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Emerging Pollution Control Technologies 477

from wastewater and groundwater-treatment technologies. A possible application for
the UV photolysis technology may be air emission streams from biological treatment
process, air stripping process, and in situ remediation of soil by vacuum extraction pro-
cess. Proponents of UV photolysis technology indicate the major advantage of this
technology is that it destroys the toxic organic compounds rather than transferring the
compound to another medium, such as activated carbon (38–42).
Studies on the UV photolysis technology have been limited. Because of the limited
amount of information, it is unclear what range of conditions may be effective for this
treatment technology. A study conducted on an air emission stream containing 300,000
ppb of TCE was lowered to 100 ppb by UV photolysis process that had an approx 3-s
residence time (38). Until further studies establish the range of operating conditions for
this technology, its application for Superfund sites cannot be predicted.
Currently, there are no specific sizing criteria presently available for treating air
emissions by UV photolysis, but sizing is dependent on the following parameters: (1)
the flow rate of the contaminated air emission stream, (2) the concentration of contam-
ination in air emission stream, and (3) the refractoriness of the compounds. Currently, to
size an UV photolysis system, pilot tests would be performed on a sample air stream to
determine the appropriate size for a full-scale system.
The feasibility of using the UV oxidation system for VOC control has been studied by
Moretti and Mukhopadhyay (35). The efficiency of UV oxidation has been compared with
other air pollution control technologies, such as thermal oxidation, catalytic oxidation,
flaring, condensation, adsorption, absorption, boilers and process heaters, biofiltration,
and membrane separation.
Section 10 discusses a comparison between the UV process and other emerging and
conventional processes for VOC control. The UV process is not technically feasible for
removal of PM and heavy metals from air emission streams. It is very effective for VOC
control (99.9% removal efficiency) in a very narrow influent VOC concentration range
200–300 ppmv in an air emission stream.

9. HIGH-EFFICIENCY PARTICULATE AIR FILTERS
9.1. Process Description

Medical, research, and manufacturing facilities use high-efficiency particulate air
(HEPA) filters when they require 99.9% or greater particulate removal. Superfund site
have not widely adopted the use of HEPA filters, which could be utilized as a PM pol-
ishing step on ventilation systems for either a building undergoing asbestos remediation
or an enclosure for a solidification/stabilization mixing bin (39).
Typically, PM control system with HEPA filter (Figs. 14 and 15) has following the
major components: (1) HEPA filter, (2) filter housing, (3) ductwork, and (4) fan. The fil-
ter housing unit requirements for a HEPA filter are dependent on the nature of PM being
collected and on the number/arrangement of filters. To keep personnel who are removing
the HEPA filters from having contact with the filters, a bag-out bag will be required in the
filter housing unit. A filter housing unit with a bag-out bag is shown in Figs. 14 and 15.
Depending on the degree of control and allowable pressure drop across the filters, the
arrangement of filters can be in parallel, series, or a combination of both. Parallel filters