Water and Its Pollution

1. Water and Its Pollution Lecture 9

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 6 - 8% 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 Agricultural Use - consumes the greatest quantity of fresh water - globally ~ 69% of the water withdrawn is used for irrigation - irrigation water efficiency is 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 notsoak into the ground or return to the atmosphere - forms streams, lakes, wetlands

9. Surface Runoff - water flowingoff 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 & animalwaste • 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, identifiablesource 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 & dumpedup 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