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
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                            POSTAGES FEES PAID
                                     EPA
                               PERMIT Mo. G-35

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