1. Air Pollution and Air Pollution Control

2. Air Troposphere “ambient air” nearest to Earth's surface
weather occurs here
Properties:
approximately 80% of the atmosphere's mass
99% of its water vapor and aerosols
average depth of approximately 17 km (11 mi) in the middle latitudes
deeper in the tropics, up to 20 km (12 mi)

3. Air Troposphere Stratosphere Three more layers above
Ozone here is considered a pollutant
Stratosphere
situated between about 10 km (6 mi) and 50 km (30 mi) altitude
location of protective ozone layer: absorbs high energy UV B and UV C energy waves from the Sun
Three more layers above

4. The Earth’s Atmosphere
Earth's Atmosphere Has Changed Dramatically since the Time it was Formed
some changes the result of chemical and physical characteristics of the earth and the gases

5. The Earth’s Atmosphere: Current Theory of Evolution of Atmosphere
Early Earth
no oxygen at that time
Instead high in CO2, H2O vapor, and probably NH3, H2 and CH4
Now
considerable reduction in CO2; significant increase in O2
If true,
Where did the “C” of CO2 go?

6. Current Composition of Atmosphere
0.9% Ar
0.04% CO2
trace amounts of gases, vapors, particulates
naturally occurring: Ne, He, Kr, Xe, H2, CH4, O3, N2O
these have remained relatively constant for at least several hundred million years

7. Current Composition of Atmosphere
whatever humans emit is considered ‘trace amounts’
– example CFC = %
But still can have a significant impact

8. Atmosphere Bombarded by Solar Radiation: Greenhouse Effect Keeps Earth Warm
Some is reflected back to space by stratospheric ozone or clouds while others penetrate

9. Air Pollutants

10. Air Pollution
Accumulation of substances in the atmosphere that can cause harmful health effects to living things or can negatively affect the public welfare
Fate - Matter cannot be created nor destroyed, it only changes form:
Pollutants just don’t disappear, they may
Dilute - Dispersion
Change form - Degradation
‘Sink’ – Deposition, Transfer to other compartments

11. Effects of Air Pollutants
Wildlife health including forests
Impact on agriculture
Buildings and other property
Visibility and navigation
Human health effects:
Irritation of the respiratory passages including nose, throat, trachea and bronchii
Eye irritation
Increased susceptibility to the common cold
Neural disorders (from toxics like lead)
Other toxic effects

12. Air Pollution Sources
Anthropogenic
Geogenic
Biogenic

13. Anthropogenic Sources
Stationary Sources
Stack emissions
Fugitive emissions
Major stationary sources
Small sources
Mobile Sources
Accidental spills

14. Air Pollutant Types and Sources
Energy-related?

15. (ozone related)

16. Other Sources
Geogenic
volcanoes
dust storms

17. Other Sources Biogenic decomposition gases
organic molecules released from plants and animals
Pollen
Insect parts
cow gas?

18. Progress Being Made?

19. Other Pollutants Hazardous Air Pollutants (HAPS)
asbestos, benzene, mercury, vinyl chloride, radionuclides, numerous others
Each has its own sources and effects
Toxicity/carcinogenicity, persistence, and bioaccumulation the key issues

20. General Air Pollution Control Strategies
Source Shutdown
Source Location
Fuel Substitution and Process Changes
Very successful with autos
Correct Operation and Maintenance, Efficiency
Emissions Trading
‘End of Pipe’ Pollution Control Technologies

21. ‘End of Pipe’ controls
Consider only after other options are exhausted?
Selection heavily regulated by environmental statutes

22. Pollution Control Technologies
Form of substance dictates control technology used
Gases/vapors
Particulates
Physical and chemical properties of the pollutant also dictate which particular methods will be effective

23. Control Technologies Various levels of control technologies exist
Examples:
Best Available Control Technology (BACT)
Lowest Achievable Emissions Rate (LAER)
Ultimately, choice depends on:
Form of contaminant
Regulatory requirements for a particular industry
Quantity generated
Installation costs
Maintenance and operational costs

24. Characteristics of Pollutants
Physical state
Particulate Size (µm)
Size distribution of particulates
Density
Reactivity

25. Characteristics of Carrier Gases
Flow rate (cfm)
Moisture content
Temperature
Flammability

26. Particulate Emissions Control
Common control devices include
Settling chambers
Cyclones
Wet scrubbers
Electrostatic precipitators
Fabric filters (baghouse filters)

27. Settling Chambers

28. Cyclones

29. Wet Scrubbers

30. Electrostatic Precipitator

31. Baghouse Filters

32. Gaseous Emissions Control
Four Major Techniques
Adsorption
Absorption
Condensation
Combustion

33. Adsorption
Attachment of gas/vapor to a solid

34. Absorption
Dissolving gaseous pollutants in a liquid

35. Condensation Removal of gas or vapor by condensing it into liquid form
Uses changes in temperature and/or pressure
The pollutant(s) must be condensable at achievable temperature

36. Combustion