ASTM D6908-06(2017)
(Practice)Standard Practice for Integrity Testing of Water Filtration Membrane Systems
Standard Practice for Integrity Testing of Water Filtration Membrane Systems
SIGNIFICANCE AND USE
4.1 The integrity test methods described are used to determine the integrity of membrane systems, and are applicable to systems containing membrane module configurations of both hollow fiber and flat sheet; such as, spiral-wound configuration. In all cases the practices apply to membranes in the RO, NF, and UF membrane classes. However, the TOC and Dye Test practices do not apply to membranes in the MF range or the upper end of the UF pore size range (0.01 μm and larger pore sizes) due to insignificant or inconsistent removal of TOC material by these membranes.
4.2 These methods may be used to identify relative changes in the integrity of a system, or used in conjunction with the equations described in 9.4, to provide a means of estimating the integrity in terms of log reduction value. For critical applications, estimated log reductions using these equations should be confirmed by experiment for the particular membrane and system configuration used.
4.3 The ability of the methods to detect any given defect is affected by the size of the system or portion of the system tested. Selecting smaller portions of the system to test will increase the sensitivity of the test to defects. When determining the size that can be tested as a discrete unit, use the guidelines supplied by the system manufacturer or the general guidelines provided in this practice.
4.4 The applicability of the tests is largely independent of system size when measured in terms of the impact of defects on the treated water quality (that is, the system LRV). This is because the bypass flow from any given defect is diluted in proportion to the systems total flowrate. For example, a 10-module system with a single defect will produce the same water quality as a 100-module system with ten of the same size defects.
SCOPE
1.1 This practice covers the determination of the integrity of water filtration membrane elements and systems using air based tests (pressure decay and vacuum hold), soluble dye, continuous monitoring particulate light scatter techniques, and TOC monitoring tests for the purpose of rejecting particles and microbes. The tests are applicable to systems with membranes that have a nominal pore size less than about 1 µm. The TOC, and Dye, tests are generally applicable to NF and RO class membranes only.
1.2 This practice does not purport to cover all available methods of integrity testing.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D6908 − 06 (Reapproved 2017)
Standard Practice for
Integrity Testing of Water Filtration Membrane Systems
This standard is issued under the fixed designation D6908; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope D3864Guide for On-Line Monitoring Systems for Water
Analysis
1.1 Thispracticecoversthedeterminationoftheintegrityof
D3923Practices for Detecting Leaks in Reverse Osmosis
water filtration membrane elements and systems using air
and Nanofiltration Devices
based tests (pressure decay and vacuum hold), soluble dye,
D4839TestMethodforTotalCarbonandOrganicCarbonin
continuous monitoring particulate light scatter techniques, and
WaterbyUltraviolet,orPersulfateOxidation,orBoth,and
TOCmonitoringtestsforthepurposeofrejectingparticlesand
Infrared Detection
microbes. The tests are applicable to systems with membranes
D5173Guide for On-Line Monitoring of Total Organic
that have a nominal pore size less than about 1 µm. The TOC,
Carbon inWater by Oxidation and Detection of Resulting
and Dye, tests are generally applicable to NF and RO class
Carbon Dioxide
membranes only.
D5904TestMethodforTotalCarbon,InorganicCarbon,and
1.2 This practice does not purport to cover all available
Organic Carbon in Water by Ultraviolet, Persulfate
methods of integrity testing.
Oxidation, and Membrane Conductivity Detection
D5997 Test Method for On-Line Monitoring of Total
1.3 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this Carbon,InorganicCarboninWaterbyUltraviolet,Persul-
fate Oxidation, and Membrane Conductivity Detection
standard.
D6161TerminologyUsedforMicrofiltration,Ultrafiltration,
1.4 This standard does not purport to address all of the
Nanofiltration and Reverse Osmosis Membrane Processes
safety concerns, if any, associated with its use. It is the
D6698Test Method for On-Line Measurement of Turbidity
responsibility of the user of this standard to establish appro-
Below 5 NTU in Water
priate safety, health, and environmental practices and deter-
E20Practice for Particle Size Analysis of Particulate Sub-
mine the applicability of regulatory limitations prior to use.
stances in the Range of 0.2 to 75 Micrometres by Optical
1.5 This international standard was developed in accor-
Microscopy (Withdrawn 1994)
dance with internationally recognized principles on standard-
E128Test Method for Maximum Pore Diameter and Perme-
ization established in the Decision on Principles for the
ability of Rigid Porous Filters for Laboratory Use
Development of International Standards, Guides and Recom-
F658Practice for Calibration of a Liquid-Borne Particle
mendations issued by the World Trade Organization Technical
Counter Using an Optical System Based Upon Light
Barriers to Trade (TBT) Committee.
Extinction (Withdrawn 2007)
2. Referenced Documents
3. Terminology
2.1 ASTM Standards:
3.1 Definitions:
D1129Terminology Relating to Water
3.1.1 For definitions of terms used in this standard, refer to
D2777Practice for Determination of Precision and Bias of
Terminologies D6161 and D1129.
Applicable Test Methods of Committee D19 on Water
3.1.2 For description of terms relating to cross flow mem-
D3370Practices for Sampling Water from Closed Conduits
brane systems, refer to Terminology D6161.
3.1.3 For definition of terms relating to dissolved carbon
1 and carbon analyzers, refer to Guide D5173 and Test Methods
This practice is under the jurisdiction ofASTM Committee D19 on Water and
is the direct responsibility of Subcommittee D19.08 on Membranes and Ion
D5904 and D5997.
Exchange Materials.
3.2 Definitions of Terms Specific to This Standard:
Current edition approved Dec. 1, 2017. Published December 2017. Originally
3.2.1 bubble point, n—when the pores of a membrane are
approved in 2003. Last previous edition approved in 2010 as D6908–06 (2010).
filled with liquid and air pressure is applied to one side of the
DOI: 10.1520/D6908-06R17.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on The last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6908 − 06 (2017)
membrane, surface tension prevents the liquid in the pores 4. Significance and Use
from being blown out by air pressure below a minimum
4.1 The integrity test methods described are used to deter-
pressure known as the bubble point.
mine the integrity of membrane systems, and are applicable to
systems containing membrane module configurations of both
3.2.2 equivalent diameter, n—the diameter of a pore or
hollowfiberandflatsheet;suchas,spiral-woundconfiguration.
defect calculated from its bubble point using Eq 1 (see 9.3).
In all cases the practices apply to membranes in the RO, NF,
This is not necessarily the same as the physical dimensions of
and UF membrane classes. However, the TOC and Dye Test
the defect(s).
practices do not apply to membranes in the MF range or the
3.2.3 integrity, n—measure of the degree to which a mem-
upper end of the UF pore size range (0.01 µm and larger pore
brane system rejects particles of interest. Usually expressed as
sizes) due to insignificant or inconsistent removal of TOC
a log reduction value (LRV).
material by these membranes.
3.2.4 log reduction value (LRV), n—a measure of the
4.2 These methods may be used to identify relative changes
particle removal efficiency of the membrane system expressed in the integrity of a system, or used in conjunction with the
equationsdescribedin9.4,toprovideameansofestimatingthe
as the log of the ratio of the particle concentration in the
integrity in terms of log reduction value. For critical
untreatedandtreatedfluid.Forexample,a10-foldreductionin
applications, estimated log reductions using these equations
particle concentration is an LRV of 1. The definition of LRV
should be confirmed by experiment for the particular mem-
within this practice is one of many definitions that are used
brane and system configuration used.
withintheindustry.Theuserofthispracticeshouldusecareas
not to interchange this definition with other definitions that
4.3 The ability of the methods to detect any given defect is
potentially exist. The U.S. EPA applies the LRV definition to
affected by the size of the system or portion of the system
pathogens only.
tested. Selecting smaller portions of the system to test will
increasethesensitivityofthetesttodefects.Whendetermining
3.2.5 membrane system, n—refers to the membrane hard-
the size that can be tested as a discrete unit, use the guidelines
ware installation including the membrane, membrane
supplied by the system manufacturer or the general guidelines
housings, interconnecting plumbing, seals and valves. The
provided in this practice.
membrane can be any membrane with a pore size less than
4.4 The applicability of the tests is largely independent of
about 1 µm.
systemsizewhenmeasuredintermsoftheimpactofdefectson
3.2.6 multiplexing, v—the sharing of a common set of
the treated water quality (that is, the system LRV). This is
physical, optical, and/or electrical components across multiple
because the bypass flow from any given defect is diluted in
system sample points. Two approaches of multiplexing are
proportion to the systems total flowrate. For example, a
considered in this practice: sensor multiplexing and liquid
10-module system with a single defect will produce the same
multiplexing. Sensor multiplexing monitors a unique sample
waterqualityasa100-modulesystemwithtenofthesamesize
with a dedicated sensor. Sensors are linked to a centralized
defects.
location, where data processing and the determinative mea-
surement is performed. Liquid multiplexing uses a common 5. Reagents and Materials
instrument to measure multiple process sample streams in a
5.1 Reagents—As specified for the TOC analyzer in ques-
sequential manor. Samples are fed to the common analyzer via
tion. Guide D5173 lists requirements for a variety of instru-
a system of a manifold, valves, and tubing.
ments.
3.2.7 relative standard deviation (RSD), n—a generic con-
5.2 SolubleDyeSolution—UseFD&Correagentgradedyes
tinuous monitoring parameter used to quantify the fluctuation
such as FD&C Red #40, dissolved in RO permeate, or in
of the particulate light scatter baseline from a laser-based
ASTM Reagent Grade Type IV water.
incident light source. As an example, the RSD may be
5.3 Light Scatter Standards—See Test Method D6698 for
calculated as the standard deviation divided by the average for
the selection of appropriate turbidity standards. In addition,
a defined set of measurements that are acquired over a short
polystyrene latex standards of a defined size and concentration
period of time. The result is multiplied by 100 to express the
may be used in place of a turbidity standard as long as count
value as a percentage and is then reported as %RSD. The
concentration is correlated to instrument response.
sample monitoring frequency is typically in the range of 0.1 to
5.4 Light Obscuration Standards—Standards that are used
60 seconds. The RSD parameter is specific for laser-based
for the calibration of particle counters, namely polystyrene
particulate light-scatter techniques which includes particle
latex spheres should be used. Consult the instrument manufac-
counters and laser turbidimeters. The RSD is can be treated as
turer for the appropriate type and size diameter of standards to
an independent monitoring parameter. Other methods for RSD
be used.
calculations may also be used.
6. Precision and Bias
3.2.8 UCL, n—a generic term to represent the aggregate
quantity of material that causes an incident light beam to be 6.1 Neitherprecisionnorbiasdatacanbeobtainedforthese
scattered. The value can be correlated to either turbidity or to
test methods because they are composed of continuous deter-
specific particle count levels of a defined size. minations specific to the equipment being tested. No suitable
D6908 − 06 (2017)
NOTE 1—The last example also represents the vacuum decay test when a partial vacuum is applied to one side of the membrane.
FIG. 1 Various Configurations for the Pressure Decay Test
means has been found of performing a collaborative study to of a membrane system (either the feed or filtrate side) is
meet the requirements of Practice D2777. The inability to isolated and pressurized with air. In the VDT an air pressure
obtain precision and bias data for methods involving continu- differential is generated by isolating one side of a wet mem-
ous sampling or measurement of specific properties is recog- braneandapplyingapartialvacuumwithatmosphericpressure
nized and stated in the scope of Practice D2777. on the other side. Air flow is measured as the rate of vacuum
decayontheisolatedsideofthemembrane.Theresultsofboth
the PDT and VDT are a direct measure of the membrane
PRACTICE A
system integrity.
PRESSURE DECAY AND VACUUM DECAY TESTS
8.2 Limitations and Applications—The tests are limited to
7. Scope
monitoring and control of defects greater than about 1 to 2 µm
(see 9.3, Selection of Test Pressure).
7.1 This practice covers the determination of integrity for
8.2.1 The tests can be applied in various forms provided a
membrane systems using the pressure decay test (PDT) and
differential pressure below the bubble point is established
vacuum decay test (VDT).
across a wet membrane with air on the relative high pressure
7.2 The tests may be used on membranes in all classes, RO
side of the membrane. Some examples are included in Fig. 1.
through MF, and are suitable for hollow fibers, tubular and flat
8.2.2 Both the PDT and VDT are described here in their
sheet(suchasspiralwound)configurations.However,thePDT
most common forms. In the case of the PDT this is with one
is most commonly employed for in-situ testing of UF and MF
side of the membrane pressurized with air and the other filled
systems and the VDT for testing NF and RO elements and
withliquidventedtoatmosphere.InthecaseoftheVDT,airis
systems. See Practices D3923.
typically present on both sides and vacuum is applied to the
permeate side.
8. Summary of Practice
8.1 Principles—The tests work on the principle that if air
9. Procedure
pressure is applied to one side of an integral, fully wet
9.1 Pressure Decay Test (PDT)—The pressure decay test
membrane at a pressure below the membrane bubble point,
can be carried out by pressurizing either side of the membrane
there will be no airflow through the membrane other than by
(see Fig. 1). For complete wet-out of all the membrane in the
diffusion through liquid in the membrane wall. If a defect or
system, the system should be operated at its normal pressure
leak is present then air will flow freely at this point, providing
beforethetestisperformed.ThestepsinvolvedinthePDTare:
that the size of the defect is such that it has a bubble point
9.1.1 Drain the liquid from the side of the membrane to be
pressurebelowtheappliedtestpressure.Theconfigurationsfor
pressurized (referred to here as the upstream side).
applying air and water are shown in Fig. 1.
9.1.2 Openthedownstreamsideofthemembranesystemto
8.1.1 Airbasedtestsaremeansofapplyingair,atapressure
atmosphere. This ensures air that leaks or diffuses is free to
below the membrane bubble point, to one side of a wet
escape without creating backpressure, and establishes the
membrane and measuring the air flow from one side to the
downstream pressure as atmospheric pressure.
other.Air flow can be measured directly, but more commonly,
it is derived from pressure or vacuum decay. In the PDT air 9.1.3 Isolateandpressurizetheupstreamsidewithairtothe
flow is measured as the rate of pressure decay when one side testpressure.Thenisolatetheairsupply.Donotexceedthetest
D6908 − 06 (2017)
FIG. 2 Connection Arrangement for the VDT
pressure as this could lead to blowing out smaller pores than nent can be estimated either by calculation or experimental
intended resulting in a higher PDT. Record this pressure as determination of the diffusive flow, such as laboratory mea-
P , the maximum test pressure
...
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