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Water and Water Pollution. Chapter 11 Brian W, Kate H, Amanda K. Key Concepts. Why is water so important? How much water is available? How much water are we using? What causes water shortages and what can be done? What causes floods and how can they be avoided?

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water and water pollution

Water and Water Pollution

Chapter 11

Brian W, Kate H, Amanda K

key concepts
Key Concepts
  • Why is water so important?
  • How much water is available?
  • How much water are we using?
  • What causes water shortages and what can be done?
  • What causes floods and how can they be avoided?
  • Sources, types, and risks of water pollution
  • Preventing and reducing water pollution
  • Sustainable use of water resources
water conflicts in the middle east
Water shortages

Nile River

Jordan Basin- water short

Tigris and Euphrates rivers

Jordan, Syria, Palestine, and Israel competing for the water

Peacefully solving the problems

Water Conflicts in the Middle East

Fig. 11-1, p. 236

earth s water budget
Earth’s Water Budget

All water

Fresh water

Readily accessible fresh water

Groundwater

0.592%

Biota

0.0001%

Rivers

0.0001%

Lakes

0.007%

0.014%

Fresh water

2.6%

Atmospheric

water vapor

0.001%

Oceans and

saline lakes

97.4%

Ice caps

and glaciers

1.984%

Soil

moisture

0.005%

Fig. 11-2, p. 238

groundwater
Groundwater
  • Zone of saturation- under the ground, spaces between rocks and soil that fill with water
  • Water table- top of zone of saturation, falls in dry weather, rises in wet weather
  • Aquifers- porous, saturated layers of sand, gravel, or bedrock through which groundwater flows
  • Natural recharge- precipitation percolates downward through soil and rock which replenishes aquifers naturally
groundwater systems
Groundwater Systems

Unconfined Aquifer Recharge Area

Evaporation and transpiration

Evaporation

Precipitation

Confined

Recharge

Area

Runoff

Flowing

artesian well

Recharge

Unconfined

Aquifer

Stream

Well requiring a pump

Water

table

Lake

Infiltration

Infiltration

Unconfined aquifer

Less

permeable material

such as clay

Confined aquifer

Confiningimpermeable rock layer

Fig. 11-3, p. 239

use of water resources
Use of Water Resources
  • Runoff use: about 54%
  • Freshwater use-
    • 20% - industry
    • 10% - cities and residents
    • 70% - irrigation of 1/5 of the world’s cropland (40% of world food)
  • Domestic, agricultural, and industrial use
  • US freshwater resources- more than enough freshwater resources. East- energy, cooling and manufacturing. West- irrigation
water hot spots in western states
Water Hot Spots in Western States

Wash.

N.D.

Montana

Oregon

S.D.

Idaho

Wyoming

Neb.

Nevada

Colo.

Utah

Kansas

California

Oak.

N.M.

Texas

Highly likely conflict potential

Substantial conflict potential

Moderate conflict potential

Unmet rural water needs

Fig. 11-5, p. 240

freshwater shortages
Freshwater Shortages
  • Causes of water scarcity: dry climate and too many people
  • Stresses on world’s major river systems
  • 1 of 6 people have no regular access to clean water
  • Poverty hinders access to water
  • Hydrological poverty
stress on world s river basins
Stress on World’s River Basins

Europe

North America

Asia

Africa

South America

Australia

Stress

High

None

Fig. 11-6, p. 241

hydrological poverty
Hydrological Poverty
  • An increasing number of governments are gaining ownership of public water by hiring private companies to manage them.
  • In Cochabamba, Bolivia, 60% of the water is being lost through leaking pipes.
  • Two potential problems of privatized water systems:
    • Since they have an incentive to sell as much water as they can, they don’t conserve well.
    • Because of lack of money to pay water bills, poor will continue to be left out

Fig. 11-7, p. 241

increasing freshwater supplies
Increasing Freshwater Supplies
  • Building damns
  • Bringing in water from somewhere else
  • Withdrawing groundwater
  • Converting salt water to freshwater (desalinization)
  • Wasting less water
  • Importing food
tradeoffs of large dams and reservoirs
Tradeoffs of Large Dams and Reservoirs

Large losses

of water through

evaporation

Flooded land destroys forests or cropland and

displaces people

Migration and

spawning of

some fish are

disrupted

Downstream cropland and estuaries are deprived of nutrient-rich silt

Provides water

for year-round

irrigation of

cropland

Reservoir is useful for

recreation and fishing

Can produce

cheap electricity

(hydropower)

Downstream

flooding is

reduced

Fig. 11-8, p. 243

ecological services of rivers
Ecological Services of Rivers

N a t u r a l C a p i t a l

Ecological Services of Rivers

• Deliver nutrients to sea to help sustain

coastal fisheries

• Deposit silt that maintains deltas

• Purify water

• Renew and renourish wetlands

• Provide habitats for wildlife

Fig. 11-9, p. 243

california water project and central arizona project
California Water Project and Central Arizona Project

CALIFORNIA

NEVADA

Shasta Lake

UTAH

Oroville Dam and

Reservoir

Sacramento

River

Lake Tahoe

Feather

River

North Bay

Aqueduct

Sacramento

San Francisco

Hoover Dam

and Reservoir

(Lake Mead)

South Bay

Aqueduct

Fresno

San Joaquin Valley

San Luis Dam

and Reservoir

Colorado

River

Los Angeles

Aqueduct

California Aqueduct

ARIZONA

Colorado River

Aqueduct

Santa Barbara

Central Arizona

Project

Los Angeles

Phoenix

Salton Sea

San Diego

Tucson

Fig. 11-10, p. 244

MEXICO

aral sea disaster
Aral Sea Disaster
  • Large-scale water transfers in dry central Asia
  • Salinity
  • Wetland destruction and wildlife
  • Fish extinctions and fishing
  • Wind-blown salt
  • Water pollution
  • Climatic changes
  • Restoration efforts
shrinking aral sea
Shrinking Aral Sea

Fig. 11-11, p. 245

tradeoffs of withdrawing groundwater
Tradeoffs of Withdrawing Groundwater

Trade-Offs

Withdrawing Groundwater

Advantages

Disadvantages

Good source of water for

drinking and irrigation

Available year-round

Exists almost everywhere

Renewable if not over-

pumped or contaminated

No evaporation losses

Cheaper to extract than

most surface waters

Aquifier depletion from over-

pumping

Sinking of land (subsidence)

when water removed

Polluted aquifiers unusable

for decades or centuries

Saltwater intrusion into

drinking water supplies near

coastal areas

Reduced water flows into

streams, lakes, estuaries,

and wetlands

Increased cost, energy use,

and contamination from

deeper wells

Fig. 11-13, p. 246

aquifer depletion
Aquifer Depletion

Groundwater

Overdrafts:

High

Moderate

Minor or none

Fig. 11-14, p. 246

groundwater depletion
Groundwater Depletion

Solutions

Groundwater Depletion

Prevention

Control

Raise price of water to

discourage waste

Tax water pumped

from Wells near

surface water

Set and enforce

minimum stream flow

levels

Waste less water

Subsidize water

conservation

Ban new wells in

aquifiers near surface

waters

Buy and retire ground-

water withdrawal rights in

critical areas

Do not grow water-

intensive crops in dry

areas

Reduce birth rates

Fig. 11-16, p. 247

saltwater intrusion into coastal water wells groundwater depletion
Saltwater Intrusion into Coastal Water Wells- groundwater depletion

Well contaminated

with saltwater

Major irrigation

well

Water table

Sea Level

Saltwater

Fresh

groundwater

aquifer

Seafloor

Interface

Saltwater

Intrusion

Interface

Normal

Interface

Fig. 11-15, p. 247

desalination
Desalination
  • Removal of salts from ocean or brackish waters to produce useable water
  • Distillation method-heating salt water until it evaporates, leaves behind salts in solid form, and condenses as fresh water
  • Reverse osmosis method- pumping salt water at high pressure through a thin membrane with pores that allow water molecules, but not most dissolved salts, to pass through. High pressure is used to push fresh water out of salt water
  • Used in 120 countries
  • Major problems: high cost and a lot of brine wastes (contains salt and other minerals)
  • Research is needed
  • Significant desalination is practical only for wealthy and water-short countries and cities that can afford its high costs
reducing water waste
Reducing Water Waste
  • Benefits of water conservation- Reduce leakage and save water, Improve irrigation
  • Increase water prices (we charge too little), no government subsidies (provide irrigation water, electricity, and diesel fuel for farmers at below market prices), and water waste
  • Using less water in homes and businesses
major types of irrigation systems
Major Types of Irrigation Systems

Drip Irrigation

(efficiency 90-95%)

Above- or below-ground pipes or tubes deliver water to individual plant roots.

Gravity Flow

(efficiency 60% and 80% with surge valves)

Water usually comes from an aqueduct system or a nearby river.

Center Pivot

(efficiency 80% with low-pressure sprinkler and 90–95% with LEPA sprinkler)

Water usually pumped from underground and sprayed from mobile boom with sprinklers.

Fig. 11-17, p. 249

reducing irrigation water waste
Reducing Irrigation Water Waste

Solutions

Reducing Irrigation Water Waste

  • Lining canals bring water to irrigation ditches
  • Leveling fields with lasers
  • Irrigating at night to reduce evaporation
  • Using soil and satellite sensorsand computer systems to monitor soil moisture and add water only when necessary
  • Polyculture
  • Organic Farming
  • Growing water-efficient crops using drought-resistant and salt tolerant crops varieties
  • Irrigating with treated urban waste water
  • Importing water-intensive crops and meat

Fig. 11-18, p. 250

reducing water waste1
Reducing Water Waste

Solutions

Reducing Water Waste

  • Redesign manufacturing processes
  • Landscape yards with plants that require little water
  • Use drip irrigation
  • Fix water leaks
  • Use water meters and charge for all municipal water use
  • Use waterless composting toilets
  • Require water conservation in water-short cities
  • Use water-saving toilets, showerheads, and front-loading clothes washers
  • Collect and reuse household water to irrigate lawns and nonedible plants
  • Purify and reuse water for houses, apartments, and office buildings

Fig. 11-19, p. 250

using water more sustainably
Using Water More Sustainably
  • Blue revolution-
    • Using technology to irrigate crops more efficiently and to save water in industries and homes
    • Economic and political policies to remove subsidies that cause water to be under priced and wasted, while guaranteeing low prices for low-income consumers
    • Switch to new waste-treatment systems
    • Leave enough water in nature
    • Help by using and wasting less water
  • Cut waste
  • Raise water prices
  • Drier waste treatment
  • Preserve forests
  • Slow population growth
sustainable water use
Sustainable Water Use

Solutions

Sustainable Water Use

  • Not depleting aquifers
  • Preserving ecological health of aquatic systems
  • Preserving water quality
  • Integrated watershed management
  • Agreements among regions and countries sharing surface water resources
  • Outside party mediation of water disputes between nations
  • Marketing of water rights
  • Raising water prices
  • Wasting less water
  • Decreasing government subsides for supplying water
  • Increasing government subsides for reducing water waste
  • Slowing population growth

Fig. 11-20, p. 251

what can we do
What Can We Do?

What Can You Do?

Water Use and Waste

  • Use water-saving toilets, showerheads, and faucet aerators
  • Shower instead of taking baths, and take short showers.
  • Repair water leaks.
  • Turn off sink faucets while brushing teeth, shaving, or washing.
  • Wash only full loads of clothes or use the lowest possible water-level setting for smaller loads.
  • Wash a car from a bucket of soapy water, and use the hose for rinsing only.
  • If you use a commercial car wash, try to find one that recycles its water.
  • Replace your lawn with native plants that need little if any watering.
  • Water lawns and garden in the early morning or evening.
  • Use drip irrigation and mulch for gardens and flowerbeds.
  • Use recycled (gray) water for watering lawns and houseplants and for washing cars.

Fig. 11-21, p. 251

benefits of floodplains
Benefits of Floodplains
  • Floodplain- a flood happens when water in a stream overflows its normal channel and spills into the adjacent area
  • Highly productive wetlands
  • Provide natural flood and erosion control
  • Maintain high water quality
  • Recharge groundwater
  • Fertile soils
  • Nearby rivers for use and recreation
  • Flatlands for urbanization and farming
dangers of floodplains and floods
Dangers of Floodplains and Floods
  • Deadly and destructive (considered natural disaster)
  • Human activities worsen floods
  • Failing dams and water diversion
  • Bangladesh- One of the world’s most densely populated countries. Due to overpopulation in the Himalayan watershed, great floods are now occurring every 4 years instead of every 50 years because of deforestation, overgrazing, and unsustainable farming.
before and during a flood in st louis missouri
Before and During a Flood in St. Louis, Missouri

This image shows the negative effects of living on a flood plain.

Fig. 11-22, p. 252

reducing flood risks
Reducing Flood Risks
  • Channelization- straighten and deepen streams
  • Levees (floodwalls)- contain and speed up stream flow
  • Dams- storing water
  • Protect and restore wetlands- natural flood control
  • Identify and manage flood-prone areas
  • Precautionary approach- to think carefully about where we live
water pollution
Water Pollution
  • What is water pollution? Any chemical, biological, or physical change in water quality that harms living organisms or makes water unsuitable for desired uses
  • Point sources- discharge pollutants at specific locations
  • Nonpoint sources- scattered and diffuse and can’t be traced to any single site of discharge
  • Is the water safe to drink? 95% of people in developed countries have access to safe drinking water. According to the WHO, 1 in every 5 people on Earth don’t have access to clean drinking water. Every day 9300 people die from infectious diseases from contaminated water.
polluted streams
Polluted Streams
  • Factors influencing stream recovery from pollution
  • Oxygen sag curve
  • Importance of wastewater treatment plants- so you don’t put contaminated water back into streams, lakes, and bays
  • Improvements in quality of US streams- water pollution control laws in 1970 increased the amount of wastewater treatment plants in the US
  • Cuyahoga River of Ohio- Caught fire twice in a ten year span. Resulted in new laws prohibiting the discharge of industrial wastes into rivers
  • Effect of regulations in US- cleaner streams, loss of pollution
  • Problems with nonpoint, accidental and illegal releases- can’t really stop it easily
  • Problems in developing countries- Half of the world’s 500 rivers are heavily polluted, most of them going through developing countries. Only 10% of sewage from Chinese cities is treated.
pollution in streams oxygen sag curve
Pollution in Streams(Oxygen sag curve)

Normal clean water organisms

(trout, perch, bass,

mayfly, stonefly)

Trash fish

(carp, gar,

leeches)

Fish absent, fungi,

sludge worms,

bacteria

(anaerobic)

Trash fish

(carp, gar,

leeches)

Normal clean water organisms

(trout, perch, bass,

mayfly, stonefly)

8 ppm

Types of

organisms

8 ppm

Dissolved oxygen (ppm)

Biological oxygen

demand

Clean Zone

Recovery Zone

Septic Zone

Decomposition

Zone

Clean Zone

Fig. 11-24, p. 256

lake pollution
Lake Pollution
  • Dilution less effective than with streams
  • Stratification (layers in the lake) and relatively little flow hinder rapid dilution of pollutants
  • Lakes more vulnerable to pollutants than streams
  • How pollutants enter lakes- runoff from watersheds, farmland, animal feedlots, urban areas, mining sites, sewage
  • Eutrophication: name given to the natural nutrient enrichment of lakes mostly from runoff of plant nutrients such as nitrates and phosphates from surrounding land. In hot weather or drought the nutrient overload produces algae, creating green lakes.
  • Oligotrophic lake- low in nutrients (clear)
  • Eutrophic lake- green lakes
  • Cultural eutrophication- Human activities accelerate the input of plant nutrients.
  • Preventing or removing eutrophication
    • Advanced waste treatment to remove nitrates and phosphates
    • Ban or limit the use of phosphates in household detergents
    • Employ soil conservation and land use control to reduce nutrient runoff
oligotrophic and eutrophic lakes
Oligotrophic and Eutrophic Lakes

Oligotrophic (clear lakes)

Eutrophic (green lakes)

Fig. 11-25, p. 257

groundwater pollution causes and persistence
Groundwater Pollution: Causes and Persistence
  • Sources of groundwater pollution- oil spills, paint thinners, sewage, hazardous wastes injection wells, waste lagoons, landfills
  • Slow flowing: Groundwater flows so slowly (1 foot per day) that contaminants are not diluted and dispersed effectively.
  • Consequences of lower dissolved oxygen- dissolved oxygen helps decompose many contaminants
  • Fewer bacteria to decompose wastes
  • Cooler temperatures: slow down chemical reactions
  • “Degradable” and nondegradable wastes in groundwater
groundwater pollution
Groundwater Pollution

Polluted air

Hazardous waste injection well

Pesticides

and fertilizers

De-icing road salt

Coal strip mine runoff

Buried gasoline and solvent tank

Pumping well

Gasoline station

Water pumping well

Cesspool septic tank

Waste lagoon

Sewer

Landfill

Leakage from faulty casing

Accidental spills

Discharge

Unconfined freshwater aquifer

Confined aquifer

Confined freshwater aquifer

Groundwater flow

Fig. 11-26, p. 258

extent of groundwater pollution
Extent of Groundwater Pollution
  • Not much is known about groundwater pollution
  • Organic contaminants, including fuel leaks
  • Arsenic- contaminates drinking water that comes from underground wells
  • Protecting groundwater: Prevention is best
preventing and cleaning up pollution in groundwater
Preventing and Cleaning Up Pollution in Groundwater

Solutions

Groundwater Pollution

Prevention

Cleanup

Find substitutes for toxic chemicals

Pump to surface, clean, and return to aquifer (very expensive)

Keep toxic chemicals out of the environment

Install monitoring wells near

landfills and underground tanks

Inject microorganisms to clean up contamination (less expensive but still costly)

Require leak detectors on underground tanks

Ban hazardous waste disposal

in landfills and injection wells

Pump nanoparticles of inorganic compounds to remove pollutants (may be the cheapest, easiest, and most effective method but is still being developed)

Store harmful liquids in aboveground tanks with leak detection and collection systems

Fig. 11-27, p. 259

ocean pollution
Ocean Pollution
  • How much pollution can oceans tolerate? Oceans can dilute, disperse, and degrade large amounts of pollutants, especially in deep ocean areas
  • Ocean dumping controversies
    • Some scientists think that it is best to dump pollutants in deep water instead of burying them.
    • We don’t know enough about the ocean so we may not know the harmful effects in the long run
coastal water pollution
Coastal Water Pollution

Urban sprawl

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

Cities

Toxic metals and

oil from streets and

parking lots pollute

waters; sewage

adds nitrogen and

phosphorus.

Industry

Nitrogen oxides from autos and smokestacks; toxic

chemicals, and heavy

metals in effluents flow into bays and estuaries.

Constructionsites

Sediments are washed into waterways,

choking fish and plants, clouding

waters, and blocking sunlight.

Farms

Run off 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.

Healthy zone

Clear, oxygen-rich waters

promote growth of plankton

and sea grasses, and support fish.

Oxygen-depleted zone

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

Fig. 11-28, p. 260

oxygen depleted water in the gulf of mexico
Oxygen-depleted Water in the Gulf of Mexico

Mississippi

River Basin

Ohio

River

Mississippi

River

Missouri

River

LOUISIANA

Mississippi

River

Depleted Oxygen

Gulf of Mexico

Fig. 11-29, p. 261

chesapeake bay
Largest US estuary

Pollution “sink”

Oxygen depletion

Chesapeake Bay Program

Chesapeake Bay

Fig. 11-30, p. 261

effects of oil on ocean life
Effects of Oil on Ocean Life
  • Crude and refined petroleum- most oil pollution comes from human activities on land
  • Tanker accidents and blowouts
  • Exxon Valdez- tanker that spilled oil into Alaska’s Prince William Sound (waterway)
  • Volatile hydrocarbons kill larvae- hydrocarbons immediately kill aquatic organisms
  • Tar-like globs coat birds and marine mammals
  • Oil destroys insulation and buoyancy
  • Heavy oil sinks and kills bottom organisms
  • Coral reefs die
  • Slow recovery
  • Oil slicks ruin beaches
  • Limited effectiveness of clean up methods
preventing and cleaning up pollution in coastal waters
Preventing and Cleaning Up Pollution in Coastal Waters

Solutions

Coastal Water Pollution

Prevention

Cleanup

Reduce input of toxic pollutants

Improve oil-spill cleanup

capabilities

Separate sewage and storm lines

Ban dumping of wastes and sewage by maritime and cruise ships in coastal waters

Sprinkle nanoparticles over an oil or sewage spill to dissolve the oil or sewage without creating harmful byproducts

(still under development)

Ban ocean dumping of sludge and hazardous dredged material

Protect sensitive areas from development, oil drilling, and oil shipping

Require at least secondary

treatment of coastal sewage

Regulate coastal development

Use wetlands, solar-aquatic, or

other methods to treat sewage

Recycle used oil

Require double hulls for oil tankers

Fig. 11-31, p. 263

preventing nonpoint source pollution
Preventing Nonpoint Source Pollution
  • Mostly agricultural wastes
  • Use vegetation to reduce soil erosion
  • Reduce fertilizer use
  • Use plant buffer zones around fields
  • Integrated pest management: Only use pesticides when necessary
  • Use plant buffers around animal feedlots
  • Keep feedlots away from slopes, surface water and flood zones
laws for reducing point source pollution
Laws for Reducing Point Source Pollution
  • Clean Water Act (1972)
    • Sets standards for allowed levels of key water pollutants and requires polluters to get permits
  • Water Quality Act
    • Another effort to clean water in the US
  • Discharge trading controversies
    • Allow buildup of pollutants in areas where credits are bought
sewage treatment systems
Sewage Treatment Systems
  • Sewage treatment in rural and suburban areas
  • Septic tanks
  • Primary (physical) sewage treatment
  • Secondary (biological) sewage treatment
  • Urban sewage treatment (Clean Water Act)
  • Sewage treatment facilities in many cities fail to meet federal standards
  • Bleaching and disinfection- last step of water treatment
  • Disinfectants: chlorine, ozone, and ultraviolet radiation
typical septic tank system
Typical Septic Tank System

Septic tank with manhole (for cleanout)

Household

wastewater

Nonperforated pipe

Distribution box (optional)

Gravel or

crushed

stone

Drain

field

Vent pipe

Perforated pipe

Fig. 11-32, p. 264

primary and secondary sewage treatment
Primary and Secondary Sewage Treatment

Secondary

Primary

Chlorine

disinfection tank

Bar screen

Grit chamber

Settling tank

Aeration tank

Settling tank

To river, lake,

or ocean

Sludge

(kills bacteria)

Activated sludge

Raw sewage

from sewers

Air pump

Sludge digester

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

Sludge drying bed

Fig. 11-33, p. 265

improving sewage treatment
Improving Sewage Treatment
  • Systems that exclude hazardous wastes
  • Non-hazardous substitutes
  • Composting toilet systems
  • Working with nature to treat sewage
  • Using wetlands to treat sewage
ecological wastewater treatment
Ecological Wastewater Treatment

Plants clean the wastewater

Fig. 11-34, p. 265

should the clean water act be strengthened
Should the Clean Water Act be Strengthened?
  • Yes: environmentalists
  • No: farmers, libertarians, manufacturers, and developers
  • State and local officials want more discretion
  • How Would You Vote exercise
    • http://biology.brookscole.com/miller11
drinking water quality
Drinking Water Quality
  • Purification of urban drinking water- allowing water to sit for several days. Increases taste and clarity and allows matter to settle on the bottom
  • Purification of drinking water in developing countries- households receive strips of cloth for filtering cholera producing bacteria. Villages that have done this have cut the cholera cases in half
  • Bottled water- studies have shown that US bottled water is 240 times to 10000 times more expensive than tap water. 25% of bottled water is tap water.
reducing water pollution
Reducing Water Pollution

Solutions

Water Pollution

  • Prevent groundwater contamination
  • Greatly reduce nonpoint runoff
  • Reuse treated wastewater for irrigation
  • Find substitutes for toxic pollutants
  • Work with nature to treat sewage
  • Practice four R's of resource use (refuse, reduce, recycle, reuse)
  • Reduce resource waste
  • Reduce air pollution
  • Reduce poverty
  • Reduce birth rates

Fig. 11-35, p. 267

what can we do1
What Can We Do?

What Can You Do?

Water Pollution

  • Fertilize your garden and yard plants with manure or compost instead of commercial inorganic fertilizer.
  • Minimize your use of pesticides.
  • Never apply fertilizer or pesticides near a body of water.
  • Grow or buy organic foods.
  • Compost your food wastes.
  • Do not use water fresheners in toilets.
  • Do not flush unwanted medicines down the toilet.
  • Do not pour pesticides, paints, solvents, oil, antifreeze, or other products containing harmful chemicals down the drain or onto the ground.

Fig. 11-36, p. 268