Remediation: Techniques and Cost - Urban Watersheds: Geology, Contamination, and Sustainable Development - page 404

There are two categories of air pollutant sources: (1) mobile sources, such as automobiles,
trucks, buses, farm machinery, and airplanes and (2) stationary sources, such as industrial
facilities, chemical production facilities, pharmaceutical companies, and refineries (USEPA
2008b). Motor vehicle exhaust accounts for 90% of air contamination (USEPA 2008b); how-
ever, there have been significant improvements in air quality over the last few decades.
Programs and incentives used to reduce the amount and type of contaminants from motor
vehicle exhaust include
• Increasing fuel efficiency
• Decreasing the amount of emissions
• Installing air pollution control devices on vehicles (such as catalytic converters)
• Increasing public awareness (e.g., driving less and not refueling during critical
periods)
• Reformulating fuels (e.g., eliminating the use of lead as an additive)
• Developing more efficient engines
• Requiring inspections and routine maintenance, if necessary (e.g., vehicle emis-
sions inspections)
Stationary sources are divided into two categories: gaseous contaminants and particulate
matter. Removal of contaminants from the gaseous phase is accomplished through vari-
ous technologies, including (USEPA 2008b):
• Contact condenser
• Surface condenser
• Thermal incinerator
• Catalytic incinerator
Removal of particulates is usually accomplished with the installation of a dust collector
(also referred to as a baghouse), or by a similar device called a wet scrubber. The process of
collecting dust (particulates) using a baghouse involves capturing the particulate matter at
or very near the emission source by placing the source under a vacuum. The particulates
are captured using a filter before the air stream is exhausted to the atmosphere. Capture
efficiencies are very high and routinely exceed 95% (USEPA 2008b) Figure 11.31.
11.10 Cost of Remediation
Remediation is costly, and not only in the financial sense. Remediation takes time, patience,
and scientific understanding. Some of the factors controlling whether remediation is con-
ducted, how it is conducted, and the resulting costs are (Rogers et al. 2006, 2009):
• Geology: Different types of geology can influence the extent of contamination and
methods of remediation.
• Hydrogeology: The presence of groundwater often plays a significant role in
assessing risk, migration pathways, and the selection of appropriate technology.