vvEPA
United States
Environmental Protection
Agency
EPA/540/S5-90/007
March! 992
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Technology Demonstration
Summary
: - - . ^ . f
DuPont/Oberlin
Microfiltration System
Palmerton, Pennsylvania
In April and May 1990, the U.S. Envi-
ronmental Protection Agency (EPA),
under the Superfund Innovative Tech-
nology Evaluation (SITE) program,
demonstrated DuPont/Oberlin's micro-
filtration system at the Palmerton Zinc
Superfund (PZS) site In Palmerton,
Pennsylvania. The microfiltration sys-
tem combines DuPont's Tyvek* T-980
filter media with Oberlin's automatic
pressure filter and Is designed to re-
move solids larger than 0.1 u. in diam-
eter from liquid wastes. The
mlcrofiltration system demonstrated at
the PZS site was evaluated primarily In
terms of its ability to remove metals
(mainly zinc) and partlculates from the
contaminated groundwater on site,
while producing a dry filter cake and
filtrate that meet applicable disposal
requirements.
The results showed that the
microfiltration system achieved zinc
and total suspended solids (TSS) re-
moval efficiencies of about 99.95%, and
a filter cake solids content of 41%. The
filter cake contained no free liquids,
and a composite sample from all the
demonstration runs passed both the
extraction procedure (EP) toxicity test
and the toxicity characteristic leaching
procedure (TCLP) test. The filtrate met
all National Pollutant Discharge Elimi-
nation System (NPDES) permit limits
for metals and TSS, but not for pH. The
filtrate pH was typically 11.5, while the
NPDES upper pH limit Is 9.
This Summary was developed by
EPA's Risk Reduction Engineering
Laboratory, Cincinnati, OH, to announce
key findings of the SITE program dem-
onstration that Is fully documented In
two separate reports (see ordering in-
formation at back).
Introduction
In response to the Superfund Amend-
ments and Reauthorization Act of 1986
(SARA), the EPA's Office of Research
and Development (ORD) and Solid Waste
and Emergency Response (OSWER) have
established a formal program to acceler-
ate the development, demonstration, and
use of new or innovative technologies that
offer permanent, long-term cleanup solu-
tions for hazardous wastes. This program
is called the SITE program. One compo-
nent of the SITE program is the demon-
stration program, through which EPA
evaluates field- or pilot-scale technologies
Printed on Recycled Paper
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that can be scaled up for commercial use.
The main objective of the demonstration
program is to develop performance, engi-
neering, and cost information for innova-
tive technologies. This information may be
used to compare the technology's effec-
tiveness and cost to other alternatives in
order to make sound judgements regard-
ing the applicability of the technology for a
specific site.
In February 1988, E.I. DuPont de
Nemours & Company, Inc. (DuPont), and
Oberlin Filter Company (Oberlin) submit-
ted to EPA a joint proposal to demon-
strate their microfiltration technology un-
der the SITE program. EPA selected the
DuPont/Oberlin microfiltration technology
for demonstration under the SITE program
in June 1988.
The demonstration was conducted at
the PZS site in Palmerton, Pennsylvania,
during April and May 1990. During the
last 70 yr, zinc smelter operations have
resulted in 33 million tons of zinc residue
accumulating and forming an extensive
cinder bank at the site. The cinder bank
has contaminated surrounding areas, in-
cluding groundwater and surface water.
The shallow groundwater at the PZS site
was selected for evaluating the
microfiltration system. The groundwater is
primarily contaminated with high levels of
zinc (400 to 500 mg/L) and trace levels (^
1 mg/L) of cadmium, copper, lead, and
selenium.
The technology demonstration had four
objectives:
• Assess the technology's ability to re-
move zinc from the groundwater un-
der different operating conditions
• Evaluate the microfiltration system's
ability to dewater the metals precipi-
tate from the treated groundwater
« Determine the system's ability to pro-
duce a filtrate and filter cake that meet
applicable disposal requirements
• Develop information required to esti-
mate the operating costs for the treat-
ment system, such as electrical power
consumption and chemical doses
Technology Description
DuPont/Oberlin's microfiltration technol-
ogy is designed to remove solids from
liquid wastes, it is suitable for treating
landfill leachate. groundwater, and liquid
Industrial wastes containing metals. Since
the microfiltration system is designed to
remove particles down to 0.1 u. in diam-
eter, dissolved contaminants must first be
converted to a particulate form. For ex-
ample, groundwater with dissolved metals
must first be treated with a precipitating
agent, such as lime, to convert the dis-
solved metals into particulate form, such
as metal hydroxides. After the dissolved
metals are converted to a particulate form,
the liquid waste can be filtered through
the microfittration unit.
The microfiltration unit produces two end
products: filter cake and filtrate. To pro-
duce a filter cake that has a low moisture
content and a filtrate that has a low solids
content, DuPont/Oberlin normally uses a
filter aid or filter aid/cake stabilizing agent.
For the SITE demonstration, DuPont se-
lected a silicate-based filter aid/cake sta-
bilizing agent known as ProFix, which is
manufactured by EnviroGuard, Inc., of
Houston, Texas.
A schematic of the DuPont/Oberlin
microfiltration unit is shown in Figure 1.
This microfiltration unit is an automatic
pressure filter (APF) that operates on pres-
sure signals and uses a low-cost, Tyvek®
T-980 membrane filter (Tyvek8), a thin,
durable spunbonded olefin fabric devel-
oped by DuPdnt. The APF, developed by
Oberlin, has two chambers—an upper
chamber for feeding waste through the
filter media, and a lower chamber for col-
lecting the filtrate. The Tyvek® filter lies
between these two chambers. The APF
unit used in the demonstration was 64 in.
long, 33 in. wide, and 83 in. high. It
weighed approximately 1,300 Ib and had
a filtering area of 2.4 sq ft. The system
can be manufactured as an enclosed unit,
requires little attention during operation, is
mobile, and can be trailer-mounted. A typi-
cal configuration of the DuPont/Oberlin
microfiltration system (including pretreat-
ment of dissolved metals) is shown in
Figure 2.
A typical microfiltration cycle consists of
four steps: (1) initial filtration, (2) main
filtration and cake forming, (3) cake dry-
ing, and (4) cake discharge. The process
begins with liquid waste being pumped,
usually from a waste feed tank, into the
upper chamber. During the first minute of
filtration, or the initial filtration step, the
filtrate is usually recycled to the waste
feed tank. At the end of 1 min, when filter
cake buildup is sufficient to produce a
clear filtrate, recirculation stops and the
main filtration step begins. During the main
filtration step, solids continue to accumu-
late and form a cake on the Tyvek* while
filtrate drains from the lower chamber to a
filtrate collection tank. When the pressure
drop across the filter is about 45 psig, the
waste feed valve closes, pumping of liq-
uid waste feed to the microfiltration unit
stops, and the cake drying step begins.
Pressurized air (typically, at a blowdown
Pressurized Air
Air Cylinder
Used TyvaK*
Rlter Cake
Clean Tyvek"
Filter Belt
Filtrate Chamber
Filter Discharge
Figure 1. Schematic of DuPont/Oberlin microfiltration unit.
2
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Groundwater
Filtrate
To Disposal
Air
Lime Slurry
Tank
Filter Cake
Filter Cake
Sto,
Used Tyvek31
ProFix Slurry Tank
Microfiltratidn'
Unit
Figure 2. DuPont/Oberlin microfiltration treatment system.
pressure of 35 to 45 psig) is fed into the
upper chamber to dry the cake. After air
breaks through the cake, drying continues
for a preset time, known as the blowdown
time. During this step, any remaining liq-
uid is forced through the Tyvek* and is
recycled to the waste feed tank. Immedi-
ately following the cake drying step, the
upper chamber is lifted, clean Tyvek* is
drawn from a roll into the microfiltration
unit for the next cycle, and the filter cake
is discharged.
Demonstration Procedures
The procedures followed during the Du-
Pont/Oberlin microfiltration technology
demonstration were developed to evalu-
ate the technology's effectiveness in treat-
ing contaminated groundwater from the
PZS site. Groundwater samples from the
PZS site were collected in June 1989 to
characterize the groundwater and identify
contaminants of concern for the technol-
ogy demonstration. In July 1989, DuPont
performed bench- and pilot-scale treat-
ability studies. An additional study to re-
fine the sampling and analytical techniques
used during the pilot-scale study was con-
ducted in October 1989. Based on the
PZS site groundwater characteristics and
the results of treatabilrty tests, a demon-
stration plan was prepared detailing sam-
pling, analytical, quality assurance, and
health and safety procedures. Following
EPA's approval of the demonstration plan,
site preparation and equipment mobiliza-
tion for the demonstration began in mid-
March 1990. The actual demonstration of
the DuPont/Oberlin microfiltration system
began in April 1990. The demonstration
was divided into three stages: (1) site
preparation (2 weeks), (2) technology dem-
onstration (4 weeks), and (3) site demobi-
lization (2 weeks). The demonstration was
completed in May 1990.
This section summarizes demonstration
procedures, including the waste charac-
terization, treatability studies, site prepa-
ration, and technology testing activities.
Waste Characterization
A detailed waste characterization was
performed to (1) determine the metals con-
centration in the groundwater and (2) iden-
tify the levels of complexing agents (such
as chloride, ammonia, cyanide, and sul-
fide) and oil and grease that could affect
the microfiltration system's performance.
Samples were collected from two onsfte
wells to characterize the groundwater.
Groundwater samples indicated that the
shallow groundwater was contaminated
with high levels of zinc (400 to 500 mg/L)
and trace levels of cadmium (1 mg/L),
copper (0.02 mg/L), lead (0.015 mg/L),
and selenium (0.05 mg/L). Neither
complexing agents nor oil and grease were
present at levels that could affect the
microfiltration system's performance.
Treatability Studies
Treatability studies were conducted to
evaluate treatment effectiveness and de-
termine initial operating conditions for the
microfiltration unit used for the SITE dem-
onstration. Using groundwater from the
PZS site, DuPont/Oberlin performed
bench-scale treatability studies to (1) test
several precipitating agents and filter aids
that could be used to pretreat the ground-
water and (2) develop initial operating con-
ditions for pilot-scale studies. Groundwa-
ter from two onsite wells was mixed in
equal volumes for the studies. During the
bench-scale studies, a jar test apparatus
precipitated the, metals, and a vacuum
filtration apparatus with a 0.45-u. mem-
brane filter dewatered the metals precipi-
tate. The results indicated that the Du-
Pont/Oberlin process could meet appli-
cable limits for filtrate discharge into a
local waterway.
.Following the bench-scale treatability
studies, pilot-scale studies were performed
using the same batch of groundwater. The
purposes of the; pilot-scale studies were
to (1) select precipitating agent(s) and fil-
ter aid(s) and (2) develop initial operating
conditions for the demonstration. The pi-
lot-scale studies involved 10 experiments
on a 0.0845-sq ft microfiltration unit, fol-
lowed by two test runs using a 2.4-sq ft
unit. The results showed (1) greater than
99% metals removal from groundwater,
(2) a TSS concentration of 44 mg/L, and
(3) 34% solids in the filter cake. Operating
conditions were as follows: a precipitation
pH of 10, a filter aid (EnviroGuard) dose
of .11.1 g/L, a blowdown pressure of 45
psig, and a blowdown time of 2 min. These
operating conditions were used to design
an experimental matrix for the SITE dem-
onstration.
Site Preparation
After a suitable location was selected
for the demonstration at the PZS site,
required support services, facilities, and
equipment were ordered and installed.
Specifically, EPA arranged utility connec-
tions, ordered and rented specialty equip-
ment, and supervised and directed instal-
lation.
Approximately 10,000 sq ft of relatively
flat area was needed for the microfiltration
system and support facilities, such as stor-
age tanks, an office and field laboratory
trailer, and a parking area. Crushed gravel
was laid and compacted on the existing
ground to form a level surface and mini-
mize muddy conditions resulting from rain
or snow. A temporary enclosure covering
approximately one half of the demonstra-
tion area was erected to provide shelter
for the microfiltration system during in-
clement weather. To contain any spills
during the demonstration, secondary con-
tainment was provided as needed. A 6-ft
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chain-link fence was constructed along the
perimeter of the demonstration area to
prevent unauthorized entry. Utilities re-
quired for the demonstration included wa-
ter, electricity, and telephone service.
A week before the demonstration, about
6,000 gal of contaminated groundwater
was collected for all the test runs to mini-
mize variation in groundwater characteris-
tics from run to run. The groundwater was
stored in a 6,000-gallon waste feed tank
located In the secondary containment area.
Technology Testing
After the site was prepared and the
microfiltration unit and support facilities
were Installed, DuPont/Oberlin conducted
startup testing of its demonstration equip-
ment. During startup, the microfiltration
system and connected support facilities
were checked for leaks and proper opera-
tion.
The demonstration testing program in-
volved evaluating (1) the performance of
the microfiltration system by varying the
chemical parameters (pH and filter aid/
cake stabilizing agent dose) and filter pa-
rameters (blowdown pressure and
blowdown time), (2) the reproducibility of
the microfiltration system performance, and
(3) the reusability of the Tyvek* fitter me-
dia. The experimental program was car-
ried out In four phases. In Phase 1, chemi-
cal operating parameters were varied, and
the filter operating parameters were kept
constant. In Phase 2. the fitter operating
parameters were varied, and the chemical
operating parameters were kept constant.
Phase 3 runs were performed to evaluate
the reproducibiltty of the microfiltration
system's performance. Phase 4 runs were
performed to evaluate the reusability of
the Tyvek* filter.
Figure 3 summarizes the operating con-
ditions for the demonstration runs. During
the demonstration, the optimum chemical
operating conditions and filter operating
conditions were determined in Phases 1
and 2, respectively. Run 5 conditions were
selected as the optimum operating condi-
tions for Phase 1; these were set as the
chemical operating conditions for Phase
2. Phases 3 and 4 were performed at Run
13 conditions because these conditions
were selected as the overall optimum
chemical and filter operating conditions.
This experimental design assumed that
the chemical and filter operating param-
eters do not interact. Although this as-
sumption is not critical to evaluating the
microfiltration system based on the tech-
nology demonstration objectives, the tech-
nology developers, agreed with this as-
sumption based on their experience.
Liquid and solid samples were collected
from several locations in the treatment
system. Sampling locations for liquids in-
cluded the (1) influent (raw groundwater)
line to the precipitation tank; (2) influent
line to the microfiltration unit; and (3) fil-
trate line from the collection tank. The
fitter cake solids were sampled directly
from the microfiltration unit. EPA-approved
sampling, analytical, quality assurance and
quality control procedures were followed
to obtain reliable data. Details on these
procedures are presented in the Demon-
stration Plan.
Table 1 identifies critical parameters
measured during the demonstration. Met-
als and TSS were measured to estimate
the removal efficiencies and determine
whether the filtrate met the applicable dis-
charge limits. Free liquids and moisture
content of the fitter cake were measured
to determine whether the fitter cake passed
the paint filter liquids test (that is, tt con-
tained no free liquids) and to determine
the percent solids in the filter cake, re-
spectively. In addition, pH was measured
to control the precipitation pH and deter-
mine whether the filtrate met applicable
discharge limits.
Results
This section summarizes the analytical
results for critical parameters for the over-
all optimum condition runs (13,19, 20, 21,
and 22).
The total zinc concentration in the
untreated groundwater in Runs 19 and 20
(reproducibility runs performed at Run 13
Table 1. Critical Parameters
Solids Liquids
Free Liquids
Metals (total zinc)
Moisture Content
Metals (total and
dissolved)
Total Suspended
Solids
pH
Run No.
Precipitation
PH
ProFix Dose
(9/L)
Blowdown
Time (mm)
Blowdown
Pressure (psig)
Phase 1 Chemical Parameter Runs
1
2
3
4
5
6
7
8
9
8
9
10
8
9
10
8
9
10
6
6
6
12
12
12
14
14
14
-
Slowdown Time *2
, "
Slowdown Pressure * 45
,
/ */ .-
Phase 2 Filter Parameter Runs
10
11
12
13
14
15
16
17
18
f , *
"' A '
' '
pH-Sf
"* _/.
Pro-fix Dose « 12
0.5
2
3
0.5
2
3
0.5
2
3
30
30
30
38
38
38
45
45
45
Phase 3 Performance Reproduclblllty Runs*
19
20
pH*9
PtoFlXDOSe = 12
Slowdown Time - 0.$
Blowdown Pressure =• 38
Phase 4 Tyvek" Reusability Runs*
21
22
pH*9
Fro fix Dose == 12
Bfowdown Time » &$
Blowdown Pressure = 38
• Performed at Run 13 Conditions
Figure 3. Operating conditions for the demonstration runs.
4
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operating conditions) was 465 mg/L. Fol-
lowing treatment, zinc concentrations were
reduced by 99.95% and 99.94%, resulting
in 0.24 and 0.28 mg/L of zinc in Runs 19
and 20, respectively. These removal effi-
ciencies agree with the removal efficiency
achieved in Run 13 (99.95%), indicating
that the microfiltration system's perfor-
mance in removing zinc was reproducible.
The TSS concentrations in the influent
to the microfiltration unit were 14,300 and
14,000 mg/L in Runs 19 and 20, respec-
tively. Following treatment, these concen-
trations were reduced by 99.95%, result-
ing in 7.7 and 6.8 mg/L of TSS in Runs 19
and 20, respectively. This removal effi-
ciency also agrees with the TSS removal
efficiency observed in Run 13 (99.91%),
indicating that the system's performance
in removing TSS was reproducible.
Figure 4 compares regulatory thresh-
olds with (1) the 95% upper confidence
limits (UCL) for filtrate metals (cadmium,
lead, and zinc) and TSS and (2) the fil-
trate pH level most frequently measured
for Runs 13, 19, and 20. The regulatory
thresholds are those that would need to
be met for discharge into a local waterway
(Aquashicola Creek) if a NPDES permit
'were required. The UCLs were calculated
using the one-tailed Student's t-test. To
calculate UCLs for cadmium and lead,
which were present below detection limits,
mean concentrations were estimated us-
ing standard statistical procedures. Figure
4 shows that the filtrate met the NPDES
limits for metals and TSS. However, the
NPDES upper limit for pH was not met.
The filter cake passed the paint filter
liquids test for all test runs. Average per-
cent solids in the filter cake ranged from
41.2 in Run 19 to 42.1 in Run 20. Of
these solids, about 80% to 90% were from
the filter aid/cake stabilizing agent, ProFix,
and the remaining were from (1) TSS
present in the untreated groundwater, (2)
metals precipitated during pretreatment,
and (3) any unreacted lime from pH ad-
justment.
As a quality control check, a mass bal-
ance was performed for zinc and TSS in
Runs 19 and 20. The difference between
zinc entering and leaving the system was
about 15%, which is within the analytical
precision for zinc measurement (± 25%).
Similarly, TSS measurements were also
found to be within analytical precision
(± 30%).
The results for zinc, TSS, and cake
solids for Runs 21 and 22 (Tyvek® reus-
ability runs) are presented in Figure 5. In
these runs, the same portion of Tyvek®
was used repeatedly for six cycles.
Samples were composited after the first
three cycles (Run 21) and the last three
cycles (Run 22). Figure 5 shows that the
microfiltration unit's performance was un-
affected even after multiple uses of the
Tyvek®.
Costs
The costs associated with the DuPont/
Oberlin microfiltration technology have
been estimated for the 12 cost categories
typically applicable to cleanup activities at
Superfund and Resource Conservation
and Recovery Act (RCRA) corrective ac-
tion sites. These costs are presented in
Table 2 for a 2.4-sq ft unit (demonstration
unit) and a 36-sq ft unit (largest avail-
able), along with annual operating and
maintenance costs and one-time costs.
The costs presented in Table 2 are con-
sidered order-of-magnitude (-30% to
+50%) estimates.
Conclusions
Based on the results from the SITE
program demonstration of DuRont/
Oberlin's microfiltration system, the fol-
Metals
10,000
1,000
$
oj
10
RT= 2,400
RT=700
Regulatory Threshold
RT=200
Zinc
40
30
20
10
TSS
RT=30
\i19A " _____
i.'fc'T^ Ii ............
=8.79 '
[Run \
\i3 iiirg j]
18.511|
iRuri ji
Figure 4. Comparison of filtrate quality for reproducibility runs with regulatory thresholds.
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0.01
2Snc Concentration, mg/L
1 10
100
1,000
10
TSS Concentration, mg/L
100 1,000
10,000
100,000
Cake Solids, %
30 40
50
lowing conclusions about the technology's
ability to treat groundwater at the PZS site
were drawn.
• The DuPont/Oberlin microfiltration
system achieved zinc and TSS re-
moval efficiencies of 99.69% to
. 99.99% and produced filter cakes
with 30.5% to 47.1% solids. Under
optimum conditions, zinc and TSS
removal efficiencies were about
99.95% and the filter cake solids
were about 41%.
• The filter aid/cake stabilizing agent,
ProFix, contributed a significant por-
tion (80% to 90%) of solids to the
filter cake. The remaining solids were
due to precipitated metals, TSS from
the untreated groundwater, and any
unreacted lime.
• The zinc and TSS removal efficien-
cies and the filter cake percent sol-
ids were unaffected by the repeated
use (6 cycles) of the Tyvek® filter
media. This indicates that the Tyvek8
media could be reused without ad-
versely affecting the microfiltration
system's performance.
• The filtrate met the applicable
NPDES permit limits for metals and
TSS at the 95% confidence level.
However, the filtrate did not meet
the NPDES upper permit limit for
pH. The filtrate pH was typically 11.5,
while the upper permit limit for pH is
9.
• The filter cake passed the paint filter
liquids test for all runs. Also, a com-
posite filter cake sample from the
demonstration runs passed the ex-
traction procedure (EP) toxicrty and
toxic'rty characteristic leaching pro-
cedure (TCLP) tests.
Untreated Groundwater
Influent to Microfiltration Unit
Filtrate
Filter Cake
Figure 5. Tyvek performance for reusability runs.
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Table 2. Estimated Costs Associated with DuPont/Oberlin Microfiltration Systems
Cost Categories
Estimated Costs (1990 $)
2.4sqfP
36sqfP
Site Preparation*
Permitting and Regulatory1'
Capital Equipment
Startup and Fixed1
Labor*
Supplies and Consumables'
Utilities!1
Effluent Monitoring1
Residuals and Waste Shipping, Handling,
and Transporting0
Analytical0
Equipment Repair and Replacement1
Site Demobilization*
Total One-Time Costs
Total Annual Operation and Maintenance Costs
209,200
2,300
47,800
80,000
133,400
16,900
5,500
15,000
3,700
36,000
2,500
30,000
369,300
213,000
843,200
11,200
231,800
80,000
133,400
220,000
82,500
15,000
55,200
36,000
7,000
85,000
1,251,200
549,100
Notes: ' During a 1-yr period, it is assumed that the 2.4-sq ft unit will treat about 525,600
gal and the 36-sq ft unit will treat about 7,884,000 gal.
* One-time costs.
0 Annual operation and maintenance costs.
•&V.S. GOVERNMENT PRINTING OFFICE: 1992 - 648-080/40199
-------
7779 EPA Project Manager, John Martin, is with the Risk Reduction Engineer-
Ing Laboratory, Cincinnati, OH 45268 (see below)
The complete report, entitled "Technology Evaluation Report: SITE Program
Demonstration oftheDuPont/OberlinMicrofihration Technology" (Order
No. PB92-153 410; Cost: $26.00, subject to change) discusses the results
of the SITE demonstration.
This report will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
A related report, entitled "Applications Analysis Report: DuPont/Oberlin Mhrofil-
tration Technology" (EPA/540/A5-90/007 dated October 1991), discusses the
applications and costs.
The EPA Project Manager can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for'Environmental
Research Information
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT NO. G-35
Official Business
Penalty for Private Use $300
EPA/S40/S5-90/007
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