CHAPTER 21 Water Pollution: Sustainably Managing

The Endangered GlobalCommonsThe Effects of Climate and Topography on AirPollutionThe Effects of AirPollutionAir Pollution Control:Toward a SustainableStrategyNoise: The ForgottenPollutantIndoor Air PollutionSpotlight on SustainableDevelopment 20-1:Germany's SustainableApproach Pays HugeDividends

20.1

20.1

20.1

20.1

20.1

20.1

20.1

CHAPTER OUTLINE

CHAPTER 21

CHAPTER 21Author Loren Eiseley once wrote, “If there is magic in this planet,

it is in water.” Water has a practical side, too. Water covers 70%of the Earth’s surface and makes up two-thirds or more of the

weight of most animals and up to 95% of the weight of plants. It playsan important role in metabolism, the chemical reactions in the cells ofthe bodies of all organisms. It is vital to agriculture and industry, too.Despite its crucial role in our lives, water is one of the most badlyabused resources. Chapter 13, for example, described unsustainablewithdrawals of groundwater and surface water. Chapter 13 also showedhow pollution of estuaries was destroying food sources for humans andother species. This chapter covers water pollution: where it comes

Water Pollution:Sustainably Managing a Renewable ResourceSurface Water Pollution

Groundwater PollutionOcean PollutionWater Pollution ControlSpotlight on SustainableDevelopment 21-1:Cleaning Up the GreatLakes

21.4

21.3

21.2

21.1

It is a crime to catch a fish in some lakes, and a miracle inothers.

—Evan Esar

468

Sources of Water PollutionLike air pollutants, water pollutants come from numeroussources, both natural and anthropogenic. As a rule, anthro-pogenic sources are the most important because they tend tobe localized and thus contribute significantly to the deterio-ration of local waterways or groundwater required by humans.

Like air pollutants, water pollutants respect no bound-aries. Pollutants produced in one city, for example, may af-fect water quality in another city located downstream. Theymay even flow from one country to another, ending up in thewater supply of downstream neighbors, or they may flowinto oceans and seas. For example, for many years the rivers flowing into theMediterranean Sea and thesea itself were viewed as aconvenient dump for do-mestic and industrial wastes.Along Italy’s coast, the waters became a cesspool. Fortu-nately, internal actions and negotiations among the nationsthat border the Mediterranean have spawned a region-wideplan that is successfully reversing the years of decline.

Pollutants also enter surface waters from the air andsurrounding land. This problem is called cross-media con-tamination and refers specifically to the movement of a pol-lutant from one medium (such as air) to another (such aswater). Pesticides sprayed on crops, for example, may evap-orate, becoming airborne. They may then be transported inthe air to nearby lakes. They may then flow to the oceans.Volatile organic chemicals from factories may evaporate andlater be washed out of the sky by rains.

KEY CONCEPTS

Point and Nonpoint SourcesWhen we ponder the sources of water pollution, we gener-ally think of factories, power plants, mines, oil wells, andsewage treatment plants that release tons of potentially toxicchemicals into sewers and lakes and rivers (FIGURE 21-1a).These point sources, so named because they are discrete lo-cations, are relatively easy to identify and control. Althoughthey are obvious sources for which controls can be effected,pollution control can be costly. Abandoned metal mines inCanada’s Arctic region, for example, leak a variety of pollu-tants (mostly heavy metals) into nearby streams and willcost billions of dollars to clean up.

In the past decade, scientists have come to realize thatpoint sources are only half the problem. The other half arethe nonpoint sources—less discrete sites such as farms,forests, lawns, and urban streets (FIGURE 21-1b). Rainwaterwashes pollutants from these sources into nearby streams,rivers, and lakes (Table 21-1).

Water pollutants arise from natural and anthropogenic sources.They travel freely from one location to another through rivers,streams, and groundwater. They are also transported from onemedium (land or air) to another (water).

from, how it affects living organisms, and finally,ways to reduce it. Like other chapters, this oneoutlines some components of a sustainable re-sponse to this problem.

Surface Water PollutionWater exists in many forms. It is found in the atmosphere asmist or clouds. It is locked in glaciers as solid ice. It is foundon the Earth’s surface in ponds, lakes, streams, and rivers,which are collectively referred to as surface waters and dis-cussed in Chapter 5. Water is also stored underground inaquifers. Such deposits are part of the planet’s vast ground-water holdings discussed in Chapter 13. This chapter dealswith water pollution occurring in groundwater and surfacewaters.

Water pollution is any physical or chemical change inwater that adversely affects organisms. Like many otherproblems, it is global in scope, but the types of pollutionvary according to a country’s level of development. In poor,nonindustrialized nations, water pollution is predominantlycaused by human and animal wastes, pathogenic organismsfrom this waste, pesticides, and sediment from unsoundfarming and timber practices. The rich industrial nationsalso suffer from these problems, but their more opulentlifestyles and numerous industries create an additional as-sortment of potentially hazardous pollutants: heat, toxicmetals, acids, pesticides, organic chemicals, and an assort-ment of pharmaceuticals (excreted in peoples’ urine). In be-tween these two extremes are numerous countries withvarious levels of industrialization. They often have inadequatelaws—or none at all—to combat water pollution, or if theydo have good pollution control laws, they frequently lack ad-equate funding to enforce them. Their waters are thereforeoften badly polluted with an assortment of industrial andmunicipal wastes.

KEY CONCEPTSNations produce many different types of water pollutants. Thewater in all countries is plagued with pollutants from human andanimal wastes, but in the industrial nations numerous toxicchemicals also contribute to water pollution.

21.1

469

CRITICAL THINKING

ExerciseA family living along Lake Superior arguesthat they don’t need to conserve water.There’s plenty of water in the lake, so whyshould they sacrifice? Do you agree with thisassertion? When you have finished, list thecritical thinking rules you used to analyze thisissue.

GO GREEN

To reduce water pollution, com-post organic kitchen wasterather than using the garbagedisposal.

470 PART V. Learning to Live with the Earth’s Carrying Capacity

Together point and nonpoint sources can result in hugeproblems. Many Canadian waters are polluted by direct dis-charge of pollutants from industrial and municipal pointsources and by indirect discharge from a long list of nonpointsources. The Frazer River in Canada, for instance, receivesincompletely treated sewage and a variety of toxic chemicalsfrom wood treatment and wood pulp and paper mills. It ispolluted by chemical leaching from nearby landfills.

In the United States, nonpoint sources release nearlytwo-thirds of the pollutants that end up in our waterways (FIG-URE 21-2). These substances include dust, sediment, pesti-cides, asbestos, fertilizers, heavy metals, salts, oil, grease,litter, and even air pollutants washed from the sky by rain.Because the sources are many and spread out, control hasproven difficult. It is also far easier for governments to forcea company to install a pollution control device on a factorythan to try to force tens of thousands of city dwellers to get

oil leaks in cars fixed or to apply pesticides to lawns more con-servatively. Although there are numerous sources of non-point water pollution, FIGURE 21-3 shows that agriculture isthe predominant nonpoint source in the United States, af-fecting nearly 60% of the nation’s streams.

The remaining portion of this section covers the majortypes of point and nonpoint water pollution.

KEY CONCEPTSWater pollution arises from identifiable point sources, such asfactories, and from diffuse nonpoint sources, such as farm fieldsand streets. Point sources are much easier to control.

FIGURE 21-1 Water pollution sources. (a) This pipe dumping factory waste into a nearby river is an example of a point source.(b) Urban streets, lawns, and gardens are nonpoint sources. Heavy rains often wash pollutants from these sources into nearbywaterways.

(b)

(a)

Table 21-1Major Nonpoint Pollution Sources in the United States

Activity Explanation

Silviculture Growing and harvesting trees for lumber and paper production can produce large quantities of sediment.Agriculture Disruption of natural vegetation leads to increased erosion; pesticide and fertilizer use, coupled with poor

land management, can pollute neighboring surface water and groundwater.Mining Leaching from mine wastes and drainage from mines themselves can pollute surface and groundwater with

metals and acids; disruption of natural vegetation accelerates sediment erosion.Construction Road and building construction disrupts vegetation and increases sediment erosion.Salt use and ground- Salt from roads and storage piles can pollute groundwater and surface water; saltwater intrusion fromwater overuse groundwater overdraft pollutes ground and surface water.Drilling and waste Injection wells for waste disposal, septic tanks, hazardous waste dumps, and landfills for municipal garbagedisposal can contaminate groundwater.Hydrological Dam construction and diversion of water both can pollute surface waters. modificationUrban runoff Pesticides, herbicides, and fertilizers applied to lawns, as well as residues from roads, can be washed into sur-

face waters by rain.

where the waste is held for treatment, flowed into streams(FIGURE 21-4). Hundreds of millions of gallons of hog wastespoured into wetlands, creeks, and rivers.

In less developed countries (LDCs), organic pollutantscome primarily from human sewage and animal wastes. Rawsewage often enters water without treatment.

In surface waters, organic pollutants are consumed bynaturally occurring bacteria. With an abundant food source,the bacterial populations proliferate. As bacteria consume theorganic matter, they help to purify the waters and are there-fore part of nature’s system of restoration. Unfortunately,there’s a catch.

The degradation of organic pollutants by bacteria utilizesoxygen, which is dissolved in water (FIGURE 21-5). Excess or-ganic matter therefore causes oxygen levels to drop; as a re-sult, fish and other aquatic organisms may perish. Whenoxygen levels become very low, anaerobic (non–oxygen-requiring) bacteria take over, breaking down what’s left. Inthe process, though, they produce foul-smelling and toxicgases (methane and hydrogen sulfide).

Oxygen depletion in rivers and streams occurs morereadily in the hot summer months because stream flow is gen-erally low and organic pollutant concentrations are higher.

Other 3%

Industrial 9%

Municipal 17%

Background 6%

Nonpoint65%

FIGURE 21-2 Major sources of U.S. stream pollution. This piechart shows the contribution of point and nonpoint sources tototal water pollution in the United States. Municipal, Industrial,and Other are point sources (Background is natural pollution.).Nonpoint sources are by far the greatest polluter of U.S. waters.

70

60

50

40

30

20

10

0

Agr

icul

ture

Mun

icip

al w

aste

Res

ourc

e ex

tract

ion

Hab

itat m

odifi

catio

nS

torm

sew

ers

Silv

icul

ture

Indu

stry

Con

stru

ctio

nLa

nd w

aste

dis

posa

l

% o

f str

eam

mile

s af

fect

ed

FIGURE 21-3 Sources of nonpoint water pollution affectingstreams. This bar graph lists nonpoint water pollution sources inthe United States by their impact—that is, the percentage ofmiles of streams they affect in the United States. Agricultural ac-tivities and municipal wastes (sewage) turn out to be the numberone and two contributors.

1An organic compound consists primarily of carbon and hydro-gen atoms.

Organic NutrientsIn more developed countries, large quantities of organicchemicals are released into surface waters from point sourcessuch as feedlots, sewage treatment plants, and various in-dustries such as paper mills and meat-packing plants.1 Inmany cases, these wastes are treated prior to release intostreams. Even so, large quantities of organic waste still entersurface waters. Flooding can also cause severe problems.In 1999, for example, a series of hurricanes and tropicalstorms hit the southeastern United States. In North Car-olina, 20 municipal sewage treatment plants were flooded,releasing enormous amounts of untreated human waste intostreams and other water bodies. Making matters worse, manyof the state’s 4,000 hog farms were flooded out by heavy per-sistent rainfall. Waste on the ground and in lagoons, ponds

FIGURE 21-4 Hundreds of hog farms, many built in flood plainslike this one were flooded by Hurricane Floyd in 1999, drowningtens of thousands of animals. Sewage lagoons overflowed andwaste from the thousands of farms flowed into rivers, lakes, andthe ocean.

CHAPTER 21: Water Pollution: Sustainably Managing a Renewable Resource 471

TroutBlack bass

Trout

Black bass CarpGar Carp

GarFish absent

Mayfly larvae Stone fly larvaeCaddis fly larvae

Mayfly larvae Stone fly larvaeCaddis fly larvae

Sludge worms Midge larvaeMosquito larvae

Black fly larvaeMidge larvae

Black fly larvaeMidge larvae

Invertebrates

Cleanwater

Cleanwater

Point of discharge of sewage with high BOD

Decomposition Recovery

Dissolvedoxygen

Biochemical oxygen demand 2 ppm

8 ppmOxygen sag

Time of distance downstream from point of discharge

Con

cent

ratio

n

Types of organisms

Dominantfish


FIGURE 21-5 The oxygen sagcurve. Oxygen levels and biochemi-

cal oxygen demand in a stream areshown downriver from a point source of

organic nutrients. Oxygen levels dropimmediately below the pollution source as

a result of bacterial decay of organic mat-ter. Oxygen levels recover downstream after

the organic matter is removed from the water.

In addition, increased watertemperatures speed up bac-terial decay.

Because streams are flow-ing systems, oxygen levels mayreturn to normal if the pollu-tion is a one-time event. However, when numerous sources oforganic pollutants are found along the course of a river—orwhen organic input exceeds the ability of the aquatic system torestore conditions through bacterial decomposition and waterflow—recovery may be impossible. Lakes can also recover fromorganic pollutants, but usually much more slowly than rivers.

The organic nutrient concentration in streams is esti-mated by a test that determines the rate at which oxygen isdepleted from a test sample. In this test, polluted water is sat-urated with oxygen and held in a closed bottle for 5 days; dur-ing this period, bacteria in the water degrade the organicmatter and consume the oxygen that was added to it. Theamount of oxygen remaining after 5 days gives an indicationof the organic matter present; the more polluted the sample,the less oxygen is left. This standard measurement is calledthe biochemical oxygen demand, or BOD.

KEY CONCEPTSOrganic nutrients come from a variety of sources, primarilytreated and untreated waste (human and other animals) acci-dentally and intentionally released into waterways. Organiccompounds stimulate bacterial growth, which depletes oxygenlevels in water bodies, killing off oxygen-dependent species.Oxygen levels can return to normal levels, but only if the influxof organic materials ceases.

Inorganic Nutrients—Nitrates and PhosphatesInorganic nutrients are chemical compounds produced bya variety of sources, many of which also release organic nu-trients. Two of the most common inorganic nutrients are ni-trogen and phosphorus. Unlike organic nutrients, whichstimulate the proliferation of bacteria, inorganic nutrients tendto promote the growth of algae and aquatic plants.

In terrestrial and aquatic ecosystems, nitrogen is con-tained primarily in the form of ammonia and nitrates. Phos-phorus is found in phosphates. In aquatic ecosystems, nitrogenand phosphorus are often limiting factors for populations ofalgae and other aquatic plants (Chapter 6). Consequently, iflevels of these pollutants increase, algal and plant growthmay increase dramatically. Lakes and rivers become chokedwith thick mats of algae or dense growths of aquatic plants.In freshwater lakes and reservoirs, phosphate is usually thelimiting nutrient for plant growth; marine waters are usu-ally nitrate limited.

Excessive plant growth impacts people and the envi-ronment. For example, during the summer the proliferationof plants often impairs fishing, swimming, navigation, andrecreational boating. In the fall, most of these plants die andare degraded by bacteria. When large amounts of plant mat-ter decay, dissolved oxygen levels fall, killing other aquaticorganisms. As oxygen levels drop, anaerobic bacteria resumethe breakdown and produce the noxious products notedearlier. Thus, inorganic nutrients create many of the sameproblems that organic nutrients do. Where do inorganic nu-trients come from?

GO GREEN

Use low- or nonphosphate detergents to reduce waterpollution.

course, shallow lakes are many times more vulnerable thandeeper lakes.

Humans can accelerate the decay of lakes and ponds. Ac-celerated erosion, caused by human activities, and nutrientsentering from farms, feedlots, and sewage treatment plants—called cultural eutrophication—both contribute to the de-terioration of lakes. Inorganic nutrients may cause good,productive lakes to become choked with vegetation. In tem-perate climates, the plants rot in the fall. Sediment from ero-sion and organic debris caused by excessive plant growthcan eventually fill the lake, destroying it.

The fate of lakes overfed with nutrients from sewagetreatment plants and farms, however, is not as dim as scientistsonce believed; if nutrient inflow is greatly reduced or stopped,a lake may make a comeback. Lake Washington near Seat-tle, for example, became afoul-smelling, eutrophic eye-sore after decades of abuseduring which millions of gal-lons of sewage were dumpedinto its waters. In 1968, localcommunities began to divert their wastes to Puget Sound, anarm of the sea with a greater capacity to assimilate the wastes.Lake Washington began a slow recovery.

Of course, the diversion of sewage to Puget Sound has hadsome negative effects. Although the sound cleanses itselfmore quickly than the lake, certain toxic substances in thewaste and in surface runoff (nonpoint pollution) are havinga harmful effect on marine life. The effects are especially noticeable in areas where industries have discharged theirwastes for decades. Today, sediments in the sound contain

Inorganic fertilizer from croplands is the major anthro-pogenic source of plant nutrients in fresh waters. Whenhighly soluble fertilizers are used in excess, as much as 25%may be washed into streams and lakes by the rain. Applyingfertilizer in smaller amounts and implementing measuresto reduce surface runoff of farmland, such as terracing andstrip cropping, could greatly reduce the amount of phos-phates and nitrates entering surface waters (Chapter 10).

Fertilizers also pollute groundwater with nitrates. InCanada’s Lower Frazer River Valley and in southern On-tario, nitrate pollution in groundwater has been traced tothe application of manure and artificial fertilizer and from sep-tic tanks.

Laundry detergents are the second most important an-thropogenic source of inorganic nutrient pollution in theUnited States and other developed countries. Many detergentscontain synthetic phosphates called tripoly-phosphates(TPPs). These chemicals cling to dirt particles and grease,keeping them in suspension until the wash water is flushedout of the washing machine.

Low and nonphosphate detergents are currently widelyavailable, but many people don’t need phosphate-based de-tergents at all. In fact, nearly 60% of the U.S. populationlives in soft-water regions where soap-based cleansing agentswork as well as detergents. In the hard-water regions, harm-less substitutes for TPPs can be used. For example, limesoap-dispersing agents have been used in bar soaps for yearsand could be used for laundry detergents.

Nitrates and nitric acid can also enter surface watersfrom the atmosphere, as described in Chapter 20. Accordingto the Environmental Defense Fund, about 25% of the ni-trogen polluting the Chesapeake Bay comes from wet and dryacid deposition. Nitrates and phosphates are also containedin animal waste—humans and livestock being the princi-pal sources. These pollutants may seep into groundwaterunder intense livestock operations, polluting the drinkingwater of local residents.

KEY CONCEPTS

Eutrophication and Natural SuccessionIn undisturbed ecosystems, lakes naturally pick up plant nu-trients from surface runoff and rainfall. The natural accu-mulation of nutrients in lakes is called natural eutrophication(u-TROH-feh-KAY-shun). Given sufficient time, natural eu-trophication and natural soil erosion can transform shallowlakes into swampland and then into dry land, a process callednatural succession (discussed in Chapter 6). As shown in FIGURE 21-6, inorganic nutrients that accumulate in lakesstimulate plant growth. The plants eventually die and con-tribute organic sediment to the lake’s bottom. This sedimentcombines with silt from erosion, gradually filling in a lake. Of

Inorganic nutrients stimulate excess plant growth, which impairsnavigation and swimming and disrupts the aquatic environ-ment. When the plants die, they decompose, causing oxygenlevels to decline precipitously—an effect that can be harmfulto a host of organisms.

Inorganic(plant)

nutrients

Siltation

Fills lake

Plantgrowth

Plantsdie

Organicsediments

Organicnutrients

FIGURE 21-6 Eutrophication and succession. This drawingshows the contributions of inorganic and organic nutrients andsediment to the succession of a lake into swampland. Inorganicnutrients contribute to eutrophication. Combined with sedimentfrom natural or anthropogenic sources, they can cause a lake tofill in.

GO GREEN

Use nontoxic biodegradablecleaning agents to reduce wa-ter pollution.



high levels of toxic organic wastes and heavy metals, whichmay explain the high incidence of tumors in sole, a fish thatlives on the ocean’s bottom. Shellfish beds have been closedto prevent people from harvesting contaminated shellfish. Ef-forts are now under way to minimize sewage and industrialwaste discharged into the sound.

The story of Puget Sound reminds us that when it comesto pollution there is no “away.” The diversion of waste fromone location to another is often not a remedy, just a quick fixthat transfers a problem from one location to another. It alsoillustrates the importance of preventing problems in the firstplace. By minimizing or eliminating the discharge of pollutantsinto the environment, we stand a better chance of living sus-tainably on the planet. The Puget Sound case also illustratesthe economic impact of human actions. Contamination ofshellfish beds by human wastes not only threatens naturalsystems and organisms, it threatens human health and theeconomic well-being of those who make a living from the sea.

Eutrophication is the most widespread problem in U.S.lakes. According to a report by the EPA that summarizedthe results of water-quality assessments of lakes, reservoirs,and ponds by states and Native American tribes, 14% of thewater bodies assessed were polluted by nutrients that causeeutrophication. (The states only assessed 42% of their ponds,lakes, and reservoirs acreage.) Nearly all receive wastes fromindustry and municipalities, but even if these sources wereeliminated, many lakes would probably not improve signif-icantly because of continued pollution from nonpoint sources.

KEY CONCEPTSThe accumulation of nutrients in lakes, from both natural and hu-man sources, is called natural and cultural eutrophication, respec-tively. Combined with the deposition of sediment from humanactivities, cultural eutrophication causes lakes to age prematurely.

Infectious AgentsWater may be polluted by pathogenic (disease-causing) or-ganisms, including bacteria, viruses, and protozoans. The ma-jor infectious diseases transmitted via water include viralhepatitis, polio (viral), typhoid fever (bacterial), amoebicdysentery (protozoan), cholera (bacterial), schistosomiasis(parasitic worm), and salmonellosis (bacterial). These dis-eases are especially harmful to the young, old, and infirm. Themajor sources of infectiousagents are (1) untreated orimproperly treated sewage,(2) animal wastes in fieldsand feedlots located nearwaterways, (3) meat-packing and tanning plants that releaseuntreated animal wastes into water, and (4) some wildlifespecies that transmit waterborne diseases.

Waterborne infectious diseases are a problem of im-mense proportions in the less developed nations of Africa,Asia, and Latin America, as witnessed by the outbreak ofcholera in the 1990s in many Central and South Americannations. Safe drinking water is very hard to come by in manyless developed nations.

Infectious agents were once the major water pollu-tants of now-developed nations, too, before sewage treat-ment plants and disinfection of drinking water becamecommonplace. Despite these improvements, problems re-main. In many cities, sewage and storm runoff travelthrough the same pipes. Both end up in the sewage treat-ment plant. However, when heavy storms occur, thestormwater fills the system, and excess water containingboth sewage and stormwater bypasses the sewage treat-ment plants, ending up in rivers and lakes. Flooding alsocauses sewage treatment plants located in flood plains (acommon practice) to overflow. According to a U.S. EPA re-port that summarized the findings of states, 15% of the riversstudied had unacceptable levels of bacteria. (This survey onlycovered 26% of the nation’s waterways.) Although this ishigh, it is nothing compared to the condition of waterwaysin the less developed nations.

Still, infectious agents can cause enormous problemsin more developed countries. In 1993, 400,000 residentsof Milwaukee, Wisconsin, developed flu-like symptomsafter drinking water contaminated by a protozoan parasiteknown as Cryptosporidium (CRYPT-toe-spore-ID-eum)(FIGURE 21-7). Eight people died. This organism entered thedrinking water drawn from Lake Michigan. The parasitelives in the intestinal tract of land-dwelling animals such ascows, pigs, and chickens. Scientists believe that its eggs werewashed into the Milwaukee River and then into the lakeafter heavy spring rains. Water is drawn for the city’s treat-ment plant only 3 miles from the river. A few days before theoutbreak of the disease, the treatment plant’s filtration sys-tem failed to operate at peak efficiency, permitting millionsof microscopic eggs to enter the system. Such instances arerare in more developed countries. Outbreaks that do occurare most commonly associated with contaminated food suchas eggs, tomatoes, and spinach. From May 1 to Dec 1, 2010,

GO GREEN

Avoid use of soaps containingantibacterial agents.

FIGURE 21-7 Cryptosporidium. This microorganism can causewidespread illness if it contaminates public drinking supplies.

for instance, there were nearly 3,600 reported cases of salmonella infection—an intestinal infection caused, in thisinstance, by eggs contaminated with the salmonella bacterium.It was believed to come from contaminated feed. More than380 million eggs were recalled in the summer of 2010.

Measuring the level of pathogenic organisms would becostly and time consuming for cities and towns. However, bymeasuring levels of a naturally occurring intestinal bac-terium, the coliform bacterium, water quality personnelcan determine how much fecal contamination has occurred(FIGURE 21-8). The higher the coliform count, the more likelythe water is to contain some pathogenic agent from fecal con-tamination. As noted previously, 15% of U.S. rivers assessedviolate standards for coliform bacteria. Rivers in many lessdeveloped nations are very heavily polluted with humanwastes. A river in New Delhi, India, for example, has a coli-form bacteria count of 7,500 per 100 milliliters, which isextremely high, before it enters the city. The count jumps to24,000,000 per 100 milliliters after leaving the city. Diseaseand mortality rates are understandably very high.

Monitoring coliform bacteria in water is not by itselfsufficient to protect human health. Several studies show thatswimmers have developed gastrointestinal disorders andflu-like symptoms after swimming in seawater containing lev-els of coliform bacteria considered safe by government stan-dards. Researchers have found that these symptoms arerelated to exposure to another noncoliform bacteria, a groupknown as fecal streptococcal bacteria. Some water qualityexperts believe that they are a more sensitive indicator ofhuman fecal contamination. Others argue that, to protecthuman health adequately, two or more microorganisms oughtto be monitored, including viruses.

KEY CONCEPTS

Toxic Organic Water PollutantsAbout 85,000 synthetic organic compounds are in use todayin the industrialized nations. These include solvents, pesticides,and a host of others. Some ofthese chemicals find their wayinto surface waters directlyfrom factories.2 Others, suchas pesticides, enter waterwaysin surface runoff. Still others,such as toxic cleaning agents,enter sewage from homes. Concerns over toxic organic pol-lutants are many: (1) Many toxic organic compounds are non-biodegradable or degrade slowly, so they persist in theecosystem; (2) some are biomagnified in the food web (Chap-ter 18); (3) some bioaccumulate; (4) some chemicals cause can-cer in humans and aquatic organisms, whereas others areconverted into carcinogens after reacting with the chlorineused to disinfect water; (5) many are toxic to fish and otheraquatic organisms; and (6) some are mere nuisances, givingwater and fish an offensive taste or odor.

Unfortunately, our knowledge of the effects of syn-thetic organics, which are often found in low concentrations,is rudimentary. Reports of diseases traceable to a singlechemical are few, but many experts worry that cancer andgenetic damage may result from long-term exposure to thewide array of toxic substances found in the waterways ofthe world.

KEY CONCEPTS

Toxic Inorganic Water PollutantsToxic inorganic water pollutants encompass a wide rangeof chemicals, including metals, acids, and salts. Some ofthem have become major water pollutants. In most states, forexample, toxic metals such as mercury and lead are found in

Numerous toxic chemicals enter the waterways from factories,homes, farms, lawns, and gardens. They may have many differ-ent effects on people and the environment. As a rule, concen-trations in surface waters are low.

Numerous infectious agents are found in surface waters, espe-cially in the less developed nations where they cause consider-able amounts of suffering and death. Sewage treatment facilitiesand drinking water purification have greatly reduced the inci-dence of disease in more developed countries, although outbreaksdo occur. To monitor infectious agents, officials generally mea-sure fecal coliform levels, a harmless bacterium itself, but an in-dicator of the presence of fecal contamination.

FIGURE 21-8 Fecal coliform bacteria. This nontoxic bacterium isan indicator organism. Drinking water quality personnel measure itto determine the level of fecal contamination in water supplies. Itspresence suggests the possible presence of pathogenic organisms.

2Toxic organic pollutants differ from organic nutrients discussedearlier because they do not nourish plants. They are harmful toboth plants and animals because they alter metabolism, as discussedin Chapter 18.

GO GREEN

Use natural and nontoxic clean-ers to help reduce water pol-lution.



levels that are considered unsafe for people and other or-ganisms. Metals come from many sources, among them in-dustrial discharge, urban runoff, sewage effluents, and mining.They are also derived from air pollution fallout. This is an-other example of cross-media contamination (Chapter 18).Mercury emitted from coal-fired power plants, for instance,is washed from the sky and enters rivers, lakes, and streams.Recent surveys of U.S. drinking water show that some heavymetals such as lead come from pipes; others may come fromgroundwater supplies.

KEY CONCEPTS

Mercury One of the morecommon and potentiallymost harmful toxic metals ismercury. In the 1950s, mer-cury was thought to be an in-nocuous water pollutant,although it was known tohave been hazardous to min-ers and to 19th-century hat-makers exposed to mercury during the manufacture of hatbrims. Both miners and hatters frequently developed tremors,or “hatter’s shakes,” and lost hair and teeth.

In the 1950s, an outbreak of mercury poisonings inJapan raised awareness of the hazard. Residents who ateseafood from Minamata Bay, which was contaminated withmethyl mercury, developed numbness of the limbs, lips, andtongue. They lost muscle control and suffered from other neu-rological defects, among them deafness, blurring of vision,clumsiness, apathy, and mental derangement. Of 52 reportedcases, 17 people died and 23 were permanently disabled.

Mercury is a byproduct of manufacturing the plastic vinylchloride, from which beach balls, toys, and other productsare made. It is also emitted in aqueous wastes of the chem-ical industry and from incinerators, coal-fired power plants,research laboratories, and even hospitals. Worldwide, anestimated 5,000 to 13,000 metric tons (5,500 to 14,300 tons)of mercury are released into the air and water each year.

In streams and lakes, inorganic mercury is convertedby bacteria into two organic forms. One of these, dimethylmercury, evaporates quickly from the water. The other,methyl mercury, however, remains in the bottom sedimentsand is slowly released into the water, where it enters organ-isms in the food chain and is biologically magnified. Themercury poisoning that affected those eating seafood fromMinimata Bay resulted from biological magnification ofmethyl mercury. In Minnesota and other northern states,mercury levels in fish are so high that wildlife officials pub-lish booklets that warn anglers to limit their intake of fish.Mercury even contaminates saltwater fish like swordfish,making some hazardous to eat, especially for young chil-dren and pregnant women.

Numerous inorganic pollutants such as acids and heavy metalsmake their way into the surface and groundwater of industrialnations, usually from industrial sources. Some, such as lead andmercury, are of major concern.

KEY CONCEPTS

Nitrates and Nitrites Nitrates and nitrites are commoninorganic pollutants of water. Nitrates in surface and ground-water come primarily from animal waste and artificial fer-tilizers. The sources include septic tanks, barnyards, sewagetreatment plants, and heavily fertilized crops. Besides stim-ulating algal and plant growth, described earlier, nitrates arealso converted to toxic nitrites in the intestines of humans.Nitrites combine with the hemoglobin in red blood corpus-cles and form methemoglobin, which has a reduced oxy-gen-carrying capacity. Nitrites can be fatal to infants. Althoughrare today, nitrite poisonings usually occur in rural areaswhere drinking water is contaminated by septic tanks, farm-yards, or intensive livestock operations such as pig farms.

KEY CONCEPTS

Salts Sodium chloride and calcium chloride are used onwinter roads, driveways, and sidewalks to melt ice andsnow. However, meltwater from ice and snow carries saltsinto streams and groundwater. Salts kill sensitive plantssuch as the sugar maple. Apple and peach trees are alsoaffected.

In surface waters, salts may kill salt-intolerant organisms,allowing salt-tolerant species to thrive. However, the fluc-tuations in water flow lead to varying salt concentrations. Thisis a condition that neither salt-tolerant species (which thrivein high salt concentrations) nor salt-intolerant organismscan survive. Many cities and towns are now adding a solu-tion of magnesium chloride to roads before snowstorms.Magnesium chloride prevents snow from sticking to theroad and prevents dangerous black ice, making winter driv-ing safer. This liquid works like antifreeze—it lowers thefreezing point of water. This prevents ice from forming astrong bond on the road and helps keep roads from becom-ing slippery, thus reducing accidents. Magnesium chloridealso replaces sand-salt mix applied to roads. Sand can be re-trained, that is, injected into the air, causing air pollution.Does magnesium chloride use pose any environmentalproblems?

Environmental studies conducted in the 1980s showedmagnesium chloride to be less toxic than salt. Tests haveshown that the proper application of magnesium chloride pro-duces no negative effects on groundwater, surface water, orvegetation. Further research, however, shows that magnesiumchloride, far from being safe, can cause extensive damage toroadside vegetation. It appears to be directly toxic to trees andinhibits water absorption by their roots. Further research isneeded to assess the impact of magnesium chloride on fishand other aquatic organisms.

Nitrates can be converted to nitrites, which bind to hemoglo-bin and reduce the oxygen-carrying capacity of the blood.

Mercury is emitted from many sources, among them vinyl fac-tories and coal-fired power plants, and is one of the most com-mon and most toxic inorganic pollutants, primarily exerting itseffect through the nervous system.

GO GREEN

Use energy efficiently to reducemercury release from coal-firedpower plants. Energy efficiencyalso reduces other air pollu-tants that eventually end up insurface waters.

KEY CONCEPTS

Chlorine Chlorine is a highly reactive inorganic chemi-cal. It is commonly used (1) to kill bacteria in drinking wa-ter; (2) to destroy potentially harmful organisms in treatedwastewater released from sewage treatment plants intostreams; and (3) to kill algae, bacteria, fungi, and other or-ganisms that grow inside and clog the pipes of the coolingsystems of power plants. Chlorine and some of the prod-ucts it forms in water are highly toxic to fish and other or-ganisms.

Chlorine reacts with organic compounds to form chlo-rinated organics. These chemicals may show up in drink-ing water downstream from sewage treatment plants andother sources. Many of them are known carcinogens and ter-atogens. However, medical studies indicate that the rates ofcertain cancers (liver, intestinal tract) are only slightly ele-vated in populations consuming water contaminated bythese compounds.

KEY CONCEPTS

SedimentSediment is the leading wa-ter pollutant in the UnitedStates in terms of volume.Consisting of dirt particlesand sand, sediment is largelya byproduct of a number ofpoorly planned and executedpractices such as logging, agriculture, mining, and con-struction of roads and buildings. Agriculture, for example,increases erosion rates on average four to eight times abovenormal, sometimes much more. Poor construction and min-ing may increase the rate of erosion by 10 to 200 times. Sed-iment is also a major problem in the less developed countries,where poor farming practices, overgrazing, and careless log-ging practices commonly occur.

Sedimentation, the deposition of sediment in surface wa-ters, has many social, economic, and environmental im-pacts. Sediment, for instance, destroys spawning and feedinggrounds for fish. It also smothers fish eggs and fry and thusreduces fish and shellfish populations. Suspended sedimentsdecrease light penetration in water bodies, which may im-pair the growth of algae and aquatic plants, the base of thefood chain. Each of these environmental impacts exacts a so-cial and economic cost. As rivers and lakes are destroyed, forinstance, they reduce recreational opportunities such as fish-ing; this not only robs many individuals of satisfying enter-tainment, it also reduces revenues to local bait shops andother segments of the local economy dependent on fishing.

Chlorine is routinely added to water to kill harmful organisms.Unfortunately, it also reacts with organic compounds to form sub-stances toxic to humans and other organisms.

Road salts used to remove ice and make driving safe can pro-foundly affect aquatic ecosystems, forests, and orchards.

The deposition of sediment in lakes speeds up naturalsuccession. Sediment deposited in streams, called streambedaggradation (ah-gra-DAY-shun), results in a gradual widen-ing of the channel. As streams become shallower, they becomewider. Water temperature may rise, lowering the amount ofdissolved oxygen and making streams more vulnerable to or-ganic pollutants that deplete oxygen. Lowered dissolvedoxygen also wipes out species such as trout that requirehigher levels. Streambed aggradation also makes streamsmore susceptible to flooding. In addition, sediment can fillshipping channels, which must then be dredged at consid-erable expense. As noted in Chapter 13, sediment fills inagricultural and municipal reservoirs throughout the world,reducing their lifespan. Moreover, hydroelectric equipmentassociated with dams may be worn out by sediments. Fi-nally, some pollutants—such as pesticides, nitrates, phos-phates from agricultural fertilizers, and pathogenicorganisms—bind to sediment. This extends their lifetimeand biological impacts. Sediment pollution can be checkedand even eliminated, however, by good land management andrestoration (described in Chapters 10 and 12).

KEY CONCEPTS

Thermal PollutionUnknown to many people,industry also pollutes waterby dumping warm or hot wa-ter into cooler surface wa-ters. Rapid or even gradualchanges in water tempera-ture can disrupt aquaticecosystems with profound effects. Where does all this hot wa-ter come from?

Power plants and factories often must use water to coolliquids or machinery. They obtain this water from nearbylakes, oceans, and rivers. The U.S. electric power industryis a major contributor (FIGURE 21-9). It uses nearly 90% ofall cooling water in the United States, or about 795 billionliters (200 billion gallons) per day. Steel mills, oil refineries,and paper mills also use large amounts of water for cooling.

Small amounts of heat have no serious effect on theaquatic ecosystem, but large quantities can shift condi-tions beyond the range of tolerance of aquatic organisms(discussed in Chapter 4). Heat-intolerant organisms per-ish. Elimination of heat-intolerant species may allow heat-tolerant species to take over. These are usually less desirablespecies.

Thermal pollution lowers the dissolved oxygen contentof water, at the same time increasing the metabolic rate of fishand aquatic organisms. Metabolism consists of the chemi-cal reactions occurring in the cells of organisms. Because

Sediment washed from the land because of many poorly plannedand executed human activities such as mining and farming hasprofound effects on the chemical and physical nature of ecosys-tems. Such changes have profound impacts on aquatic organismsand humans who depend on them.

GO GREEN

Support efforts to replantforests and other ecosystemsto reduce soil erosion and wa-ter pollution.

GO GREEN

Use energy efficiently to helpreduce power production andthermal pollution caused bypower plants.



Steam

Steam

Stream flow

Reactorcooling water

Zone of thermal pollution

Condensorcooling water

Steam line

Nuclear reactor

18°C

18°C

18°C

27°C

Fuelrod

Steam condenses

FIGURE 21-9 Thermal pollution. Thisschematic drawing shows a cooling system of anuclear power plant and its effect on the tem-perature of surface waters of a nearby streaminto which the heated water is released. Waterfrom the river is used to cool water that circu-lates through the reactor. Heat picked up fromthis process by the river water is then dumped,along with the water, back into the stream (or lake), causing a dramatic increase in watertemperature that is harmful to aquatic life.

metabolism requires oxygen, somespecies may be eliminated entirely ifthe water temperature rises 10°C(18°F). At the Savannah River nu-clear power plant, the number ofrooted plant species and turtles was atleast 75% lower in ponds receiving hotwater than in ponds at normal temperature.The number of fish species was reduced by onethird.

Sudden changes in water temperature can cause thermalshock, the sudden death of fish and other organisms thatcannot escape into cooler neighboring waters. Thermal shockis frequently experienced when power plants begin opera-tion or when they temporarily shut down for repair. The lat-ter event can devastate heat-tolerant species that inhabitartificially warmed waters.

Fish spawn and migrate in response to changes in wa-ter temperature, and thermal pollution may interfere withthese processes. Water temperature also influences the sur-vival and early development of aquatic organisms. For in-stance, trout eggs may not hatch if water is too warm. Thermalpollution can also increase the susceptibility of aquatic or-ganisms to parasites, certain toxic substances, and pathogens.

Thermal pollution can be controlled by constructingponds for collecting and cooling water before it is releasedinto nearby lakes and streams. Cooling towers are anotherway to dissipate heat.

KEY CONCEPTS

Groundwater PollutionAquifers supply nearly one-fourth of the annual water de-mand in the United States and drinking water for over halfthe population. In rural areas, groundwater supplies 98%of the drinking water. Aquifers are also a major supplier ofwater in many other countries. In Canada, a country con-taining seven of the world’s largest lakes and with nearly 8%

21.2

Water from rivers and lakes is used to cool many industrialprocesses, electric power production being one of the majorones. Heat generated by these processes is often discharged di-rectly into surface waters, where it kills organisms outright orshifts the composition of the aquatic system.

of its land area covered by lakes and rivers, groundwaterstill contains 37 times more water than surface waters. Ac-cording to one estimate, approximately one in four Canadi-ans relies on groundwater for domestic uses. In some areas,however, such as Prince Edward Island, groundwater sup-plies 100% of the domestic demand. Sixty percent of thepopulation of New Brunswick and the Yukon are dependenton groundwater.

Scientists are now re-porting that U.S. and Ca-nadian groundwater isincreasingly threatened bypollution. In fact, many pol-lutants are present at much higher concentrations in ground-water than they are in most contaminated surface supplies.Also, many contaminants are tasteless and odorless at con-centrations thought to threaten human health.

About 4,500 billion liters (1,185 billion gallons) of con-taminated water seeps into the ground in the United Statesevery day from septic tanks, cesspools, oil wells, landfills,agriculture, and ponds holding hazardous wastes. Unfor-tunately, very little is known about the extent of ground-water contamination. The Environmental Protection Agencyestimates that 1% of the drinking water wells in the UnitedStates have contaminants that exceed the standards de-signed to protect human health. Although that may seemsmall, 1% of hundreds of thousands of wells is a large num-ber. In fact, one study reported that at least 8,000 private,public, and industrial wells in the United States arecontaminated.

GO GREEN

Use organic fertilizers and nat-ural pesticides on lawns andgardens.

KEY CONCEPTS

Effects of Groundwater PollutionThousands of chemicals, many of them potentially harmfulto health, turn up in water samples from polluted wells. Themost common chemical pollutants are chlorides, nitrates,heavy metals, and various toxic organics such as pesticides,degreasing agents, and petroleum products. In Canada, manyunderground storage tanks containing gasoline and otherpetroleum byproducts have begun to leak. The problem is es-pecially severe in the Atlantic provinces where groundwateruse is high.

Low-molecular-weight organic compounds are partic-ularly worrisome because many of them are carcinogenic.Concern among medical experts is great because some fearthat there is no threshold level for some of these com-pounds—that is, there is no level free from risk of cancer orother problems. Others fear that many chemicals may act syn-ergistically, making a potentially difficult problem muchworse.

With so many different chemicals in groundwater, it isnot surprising that the effects vary widely. Nonetheless, someeffects are more prevalent, according to Beverly Paigen, anOakland, California, researcher renowned for her studies atLove Canal in Niagara Falls, New York. In a summary reportof health studies of Americans exposed to groundwater pol-lutants, Paigen noted that the most common problems includemiscarriage, low birth weight, birth defects, and prematureinfant death. Adults and children suffer skin rashes, eye ir-ritation, and a whole host of neurological problems, in-cluding dizziness, headaches, seizures, and fainting spells.In a widely publicized case in San Jose, California, pollu-tants from a leaky underground storage tank owned by theFairchild Camera and Instrument Company are thought tohave doubled the rate of miscarriage in pregnant womenand tripled the rate of heart defects in newborns. In Woburn,Massachusetts, contaminated groundwater is blamed for adoubling in the childhood leukemia rate.

KEY CONCEPTS

Cleaning Up GroundwaterMany people think of groundwater as underground rivers.Nothing could be farther from the truth. Groundwater typ-ically moves slowly—from 5 centimeters (2 inches) to 64 cen-timeters (2 feet) a day. Because groundwater moves so slowly,

Thousands of chemicals may be found in a nation’s groundwa-ter. Many of them are potentially harmful to human health,causing problems for unborn children (miscarriage, birth de-fects, and premature infant death) and adults (rashes and neu-rological problems).

Groundwater is an important source of drinking water in many na-tions and may be heavily contaminated in numerous industrial-ized nations by industrial waste pits, septic tanks, oil wells, andlandfills. Groundwater in some rural areas may also be contam-inated by agricultural chemicals, notably pesticides and fertilizer.

it can take years for water polluted in one location to ap-pear in another. Additionally, once an aquifer is contami-nated, it can take several hundred years for it to cleanseitself.

Detecting groundwater pollution is expensive and timeconsuming. Numerous test wells must be drilled to samplewater and determine the rate and direction of flow. Despiteintensive drilling, health officials can easily miss a tiny streamof pollutants that flows through one portion of a large aquifer.Liquids that do not readily mix with water, for example, maytravel along the top or bottom of the aquifer in thin layersand are often difficult to detect.

Preventing groundwater pollution is generally the cheap-est way to protect this vital resource and is an essential ele-ment in creating a sustainable water supply system. Howcan we prevent this problem? Cutting down on the use of po-tentially toxic chemicals and taking measures to reduce oreliminate the production of hazardous wastes are importantfirst steps. Individuals can help by using natural or biodegrad-able cleaning agents. Hazardous waste recycling and im-provements in the ways we dispose of wastes would alsohelp. Ways to achieve these goals are discussed in Chapter23 on waste management.

Because many aquifers are already contaminated by po-tentially toxic substances, efforts are needed to reclaim them.It may, for example, be necessary to pump contaminatedwater from polluted aquifers to the surface and purify it.The water can be pumped back into the ground at that siteor used for a variety of purposes. This process, although fea-sible for some contaminants, is extremely expensive. Manyother approaches are being tested. For example, steam, var-ious solvents, and surfactants (substances that reduce sur-face tension of liquids) can be injected into aquifers toimprove recovery rates of chemicals. Laboratory studies ofthese ideas seem promising.

New techniques are also being developed to use natu-rally occurring bacteria in soil and groundwater to clean upsome contamination; this is called bioremediation. For in-stance, hydrocarbons (such as crude oil, gasoline, and cre-osote) that have leaked from storage tanks or are spilledfrom vehicles have polluted more groundwater used fordrinking than any other class of chemicals in the UnitedStates. Microbiologists have known since the late 1970s thatsome bacteria can digest or break down hydrocarbons in thesoil and groundwater, converting them into carbon dioxideand methane gases. Bacteria in the soil, however, as a rule candegrade only about 1% of the hydrocarbon pollution flow-ing past them. Why? Quite simply, they lack key chemicalnutrients needed for metabolism. By supplying these nutri-ents, researchers may be able to accelerate the bacterial de-composition of hydrocarbons.

KEY CONCEPTSGroundwater moves slowly and takes many years to cleanse it-self. Preventing groundwater pollution is essential to creatinga sustainable water supply. Equally important are efforts toclean up groundwater supplies already contaminated by poten-tially toxic chemicals.


Ocean Pollution“When we go down to the low-tide line,” Rachel Carson wrote,“we enter a world that is as old as the Earth itself—the primevalmeeting place of the elements of Earth and water, a place ofcompromise and conflict and eternal change.” Today thiscompromise, conflict, and eternal change have taken on a newmeaning as humankind forges out into the oceans in search offood, fuel, and minerals. In our use of the seas, we spill manytoxic substances, such as oil. Ocean pollutants also arise fromland-based activities, though. The Kansas farmer and theMinnesota factory, for instance, have an impact on this vast bodycontaining more than 1.3 billion cubic kilometers of water.Many inland pollutants are washed from the land or dumpedinto rivers, in which they are transported to the world’s oceans.

Oceanic life zones and the hazards of pollution in thebiologically rich coastal zones were discussed in Chapters 5and 13. You may want to review this material before readingthis section, which deals with five crucial challenges: (1) oilpollution, (2) plastic pollution, (3) medical wastes, (4) redtide (algal blooms), and (5) disposal of sewage in the ocean.

KEY CONCEPTS

Oil in the SeasOil spills from oil tankers receive a considerable amountof attention and lead many to believe that oil-tanker acci-dents are the major source of oil in the seas. The massiverelease of oil from the damaged offshore oil well in 2010 topsall spills (FIGURE 21-10).

On April 20, 2010, a deep-water offshore oil rig ownedby British Petroleum (BP) experienced a devastating explo-sion that killed 11 workers. Over the next 108 days, the leak-

The oceans are polluted by chemicals spilled into them directlyand by pollutants washed from the lands and transported tothem by rivers.

21.3 ing well released an estimated 5 million barrels of oil intothe Gulf of Mexico. Oil flooded pristine coastal beaches thatare the heart of much of the region’s economy. The oil slick wasestimated to be more than 208 kilometers (130 miles) long and110 kilometers (70 miles) wide, and has affected the coastlinesof four states: Louisiana, Alabama, Mississippi, and Florida.

Oil invaded fragile ecosystems, including wetlands andbayous, on which many species of wildlife depend. Biologistsbelieve that the oil from the leaking drill rig could causelong-term damage to these ecosystems and could, in fact,irreversibly alter some coastal ecosystems in the region.

Some of the nation’s most valuable wildlife refuges andconservation areas are located in the area affected by thespill. The Gulf of Mexico is home to hundreds of species. Eachyear, an estimated 5 million migratory birds such as ducksand geese pass through the region. The Gulf provides win-ter refuge or a resting spot on long migrations to 70% of thenation’s waterfowl. Many endangered species rely on Gulfwaters, among them the North Atlantic bluefin tuna, fourspecies of sea turtles, six whale species, sharks, and dolphins.

While the price tag of this disaster is not yet known, itcould be in the billions of dollars. Especially hard hit will bethe fishing industry in coastal communities, such as Louisiana’soyster and shrimp industry. In Louisiana, the annual retail saleof seafood comes to 1.8 billion. Recreation fishing nets another$1 billion in sales, and saltwater sport fishing generates about$757 million each year. Thousands of jobs depend on theGulf water.

Although huge oil spills do occur and can pose a threatto coastlines, coastal wetlands, and fish and wildlife, nearlyhalf (47%) of the oil entering our oceans comes from nat-ural seepage from offshore oil deposits, according to theNational Research Council (NRC). According to their report,Oil in the Sea III, natural seepage contributes about 4.3 mil-lion barrels (180 million gallons) of oil per year.

The second largest source of oil pollution in the seacomes from oil runoff from paved areas in urban and sub-urban areas, including streets and parking lots.Oil drippingfrom cars or dumped down sewer drains runs into riversafter rainstorms and makes its way to the sea. Oil is also re-leased from boats and jet skis, which burn a mixture of gasand oil. Together, these and several other sources, contributethe vast majority of petroleum introduced to the environ-ment through human activity. On average, they release ap-proximately about 3.3 million barrels per year or about140,000,000 gallons worldwide each year.

The third largest source is oil transportation, a cate-gory that includes oil spills and releases from refineries. To-gether, theses sources release slightly more that 1 millionbarrels (44,000,000 gallons) of crude oil or refined productsinto the world’s oceans, or about 12% of the total.

Oil and gas exploration and associated activities releaseabout 264,000 barrels or 11,000,000 gallons worldwide, eachyear, according to the NRC. That’s under 3% of the total.

KEY CONCEPTSHalf of the oil polluting the oceans comes from natural seepage;the rest comes from human sources, including tanker accidents andinland disposal. The largest natural source is inland disposal.


FIGURE 21-10 Oil flowed for days from this offshore oil well, severely damaged by an explosion.

Biological Impacts of an Oil Spill What happens to oilspilled from a tanker or a well? You may be surprised tolearn that about 25% of the chemicals making up crude oilare volatile—that is, they evaporate readily. Within 3 months,one-fourth of the chemical substances in oil evaporate, be-coming air pollutants. Relatively nonvolatile compoundsthat are lighter than water float on the surface, where theyare broken down by bacteria over the next few months.Nearly 60% of the oil spill is destroyed in this way. The re-maining 15% consists of heavier compounds that stick to-gether and sink to the bottom in huge globs. In cold polarwaters, oil decomposes very slowly. In some cases, it may be-come incorporated into sea ice and be released very slowlyfor years afterward.

Before oil’s chemical components can evaporate or bebroken down, they can have many harmful effects. Oil killsplants and animals in the estuarine zone. Especially hardhit are the barnacles, mussels, crabs, and rock weed (a typeof algae). Their recovery after a major spill may take 2 to 10 years. Oil also settles on beaches and kills organisms thatlive there. It settles to the ocean floor and kills benthic(bottom dwelling) organisms such as crabs. Those benthicorganisms that survive may accumulate oil in their tissue,making them inedible. Oilpoisons algae and may dis-rupt major food chains anddecrease the yield of ediblefish. It also coats birds, im-pairing flight or reducingthe insulative property offeathers, thus making the birds highly vulnerable to hypo-thermia (FIGURE 21-11). Gallant efforts are often made torescue birds sullied by oil. After cleaning off the oil, thebirds are kept in captivity, nursed back to health, and thenreleased. Two studies published in 1996, however, sug-gest that such efforts (which are quite costly) are fairly

ineffective. One extensive study of more sensitive speciesof rehabilitated seabirds found that they lasted, on average,only 4 days after release. A study of brown pelicans showedthat half of the birds released into the wild died within 6 months. Only 12 to 15% of the rehabilitated birds were stillalive after 2 years, far lower than the 80 to 90% two-yearsurvival rate of birds not exposed to oil. Why?

Birds immersed in oil inhale and ingest (swallow) toxicsubstances. These birds commonly suffer from anemia, immune system suppression, tissue damage, and hormonalimbalances. Researchers hypothesize that rehabilitated birds,although apparently healthy upon release, fare poorly be-cause their immune systems cannot protect them adequatelyunder the stressful conditions of life in the wild.

Oil also endangers fish hatcheries in coastal watersand can contaminate the flesh of commercially valuablefish, as it did in Prince William Sound in Alaska after theValdez spill.

The amount of damage caused by oil pollution dependspartly on the amount of oil spilled and the direction in whichit is carried by the wind and ocean currents. If slicks reachland, they damage beaches and shorelines, recreational ar-eas, and marine organisms. Oil may be driven over portionsof the continental shelf, a highly productive marine zone;there it can poison clams, scallops, flounder, haddock, andother important food species. Oil driven out to sea has fewerenvironmental consequences because there is little life inthe open waters of the ocean.

The damage resulting from an oil spill also depends onwhen it occurs, too. For example, the devastating spill offthe coast of Alaska in 1989 occurred only 2 weeks beforehundreds of thousands of ducks and other waterfowl migrated through the sound or came to nest. Had the spilloccurred after the migration, wildlife losses would havebeen much lower.

Oil pollution of the oceans poses less of a threat to theoverall marine environment than was once feared, a Na-tional Research Council committee has concluded. Oil canhave serious local effects, the group noted, and these canpersist for decades, as in the case of Prince William Sound.Overall, however, the marine environment has not sufferedirreversible damage from oil. The committee was quick topoint out that scientists have only limited knowledge of thepotential damage of oil in tropical and Arctic regions, wheremuch of the current oil development is occurring. Studiesof the 1989 oil spill in Alaska, for example, showed that thehydrocarbons in the oil are more stable and more persistentin the cold waters than in warmer seas. This could maketheir impact even greater.

KEY CONCEPTSOil spilled from human sources evaporates or is broken down bynaturally occurring bacteria or sinks to the bottom. Before itis eliminated, however, it can cause serious environmentaldamage. The extent of the damage depends on the amount spilled,the location of the spill, the prevailing weather conditions, andthe season.

FIGURE 21-11 Oil-covered duck. This bird was beyond the helpof volunteers who attempted to save many oil-covered animalsafter the 1989 oil spill in Prince William Sound (Alaska).

GO GREEN

Never dump oil down a sewer—ever! Change oil through companies that recycle or reuseoils.



Num

ber

of s

pills

0

30

35

25

20

15

10

5

Year

Indicates average number of spills per decade

1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010

1970–197925.4 spills per year on average




FIGURE 21-12 Number of spills over 700 tonnes. Data courtesy of International Tanker Owners Pollution Federation Ltd. (ITOPF)

Reducing the Number of Oil Spills Thanks to publicoutcry since the decade of the 1970s, the number of oilspills has fallen dramatically. FIGURE 21-12 shows that thenumber of large spills fell from an average of 25 per yearin the 1970s to 3.3 per year in the 2000s. Tougher gov-ernmental standards for new oil tankers went into effectin 1979. New safety standards for older tankers were phasedin between 1981 and 1985. Dual radar systems, backupsteering controls, collision avoidance aids, and improvedinspection and certification were instrumental in reduc-ing spills. In addition, under these regulations, crude oilmust be cleaned before it is pumped on board to elimi-nate sludge buildup in storage tanks. This sludge was oncerinsed out at sea. New regulations also require tankers to have separate ballast tanks. These tanks are filled withsalt water to help ships keep their balance when returningafter discharging their cargo. In older ships, empty oiltanks were once filled with water for ballast. When theship arrived at port, the oil-contaminated water was dumpedinto the sea.

The serious effects of oil washing and combined bal-last-oil tanks must not be underestimated. About 1.3 millionmetric tons (1.4 million tons) of oil were once released eachyear during tank purging and ballast tank discharge—oversix times the amount released by tanker spills.

Although the number of oil spills has decreased world-wide since the 1970s, the quantity of oil released fluctu-ates (FIGURE 21-13). In 2004, for example, 4.6 million

gallons were spilled from ships and barges; in 2002, oilspills from these sources was 4.5 greater, about 21 milliongallons.

In 1990 the U.S. Congress passed the Oil Pollution Act,which established a $1 billion fund to be used to clean up oilspills and pay for damages. The money comes from a 3-cents-per-barrel tax on domestic and imported oil and thus passesthe costs of cleanup and damage on to the consumer. Underthe bill, oil companies would ultimately be responsible forcleanup costs, but only up to a point because the law sets strictlimits on their financial liability. A company responsible fora spill, for instance, would pay only $10 million for cleanup.If the spill occurred near an onshore facility where damageis much greater, the company would pay $350 million foreach spill. The fund would be used to pay the additionalcosts. Many critics are disappointed with the liability limitsbecause the costs of cleaning oil are likely to be far greater.Cleanup in Prince William Sound to date has cost Exxon$2.5 billion and the federal government $154 million. In ad-dition, in 1992, Exxon agreed to pay an additional $1.25 bil-lion in criminal fees, restitution, and civil recovery (to paydamages to salmon fishing companies and other parties),although this money has never been paid.

Although the law requires new tankers to be equippedwith double steel hulls or effective double containment fea-tures to reduce the likelihood of spills, existing oil tankersare not required to be retrofitted. However, existing tankersmust be escorted by two towing vessels in high-risk areas, and

single-hull vessels started being phased out in 1995. By 2015all tankers with single hulls will be banned.

In addition, the law establishes regional oil spill re-sponse teams that can be deployed immediately after a spillto coordinate cleanup efforts. It also allows states to setstricter guidelines. A state, for instance, could mandate dou-ble hulls for use in its harbors.

KEY CONCEPTS

Sustainable Solutions to Oil Pollution Many of the stepsoutlined in this book to make human systems more sus-tainable will have a profound impact on water quality. Thissection describes how key principles of sustainable devel-opment—conservation, recycling, renewable energy use,restoration, and population control—can be applied to re-duce oil pollution, beginning with conservation.

Conservation is one of the most important principles ofsustainability. Energy conservation—using what we needand using it efficiently—is one of the most important areasto practice this principle. For example, energy efficiency inautomobiles and increased use of mass transit will decreasethe world’s dependence on crude oil and will reduce thenumber of oil wells that leak oil into the ocean. It will alsodecrease oil spills occurring each year, as noted previously.

Many efforts are under way in the United States and other coun-tries to reduce oil spills, including new standards for the con-struction of oil tankers.

Because much of the oil entering the oceans comes from dis-posal of oil on land, recycling of oil, rather than disposingof it in sewers, will also help protect the oceans. Renewableenergy resources cut pollution of water and air by reducingour dependence on fossil fuels.

KEY CONCEPTS

Plastic PollutionA young seal swims playfully in the coastal waters of SanDiego Bay. Floating in its watery domain is a piece of a plas-tic fishing net that has drifted with the currents for months.The seal swims around and around curiously and thenplunges through an opening in the net, only to be entrapped.

At first, the net is just a mild nuisance, but as the sealgrows, the filament begins to tighten around its neck. Even-tually, it cuts into the seal’s skin, leaving an open ring of rawflesh exposed to bacteria. Unless it is helped, the seal willperish, along with an estimated 100,000 turtles, seals, sealions, whales, dolphins, and other sea mammals and1,000,000 sea birds each year that die as a result of the es-timated 10 million metric tons (9 million tons) of plastics(including nets) discarded into the ocean annually by com-mercial fishers, sailors, and military personnel accordingto the environmental group Greenpeace. Tens of thousands

Conservation, recycling, and renewable resource use can all re-duce our dependence on oil and reduce oil pollution in the seas.

Tho

usan

ds o

f met

ric to

ns

0

300

350

400

450

500

550

600

650

Atlantic Empress287,000 tonnes

Castillio de Bellver252,000 tonnes

ABT Summer260,000 tonnes

Prestige63,000 tonnes

Hebei Spirit10,500 tonnes

Erika20,000 tonnes

Khark V80,000 tonnes

Exxon Valdez37,000 tonnes

250

200

150

100

50

Year1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010

FIGURE 21-13 Oil spills from 1970 to 2009. Note the dramatic decline in recent years thanks to higher safety standards. (Tonnes � metric tons.) (Data courtesy of International Tanker Owners Pollution Federation Ltd., ITOPF.)



of tons of plastic may also come from private boats, factories,and onshore facilities (FIGURE 21-14). Plastic also comesfrom bottles and bags discarded on beaches and plastic thatwashes into rivers during heavy rainstorms. No one knowsthe number of fish that die each year from nylon fishing nets,plastic bags, six-pack yokes, plastic straps, and a myriad ofother objects made from nonbiodegradable plastic.

Plastic nets entangle fish, birds, and sea mammals. Theymay strangle, starve to death, or drown their victims. Plas-tic bags, looking like jellyfish, are eaten by sea turtles. Onescientist pulled enough plastic out of a leatherback turtle’sstomach to make a ball several feet in diameter. In suchcases, starvation is the usual result because the animal’sstomach is packed with indigestible plastic that cannot passthrough its digestive tract. Birds and fish gobble plastic beadsresembling the tiny crustaceans that are a normal part oftheir diet. They may become poisoned and die. Discardedplastic eating utensils, when swallowed, may cut into an an-imal’s stomach lining, causing it to bleed to death.

Plastic is found throughout the world’s oceans, but in1997, a California sailor, surfer, and volunteer environmen-talist and a friend, who were heading back from a sailing racein Hawaii, headed into an area known as the doldrums. Knowntechnically as the North Pacific Subtropical Gyre, it is a regionof perennial high pressure. It forms a huge, slowly spiralingvortex of warm equatorial air. It draws in winds and turns themgently until they expire, hence the nickname, the doldrums.Several major sea currents also converge in the gyre, bring-ing with them floating debris from the Pacific coasts of South-east Asia, North America, Canada, and Mexico.

It is here that the sailors found an enormous region ofplastic pollution estimated to be twice the size of France.Known as Great Pacific Garbage Patch, it is likened to amarine soup, the main ingredient of which is floating plas-tic debris. Plastic garbage can be found as deep as 10 meters

(33 feet) and consists of small plastic flecks and particles,in many colors.

KEY CONCEPTS

Controlling Plastic Pollution As with many other envi-ronmental issues, public outcry created a groundswell of ac-tivity at many levels. On the local level, concern over plasticspurred the Oregon Fish and Wildlife Department to spon-sor annual beach cleanups to remove plastic that might bewashed out to sea (FIGURE 21-15). Italy placed a ban on allnonbiodegradable plastics, which went into effect in 1991.Following suit, Oregon and Alaska passed laws requiringthat all six-pack yokes be biodegradable. In 2007, San Fran-cisco became the first city to ban plastic shopping bags in gro-cery stores and large-chain pharmacies. Numerous countrieshave banned or taken action to reduce the use of plastic bagsincluding Australia, Bangladesh, Ireland, Italy, South Africa,and Taiwan.

On a larger scale, the U.S. Congress passed the Plastic Pol-lution Control Act (1988), which makes it unlawful for anyU.S. vessel to discard plastic garbage into the ocean. This leg-islation also requires all manufacturers of six-pack yokes touse degradable plastic if technically feasible. In 1988, theU.S. Senate approved an international treaty banning the dis-posal of plastics in the ocean. The agreement was signed by28 nations and went into effect in December 1988.

Millions of tons of plastic are dumped into the ocean each year,killing hundreds of thousands of marine mammals, fish, andbirds.

FIGURE 21-15 Trash on a beach in California. National and localinitiatives are helping to reduce the amount of plastic and othertrash like this on our beaches and in our oceans.

FIGURE 21-14 Victim of plastic pollution. A young hawksbillsea turtle is caught in a plastic fishing net cut loose by commer-cial fishing interests.

sometimes noxious, and sometimes deadly red tides appear tobe on the rise. At one time, they were found mainly in the wa-ters off the coasts of Europe and North America. Today, theyare also reported in coastal waters of Asia and South America.Scientists are not certain whether there is an actual increasein the incidence of such outbreaks or simply more awarenessof the problem and more frequent reporting.

Red tides are only occasionally red. They may be brownor green or orange. Some evidence suggests that they may becaused by elevated levels of plant nutrients, such as algalblooms in freshwater. The problem with red tides is that theorganisms that discolor the water contain toxic substancesthat protect them from predators. These organisms may beingested by shellfish, however, which themselves becometoxic to people.

Scientists have also discovered an entirely new family ofmicroorganisms (pfeisteria) that release an extremely toxicsubstance into the water. The substance is so toxic that sci-entists must take very special precautions when workingwith it—similar to those taken when studying the AIDSvirus in the laboratory. First identified in coastal waters ofNorth Carolina, this organism causes massive fish kills. Inthe laboratory, the organism is nourished by levels of phos-phate similar to those found in polluted rivers.

Some ecologists believe that toxic red tides represent aserious problem worldwide and are urging states and na-tions to step up efforts to reduce pollution that may be feed-ing these organisms.

KEY CONCEPTS

The Case of the Dying SealsIn the spring of 1988, harbor seals in the North Sea began todie in record numbers. Adult seals floated aimlessly in the wa-ter, too weak to eat. Pregnant females aborted their fetuses.The mysterious epidemic, which began off the coast of Den-mark, quickly spread to seal colonies throughout the Northand Baltic Seas. By the middle of the summer, seals were dy-ing along hundreds of miles of North Sea coastline. By Sep-tember, the disease had spread to the Atlantic coast of Ireland.

Some people dubbed this incident the “black death ofthe sea,” for it recalled the epidemics of bubonic plague, orblack death, which devastated the human population of Eu-rope in the 1300s. In this tragic turn of events, though, thevictims were helpless seals. In a few short months, the pop-ulation of harbor seals, once numbering 18,000, had fallento only 6,000.

Studies showed that the massive die-off was caused di-rectly by the phocine distemper virus (PDV), a new virus toscience. Biologists believe, however, that the virus was onlythe most immediate cause of death. Pollution in the seas,they say, may have greatly weakened the immune systems ofthe seals, making them highly susceptible to infection.

Outbreaks of microscopic and often highly toxic algae appear tobe on the rise worldwide and may be caused by an increase ininorganic nutrient pollution from agriculture, industry, and thehuman population.

Despite these steps, millions of fish, birds, and seamammals will perish in coming years. Without strictercontrols, international cooperation, and private efforts, theever-increasing use of plastic will bring about the unneces-sary death of innumerable sea creatures. The use of biodegrad-able plastics could help, but they are not a panacea. In fact,the term biodegradable plastic is a bit of a misnomer.Biodegradable plastics are plastics mixed with starch or someother material that breaks down, dispersing small particlesof plastic into the environment.

KEY CONCEPTS

Medical Wastes and Sewage SludgeIn the summer of 1988, many Americans were shocked tolearn that medical wastes were being illegally dumped intothe ocean. Bloody bandages, sutures, vials of AIDS-infectedblood, and used syringes washed up onto the eastern coastof the United States as well as onto the shores of Lake Erie.

Because there was no way to track the wastes to theirsource, the U.S. Congress passed the Medical Waste Track-ing Act (1988). It established a 2-year program that covered10 states and required people generating, storing, treating,and disposing of medical wastes to keep records that wereaccessible to the public. If wastes showed up on shorelines,they could be traced back to their source so that responsibleparties could be brought to justice. Unfortunately, this lawexpired in 1990 and has not been reauthorized, leaving con-trols up to the states. All states have some rules regarding med-ical waste disposal.

A far more important concern has been the dumping ofsewage into the ocean from sewage treatment plants. In1988, Congress passed the Ocean Dumping Ban Act, whichprohibited the dumping of sewage sludge (organic mate-rial from sewage treatment plants, discussed later) into theocean. This longstanding practice of many coastal citiesofficially ended on December 31, 1991. Even though it is nolonger legal to dump human wastes into the ocean, seweroverflows which occurs during heavy rainstorms, result ina considerable amount of raw sewage entering the oceaneach year.

KEY CONCEPTS

Red TideAnother growing problem occurring in the oceans of the worldis known as red tide. Red tide is a term that refers to reddishalgal blooms in coastal waters. Reports of sometimes harmless,

Medical wastes and sewage have long been dumped into theocean, but steps have been taken to eliminate both practices.The direct dumping of sewage has stopped entirely, but mil-lions of gallons of sewage enter the sea each year from sewagetreatment plants located near the coast.

Many steps have been taken to reduce the disposal of plastic intothe ocean, but huge amounts are still being disposed of each year,posing a serious threat to sea life.



Seals living in the waters off the coast of Germany andthe Netherlands are heavily contaminated with a toxic chem-ical called PCB (polychlorinated biphenyl), a substance onceused as an insulator in electrical devices. PCBs and otherchemical contaminants are believed responsible for the re-productive problems and the suppression of the seals’ immunesystems. PCBs entered the ocean from either land or air.

An emergency working group formed in London todeal with the epidemic. Made up of biologists, veterinari-ans, and toxicologists, the group concluded that “persistentpollutants could not be excluded as an additional factor inthe seal deaths.” Though there is not a great deal of evidenceabout what role pollution played, scientists found that thehighest seal mortality occurred in waters that were mostpolluted.

The North and Baltic Seas have been polluted for years.The pollution problem in the North and Baltic Seas, however,is compounded by the fact that both seas are shallow andcleanse themselves very slowly. The North Sea, for instance,purges itself only twice every 10 years. The Baltic Sea ismuch slower. Because they are cleaned so slowly, pollutionlevels can reach dangerous levels and have serious impactson fish, wildlife, and possibly people.

The seal plague may be the latest manifestation of achronic pollution problem in the North and Baltic Seas. For-tunately, many countries have decided to take action andhave entered into cooperative agreements. Most of the coun-tries bordering the North Sea, for instance, agreed to halvethe amount of nutrient pollution (nitrates and phosphates)and toxic chemicals flowing into the sea by 1995, a goal notyet met. A similar agreement was reached to cut pollution en-tering the Baltic Sea.

Seal deaths off the coast of Europe are a symptom of aglobal problem. Similar tragedies have occurred elsewhere.

In 1987, for example, as many as 4 of every 10 dolphins offthe Atlantic coast of the United States perished. Numerousdolphins perished off the coast of Florida in 1999, 2000,and 2004. Studies of gulls in the Great Lakes have shownan alarming reproductive failure because of PCBs and otherorganic pollutants.

KEY CONCEPTS

Water Pollution ControlTable 21-2 offers a quick summary of the different sourcesof water pollution and shows the major pollutants from eachone. This information is helpful in plotting control strategies.You may want to take a few minutes to go through the tableand devise some solutions. The real challenge is to devise so-lutions that prevent the problem in the first place. Also bearin mind the need to address both point and nonpoint sources.

As with other issues, water pollution control has tra-ditionally focused on end-of-pipe measures: pollution con-trol devices that remove the pollutants from a waste stream.Although these are important, the waste must go somewhere.Ultimately, the most sustainable approaches are those thatprevent the pollutant from being generated in the first place.

KEY CONCEPTSReducing water pollution requires efforts on two levels—thosethat capture wastes emitted from various sources (the so-calledend-of-pipe solutions) and those that prevent waste produc-tion and pollution.

21.4

A massive seal die-off in the late 1980s, caused by a virus, mayultimately have resulted from immune system suppression causedby a common pollutant, PCB.

Table 21-2Common Water Pollutants

Total Dissolved

Sources Bacteria Nutrients Ammonia Solids Acids Toxins

Point sourcesMunicipal sewage treatment plants • • • •Industrial facilities •Combined sewer overflows • • • • •Nonpoint sourcesAgricultural runoff • • • •Urban runoff • • • •Construction runoff • •Mining runoff • • •Septic systems • • •Landfills •Forestry runoff • •

Source: U.S. Environmental Protection Agency.

Some state and local governments have taken actions ontheir own by passing zoning laws aimed at reducing agri-cultural and urban runoff. Maryland, for instance, limits theamount of pavement accompanying development in water-sheds of Chesapeake Bay. In northern California, loggers areprohibited from clogging streams with silt. In addition, lo-cal soil conservation districts help to identify trouble spotsand work with farmers to decrease erosion and other prob-lems. North Carolina has instituted some innovative ap-proaches to control nonpoint sources. For example, itcurrently permits industry to work with farmers to implementnonpoint pollution controls—for example, erosion controls.Such measures are often cheaper than building treatmentfacilities and offer multiple benefits.

Despite these gains, much work is needed to reducenonpoint water pollution to sustainable levels. Because agri-cultural runoff is the largest source of nonpoint water pol-lution, affecting between 50 and 70% of all surface waterand groundwater in the nation, laws that address pollutionfrom farms are important. New regulations that require ter-racing of steep roadbanks, revegetation of denuded land,

Legislative ControlsThe cornerstone of U.S. water pollution policy is the CleanWater Act. While important, it has focused primarily onpoint sources, notably sewage treatment plants and factories.In fact, the Clean Water Act has provided funding to constructand improve thousands of U.S. sewage treatment plants thathandle municipal wastes (FIGURE 21-16). It has also requiredfactory owners to install water-pollution control equipmentto reduce the discharge of industrial waste into surface wa-ters (Table 21-3). For a success story, see Spotlight on Sus-tainable Development 21-1.

Unfortunately, in many cases nonpoint pollution fromexpanding cities offsets the gains from sewage treatmentplants. Pesticides from lawns; oil on driveways, parking lots,and streets; nitrate fertilizers from farm fields; and dozensof other nonpoint sources all contribute millions of tonsof pollution each year to U.S. waterways. Ironically, despiteintense efforts to control point sources, in many regionsexperiencing rapid population growth water quality has notimproved or has improved only slightly.

KEY CONCEPTS

Controlling Nonpoint PollutionRecognizing that nonpoint sources are a major source of wa-ter pollution, the U.S. Congress amended the Clean WaterAct in 1987. Under the amended law, the states were re-quired to identify nonpoint sources and draft plans to con-trol them. The EPA currently provides $200 million per yearin grant money to states to address nonpoint sources. Statesare required to partially match federal funds as well. This pro-gram has resulted in numerous successes.

Legislation to address water pollution has historically focusedon point sources—primarily factories and sewage treatmentplants. Gains made in controlling such sources, however, haveoften been offset by increasing levels of pollution from nonpointsources such as city streets, lawns, and farm fields.

Table 21-3Major Provisions of the U.S. Clean Water Act

PlanningThe states receive planning grants from the EPA to review theirwater pollution problems and to determine ways to solve themby reducing or eliminating point and nonpoint water pollu-tants.Standards DevelopmentThe states adopt water quality standards for their streams.These standards define a use for each stream and prescribe thewater quality needed to achieve that use.Effluent StandardsThe EPA develops limits on how much pollution may be re-leased by industries and municipalities. These limits are devel-oped at the national level based on engineering and economicjudgments. The EPA or the states are required to make the dis-charge limits for individual plants more stringent if necessaryto meet the state water quality standards.Grants and LoansThe EPA provides financial assistance to state water programs forthe construction of sewage treatment plants, processing of per-mit applications, monitoring of water quality, and enforcement.Dredge and Fill ProgramThe EPA develops environmental guidelines to protect wet-lands from dredge and fill activities. These guidelines are usedto assess whether permits should be issued.Permits and EnforcementAll industries and municipal dischargers receive permits fromeither the EPA or the states. The EPA and the states regularlyinspect these dischargers to determine whether they are incompliance with the permit and take appropriate enforcementactions if necessary.

Source: U.S. Environmental Protection Agency.

FIGURE 21-16 Sewage treatment plant. This photograph of asewage treatment plant shows the large, circular trickling filtersthat are used for secondary treatment.


SPOTLIGHT ON SUSTAINABLE DEVELOPMENT

21-1 Cleaning Up the Great Lakes

Carved by ancient glaciers, the five mammoth Great Lakeshold one-fifth of the world’s standing freshwater. Approx-imately 40 million people live within their drainage basin.Like so many of the continent’s waters, they have sufferedyears of abuse from pollution and poor land management.Especially hard hit were Lakes Ontario and Erie.

Cultural Stress: The Death of a Lake?The story of Lake Erie serves as a reminder of the immenseimpact of human civilization and as a lesson on ways to pre-vent future deterioration of the world’s waters. Lake Erie wasonce surrounded by dense forest. The healthy forests re-duced erosion and streams ran clean. Today, more than 13million people live in the lake’s watershed. The dense wood-lands that once protected the soil were cut down to makeroom for farms, homes, industries, and roadways. As a re-sult, large quantities of topsoil washed into the rivers andthe lake, clogging navigable channels and destroying spawn-ing areas essential to the lake’s once rich fish life. In theearly 1900s, many of the wetlands along the lake’s shore weredrained, and hundreds of small dams were built to providepower to mills, blocking the upstream migration of fishsuch as the walleye and sturgeon.

By the 1960s, the lake’s waters were polluted with a wideassortment of organic and inorganic nutrients. Raw sewagefloated on the water’s surface, and algal blooms (rapidgrowth of algae) were commonplace (FIGURE 1). Dissolvedoxygen levels frequently dropped to low levels, especiallyin the profundal zone that occupies the large central basinof the lake. Blue-green algae proliferated in the warm sum-mer months in the shallow western end of the lake, creat-ing a foul-smelling, murky green water. Lead, zinc, nickel,mercury, and other toxins from industry polluted harbors andbuilt up in nearshore sediments. In 1970 and 1971, mercurylevels in fish from Lake Erie often exceeded safe levels setby the U.S. Food and Drug Administration (FDA). Reductionsin mercury discharges in 1975 resulted in a decline in mer-cury in fish, but violations of health standards continue.

In colonial days, numerous fish species inhabited thelake and its tributaries. Largemouth and smallmouth bass,muskellunge, northern pike, and channel catfish were com-mon in the tributaries of the lake. Lake herring, blue pike,lake whitefish, lake sturgeon, and others lived in the openwaters. By the 1940s, however, blue pike and native lake

trout had vanished. Sturgeon, lake herring, whitefish, andmuskellunge managed to hold on, but in reduced numbers.

Lake Erie suffered from overfishing, introduction ofalien species, pollution, and destruction of shorelines andspawning grounds. Algal blooms, beach closings, thick de-posits of sludge, oxygen depletion, taste and odor prob-lems, and contaminated fish were the legacy of years ofdisregard and mismanagement.

By the late 1950s, large areas of Lake Erie’s centralbasin were anoxic (without oxygen) for weeks on end dur-ing the summer. Until the late 1970s, anoxia spread can-cerously. The lake was pronounced dead; many feared thatthe other lakes would follow suit.

The Joint Cleanup Program—Not EnoughAlarmed by the condition of Lake Erie and the other lakes,in 1972, the United States and Canada agreed to restrictthe discharge of pollution into the Great Lakes. The GreatLakes Water Quality Agreement, updated in 1978, calledfor controls of point and nonpoint pollution sources. It de-manded that releases into the lakes of “any or all persist-ent toxic substances” be “virtually eliminated.” Withcooperation from industrial and municipal polluters, thelakes began to show signs of recovery. Lake Erie, the shal-lowest and fastest flowing of the lakes, made a quick re-covery. Today, it is teeming with fish. Gone are the massive

FIGURE 1 Plant nutrients from sewage treatment facilitiescaused massive algal blooms in the Great Lakes.


algal blooms and the raw sewage discharges that oncediscolored the waters. The other lakes also show signs ofimprovement. In a recent report to the U.S. Congress, infact, Great Lake states reported on a survey that includednearly all of the nearshore waters. This report showed thatmost of the waters are now safe for swimming and otherrecreational activities, and much of it is clean enough fordrinking water.

Despite these efforts, 43 areas failed to meet the stan-dards established in the U.S.–Canadian accord a decade orso later. In 1987, a Buffalo-based environmental group,Great Lakes United, published a report noting that whilehighly visible and odoriferous pollutants such as sewage hadbeen significantly reduced, many toxic substances not vis-ible to the naked eye continue to pour into the Lakes. Forinstance, PCBs and pesticides still persist at unacceptablelevels. Officials administering the 1978 agreement con-ceded that the U.S. and Canadian governments had notfully lived up to its terms.

Toxicants enter the lakes from factories and sewagetreatment plants; from nonpoint pollution, including farm-land and urban runoff; from toxic fallout—that is, pollutantsdeposited from the atmosphere; and from resuspension ofsubstances contained in the bottom sediments, caused inpart when harbors and river mouths are dredged.

One of the most significant avenues of entry for tox-ins is atmospheric deposition. Trace metals, pesticides,phosphorus, nitric acid, nitrates, sulfates, sulfuric acid, andorganic compounds are all deposited from the air. Approx-imately 60 to 90% of all PCBs entering Lakes Superiorand Michigan come from the atmosphere. An estimated14,000 metric tons (15,400 tons) of aluminum is depositedin Lake Superior from the atmosphere, and nearly 29,000metric tons (31,900 tons) annually falls from the skies intoLake Michigan. The atmosphere is also a major source ofphosphorus, providing an estimated 59% of the total inputto Lake Superior. Without controls on atmospheric deposi-tion, it will be impossible to end the discharge of toxins intothe Great Lakes.

What does the continued pollution assault mean? First,commercial fishing, once an economic mainstay in the re-gion, has virtually ceased in all of the lakes except Supe-rior. Even there, the commercial fishers operate undercontinual uncertainty, never knowing when their catch will

exceed safe limits for contaminants and be declared unsafeby the FDA. Second, introduced Pacific salmon and rein-troduced lake trout survive in the lakes, but the salmon pop-ulation must be restocked each year. Lake trout do notreproduce successfully either, except in Superior. Restock-ing costs millions of dollars a year. Third, continued pol-lution has forced states to issue warnings advising womenwho are pregnant, lactating, or of childbearing age not toeat certain fish. Parents are also advised not to feed theirchildren lake-caught fish. This warning came after a sci-entific study on chronic low-level exposure, which showedthat infants of women who had eaten PCB-contaminatedfish two to three times a month were smaller, more slug-gish, and had slower reflexes than infants of women whohad not eaten contaminated fish. Children also accumulatethe toxicants, which may impact future fertility. Acceptablelevels for most of the 800 pollutants found in the lakes sim-ply have not been established, primarily because of a lackof information on health effects. In its report to Congress,the EPA noted that 97% of the nearshore waters of theGreat Lakes is under fish consumption advisory—meaningthe fish consumption is inadvisable or should be limitedto prevent health problems. PCBs are the main culprit.Aquatic life in these waters is also in jeopardy from bothtoxic chemicals that accumulate in the food chain andhabitat loss or degradation and competition and preda-tion by nonnative species such as the zebra mussel andsea lamprey.

Reducing the problems posed by toxic pollutants iscomplicated. Eight states, two provinces, numerous tribalcouncils, and two nations share an interest in managing thewaters of the Great Lakes. The result is often conflict thatholds up the important steps needed to bring the GreatLakes back to a full, productive, and healthy life. In 2002,20 years after starting cleanup efforts only 2 of the 43 ar-eas that failed to meet standards have been cleaned up. Twomore are said to be in recovery.

In recent talks, Canada and the United States agreedon ways to control airborne pollutants. They also agreed toremove contaminated sediments from the lakes and to bet-ter control groundwater pollution that contributes to thedegradation of the Great Lakes. At least 15 to 30 years ofrehabilitation are needed, but improvements are alreadybeginning to be seen. Clearly, there’s a long way to go.



and use of mulches to hold soil in place while grasses takehold along newly constructed highways and housing sites,are also essential. Laws that require sedimentation ponds tocollect runoff before it can reach streams and that requireporous pavements or porous pavers that soak up rainwatercould also help reduce erosion and the influx of pollutantsinto nearby water bodies.

KEY CONCEPTS

Preventing Groundwater Pollution Several federal laws givethe EPA the authority to prevent and control sources ofgroundwater pollution and to clean up polluted groundwa-ter. In 1984, the EPA adopted a formal groundwater protec-tion strategy that, among many things, established an Officeof Groundwater Protection. This strategy focuses on build-ing state capacity—that is, state regulation and control ofgroundwater. Under the plan, the EPA provides technicalassistance in analyzing problems and gives advice needed bystates to establish their own groundwater protection pro-grams. Unfortunately, say critics, states often lack the nec-essary funds, experience, and expertise. Nonetheless, manystates have adopted their own groundwater standards. Somehave taken preventive measures by mapping out aquifersand banning industrial development over them. Today, thevast majority of the states have developed programs that atleast minimally regulate discharges to groundwater. Clearly,much improvement is needed, especially in groundwaterpollution prevention.

In 1996, Congress toughened the U.S. drinking waterlaw by adding regulations that protect groundwater. Con-gress also recently passed legislation that requires the EPA toset standards for drinking water quality for 85 additionalchemical substances, including pesticides and various in-dustrial chemicals.

The new law requires drinking water suppliers to test forthese chemicals and to maintain the drinking water stan-dards. It also requires them to monitor drinking water sup-plies for other substances that might pose a threat to humanhealth. Even though the EPA is now monitoring these chem-icals, hundreds more could be monitored.

KEY CONCEPTS

Water Pollution Control Technologies:End-of-Pipe ApproachesThe first sewage treatment plant in the United States wasbuilt in Memphis, Tennessee, in 1880; today, there are over14,770 of them. Sewage entering a treatment plant often con-

The U.S. government and many states have done a better job ofaddressing groundwater pollution than nonpoint water pollutionbecause groundwater is an important source of drinking waterfor many communities.

In the United States, efforts to control nonpoint water pollutionare still in their infancy but are gaining in popularity becausethey are often economical solutions that offer other benefits aswell. Especially important are efforts to control agriculturalrunoff.

tains pollutants from homes, hospitals, schools, and indus-tries. It contains human wastes, paper, soap, detergent, dirt,cloth, food residues, microorganisms, and a variety of house-hold chemicals. In some cases, water from storm drainagesystems is mixed with municipal waste drainage systems tosave the cost of building separate pipes for each, which canbe exorbitant. Combined systems generally work well, but asnoted earlier, during storms inflow may exceed plant capac-ity. Consequently, some untreated storm runoff and sewagepass directly into waterways, raising the coliform count indownstream waters and rendering them unfit for swimming.Combined sewage overflows, as they are called, annuallyamount to 5 trillion liters (1.3 trillion gallons) according tothe EPA.

KEY CONCEPTS

Primary Treatment Sewage treatment can take place in threestages: primary, secondary, and tertiary treatment. Primarytreatment physically removes large objects by first passingthe sewage through a series of grates and screens. Sand, dirt,and other solids settle out in grit chambers (FIGURE 21-17). Thesolid organic matter, or sludge, settles out in a settling tank.

KEY CONCEPTS

Secondary Treatment The secondary stage destroysbiodegradable organic matter through biological decay (Fig-ure 21-17). Sludge from primary treatment enters a largetank, where bacteria and other organisms decompose the ag-itated waste. Another common way is to pass the liquid sludgethrough a trickling filter (FIGURE 21-18). Here, long pipes ro-tate slowly over a bed of stones (and sometimes bark), drip-ping wastes on an artificial decomposer food web consistingof bacteria, protozoa, fungi, snails, worms, and insects. Thebacteria and fungi consume the organics and, in turn, areconsumed by protozoans. Snails and insects feed on the pro-tozoans. Some inorganic nutrients—notably nitrates andphosphorus—are also removed during secondary treatment.

Secondary treatment is completed by a secondary settlingbasin, or clarifier, which removes residual organic matter. Inmost municipalities, liquid remaining after secondary treat-ment is chlorinated to kill potentially pathogenic bacteria andprotozoans and is then released into receiving streams, lakes,or bays.

The efficiency of primary and secondary treatment isshown in Table 21-4.

KEY CONCEPTSSecondary treatment further destroys organic matter and re-moves much of the nitrogen and phosphorus in sewage by em-ploying bacteria and other decomposers.

Primary treatment is a means of filtering out large objects andsolid organic matter.

Sewage treatment plants receive waste from many sources withincities, including homes, office buildings, factories, hospitals, and,in some cases, stormwater drainage systems.

Bar screen

Raw sewage

Air pump

Activatedsludge

Disposed of in landfillor applied to cropland,pasture, or rangeland

Sludge digester

Grit chamber

Primary settlingtank

Aerationtank

Sludge drying bed

Secondarysettlingtank

To stream

Chlorinationtank

Primary treatment

Secondary treatment

FIGURE 21-17 Sewage treatment. Primary and secondary sewage treat-ment facilities. The secondary treatment facility contains all of the com-ponents of the primary system but has an additional aeration tank (ortrickling filter) to further decompose organic matter.

Table 21-4Removal of Pollutants by Sewage Treatment Plants

Percentage Removed by Treatment

Primary and Substance Primary Secondary

Solids 60 90Organic wastes 30 90Phosphorus 0 30Nitrates 0 50Salts 0 5Radioisotopes 0 50Pesticides 0 0

FIGURE 21-18 Trickling filter. A decomposer food chain consist-ing of bacteria and other microorganisms in the rock or bark bedof this system consumes organic matter, nitrates, and phosphatesin the liquid sewage.



Solutions to global problems require new laws and tightercontrols. Critical thinking demands a search for additionalsystemic solutions. New technologies, for example, can helpreduce waste.

In making the transition to a sustainable society, consid-erable effort must be made to find solutions that strike at theroot causes. These strategies do not merely capture pollutantsbound for waterways and dispose of them in a slightly moreacceptable manner, in the process often contaminating an-other medium; they seek to prevent pollution in the first place.

Conservation, recycling, renewable resource use, andpopulation control are four forms of pollution prevention. Forexample, by using energy more efficiently, individuals andcompanies can reduce their demand for electricity. This, inturn, decreases the amount of cooling water needed by util-ities and cuts back on thermal pollution and pollution ofstreams and lakes with chlorine. Cooling systems are alsotreated with chemicals to keep organisms from clogging pipes.The less cooling water that is used, the less chemical pollu-tion of waters will result. Farmers can find many ways to cutback on their use of fertilizers and pesticides (Chapters 10 and22). Many techniques that are essential to creating a sus-tainable agriculture help control soil erosion (Chapter 10).These measures therefore reduce sedimentation and the re-lease of pesticides, inorganic plant nutrients, and organicchemical pollutants into surface and groundwaters.

Table 21-5 shows the dramatic reductions in water pol-lution possible from recycling aluminum, steel, paper, andglass. Because recycling these commodities also reduces air pol-lution—and because air pollution can become water pollutionthrough cross-media contamination—this strategy pays adouble dividend. A third payoff comes from the reduction ofmining wastes, which often make their way into streams.

In contrast to fossil fuel power plants, most renewableenergy sources such as photovoltaics and wind energy requirelittle if any water. Thus they produce little if any air and waterpollution. Population stabilization, of course, is the ultimatepollution prevention strategy. Each avoided birth means thatmuch less waste going into waterways.

The sustainable strategy also seeks to weave humanactions into the cycles of nature. That is, it attempts to return

Table 21-5Environmental Benefits Derived from Substituting Secondary Materials for Virgin Resources

Reduction of Use (percent)

Environmental Benefit Aluminum Steel Paper Glass

Energy use 90–97 47–74 23–74 4–32Air pollution 95 85 74 20Water pollution 97 76 35 —Mining wastes — 97 — 80Water use — 40 58 50

Source: R. C. Lechter and M. T. Sheil. 1986. “Source Separation and Citizen Recycling.” In The Solid Waste Handbook. W. D. Robinson, ed. New York: Wiley.

Tertiary Treatment Many methods exist for removingthe chemicals that remain after secondary treatment. Mostof these tertiary treatments are costly and therefore arerarely used unless water is being released into bodies of water that require a high level of purity—for example,Lake Tahoe in California. Fortunately, some cheaper optionsare gaining recognition. For example, effluents can be trans-ferred to holding ponds after secondary treatment, wherealgae and water hyacinths growing in the water consumethe remaining nitrates and phosphates. Certain aquatic plantssuch as duckweed absorb dissolved organic materials directly from the water.

Aquatic plants grown in sewage ponds can be harvestedand converted into food for humans or livestock. In Burma,Laos, and Thailand, duckweed has been consumed by farm-ers for years. The protein yield of a duckweed pond is six timesgreater than that of an equivalent field of soybeans. One ofthe problems with this approach, however, is that water hy-acinths and duckweed also absorb toxic metals from the wa-ter. Therefore, consumption by humans and livestock mustbe carefully monitored. Another approach is the use of arti-ficial wetlands, either indoors in greenhouses or outdoors.These were discussed in Chapter 13 and Spotlight on Sus-tainable Development 4-1.

KEY CONCEPTS

Sustainable Solutions for Water PollutionDespite an outpouring of laws to control pollution, the UnitedStates and other countries have hardly come to grips withthe problem. Tens of thousands of hazardous waste sites lit-ter the American landscape. Pollution control laws passedin the 1970s initially decreased water pollution nationwide,but since the early 1980s, pollution levels have remainedmore or less constant. Making matters worse, regulation andenforcement of hazardous-waste laws have been lax.

Tertiary treatment brings sewage wastewater near to drinking wa-ter quality but is rarely used because it is so costly.

nutrients to their site of origin or to utilize them for otherpurposes—for example, by using municipal sewage to fertil-ize crops. This approach is known as land disposal.

In ancient times, land disposal of human sewage wascommonplace; it is still practiced in many LDCs, such asChina and India. As the populations of LDCs grew andbecame more urbanized, this natural method of recyclingwastes was gradually phased out. Land disposal, discussedin Chapter 13 as a means of recharging groundwater, usesthe surface vegetation, soil, and soil microorganisms as a nat-ural filter for many potentially harmful chemicals. Sewagecan be piped to pastures, fields, and forests (FIGURE 21-19).Organic matter in the effluent enriches the soil and im-proves its organic content and ability to retain water. Ni-trates and phosphates serve as fertilizers. The water supportsplant growth and helps recharge aquifers. Crops nour-ished by effluents from treated sewage show a remarkableincrease in yield.

Land disposal of sludge from sewage treatment plants isnot a perfect solution. First, treated sewage may containharmful bacteria, protozoans, and viruses that could adhereto plants consumed by humans or livestock or become air-borne after the effluent dries. To get around this problem, theSwiss and Germans heat their sludge to destroy such or-ganisms before applying it to pastures and cropland. Alter-natively, sewage sludge can be decayed in compost pilesbefore application. The heat given off during compostingkills virtually all of the viruses, bacteria, and parasite eggs.

The second problem is that toxic metals found in somesewage may accumulate in soils and be taken up by plantsand livestock. Metal-contaminated sewage usually comesfrom industries. By removing metals from their waste stream(an option called pretreatment) or by finding ways to pre-vent them from entering the waste stream entirely (pollutionprevention), industries can eliminate the problem.

Third, transporting sludge to fields increases the cost ofsewage treatment, limiting some of the incentive to use thismethod. Experts are quick to point out, however, that landdisposal is 10 times cheaper than building and operating atertiary treatment plant.

Scientists at the University of Maryland recently devel-oped an unusual way to put sludge to good use. By combin-ing it with clay and slate, they formed odorless biobricks,which look like ordinary bricks. Washington’s Suburban San-itary Commission recently put the idea to the test by build-ing a 750-square-meter (8,300-square-foot) maintenancebuilding in Maryland with 20,000 biobricks. If successful,biobricks could help reduce land disturbance resulting frommining materials used for brick making—and could help cutsewage disposal costs and environmental contamination.

Restoration efforts can also help clean up water sup-plies. Direct efforts are needed to clean up groundwater, asnoted earlier in the chapter. In addition, restoration of wet-lands can help reverse the decline of aquatic systems. InFlorida, for example, drained swampland that was convertedto farms is now pouring vast amounts of plant nutrients intothe once massive Everglades. The native sawgrass that cov-ers much of this massive wetland is adapted to a nutrient-poorenvironment. In the presence of excess nutrients, cattailsare taking over, outcompeting the slow-growing sawgrass.To date, about 24,000 hectares (60,000 acres) of the Ever-glades National Park has been destroyed by cattails, whichare spreading at a rate of about 0.8 hectares (2 acres) a day.Debris from the plants rots in the water and creates anaero-bic conditions that kill fish and other aquatic species.

To reverse this trend, Florida officials have begun a mas-sive project to save the Everglades, called the Comprehen-sive Everglades Restoration Plan. Its measures includerestoration of swampland, pollution control facilities, pol-lution prevention, and removal of sediment from estuariesto restore sand-bottomed communities.

These are just a handful of steps needed to solve the wa-ter pollution dilemma sustainably. Of course, personal actionsare also needed. Limiting family size and reducing the con-sumption of unnecessary goods are important actions we caneach take. By reducing the purchase of goods, we can greatlyreduce hazardous waste production at factories. As a generalrule, each ton of garbage generated by consumers is precededby 5 tons of manufacturing waste and 20 tons of waste producedat the source (the mine or forest where the raw materials were

Water tableSedimentsand liquidsludge

Groundwater

Sewage

Water supply

City (10,000 people)

Marsh area(50 acres)

Forest area(100-200 acres)Forage crops

Cattle

Percolation

Pump

FIGURE 21-19Closing the loop. Land disposal of sewage helps fertilize farmlands and forests, reduce surface water pollution, and replenish groundwater supplies. This strategy helps prevent the pollution of surface waters.



acquired). So every savings we make, by buying less or by buy-ing more durable items, can effect large upstream savings inwaste and pollutants that might otherwise make their way intoour waterways.

Another effective way to cut your personal contribu-tion to water pollution is to install a composting toilet. Thecomposted wastes can be added safely to gardens, eliminat-ing the need for synthetic fertilizer. If and when you becomea homeowner, restrict your use of synthetic fertilizers, in-secticides, herbicides, bleaches, detergents, disinfectants,and other household chemicals—or find safe alternatives. Se-lect low-phosphate or nonphosphate detergents for wash-ing your clothes. You may also contact local and federalofficials to support further cleanup efforts.

KEY CONCEPTS

It is astonishing with how little wisdommankind can be governed when that littlewisdom is its own.

—W.R. Inge

Preventing pollution is a key to creating clean, healthy groundand surface waters, which are a prerequisite to living sustain-ably on the Earth. Efforts to reduce consumption; recycling ma-terials, industrial waste, and municipal sewage; using renewableresources; and stabilizing population growth—all of these willcollectively serve to reduce our production of water pollutants.

CRITICAL THINKING

Exercise AnalysisWater conservation in the home is designed to save water, but it has other benefits as well. For example, ithelps reduce energy demand because it takes energy both to pump water to treatment plants and to heat waterfor domestic use. The less water you use, the less energy is needed in your home and at the water treatmentplant. This in turn results in numerous environmental savings, from reduced habitat destruction from coal min-ing to less air pollution.

Water conservation in the home also means less water going down the drains to sewage treatment plants.That saves energy at the sewage treatment plant. It also reduces the demand for chlorine, which is used to dis-infect the effluent of sewage treatment plants. Can you think of any other benefits?

This exercise clearly shows how important it is to examine the big picture. Creating a sustainable future re-quires steps with multiple benefits. We need to conserve energy and reduce pollution wherever we can; so look ateach solution as an opportunity to solve several problems. Many people think that conservation means sacrifice,when in fact water conservation measures in the home can be quite inexpensive and easy to implement. Simplechanges in behavior—such as not flushing the toilet every time or watering your lawn less frequently—actuallyreduce your work. Conservation measures can save you money as well, which can be used to enhance your life.

CRITICAL THINKING AND CONCEPT REVIEW1. List the major types of water pollutants found in devel-

oping and developed nations. What are the major dif-ferences? Why do these differences exist?

2. Define the terms point source and nonpoint source. Givesome examples of each and explain why nonpointsources of water pollution are often more difficult tocontrol than point sources.

3. Describe where organic nutrients come from, what ef-fects they have on aquatic ecosystems, and how theycan be controlled.

4. What are inorganic plant nutrients, and how do theyaffect the aquatic environment? List some strategiesfor eliminating these pollutants.

5. Define the terms natural eutrophication and cultural eu-trophication. Describe how inorganic and organic nutri-ents accelerate natural succession in a lake.

6. What are the major sources of infectious agents in pol-luted water? How can they be controlled?

7. What are some of the major inorganic water pollutants?How do they affect the aquatic environment and hu-man populations?

8. Why is chlorine used in the treatment of human sewageand drinking water? What dangers does its use pose?How would you determine if the risks of chlorine useoutweigh the benefits?

9. What are the major sources of sediment, and how canthey be controlled? What are the costs and benefits ofsediment control?

10. A factory that has been polluting a nearby stream withtoxic wastes (volatile organic chemicals) has agreed to

stop. The owners are proposing the use of evaporationponds, where the wastes would sit until they evapo-rated. Using your critical thinking skills, your systems-thinking abilities, and your knowledge of waterpollution, critically analyze this proposal.

11. What are the major sources of groundwater pollution?How can groundwater pollution be reduced or elimi-nated? What can you do?

12. Discuss the sources of oil in the ocean and ways to re-duce oil contamination.

13. Critically analyze the following statement: “Oil natu-rally seeps into the ocean. In fact, about half of the oilin the ocean comes from natural sources. Because ofthis, it makes little sense to worry about spills fromtankers and other sources.”

14. Describe primary and secondary wastewater treatment.What happens at each stage, and what pollutants areremoved?

15. A housing development is being built in your town. Thedevelopers say that this project will not increase pollu-tion in the river that flows into the town because theywill pay to expand the town’s sewage treatment plant.Do you agree or disagree with their assertion? Why?

16. Pollution control devices are often viewed as stopgapmeasures. Why are such measures essential for long-term sustainability?

17. List and critically analyze all of the options availableto us to prevent pollution, such as population stabi-lization. Why are these approaches essential to thetask of building a sustainable society?

KEY TERMS biochemical oxygen demand (BOD)bioremediationchlorinated organicsClean Water Actcoliform bacteriumcross-media contaminationcultural eutrophicationfecal streptococcal bacteriagroundwaterinorganic nutrients

land disposalMedical Waste Tracking Actmetabolismmethyl mercurynatural eutrophicationnatural successionnonpoint sourcesOcean Dumping Ban ActOil Pollution ActPlastic Pollution Control Act

point sourcespretreatmentred tidesedimentsedimentationstreambed aggradationsurface watersthermal shockwater pollution

Connect to this book's website:http://environment.jbpub.com/9e/The site features eLearning, an online reviewarea that provides quizzes, chapter outlines,and other tools to help you study for yourclass. You can also follow useful links for in-depth information, research the differingviews in the Point/Counterpoints, or keep up on the latest environmental news.

REFERENCES AND FURTHER READINGTo save on paper and allow for updates, additional readingrecommendations and the list of sources for the informationdiscussed in this chapter are available at http://environment.jbpub.com/9e/.


Documents

CHAPTER 21 Water Pollution: Sustainably Managing