ASTM D6908-03

Standard Practice for Integrity Testing of Water Filtration Membrane Systems

SCOPE
1.1 This standard covers the determination of the integrity of water filtration membrane elements and systems using air based tests (pressure decay and vacuum hold), soluble dye, 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 m. The TOC and Dye tests are generally applicable to NF and RO class membranes only.
1.2 This standard does not purport to cover all available methods of integrity testing.
1.3 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.

General Information

• Status: Historical
• Publication Date: 09-Apr-2003
• ICS: 13.060.01 - Water quality in general
• Technical Committee: D19 - Water
• Drafting Committee: D19.08 - Membranes and Ion Exchange Materials

Relations

• Replaced By: ASTM D6908-05 - Standard Practice for Integrity Testing of Water Filtration Membrane Systems
• Effective Date: 01-Oct-2005
• Referred By: ASTM D7601-19 - Standard Practice for Pressure Driven Membrane Separation Element/Bundle Evaluation
• Effective Date: 10-Apr-2003
• Referred By: ASTM D3923-23 - Standard Practices for Detecting Leaks in Reverse Osmosis and Nanofiltration Devices
• Effective Date: 10-Apr-2003
• Referred By: ASTM D7285-06(2017) - Standard Guide for Recordkeeping Microfiltration and Ultrafiltration Systems
• Effective Date: 10-Apr-2003

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
An American National Standard
Designation: D 6908 – 03
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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope Membrane Conductivity Detection
D6161 Terminology Used for Crossflow Microfiltration,
1.1 This standard covers the determination of the integrity
Ultrafiltration, Nanofiltration and Reverse Osmosis Mem-
of water filtration membrane elements and systems using air
brane Processes
basedtests(pressuredecayandvacuumhold),solubledye,and
E128 Maximum Pore Diameter and Permeability of Rigid
TOCmonitoringtestsforthepurposeofrejectingparticlesand
Porous Filters for Laboratory Use
microbes. The tests are applicable to systems with membranes
that have a nominal pore size less than about 1 µm. The TOC
3. Terminology
and Dye tests are generally applicable to NF and RO class
3.1 Definitions—For definitions of terms used in this prac-
membranes only.
tice, refer to Terminologies D6161 and D1129.
1.2 This standard does not purport to cover all available
3.1.1 For description of terms relating to cross flow mem-
methods of integrity testing.
brane systems, refer to Terminology D6161.
1.3 This standard does not purport to address all of the
3.1.2 For definition of terms relating to dissolved carbon
safety concerns, if any, associated with its use. It is the
and carbon analyzers, refer to D5173, D5904 and D5997.
responsibility of the user of this standard to establish appro-
3.1.3 bubble point—when the pores of a membrane are
priate safety and health practices and determine the applica-
filled with liquid and air pressure is applied to one side of the
bility of regulatory limitations prior to use.
membrane, surface tension prevents the liquid in the pores
2. Referenced Documents from being blown out by air pressure below a minimum
pressure known as the bubble point.
2.1 ASTM Standards:
3.1.4 equivalent diameter—the diameter of a pore or defect
D1129 Terminology Relating to Water
calculated from its bubble point using Eq 1 (see 9.3). This is
D2777 Determination of Precision and Bias of Applicable
not necessarily the same as the physical dimensions of the
Tests Methods of Committee D19 on Water
defect(s).
D3370 Practices for Sampling Water from Closed Con-
2 3.1.5 integrity—measure of the degree to which a mem-
duits
brane system rejects particles of interest. Usually expressed as
D3923 Practice for the Determination of Leaks Within a
3 a log reduction value (LRV).
Reverse Osmosis Device
3.1.6 log reduction value (LRV)—a measure of the particle
D4839 Total Carbon and Organic Carbon in Water by
removal efficiency of the membrane system expressed as the
Ultraviolet, or Persulfate Oxidation, or Both, and Infrared
log of the ratio of the particle concentration in the untreated
Detection
and treated fluid. For example, a 10-fold reduction in particle
D5173 On-Line Monitoring of Carbon Compounds in Wa-
concentration is an LRV of 1.
ter by Chemical Oxidation, by UV Light Oxidation, by
3.1.7 membrane system—refers to the membrane hardware
Both, or by High Temperature Combustion Followed by
installation including the membrane, membrane housings,
Gas Phase NDIR or by Electrolytic Conductivity
interconnectingplumbing,sealsandvalves.Themembranecan
D5904 Total Carbon, Inorganic Carbon and Organic Car-
be any membrane with a pore size less than about 1 µm.
bon in Water by Ultraviolet, Persulfate Oxidation and
Membrane Conductivity Detection
4. Significance and Use
D5997 On-Line Monitoring of Total Carbon, Inorganic
4.1 The integrity test methods described are used to deter-
Carbon in Water by Ultraviolet, Persulfate Oxidation, and
mine the integrity of membrane systems, and are applicable to
systems containing membrane module configurations of both
hollowfiberandflatsheet;suchas,spiral-woundconfiguration.
This practice is under the jurisdiction ofASTM Committee D19 on Water and
is the direct responsibility of Subcommittee D19.08 on Membranes and Ion
In all cases the practices apply to membranes in the RO, NF,
Exchange Materials.
Current edition approved April 10, 2003. Published June 2003.
Annual Book of ASTM Standards, Vol 11.01.
3 4
Annual Book of ASTM Standards, Vol 11.02. Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6908–03
and UF membrane classes. However, the TOC and Dye Test because the bypass flow from any given defect is diluted in
practices do not apply to membranes in the MF range or the proportion to the systems total flowrate. For example, a
upper end of the UF pore size range (0.01 µm and larger pore 10-module system with a single defect will produce the same
sizes) due to insignificant or inconsistent removal of TOC waterqualityasa100-modulesystemwithtenofthesamesize
material by these membranes. defects.
4.2 These methods may be used to identify relative changes
5. Reagents and Materials
in the integrity of a system, or used in conjunction with the
equationsdescribedin9.4,toprovideameansofestimatingthe 5.1 Reagents—As specified for the TOC analyzer in ques-
integrity in terms of log reduction value. For critical applica- tion. D5173 lists requirements for a variety of instruments.
tions,estimatedlogreductionsusingtheseequationsshouldbe 5.2 Soluble Dye Solution—Use FD&C or reagent grade
confirmed by experiment for the particular membrane and dyes such as FD&C Red #40, dissolved in RO permeate, or in
system configuration used. ASTM Reagent Grade Type IV water.
4.3 The ability of the methods to detect any given defect is
6. Precision and Bias
affected by the size of the system or portion of the system
tested. Selecting smaller portions of the system to test will 6.1 Neitherprecisionnorbiasdatacanbeobtainedforthese
increasethesensitivityofthetesttodefects.Whendetermining test methods because they are composed of continuous deter-
the size that can be tested as a discrete unit, use the guidelines minations specific to the equipment being tested. No suitable
supplied by the system manufacturer or the general guidelines means has been found of performing a collaborative study to
provided in this standard. meet the requirements of Practice D2777. The inability to
4.4 The applicability of the tests is largely independent of obtain precision and bias data for methods involving continu-
systemsizewhenmeasuredintermsoftheimpactofdefectson ous sampling or measurement of specific properties is recog-
the treated water quality (that is, the system LRV). This is nized and stated in the scope of Practice D2777.
PRACTICE A—PRESSURE DECAYAND VACUUM DECAY TESTS
7. Scope decayontheisolatedsideofthemembrane.Theresultsofboth
the PDT and VDT are a direct measure of the membrane
7.1 This practice covers the determination of integrity for
system integrity.
membrane systems using the pressure decay test (PDT) and
8.2 Limitations and Applications—The tests are limited to
vacuum decay test (VDT).
monitoring and control of defects greater than about 1 to 2 µm
7.2 The tests may be used on membranes in all classes, RO
(see 9.3, Selection of Test Pressure).
through MF, and are suitable for hollow fibers, tubular and flat
8.2.1 The tests can be applied in various forms provided a
sheet(suchasspiralwound)configurations.However,thePDT
differential pressure below the bubble point is established
is most commonly employed for in-situ testing of UF and MF
across a wet membrane with air on the relative high pressure
systems and the VDT for testing NF and RO elements and
side of the membrane. Some examples are included in Fig. 1.
systems. See Practice D3923.
8.2.2 Both the PDT and VDT are described here in their
most common forms. In the case of the PDT this is with one
8. Summary of Practice
side of the membrane pressurized with air and the other filled
withliquidventedtoatmosphere.InthecaseoftheVDT,airis
8.1 Principles—The tests work on the principle that if air
typically present on both sides and vacuum is applied to the
pressure is applied to one side of an integral, fully wet
permeate side.
membrane at a pressure below the membrane bubble point,
there will be no airflow through the membrane other than by
9. Procedure
diffusion through liquid in the membrane wall. If a defect or
leak is present then air will flow freely at this point, providing
9.1 Pressure Decay Test (PDT)—The pressure decay test
that the size of the defect is such that it has a bubble point
can be carried out by pressurizing either side of the membrane
pressure below the applied test pressure.
(see Fig. 1). For complete wet-out of all the membrane in the
8.1.1 Airbasedtestsaremeansofapplyingair,atapressure system, the system should be operated at its normal pressure
below the membrane bubble point, to one side of a wet beforethetestisperformed.ThestepsinvolvedinthePDTare:
membrane and measuring the air flow from one side to the 9.1.1 Drain the liquid from the side of the membrane to be
other.Air flow can be measured directly, but more commonly, pressurized (referred to here as the upstream side).
it is derived from pressure or vacuum decay. In the PDT air 9.1.2 Openthedownstreamsideofthemembranesystemto
flow is measured as the rate of pressure decay when one side atmosphere. This ensures air that leaks or diffuses is free to
of a membrane system (either the feed or filtrate side) is escape without creating backpressure, and establishes the
isolated and pressurized with air. In the VDT an air pressure downstream pressure as atmospheric pressure.
differential is generated by isolating one side of a wet mem- 9.1.3 Isolateandpressurizetheupstreamsidewithairtothe
braneandapplyingapartialvacuumwithatmosphericpressure testpressure.Thenisolatetheairsupply.Donotexceedthetest
on the other side. Air flow is measured as the rate of vacuum pressure as this could lead to blowing out smaller pores than
D6908–03
NOTE—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
intended resulting in a higher PDT. Record this pressure as diffusive flow from the measured flow. The diffusive compo-
P , the maximum test pressure. nent can be estimated either by calculation or experimental
test,max
9.1.4 After allowing time for the decay rate to stabilize
determination of the diffusive flow, such as laboratory mea-
record the initial pressure, P, and commence timer. surements or by measuring the PDR on a system confirmed
i
9.1.5 After at least 2 min, record the final pressure, P, and
suitably integral by other means. In such cases, the measured
f
the time taken for the pressure to decay from P to P (t). The
PDR result is corrected as follows:
i f
time period can be extended in order obtain a more accurate
PDR 5 PDR 2 PDR
corrected measured diffusion
result if the pressure decay rate is slow.
9.1.6 Calculate the Pressure Decay Rate (PDR) as follows where:
PDR = PDR for the integral system, at the
and record the result along with the test conditions (tempera-
diffusion measured
ture, average test pressure P and maximum pressure same P and temperature.
test,avg Test
P ):
9.1.8 For most practical applications of the test sufficient
test,max
accuracy can be obtained by taking the conservative approach
P 2 P
i f
PDR 5
measured
t and assuming that all the pressure decay is related entirely to
leaks (PDR = 0).
diffusion
where:
9.2 Vacuum Decay Test—TheVDTisconductedwithairon
PDR = measured pressure decay rate, kPa/min at
measured
both sides of the membrane. For complete wet-out of all the
theaveragetestpressure, P = P + P
test,ave i f
membrane in the system, the system should be operated at its
/2,
normal pressure before the test is performed. The steps
P = initial pressure, kPa gauge,
i
involved in the VDT are:
P = final pressure, kPa gauge,
f
9.2.1 Drain the liquid from the feed side of the membrane
t = timetakenforpressuretodecayfromP to
i
P, mins, and (referred to here as the upstream side), and let it remain open
f
P = maximum test pressure given as the pres-
to the atmosphere. For membrane devices placed horizontally,
test,max
sure at the start of the test, kPa.
the feed and exit ports must be located on the bottom of the
9.1.7 The PDR will result from diffusion through the
device housings in order for this to work.
membrane wall, as well as leaks through defects, damaged
9.2.2 Usetheequipmentconnectedinthisorder(seeFig.2):
membranes,orseals.Thediffusivecomponentoftheairflowis
a vacuum pressure gauge, an isolation valve, a water trap that
not related to the integrity, so a more accurate estimate of the
will not buckle at vacuum, and a vacuum pump, to the
nondiffusive pressure decay can be obtained by subtracting the
permeate manifold that serves one or more membrane devices.
Addition of another isolation valve (B) at the permeate header
allows easy connection of the equipment without disrupting
The pressure decay rate at the start of the test is usually quite high due to
operation of the membrane system.
displacement of some of the liquid in the membrane wall. The time taken for the
decay rate to stabilize will be different for different systems, but may take up to 3
9.2.3 Open isolation valves A and B and run the vacuum
min.
pump to evacuate the permeate side until the pressure gauge
Due to the nonlinear decay in pressure with time and the desire to simplify the
shows a stable vacuum. The water removed during this
equations by using the first order approximation for decay rate, the maximum time
should be such that P is no more than 10% lower than P. operationiscollectedinthewatertrap.CloseisolationvalveA.
f i
D6908–03
FIG. 2 Connection Arrangement for the VDT
Start the stopwatch and record the initial vacuum (P).The test can contribute to the pressure or vacuum decay rate. The
i
vacuum can be selected using the guidelines in 9.3. relationshipbetweenthetestpressureandtheequivalentdefect
9.2.4 After the determined time (60 s is a typical time, 120, diameterisgivenbyEq1.Defectssmallerthanthiswillbetoo
180 or 300 s will yield a more sensitive test) record the final small for the bubble point to be overcome and thus will not
pressure (P) and the time (t) for reaching this value. contribute to airflow. Larger defects will allow airflow as the
f
9.2.5 Calculate the Vacuum Decay Rate (VDR) as fo
...