Lesson Pollution Solutions

Learning Objectives

After this lesson, students should be able to:

• Describe and explain how a scrubber, an electrostatic precipitator, a cyclone and a baghouse work as pollutant recovery methods.
• Give examples of when the use of a scrubber, an electrostatic precipitator, a cyclone or a baghouse is appropriate.
• Describe how engineers create technology to help industry clean up their air pollution.

Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

NGSS: Next Generation Science Standards - Science

International Technology and Engineering Educators Association - Technology

State Standards

Worksheets and Attachments

Introduction/Motivation

Ask students to suggest ideas to the following questions: How would you clean up air that is dirty with dust, particulate matter and gases? Would you establish any laws? Who would the laws impact: industries, small businesses, citizens? Write their ideas on the chalkboard.

Hopefully, the student suggestions include "washing the air" and, perhaps, using a filter. If not, prompt them by asking how nature cleans the air, and what happens to all the dirt and dust that is suctioned up by a vacuum. Discuss what they think should happen if somebody releases a large amount of pollution into the air.

The Clean Air Act of 1970 regulates how much of any pollutant can be released into the air. Two kinds of pollutants are regulated under the Clean Air Act. One type, called "criteria" pollutants, includes these six pollutants: carbon monoxide, nitrogen dioxide, sulfur dioxide, ozone, lead and particulate matter. Criteria air pollutants are discharged in relatively large quantities by a variety of sources, and they threaten human health and welfare across broad regions of the country. The U.S. Environmental Protection Agency (EPA) sets national standards for each of the criteria pollutants, and the states must take action to ensure the standards are met. Failure to meet the standards is called "nonattainment." Many urban areas are classified as "non-attainment areas" for at least one criteria air pollutant. The Clean Air Act establishes "enforcement" methods that can be used to make polluters obey the laws and regulations. Enforcement methods include citations (like traffic tickets), fines and jail terms for violators of the law. As the goals of the law are met, we breathe cleaner air every year.

The most common methods of eliminating or reducing pollutants to an acceptable level are: destroying the pollutant by thermal or catalytic combustion (burning the air), changing the pollutant to a less toxic form or collecting the pollution with equipment to prevent its escape into the atmosphere. Explain to the students that in this lesson they will investigate four air pollution cleaning methods developed by environmental engineers and used in industry: scrubbers, electrostatic precipitators, cyclones and baghouses.

Lesson Background and Concepts for Teachers

One of the biggest challenges environmental and chemical engineers face is devising new techniques to prevent the creation of additional air pollution. Manufacturing and industry are large contributors to air pollution. In this lesson, students take on the role of engineers and experiment with four different methods for cleaning up industrially-polluted air. To do this, conduct four of the activities listed in the Associated Activities section in sequence to model the four technologies used to reduce industrial air pollution: Washing Air: Wet Scrubber Pollutant Recovery Method (wet scrubber), Cleaning Air with Balloons (electrostatic precipitator), A Merry-Go-Round for Dirty Air (cyclone) and Cleaning Air Like a Vacuum Cleaner: Let's Bag It (baghouse).

Industrial Cleaning Methods

Air contaminants are emitted into the atmosphere as particulate matter, aerosols, vapors or gases. The most common methods of eliminating or reducing pollutants to an acceptable level are: destroying the pollutant by thermal or catalytic combustion, changing the pollutant to a less toxic form or collecting the pollution with equipment to prevent its escape into the atmosphere. Pollutant recovery may be performed by the use of one or more of the following: scrubbers, electrostatic precipitators, cyclones and/or baghouses. Each technology has its own advantages and disadvantages; it's important for engineers to evaluate the constraints of each technology, as well as the ability for each option to control air pollution. Figure 1 presents the advantages and disadvantages of each technology.

Natural Cleaning Methods

There are also a number of natural ways to clean the air, including:

• Hurricanes (violent tropical storms of rain, lightning, thunder and high winds)
• Tornadoes (violent, funnel-shaped windstorms that are very destructive)
• Raindrops, snowflakes and other precipitation events remove air pollution through the natural water cycle (although this can lead to water and land pollution)
• Plants (especially spider plants)
• Mucus inside our noses traps the dirt and germs from the air before they reach our lungs. If the air is really dirty it cannot stop all the pollution, so some of it may reach and damage our lungs (i.e., smoking effects).

Clean Air Act

To help reduce air pollution, over the years, our government has passed many laws, called the Clean Air Act. The first Clean Air Act was passed in 1963. The Clean Air Act tells people everything they must do to reduce air pollution. Several Clean Air Acts have been passed since 1963. The most recent one was passed in 1990. (For more information, see the attached Clean Air Act Reading.)

Associated Activities

• Cleaning Air with Balloons - Students observe and discuss a simple balloon model of an electrostatic precipitator to better understand how this pollution recovery method functions in cleaning industrial air pollution.
• Cleaning Air Like a Vacuum Cleaner: Let's Bag It - Students observe and discuss a vacuum cleaner model of a baghouse to better understand how this pollution recovery method functions in cleaning industrial air pollution.
• A Merry-Go-Round for Dirty Air - Students observe and discuss a cup and pencil model of a cyclone to better understand how this pollution recovery method functions in cleaning industrial air pollution.
• Washing Air: Wet Scrubber Pollutant Recovery Method - Students observe and discuss a simple model of a wet scrubber to better understand how this pollution recovery method functions in cleaning industrial air pollution.
• What's a Kid to Do? Environmental Letter Campaign - In this literacy activity, students write letters as part of an environmental action campaign. They become more aware of global environmental problems and play a part in their solution.

Lesson Closure

Write on the chalkboard the following information on the four air pollutant removal methods explored in the four activities in the Associated Activities section:

Baghouses: 99.9% efficiency

Cyclones: 95% efficiency

Electrostatic precipitators: 99.9% efficiency

Wet scrubbers: 95% efficiency

Ask the students the following questions to help clarify their understanding of the industrial air pollutant recovery methods in use today, and discuss as a class:

• Does a wet scrubber clean up all of the pollutants? (Answer: No, it removes 95% of them.)
• Do any of these cleaning methods remove all pollutants from the air? (Answer: No. They range from 95-99.9% efficient.)
• Which type of air cleaning process would be the best for removing particles? Which method is most efficient? (Answer: The baghouses and precipitators are the most efficient.)
• Which method is least efficient? (Answer: Cyclones.)
• Which type of air cleaner would be the best for removing waste gases? (Answer: Wet scrubbers work better on acidic, basic or corrosive gasses. Cyclones work better on other gases.)
• When might one type of pollutant recovery method be better than another? (Answer: It would depend on the type of pollutant(s), cost, location, etc.)
• If the baghouses and precipitators are the most efficient, why would you ever want to use a wet scrubber or cyclone? (Answer: It depends on the type of pollutant(s) and the industrial conditions. Wet scrubbers work better on acidic, basic or corrosive gases with high water solubility. Cyclones are best at removing solid pollutants from dust-laden gases.)
• What problems arise by having too many pollutants in the air we breathe? (Answer: The most important problems are adverse health effects.)

Have the students complete the attached Cleaning Up Worksheet – Four Methods to summarize their understanding of the various pollutant recovery methods explored in the activities.

Read the attached Clean Air Act Reading.

Explain to students that during this lesson they have only considered industrial changes and technologies for controlling air pollution. Ask for suggestions about what we can personally do to control and/or prevent the amount of air pollution that we cause? Conduct the literacy activity, What's a Kid to Do? Environmental Letter Campaign, for this lesson and/or assign the attached Clean Air Act Worksheet and Letter as homework.

Vocabulary/Definitions

baghouse: A pollutant recovery method that works very much like a giant vacuum cleaner. Heavy dirt particles fall out and are removed, and smaller particles are trapped by filters (bags) made of cloth, paper or similar materials. Particles are shaken or blown from the filters into a collection hopper.

cyclone: A pollutant recovery method in which dust-laden gas is whirled very rapidly inside a cylinder-shaped collector. Flying dust particles (as well as all matter) like to travel in straight lines unless an external force acts upon them. Because of this, pollutant particles with inertia in a cyclone tend to leave the circular path of the cyclone, collect on the wall, and then slide down the wall into a collection chamber.

electrostatic precipitator: A pollutant recovery method in which a static charge makes dirt particles stick to electrified plates (much the same way that static electricity in clothing attracts small bits of dust and lint). The dirt is knocked loose, collected and removed.

hopper: A funnel-shaped chamber in which materials are collected temporarily and later discharged through the bottom.

scrubber: A pollutant recovery method that traps solid particles and gases as they pass through a fine water mist inside the scrubber. Sometimes the mist is injected with limestone powder to help extract the dirt particles.

Assessment

Pre-Lesson Assessment

Brainstorming: As a class or in small groups, have the students engage in open discussion. Remind students that in brainstorming, no idea or suggestion is "silly." All ideas should be respectfully heard. Take an uncritical position, encourage wild ideas and discourage criticism of ideas. Have them raise their hands to respond. Write their ideas on the board. Ask the students:

• How would you clean up air that is dirty with dust, particulate matter and gases?

Post-Introduction Assessment

Class Discussion: Ask the students and discuss as a class:

• Can you think of any ways that nature helps clean up the air? (Answer: Hurricanes, violent tropical storms with rain and high winds, tornadoes, raindrops/snowflakes/other precipitation remove air pollution through the water cycle, plants [especially spider plants], and mucus inside our noses traps some of the dirt and germs from the air before they reach our lungs.)
• Do you think engineers use nature as a model for the air cleaning technologies they design? (Answer: We will find out as we learn about industrial air cleaning methods.)

Lesson Summary Assessment

Drawing/Journaling: If your class conducted all four pollutant recovery method activities, have students complete the attached Cleaning Up Worksheet – Four Methods to capture their observations and summarize their understanding of the various methods. Otherwise, depending on the students' age, have them draw a picture or write in their own words a description of how the studied industrial air cleaner methods clean air. Ask for volunteers to share their descriptions with the class.

It's a problem all over the world! Imagine that you are an engineer at a meeting of great leaders from around the world. They are waiting to hear you speak about what is happening to our fresh air. You want to convince more of them to begin using the new technologies that you have just studied. What will you tell them? How will you get them to work together? Write down your ideas.

Now What? Have the students brainstorm about what to do with the pollutants that are removed from the air with the pollution recovery methods investigated in the activities of this lesson.

Homework

Clean Air Act: Have students complete the Clean Air Act Worksheet and Letter, which asks them to describe what they would include in their own "clean air act" and write a letter to the National Clean Air Coalition about what they have learned.

Lesson Extension Activities

If you have the time and ability to let the students build the models described in the Associated Activities section, consider having one group build a different model and present it to the class. Have students research the Clean Air Act. What is it? What is the goal? When was it started? Have students compare the U.S. to other countries in its air quality and regulations for controlling air quality.

Assign students some of the lesson concepts to research on the Internet. Lead a small discussion of the findings during the next class period.

References

Copyright

Contributors

Supporting Program

Acknowledgements

The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.