THE ENVIRONMENTAL TECHNOLOGY VERIFICATION
PROGRAM ^
f X
&EPA
ETV
U.S. Environmental Protection Agency
NSF International
ETV Joint Verification Statement
TECHNOLOGY TYPE: ULTRAFILTRATION
APPLICATION: REMOVAL OF MICROBIAL CONTAMINANTS
PRODUCT NAME: SFD-2880 ULTRAFILTRATION MODULE
VENDOR: THE DOW CHEMICAL COMPANY - DOW WATER
SOLUTIONS
ADDRESS: 1691 SWEDE ROAD
MIDLAND, MI 48674
CONTACT: DARYL GISCH
PHONE: +1989-636-9254
EMAIL: DGISCH@DOW.COM
NSF International (NSF) manages the Drinking Water Systems (DWS) Center under the U.S.
Environmental Protection Agency's (EPA) Environmental Technology Verification (ETV) Program. The
DWS Center recently evaluated the performance of the Dow Water Solutions SFD-2880 ultrafiltration
(UF) module for removal of microbial contaminants under controlled laboratory challenge conditions.
The challenge tests were conducted at NSF's testing laboratory in Ann Arbor, MI. Testing of the SFD-
2880 UF module was conducted to verify microbial reduction performance under the product-specific
challenge requirements of the USEPA Long Term 2 Enhanced Surface Water Treatment Rule
(LT2ESWTR).
EPA created the ETV Program to facilitate the deployment of innovative or improved environmental
technologies through performance verification and dissemination of information. The goal of the ETV
Program is to further environmental protection by accelerating the acceptance and use of improved and
more cost-effective technologies. ETV seeks to achieve this goal by providing high-quality, peer-
reviewed data on technology performance to those involved in the design, distribution, permitting,
purchase, and use of environmental technologies.
ETV works in partnership with recognized standards and testing organizations, stakeholder groups
(consisting of buyers, vendor organizations, and permitters), and with the full participation of individual
technology developers. The program evaluates the performance of innovative technologies by developing
test plans that are responsive to the needs of stakeholders, conducting field or laboratory tests (as
appropriate), collecting and analyzing data, and preparing peer-reviewed reports. All evaluations are
conducted in accordance with rigorous quality assurance protocols to ensure that data of known and
adequate quality are generated and that the results are defensible.
NSF 10/34/EPADWCTR The accompanying notice is an integral part of this verification statement. January 2011
VS-i
-------
ABSTRACT
The Dow SFD-2880 UF module was tested for removal of microorganisms using live Cryptosporidium
parvum oocysts, endospores of the bacteria Bacillus atrophaeus, and the MS2 coliphage virus according
to the product-specific challenge testing requirements of the EPA Long-Term 2 Enhanced Surface Water
Treatment Rule (LT2ESWTR). Six modules were challenged with B. atrophaeus endospores and MS2.
Separate challenges were conducted for each organism. The B. atrophaeus endospores served as a
surrogate for Cryptosporidium. Two of the six modules were challenged with C. parvum oocysts to
experimentally confirm the surrogate relationship. The modules were operated at a target flux of 70
gallons per square foot per day (gfd), which equates to a flow of 40.3 gallons per minute (gpm).
The LT2ESWTR specifies that log removal values (LRV) be calculated for each module for each
organism, and then one LRV for each organism (LRVc-iEsi) be assigned from the set of LRVs. However,
the rule does not specify how the LRVC.TEST should be determined, instead, different methods are
suggested. For this verification, LRVs were calculated for each feed/filtrate sample pair, and an average
LRV was calculated for each module. For each challenge organism two LRVC_TEST are reported. The first
is the lowest average LRV from each challenge test. The second is the lowest individual sample point
LRV across all of the modules tested.
The LRVc-TEsi results for each organism by each method are displayed below in Table VS-i.
Table VS-i. LRVC-TEsx for Each Organism
Challenge
Organism
C. parvum
B. atrophaeus
MS2
Mean LRV
6.20
5.90
2.54
Lowest LRV
5.97
5.77
2.37
PRODUCT DESCRIPTION
The following information was provided by Dow and was not verified.
The Dow SFD-2880 UF membrane module measures 4.7 inches in diameter by 45.5 inches in length.
The membrane fibers are made of polyvinylidene fluoride (PVDF). Water flow through the membrane
fibers is outside to inside. The modules can operate in deposition (dead-end) or suspension modes. The
nominal pore size is 0.03 (im. The maximum recommended flux is 70 gfd, with a maximum
recommended feed pressure of 44 pounds per square inch (psi), and a maximum transmembrane pressure
of 30psi.
For this verification, the modules were operated in dead-end mode at the maximum recommended flux of
70 gfd, unless otherwise indicated.
VERIFICATION TEST DESCRIPTION
Challenge Organisms
The SFD-2880 module was tested for removal of microorganisms using live C. parvum oocysts,
endospores of the bacterial, atrophaeus (ATCC 9372, deposited as Bacillus subtilis var. niger), and MS2
coliphage virus (ATCC 15597-B1). B. atrophaeus served as surrogate for C. parvum, due to the high cost
and lack of availability of the amount of C. parvum required to test six modules. Virus reduction was
evaluated using MS2 for possible virus removal credits. MS2 is considered a suitable surrogate for
pathogenic viruses because of its small size of approximately 24 nanometers in diameter.
NSF 10/34/EPADWCTR
The accompanying notice is an integral part of this verification statement.
VS-ii
January 2011
-------
Methods and Procedures
All tests were conducted at the NSF International testing laboratories. The tests followed the procedures
described in the Test/QA Plan for the Microbial Seeding Challenge Study of the Dow Chemical Company
SFD-2880 Ultrafiltration Module. The challenge protocol was adapted from the ETV Protocol for
Equipment Verification Testing for Physical Removal of Microbiological and P articulate Contaminants,
and the USEPA Membrane Filtration Guidance Manual (MFGM), and met the product-specific challenge
test requirements of the LT2ESWTR.
Each of the SFD-2880 modules submitted for testing was challenged individually, and separate challenge
tests were conducted for each organism. The target flux for membrane operation was Dow's maximum
recommended value of 70 gfd at 25 °C, which equals a flow rate of 40.3 gpm. A total of six modules
were submitted for testing. The test plan called for testing only five modules, but the module tested for
Cryptosporidium parvum reduction developed an apparent membrane breach during the test. As a result,
Dow chose to submit a sixth module for testing so they could have a five-module data set demonstrating
the performance of fully integral modules.
The LT2ESWTR calls for the maximum challenge concentration to be 6.5 logio above the organism's
detection limit (3.16xl06). The goal for the B. atrophaeus challenges was to be able to measure log
reductions greater than six, so NSF elected to target IxlO7 CFU/100 mL to account for less than 100%
recovery of spiked challenge organism concentration. After all six modules were tested, and the feed
concentrations were found to be above 6.5 logio, NSF learned that the maximum 6.5 logic challenge level
is not just guidance, but rather the maximum allowed in the rule language in the Federal Register.
Therefore, NSF decided to retest two modules with lower challenge levels to provide a data set that meets
rule requirements. NSF also learned from EPA that the States could accept data from high feed challenge
tests, provided that feed concentrations were capped at 6.5 logio for the purpose of calculating the LRV.
Therefore, two sets of LRV calculations are presented here and in the full verification report, one set
using the measured feed counts, and a second set with the feed concentration set at 6.5 Iogi0.
The duration of each challenge test was approximately 35 minutes. The challenge organisms were
injected into the feed stream at start-up, after 15 minutes of operation, and after 30 minutes of operation.
After at least one minute of injection, grab samples were collected from the feed and filtrate sample taps.
After each round of sample collection, injection of the challenge organism suspension was turned off, and
clean feed water was pumped through the modules at 40 gpm until the next sampling point.
After the MS2 reduction data was shared with Dow, they requested that NSF conduct three more MS2
reduction challenges on one module at lower fluxes to identify whether MS2 reduction would increase as
the flux was lowered, and to generate a curve of MS2 reduction vs. flux. The procedure for these tests
was the same as for the previous tests. Module 5 was randomly chosen for testing by the laboratory
testing engineer. The tests were conducted at the target flows of 13.6 gpm, 25.4 gpm, and 35.6 gpm.
These flow rates translate into fluxes of 23.6, 44.1, and 61.8 gfd, respectively.
VERIFICATION OF PERFORMANCE
The feed and filtrate challenge organism triplicate counts were averaged by calculating geometric means.
Geometric means <1 were rounded up to 1, unless all three triplicate analyses had no organisms found.
The mean counts were then logio transformed to calculate log removal values (LRV).
The LT2ESWTR and MFGM specify that an LRV for the test (LRVc-TEsi) be calculated for each module
tested, and that the LRVs for each module are then combined to yield a single LRVC.TEST for the product.
If fewer than 20 modules are tested, as was the case for this verification, the LRVc-TEST is simply the
NSF 10/34/EPADWCTR The accompanying notice is an integral part of this verification statement. January 2011
VS-iii
-------
lowest LRV for the individual modules. However, the rule does not specify a method to calculate LRVC.
TEST for each module. Suggested options in the MFGM include:
• Calculate a LRV for each feed/filtrate sample pair, then calculate the average of the
individual sample point LRVs;
• Average all of the feed and filtrate counts, then calculate a single LRV for the module; or
• Calculate a LRV for each feed/filtrate sample pair, select the LRV for the module as the
lowest (most conservative of the three options).
Options 1 and 2 give LRVc-iEsi values that are either identical, or only a few hundredths or less different,
so for this verification, options 1 and 3 are used to calculate LRVs.
Each module was challenged with both B. atrophaeus and MS-2 on the same day. After all of the
modules were tested, the B. atrophaeus data was examined to choose the module to undergo the C.
parvum challenge test. Modules 2 and 3 were the only ones with B. atropheaus CPU found in all three
triplicate counts of a filtrate sample. For Module 2, 1 CPU was found in each of the triplicate
measurements for the 2-minute filtrate sample. For Module 3, the 30-minute filtrate sample triplicate
counts were 3, 1, and 1 CPU, so Module 3 was chosen over Module 2 for the C. parvum test. During the
C. parvum test, there was a possible integrity breach that developed, because the post-test pressure decay
rate was approximately double that measured immediately before the challenge test. When the filtrate
samples were analyzed, one C. parvum oocyst was found in one of the triplicate analyses for the 30-
minute filtrate sample. As a result, Dow decided to submit a sixth module for testing. This sixth module
was first challenged with B. atrophaeus to compare its performance to the other modules. The B.
atrophaeus data set was re-examined, omitting Module 3, and Module 2 was chosen for a second C.
parvum challenge test.
Except for the Module 3 post-C parvum challenge pressure decay rate, the maximum observed pressure
decay rate was 0.063 psig/min, indicating there were no other membrane integrity issues during testing.
C. parvum Reduction
The C. parvum feed concentrations ranged from 9.4xl05 to 2.4xl06 oocysts/L for the two tests. As
discussed above, because one oocyst was found in a filtrate sample for the Module 3 test and the post-test
pressure decay rate indicated a possible membrane breach, Module 2 was also tested for C. parvum
reduction. The C. parvum LRVs from the two different calculation methods are presented in Table VS-i.
All logio transformations of the filtrate samples are zero, so the LRVs are simply a function of the
measured feed concentrations. The LRVC.TEST from the overall means is 6.20, while the LRVC.TEST from
the individual sample pairs is 5.97. The flows recorded during the C. parvum challenges translate into
fluxes ranging from 69.7 to 70.0 gfd.
Table VS-i. C. parvum LRV Calculations
Module #
Module 3
Module 2
Mean LRV
6.20
6.26
Lowest LRV
5.97
6.18
B. atrophaeus Reduction
The B. atrophaeus feed concentrations for the tests ranged from 7.3xl06 to 1.63xl07 CFU/100 mL for the
first round of tests. As discussed above, because the challenge concentrations were above the allowable
maximum of 6.5 logio, two modules were retested with lower challenge concentrations. The feeds for the
retests ranged from 9.4xl05 to 1.29xl06 CFU/100 mL.
NSF 10/34/EPADWCTR
The accompanying notice is an integral part of this verification statement.
VS-iv
January 2011
-------
The B. atrophaeus LRVs are displayed in Table VS-ii. Where the feed concentrations are above 6.5 logio,
two LRVs are listed, one based on the measured feed concentration, and a second based on the feed
capped at 6.5 logio. Considering only the capped feed LRVs from the first round of tests, the LRVc-iEST
from the means is 6.40, and the LRVC_TEST from the individual sample pairs is 6.20. Including the lower
feed concentration retest data, the LRVC.TEST from the mean individual LRVs is 5.89, and 5.77 from the
individual sample pairs. The flows recorded during the B. atrophaeus tests translated into fluxes ranging
from 69.5 to 70.9 gfd.
Table VS-ii. B. atrophaeus LRV Calculations
Module #
Module 1
Module 2
Module 3
Module 4
Module 5
Module 6
Module 2 Retest
Module 4 Retest
LRV Using Measured Feeds
Mean LRV
7.05
7.10
7.05
6.87
7.12
7.18
5.98
5.89
Lowest LRV
7.04
7.08
7.00
6.70
7.09
7.11
5.97
5.77
LRV from Capped Feeds
Mean LRV
6.50
6.50
6.50
6.40
6.50
6.50
NA
NA
Lowest LRV
6.50
6.50
6.50
6.20
6.50
6.50
NA
NA
MS2 Reduction
The MS2 feed concentrations ranged from 7.6xl05 PFU/mL to 3.4xl06 PFU/mL for Modules 1 through 5,
while the feeds for the Module 6 test were just above IxlO7 PFU/mL. Therefore, the feed concentrations
for Module 6 were capped at 6.5 logio. The LRVs for the MS2 reduction tests are displayed in Table VS-
iii. The LRVC_TEST based on the mean LRVs is 2.54, and that based on the lowest individual sample pair
LRVs is 2.37. The flows recorded during the MS2 challenges translated into fluxes ranging from 69.5 to
71.9 gfd.
Table VS-iii. MS2 LRV Calculations
Module #
Module 1
Module 2
Module 3
Module 4
Module 5
Module 6
Mean LRV
4.52
3.75
3.48
3.34
3.24
2.54
Lowest LRV
4.47
3.60
3.37
3.08
2.99
2.37
MS2 Reduction vs. Flux
Dow requested that NSF conduct three additional MS2 challenge tests at lower flows to determine
whether MS2 reduction increased as the flux decreased. Module #5 was chosen for these tests because it
was the worst performing module of the five that had been tested.
The LRV calculations for these tests are displayed in Table VS-iv. The data indicates that MS2 reduction
is inversely proportional to the flux, but the observed LRVs for the lower flow rate tests are all within the
range of LRVs from the maximum flux tests, except for the first sampling point from the 13.6 gpm test.
The feed concentrations for these challenges are not capped at 6.5 logio because the intent of this study
was not to provide regulatory compliance data, but rather to supply comparative data on membrane
performance at lower fluxes.
NSF 10/34/EPADWCTR
The accompanying notice is an integral part of this verification statement.
VS-v
January 2011
-------
Table VS-iv. MS2 LRV at Lower Flows
Flow
13.6 gpm
25.4 gpm
35.6 gpm
Mean LRV
4.28
3.35
2.78
Lowest LRV
3.91
3.55
3.16
QUALITY ASSURANCE/QUALITY CONTROL (QA/QC)
NSF provided technical and quality assurance oversight of the verification testing as described in the
verification report, including a review of 100% of the data. NSF QA personnel also conducted a technical
systems audit during testing to ensure the testing was in compliance with the test plan. A complete
description of the QA/QC procedures is provided in the verification report.
Original signed by Sally Gutierrez 01/31/11
Sally Gutierrez Date
Director
National Risk Management Research
Laboratory
Office of Research and Development
United States Environmental Protection
Agency
Original signed by Robert Ferguson 01/13/11
Robert Ferguson Date
Vice President
Water Systems
NSF International
NOTICE: Verifications are based on an evaluation of technology performance under specific,
predetermined criteria and the appropriate quality assurance procedures. EPA and NSF make no
expressed or implied warranties as to the performance of the technology and do not certify that a
technology will always operate as verified. The end-user is solely responsible for complying with
any and all applicable federal, state, and local requirements. Mention of corporate names, trade
names, or commercial products does not constitute endorsement or recommendation for use of
specific products. This report is not an NSF Certification of the specific product mentioned
herein.
Availability of Supporting Documents
Copies of the test protocol, the verification statement, and the verification report (NSF
report # NSF 10/34/EPADWCTR) are available from the following sources:
1. ETV Drinking Water Systems Center Manager (order hard copy)
NSF International
P.O. Box 130140
Ann Arbor, Michigan 48113-0140
2. Electronic PDF copy
NSF web site: http://www.nsf.org/info/etv
EPA web site: http://www.epa.gov/etv
NSF 10/34/EPADWCTR
The accompanying notice is an integral part of this verification statement.
VS-vi
January 2011
------- |