Materials Included In Kit

Safety Precautions

See the safety precautions section in the student section. Wear chemical splash goggles, chemical-resistant apron and chemical-resistant gloves. Please review current Safety Data Sheets for additional safety, handling and disposal information.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. Reacted samples may be disposed of according to Flinn Suggested Disposal Method #26b.

Teacher Tips

• Enough materials are provided for a class of 30 students working in pairs or 15 groups of students.
• One color comparison chart is provided for each test. Have students share each color comparison chart. Lab stations may be setup for each test.
• Tap water samples from other locations may be collected in a clean, glass or plastic container with a lid. Handle the samples in a manner that will prevent any physical changes or chemical reactions.
• It is wise to test the samples within one hour of collection if possible.
• If a test sample reaction is darker than the darkest color on the color chart, the concentration of the sample is greater than the test range of the test. Combine equal parts of the sample water and distilled water. Follow the test procedure with the water sample that has been diluted. Then multiply the test result by two.
• TesTabs are a vendor product of the LaMotte Company. SDSs are available through the manufacturer website. Links to the specific TesTabs used in this kit are listed.
  Chlorine — http://www.lamotte.com/pages/common/pdf/msds/6899.PDF
  Wide Range — http://www.lamotte.com/pages/common/pdf/msds/6459.PDF

Further Extensions

Have students write reports on a certain pollutants, their sources and effects. Encourage students to use the Internet to explore the wide range of water pollution information available.

Test drinking water samples from different locations. Have students compare and contrast the results.

Introduce and discuss real-life examples of pollution. A good example is the water pollution that occurred on the Cuyahoga River. The Cuyahoga (which eventually empties in to Lake Erie) is a river that runs through Akron and Cleveland, Ohio. In the 1950s and 60s, chemical and steel factories dumped up to 155 tons a day of toxic chemicals, sludge and solvents into the river. The river was also bombarded with animal manure, pesticides, fertilizers, and raw and poorly treated sewage. In 1959, oil slicks from these substances caught fire and burned for a total of eight days. Firefighting measures only complicated the situation. As water was sprayed from the fire hoses the blaze was spread even further. Ten years after this incident the river caught fire once again. These incidents were strong factors leading to the passage of the Clean Water Act in 1972.

Take a field trip to a water treatment facility. Discuss the pollutants covered in this activity as well as other factors monitored by the treatment facility.

Answers to Questions

1. What are the two main types of water pollution? Define each type and list examples.
   Point specific pollution and nonpoint pollution. Point specific pollution is contamination that comes from a specific location. An example of point specific pollution is a factory that has a chemical discharge pipe that leads directly to a water source. Nonpoint pollution does not come from a specific location. Some examples are runoff of water from city areas, agricultural land, or from poor forestry practices.
2. List possible sources and effects of each of the pollutants in this activity.
   See Background section (answers may vary).
3. Compare and discuss your results with the accepted values given in the Background section of this handout for each factor tested in this activity.
   Answers will vary depending on results.
4. Compare your values to your classmates’ values for each of the pollutants.
5. What can be done to help minimize the amount of pollutants in your local tap water?
   Answers will vary.
6. Would you describe your tested water source as polluted or non-polluted? Defend your answer.
   Answers will vary.

Discussion

Here are the reactions that take place for each sample:

Chlorine: Chlorine DPD #4R TesTabs contain diethyl-p-phenylenediamine (DPD). When chlorine oxidizes DPD, a pink color is formed in proportion to the chlorine concentration.

Iron: Total iron TesTabs contain bipyridyl. The ferric ion is reduced to ferrous ion and forms a colored complex with bipyridyl that can be used for the overall quantitative measure of total iron.

Copper: Copper Testabs contain zincon. Zincon chelates with copper to produce a blue color. When copper is not present in solution no color is present.

pH: pH wide range TesTabs contain mixed pH indicators which are sensitive to pH and undergo specific color changes with variation in pH.

References

Cunningham, W. P.; Woodworth, S. B. Environmental Science A Global Concern; William C. Brown: Dubuque, IA, 1995; pp 424, 429, 430.

Mitchell, M. K.; Stapp, W. B. Field Manual for Global Low-Cost Water Quality Monitoring; Kendall/Hunt: Dubuque, IA, 1997; pp 29, 35, 36, 47.

Sarkis, V. J. Chem. Educ 1974, 51, 745–747.

Introduction

What types of pollutants are in our water? How do these pollutants affect us? In this activity, the amount of pollutants in drinking water will be tested.

Concepts

• Chemical pollution
• Sources of pollution
• Water quality
• Effects of pollution

Background

Water is an essential resource for humans. It is used for almost every activity in life and is required for life itself. In fact, water is the main component in cells and it composes up to 60 to 70 percent of the weight of living organisms. Water is needed for agricultural and industrial use, drinking, transportation, and in recreation. Water often seems to be available in an almost endless supply, but as populations rise and our world becomes increasingly industrialized, more and more water is being used. With this extensive use of water, a problem arises—the water becomes polluted and contaminated. This pollution leads to a strain on water’s ability to recycle and cleanse itself of contaminants. It is now estimated that over one billion people are unable to obtain adequate drinking water. The amount of water available, its distribution, and its quality are critical issues that continue to affect all life. An increasing awareness of the need to monitor the quality of water and to locate the sources of pollution is becoming more prevalent in today’s society.

Roughly half the population of the United States (95% of the population in rural areas) depend on underground aquifers as a source of drinking water. Aquifers are water bearing, porous layers of gravel, sand and rock below the Earth’s surface that contain and hold groundwater. The overall quality of water found in underground aquifers is being increasingly threatened by both pollution and overuse. Pollution of aquifers is a major threat to the quality of drinking water due to the fact that it generally takes hundreds, up to thousands of years for deep aquifers to totally replenish their water supply. In addition, once many types of pollutants enter underground water supplies they become very stable. This stability of underground pollutants also increases the longevity of aquifer pollution problems.

There are two main ways pollution enters drinking water supplies. They are known as point specific pollution and nonpoint pollution. Point specific pollution is contamination that comes from a specific location. An example of point specific pollution is a factory that has a chemical discharge pipe that leads directly to a water source. This type of pollution can be pinpointed and limited much more readily than the second class of pollutants, nonpoint sources.

Nonpoint water pollution does not come from a specific location. Some examples are runoff of water from city areas, agricultural land or poor forestry practices. This type of pollution occurs when runoff water such as snowmelt or rainfall travels over an area of land. As this water moves over the ground, it picks up waste and carries it to a body of water. This water enters rivers and will seep down through the soil and eventually enter the groundwater supply. This type of pollution can be difficult to pinpoint and eliminate.

As polluted water enters the groundwater supply, the concentrations of certain pollutants may alter drinking water’s purity. If the concentration of a pollutant reaches a certain level, the water could become hazardous to human health. The following is a list of some common pollution indicators and how they affect our tap water:

Chlorine—Chlorine is not naturally found in water. It is added to public water systems and swimming pools as a bactericide. Chlorine in drinking water supplies is generally maintained under 0.75 parts per million. Large levels of chlorine introduced to streams, lakes, rivers and ponds can be harmful and possibly fatal to aquatic organisms.

Total Hardness—Hardness is a measure of the amount of calcium and magnesium in water. Both calcium and magnesium may originate from soils or from commercial and industrial wastes. Water with a low level of hardness is referred to as soft water, and water that contains a high level of calcium and magnesium is termed hard. Hard water can cause a wide variety problems in industrial and home water systems. The main effects of hard water are scaling in pipes and appliances, and also a decrease in the effectiveness of soaps and laundry detergents. Water with a range of 0 to 60 parts per million of total hardness is considered soft, 60 to 120 parts per million medium hard, 120 to 180 parts per million hard and 180 parts per million and above is considered extremely hard.

Iron—Iron, in small amounts, is an essential nutrient to humans and other organisms. It is present in water from natural sources such as rocks and soils and it is also found in water due to industrial waste and the corrosion of iron pipes. When the concentration of iron is above 0.1 parts per million, it will precipitate as iron oxides when it comes in contact with air. Iron oxides will stain laundry, plumbing fixtures and silverware. It will also cause food and drinks to taste and look peculiar. Iron concentrations in drinking water should not exceed 0.3 parts per million.

Copper—Copper is present in water from sewage or industrial waste. It is also added to reservoirs and ponds to control the amount of aquatic vegetation. Even though copper is essential in small amounts to the human body, excessive amounts can result in liver damage. If concentrations of copper are above 1 part per million, drinking water may taste bitter. In general, the amount of copper found in drinking water is below 0.03 parts per million, but it may reach up to 0.6 parts per million in certain places.

pH—The pH test is a standard analysis of water testing. pH refers to the relative abundance of hydrogen ions in a water sample. The pH scale has a range of 0 to 14 where 7 is neutral, values lower than 7 are acidic, and values greater than 7 are basic. Most aquatic organisms require a pH range between 6.5 and 8.2. Waters with abundant algae and vegetation growth usually have a significantly high pH. This is due to the fact that rapidly growing algae and vegetation remove carbon dioxide from the water during photosynthesis.

Experiment Overview

In this activity, the quality and the amounts of pollutants in tap water will be tested.

Materials

Safety Precautions

Chlorine DPD #4R TesTabs, Copper HR TesTabs and Total Iron TesTabs contain chemicals that may irritate skin, or be harmful if swallowed. pH wide range TesTabs contain trace amounts of dyes and inert fillers. The TesTab reagents used in this kit were designed with safety in mind. The single-use, foil packaged TesTabs are easy to dispense. Store TesTabs in a cool, dry place and only open when ready to use the tablet. A single tablet, either alone or reacted with a sample, is not a health hazard. However, TesTabs should not be ingested. Wear chemical splash goggles, a chemical-resistant apron and chemical-resistant gloves. Please review current Safety Data Sheets for additional safety, handling and disposal information.

Procedure

Part 1. Chlorine Test

1. Fill the water sample tube to the 5-mL line with the tap water sample.
2. Add one Chlorine DPD #4R TesTab to the water sample tube.
3. Cap the tube and mix the solution until the tablet has dissolved.
4. Compare the color of the sample to the Chlorine color comparison chart. Record the findings as parts per million in the data table.
5. Dispose of the reacted sample according to the instructor and rinse the water sample tube twice with the water sample for the next test.

1. Fill the water sample tube to the 14-mL line with the tap water sample.
2. Dip the Total Hardness Test Strip into the water sample.
3. Compare the test strip to the Hardness color comparison chart listed on the bottle. Record the findings as parts per million in the data table.
4. Dispose of the reacted sample according to the instructor and rinse the water sample tube twice with the water sample for the next test.

1. Fill the water sample tube to the 5-mL line with the tap water sample.
2. Add one Total Iron TesTab to the water sample tube.
3. Cap the tube and mix the solution until the tablet has dissolved.
4. Wait for five minutes.
5. Compare the color of the sample to the Iron color comparison chart. Record the findings as parts per million in the data table.
6. Dispose of the reacted sample according to the instructor and rinse the water sample tube twice with the water sample for the next test.

1. Fill the water sample tube to the 10-mL line with the tap water sample.
2. Add one Copper HR TesTab to the tube.
3. Cap the tube and mix until the tablet has dissolved.
4. Compare the color of the sample to the Copper color comparison chart. Record the findings as parts per million in the data table.
5. Dispose of the reacted sample according to the instructor and rinse the water sample tube twice with the water sample for the next test.

1. Fill the water sample tube to the 10-mL line with the tap water sample.
2. Add one pH Wide Range TesTab to the water sample tube.
3. Cap the tube and mix until the tablet has dissolved.
4. Compare the color of the sample to the pH color comparison chart. Record the findings as parts per million in the data table.
5. Dispose of the reacted sample according to the instructor and rinse the water sample tube twice with the water sample.

Student Worksheet PDF

11918_Student1.pdf