Water Pollution Chapter 20

1. Water PollutionChapter 20 Dave Sang Nora Tibbetts

2. 20-1 What are the Causes and Effects of Water Pollution?

3. Causes of Water Pollution • Water pollution - any chemical, biological, or physical change in water quality that harms living organisms or makes water unsuitable for desired uses. • Agricultural activities - leading cause • Industrial facilities • Mining • Parking lots • Widespread use of human-made materials (plastics, etc.) • Climate change as a result of global warming

4. Point Sources • Point sources - discharge pollutants at specific locations through drain pipes, ditches, or sewer lines into bodies of surface water. • Examples: factories, sewage treatment plants, underground mines, oil tankers • Located at specific places, and are easy to identify, monitor, and regulate. • Many developed countries have laws that help to control point-source pollution.

5. Nonpoint Sources • Nonpoint sources - are broad, and diffuse areas, rather than points, from which pollutants enter bodies of surface water or air. • Examples: runoff of chemicals and sediments from cropland, livestock feedlots, logged forests, urban streets, parking lots, lawns, golf courses • Difficult and expensive to identify and control such discharges, so not much progress has been made.

6. Effects of Water Pollution • Exposure to infectious disease organisms (pathogens) mostly through contaminated drinking water. • 3.2 million people die prematurely each year as a result of contaminated drinking water. • An average of 8,700 premature deaths a day.

7. 20-2What are the Major Water Pollution Problems in Streams and Lakes?

8. Water Pollution Problems in Streams • Streams can cleanse themselves if we do not overload them: • Undergo a natural recovery process • Can remove biodegradable wastes, but not slowly degradable and non-degradable pollutants • The breakdown of biodegradable wastes by bacteria depletes dissolved oxygen and creates an oxygen sag curve

9. Ohio’s Cuyahoga River • Water pollution control laws enacted in the 1970s have greatly increased the number and quality of waste water treatment plants in the United States and most other developed countries. • Extremely polluted with flammable chemicals. • Prompted by a highly publicized photo of the burning river in 1969, elected officials enacted laws that limited the discharge of industrial wastes into the river and into local sewage systems and provided funds to upgrade sewage treatment facilities. • Today, river is cleaner, no longer flammable, and highly used by boaters and anglers. • Successful use of bottom-up pressure by citizens.

11. India’s Ganges River • Viewed as a holy river. • Each day, large numbers of Hindus bathe, drink from, or take a dip in the river for religious reasons. • Highly polluted, yet 350 million people live in the Ganges River Basin. • Hindus believe in cremating the dead to free the soul and throwing the ashes into the river. • Indian government plans to build waste treatment plants to ease pollution.

13. Water Pollution Problems in Lakes • Generally less effective at diluting pollutants than streams are because: • Often contain stratified layers that undergo little vertical mixing • Have little or no flow • Very vulnerable to contamination by runoff • Contaminants can kill bottom life and fish and birds that feed on contaminated aquatic organisms.

14. Cultural Eutrophication • Cultural eutrophication - over nourishment of aquatic ecosystems with plant nutrients (mostly nitrates and phosphates) because of human activities such as agriculture, urbanization, and discharges from industrial plants and sewage treatment plants. • Produces dense growths or blooms of organisms like algae and cyanobacteria during hot weather or drought. • Reduce lake productivity. • 85% of the large lakes near major U.S. population centers have some degree of cultural eutrophication.

16. Prevention and Reduction of Cultural Eutrophication • Luckily, lakes can usually recover from cultural eutrophication. • Use advanced (and expensive) waste treatment to remove nitrates and phosphates before wastewater enters lakes. • Mechanically remove excess weeds. • Control undesirable plant growth with herbicides and algicides. • Pump air through lakes and reservoirs to prevent oxygen depletion.

17. 20-3What are the Major Pollution Problems Affecting Groundwater and Other Drinking Water Sources?

18. Major Pollution Problems Affecting Groundwater • Common pollutants can seep into groundwater from numerous sources. • Contaminates are not diluted and dispersed effectively. • Much lower concentrations of dissolved oxygen and smaller populations of decomposing bacteria. • The cold temperatures of groundwater slow down chemical reactions that decompose wastes. • Can take decades to thousands of years for contaminated groundwater to cleanse itself of slowly degradable wastes (like DDT). On a human time scale, non degradable wastes (like toxic lead and arsenic) remain in the water permanently.

19. Protecting Groundwater • Treating a contaminated aquifer involves eliminating the source of pollution and drilling monitoring wells to determine how far, in what direction, and how fast the contaminated plume is moving. • A computer model is used to project future dispersion of the contaminant in the aquifer. • Develop and implement a strategy to clean up the contamination. • Preventing contamination is the least expensive and most effective way to protect groundwater sources

20. Purifying Drinking Water • Complex Techniques: • Is usually stored in a reservoir and treated in a purification plant in developed countries. • Countries like Japan are developing plants that process sewer water into drinking water. • El Paso, Texas: 40% of drinking water comes from recycling and purifying waste water. • Orange Country, California: completed the world’s largest plant devoted to making sewer water as pure as distilled water • Simple Techniques: • Exposing a clear plastic bottle filled with contaminated water to intense sunlight • Nanofilters to clean contaminated water • LifeStraw

22. Laws Protecting Drinking Water Quality • U.S. Safe Drinking Water Act of 1974 - requires the EPA to establish national drinking water standards, called maximum contaminant levels, for any pollutants that may have adverse effects on human health. • Despite this, the UN estimates that 5.6 million Americans drink water that does not meet EPA standards. • Health scientists call for strengthening the U.S. Safe Drink Water Act

23. Is Bottled Water the Answer? • Between 1976 and 2006, average bottled water consumption per person in the US increased from 7.5 liters (2 gallons) to 113 liters (30 gallons) a year. • About one-fourth of it is ordinary tap water in a bottle. • Bacteria or fungi contaminate about 40% of bottled water. • Many bottles are thrown away without being recycled. • Manufacture of plastic water bottles emits toxic gases and liquids. • Greenhouse gases and other air pollutants are emitted by the fossil fuels burned to make and to deliver bottled water to suppliers.

24. 20-4What are the Major Water Pollution Problems Affecting Oceans?

25. Ocean Pollution is growing and poorly understood • About 40% world population lives on coasts • That population will double by 2050 • Ocean pollution has a large effect • 85% of sewage in developing countries is dumped untreated into oceans • Cruise ships also dump tons of waste into oceans • This pollution creates and spreads disease • Runoffs release nitrates and phosphates into the water, creating algae blooms • Algae blooms deplete oxygen and kill ocean animals • They also poison seafood, harming humans

26. Northern Gulf of Mexico • Collects agricultural runoff for 31 states • Has large zone of depleted oxygen due to eutriphication • Many attempts to reduce size • All failed, and zone is still growing • Scientists fear soon it will be uninhabitable

27. Ocean Oil is a Serious Problem • Oil spills and blowouts spew large amounts of oil into the ocean • Costly to clean up • Most oil pollution comes from leaks from urban runoff • Oil immediately kills many larvae • Oil stuck of birds causes them to drown • Recovery from refined oil usually take triple the time as crude oil • Oil slicks on beaches can destroy fishing and tourist economies • Oil spills can be mechanically cleaned up (booms/skimmers), but only about 15% effective • Preventing pollution is the most important goal (double hull)

28. 20-5How Can We Best Deal with Water Pollution?

29. We Need to Reduce Surface Water Pollution from Nonpoint Sources • Farmers keep soil vegetated to prevent erosion • Use slow release fertilizer and use buffers to prevent runoff • Use manure for fertilizer • Use less pesticides and use IPM

30. Laws can Help Reduce Water Pollution from Point Sources • Federal Pollution Control Act • Clean Water Act • Water Quality Act • Sets standards for pollutant limits • EPA : discharge traing policy • Buy credits from other permit holders • Would require heavy scrutiny and gradual lowering of caps • Neither is currently in the policy

31. Success and Failures of Clean Water Act • Annual wetland loss decreased 80% since 1992 • Swimmable US streams increased from 36 to 60% • US population served by sewage treatment increased from 32 to 74% • Number of American getting good water increased from 79 to 94% • 40% of streams still too polluted for fishing • Tens of thousands of gas tanks are leaking • Environmentalist want more preventive policies • Very costly to keep testing amounts of water pollution

32. Sewage Treatment Reduces Water Pollution • 25% of US homes use septic tanks • Home wastewater is pumped into the tank • Soil and bacteria are used to treat the water • When the tank fills every few years, it must be pumped into a tank truck • If not maintained, they can cause sewage to back up and

33. Sewage treatment plants • Sewer pipes bring wastewater to plants • Primary sewage treatment: Physically removes suspended solids with screens/filters • Secondary: Biologically removes dissolved wastes • Tertiary: Uses specialized processes to remove specific pollutants. Very costly • Chlorination: removes disease before discharging • Storm waters can overflow sewer systems and cause sewage discharge • Better to have separate pipe networks

34. We Can Improve Conventional Sewage Treatment • Composting Toilet Systems • Convert human feces into fertilizer supplement • Cheap, saves water, and saves energy

35. Wetland Based Sewage Treatment • Series of tanks to purify water • Algae decompose organic waste • Plants take up resulting nutrients • Passes through marsh to filter out more organic waste • Some plants can remove toxins and kill pathogens • Flows into aquarium where microorganisms eaten by snails, which are eaten by larger fish • Fish can be sold as bait or food • Water goes into second marsh for more cleansing • Water can be treated drinkable using UV light • Water is then discharged • Costs as much as conventional sewage plant