ASTM D4189-23

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: D4189 − 23
Standard Test Method for
Silt Density Index (SDI) of Water
This standard is issued under the fixed designation D4189; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
3.1 Definitions—For definitions of terms used in this test
1.1 This test method covers the determination of the silt
method, refer to Terminology D1129.
density index (SDI) of water. This test method can be used to
indicate the quantity of particulate matter in water and is
3.2 Definitions:
applicable to relatively low (<1.0 NTU) turbidity waters such
3.2.1 silt density index (SDI), n—an index calculated from
as well water, filtered water, or clarified effluent samples. Since
the rate of plugging of a 0.45 μm membrane filter.
the size, shape, and nature of particulate matter in water may
vary, this test method is not an absolute measurement of the 4. Summary of Test Method
quantity of particulate matter.
4.1 Water is passed through a 0.45 μm membrane filter at a
constant applied gauge pressure of 207 kPa (30 psi), and the
1.2 This test method is not applicable for reagent grade
rate of plugging of the filter is measured.
water Types I, II, and III of Specification D1193, or effluents
from most reverse osmosis and ultrafiltration systems.
4.2 The SDI is calculated from the rate of plugging.
1.3 This standard does not purport to address all of the
5. Significance and Use
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- 5.1 The SDI can serve as a useful indication of the quantity
priate safety, health, and environmental practices and deter- of particulate matter in water.
mine the applicability of regulatory limitations prior to use.
5.2 The SDI can be used to determine effectiveness of
1.4 This international standard was developed in accor-
various processes such as filtration or clarification used to
dance with internationally recognized principles on standard-
remove particulate matter.
ization established in the Decision on Principles for the
5.3 The SDI has been empirically correlated with the
Development of International Standards, Guides and Recom-
fouling tendency of some water treatment equipment such as
mendations issued by the World Trade Organization Technical
reverse osmosis devices.
Barriers to Trade (TBT) Committee.
5.4 The SDI may vary as a function of water temperature,
and values obtained at different temperatures may not neces-
2. Referenced Documents
sarily be comparable.
2.1 ASTM Standards:
5.5 The SDI can vary with the membrane filter manufac-
D1129 Terminology Relating to Water
turer. Thus, SDI values obtained with filters from different
D1193 Specification for Reagent Water
membrane manufacturers might not be comparable.
D3370 Practices for Sampling Water from Flowing Process
Streams
6. Apparatus
E1 Specification for ASTM Liquid-in-Glass Thermometers
6.1 SDI Assembly, as schematically described in Fig. 1. All
wetted parts should be made of high-quality stainless steel or
plastic to prevent contamination by corrosion products. Do not
This test method is under the jurisdiction of ASTM Committee D19 on Water
use reactive materials such as carbon steel or cast iron. Suitable
and is the direct responsibility of Subcommittee D19.08 on Membranes and Ion
filter holders, designed to withstand an operating gauge pres-
Exchange Materials.
Current edition approved Nov. 1, 2023. Published November 2023. Originally
sure of 350 kPa (50 psi) can be obtained from suppliers of
approved in 1982. Last previous edition approved in 2014 as D4189 – 07 (2014)
membrane filters.
which was withdrawn July 2023 and reinstated in November 2023. DOI: 10.1520/
D4189-23.
6.2 Membrane Filter:
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
6.2.1 Membrane—White hydrophilic, mixed cellulose ni-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
trate (50 % to 75 %) and cellulose acetate (MCE).
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. 6.2.2 Mean Pore Size—0.45 μm.
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D4189 − 23
7.5 Make sure the O-ring is in good condition and properly
placed. Replace the top half of the filter holder and close
loosely.
7.6 Bleed out trapped air by cracking the ball valve. Close
the valve and tighten the filter holder.
7.7 Open the ball valve. Simultaneously, using a stopwatch,
begin measuring the time required for the flow of 500 mL.
Adjust the pressure regulator as necessary to maintain a
constant feed pressure of 207 kPa 6 7 kPa (30 psi 6 1 psi)
throughout the test. Record the time (t ). Leave the valve open
i
for continued flow.
NOTE 3—Time (t ) to collect 500 mL should be within 610 % of the
i
time to collect 500 mL using nonplugging reference water at the same
water temperature. The nonplugging reference water can be obtained by
filtering distilled water through a 0.2 μm pore size membrane filter.
NOTE 4—If t is less than 90 % of the nonplugging time, the filter may
i
be cracked and a new filter should be used. If t is more than 110 % of the
i
nonplugging time, then a smaller sample size, that is, 250 mL or 100 mL
should be used.
FIG. 1 Apparatus for Measuring the Silt Density Index
NOTE 5—The 500 mL sample size is based on a 47 mm diameter filter.
If a different filter size is used, adjust the sample size in direct proportion
to the filter area.
6.2.3 Diameter—47 mm nominal, plain.
7.8 Measure and record the times to collect additional
6.2.4 Thickness—115 μm to 180 μm.
500 mL (Note 6) volumes of sample, s
...