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© Cengage Learning 2015

LIVING IN THE ENVIRONMENT, 18e G. TYLER MILLER • SCOTT E. SPOOLMAN


20 Water Pollution


• Spring and summer – huge inputs of nutrients from the Mississippi River basin

• Depletion of dissolved oxygen in the Gulf of Mexico’s bottom layer of water – Contains little marine life – Disrupts nitrogen cycle

Case Study: The Gulf of Mexico’s Annual Dead Zone


Fig. 20-1a, p. 544

Mississippi River Basin

Missouri River

Ohio River

Mississippi River

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Presentation Notes

Figure 20.1 Water containing sediments, dissolved nitrate fertilizers, and other pollutants drains from the Mississippi River basin (top) into the Mississippi River and from there into the northern Gulf of Mexico (bottom). The boxed area at the bottom of the map shows the dead zone with the red area having the lowest oxygen level.


Fig. 20-1b, p. 544

Mississippi River

GULF OF MEXICO

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Presentation Notes

Figure 20.1 Water containing sediments, dissolved nitrate fertilizers, and other pollutants drains from the Mississippi River basin (top) into the Mississippi River and from there into the northern Gulf of Mexico (bottom). The boxed area at the bottom of the map shows the dead zone with the red area having the lowest oxygen level.


• Water pollution causes illness and death in humans and other species, and disrupts ecosystems

• Sources: – Primarily agricultural activities, industrial

facilities, and mining – Growth of both the human population and our

rate of resource use makes it increasingly worse

20-1 What Are the Causes and Effects of Water Pollution?


• Water pollution – Change in water quality that can harm

organisms or make water unfit for human uses

• Point sources – Located at specific places – Easy to identify, monitor, and regulate

Water Pollution Comes from Point and Nonpoint Sources


• Nonpoint sources – Broad, diffuse areas – Difficult to identify and control – Expensive to clean up

Water Pollution Comes from Point and Nonpoint Sources (cont’d.)


• Leading causes of water pollution – Agriculture activities

• Sediment eroded from the lands • Fertilizers and pesticides

– Industrial facilities • Inorganic and organic chemicals

– Mining • Erosion and toxic chemicals

Water Pollution Comes from Point and Nonpoint Sources (cont’d.)

Fig. 20-2, p. 545

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Figure 20-2: This is a point source of water pollution in Gargas, France.


Fig. 20-3, p. 546

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Figure 20-3: Nonpoint sediment from farmland runoff flows into streams and sometimes changes their courses or dams them up. As measured by weight, it is the largest source of water pollution. Question: What do you think the owner of this farm could have done to prevent such sediment pollution?


• Infectious disease organisms – Contaminated drinking water – An estimated 1.6 million people die every

year, mostly under the age of five

Major Water Pollutants Have Harmful Effects


Table 20-1, p. 547

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Table 20-1


• Streams and rivers around the world are extensively polluted – However, they can cleanse themselves of

many pollutants if we do not overload them or reduce their flows

– Adding excessive nutrients to lakes from human activities can disrupt their ecosystems, and prevention of such pollution is more effective and less costly than cleaning it up

20-2 What Are the Major Water Pollution Problems in Streams and Lakes?


• Dilution • Biodegradation of wastes by bacteria

takes time • Oxygen sag curve

– Breakdown of biodegradable wastes by bacteria depletes oxygen

Streams Can Cleanse Themselves, If We Do Not Overload Them


Fig. 20-6, p. 549

Point source

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Presentation Notes

Animated Figure 20-6: Natural capital. A stream can dilute and decay degradable, oxygen-demanding wastes, and it can also dilute heated water. This figure shows the oxygen sag curve (blue) and the curve of oxygen demand (red). Streams recover from oxygen-demanding wastes and from the injection of heated water if they are given enough time and are not overloaded (Concept 20-2A). Question: What would be the effect of putting another discharge pipe emitting biodegradable waste to the right of the one in this picture?


• 1970s – water pollution control laws • Successful water clean-up stories

– Ohio Cuyahoga River, U.S. – Thames River, Great Britain

• Contamination of toxic inorganic and organic chemicals by industries and mines

Stream Pollution in More-Developed Countries


• Half of the world’s 500 major rivers are polluted – Untreated sewage – Industrial waste

• Water often used for human activities

Stream Pollution in Less-Developed Countries


Fig. 20-7, p. 550

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Figure 20-7: Natural capital degradation. This portion of China’s Yangtze River near the Three Gorges dam is heavily polluted with chemicals, sediment, and trash.


• Less effective at diluting pollutants than streams – Stratified layers

• Little vertical mixing

– Little of no water flow – Can take up to 100 years to change the water

in a lake – Biological magnification of pollutants

Too Little Mixing and Low Water Flow Makes Lakes Vulnerable to Water Pollution


• Eutrophication – Natural enrichment of a shallow lake, estuary,

or slow-moving stream – Caused by runoff into lake that contains

nitrates and phosphates • Oligotrophic lake

– Low nutrients; clear water

Cultural Eutrophication Is Too Much of a Good Thing


• Cultural eutrophication – Nitrates and phosphates from human sources – Farms, feedlots, streets, parking lots – Fertilized lawns, mining sites, sewage plants

• During hot weather or droughts – Algal blooms – Increased bacteria; anaerobic bacteria – More nutrients

Cultural Eutrophication Is Too Much of a Good Thing (cont’d.)


• Prevent or reduce cultural eutrophication – Remove nitrates and phosphates – Diversion of lake water

• Clean up lakes – Remove excess weeds – Use herbicides and algaecides – Pump in air

Cultural Eutrophication Is Too Much of a Good Thing (cont’d.)


Fig. 20-8, p. 551

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Figure 20-8: In 2010, severe cultural eutrophication affected Chaohu Lake near Hefei City in China’s Anhui Province.


• Nitrates discharged from the Mississippi have nearly tripled since 1950 – Nitrogen cycle disrupted – Blue-green algae blooms

• Flood-control along the Mississippi – Flow faster; increase sediment pollution

• Fish kills

Revisiting The Gulf of Mexico: An Extreme Case of Cultural Eutrophication


• 1960s – many areas with cultural eutrophication

• 1972 – Canada and the United States Great Lakes pollution control program – Decreased algal blooms – Increased dissolved oxygen – Increased fishing catches – Better sewage treatment plants

Case Study: Pollution in the Great Lakes


• Pollution control program (cont’d.) – Fewer industrial wastes – Bans on phosphate-containing household

products • Problems still exist

– Raw sewage and biological pollution – Nonpoint runoff of pesticides and fertilizers – Atmospheric deposition of pesticides and Hg

Case Study: Pollution in the Great Lakes (cont’d.)


• Continuing problems – Urban sprawl and runoff – Biological pollution

• Zebra mussels

– Atmospheric deposition of pollutants

Case Study: Pollution in the Great Lakes (cont’d.)


Fig. 20-11, p. 553

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Figure 20-11: The five Great Lakes of North America make up the world’s largest freshwater system. Dozens of major cities in the United States and Canada are located on their shores, and water pollution in the lakes is a growing problem.


• Chemicals used in agriculture, industry, transportation, and homes can spill and leak into groundwater and make it undrinkable – There are both simple ways and complex

ways to purify groundwater used as a source of drinking water, but protecting it through pollution prevention is the least expensive and most effective strategy

20-3 What Are the Major Pollution Problems Affecting Groundwater?


• Source of drinking water for about half of the U.S. population

• Common pollutants – Fertilizers and pesticides – Gasoline – Organic solvents – Fracking

• Pollutants dispersed in a widening plume

Ground Water Cannot Cleanse Itself Very Well


• Slower chemical reactions in groundwater due to: – Slow flow – contaminants not diluted – Less dissolved oxygen – Fewer decomposing bacteria – Low temperatures

Ground Water Cannot Cleanse Itself Very Well (cont’d.)


Fig. 20-12, p. 554

Polluted air

Hazardous waste

injection well Pesticides and fertilizers

Deicing road salt

Coal strip mine runoff

Buried gasoline and solvent tanks

Pumping well

Gasoline station

Cesspool, septic tank

Water pumping well Waste lagoon

Landfill Sewer

Accidental spills

Leakage from faulty casing

Discharge

Freshwater aquifer

Groundwater flow

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Presentation Notes

Figure 20-12: Natural capital degradation. Principal sources of groundwater contamination in the United States (Concept 20-3A). Another source in coastal areas is saltwater intrusion from excessive groundwater withdrawal. (Figure is not drawn to scale.) Question: What are three sources shown in this figure that might be affecting groundwater in your area?


• China – 90% of urban aquifers are contaminated or overexploited

• U.S. – FDA reports of toxins found in many aquifers

• Nitrate ions – Can turn into cancer causing chemicals

• Slowly degrading wastes • Non-degradable wastes

Groundwater Pollution Is a Serious Hidden Threat in Some Areas


• Rocks rich in arsenic can contaminate wells

• Long-term exposure can lead to: – Skin, lung, bladder cancer

• Treatment – Nanoparticles of rust

Case Study: Arsenic in Drinking Water


• Reservoirs and purification plants • Process sewer water to drinking water • Expose clear plastic containers to sunlight

(UV) • The LifeStraw • PUR – chlorine and iron sulfate powder

There Are Many Ways to Purify Drinking Water


• Bottled water can be useful but expensive • The U.S. has some of the world’s cleanest

drinking water • Bottled water less regulated than tap water • Use of bottled water can create

environmental problems

Case Study: Is Bottled Water a Good Option?


• 1974 – U.S. Safe Drinking Water Act – Sets maximum contaminant levels for any

pollutants that affect human health • Health scientists

– Strengthen the law • Water-polluting companies

– Weaken the law

Using Laws to Protect Drinking Water Quality


• Most ocean pollution originates on land and includes: – Oil and other toxic chemicals – Solid waste, which threaten fish and wildlife

and disrupt marine ecosystems • Key to protecting the oceans

– Reduce the flow of pollution from land and air and from streams emptying into ocean waters

20-4 What Are the Major Water Pollution Problems Affecting Oceans?


• Municipal sewage from less-developed countries are often dumped into oceans without treatment

• Deeper ocean waters – Dilution – Dispersion – Degradation

Ocean Pollution Is a Growing and Poorly Understood Problem


• U.S. coastal waters – Raw sewage – viruses – Sewage and agricultural runoff: NO3

- and PO4

3-

– Harmful algal blooms – Oxygen-depleted zones

Ocean Pollution Is a Growing and Poorly Understood Problem (cont’d.)

Fig. 20-15, p. 559

Industry Nitrogen oxides from autos and smokestacks, toxic chemicals, and heavy metals in effluents flow into bays and estuaries.

Cities Toxic metals and oil from streets and parking lots pollute waters; sewage adds nitrogen and phosphorus.

Urban sprawl Bacteria and viruses from sewers and septic tanks contaminate shellfish beds and close beaches; runoff of fertilizer from lawns adds nitrogen and phosphorus.

Construction sites Sediments are washed into waterways, choking fish and plants, clouding waters, and blocking sunlight.

Farms Runoff of pesticides, manure, and fertilizers adds toxins and excess nitrogen and phosphorus.

Red tides Excess nitrogen causes explosive growth of toxic microscopic algae, poisoning fish and marine mammals.

Closed shellfish beds

Closed beach

Oxygen-depleted zone

Toxic sediments Chemicals and toxic metals contaminate shellfish beds, kill spawning fish, and accumulate in the tissues of bottom feeders.

Oxygen-depleted zone Sedimentation and algae overgrowth reduce sunlight, kill beneficial sea grasses, use up oxygen, and degrade habitat.

Healthy zone Clear, oxygen-rich waters promote growth of plankton and sea grasses, and support fish.

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Presentation Notes

Figure 20-15: Natural capital degradation. Residential areas, factories, and farms all contribute to the pollution of coastal waters. Question: What do you think are the three worst pollution problems shown here? For each one, how does it affect two or more of the ecosystem and economic services listed in Figure 8-5?


• North Pacific Garbage Patch – Two rotating gyres – On or just beneath the water surface

• Tiny plastic pieces harmful to wildlife • No practical way to clean up

Case Study: Ocean Garbage Patches: There Is No Away


Fig. 20-17, p. 560

PACIFIC OCEAN

Hawaii

Russia Alaska United States

China

Japan

Canada

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Figure 20-17: The North Pacific Garbage Patch is actually two vast, slowly swirling masses of small plastic particles floating just under the water. Four other huge garbage patches have been discovered in the world’s other major oceans.


• Crude and refined petroleum – Highly disruptive pollutants

• Largest source of ocean oil pollution – Urban and industrial runoff from land

• 1989 – Exxon Valdez, oil tanker • 2010 – BP Deepwater Horizon in the Gulf

of Mexico

Ocean Pollution from Oil


• Volatile organic hydrocarbons – Kill many aquatic organisms

• Tar-like globs on the ocean’s surface – Coat animals

• Heavy oil components sink – Affect the bottom dwellers

Ocean Pollution from Oil (cont’d.)


• Faster recovery in warm water with rapid currents – In cold, calm waters recovery can take

decades • Methods of preventing oil spills

– Double hulls

Ocean Pollution from Oil (cont’d.)


Fig. 20-19, p. 561

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Figure 20-19: The Deepwater Horizon drilling platform burned and sank in the Gulf of Mexico after exploding on April 20, 2010.


• Spill from deep-sea oil drilling – 1 mile deep – Released 4.9 million barrels of crude oil – Contaminated vast areas of coastline – Caused by equipment failure and poor

decisions • Government developed new standards for

offshore drilling procedures

Case Study: The BP Deepwater Horizon Oil-Rig Spill


• Reducing water pollution requires that we: – Prevent it – Work with nature to treat sewage – Use natural resources far more efficiently

20-5 How Can We Deal with Water Pollution?


• Reduce flow of pollution from land – Land-use – Air pollution – Linked to energy and climate policy

Reducing Ocean Water Pollution


Fig. 20-21, p. 563

Coastal Water Pollution

Prevention Cleanup

Require secondary treatment of coastal sewage

Improve oil-spill cleanup capabilities

Separate sewage and storm water lines

Use nanoparticles on sewage and oil spills to dissolve the oil or sewage (still under development)

Ban dumping of wastes and sewage by ships in coastal waters

Strictly regulate coastal development, oil drilling, and oil shipping

Use wetlands and other natural methods to treat sewage

Require double hulls for oil tankers

Solutions

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Presentation Notes

Figure 20-21: Methods for preventing excessive pollution of coastal waters and methods for cleaning it up (Concept 20-4B). Question: Which two of these solutions do you think are the best ones? Why?


• Agriculture – Reduce erosion – Reduce the amount of fertilizers – Plant buffer zones of vegetation – Use organic farming techniques – Use pesticides prudently – Institute tougher pollution regulations for

livestock operations

Reducing Surface Water Pollution from Nonpoint Sources


• 1972 – Clean Water Act • 1987 – Water Quality Act • Experimenting with a discharge trading

policy that uses market forces • What are some achievements of the Clean

Water Act?

Case Study: The U.S. Experience with Reducing Point-Source Pollution


• How do septic tank systems work? • Wastewater or sewage treatment plants

– Primary sewage treatment • Physical process

– Secondary sewage treatment • Biological process with bacteria

– Tertiary or advance sewage treatment • Special filtering processes • Bleaching, chlorination

Sewage Treatment Reduces Water Pollution


• Many cities violate federal standards for sewage treatment plants – Federal law requires primary and secondary

treatment • Exemptions from secondary treatment

• There are health risks of swimming in water with blended sewage wastes

Sewage Treatment Reduces Water Pollution (cont’d.)


Fig. 20-23, p. 565

Manhole cover (for cleanout)

Septic tank Gas

Distribution box Scum

Wastewater Sludge

Drain field (gravel or crushed stone)

Vent pipe Perforated pipe

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Figure 20-23: Solutions. Septic tank systems are often used for disposal of domestic sewage and wastewater in rural and suburban areas.


Fig. 20-24, p. 566

Primary Secondary

Chlorine disinfection tank Bar screen Grit chamber Settling tank Aeration tank Settling tank

To river, lake, or ocean Raw sewage

from sewers

Sludge Activated sludge (kills bacteria)

Air pump

Sludge digester

Disposed of in landfill or ocean or applied to cropland, pasture, or rangeland

Sludge drying bed

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Presentation Notes

Figure 20-24: Solutions: Primary and secondary sewage treatment systems help to reduce water pollution. Question: What do you think should be done with the sludge produced by sewage treatment plants?


• Remove toxic wastes before water goes to the municipal sewage treatment plants

• Reduce or eliminate use and waste of toxic chemicals

• Use composting toilet systems • Wetland-based sewage treatment systems

– Work with nature

We Can Improve Conventional Sewage Treatment


• Developed countries – Bottom-up political pressure to pass laws

• Developing countries – Little has been done to reduce water pollution – China

• Small sewage treatment plants

• How can we avoid producing water pollutants in the first place?

There Are Sustainable Ways to Reduce and Prevent Water Pollution


Fig. 20-26, p. 568

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Figure 20-26: Ways to prevent or reduce water pollution (Concept 20-5). Question: Which two of these solutions do you think are the best ones? Why?


Fig. 20-27, p. 570

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Figure 20-27: Individuals matter. You can help reduce water pollution. Question: Which three of these steps do you think are the most important ones to take? Why?


• There are a number of ways to purify drinking water, but the most effective and least costly strategy is pollution prevention

• The key to protecting the oceans is to reduce the flow of pollution from: – Land and air – Streams emptying into ocean waters

Three Big Ideas


• Reducing water pollution requires that we: – Prevent it – Work with nature in treating sewage – Use natural resources far more efficiently

Three Big Ideas


• Dead zones disrupt ecological interactions between species in river and coastal systems

• We can use solar energy to purify water and reduce waste

• We can use natural nutrient cycles to purify water

Tying It All Together: Dead Zones and Sustainability

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