CHAPTER 11 Water Quality · Sci8_UnitD_Chap11.indd 288 10/24/08 8:53:55 AM. ... answers to the...

VOCABULARY

salinity

concentration

desalination

contaminant

fertilizer

herbicide

pesticide

turbid

thermal pollution

watershed

bioremediation

sewer system

blackwater

greywater

wastewater

stormwater runoff

CHAPTER

288 Chapter 11 • Water Quality NEL

Water Quality

KEY QUESTION: What substances are in water, and where do they come from?

Looking Ahead

Only a tiny fraction of the water on Earth is fresh water available for our use.

Water can contain many different contaminants.

The skills of scientifi c inquiry can be used to test water quality.

Water must be used sustainably.

Wastewater must be treated before being returned to the environment.

Research skills can be used to learn more about water issues.

11

Sci8_UnitD_Chap11.indd 288Sci8_UnitD_Chap11.indd 288 10/24/08 8:53:55 AM10/24/08 8:53:55 AM

Reading Science and Technology

Asha and her friends were enjoying the breeze off the lake. It was a hot day. Th ey wanted to swim in the lake, but a “Beach Closed” sign had appeared at their favourite swimming place. Th e water looked clean. What was the problem? Th e friends decided to go for a walk along the beach to see if they could discover why the sign was posted.

Th ey split into groups and sauntered along. Soon, some of Asha’s friends called her over to a low place in the sand. Dirty water was trickling into the lake from somewhere above the beach. Only a few metres out into the lake, the dirty water seemed to disappear as it mixed into the lake water. Perhaps this little stream was making Asha’s beach unsafe for swimming.

Th e friends followed the stream up from the shoreline. Th ey discovered an open pipe, the source of the dirty water.

Returning to the shoreline, Asha and her friends discussed how to fi nd out where the dirty water was coming from, and what they could do about it.

Pollution on the Beach

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....

289NEL

Making Connections: Text-to-WorldIn a small group, or with a partner, discuss possible answers to the following questions. Be prepared to present and defend your best answers to the class.

1 Asha and her friends decided not to swim at the beach that day because a sign had been posted. What signs have you recently seen that stopped you from doing something? Why had these signs been posted?

2 Do warning signs always give reasons for the warning? Why or why not?

3 If the sign had not been posted, do you think the friends would have gone swimming that day? Explain your answer.

4 The story does not give information about the source of the dirty water on the beach. Where do you think it might be coming from? Make a list of possible sources for the dirty water.

L I N K I N G T O L I T E R A C Y



Fresh Water and Salt WaterIf all the water on Earth were drinkable fresh water, it would be a very long time before we ran short of water (Figure 1). Unfortunately, most of the water is in the oceans, and it is salt water. Only 3 % of Earth’s water is fresh water—not salty—and most of that is deep under the surface or frozen in glaciers and polar ice. Only 0.4 % of Earth’s water is liquid fresh water at, or near, the surface. Even so, “fresh water” does not always mean “water suitable for drinking.”

Comparing Fresh Water and Salt Water How are fresh water and salt water diff erent? To begin to answer this question, consider the Dead Sea. Swimmers can fl oat in the Dead Sea with little eff ort (Figure 2). Th is is because the Dead Sea has a very high salinity—it contains a lot of dissolved salt. Salinity refers to the amount of salt dissolved in water. Salinity is expressed either as a percentage or as a concentration in g/L. Remember that concentration is the amount of solute in a particular volume of solution. Th e Dead Sea is a 30 % salt solution. Th erefore, the concentration of salt in the Dead Sea is 300 g/L.

In comparison, the average salinity of the world’s oceans is only 3 to 4 %. Th e salinity of any freshwater source (such as the Great Lakes) is less than 1 %.

Salt water has a greater density than fresh water (Figure 3). Objects that are more dense than a liquid will sink in that liquid; objects that are less dense than a liquid will fl oat in it. For example, the water in the Dead Sea contains so much salt that the water is much more dense than a human body. Th e high density of salt water allows swimmers to fl oat easily on the surface.

salinity: a measure of the quantity of dissolved salt in water

concentration: a measure of the quantity of dissolved substance contained per unit volume of solution

11.1

Figure 2 The salinity of the Dead Sea allows swimmers to fl oat. Figure 3 Fresh water (blue) is poured into a beaker containing salt water (red). Which is more dense?

Figure 1 About 70 % of Earth’s surface is covered in water.


11.1 Fresh Water and Salt Water 291NEL

DesalinationIs there a way to change salt water into fresh water? To answer this question, think about the changes of state that water undergoes as it moves in the water cycle.

Th e Try Th is activity shows us that only water evaporates from the oceans, leaving the solid salt behind. Th is is why rain is not salty!

Th ere are many places on Earth that have plenty of salt water but not enough fresh water to meet people’s needs. Engineers have developed ways to separate fresh water from salt water to solve this problem. Desalination is any process that removes salt from water, producing pure water and solid salt.

Some desalination technologies involve evaporating and then condensing water to remove the salt. Th is process requires a lot of thermal energy, which makes it very expensive compared to using fresh surface water or groundwater directly. Some desalination technologies involve using renewable energy sources, such as energy from the Sun (Figure 4), or geothermal energy.

A recent advance in desalination technology uses osmosis across a membrane with tube-like pores called nanotubes. Water particles can easily pass through the little nanotubes, but salt particles and other large non-water particles cannot.

desalination: the technology of removing salt and other minerals from water

TRY THIS: What’s Left Behind?

In this activity, you will compare what is left behind when a sample of salty water and a sample of tap water are left in open containers for several days.

Equipment and Materials: small graduated cylinder; 2 cups or small bowls; marker; teaspoon; warm tap water; 2 paper labels; salt

1. Measure 10 mL of warm tap water. Pour the water into one of the cups. Label the cup “tap water.”

2. Measure about half a teaspoon of salt into the graduated cylinder. Add warm tap water to the cylinder until the total volume of the solution is 10 mL. Swirl the salt-and-water mixture until the salt dissolves completely. Pour the salt solution into the second cup. Label this cup “salt water.”

3. Place the two cups in a warm place where they will be undisturbed for several days. Check on them periodically and record your observations.

A. What did you learn from your observations? Does salt evaporate along with water?

B. How could you use what you learned to change salt water into a source of drinking water?

SKILLS MENU: performing, observing

CHECK YOUR LEARNING

1. What percentage of water on Earth is fresh water?

2. Describe two special characteristics of salt water.

3. (a) Why are engineers developing desalination technologies? (b) Briefl y describe a desalination process.

4. (a) What can make desalination expensive? (b) Name two renewable energy sources that can be used in

desalination.

C

Figure 4 This solar power station in a desalination plant converts the Sun’s energy into electricity. The electricity is used to run the plant.

Go to Nelson ScienceGo to Nelson Science

To learn more about osmosis and nanotubes,

2.B.6., 6.A.2.2.B.6., 6.A.2.SKILLS HANDBOOK



Contaminants in Water Water is a very eff ective solvent; it can dissolve many substances. Land plants obtain most of their nutrients by absorbing nutrient-rich water through their roots. Aquatic plants obtain oxygen and carbon dioxide from water. Animals also benefi t from drinking water that contains dissolved minerals. However, toxic substances can dissolve in water, too. Unwanted substances that dissolve in water are called contaminants. Taking in water that contains contaminants can be hazardous to both plants and animals.

Sources of Chemical ContaminantsTh ere are many places where contaminants may enter the water cycle. Contaminants in the air can dissolve into precipitation that falls to Earth. Surface water and groundwater dissolve many chemical substances as they fl ow to the ocean. Th ese can include salt and toxic chemicals (toxins). For example, surface water fl owing across the Canadian prairies dissolves a great deal of salt. Water also dissolves minerals from soil and rock. Farmers in southern Ontario oft en add fertilizers to their fi elds to increase crop production. Fertilizers are substances that contain nutrients that help plants grow. Farmers and gardeners may use herbicides to kill weeds, or pesticides to kill unwanted insects (Figure 1). Surface water and groundwater dissolve these substances, which contaminate the water. Acid rain also aff ects water sources. Road, rail, and boat accidents can spill unwanted chemicals into the water supply.

SaltWe use road salt, gravel, and sand in the winter to prevent ice from forming on roads (Figure 2). Melting snow and rain wash road salt into ditches and streams. Road maintenance crews must store and use road salt carefully to prevent it from scattering into nearby forested areas or washing into surface water. Municipalities are studying and testing alternatives to scattering solid road salt. Spraying a concentrated salt solution is one alternative.

contaminant: an undesirable substance in a mixture

fertilizer: a substance used to provide nutrients to plants, usually for the purpose of increasing crop production

herbicide: a chemical substance used to kill or slow the growth of certain plants; often used to kill weeds that compete with crop plants

pesticide: a chemical substance used to kill animal pests; often used to kill insects that damage crop plants

11.2

Figure 2 Roads should be salted to prevent ice buildup only when needed.

Figure 1 Pesticides and herbicides are sometimes sprayed on crops from the air.


11.2 Contaminants in Water 293NEL

MineralsSurface water and groundwater both travel through various kinds of rock. Minerals from rock dissolve in the water. Limestone in southern Ontario is a soft rock that slowly dissolves in water, adding calcium carbonate to the water. Th e harder rock of the Canadian Shield is much less soluble and contributes few, if any, minerals to water.FertilizersSurface runoff can dissolve fertilizers in farm fi elds and carry them into streams and lakes. Fertilizers used on lawns and gardens can also enter surface water and groundwater. Fertilizers encourage the growth of tiny water plants called “algae,” just as they promote plant growth on land (Figure 3). When algae die, they decompose. Th e decomposition process uses oxygen, which reduces the amount of oxygen in the water. Th is can harm some fi sh populations because fi sh also need oxygen to survive.Herbicides and PesticidesHerbicides and pesticides are toxins intended to kill unwanted plants and animals. Not all of the toxins reach the target organisms. Excess herbicides and pesticides can dissolve into groundwater and surface water that may carry them to nearby waterways. Herbicides and pesticides can remain toxic for up to fi ve years before they are naturally converted into less harmful substances.

A popular pesticide used in the twentieth century was DDT. It was very eff ective at killing fl ies, mosquitoes, and potato beetles. DDT also had an undesirable eff ect: it caused birds to lay eggs with very thin shells. Th e shells broke before the chicks hatched, and bird populations suddenly dropped. Th e government was persuaded to outlaw the use of DDT in Canada. Since then, bird populations have recovered (Figure 4). It is encouraging to know that we can reverse some of the negative eff ects that we cause in the environment.

Figure 3 A sudden growth of algae in water is called an “algal bloom.” Algal blooms indicate that the water contains high concentrations of nutrients, often from fertilizers.

Figure 4 Since DDT was outlawed in the 1970s, the peregrine falcon has returned to its Ontario habitat.

Cause and EffectThe story of DDT describes a cause and effect text pattern. Take a moment to study this situation by

i• dentifying the cause

locating information about • the effect

refl ecting on people’s • reactions and the long-term impact on the environment

Work with a partner to discuss your fi ndings.


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Acid RainIndustries and vehicles that burn fossil fuels release many chemicals into the air. Some of these chemicals react with water vapour in the atmosphere to form acid rain. Acid rain can fall hundreds of kilometres away from where the chemicals are released, damaging land and aquatic ecosystems. Maple forests in Quebec and northeastern Ontario were damaged by acid rain in the twentieth century (Figure 5). Many organisms cannot live in water that is aff ected by acid rain.

Other Toxic ChemicalsTh e transportation industry is a major polluter of freshwater sources. Ships on the Great Lakes release pollutants when they empty ballast (stored water) or dump garbage and sewage. Th is is now illegal, but is diffi cult to enforce and still happens regularly. Accidental collisions of ships carrying chemicals or other harmful substances oft en result in spills. Train derailments and transport truck collisions can also release chemicals that can contaminate both surface water and groundwater.

Table 1 summarizes how some types of pollution get into our water.

Figure 5 Acid rain damage has cost the Canadian forestry industry hundreds of millions of dollars.

Table 1 Chemical Contaminants in Fresh Water

Pollution type Examples Sources Harmful effects

salt • naturally occurring salt

• road salt

• soil that contains salt• stored road salt• salt applied to roads

• kills crops or reduces yields• contaminates freshwater supplies,

making them undrinkable

minerals • carbonate • rock and soil• chemicals applied to farm fi elds

• none

nutrients • fertilizers • runoff from agricultural lands and urban areas

• industrial discharge

• stimulate growth of algae, which then decomposes, using up oxygen and harming aquatic life

toxic chemicals • PCBs• pesticides

• industrial sites• automobiles• farms and gardens• municipal wastewater• chemical spills

• mild immune suppression• acute poisoning• reproductive failure

acid • sulfuric acid• nitric acid

• acid rain from electric power generation, industrial stack, and auto/truck emissions

• chemicals from mining

• harms aquatic organisms• moves heavy metals from soils into

water bodies• damages trees

heavy metals • lead• cadmium• zinc• mercury

• industries• mines• landfi ll sites

• accumulates in the tissues of fi sh and shellfi sh

• toxic to animals and humans who eat them


11.2 Contaminants in Water 295NEL


To learn more about diseases transmitted in water,

Figure 6 Worms like these can grow inside the bodies of mammals, including humans.

Table 2 Biological Contaminants in Fresh Water

Pollution type Examples Sources Harmful effects

micro-organisms • Salmonella• E. coli• Giardia

• domestic sewage• cattle and other livestock• natural sources

• spreads infectious diseases through contaminated drinking water

organic matter • waste from cattle

• industrial wastewater• farm sewage

• uses up oxygen from the water as it decomposes, suffocating aquatic life

Sources of Biological ContaminantsSources of water are sometimes vulnerable to biological contamination and must be monitored closely. Surface runoff , for example, oft en mixes with farm manure in low-lying pastures. Manure can contaminate nearby water sources, such as aquifers, with dangerous bacteria. Th is was the case in 2000, when a deadly strain of E. coli contaminated the local water supply of Walkerton, Ontario, killing seven people.

Drinking water containing parasites can also cause illnesses. Parasites are organisms that get their nourishment by living inside, or attaching to, a host. All animals, including humans, can be aff ected by parasites. Some parasites are unicellular organisms too tiny for us to see; others are large enough to be seen easily (Figure 6). Parasites oft en enter water sources from feces excreted by infected animals. Runoff carries the contaminated feces into nearby bodies of water.

Giardiasis is a common parasitic infection in Ontario. It is caused by a parasite called Giardia, which infects mammals. Giardiasis is contracted by drinking untreated water. Th e infection causes nausea, cramps, or diarrhea.

Animal feces also add organic matter into the water system. Organic matter can smell bad as it decomposes, and it can harm aquatic animals by reducing the amount of oxygen in the water (Table 2).

CHECK YOUR LEARNING

1. Name two parts of the water cycle in which contaminants can be introduced.

2. (a) What are the two main categories of contaminants in water?

(b) Why are they a problem?

3. Choose two chemical contaminants that could be found in a freshwater source. For each one,

(a) identify a source of the contaminant (b) describe how the contaminant got into the water

4. Briefl y describe how a biological contaminant was able to get into groundwater wells at Walkerton.

C

Consider how you can use this information about contaminants as you plan to address your water issue for the Unit Task.Unit Task



Testing Water Quality Water quality is an important indicator of the health of a water system. How do we know if the water quality is good or poor?

TurbiditySediment (bits of solid matter) makes water turbid (cloudy). Clear water is usually of better quality than turbid water. You can see the turbidity of water simply by looking at it. Environmental scientists measure turbidity by slowly lowering a two-coloured disk into the water until it is no longer visible, and then recording this depth (Figure 1).

TemperatureWarm water contains less dissolved oxygen than cold water. If the water does not contain enough oxygen, aquatic organisms will die. Increasing the temperature of water by artifi cial means is called thermal pollution. Nuclear power plants and some industries use large volumes of water for cooling machinery. Th is warmed water is then returned to rivers and lakes (Figure 2).

Deforestation along a waterway reduces shade along the shoreline, which also causes thermal pollution. Th ermal pollution reduces the quality of the water.

AcidityWater becomes acidic if it contains certain dissolved chemicals, such as sulfuric acid or nitric acid. We can measure the acidity of water with an indicator that turns diff erent colours in acidic and basic solutions (Figure 3). Water is “acidic” if its pH is below 7 and “basic” if its pH is above 7. Good-quality fresh water has a pH between 6.5 and 8.5. Acid rain, industrial pollution, and chemical spills can aff ect the acidity of water. Most fi sh cannot reproduce in acidic water.

turbid: not clear; containing tiny specks of sediment or other solid matter

11.3

Figure 1 Scientists lower a disk called a “Secchi disk” into a lake to measure the water’s turbidity.

Figure 3 An indicator scale can be used to discover whether a sample is acidic or basic.

Figure 2 Nuclear power plants use lake water as a coolant.

thermal pollution: artifi cially raising the temperature (for example, of water)


11.3 Testing Water Quality 297NEL

CHECK YOUR LEARNING

1. List at least three factors mentioned in this section that decrease water quality.

2. How can you test a water source to see whether it is acidic or not?

3. What is thermal pollution? How do nuclear power plants contribute to thermal pollution?

4. How could each of the following substances enter a freshwater source?

(a) chlorine (c) calcium (b) nitrates (d) acid

C

Concept MapTo help you learn about water quality, draw a concept map. Start with the words “water quality,” then draw a line and write “turbidity.” Repeat this for each of the factors that affect water quality. Around each factor, make notes using lines and boxes. Write connecting words on the lines between boxes. Concept maps are a useful tool for boosting your learning.

L I N K I N G T O L I T E R A C YSalinityHow can you test for salt in water without tasting it? A conductivity apparatus is used to determine whether a solution can carry an electrical current. Salt water is a good conductor of electricity. Th erefore, testing a sample of water for conductivity will tell you whether the solution contains salt (Figure 4).

Other Dissolved SubstancesDissolved substances (solutes) in water include:

chlorine—added to kill unwanted organisms in drinking water• nitrates—from fertilizer runoff from fi elds, golf courses, and gardens• iron and copper—dissolved as water fl ows over certain rocks• calcium and magnesium—also dissolved from rocks, making the • water hardWe can use chemically treated paper test strips to show whether a

chemical is present in the water. Sometimes, we also need to know the quantities of solutes that are present. In the proper amounts, some of these solutes can be benefi cial. For example, chlorine is used in the water treatment process to kill harmful bacteria. However, too much chlorine can be toxic to animals. Other solutes, such as DDT, are toxic even in tiny amounts. What are the safe concentrations, and how much is too much?

If you choose to develop a technology to solve a water issue for the Unit Task, which of the water quality tests discussed in this section might be useful?Unit Task

Figure 4 The dissolved salt in the salt solution completes the circuit and lights the bulb. The fresh water contains no salt. It is not conductive, so its bulb does not light up.


To learn about maximum acceptable concentrations of solutes in water,



WatershedsGravity pulls surface water and ice downward. Water fl ows quickly downhill, but glacier ice fl ows very slowly. Th e direction of fl ow depends on the shape of the land.

The Continental DividesMost of the landmass that makes up North America was once below the current level of the oceans, and was covered by a shallow sea. Earth’s crust buckled and heaved over time, pushing the continent above the sea and forming mountain ranges. As the land rose, water slid down the sides of the rising ground. Th is fl owing water eroded the soil and rock, and helped to form the streams, rivers, and lakes of today.

Th e highest parts of North America are called the continental divides. Th ese areas of high land divide the waters (and ice) on each side, causing them to fl ow downhill in diff erent directions (Figure 1). Almost 80 % of Canada’s surface water fl ows north to the Arctic Ocean or northeast to Hudson Bay. Some fl ows west into the Pacifi c Ocean. Only a small fraction of our water fl ows toward the Great Lakes–St. Lawrence River region where most of the population lives. With the majority of Canadians sharing this limited resource, it is very important that we use water sustainably.

11.4

PACIFICOCEAN

ATLANTICOCEAN

ARCTICOCEAN

Gulf ofMexico

WE

N

S

HudsonBay

0 350 700 km

An extension of the Great Divide stretches northeast. It separates rivers flowing north (to the Arctic Ocean) from rivers flowing south

and east (to Hudson Bay and the Atlantic

Ocean).The Great Divide separates waters flowing into the Pacific Ocean from those flowing north and east.

A second extension of the Great Divide separates water flowing north (to Hudson Bay) from water flowing south and west (to the United States, the Great Lakes, and the St. Lawrence River basins).

Figure 1 The major continental divides of North America

Critical LiteracyRead Section 11.4. After reading, what do you feel is your responsibility toward protecting watersheds? What actions could you take to protect water where you live?



11.4 Watersheds 299NEL

Watershed Protection and CleanupIn southern Ontario and the northeastern United States, most surface water drains into the Great Lakes. Th is area is called the Great Lakes Basin. Th e Great Lakes Basin is an example of a large watershed—an area from which all water drains downhill to a common destination. Small watersheds oft en lie within larger ones. For example, the Grand River watershed consists of the land around the streams that fl ow into the Grand River, which in turn fl ows into Lake Erie. Th e Grand River watershed is therefore a part of the Great Lakes Basin.

Watersheds can be threatened in diff erent ways. Th e quality of water is damaged if it is polluted with contaminants. Th e volume of water can also be aff ected if rivers are dammed. Removing water, for industry or to sell as bottled water, can aff ect both surface water and groundwater. How can we protect our watersheds?Conservation AuthoritiesTh e Ontario legislature created 36 Conservation Authorities (CAs) in 1946 that protect and manage local watersheds (Figure 2). CAs act as caretakers of the watersheds, balancing human and economic needs with the needs of the natural environment. Th ey design, promote, and implement plans to protect and restore water systems within their watersheds. To accomplish this mission, CAs build partnerships with all levels of government, businesses, and residents. CAs reach their goals through education and provide advice on how to keep water clean, protect communities from fl ooding, and contribute to municipal planning processes. Watershed management is important to human communities and the environment.

watershed: an area surrounded by high land and drained by a river and its tributaries; all runoff from within the watershed leaves the watershed at the same exit

TRY THIS: Making a Continental Divide

In this activity, you will make a model to help you understand how water fl ows away from a continental divide.

Equipment and Materials: large plastic bowl; scissors; apron; graduated cylinder or measuring cup; mixing bowl or 1 L jug; spoon; plastic garbage bag; 2 m of string; duct tape; 700 mL cornstarch; water

1. Place the garbage bag in the large bowl so that the bag extends up the sides of the bowl and over the edges.

2. Cut the string into fi ve equal lengths. Take each piece of string and wrap one end once around a piece of duct tape before taping the string to the garbage bag. Attach the strings randomly to the inside of the bowl, but at least 10 cm from the edge of the bowl. Make sure that the free ends of the fi ve strings are draped over one side of the bowl.

3. Put on your apron. Use the graduated cylinder or measuring cup to measure fi rst 700 mL of cornstarch, and then 300 mL of water into the mixing bowl. Mix the cornstarch and water into a paste.

4. Holding the ends of the strings out of the way, carefully pour the paste into the plastic-lined bowl.

5. Gently pull the strings upward to make “mountain peaks” rise out of the paste “sea.” Be careful not to pull the strings so far that the “sea” fl ows out of the bowl! Try pulling some strings more than others. Observe what happens to the “sea.”

A. Describe what “land forms” you made.

B. What was the effect of raising and lowering the strings?

C. How well does this model represent the real continental divides? Explain your answer.

SKILLS MENU: performing, observing, evaluating

Figure 2 Conservation Authorities employ many people. One of their jobs is to teach young citizens about our water resources.

2.B.8., 6.A.2.2.B.8., 6.A.2.SKILLS HANDBOOK



Remedial Action PlansTh e Great Lakes form a chain of large bodies of fresh water that lie on the Canada–United States border. Th e Great Lakes became more and more polluted throughout the twentieth century. In 1987, Canada and the United States signed Th e Great Lakes Water Quality Agreement. Each country identifi ed pollution “hot spots” (areas of concern) in the Great Lakes Basin. Th e countries enlisted the support of nearby communities to protect the watershed. Together, they developed local remedial action plans (RAPs) for each of the hot spots. Each RAP is designed to set goals and

guide restoration projects (Figure 3). Th e hot spot is “de-listed” by both governments when the goals of the action plan are met. BioremediationOrganisms that “feed” on specifi c pollutants can be used to break pollutants down and remove them from the environment.Bioremediation makes use of organisms to help correct pollution problems. Figure 4 shows bacteria that have been added to a pond contaminated with oil from a nearby oil well. Th e bacteria convert the oil into carbon dioxide and water.

Micro-organisms cannot decompose metals such as mercury. Th ese metals enter the bodies of organisms and are passed on to other organisms through the food chain. Because of this, metals consumed by micro-organisms stay in the environment. Aquatic plants, however, can be used to remove metals from the environment. As aquatic plants grow, their cells accumulate the metals. Removing the contaminated plants removes these toxins from the water.

Wetlands work as natural water-cleaners, removing bacteria, waste solids, and excess nutrients from the water. Protecting natural wetlands is one step toward sustainability for our water systems. It is oft en less expensive to protect wetlands than it is to build modern water treatment facilities. Specially designed wetlands are being used in some areas of Europe to treat wastewater (sewage).

bioremediation: the use of living things (micro-organisms, fungi, and green plants) to remove contaminants from a polluted environment

Figure 3 Not long ago, the St. Clair River was one of the most polluted areas within the Great Lakes Basin.

Figure 4 Bioremediation can take place in isolated treatment tanks or in the natural environment.

CHECK YOUR LEARNING

1. (a) Describe how a continental divide affects the direction of water fl ow over land.

(b) Name a continental divide, and describe where it is.

2. Explain the meaning of the term “watershed.”

3. Briefl y describe the role of a Conservation Authority.

4. What is the process called in which organisms are used to remove contaminants from the environment?

5. Describe, with an example, how each of the following organisms removes contaminants from water:

(a) micro-organisms (b) plants

C


To fi nd out more about bioremediation,


SCIENCE

301NEL

Protectors of the Watershed

Keeping a close eye on Ontario’s water quality is a challenge. Most southern Ontario watersheds are monitored by Conservation Authorities (CAs), which act to conserve and manage natural resources. The Ontario Ministry of Natural Resources, the Ministry of the Environment, and Environment Canada all work with local CAs to protect the sustainability of watersheds in that area. CAs promote community involvement and facilitate projects to restore water quality (Figure 1).

Conservation offi cers who work for these groups have a wide range of tasks, including measuring water levels and taking water samples. Engineers, computer programmers, physicists, chemists, and biologists work together. Protecting water also involves talking with politicians to help develop laws, and educating the public. Towns and cities need help to plan new building projects. Watersheds provide a steady water supply to nearby urban areas and must be carefully managed. Farmers with bodies of water on their farms must understand how to protect the water (Figure 2).

Laws are in place to protect our water. Unfortunately, not everyone follows the laws. The Ministry of the Environment deals with pollution, as well as with other water quality issues. Conservation offi cers enforce laws by charging and fi ning people who pollute or damage the water. In many areas, the local Conservation Authority is the fi rst place to turn if you notice a violation. Watershed management programs aim to protect our natural resources for future generations.

Figure 2 Ontario farmers need to take care of the water on their property.


To learn more about Conservation Authorities,

Figure 1 Ontario has 36 local Conservation Authorities.


EXPLORE AN ISSUE CRITICALLY


Farm Practices and Surface-Water Pollution Imagine that you have just graduated. You have been given the opportunity to take over the family farm in rural Ontario. Th e farm is located in a watershed under the management of a Conservation Authority. It is a farm that produces both crops and livestock (Figure 1).

You visit the farm to learn more about its day-to-day operation. Your cousin, who has been running the farm, is pleased to show you around and explain everything. You learn that the farm relies heavily on fertilizers to produce good crop yields. Th is heavy use of fertilizers contradicts what you learned about water quality in your science courses. You voice your concerns about fertilizers contaminating the water. In response, your cousin gives you copies of articles from a local newspaper, an issue of a Canadian environmental magazine, and brochures from the fertilizer manufacturers.

The IssueYou have received confl icting information. Th e Conservation Authority clearly recommends using smaller quantities of fertilizer than the farm is currently using. Local newspaper articles celebrate the township’s donation of grain to developing countries. Th e environmental magazine seems to give a more balanced perspective, but does not strongly recommend reducing fertilizer use. You note that one of the fertilizer companies is an advertiser in the magazine. Th e manufacturers’ brochures quote studies that show signifi cant increases in crop yields when the fertilizer is used. You suspect, however, that the studies were funded by the fertilizer manufacturers.

11.5

Figure 1 Farms that raise livestock and grow crops are called mixed farms.

Defi ning the Issue Researching Identifying Alternatives Analyzing the Issue Defending a Decision Communicating Evaluating

SKILLS MENU


11.5 Explore an Issue Critically 303NEL

GoalTo decide whether it is possible to run the farm and grow crops using fertilizers without damaging the quality of the water in the area. To accomplish this goal, you will have to judge the accuracy of the information that you collect from a variety of resources.

Gather InformationWork in small groups to gather information from a variety of media sources before making a decision. Research how fertilizer is applied and the percentage of a fertilizer application that aff ects plant growth and crop yield. Use what you have learned about surface-water runoff and watersheds. Learn about the components of fertilizer and the eff ect that these components may have on water systems. As you gather information, look for evidence of bias.


Identify SolutionsAnalyze the various perspectives on the use of fertilizers to increase crop yields. Consider possible management strategies that will benefi t production while minimizing potential harm to nearby water systems.

Make a DecisionDecide whether it is possible to run the farm and grow crops using fertilizers without negatively impacting the local watershed.

If you came across confl icting information, consider these questions:

Why might there be diff erent positions on this issue?• What diff erent groups are represented in the sources you fi nd?• Who is the intended audience of each source?• Who provided the information to each source?• Use this information to help you make a decision about this issue.

CommunicateExplain your position in a letter to your cousin. In your letter

give reasons for your position, focusing on the pros and cons of • using fertilizers refer to information that you have researched• suggest a plan for the farm that would • give acceptable crop yields while minimizing the harm to nearby water systems

3.I., 7.C.3.I., 7.C.SKILLS HANDBOOK

Critical LiteracyLook for objective information when you research any topic. The information should be factual and free from bias. (Biased information supports one side of an issue and ignores other perspectives.) Objective information is not infl uenced by the emotions, personal opinions, or benefi t to the writer or publisher. Compare the information on crop fertilization provided by a Conservation Authority to information provided by a fertilizer manufacturer.


You considered a very important water quality issue in this section. How does this relate to the water issue you are considering for the Unit Task?Unit Task



PurposeTo test water, from a minimum of three separate sources, for the presence of dissolved substances.

Equipment and Materials eye protection• apron • graduated cylinder (25 mL)• thermometer• conductivity apparatus• micro test tubes• micro test tube rack or beaker• marker• masking tape• samples of water • distilled water• pH test strips• other test strips (nitrate, chlorine, hardness)•

Water TestingWater quality is important to industries, environmentalists, government agencies, aquarium owners and retailers, gardeners, and homeowners. Th e health of a municipal water supply and its freshwater source aff ects the water’s quality. Poor water quality poses a health threat to people who drink water from that source. Economic development also suff ers if the quality of the water is poor. Th is is because treating water aft er it has been polluted is oft en more costly than preventing the pollution in the fi rst place.

Th ere are many water quality tests available. In this activity, you will test water from diff erent sources, such as tap water, bottled water, and water from a local river or lake. You will then compare your results.

11.6 PERFORM AN ACTIVITY

Questioning Hypothesizing Predicting Planning Controlling Variables

Performing Observing Analyzing Evaluating Communicating

SKILLS MENU

eye protection

masking tape

conductivity apparatus

apron

samples of water distilled water

other test strips (nitrate, chlorine, hardness)

pH test strips

micro test tubes

graduated cylinder (25 mL)

markermicro test tube rack or beaker

thermometer


11.6 Perform an Activity 305NEL

Procedure1. In your notebook, construct an observation

table similar to Table 1. Your teacher will tell you which tests you will be doing. Write the names of the tests at the top of the columns.

Table 1 Observation Table for Testing Water Samples

2. Put on your eye protection and apron. 3. Obtain a 25 mL sample of water from one of

the samples. Write the source of your sample in the left -hand column. Measure and record the temperature of the water.

4. Test the water sample with the conductivity apparatus. If the bulb lights up, then the water contains salt. (Remember that salt water is a good conductor of electricity.) Rinse the conductivity wires in distilled water aft er using them. Record your observations.

5. Collect one micro test tube for each test that you will be doing. (For example, if you will be testing for pH, hardness, nitrate, and chlorine, collect four test tubes.) Be sure to label your micro test tubes with the name of the test.

6. Pour an equal volume of water into each micro test tube.

7. Add a pH test strip to the water in the fi rst test tube (Figure 1). Record your observations in your table. Pay particular attention to any change in the test strip or the water sample.

8. To each of the remaining test tubes, add the appropriate test strips. Record all observations.

9. Repeat steps 3 to 8 with the samples of water from other sources.

Analyze and Evaluate(a) Interpret your observations. Which

contaminants were present in each sample?(b) Comment on the water quality of each

sample. (c) You know where each sample came from.

Suggest explanations for any diff erences in water quality among the samples.

Apply and Extend(d) You only tested for a few possible substances

that could have an impact on water quality. Could you tell from your observations whether any of the contaminants present would pose health risks to humans drinking the water? Explain.

(e) Research ways to determine water quality other than using test strips or conductivity apparatus (Figure 2). Describe one of the methods that you researched.


6.A.4.6.A.4.SKILLS HANDBOOK

2.B.7.2.B.7.SKILLS HANDBOOK

Temperature TestsSource (°C) conductivity pH hardness nitrate chlorinetap 8 no light 7 X X

Figure 2 Water testing is an important part of many people’s careers.

Figure 1 Step 7

Will you have to address water quality in the Unit Task? Can you use the tests you learned about in this activity in the Unit Task?

Unit Task



Wastewater TreatmentYou have already learned that human activities, such as farming and transportation, can aff ect surface water (Section 11.2). What about your everyday activities—all those “water uses” that you listed in Section 10.1? What happens to dirty water that fl ows down the drain when you fl ush the toilet or wash your clothes? Th is water goes into either a sewer system or a septic system, depending on where you live. Most homes in towns and cities are connected to a sewer system. A sewer system is a series of underground pipes that carries “used” water to a wastewater treatment facility (Figure 1).

sewer system: a network of pipes that transports dirty or used water

11.7

1

3

4

1. Preliminary Treatment

2. Primary Treatment3. Secondary Treatment

4. Final Treatment

chlorine

digester

river orlake

clarifier

wastewater

primary settling tank

grit tank

landfill

farm fertilizer

incineration

5. Solids Processing

heating and electricity

1. Preliminary TreatmentWastewater passes through a bar screen, which removesobjects such as sticks, rocks, and garbage. The wastewateris slowed down as it enters the grit tank to allow sand, gravel, and other heavy materials to settle to the bottom. Debris from the bar screen and grit tank is trucked to a landfill.

2. Primary TreatmentThe wastewater flows into a primary settling tank where it isheld for several hours. Solid particles settle to the bottom ofthe tank.

3. Secondary TreatmentNext, a biological treatment process removes organic matter from the wastewater. Adding oxygen encourages micro-organisms to grow and eat the organic matter. This is the same as the natural decomposition process—only sped up. Any remaining solids settle to the bottom of the clarifier.

4. Final TreatmentThe wastewater is disinfected with chlorine to kill harmful organisms. The clean water is then released into Lake Ontario.

5. Solids ProcessingThe primary solids from the primary settling tank and the secondary solids from the clarifier are sent to the digester. Micro-organisms use organic material in the solids as food and convert it to methane gas. This gas can be used to produce electricity or to heat the plant. After 15 days in the digester, bio-solids (wet, soil-like material) are sent to the landfill or are incinerated. Bio-solids are high in nutrients, such as nitrogen and phosphorus, and can be used as fertilizer.

Figure 1 This diagram shows the wastewater treatment process in Toronto.


To look at an interactive diagram of a typical wastewater treatment facility,


11.7 Wastewater Treatment 307NEL

Water containing feces and urine—oft en called blackwater—is fl ushed directly into the sewer. Water from bathing, washing machines, and sinks is called greywater. Greywater and blackwater are both types of wastewater. Wastewater is any used water (carrying waste) that has been discharged from homes, businesses, and industries.

Cities also have to handle stormwater runoff —the rainwater and snowmelt that runs off roofs, paths, and roads. Stormwater can carry road salt, pesticides, animal waste, and other contaminants. Stormwater runoff joins the wastewater in the sewers of some cities (Figure 2(a)), but other cities keep stormwater separate from wastewater (Figure 2(b)). Th is means that there is less water that has to be cleaned.

Th e treatment plant removes most of the contaminants before returning the cleaned water to the environment.

Not all wastewater goes to municipal treatment systems. Homes and small businesses in rural areas commonly have septic systems that treat their wastewater on a much smaller scale. A septic system includes a septic tank and a drainage bed (Figure 3). Solids are trapped in the septic tank, where bacteria slowly digest the wastes. Liquid fl ows to the drainage bed, where it gradually soaks into the ground.

blackwater: water that contains feces and urine; also called “sewage”

greywater: water that has been used for cooking, laundry, bathing, or similar tasks

wastewater: water that has been used or contaminated by human activity; blackwater and greywater

stormwater runoff: water, usually from precipitation, that runs off roofs, lawns, and paved areas

residential(single-family andmultiple-family)

industrial

stormwater

wastewatertreatment

facilityrivertreated

blackwaterand greywater

combined

Figure 2 Combined sewers use one pipe to carry all wastewater to treatment plants (a). However, during wet weather, the volume of water may exceed the treatment plant’s capacity and some of the wastewater overfl ows, untreated, into the river or lake. Storm sewers use a separate pipe to carry stormwater directly into nearby rivers, streams, and brooks (b).

septic tankdistribution

boxdrainage bed

inlet

sludgescum and

grease

outlet

Figure 3 A typical septic system

(a) (b)

CHECK YOUR LEARNING

1. Explain in your own words how greywater is different from blackwater.

2. List two sources of wastewater.

3. What is the purpose of the primary stage of sewage treatment?

4. Explain the difference between a septic system and a sewage system.

C

residential(single-family andmultiple-family)

industrial

stormwater

wastewatertreatment

facilityrivertreated

untreated

blackwaterand greywater

combined


EXPLORE AN ISSUE CRITICALLY


Wastewater Reduction At the beginning of this unit, you tracked and recorded your water consumption over a period of 24 hours. In a follow-up activity, you created an action plan to reduce your water consumption. You may have made the connection that, as you reduce the volume of clean water that you use, you also reduce the volume of wastewater that you produce.

All water leaving our homes should be treated before it is released into the environment (Figure 1). Fast-growing communities sometimes exceed the capacity of their water treatment facilities. When too much wastewater arrives at a treatment facility, some water bypasses the facility. Th is untreated water fl ows into the natural environment. Th is has serious health and environmental consequences.

The IssueYour community wastewater treatment facility is having diffi culties meeting the demands of the growing population. Th e local town council has asked you to design an advertising campaign that will encourage people living in the community to reduce the amount of wastewater produced.

Your campaign should explain how the community currently manages wastewater. It should also outline the main concerns regarding wastewater and suggest ways to address these concerns in an environmentally friendly way.

Goal To design an advertising campaign that will encourage people to reduce the amount of water going to the wastewater treatment facility.

11.8

Figure 1 Cities must make sure that the wastewater treatment facilities are adequate.

Critical LiteracyDo you believe that each citizen should be responsible for dealing with wastewater? Is each citizen in your area dealing with wastewater in an environmental way? Why do you think this is? Discuss in a small group or with a partner.


Defi ning the Issue Researching Identifying Alternatives Analyzing the Issue Defending a Decision Communicating Evaluating

SKILLS MENU


11.8 Explore an Issue Critically 309NEL

Gather InformationIt is important to know how and where wastewater is generated in your community. Where does all the wastewater come from? Where does it go?

Find out what happens to rainwater that runs off your roof. Does some of it fl ow into downspouts and then down your driveway and into a sewer grate? Where does rainwater go aft er landing on parking lots and streets? Does water from all these sources end up at the water treatment facility, or does it go directly back into the environment and fi nd its way into freshwater sources? What are the concerns surrounding wastewater, and how can they be dealt with?


Identify SolutionsConsider the challenges faced by your local wastewater treatment facility. Th ink about the volume of water that ends up at the facility and all the sources of this water. How could the total volume of wastewater be reduced? Can any of the water be diverted or reused (Figure 2)? Try to develop solutions to your local problem. Your solutions

must be environmentally friendly • should not be too expensive • could involve the support of the local community•

Make a DecisionDevelop a plan to ease the pressure on your local wastewater treatment facility. When developing your plan, consider what points you will present to the public. How will your campaign encourage people to reduce the amount of wastewater they produce?

Communicate Present your campaign to the class (who will act as members of the public). Explain how wastewater is currently managed in the community and what the concerns are. Explain how your plan will address these concerns. Be prepared to support your plan with evidence.

Your campaign may take the form of a television spot, a photo essay, a cartoon strip, or a T-shirt graphic. Remember, the more creative your advertising is, the more people will remember it!

3.J.4., 3.J.5.3.J.4., 3.J.5.SKILLS HANDBOOK

8.8.SKILLS HANDBOOK

Figure 2 Some cities are encouraging homeowners to divert rainwater from house roofs into rain barrels. The water can then be used for lawns and gardens.

How does wastewater reduction apply to the water issue you are considering for the Unit Task?Unit Task



Looking Back

CHAPTER

11Water Quality

SUMMARY

✓✓

BIG Ideas

Water is crucial to life on Earth.

Water systems infl uence climate and weather patterns.

Water is an important resource that needs to be managed sustainably.

✓

✓

Only a tiny fraction of the water on Earth is fresh water available for our use.

Most of Earth’s water is in the oceans and is salt water. Th is makes • the water unsuitable for drinking.Only 3 % of Earth’s water is fresh water. Most of this is frozen in • glaciers or polar ice, or deep underground. Desalination processes have been developed to remove salt from • water to meet people’s need for clean drinking water. Th ese processes use a lot of thermal energy and can be expensive.

Water can contain many different contaminants.

Water dissolves many substances, including toxic chemicals.• Water can contain fi ne solids that make the water turbid.• Human activities result in many contaminants entering the water. • Th ese include the use of fertilizers, herbicides, and pesticides in farming, and the use of chemicals in industry. Road salt also contaminates water. Biological contaminants are organisms that are harmful to other • living things. Drinking water containing harmful organisms and parasites can cause serious health problems.


VOCABULARY

salinity, p. 290

concentration, p. 290

desalination, p. 291

contaminant, p. 292

fertilizer, p. 292

herbicide, p. 292

pesticide, p. 292

turbid, p. 296

thermal pollution, p. 296

watershed, p. 299

bioremediation, p. 300

sewer system, p. 306

blackwater, p. 307

greywater, p. 307

wastewater, p. 307

stormwater runoff, p. 307

Chapter 11 Summary 311NEL

The skills of scientifi c inquiry can be used to test water quality.

Test strips and solutions can be used to test water samples for the • presence of chemicals.Conductivity apparatus can indicate the presence of salt in water.• Water test results can be used to compare the quality of diff erent • water samples.

Water must be used sustainably.

Th e highest areas of land on Earth are called the continental • divides. Th e waters on each side of the divides fl ow downhill in diff erent directions toward bodies of water. Th e areas between the divides are called watersheds.Conservation Authorities manage and protect watersheds. Ontario • has 36 Conservation Authorities.Remedial Action Plans are in place to improve the water quality in • seriously polluted areas. Technologies such as bioremediation are becoming increasingly important in restoring polluted areas.

Wastewater must be treated before being returned to the environment.

Wastewater in cities is transported from its source to a water • treatment facility through a sewer system. In rural areas, wastewater is sometimes treated in septic systems. Most contaminants are removed before the water is returned to the environment.Wastewater includes blackwater (feces and urine), greywater (used • water from domestic processes), and stormwater (rainwater and snowmelt runoff ).

Research skills can be used to learn more about water issues.

Analysis skills can be used to assess how diff erent media sources • address issues related to water systems.



CHAPTER

11 REVIEW K/U Knowledge/Understanding T/I Thinking/InvestigationC Communication A Application

The following icons indicate the Achievement Chart categories:

What Do You Remember?1. In your own words, defi ne “salinity” and

“concentration.” K/U

2. How does a continental divide aff ect the fl ow of water? K/U

3. (a) What is a watershed? (b) Explain how a stream can be part of more

than one watershed. K/U

4. Write a sentence that includes the term “bioremediation.” K/U C

What Do You Understand?5. Describe the diff erence between a water table

and a watershed. K/U 6. Why might a farmer apply the following to a

fi eld of tomato plants?(a) fertilizer(b) herbicide(c) pesticide K/U

7. Describe the possible eff ect of each of the following activities on a freshwater source:(a) the application of road salt to melt snow

and ice on winter roads(b) transportation by ships K/U

8. Draw a diagram showing a wetland as a system, with contaminated water as the input and clean water as the output. K/U C

9. (a) Explain the term “wastewater.”(b) Identify three sources of wastewater in

your community. K/U A

10. Many parts of the Great Lakes watershed are polluted. Pollution “hot spots” have been identifi ed, along with remedial action plans to fi x each one.(a) What is a remedial action plan?(b) How do you know when a remedial action

plan is complete and the identifi ed hot spot cleaned? T/I A

11. Research and describe one situation where bioremediation was successful in returning a polluted water source back to its natural condition. T/I A


Solve a Problem!12. Trout need high concentrations of oxygen in

the water. Where would you fi sh for them in summer: near the surface or in deep water? Explain your answer. T/I A

13. (a) Describe turbid water.(b) Describe two methods you could use to

remove the turbidity from water. T/I A

Create and Evaluate!14. You have learned about the process of treating

wastewater to produce clean water that can be returned to any freshwater source. Create an illustrated story about a water particle called Potty Water. Sketch the changes that Potty Water sees as the particle goes through each stage of sewage treatment. T/I C

15. Draw a cartoon or a fl ow chart to show the stages of municipal water treatment. K/U C

16. Nature has its own way of cleaning chemicals from water. Soil fi lters surface water as it is absorbed into the ground to become groundwater. Wetlands and marshes contain both plants and micro-organisms that clean runoff before returning the water to streams and rivers. Research information about a community that has successfully created an artifi cial wetland. Write their story for a school newspaper. Remember to present the story objectively. T/I C



Chapter 11 Review 313NEL

17. Th e following appeared on the website of an environmental organization.

Rouge Park Stream Disaster

The Morningside Tributary is the last tableland trout stream in Toronto. It is part of the Rouge Park and it provides habitat for nationally rare red-side dace. Between 2001 and 2003, a 1400 m reach of the Morningside Tributary was destroyed to allow developers to fi ll and build homes within the fl ood plain area.

Rampant Fish and Wildlife Habitat Destruction

To redesign the fl ood plain, developers were permitted to divert and channelize the stream, gouge out a deeper but narrower fl ood plain, fi ll former fl ood plain areas, and reconstruct the stream.

The developers also received permission to remove all the trees, shrubs, vegetation, topsoil, and living things for a width of 100+ m and a length of 1400+ m along this Rouge Park stream. Many fi sh and wildlife were killed or displaced, including a family of beavers, which were shot.

Government Complicity

Shockingly, the City of Toronto, Ontario Municipal Board, federal Department of Fisheries and Oceans (DFO), and the Toronto and Region Conservation Authority (TRCA) reviewed and “permitted” the developers’ proposals without a public environmental assessment of alternatives. They boldly and incorrectly predicted “no signifi cant adverse environmental effects with the implementation of mitigation.”

Source: Friends of the Rouge Watershed

(a) What is the purpose of this piece of text? (b) How does the writer attempt to achieve

this purpose? Does the writer succeed?(c) Describe the position of the writer. What

evidence do you have of this position? (d) Why might diff erent readers react

diff erently to this text? T/I A

18. You are an environmental technician working for a Conservation Authority. A report has come in that a factory may be aff ecting the quality of water in a river. You have been sent to measure the temperature of the water and to test it for pH and salinity. (a) Briefl y describe how you would gather

your data.(b) Analyze the observations in Table 1, and

write a brief report about the quality of the water in the river.

(c) Is there enough evidence here to conclude that the factory is polluting the river? Explain your answer. T/I C A

Refl ect on Your Learning 19. (a) List four new ideas that you have learned

in this chapter.(b) Which of these ideas is the most diffi cult

for you to understand? Why?(c) Plan and carry out a strategy to help you

understand this diffi cult idea.(d) Share your responses with a classmate.

20. Th ink back to the Key Question on the fi rst page of this chapter.(a) In a brief paragraph, answer the Key

Question. You may use diagrams.(b) Write one or two more questions about

the topic of this unit that you would like to explore.

Table 1 Observations of Three Water Samples

SampleTemperature

(°C) Average pHConductivity

(X or √)

#1 9.9 5.3 X

#2 10.3 5.5 X

#3 9.7 5.5 X

To do a self-quiz Go to Nelson Science


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