Application: used to reduce emissions from buildings
Pros
- Very effective for VOCs and odor reduction.
- Potential to remove pathogens.
Cons
- Technology is still not common and may require more development.
- Cost estimates are somewhat unknown.
- Filters may be needed to reduce the impact of particulate matter on treatment surfaces.
Description
Ultraviolet (UV) light has been used in treating volatile organic compounds (VOCs) and pathogens in water treatment for some time. It has also been used in air cleaning on a more limited basis for home usage as well as some applications for Homeland Security regarding bio-aerosol inactivation within duct systems.
| Figure 1. An example of a pit fan that could potentially be outfitted with a UV treatment system. |
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Photocatalytic oxidation is achieved when air flows past a UV light and a titanium dioxide (TiO2) coating. This creates hydroxyl radicals and super-oxide ions that are highly reactive. These then combine with bacteria and VOCs, causing a reaction which breaks the pollutant down into carbon dioxide and water vapor. The intensity of UV light and the exposure time are ultimately the most important factors in effectiveness. Temperature, reflectivity of the duct material and humidity are all important as well but to a lesser degree.
Research was done by Koziel et al (2008) to examine the impact of using a UV-185 nm light in the presence of TiO2. Because not all chemical compounds are equally odorous, they looked at the odor degradation of several selected odor-causing VOCs as well as the chemical degradation.They tested various exposure times using a 5.5 Watt UV lamp on a lab scale. Exposure time is an important consideration in developing the actual design for field application. It was found that with a one second exposure time VOCs were reduced from 80 to 99%, while hydrogen sulfide was only reduced 10%. Odor reduction for each compound ranged from 38 to 100%.
While this mitigation technique has not been fully developed for use in livestock housing, it has great potential.The one second retention time is practical. For instance, if a 24” fan moves 6000 cfm of air, the air speed would be 1910 fpm on average. For a one second retention time, this means that a UV lighting duct equivalent to 32’ long would be needed or a treatment plenum that would hold up to 100 cubic feet of air. A similar length treatment duct would be needed on other fans as well. UV treatment could also be used for incoming air to reduce pathogen load, though it has not been fully tested in this environment. The depositing of dust on UV bulbs is a possible concern.
Effectiveness
| Component | Reduction | Notes |
|---|---|---|
| NH3 | --- | Field application under development |
| H2S | 10% | |
| Odor | 38 to 100% | |
| Particulate Matter |
--- |
|
| Volatile Organic Compounds (VOC) | 80 to 99% | |
| Cost | $$ |
Cost Considerations
The costs are mostly unknown however, Koziel et al (2008) estimated that the electrical cost to be $0.25 per pig finished. Capital costs would be for duct construction and lamp purchase. Additional costs may be needed for filtering particulate matter prior to the UV treatment.
References
Honeywell. “Ultraviolet Air Treatment Systems”. Accessed April 29, 2014.
Koziel, J., X. Yang, T. Cutler, S. Zhang, J. Zimmerman, S. Hoff, W. Jenks, Y. Laor, U. Ravid, R. Armon, and H. Van Leeuwen. 2008. Mitigation of Odor and Pathogens from CAFOs with UV/TiO2: Exploring the Cost Effectiveness. In: Mitigating Air Emissions from Animal Feeding Operations Conference Proceedings. Iowa State University, Ames, IA. p. 169-173.
Peak Pure Air. “How TiO2 UV Photocatalytic Oxidation Works.” Accessed April 29, 2014.