1. Water and Its Pollution
Lecture 9
Water and Its Pollution

2. 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
- in living organisms: carry dissolved nutrients; flush waste products

3. Main Uses of Water Domestic Use
- domestic and municipal use account for % of worldwide withdrawals
- improved water supply helps reduce diseases
- humans are approx. 70% water

4. Main Uses of Water cont’d
2. Industrial Use
- worldwide withdrawals of water for energy production & industrial processing is ~ 23%
- most water is used for cooling & cleaning
- it takes 100,000 gallons (380,000 litres) to make an automobile

5. Main Uses of Water cont’d
3. Agricultural Use
- consumes the greatest quantity of fresh water
- globally ~ 69% of the water withdrawn is used for irrigation
- irrigation water efficiency is < 30%

6. Main Uses of Water cont’d
4. Transport
- use of seas and rivers
- e.g., river barges, freight ships

7. Main Uses of Water cont’d
5. Recreation / Tourism
- use of seas and rivers
- e.g., rafting, canoeing, snorkeling, swimming, river-boat casinos, scuba diving, cruise ships

8. 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

9. 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

10. 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

11. Water Pollution
Water is becoming scarce in some parts of the world & its quality is being degraded.

12. 8 Principal Water Pollutants
Sediment
Inorganic Plant Nutrients
Pathogens
Organic Chemicals
Inorganic Chemicals
Radioactive Chemicals
Thermal Pollution
Sewage

13. 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)

14. 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

15. 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

16. 4. Organic Chemicals / Compounds
- include oil, gasoline, plastics, pesticides, cleaning solvents, detergents
- threaten human health
harm aquatic life

17. 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

18. 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)

19. 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

20. 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

21. Sources of Water Pollution
Point Source
- single, identifiable source that discharges pollutants into the environment
- e.g., the drainpipe of a meat packing plant

22. 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

23. MAIN SOURCES OF WATER POLLUTION
Agriculture
Municipal Waste
Industrial Waste

24. AQUATIC ECOSYSTEMS UNDER THREAT

25. Coral Reefs the most threatened ecosystem in the coastal zone
greatest threats come from eroded soil
produced by: deforestation
construction
agriculture
poor land management

26. Wetlands under severe human attack cut & converted to wood chips
cut and drained for farmland & aquaculture ponds
drained & dumped up for housing development

27. 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

29. Sustainable Use of Water
Conservation
Recycling
Rainwater harvesting
Efficient sewage treatment
Proper solid waste disposal
Soil conservation
Population control