak into the
ground or return to the atmosphere
- forms streams, lakes, wetlands
Surface Runoff
- water flowing off the land into bodies of
surface water
Groundwater
- water that sinks into the soil and is stored in
slow flowing and slowly renewed
underground reservoirs
-
underground water
Groundwater Pollution
- groundwater is easy to deplete and pollute
because it is renewed very slowly
- pesticides and nitrates are the most common
contaminants
- pollution is caused from: landfills, underground
storage tanks, hazardous waste dumps, leaking
underground sewers, industrial-waste storage
lagoons e.g. red mud lakes
Water Pollution
Water is becoming scarce in some parts of the world
& its quality is being degraded.
8 Principal Water Pollutants
1. Sediment
2. Inorganic Plant Nutrients
3. Pathogens
4. Organic Chemicals
5. Inorganic Chemicals
6. Radioactive Chemicals
7. Thermal Pollution
8. Sewage
1. Sediment (or suspended matter)
- insoluble particles of soil and other solids that are
suspended in water
- occurs mostly when soil is eroded from land
- biggest water pollutant
- clouds water
(lowers rate of photosynthesis)
2.
Inorganic Plant Nutrients
(excess nutrients)
- come from soil erosion and human & animal
waste
- water-soluble nitrates and phosphates can cause
excessive growth of algae
- causes eutrophication:
 over-nourishment of aquatic ecosystems with
plant nutrients
3.
Pathogens (disease-causing agents)
- from sewage and livestock wastes
- include disease-causing bacteria, parasitic worms,
protozoa and viruses
- greatest cause of sickness and death in LDCs
4. Organic Chemicals / Compounds
- include oil, gasoline, plastics, pesticides, cleaning
solvents, detergents
- threaten human health
- harm aquatic life
5. Inorganic Chemicals
- consist of acids, salts & compounds of toxic
chemicals, e.g., mercury, lead
- high levels can:
· make water unfit to drink
· harm aquatic life
· depress crop yields
· accelerate corrosion of equipment
6. Radioactive Chemicals
- can cause birth defects, cancer, genetic damage
- capable of being biologically amplified to higher
concentrations as they pass through food webs
- e.g.
DDT (Dichloro-Diphenyl-Trichloroethane)
PCBs (Polychlorinated Biphenyls)
7. Thermal Pollution
- is an increase in water temperature that has
harmful effects on aquatic life
- generally caused by heat that is absorbed by
water used to cool electric power plants
- water temperature increase lowers oxygen content
- aquatic organisms more vulnerable to disease
8. Sewage & other oxygen demanding wastes
- organic wastes that an be decomposed by aerobic
bacteria
- can lead to depletion of oxygen and death of
aquatic life
Sources of Water Pollution
Point Source
- single, identifiable source that discharges
pollutants into the environment
- e.g., the drainpipe of a meat packing plant
Sources of Water Pollution cont’d
Non-point Source
- large or dispersed land areas, e.g., crop fields,
streets & lawns, that discharge pollutants into the
environment over a large area
MAIN SOURCES OF WATER
POLLUTION
• Agriculture
• Municipal Waste
• Industrial Waste
AQUATIC ECOSYSTEMS
UNDER THREAT
Coral Reefs
- the most threatened ecosystem in the coastal
zone
- greatest threats come from eroded soil
produced by:
deforestation
construction
agriculture
poor land management
Wetlands
- under severe human attack
- cut & converted to wood chips
- cut and drained for farmland & aquaculture
ponds
- drained & dumped up for housing development
Oceans
- covers > 70% of Earth’s surface
- water evaporates as part of the water cycle
- mix and dilute many human-produced wastes to
less harmful levels, if they are not overloaded
- affected by oil pollution
Sustainable Use of Water
•
Conservation
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Recycling
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Rainwater harvesting
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Efficient sewage treatment
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Proper solid waste disposal
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Soil conservation
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Population control