Membrane-Mediated Extraction and
Biodegradation of VOCs from Air
Steven W. Peretti (speaker), Robert D, Shepherd
North Carolina State University
Box 7905
Raleigh, NC 27695
Email: peretti@eos.ncsu.edu
Russell K. Clayton, David E. Proffitt
ARCADIS Geraghty & Miller
4915 Prospectus Dr.
Durham, NC 27713
Norman Kaplan
U.S. Environmental Protection Agency
National Risk Management Research Laboratoiy
Research Triangle Park, NC 27711
Joseph D. Wander
Air Force Research Laboratory
Airbase and Environmental Technology Division
Tyndall Air Force Base, FL 32403-5323
Prepared for presentation at the 2000 Spring National Meeting
AMERICAN INSTITUTE OF CHEMICAL ENGINEERS
Atlanta, GA
March 6,2000
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PROJECT BACKGROUND
This project is sponsored by the Strategic Environmental .Research & Development Program (SERDP) in
response to the Compliance New Start Number 2 Statement of Need (CPSON2) for FY98, entitled, "VOC (Volatile
Organic Compound) Control Technology for Aircraft Painting and Depainting Facilities." Driven by the Clean Air
Act Amendments of 1990, quantities of VOCs and Hazardous Air Pollutants (HAPs) in coatings are being reduced,
thereby reducing emissions of ozone precursors and toxic compounds from painting operations. However,
additional controls are desirable or necessary to meet corrosion specifications in some instances, such as aircraft
coating. The National Emissions Standard for Hazardous Air Pollutants (NESHAP) specific to aircraft painting will
require the Department of Defense (DoD) to either implement volatile hazardous air pollutant (VHAPj control
technology or replace existing coating formulations. Because efforts to develop replacement coatings have met with
only mixed success, implementation of control technology appears to be the most promising near-term solution.
Project Description
This project is designed to evaluate the feasibility of using a membrane-supported extraction and
biotreattnent process to meet NESHAP standards for aircraft painting and depainting facilities. The proposed
system will both minimize the treated volume and concentrate the VOCs within that treated volume to further
reduce the size and cost of the control equipment. These advantages make this VOC treatment option viable over a
broad range of spray booth sizes. This will be accomplished using the partitioned recirculation flow reduction
technique and a novel VOC concentrating and biological treatment process, the Membrane BioTreatment (MET)
system.
In the MBT system, VOCs are first separated from the air stream, concentrated, then metabolized by
microorganisms, forming nonhazardous cell mass and carbon dioxide (CO2). Selective removal and concentration
of VOCs from the exhaust stream enable significant reduction in the volume directed to the final control device.
The system allows for independent optimization of each process: VOC removal from the air and VOC
biodegradation. The system uses microporous hollow fiber membrane contactors to mediate the extraction and
concentration of VOCs from the air into an organic stripping fluid (octanol) and to provide a physical support for
degradative microorganisms. Figure 1 is a schematic of the MBT system.
Makeup
Nutrient
Mixing
Tank
Exhaust
Gas
Cle
Ai
Membrane
Separation
Particulate
Prefilter '
in
b~* 1 ^
r 1"
[Stripping ^
Fluid
Storage
Tank )
• Recycled
' Stripping
Fluid
Nutrient
Recycle
-3 ^
Biomembrane
Effluent
Figure 1: MBT System Schematic
Gases enter a membrane separation/concentration (S/C) unit containing bundles of microporous
hydrophobic fibers in which vaporized HAPs and VOCs are transferred into a stripping fluid medium as shown in
Figure 2 (dark particles are VOCs). The medium serves as a pollutant sink and allows accumulation of significant
HAP/VOC concentrations.
Upon exiting the S/C unit, the stripping fluid is delivered to a biomembrane unit. There, the stripping fluid
is circulated past one side of another microporous membrane with VOC-degrading bacteria in a film on the opposite
side of the membrane. VOCs diffuse through the membrane pores (filled with organic stripping fluid) and are
selectively metabolized by the bacteria, as shown in Figure 3. The solvent is then collected in a storage vessel, and
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recycled through the S/C unit. Outputs from the overall MET system are clean air, CO2, and a mixture of water and
nonhazardous cell mass.
'.'.'.f'.:: :VOC-eoiitainiiig gas
Stripping flui
Figure 2: VOC Extraction in the S/C Unit Figure 3: Bioextraetion of VOCs
Separation/Concentration Experiments
Initial evaluations of mass transfer coefficients for the membrane module were conducted by
quantifying the removal of each individual VOC [wi-xylene, toluene, methyl ethyl ketone (MEK)j from an air
stream. Experiments were performed to determine the effect of airflow rate, stripping fluid flow rate, air .
stream VOC concentration, and stripping fluid VOC concentration on overall mass transfer coefficients. Inlet
air stream concentrations were set in the range of 50 to 350 ppm on a mole per mole basis with a syringe
infusion pump. Airflow rates between 1 and 5 ftVmin (28 and 140 L/min) and stripping fluid flow rates
between 0.1 and 1.0 L/min were studied. Contact times for both streams were calculated based on the
geometry of the membrane unit. The air-side contact time was 0.1 - 0.4 sec, and the stripping fluid contact
time ranged from 6 to 60 sec. Samples of inlet air, outlet air, and the stripping fluid reservoir were taken at
regular intervals and analyzed to allow calculation of the overall mass transfer coefficient via an appropriate
design equation for the membrane contactor. Air samples were collected and analyzed by gas
chromatography using a flame ionization detector (GC/FID) immediately after they were withdrawn from the
sample port. Stripping fluid samples were placed into 1.5 -mL polypropylene microcentrifuge tubes and stored
headspace-free in a -20°C freezer until analysis by ultraviolet - visible (UV-Vis) spectrophotometry or high-
pressure liquid chromatography (HPLC) with a UV or refractive index (RI) detector.
Significant effort was aimed at testing the performance and ease of application of several coatings on
smaller bench-scale Celgard contactors. We acquired and tested a module from Compact Membrane Systems
(CMS) with an amorphous copolymer of perfluorodimethyldioxole and tetrafluoroethylene (PDD-TFE)
coating inside the fibers. While it was known that PDD-TFE would not have optimum transfer
characteristics, it was the only material that CMS, the only vendor identified and judged at that time to be
capable of applying in-situ coatings inside the fibers, would provide. MEK and /n-xylene were the VOCs
used in the VOC mass transfer performance (air to octanol) tests. Three conditions were examined for each
compound, in duplicate, for a total of 12 experiments. Airflow rate and VOC concentration were
experimental variables, while absorbent (octanol) flow was held constant. Experimental conditions were
chosen to emulate previous work with a Celgard Liqui-Cel module containing hollow fibers coated on the
outside surface with PDD-TFE. Replicates were not evaluated because the VOC concentration in the solvent
varied with time. Efforts were made to duplicate air and solvent flow rates, and VOC concentrations in the air
stream. The results of the testing were similar to those of previous testing using a module coated with PDD-
TFE on the outside of the fibers. These results, shown in Table 1, indicate that, with PDD-TFE coated fibers,
the major resistance to mass transfer may be in the coating. Table 2 shows the removal efficiencies obtained
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using PDD-TFE coating on the outside of the fibers. Because PDD-TFE has a relatively high resistance to
mass transfer of VOCs, the need for a better polymeric coating to improve process economics is indicated.
Table 1. Mass Transfer Coefficients
PDD-coated membranes, shell-side (outside) coating
Compound
transferred
m-xylene
MEK
Air Stream
Concentration
(ppm)
44
50
110
64
275
270
750
1050
2200
Flow
(L/min)
28
28
60
28
28
60
30
Loading'
(ppm/s)
120
130
290
370
1600
720
2000
6000
5500
Solvent Stream
Cone,
(mg/L)
6.2
6.2
6.2
6.0
6.3
5.9
550
105
1200
980
K0
(xlO~ cm/s)
0.85
0.91
0.96
1.0
1.3
1.6
0.7
2.0
9.4
4.3
PDD-coated membranes, tube-side (inside) coating
m-xylene
MEK
40
230
280
470
2800
5000
28
60
60
28
60
28
110
1300
1600
1300
16000
13000
4080
4300
850
8500
9500
5500
0.1
2.0
2.7
-4.0
2.0
5.3
'Indicates the relative rate of flow of VOC through the module; determined by dividing the VOC
concentration by the residence time of the air in the module (shell-side volume =175 mL).
Table 2, Removal Efficiencies
PDD-coated membranes, shell-side coating
Compound
transferred
toluene
MEK/toluene
Air Concentration
(ppm)
800
900
1300
500/250
850/650
Airflow
(L/min)
105
60
30
60
30
Loading
(ppm/s)
8000
5100
3700
2800/1400
2400/1900
Removal
Efficiency (%)
74
76
78
80/60
80/70
Operating equations were derived to describe the membrane separation processes. The final result for the
separation/concentration unit was a design equation that relates concentration, partition coefficient, membrane
surface area, and flow rate to an overall mass transfer coefficient, K0. The K0 is based on the overall system driving
force and is defined by a sum of resistances model. In the equation shown below for K0 in the S/C unit, the
concentration (C) subscripts A and O denote the air and octanol phases, and subscripts 1 and 2 represent inlet and
outlet conditions, respectively. P is the air/octanol equilibrium partition coefficient, Q is the volumetric flow of the
respective phases [cm3/sec], and Am is the membrane surface area [cm2].
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In
C
At/ —
P
C
A\ _
p
K0 =
Module design
Discussions were held with Applied Membrane Technologies (AMT) regarding their standard parallel flow,
stainless steel cylindrical module and potential designs for improving the air distribution and reducing air-side
pressure drop, AMT was contracted to deliver a membrane module using fibers that are coated on the outside with
plasma-polymerized silicone rubber at a nominal thickness of 1 um. One of the concerns with a parallel-flow
contactor design is the unknown effectiveness of the air-to-fiber contact area. Though the cylindrical parallel-flow
design of the existing AMT module does not lend itself to high efficiency, it was used in preliminary testing to
gather data for the design of a cross-flow bench-scale module.
Five 48-minute tests were conducted with air flowing through the shell side of the module, three using m-
xylene as the pollutant and two with MEK. Results are presented in Table 3. The air flow was typically 60 L/min
and VOC removal ranged from 56 to 83 percent with average overall mass transfer coefficients, K0, of 4.4x10"6 to
S.OxlO"5 cm/sec.
Table 3. Air in Shell Tests - Cylindrical Parallel-flow AMT Module
Parameter
Run ID
Total run time (min)
Airflow (L/min)
Avg inlet VOC air concentration (molar ppm)
Average VOC removal (%)
Average mass transfer coefficient, K0 (cm/s)
m-xylene 1
48
60
65
56
4.40E-06
m-xylene 2
48
60
190
77
8.30E-06
m-xylene 3
48
60
185
70
1.20E-05
MEK1
48
28
186
83
2.10E-05
MEK 2
48
60
1350
78
5.00E-05
In actual operation, contaminated air flows through the shell side of a cylindrical design and octanol, or
another stripping fluid, is pumped through the tube, or lumen side. The initial set of tests on the AMT cylindrical
module was ran in this manner. Because of the distribution and contact shortcomings encountered, AMT suggested
that a second series of tests be conducted with the air flowing through the fibers. Therefore, a second set of tests was
run with the air flowing through the fibers and octanol on the shell side. Twelve runs were conducted using m-
xylene as the pollutant. These shorter (34 min) tests were conducted with airflow rates through the lumens ranging
from 5.6 to 10.3 L/min at pressure drops from 11.5 to 20 in. H2O (292 - 508 mm/H2O). Results are shown in Table
4.
Table 4. Octanol in Shell Tests - Cylindrical Parallel-flow AMT Module
Parameter
Run ID
Total run time (min)
Air-side Pressure Drop
in.H2O(mm/H,O)
Airflow (L/min)
Avg inlet VOC air
concentration (molar ppm)
Average VOC removal
(%)
Average mass transfer
coefficient, Ka (cm/s)
Bi-xylene
7
34
11.5
(292)
5.6
68
91
1.60E-06
m-xylene
S
34
11.0
(279)
5.6
84
91
1.90E-06
m -xylene
9
34
11.5
(292)
5.6
261
80
8.20E-07
m -xylene
10
34
11.0
(279)
5.6
684
97
2.30E-06
Bi-xylene
11
34
16.0
(406)
8.6
92
51
8.60E-07
m -xylene
12
34
16.0
(406)
8.6
125
44
6.00E-07
m -xylene
13
34
16.5
(419)
8.6
457
93
3.60E-06
IB — xylene
M
34
16.0
(406)
8.6
499
89
2.50E-06
m -xylene
15
34
20.0
(508)
103
76
60
5.10E-06
m -xvlene
16
34
20.0
(508)
10.3
105
52
UOE-06
m -xylene
17
34
20.0
(508)
10.3
274
73
1.60E-06
m-xylene
18
34
20.0
(508)
10.3
697
85
2.00E-06
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The Rvalues (6.0xlO"7 to S.lxlO"6 cm/sec) for this set of runs were consistently and significantly lower than for
the air-in-shell results. As airflow decreases, or as inlet concentrations increase, average VOC removal (overall)
increases, but K0, which is affected by other physical factors, may be impacted negatively. High removal
efficiencies (93 and 97 %) were achieved with octanol in the shell, and high mass transfer coefficients (2.1xlO~5 and
S.OxlO""1) were achieved with air in the shell. The challenge now is to simultaneously achieve high removal
efficiencies and rates. These inconsistencies may be a result of inefficient contact between the fluids and membrane
surfaces. Method detection limits were less than 5 ppmv for the concentrations of wi-xylene and MEK in air and
octanol using HPLC.
Biotreatment accomplishments
A series of experiments using hollow-fiber modules were performed to establish the efficacy of the
proposed biotreatment module for enhanced VOC removal from the octanol. Liquid/liquid stripping efficiency of
MEK (oetanol to water) was determined for the biotreatment module both with and without a biofilm present. Three
aqueous (absorbent) flow rates were examined, with a constant 5000-ppm MEK concentration in octanol and an
octanol flow rate of 290 mL/min. Samples were taken in duplicate. Each mass transfer rate reported in Table 4
represents an average of samples taken at four time points, and has a variance of 0.17. Results shown in Table 5
(comparing the 301 mL/min flow, abiotic vs. biofilm) indicate that the presence of a live biofilm enhanced MEK
removal by approximately 43 %.
Table 5. Biomembrane Mass Transfer
Experiment Type
Aqueous phase
Qaq,ra,s (mL/min)
Qoc..™! (mL/min)
MEK in octanol (ppm)
Mass transfer rate (g/m2h)
Abiotic
Filtered tap water
116 301
598
Biofilm
L-salts '
301
290
5000
1 .80 2.07
4.45
2.97
pH balanced trace nutrient source for microbiological organisms
Flat-sheet membrane reactor results
In all of these experiments, a flat-sheet membrane module was used; a basic schematic of the experimental
setup is shown in Figure 4. This unit was operated with continuous flow through the module and recirculation
through two equally sized reservoirs. The recirculation rate was sufficiently high (50 mL/min) to validate the
approximation that the fluid in the membrane module was well mixed. The VOC was always introduced on the side
opposite the film, so the two sides of the membrane will be referred to as the film side and the feed side.
250 mL aqueous medium
Figure 4. Flat-sheet biofilm reactor
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70
60 *
gso
c
.2 40
-u
ctf
I 30
0)
o
o 20
Q
M
10 -
• B
* Film -side
• Feed-side
100
500
600
200 300 400
Time (min)
Figure 5. M-l biofilm degradation of MEK in aqueous/octanol system
A biofilm containing an MEK-degrading bacteria (M-l) was established, Octanol containing MEK was
present on the feed side of the membrane. Water and octanol were recirculated between the membrane module and
equally sized reservoirs. As indicated in Figure 5, the concentrations of MEK in the octanol phase decreased more
rapidly than the aqueous-phase MEK concentration increased. Consistent biodegradation of MEK occurred" over the
course of a 9-hour period, following transfer of MEK from the octanol across the membrane to the biofilm. This
proved that transfer with biodegradation would occur under conditions where the organisms were in close contact
with octanol. It also indicated that while M-l would grow, slowly utilizing octanol as a carbon source (data not
shown), octanol metabolism would not severely inhibit MEK degradation.
M-l was grown in a film and exposed to a mixture of MEK and toluene in water on the feed side. The
concentration of MEK in the feed stream was at 25 ppm through day 5, then increased to 50 ppm through day 25,
when it was again decreased to 25 ppm. The toluene concentration in the feed was zero until day 25, when it was
increased to 25 ppm. Despite prior growth on MEK, the film rapidly degraded a substantial portion of the
toluene fed, decreasing the rate of MEK degradation in the process. This result was surprising, due to the fact
that M-l is an organism isolated from soil using MEK as the enrichment carbon source. However, since the soil
was subjected to long-term exposure to motor fuels, toluene degradation is to be expected.
A biofilm, containing both M-l and an m-xylene degrading bacteria (X-l), was established and fed toluene
and MEK in an aqueous mixture, each at a concentration of 50 ppm in the feed stream. After 2 hours of continuous
flow, sampling was begun. Toluene was rapidly and almost completely degraded, while MEK was degraded to a
significantly lesser extent. This suggests that both M-l and X-I preferentially degrade toluene, to the detriment of
MEK degradation.
A biofilm containing M-l and X-l was exposed to an octanol feed mixture containing 50 ppm each of
MEK and toluene. The octanol flow rate was 2 mL/min, while the aqueous flow rate was 7 mL/min. Toluene did
not appear in the aqueous stream over the course of the experiment. Essentially all of the toluene was degraded, as
was one-third of the MEK (data not shown).
A mixed organism biofilm culture containing M-l and X-l was fed a mixture of MEK, toluene, and m-
xylene from an aqueous stream (50 ppm of each compound). The culture's behavior and VOC removal capability
were investigated, and results are shown in Figure 6. Neither toluene nor m-xylene appeared in the aqueous phase,
and MEK appeared at low levels (<5 ppm).
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30
25 -
20
35
30
25
20
15
10
*
B
A
3
ti
O
• !•«
-W
cj
in
«
OJ
o
d
o
A Toluene in
* Toluene out
25 -
20 -
15 -
10
X m-xylene in
• m-xylene out
10
20 30 40 50
Time (hr)
60
70
80
Figure 6. M-l and X-l mixed biofilm degradation of MEK, toluene, and /H-xylene
These results have significant implications for the design and operation of the biotreatment system. For
example, since M-l preferentially degrades toluene over MEK, a single biofilm module may be inadequate. Several
strategies may need to be evaluated, including replacement of M-l with an organism exhibiting higher substrate
specificity for MEK, establishment of an MEK-degrading culture in the aqueous recirculation tank, or staging of
biofilm modules containing different bacterial populations. The mixed culture results are more difficult to analyze.
It may have been that X-l dominated the biofilm and that the low MEK degradation rates are attributable to low
population size for M-l. Such issues must be investigated more completely.
Shake flask results
The apparent inhibition of MEK degradation by toluene and m-xylene was investigated in a series of shake
flask experiments. MEK and m-xylene/toluene have different solubilities in an aqueous medium. Under certain
conditions in the biofilm reactor, MEK from the octanol phase will partition into the aqueous nutrient medium faster
than it can be degraded by the biofilm. This will result in exposure of the biofilm to an aqueous-phase MEK
concentration. The biofilm must be able to maintain degradative activity in the presence of this aqueous-phase
MEK. The film must also actively degrade MEK. Given the results obtained from the biofilm experiments,
suspended cell studies were undertaken to further elucidate the mechanisms of degradation of the two organisms.
X-l was grown on toluene and m-xylene, to determine its substrate preference. As indicated in Figure 7,
only one apparent growth phase results, suggesting that toluene and m-xylene are equally preferred and that
degradation of either does not inhibit degradation of the other.
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o
o
0.3
0.25 -
0.2 -
0.15 -
ft °'H
° 0.05 H
0
6
10
12
14
Time (hr)
Figure 7. X-l growth on toluene and m -xylene
Growth studies of M-l were performed with various mixtures of MEK, toluene, and /«-xylene. The cell
density, protein concentration, and concentration of the three substrates were monitored during the growth. The
results of these studies are summarized in Table 6. Since multiple growth phases were observed, multiple growth
rates are reported, with the primary carbon source denoted in parentheses. These results indicate that M-1 degrades
toluene and m-xylene preferentially to MEK, and that the growth rate of M-1 on MEK is reduced as a result of
toluene and m-xylene metabolism. It is unclear whether inhibitory byproducts are formed by M-l during aromatic
biodegradation.
Table 6. Growth of M-l on Mixed Substrates
Substrate
MEK(200ppm)
+ toluene (25 ppm)
MEK (60 ppm)
+ w-xylene (35 ppm)
Specific Growth Rate (h~l)
0.35 (toluene)
0.22 (MEK)
0,45 (w-xylene)
0.11 (MEK)
Growth patterns
sequential phases consuming
toluene, then MEK
sequential phases consuming
m-xylene, then MEK
FUTURE APPROACH
We are evaluating the mass transfer characteristics of bench-scale modules using single-component air
streams containing MEK, m-xylene, and toluene at concentrations varying from 50 to 200 ppm, Octanol has been
used as the VOC stripping fluid, but it has been found to swell the fibers. As a consequence, silicone oil, which does
not cause the fibers to swell, is the current transfer fluid of choice. Experiments will be performed to determine the
effect of airflow rates, stripping fluid flow rate, air stream VOC concentration, and stripping fluid VOC
concentration on the overall mass transfer coefficient using silicone oil. Work will continue in evaluating the mass
transfer rates of various VOC mixtures including binary and tertiary mixtures at total VOC levels from 50 to 300
ppm. Preliminary targets for mass transfer rates for removing VOCs from air and VOC degradation rates are 10"5
cm/sec and 3 x 10"lomg/cell-hr, respectively.
It is necessary to operate a biofilm reactor for 2 to 3 months in order to determine the effectiveness of the
degradative mixed culture. During this period, the aqueous-phase pressure drop, the cell mass sloughing rate, and
the biodegradation rate will be monitored. These variables will enable calculation of the effectiveness of the
biotreatment module for degradation of specific VOCs, and will provide valuable insight into the extent to which
biofouling might occur and the severity of the impact of biofouling on degradative performance.
SUMMARY
VOC removal efficiencies in excess of 75% have been achieved using a microporous hollow fiber
membrane module. This module was coated on the air-contacting side with either PDD-TFE or plasma-
polymerized silicone rubber. The VOC-laden air had a contact time of less than 0.1 sec with the coated membrane.
Operation of these modules was not optimized, and removal efficiencies in excess of 90% have been observed.
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Extraction of specific compounds from the air stream into octanol was observed to be unaffected by the presence or
concentration of other VOCs in the air stream, but extraction increased with VOC concentration in the air stream.
The membrane-supported biofilm modules successfully removed VOCs from the recirculating octanol
stream. Degradation of the aromatic compounds investigated (toluene, m-xylene) was achieved; these compounds
were not observed in the aqueous phase above the biofilm. MEK biodegradation is problematic, appearing to be
partially inhibited by toluene and m-xylene. Further mechanistic studies are required to ascertain the underlying
mechanism.
Overall, the MBT process continues to exhibit the potential for development into a robust, flexible, low-cost
treatment system suitable for implementation at facilities subject to the NESHAP for Aerospace Manufacturing and
Rework Facilities.
10
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NRMRL-RTP-P-496
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO,
EPA/600/A-00/004
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Membrane-mediated Extraction and Biodegradation
of VOCs from Air
S. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7.AUTHOR(sis. Peretti/R. Shepherd (NCSU), R. Clayton/
D. Proffitt (ARCADIS), N.Kaplan (EPA), and
J. Wander (USAF)
8. PERFORMING ORGANIZATION REPORT NO,
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
North Carolina State Univ. .Box 7905, Raleigh, NC
27695; ARCADIS Geraghty and Miller, 4915 Prospec-
tus Dr., Durham, NC 27713; and Air Force Rsrch
Lab., Tyndall Air Force Base, FL 32403-5323
11. CONTRACT/GRANT NO.
NA (SERDP)
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Air Pollution Prevention and Control Division
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Published paper;6/98-2/00
14. SPONSORING AGENCY CODE
EPA/600/13
15. SUPPLEMENTARY NOTES
project officer is Norman Kaplan, Mail Drop 4, 919/541-
2556. AIChE Spring Meeting, S^/OO, Atlanta, GA.
16. ABSTRACT
paper discusses a project designed to evaluate the feasibility of using
a membrane- supported extraction and biotreatment process to meet the National
Emissions Standard for Hazardous Air Pollutants (NESHAP) for aircraft painting
and depainting facilities. The proposed system will both minimize the treated vol-
ume and concentrate the volatile organic compounds (VOCs) within that treated vol-
ume to further reduce the size and cost of the control equipment. These advantages
make this VOC treatment option viable over a broad range of spray booth sizes.
This will be accomplished using the partitioned recirculation flow reduction techni-
que and a novel VOC concentrating and biological treatment process, the Membrane
BioTreatment (MET) system. In the MET system, VOCs are first separated from
the air stream, concentrated, then metabolized by microorganisms, forming cell
mass and carbon dioxide. Selective removal and concentration of VOCs from the
exhaust stream enable significant reduction in the volume directed to the final con-
trol device. The system allows for independent optimization of each process: VOC
removal from the air and VOC biodegradation. The system uses microporous hol-
low fiber membrane contactors to mediate the extraction and concentration of VOCs
from the air into an organic stripping fluid (octanol),
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution Aircraft
Spray Painting Extraction
Organic Compounds Biodeterioration
Volatility
Membranes
Paint Removers •
Pollution Control
Stationary Sources
Volatile Organic Com-
pounds
QIC
07A
06A.11L
13 B
13 H
07C
20 M
11G,06P, 06C
UK
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport)
"Unclassified
21. NO. OF PAGES
10
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73J
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