New Methods in Environmental Engineering to Control Air Pollution
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Abstract
This report examines different elements of air pollution. It looks at the causes and effects of air pollution. It examines the different methods that people can use to mitigate air pollution, from an environmental engineering perspective. It then evaluates the different methods highlighted, and offers recommendations based on the factors to consider when selecting the control strategy to use.
Table of contents
Causes and Effects of Air Pollution. 6
New Strategies to Control Air Pollution. 8
Electrostatic precipitators. 9
Selective catalytic reduction systems. 9
Evaluation and Recommendations. 11
List of illustrations
Introduction
Air pollutants include suspended particle matter such as fumes, smokes, dusts, and mists, gaseous pollutants, and odors. The most common pollutants include nitrogen dioxide, sulfur dioxide, particle pollution, carbon monoxide, lead, and ground-level ozone (EPA, 2010). Air pollution has had a negative effect on human health, animals and plants. Most of the air pollution tends to occur because of human related activities. Manufacturing is necessary since it produces goods that are necessary for human, and sometimes plant and animal survival. Yet, manufacturing is a major cause of air pollution. It is not possible to walk everywhere one wants to go, and people have to use different forms of transportation.
Despite the increase in technology related to the use of alternative fuels, most people continue to use fossil fuels. The combustion of these fuels contributes to air pollution. Some natural processes such as volcanoes and human and animal processes such as breathing have increased the level of carbon dioxide in the atmosphere. Efforts by the government and other stakeholders have succeeded in ensuring that the level of pollutants released continues to decrease (EPA, 2010). Despite efforts to reduce air pollution, many people live in the areas that exceed the national ambient air quality standard.
The number of people (in millions) living in counties that exceed the national ambient air quality standards
Figure 1
Retrieved from http://www.epa.gov/airtrends/2010/report/highlights.pdf
Background
The effects of air pollution have necessitated the need to develop different strategies of controlling it. Since it is not possible for people to survive without engaging in some of the activities that cause air pollution, people from different sectors and fields have come up with ways of controlling air pollution. Control of air pollution from an environmental engineering perspective involves an integration of environmental knowledge with knowledge gained from engineering and science. This involves an investigation of how different technologies and systems contribute to the formation of different particles, and the ways that engineers can mitigate the emissions.
Causes and Effects of Air Pollution
Causes
There are different causes of air pollution. One of the major causes is the burning of fossil fuels, which results to the emission of sulfur dioxide. This happens with the burning of substances such as coal and petroleum, thus transportation, whether by road, rail, or air, is a major form of air pollution. Other pollutants released when burning fossil fuels include carbon monoxide and nitrogen oxide. Different chemicals used in the manufacture of farming products such as insecticides and pesticides are hazardous to the environment as they produce gases such as ammonia, which is an air pollutant. Factories and industries emit substances that contribute to air pollution. Such substances include hydrocarbons and other chemicals. Some of the products used in households such as cleaning detergents and paints cause air pollution. They emit different chemicals to the atmosphere, which contribute to air pollution.
CO2 per capita emissions from fossil fuel use and cement production from the top 5 emitting regions
Figure 2
Retrieved from http://ies.jrc.ec.europa.eu/uploads/images/Highligts/201207-co2-v2.jpg
Effects
Human health
Air pollution has negative effects on the human body and human health, as it causes respiratory problems and heart conditions. Some of the effects are short-term, whereas others are long term. Long-term exposure to different air pollutants has reduced people’s life expectancy by several months (Amann et al., 2011). It can cause eye, nose, and throat irritation, and make it difficult for people to breathe. Air pollution aggravates conditions such as asthma and it is especially harmful to children and the elderly. Some of the pollutants released in the atmosphere, which include vinyl chloride, are harmful to health, and they can lead to cancer, damages to the brain, and birth defects.
The environment
It contributes to global warming, and leads to the thinning of the ozone layer. This has contributed to climatic changes. There has been an increase in temperatures because of this; hence summers tend to get hotter. However, air pollution is not the only factor that has contributed to the change in climate. When the ozone layer is damaged, there is nothing to protect people from harmful ultraviolet rays, and this increases the chance of people developing health problems such as skin cancer. It harms the environment by causing acid rains, and other forms of acid precipitation such as snow, and fog. This happens when gases such as sulfur oxides that are in the polluted atmosphere combine with the rain. Acid rain is harmful to humans and the environment. Air pollutants pollute lakes and other water bodies because of the acid rain, and this harms aquatic life (EPA, 2012). Air pollution reduces visibility, as seen in areas where there is smog.
Smog at noon in Beijing
Figure 3
Retrieved from http://static.guim.co.uk/sys-images/Guardian/Pix/pictures/2009/6/18/1245347153341/Traffic-runs-slowly-as-he-001.jpg
New Strategies to Control Air Pollution
As people continue researching more on air pollution, they continue coming up with ways of controlling air pollution. In the past, efforts of different people including engineers and environmentalists have led to positive changes in the manufacturing sector, which has led to a reduction in air pollution. They have developed ways of ensuring that people use alternative products, and this has in turn led to a reduction in the release of harmful emissions. In addition, air pollution control includes the use of different equipment and processes. Modern technologies are capable of removing more than one type of pollutant. This makes them more cost effective, and it encourages people to use them to control air pollution.
Electrostatic precipitators
Electrostatic precipitators involve using electric charges to control the pollutants. The precipitators work by passing particles through electric fields with high voltage where they are charged, and then attracting them to a plate with a negative charge where they collect (Nemerow & Agardy, 2009). They are very effective in capturing toxic metals and particle-bound mercury. They do not use any reagents, and they tend to be expensive. Their effectiveness depends on the type of particle, since some particles are more sensitive than others are. For instance coal particles are easier to control because they have high amount of sulfur, while fly ash particles are more difficult to control because they have low sulfur. Efficiency of the system also depends on the size of the particles. The smaller the size of the particles, the more effective t he electrostatic precipitators will be (Staudt & Bradley, 2011).
Selective catalytic reduction systems
Selective catalytic reduction systems reduce air pollution by nitrogen oxides by more than ninety percent. They use urea and ammonia as reagents. They have co-benefits since they oxide mercury, making it possible to capture the mercury in downstream wet scrubbers, and they reduce dioxins. Modern technology has made it possible to create a hybrid by combining the selective catalytic reduction systems and the selective non-catalytic reduction system. The hybrid system is more effective since it is able to control sulfur oxides by 95% and remove mercury by 98% (Staudt & Bradley, 2011).
Baghouse systems
Baghouse systems are effective in reducing air pollution of elements such as mercury and other metals in plants using coal as fuel. The baghouses can be made of woven materials, and they are also referred to as fabric filters. They collect the dust, and they have a cleaning component, and they capture nearly all the emissions released. It takes about one to two years to design, and implement the fabric filters. This depends on the work that has to be done on the systems. They work by filtration; hence they do not use any reagents. They have other co-benefits including the capture of other toxic metals other than gases, and they tend to be expensive. The baghouse captures the reaction products and sulfur oxides at high rates, making them more effective. Modern technologies have improved the wet scrubbing systems to the extent that they are almost 100% effective (Staudt & Bradley, 2011).
Figure 4
Example of a baghouse
Figure 4
Retrieved from http://www.baghouse.com/wp-content/uploads/2010/12/dust-collection-systems1-223×300.jpg
Dry sorbent injections
Dry sorbent injections are an alternative form of control technologies for the removal of sulfur oxides for small coal companies because they are cost effective. They are also efficient in the control of acid gas emissions. They remove sulfur trioxide, which hinders the capture of mercury. The dry sorbent injections use different reagents including trona, hydrated lime, and sodium bicarbonate. These reagents tend to be more expensive compared to reagents used in other systems. This system does not require additional chambers since the reaction takes place within the system (Staudt & Bradley, 2011). Manufacturers have used scrubbers for a long time. However, modern day scrubbers have a fabric filter, which captures the dry product. This method is quite expensive, but it is highly effective in the capture of sulfur oxides and mercury. The wet scrubber upgrades are not as expensive as the wet scrubbers, are but they are just as effective.
Evaluation and Recommendations
Electrostatic precipitators are relatively cheap and they are effective. In addition, one does not need to have much technological and scientific knowledge to implement them since they are simple to operate. Selective catalytic reduction systems are expensive and the cost depends on the difficulty of the retrofit. In addition, companies have to be aware of other costs including the cost of replacing the catalyst after about three years, and other operational costs including the cost of purchasing the ammonia reagent. The systems take about two years to install and test, and some can take a longer time depending on the number of retrofits. They hybrid selective systems are expensive, but they are relatively cheaper compared to the selective catalytic reduction systems. Electrostatic precipitators are expensive, complex, and they take a long time to install (Staudt & Bradley, 2011).
Although dry sorbent injections are cost effective, only the small companies can use them. The use of dry scrubbers and fabric filter is effective but it is expensive. The method that a company or another entity chooses to use will depend on the investment that it is willing to put towards air control. There are cheap alternatives to different controls, and one just has to decide on the type of control to use. Upgrading the scrubbing systems is more effective compared to installation of new systems. This is because it takes a relatively short time to upgrade a current system, than it does to implement a new scrubbing system. A new system takes about four years to install, while an upgrade takes a period of less than one year, although they will have the same level of effectiveness. Companies that decide to use the dry sorbent injections have to be aware of the additional costs that they will incur because of storage and handling. However, they are cheaper compared to most other options and they are installed within a short time. Even with the use of more expensive reagents and additional costs, they are less expensive than the scrubbers are (Staudt & Bradley, 2011).
Some factors are important to consider when making decisions on the type of control strategy to implement to control air pollution. One has to be aware of the fact that different processes in manufacturing and other activities leads to the emission of different air pollutants (Amann et al., 2011). Therefore, the type of control used should be capable to mitigating different types of air pollutants. Cost is an important factor for many people. While some people would opt to go for control systems that are relatively cheap to buy, it is important to consider other costs which add up in the process of installation, implementation, and maintenance of the systems. Therefore, a person should go for a complete system which does not need other additional costs, instead of going for a cheap system, which might end up being more expensive in the end. Other factors include the time taken to install and test the system. Systems that take a long time to install end up taking up more resources, hence they tend to be more expensive.
Conclusion
Air pollution harms human beings as well as the environment. It is not easy to eliminate air pollution since some of the causes are natural, and some human activities are necessary for human existence. Environmental engineering has made it possible to have a deeper understanding of the causes of air pollution, and this has made it easier to develop control strategies for air pollution. Engineers have worked together with environmentalists and other interested stakeholders to develop ways of mitigating air pollution. They have modified some of the strategies used since efforts of reducing air pollution began, and this has made these strategies more effective. Many of the strategies used are effective, and they are able to reduce more than one pollutant, this has made them cost effective. When deciding the strategy to use, one has to consider different elements including the time it will take to install and test the system, the cost of the systems, the type of pollutant, as well as the effectiveness of the systems.
References:
Amann, M., Bertok, I., Kleefeld, B. J., Cofala, J., Heyes, C., Isaksson, H. L., Klimont, Z. et al. (2011). Cost-effective control of air quality and greenhouse gases in europe: Modeling and policy applications. Environmental Modelling & Software, 26, 1489-1501 <ftp://ftp-ccu.jrc.it/pub/vandinge/LOREA/2_AMAN_et_al_GAINS_MODEL_PAPER_DEC2012.pdf>
Awma (2007). Fact sheet: Air pollution emission control devices for stationary sources. Air & Waste Management Association. Retrieved from http://events.awma.org/files_original/ControlDevicesFactSheet07.pdf
Daly, A., & Zannetti, P. (2007). An introduction to air pollution-definitions, classifications, and history. Retrieved from http://www.envirocomp.org/books/chapters/1aap.pdf
EPA (2010). Highlights. United States Environmental Protection Agency. Retrieved from http://www.epa.gov/airtrends/2010/report/highlights.pdf
EPA (2012). Why you should be concerned about air pollution. United States Environmental Protection Agency. Retrieved from http://www.epa.gov/airquality/peg_caa/concern.html
Nemerow, L. N., & Agardy, J. F. (2009). Environmental engineering: Environmental health and safety for municipal infrastructure, land Use and planning, and industry. Hoboken, NJ: John Wiley & Sons
Staudt, E. J., & Bradley, M. J. (2011). Control technologies to reduce conventional and hazardous air pollutants from coal-fired power plants. Retrieved from http://www.nescaum.org/documents/coal-control-technology-nescaum-report-20110330.pdf/
Wesson, K., Fann, N., Morris, M., Fox, T., & Hubbell, B. (2010). A multi-pollutant, risk-based approach to air quality management: Case study for Detroit. Atmospheric Pollution Research, 1, 296-304 <http://www.atmospolres.com/articles/Volume1/issue4/APR-10-037.pdf>