&EPA
United States
Environmental Protection
Agency
EPA/540/SR-95/526
August 1995
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Emerging Technology
Summary
Development of a Photothermal
Detoxification Unit
There has long been interest in uti-
lizing photochemical methods for de-
stroying hazardous organic materials.
Unfortunately, the direct application of
classic, low temperature photochemi-
cal processes to hazardous waste
detoxification is often too slow to be
practical for wide spread use. Further-
more, low-temperature photochemical
processes often fail to completely con-
vert the targeted wastes to mineral
products which are either harmless to
the environment or easily scrubbed
from the system effluent. Researchers
at the University of Dayton Research
Institute (UDRI) have developed a
unique photothermal process that over-
comes many of problems. Specifically,
it has been found that there are numer-
ous advantages to conducting photo-
chemical detoxification at relatively high
temperatures. Under the conditions of
simultaneous exposure to heat and ul-
traviolet (UV) radiation the rate of de-
structive photothermal reactions can be
greatly increased with complete miner-
alization of the waste feed. Furthermore,
it has been demonstrated that at the
elevated temperatures used in this pro-
cess the efficiency of UV radiation ab-
sorption also increases resulting in an
overall improvement in process effi-
ciency. These features (i.e., fast, effi-
cient, and complete destruction of or-
ganic wastes) make this a promising
technique for destroying hazardous or-
ganic wastes in the gas-phase. The au-
thors present the theoretical foundation
for the photothermal detoxification pro-
cess along with a summary of the re-
sults from a bench-scale flow reactor
system. The basic design, capital cost,
and operating cost for a full-scale flow
reactor system using currently avail-
able industrial illumination equipment
is also presented.
This Project Summary was developed
by the EPA's National Risk Manage-
ment Research Laboratory, Cincinnati,
OH, to announce key findings of the
SITE Emerging Technology that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
One approach to destroying hazardous
organic wastes which has received con-
siderable attention over the years is the
use of photochemical reactions in place of
conventional thermochemical or combus-
tion reactions. Photochemical techniques
have been of interest because photochem-
istry, the use of light to induce a chemical
-------
reaction, can be conducted at relatively
low temperatures, often at or near room
temperature. Unfortunately, most attempts
to exploit photochemistry as a waste de-
struction technology have been frustrated
by slow reaction rates and the inability to
completely convert waste materials to min-
eral products. Specifically, conducting pho-
tochemistry at low temperatures often
requires exposure times of minutes, hours,
and even days to achieve meaningful lev-
els of conversion. Furthermore, the prod-
ucts of the reactions are often other organic
compounds rather than inorganic mineral
compounds such as carbon dioxide, wa-
Side View
ter, and hydrogen chloride. The University
of Dayton Research Institute (UDRI) has
developed a novel photochemical process,
embodied in a device called a
Photothermal Detoxification Unit (PDU),
which overcomes these problems and of-
fers an efficient means of destroying haz-
ardous organic materials.
The PDU, illustrated in Figure 1, is a
relatively simple device consisting of a
thermally insulated vessel enclosing a set
of large, medium-pressure, mercury vapor
lamps. The purpose of the lamps is to
provide an efficient source of near-UV ra-
diation as well as heat for the process.
Additional heat may be provided by unit
operations upstream of the PDU, such as
a thermal desorption unit, combustor, a
dedicated preheater, or other operations.
The basis for the PDU's operation is to
use the near-UV radiation from the mer-
cury vapor lamps to induce destructive
photochemical reactions and to conduct
these reactions at moderate temperatures
(i.e., 200-600°C) so they proceed to com-
plete mineralization quickly and efficiently.
Since this process requires both light, as
with conventional photochemical pro-
cesses, and heat, it is referred to as a
photothermal detoxification process. The
Top View
General Layout of a Four Chamber PDU
Side View Top View
Chamber Details
Figure 1. Conceptual schematic of a prototype Photothermal Detoxification Unit (PDU) based on a mercury arc lamp illumination system.
2
-------
result is a technology capable of destroy-
ing organic materials at temperatures much
lower than thermal processing alone and
at temperatures easily achievable through
non-combustion means. Indeed, the tem-
perature requirements for the system may
already exist for many processes such as
the thermal desorption of contaminants
from soils.
Procedure
The specific exposure conditions of time,
temperature, and radiant intensity will be
largely dependent on the materials of in-
terest and the required level of destruc-
tion. In general, these aspects of the PDU
design and operation are brought together
through a reactor performance model such
as
(1)
where fr is the fraction remaining in the
process stream exiting the PDU, kgnd is
the rate of thermal reactions, kab is the
rate of light absorption, $ is an efficiency
term for the photothermal reactions re-
ferred to as the quantum yield, and t is
the mean exposure time. In the PDU, the
rate of thermal reactions should be rela-
tively small, but it is important to explicitly
include it for those cases where the sys-
tem may be operated at higher tempera-
tures and thermal reactions can become
important. The rate of light absorption re-
flects the extent of overlap between the
emission spectrum of the light source and
the absorption spectrum of the waste. This
term is also dependent on the intensity of
the light source and the number of lamps
used. The quantum yield is an efficiency
term describing what fraction of the light
absorbed actually results in destruction of
the waste feed. Finally, the mean expo-
sure time reflects the size of the PDU and
the rate of flow through the system. Note
that all of these terms lie in the exponent
of Equation 1 and therefore can have a
powerful influence on the performance of
the PDU.
Other reactor performance models may
be used to describe the PDU, but all share
the same basic features of Equation 1.
Specifically, to predict the performance of
the PDU, and hence define a system for a
given application, it is necessary to have
knowledge of the thermal chemistry (k d),
the photochemistry (c|>), and the UV ab-
sorption behavior (kab) of the system. Fur-
thermore, all of these aspects of the PDU
are expected to be functions of tempera-
ture. Unfortunately, since the PDU oper-
ates under unique circumstances, none of
the required high-temperature spectro-
scopic and photochemical data is avail-
able from the literature. Therefore,
researchers at UDRI designed and built a
High Temperature Absorption Spectropho-
tometer (HTAS) to obtain the necessary
spectroscopic data, and a Laboratory
Scale-Photothermal Detoxification Unit
(LS-PDU) for the basic thermal and
photothermal information. The latter was
particularly useful for demonstrating the
effectiveness of the photothermal process.
The HTAS, shown in Figure 2, is a
custom built, single-beam spectrophotom-
eter capable of operating at temperatures
as high as 1,000°C. Since the organic
molecules for which the HTAS was de-
signed to study tend to decompose with
prolonged exposures at elevated tempera-
tures, the system is fitted with a flow cell
rather than a static cell found in most
commercial spectrophotometers. Further-
more, an inert carrier gas (i.e., nitrogen) is
used for sample transport to eliminate the
possibility of sample oxidation. By flowing
a carrier gas laden with the sample of
interest through the cell the length of ex-
posure to elevated temperatures can be
kept short (typically 1 sec) to limit destruc-
tion of the sample at very high tempera-
tures.
The LS-PDU, shown in Figure 3, is a
dedicated flow reactor system capable of
obtaining thermal and photothermal de-
composition data on a great variety of
compounds. Structurally, the LS-PDU
shares many features with the HTAS. For
example, the LS-PDU includes dual
sample inlets connected to a cylindrical
vessel through a single sample transfer
line. However, whereas the HTAS was
design to prevent reactions from taking
place in the system, the LS-PDU was
designed to conduct reactions under care-
fully defined conditions and analyze the
products of those reactions. For this pur-
pose the vessel connected to the inlet line
OMA
Absorpbon
Focussing
Optics
Furnace
\
1
OMA
Morsochrometar Vent
Sampte Inlets
Deuterium
Lamp
;
Figure 2. General schematic of the High Temperature Absorption Spectrophotometer (HTAS) showing the principal elements of this system.
-------
Workstation
X
HFID Workstations
Xenon Arc
Lamp
Intel Heaters
Sample Inteis
Figure 3. General schematic of the Laboratory Scale-Photothermal Detoxification Unit (LS-PDU) showing the principal elements of this system.
\s a small cylindrical reactor measuring
1.2 cm in diameter by 8.4 cm long. The
exhaust from the reactor flows through a
heated transfer line to a trapping system
which collects all of the condensable ma-
terials from the flowing gas. This trap is a
single tube-in-shell design similar to a labo-
ratory condenser. The shell side is cooled
with nitrogen gas which has in turn been
cooled by a liquid nitrogen bath. This al-
lows the trap to operate at temperatures
as low as -180°C, though -160°C is rou-
tinely used. During the effluent collection
phase of operation the exhaust from the
trap is vented to a fume hood. In prepara-
tion to analyze the collected material, this
vent is closed which directs the flow of
gas to an inline analytical system consist-
ing of a programmed temperature, capil-
lary column gas chromatograph (GC) fitted
with dual columns and an inlet splitter.
One of the columns is connected to a
scanning quadrapole mass spectrometer
(MS), the other to a hydrogen flame ion-
ization detector (FID). The LS-PDU may
be operated at temperatures as high as
1,000°C and used with nearly any UV
radiation source. It is currently configured
with a pulsed dye laser, solar simulator,
and a high pressure xenon arc lamp.
All samples used in the tests described
below were high purity standards (typi-
cally 99+%) obtained from commercial sup-
pliers.
Results and Discussion
Conducting photochemical detoxification
at elevated temperatures improves the
overall efficiency of the process in three
important areas; the spectroscopy, the rate
of destruction, and the completeness of
the destruction.
The impact of temperature on the spec-
troscopy is illustrated by the high tem-
perature absorption spectra for
trichloroethylene (TCE) shown in Figure
4. For comparison, the emission spectra
for high-pressure, xenon arc (which was
used on the LS-PDU) and medium-pres-
sure, mercury vapor lamp (proposed for
the PDU) are shown in Figure 5. The data
summarized in Figure 4 show that as the
temperature increases, the absorption
spectrum shifts to longer wavelengths and
increases in overall intensity. The net re-
sult is that the overlap between the emis-
sion spectrum of the light source and the
absorption spectrum of the sample in-
creases with temperature. In the case of
TCE, the rate of photon absorption with
xenon arc as the radiation source, in-
creases over 8-fold as the temperature
increases from 100 to 600°C. Recalling
that the reactor performance model sug-
gests an exponential dependence on the
rate of absorption, this is a very significant
feature of the photothermal process.
The most important aspect of the
photothermal process is whether the light
absorbed by the waste feed results in the
destruction of the waste feed. The LS-
PDU data for TCE exposed to 18.1 W/cm2
of xenon arc radiation for 10 sec in air
(summarized in Figure 6) show that is
indeed what happens. Specifically, this
example clearly shows the photothermal
process is capable of destroying a signifi-
cant portion of the TCE under conditions
where no thermal destruction is occurring.
For example, at 500°C the thermal de-
composition has not yet begun, while the
photothermal process has destroyed ap-
proximately 60% of the sample.
The data presented in Figure 6 seem to
suggest that the thermal and photothermal
processes become equally efficient at high
temperatures (i.e., above 600°C). How-
ever, this is in fact an artifact of how the
data is presented. If we compare the ratio
of the fraction remaining undestroyed from
a thermal exposure to the fraction remain-
ing from a photothermal exposure (a value
referred to as the photothermal enhance-
ment ratio), we find the photothermal pro-
cess actually continues to improve over
the comparable thermal process through-
out the temperature range (cf. Figure 7).
The results for TCE illustrate that it is
important to utilize a reactor model that
explicitly includes the thermal component
of the photothermal process so that the
two components may be separated in the
course of interpreting data from the bench-
-------
o
"o
E
o
ts
JO
O
2
2,500-
2,000-
1,500-
£ 1,000-
500-
0
600°C
500°C
400°C
300°C
- 200°C
1 ' I ' ' ' ' I ' ' ' ' I ' ' ' T-I • i i i | • i • i | • i • i | i i i
230 240 250 260 270 280 290 300 310
Wavelength, nm
Figure 4. The absorption spectra for trichloroethylene at 100, 200, 300, 400, 500, and 600'C showing that the absorption shifts to longer wavelengths and
increases in intensity as the temperature increases.
8
T3
ra
ce
o
w
T3
0>
2.
ffl
Q.
Q)'
220 230 240 250 260 270 280 290 300
Wavelength, nm
Figures. The spectral radiance of IW/cm2 of medium pressure mercury and high pressure xenon arc emission showing the xenon arc spectrum
(approximately 2.5% of which is at wavelengths less than 300 nm) is spread out as broad-band emission, while the mercury arc spectrum (of which
approximately 15% is at wavelengths less than 300 nm) is concentrated in narrow emission lines.
E
-------
5.0-
o
.c
CL
4.5-
4.0-
3.5-
3.0-
2.5-
2.0-
1.5-
1.0
200 300 400 500 600
Temperature,°C
700
800
Figure 7. The ratio of the fraction remaining following thermal and photothermal exposures for
trichloroethylene exposed to 0 (thermal) and 18.1 W/cm2 (photothermal) of xenon arc
radiation for 10 sec in air showing that the photothermal process steadily increases in
efficiency compared to the thermal process as the temperature increases.
scale system. In this way, fundamental
information can be obtained to predict the
performance of full-scale systems. Al-
though the results for TCE demonstrate
that the exposure conditions used in the
bench-scale system are probably inappro-
priate for a full-scale system, the data are
still valuable for the fundamental informa-
tion contained. The thermal data yield in-
formation about the thermal decomposition
needed for the PDU model, and the spec-
troscopy (ca. Figures 4 and 5) gives the
light absorption rate information. When this
information is combined with the
photothermal destruction data, the quan-
tum yield can be extracted as shown in
Figure 8. These results illustrate that the
rate of destructive photochemical reac-
tions is increasing with temperature (the
decrease in quantum yield between 550
and 600°C is thought to result from com-
peting thermal reactions which become
significant in this temperature region). Re-
calling that the rate of photon absorption
also increases with temperature, the data
clearly show the importance of high tem-
perature in the photothermal process.
The last important aspect of the
photothermal process is its ability to com-
pletely mineralize the waste feed (i.e., con-
vert to mineral products of complete
conversion such as carbon dioxide, water,
hydrogen chloride, etc.). The data for
1,2,3,4-tetrachlorodibenzo-p-dioxin (TCDD)
shown in Figure 9 demonstrate that the
photothermal process can easily destroy
this type of hazardous material which has
traditionally challenged conventional waste
destruction techniques. The efficiency of
the photothermal process is clearly shown
in the enhancement ratio data summa-
rized in Figure 10. As in the case of TCE,
the photothermal enhancement increases
throughout the temperature range and by
600°C it reaches a value of nearly 1,300.
In addition to demonstrating the high effi-
ciency in destroying TCDD, this data set
allows direct observation of how a
photothermal reactor behaves when oper-
ating in a predominantly photo mode (as
compared to a combined photo/thermal
mode as in the case of the LS-PDU data
for TCE). It is instructional to examine the
chromatograms from these tests.
LS-PDU GC/FID traces from thermal
exposures at 300°C (100% remaining) and
600°C (35.4% remaining), and a
photothermal exposure at600°C (0.0285%
remaining) for TCDD are summarized in
Figure 11. The 600°C thermal data illus-
trate the production of numerous PICs
that often accompany the thermal decom-
position of organic compounds. The
photothermal trace clearly shows that not
only is the parent TCDD destroyed under
these conditions, but nearly all of the as-
sociated products as well. Furthermore,
the data shown here include all products
that were condensable at -160°C (the tem-
perature at which the LS-PDU's effluent
trap was operated), so that all but the
lightest organic products (such as meth-
ane and ethane) are recovered. This em-
phasizes that the photothermal process
differs significantly from conventional di-
rect photochemical processes in that
photothermal decomposition reactions lead
to the complete mineralization of the waste
feed.
With the available laboratory- and
bench-scale reactor data, it is now pos-
sible to predict the performance of a full-
scale PDU, given the geometry of the
reactor and the emission characteristics
of the illumination system. In the PDU in
Figure 1, the basic reactor vessel is shown
as a cylinder measuring 2.5 m (8.2 ft) tall
and 2m (6.6 ft) in diameter giving an inter-
nal volume of 7.85 m3 (277 ft3). The illumi-
nation system consists of six medium
pressure mercury lamps delivering 15 kW
of radiant energy each with a nominal arc
length of 2 m (6.6 ft). This gives a mean
radiant intensity of 1.23 W/cm2 with a near-
UV spectral distribution (cf. Figure 5). Per-
formance estimation using a
tanks-in-series model suggests that a com-
plete PDU system should consist of four
such vessels connected in series. In this
arrangement the system performance
would approach that of a plug flow reac-
tor, which would offer the highest theoreti-
cal destruction efficiency. Therefore, the
PDU system would have an internal vol-
ume of 31.4 m3, or approximately 1,100
ft3. Larger capacity can be achieved by
operating additional chambers in series,
or sets of chambers in parallel.
The performance of a four-chamber
PDU expressed in terms of the estimated
capacity achieving 99% destruction in ac-
tual fP/min for selected compounds is sum-
marized in Table 1. These results indicate
that for volatile organic compounds, the
PDU should be operated at temperatures
greater than 500°C and throughputs on
the order of 1,000-3,000 cfm can be ex-
pected. The performance for semi-volatiles
may be much greater, both in the allow-
able temperature range (greater than
300°C) and capacity (2,000 to 6,000 cfm).
This illustrates that the PDU is capable of
processing VOCs at high temperatures
and is particularly well suited for semi-
volatile compounds where it can be oper-
ated at lower temperatures. Furthermore,
there are other types of lamps which may
be used (i.e., low pressure mercury, xe-
non excimer, etc.) which could give better
performance for volatile compounds.
The overall capital and operating costs
for the PDU chamber illustrated in Figure
1 were calculated as summarized in Table
2. In this table the costs for the shell and
insulating firebrick where taken to be simi-
lar to that reported for a hazardous waste
incinerator afterburner and corrected to
1995 costs. The cost for the lamps, lamp
wells, and lamp ballasts were taken from
the manufacturer's literature. These esti-
-------
0.6
a
0.3-
0.2-
0.1
I ' ' ' ' I
200 300 400 500 600
Temperature, °C
700
800
Figure 8. The photothermalquantum yieldfortrichloroethylene illustrating the rate of'the photochemical reactions increasing with temperature. The observed
increase in the overall efficiency of the photothermal process is a result of this increase in the reaction rate and the increase in the efficiency of near-
UV light absorption.
100-
—•— Thermal
- -e - - Photothermal
40-
200 300 400 500 600
Temperature, °C
700
800
Figure 9. Conversion as a function of temperature for 1,2,3,4-tetrachlorodibenzo-p-dioxin exposed to 0 (thermal) and 18.1 W/cm2 (photothermal) of xenon
arc radiation for 10 sec in air showing that the photothermal process can destroy this compound to very high levels at relatively low temperatures.
1400-
o
D^
"ro
0
t
1200-
1000-
800-j
600-
400-
200-
0
200
300
400 500 600
Temperture, °C
700
800
Temperature, °C
Figure 10. The ratio of the fraction remaining following thermal ana pnowmermai exposures ror i,^,3,4-tetrachlorodibenzo-p-dioxin exposed to 0 (thermal)
and 18.1 W/cm2 (photothermal) of xenon arc radiation for 10 sec in air showing that the photothermal process steadily increases in efficiency
compared to the thermal process as the temperature increases.
7
-------
300°C, thermal (no conversion)
TCDD
o
Q.
U)
&
g
LL
O
O
600°C, thermal
Organic PICs
TCDD
600°C, 17.6 W/cm xenon arc radiation
5 10 15 20 25 30
Chromatographic Retention Time, min.
Figure 11. Example GC/FIDchromatograms from TCDD exposedto 300 thermal, 600 thermal, and600°C photothermal (17.6 W/cm2) for 10 sec in air showing
that the photothermal process destroys the complex mixture of PICs (or prevents their formation) as well as the parent compound.
-------
Table 1. Estimated PDU1 Capacity2 for Selected Compounds
Compound
Temperature ('C)
300
400
500
600
Trichloroethylene
m-Xylene
Chlorobenzene
1,2,3,4-Tetrachlorodibenzo-p-dioxin
131
53
98
2,190
384
60
131
2,504
937
158
427
3,300
2,590
1,900
1,730
5,780
1 Four 2.5x2 m chambers fitted with six 15 kWmedium pressure mercury lamps.
2 Expressed as actual cubic feet per minute achieving 99% destruction.
Table 2. Estimated Costs for a Single PDU Chamber Fitted with Six 15 kW Medium Pressure
Mercury Lamps
Item
Cost
Expected Life
Annual Cost
Carbon Steel Shell
Firebrick Insulation
Lamp Wells
Lamp Ballasts
Support Structure
Sub Total
Lamps
Sub Total
Electrical Service7
Grand Total
Hourly Cost3
$20,800 1
$1,3702
$8,400
$8,500
$8,500 5
$47,570
$3,000
$50,570
20 years
5 years
2 years3
4 years4
20 years
6 months8
$1,040
$274
$4,200
$2,125
$425
$8,064
$6,000
$14,064
$22,500
$36,564
$7.31
1 Assuming $86/ft2
2 Assuming $1.44/ft2-in.
3Assuming 10,000 hr life and 5,000 hr of operation/yr.
4 Assuming 20,000 hr life and 5,000 hr of operation/yr.
5 Assuming support structure and equipment is 20% of the chamber cost less support.
6 Assuming 2,500 hr life and 5,000 hr of operation/yr.
1 Assuming $0.05/kW-hr and 5,000 hr of operation/yr.
sAssuming 5,000 hr of operation/yr.
mates suggest the majority of the capital
costs will be in fabricating the reactor shell,
followed by the lamp wells, ballasts, and
the system support structure and equip-
ment.
With respect to the amortized costs (us-
ing a simple linear depreciation model),
Table 2 suggests the most expensive com-
ponent will be the lamps and the lamp
wells. The 2,500 hr used for the lamp life
was based on the manufactuer's estimate
assuming 5 hr of operation for every lamp
start. Discussions with lamp manufactur-
ers indicate that since the lamps will likely
see continuous service in the PDU, sig-
nificantly longer service life is likely. This
should reduce overall cost of the lamps
and, hence, the operating costs of the
PDU. The second highest amortized cost
is the lamp wells which are expected to
degrade from attack from dust and water
vapor. The cost estimates assume the
lamp wells are replaced with new wells for
every 10,000 hr of operation. If the wells
can be replaced with refurbished units,
this cost could be reduced.
With respect to consumable materials
only electricity for the lamps is considered
here. As Table 2 illustrates, electricity is
the largest single contributor to the overall
cost of the PDU. The relatively high elec-
trical energy requirement comes from the
fact that only about 15% of the electrical
energy is converted to useful near-UV ra-
diation. If other lamps are made available,
such as low pressure mercury or xenon
excimer, this cost could be considerably
reduced by the thermal contribution to the
system from the lamps. Specifically, in a
well insulated vessel the 90 kW supplied
to the chamber by the six 15 kW lamps is
sufficient to heat approximately 600 cfm
of air saturated with water vapor (as from
a soil vapor extraction unit) from 15°C to
500°C. Therefore, depending on the spe-
cific site requirements, the heat from the
lamps should reduce the size of a
preheater, or even eliminate one entirely.
The estimate summarized in Table 2 sug-
gests the overall operating cost for a PDU
based on the design presented in Figure
1 should be approximately $8/hr-chamber
including the depreciation of the equip-
ment, replacement lamps, and required
electrical service.
Conclusions and
Recommendations
In summary, the photothermal detoxifi-
cation process offers a technologically
simple and effective means of destroying
organic materials in gaseous process
streams. It is a non-combustion process,
so additional fuel and gases (e.g., com-
bustion air) are not required, though in
some cases (e.g., low temperature pro-
cesses such as soil vapor extraction) a
preheater may be needed. Furthermore,
the process efficiency is not dependent
on initial concentration making it ideally
suited for dilute waste streams. Results
from bench-scale tests show that the pro-
cess is exceptionally efficient in destroy-
ing semi-volatile wastes such as dioxins
which suggests similar results may be ex-
pected for related compounds such as
polychlorinated biphenyls and
dibenzofurans. Estimated capital and op-
erating costs suggest the photothermal
process should be relatively economical
to implement using currently available in-
dustrial illumination systems and hardware,
and that future advances in near-UV illu-
mination systems should reduce the over-
all cost even further. Given these results it
is recommended that the PDU be ad-
vanced to the level of a pilot-scale dem-
onstration at an appropriate Superfund site.
-------
John L. Graham, Barry Dellinger, and Joseph Swartzbaugh are with Environmen-
tal Science and Engineering Group, University of Dayton Research Institute,
Dayton, OH 45469-0132.
Chien T. Chen is the EPA Project Officer (see below).
The complete report, entitled "Development of a Photothermal Detoxification
Unit," (Order No. PB95-255733; Cost: $27.00, subject to change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Edison, NJ 08837
United States
Environmental Protection Agency
National Risk Management Research Laboratory (G-72)
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/540/SR-95/526
------- |