ASTM D6908-06(2010)
(Practice)Standard Practice for Integrity Testing of Water Filtration Membrane Systems
Standard Practice for Integrity Testing of Water Filtration Membrane Systems
SIGNIFICANCE AND USE
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.
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.
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 standard.
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 and health practices and determine the applicability of regulatory limitations prior to use.
7.1 This practice covers the determination of integrity for membrane systems using the pressure decay test (PDT) and vacuum decay test (VDT).
7.2 The tests may be used on membranes in all classes, RO through MF, and are suitable for hollow fibers, tubular and flat sheet (such as spiral wound) configurations. However, the PDT is most commonly employed for in-situ testing of UF and MF systems and the VDT for testing NF and RO elements and systems. See Practice D3923.
10.1 This practice is applicable where the membrane system and water source will allow the monitoring of TOC both upstream and downstream of the system, and at least order of magnitude difference from the feed can be measured in the permeate (product) water. See D4839.
16.1 This guide is applicable to RO and NF membrane systems, including those with spiral, tubular or flat sheet configuration elements. The guide describes the application of two soluble dyes, Red Dye # 40 and Rhodamine WT. Both dyes have a molecular weight of approximately 500. See Practice D3923.
22.1 This guide is applicable to MF, UF, NF, and RO membrane systems, including those with spiral, t...
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D6908 − 06 (Reapproved 2010)
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 D5173Guide for On-Line Monitoring of Total Organic
Carbon inWater by Oxidation and Detection of Resulting
1.1 Thispracticecoversthedeterminationoftheintegrityof
Carbon Dioxide
water filtration membrane elements and systems using air
D5904TestMethodforTotalCarbon,InorganicCarbon,and
based tests (pressure decay and vacuum hold), soluble dye,
Organic Carbon in Water by Ultraviolet, Persulfate
continuous monitoring particulate light scatter techniques, and
Oxidation, and Membrane Conductivity Detection
TOCmonitoringtestsforthepurposeofrejectingparticlesand
D5997 Test Method for On-Line Monitoring of Total
microbes. The tests are applicable to systems with membranes
Carbon,InorganicCarboninWaterbyUltraviolet,Persul-
that have a nominal pore size less than about 1 µm. The TOC,
fate Oxidation, and Membrane Conductivity Detection
and Dye, tests are generally applicable to NF and RO class
D6161TerminologyUsedforMicrofiltration,Ultrafiltration,
membranes only.
Nanofiltration and Reverse Osmosis Membrane Processes
1.2 This practice does not purport to cover all available
D6698Test Method for On-Line Measurement of Turbidity
methods of integrity testing.
Below 5 NTU in Water
E20Practice for Particle Size Analysis of Particulate Sub-
1.3 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this stances in the Range of 0.2 to 75 Micrometres by Optical
Microscopy (Withdrawn 1994)
standard.
E128Test Method for Maximum Pore Diameter and Perme-
1.4 This standard does not purport to address all of the
ability of Rigid Porous Filters for Laboratory Use
safety concerns, if any, associated with its use. It is the
F658Practice for Calibration of a Liquid-Borne Particle
responsibility of the user of this standard to establish appro-
Counter Using an Optical System Based Upon Light
priate safety and health practices and determine the applica-
Extinction (Withdrawn 2007)
bility of regulatory limitations prior to use.
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 practice, 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.
D3864Guide for On-Line Monitoring Systems for Water
3.1.3 For definition of terms relating to dissolved carbon
Analysis
and carbon analyzers, refer to D5173, D5904 and D5997.
D3923Practices for Detecting Leaks in Reverse Osmosis
3.1.4 bubble point—when the pores of a membrane are
and Nanofiltration Devices
filled with liquid and air pressure is applied to one side of the
D4839TestMethodforTotalCarbonandOrganicCarbonin
membrane, surface tension prevents the liquid in the pores
WaterbyUltraviolet,orPersulfateOxidation,orBoth,and
from being blown out by air pressure below a minimum
Infrared Detection
pressure known as the bubble point.
3.1.5 equivalent diameter—the diameter of a pore or defect
This practice is under the jurisdiction ofASTM Committee D19 on Water and
is the direct responsibility of Subcommittee D19.08 on Membranes and Ion
calculated from its bubble point using Eq 1 (see 9.3). This is
Exchange Materials.
not necessarily the same as the physical dimensions of the
Current edition approved May 1, 2010. Published May 2010. Originally
defect(s).
approved in 2003. Last previous edition approved in 2006 as D6908–06. DOI:
10.1520/D6908-06R10.
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 (2010)
3.1.6 integrity—measure of the degree to which a mem- practices do not apply to membranes in the MF range or the
brane system rejects particles of interest. Usually expressed as upper end of the UF pore size range (0.01 µm and larger pore
a log reduction value (LRV). sizes) due to insignificant or inconsistent removal of TOC
material by these membranes.
3.1.7 log reduction value (LRV)—a measure of the particle
removal efficiency of the membrane system expressed as the
4.2 These methods may be used to identify relative changes
log of the ratio of the particle concentration in the untreated
in the integrity of a system, or used in conjunction with the
and treated fluid. For example, a 10-fold reduction in particle
equationsdescribedin9.4,toprovideameansofestimatingthe
concentrationisanLRVof1.ThedefinitionofLRVwithinthis
integrity in terms of log reduction value. For critical
Standard is one of many definitions that are used within the
applications, estimated log reductions using these equations
industry. The user of this standard should use care as not to
should be confirmed by experiment for the particular mem-
interchange this definition with other definitions that poten-
brane and system configuration used.
tially exist. The USEPA applies the LRV definition to patho-
4.3 The ability of the methods to detect any given defect is
gens only.
affected by the size of the system or portion of the system
3.1.8 membrane system—refers to the membrane hardware
tested. Selecting smaller portions of the system to test will
installation including the membrane, membrane housings,
increasethesensitivityofthetesttodefects.Whendetermining
interconnectingplumbing,sealsandvalves.Themembranecan
the size that can be tested as a discrete unit, use the guidelines
be any membrane with a pore size less than about 1 µm.
supplied by the system manufacturer or the general guidelines
provided in this standard.
3.1.9 multiplexing—the sharing of a common set of
physical, optical, and/or electrical components across multiple
4.4 The applicability of the tests is largely independent of
system sample points. Two approaches of multiplexing are
systemsizewhenmeasuredintermsoftheimpactofdefectson
considered in this practice: sensor multiplexing and liquid
the treated water quality (that is, the system LRV). This is
multiplexing. Sensor multiplexing monitors a unique sample
because the bypass flow from any given defect is diluted in
with a dedicated sensor. Sensors are linked to a centralized
proportion to the systems total flowrate. For example, a
location, where data processing and the determinative mea-
10-module system with a single defect will produce the same
surement is performed. Liquid multiplexing uses a common
waterqualityasa100-modulesystemwithtenofthesamesize
instrument to measure multiple process sample streams in a
defects.
sequential manor. Samples are fed to the common analyzer via
a system of a manifold, valves and tubing.
5. Reagents and Materials
3.1.10 relative standard deviation (RSD)—a generic con-
5.1 Reagents—As specified for the TOC analyzer in ques-
tinuous monitoring parameter used to quantify the fluctuation
tion. D5173 lists requirements for a variety of instruments.
of the particulate light scatter baseline from a laser-based
5.2 SolubleDyeSolution—UseFD&Correagentgradedyes
incident light source. As an example, the RSD may be
such as FD&C Red #40, dissolved in RO permeate, or in
calculated as the standard deviation divided by the average for
ASTM Reagent Grade Type IV water.
a defined set of measurements that are acquired over a short
5.3 Light Scatter Standards—See Test Method D6698 for
period of time. The result is multiplied by 100 to express the
the selection of appropriate turbidity standards. In addition,
value as a percentage and is then reported as %RSD. The
polystyrene latex standards of a defined size and concentration
sample monitoring frequency is typically in the range of 0.1 to
may be used in place of a turbidity standard as long as count
60 seconds. The RSD parameter is specific for laser-based
concentration is correlated to instrument response.
particulate light-scatter techniques which includes particle
counters and laser turbidimeters. The RSD is can be treated as
5.4 Light Obscuration Standards—Standards that are used
an independent monitoring parameter. Other methods for RSD
for the calibration of particle counters, namely polystyrene
calculations may also be used.
latex spheres should be used. Consult the instrument manufac-
turer for the appropriate type and size diameter of standards to
3.1.11 UCL—a generic term to represent the aggregate
be used.
quantity of material that causes an incident light beam to be
scattered. The value can be correlated to either turbidity or to
6. Precision and Bias
specific particle count levels of a defined size.
6.1 Neitherprecisionnorbiasdatacanbeobtainedforthese
4. Significance and Use
test methods because they are composed of continuous deter-
4.1 The integrity test methods described are used to deter- minations specific to the equipment being tested. No suitable
mine the integrity of membrane systems, and are applicable to means has been found of performing a collaborative study to
systems containing membrane module configurations of both meet the requirements of Practice D2777. The inability to
hollowfiberandflatsheet;suchas,spiral-woundconfiguration. obtain precision and bias data for methods involving continu-
In all cases the practices apply to membranes in the RO, NF, ous sampling or measurement of specific properties is recog-
and UF membrane classes. However, the TOC and Dye Test nized and stated in the scope of Practice D2777.
D6908 − 06 (2010)
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
PRACTICE A—PRESSURE DECAY AND VACUUM decayontheisolatedsideofthemembrane.Theresultsofboth
DECAY TESTS the PDT and VDT are a direct measure of the membrane
system integrity.
7. Scope
8.2 Limitations and Applications—The tests are limited to
7.1 This practice covers the determination of integrity for
monitoring and control of defects greater than about 1 to 2 µm
membrane systems using the pressure decay test (PDT) and
(see 9.3, Selection of Test Pressure).
vacuum decay test (VDT).
8.2.1 The tests can be applied in various forms provided a
7.2 The tests may be used on membranes in all classes, RO differential pressure below the bubble point is established
through MF, and are suitable for hollow fibers, tubular and flat
across a wet membrane with air on the relative high pressure
sheet(suchasspiralwound)configurations.However,thePDT side of the membrane. Some examples are included in Fig. 1.
is most commonly employed for in-situ testing of UF and MF
8.2.2 Both the PDT and VDT are described here in their
systems and the VDT for testing NF and RO elements and
most common forms. In the case of the PDT this is with one
systems. See Practice D3923.
side of the membrane pressurized with air and the other filled
withliquidventedtoatmosphere.InthecaseoftheVDT,airis
8. Summary of Practice
typically present on both sides and vacuum is applied to the
permeate side.
8.1 Principles—The tests work on the principle that if air
pressure is applied to one side of an integral, fully wet
membrane at a pressure below the membrane bubble point, 9. Procedure
there will be no airflow through the membrane other than by
9.1 Pressure Decay Test (PDT)—The pressure decay test
diffusion through liquid in the membrane wall. If a defect or
can be carried out by pressurizing either side of the membrane
leak is present then air will flow freely at this point, providing
(see Fig. 1). For complete wet-out of all the membrane in the
that the size of the defect is such that it has a bubble point
system, the system should be operated at its normal pressure
pressurebelowtheappliedtestpressure.Theconfigurationsfor
beforethetestisperformed.ThestepsinvolvedinthePDTare:
applying air and water are shown in Fig. 1.
9.1.1 Drain the liquid from the side of the membrane to be
8.1.1 Airbasedtestsaremeansofapplyingair,atapressure
pressurized (referred to here as the upstream side).
below the membrane bubble point, to one side of a wet
9.1.2 Openthedownstreamsideofthemembranesystemto
membrane and measuring the air flow from one side to the
atmosphere. This ensures air that leaks or diffuses is free to
other.Air flow can be measured directly, but more commonly,
escape without creating backpressure, and establishes the
it is derived from pressure or vacuum decay. In the PDT air
downstream pressure as atmospheric pressure.
flow is measured as the rate of pressure decay when one side
of a membrane system (either the feed or filtrate side) is 9.1.3 Isolateandpressurizetheupstreamsidewithairtothe
isolated and pressurized with air. In the VDT an air pressure testpressure.Thenisolatetheairsupply.Donotexceedthetest
differential is generated by isolating one side of a wet mem- pressure as this could lead to blowing out smaller pores than
braneandapplyingapartialvacuumwithatmosphericpressure intended resulting in a higher PDT. Record this pressure as
on the other side. Air flow is measured as the rate of vacuum P , the maximum test pressure.
test,max
D6908 − 06 (2010)
FIG. 2 Connection Arrangement for the VDT
9.1.4 After allowing time for the decay rate to stabilize suitably integral by other means. In such cases, the measured
record the initial pressure, P, and commence timer. PDR result is corrected as follows:
i
9.1.5 After at least 2 min, record the final pressure, P, and
f
PDR 5 PDR 2 PDR
corrected measured diffusion
the time taken for the pressure to decay from P to P (t). The
i f
where:
time period can be extended in order obtain a more accurate
PDR = PDR for the integral system, at the
result if the pressure decay rate is slow.
diffusion measured
9.1.6 Calculate the Pressure Decay Rate (PDR) as follows same P and temperature.
Test
and record the result along with the test conditions
9.1.8 For most practical appl
...
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