Intro: over 70% of the earth is covered by water, and it is undoubted, the most essential materials for lives.

1. Water Pollution Intro: over 70% of the earth is covered by water, and it is undoubted, the most essential materials for lives.

2. What is water pollution? • Water pollution occurs when a body of water is adversely affected due to the addition of large amounts of materials to the water. That mean….not PURE!

3. Point and non-point sources • Point: direct emitted of harmful substances to water • Non-point: indirect emission through environmental change e.g. leech of fertilizer by rain water. • *non-point sources are more difficult to control

4. Major sources • major sources of water pollution can be classified as • Municipal • Industrial • Agricultural

5. Municipal water pollution • Municipal water pollution consists of waste water from homes and commercial establishments

6. Industrial water pollution • Biochemical oxygen demand and the amount of suspended solids, but also on their content of specific inorganic and organic substances.

7. Agricultural water pollution • Commercial livestock and poultry farming, is the source of many organic and inorganic pollutants in surface waters and groundwater • Sediment from cropland soil erosion, phosphorus, nitrogen in animal wastes and commercial fertilizers. Animal wastes may contain pathogenic organisms.

8. Cause of water pollution include in three major sources • Sewage from sinks, toilets, and industrial processes • Fertilizers • Petroleum • Radioactive substances (uranium and thorium) • Heat

9. Sewage • Discharge of waste water • Effect: • Dissolved oxygen content decrease • Total suspended solid contents increase • Phosphate, nitrate content increase • pH changes rapidly • Eutrophication (suffocate of organisms) • Spreading of pathogens

10. Fertilizers • Leech and runoff of organic (chemical) fertilizers into groundwater, stream • Effect: • Clogging, blocking of rivers • Phosphate, nitrate content increase • Eutrophication

11. Petroleum • Oil spills • Off-shore drilling operations • Effect: • Flammable • Carcinogenic • Sticky, trap feather of sea bird, die by rapid heat loss

12. Radioactive substances • Waste from nuclear power plants • Industrial, medical, and scientific use of radioactive materials • Effect: • Carcinogenic (damage in genetic material)

13. Discharge of cooling water by factories and power plants Effect: Increased temperatures can kill aquatic organisms as it decrease dissolved oxygen contents Heat

14. Why water need to be treated before discharge? • 95% of all fresh water on earth is ground water, and we all rely on freshwater • Contaminated water may cause death of the aquatic organisms, disturb food web and thus natural resources

15. Prevention and Treatment in municipal • Treating municipal wastewater is to reduce: • Content of suspended solids • Oxygen-demanding materials • Dissolved inorganic compounds • Harmful bacteria • *99 percent of solids are removed by treatment plant!

16. Three stages • Primary treatment: grit (砂礫) removal, screening, grinding, sedimentation • Secondary treatment: oxidation of dissolved organic matter by biologically active sludge (bacteria) then filtered off • Tertiary treatment: nitrogen removal by chemical and physical methods e.g. granular filtration and activated carbon absorption

18. Prevention and Control in industrials • Control can take place at the point of generation in the plant • Wastewater can be pretreated for discharge to municipal treatment sources • Wastewater can be treated completely at the plant and either reused or discharged directly into receiving waters.

19. Prevention and Control in agricultural • Control may involve settling basins (食物盆) for liquids • Biological treatment in aerobic or anaerobic lagoons(化糞池) • Manage animal waste to minimize contamination of surface water and ground water (like above) • Protect drinking water by using less pesticides and fertilizers

20. Reduce soil erosion by using conservation practices and other applicable best management practices • Use planned grazing systems on pasture and rangeland • Dispose of pesticides, containers, and tank rinsate in an approved manner.

21. Legislations • Clean Water Act in U.S.A. in 1970 • Control water quality in waste water in industrial, charge for treating sewage in Hong Kong

22. Other measurements which can be done by us • Urban : • Keep litter, pet wastes, leaves, and debris out of street gutters and drains • Apply garden chemicals sparingly (節儉地)and according to directions • Properly dispose of used oil, antifreeze, paints, household chemicals, do not hose them into the street

23. Control soil erosion on your property by planting ground cover and stabilizing erosion-prone (高危) areas. • Encourage local government officials to develop construction erosion/sediment control ordinances in your community. • Encouragelocal government establish a program for collecting household hazardous wastes

24. Forestry • Use proper logging and erosion control practices on forest lands by ensuring proper construction, maintenance, and closure of logging roads and skid trails. • Report questionable logging practices to state and federal (美國聯邦政府的) forestry and state water quality agencies (here can be Environmental Protection Department in Hong Kong)