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476 Lawerence K. Wang et al.

Fig. 13. Schematic of direct UV photolysis. (From US EPA.)

Energy Generators, Inc. (UVERG) has asserted that the Wekhof Direct UV Photolysis
to be “both the most efficient and cleanest method of organics destruction in water, gas
and in soil” (37).
Another manufacturer, Purus, Inc., has a direct UV photolysis process that can be used
on-site for cleanup of organic contaminants. It also claims that the process converts
organic contaminants into harmless byproduct. The Purus system utilizes xenon UV
flashlamps. It also sells a commercial direct UV photolysis system that it claims treats
contaminant air emissions.
Figure 13 shows a flow diagram for direct UV photolysis system. Air emission stream
flows into one or more processing chambers that contain UV flashlamps, where the air
emission stream is exposed to a broad spectrum of UV light. While in the chamber, the
organic contaminants in the air emission absorb energy that causes the bonds of the
organic molecules to break apart and release carbon atoms. It is proposed that, under
ideal conditions, these released carbon atoms along with oxygen atoms present in the air
emission stream can form carbon dioxide. When the analysis of the air emission stream
in the chamber indicates that contaminant levels have been lowered to a sufficient level
to meet emission standards, the air stream can then be released from the chamber.

8.2. Application to Air Emission Control
Volatile organic compounds contained in air emission may be destroyed using UV
photolysis. Types of VOC could include volatile chlorinated organic compounds (e.g.,
trichloroethylene [TCE] and methylene chloride) and VOCs present in gasoline
petroleum products (e.g., benzene and toluene). Literature reviews indicate that UV
photolysis technology has not been used at Superfund sites. This technology may be
appropriate in controlling air emissions containing toxic organic compounds released