United States
Environmental Protection
Agency
EPA/540/F-93/501
March 1993
&EPA
SUPERFUND INNOMTM
TECHNOLOGY EVALUATION
Emerging Technology Bulletin
Destruction of Organic Contaminants in Air Using
Advanced Ultraviolet Flashlamps
Purus, Inc.
Technology Description: This technology uses photolytic oxi-
dation to destroy volatile organic compounds (VOCs) in soils and
groundwater. The system uses a xenon pulsed-plasma flashlamp
that emits short wavelength ultraviolet (UV) light at very high
intensities. The process strips the contaminants into the vapor
phase, where the UV treatment converts the VOCs into less
hazardous compounds. (See figure 1)
Direct photolysis does not form hydroxyl radicals. Direct photoly-
sis occurs when the contaminants absorb sufficient UV light
energy, transforming electrons to higher energy states and break-
ing molecular bonds. The process requires the UV light source to
emit wavelengths in the regions absorbed by the contaminant. An
innovative feature of this technology is the ability to shift the UV
spectral output to optimize the photolysis.
The process uses vacuum extraction or air stripping to volatilize
VOCs from soils or groundwater, respectively. VOCs then enter
the photolysis reactor, where a xenon flashlamp generates UV
light. T~he plasma is produced by pulse discharge of electrical
energy across two electrodes in the lamp. Ninety-nine % destruc-
tion of the contaminants occurs within seconds, allowing echinu-
s'0" Power Supply
and Electronics
Septum
Sampling Port
Air Out
Septum
Sampling Port
TCE
Booster
Metering Valve
Air In
Impingers
Flow Meters
Air Pump
Figure 1. Schematic of Air-2 photochemical reactor.
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oos operation. Because organlcs are destroyed in the vapor
phase, the process uses less energy than a system treating
dissolved crgnnfcs,
Waste Applicability: The Purus, inc. photolytic oxidation pro-
cess Is designed to destroy VOGs, Including dichioroethylene
(DCE), t»!rachtoroethyiene (PCE), trtchtaroethylene (TOE), and
vinyl chlorMe volatilized from soil or groundwater. Other VOCs,
such as hanzene, carbon tetrachforkte, and 1,1,1-trichIoroethane,
«r» being Investigated.
Teat Resullst A fuB-scale field test began fn October, 1991, and
W@® completed fn July, 1992, The results are listed in table 1. The
test was conducted at the Lawrence Livermore National Labora-
tory Superfiirtd site 300r about 15 miles east of Livermore, GA.
Th® «h« contains soil zones highly contaminated with TCE. A
vacuum extraction system delivered contaminated air to the Purus
Unit at air Hows of up to 500 cubic feet per minute (cfm). Initial
ooncenfraUons of TCE in the air were approximately 250 parts per
million by volume. The contaminant removal goal for the treat-
ment was 99%. Vapor phase carbon filters were placed down-
stream of the Purus unit to comply with the California Air Quality
©mmtesforts control standards during the field test.
The low-wavelength UV emissions allowed direct photolysis of
many VOCs, particularly chlorinated compounds and freons, that
would not have been possible with commercial mercury lamps.
Very rapid and efficient destruction was observed for TCE, PCE,
and DCE, Some VOCs required either pholo-sensitizatfon or a
lower-wavelength light source for rapid photolysis.
The TGE removal resulted in undesirable intermediates. The
main product (greater than 85%) from the chain photo-oxidation
of TCE is dichloraacetyl chloride (DCAG). Further oxidation of
DCAO is about 100 times slower than the photolysis of TCE and
forms dichloroeaibonyl (DOG) fn about 20% yield. At this level of
treatment, the DGC concentration may be excessive, requiring
additional treatment Further studies should focus on the effec-
tiveness of dry or wet scrubbers for removing acidic photo-
oxMatfon products, developing thermal or other methods for
post-treatment of products, and examing the use of shorter-
Wavelength UV lamps or catalysis, to treat a broader range of
VOCs, Parus will examine several of these issues with Argonne
National Laboratory in continued demonstrations at the Depart-
ment of Energy Savannah River site.
A paper and project summary have been submitted for printing
and will be available in the near future.
T*&f* 1. Suttwaty o/ Field Resute with tfta Air-3 Photoreacior*
No, of tfss, TOE CMorfna
SJXW Time Dostfuctton Mote % Mole % Mote % Balance
Lamps fsac/ #y DOC* DGA&* C{-
m
30
30
m
16
m
s
&
1
i
4
4
4
2
4
2
4
2
4
S
&,&
10,1
10,4
4.6
1O,i
4,8
10.4
4,8
9,3
4,S
£99,89
&3&S9
£99.99
99.92
ZS9.99
299.99
L-99.93
fesass
9B.16
88,57
ndf
19.6
2&.O
17.3
21.8
12.4
8.3
9.3
12.3
6,9
25.8
24.4
34.6
S3.7
nd
64.5
72.2
75.2
91.8
86.2
61.6
89.9
91.4
65.3
682
43.2
41.9
38.6
35.8
35.8
78.8
106.2
114.5
91.1
nd
86.2
90.0
88.8
90.3
93.3
Dictihtoaegtyl efcfo/Jefe * Not detected*
*Dkhlorocarbonyl(phosgene).
For Further Information::
EPA Project Manager:
Norma M. Lewis
U.S. EPA Risk Reduction Engineering Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
(513) 569-7685 FAX (513) 569-7620
Technology Developer Contact:
Paul Blystone
Purus, inc.
2150 Paragon Dr.
San Jose, CA 95131
(408) 453-7804 FAX (408) 453-7988
Untied States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Panaliy for Private Use
$300
BULK RATE
POSTAGES FEES PAID
EPA
PERMIT Mo. G-35
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