ASTM D3739-94(1998)

Standard Practice for Calculation and Adjustment of the Langelier Saturation Index for Reverse Osmosis

SCOPE
1.1 This practice covers the calculation and adjustment of the Langelier saturation index for the concentrate stream of a reverse osmosis device. This index is used to determine the need for calcium carbonate scale control in the operation and design of reverse osmosis installations. This practice is applicable for concentrate streams containing up to 10 000 mg/L of total dissolved solids.
1.2 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-Dec-1998
• ICS: 07.030 - Physics. Chemistry
• Technical Committee: D19 - Water
• Drafting Committee: D19.08 - Membranes and Ion Exchange Materials

Relations

• Replaced By: ASTM D3739-94(2003) - Standard Practice for Calculation and Adjustment of the Langelier Saturation Index for Reverse Osmosis
• Effective Date: 10-Jun-2003
• Referred By: ASTM D6161-19 - Standard Terminology Used for Microfiltration, Ultrafiltration, Nanofiltration, and Reverse Osmosis Membrane Processes
• Effective Date: 10-Dec-1998
• Referred By: ASTM D4582-23 - Standard Practice for Calculation and Adjustment of the Stiff and Davis Stability Index for Reverse Osmosis
• Effective Date: 10-Dec-1998

Standards Content (Sample)

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: D 3739 – 94 (Reapproved 1998)
Standard Practice for
Calculation and Adjustment of the Langelier Saturation
Index for Reverse Osmosis
This standard is issued under the fixed designation D 3739; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 4. Summary of Practice
1.1 This practice covers the calculation and adjustment of 4.1 This practice consists of calculating the Langelier satu-
the Langelier saturation index for the concentrate stream of a ration index for a reverse osmosis concentrate stream from the
reverse osmosis device. This index is used to determine the total dissolved solids, calcium ion content, total alkalinity, pH,
need for calcium carbonate scale control in the operation and and temperature of the feed solution, and the recovery of the
design of reverse osmosis installations. This practice is appli- reverse osmosis system.
cable for concentrate streams containing up to 10 000 mg/L of 4.2 This practice also presents techniques to lower the
total dissolved solids. Langelier saturation index by decreasing the recovery, by
1.2 This standard does not purport to address all of the decreasing the calcium content of the feedwater, or by chang-
safety concerns, if any, associated with its use. It is the ing the ratio of total alkalinity to free carbon dioxide in the
responsibility of the user of this standard to establish appro- feedwater.
priate safety and health practices and determine the applica-
5. Significance and Use
bility of regulatory limitations prior to use.
5.1 In the design and operation of reverse osmosis installa-
2. Referenced Documents
tions, it is important to predict the calcium carbonate scaling
2.1 ASTM Standards: properties of the concentrate stream. Because of the increase in
D 511 Test Methods for Calcium and Magnesium in Water total dissolved solids in the concentrate stream and the differ-
D 1067 Test Methods for Acidity or Alkalinity of Water ence in passages for calcium ion, bicarbonate ion, and free
D 1129 Terminology Relating to Water CO , the calcium carbonate scaling properties of the concen-
D 1293 Test Method for pH of Water trate stream will generally be quite different from those of the
D 1888 Test Methods for Particulate and Dissolved Matter feed solution. This practice permits the calculation of the
in Water Langelier saturation index for the concentrate stream from the
D 4194 Test Methods for Operating Characteristics of feed water analyses and the reverse osmosis operating param-
Reverse Osmosis Devices eters.
5.2 A positive Langelier saturation index indicates the
3. Terminology
tendency to form a calcium carbonate scale, which can be
3.1 For definitions of terms used in this practice, refer to
damaging to reverse osmosis performance. This practice gives
Terminology D 1129. various procedures for the adjustment of the Langelier satura-
3.2 Definitions of Terms Specific to This Standard:
tion index.
3.2.1 For descriptions of terms relating to reverse osmosis, 5.3 The tendency to form CaCo scale can be suppressed by
refer to Test Methods D 4194.
the addition of antisealents or crystal modifiers. Suppliers of
3.2.2 Langelier saturation index—an index calculated from antisealents and crystal modifiers can provide information on
total dissolved solids, calcium concentration, total alkalinity,
the scale inhibition peformance of these types of chemical.
pH, and solution temperature that shows the tendency of a Their use may be appropriate for reducing scale formation in
water solution to precipitate or dissolve calcium carbonate.
RO systems. The RO system supplier should be consulted prior
to the use of antisealents and crystal modifiers to ensure they
will not have a negative impact on the RO system.
This practice is under the jurisdiction of ASTM Committee D-19 on Water and
is the direct responsibility of Subcommittee D19.08 on Membranes and Ion 6. Procedure
Exchange Materials.
6.1 Determine the calcium concentration in the feed solu-
Current edition approved Sept. 15, 1994. Published November 1994. Originally
tion in accordance with Test Methods D 511 and express as
published as D 3739 – 78. Last previous edition D 3739 – 88 (1993).
Annual Book of ASTM Standards, Vol 11.01.
CaCO .
Discontinued—See 1989 Annual Book of ASTM Standards, Vol 11.01.
6.2 Determine the total dissolved solids of the feed solution
Annual Book of ASTM Standards, Vol 11.02.
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 3739
using Test Methods D 1888. osmosis system, and the passage of alkalinity, by:
6.3 Determine the total alkalinity of the feed solution using
1 2 Y~SP !
alk
Alk 5 Alk 3 (5)
Test Methods D 1067, and express as CaCO .
c f
3 1 2 Y
6.4 Measure the pH of the feed solution using Test Method
where:
D 1293.
Alk 5 alkalinity in concentrate, as CaCO , mg/L,
6.5 Measure the temperature of the feed solution. c 3
Alk 5 alkalinity in feed, as CaCO , mg/L,
f 3
7. Calculation
Y 5 recovery of the reverse osmosis system, expressed
7.1 Calculate the calcium concentration in the concentrate as a decimal, and
SP 5 alkalinity passage, expressed as a decimal.
stream from the calcium concentration in the feed solution, the
alk
recovery of the reverse osmosis system, and the calcium ion
NOTE 3—SP is dependent on the pH of the feed solution and its value
alk
passage as follows:
should be obtained from the supplier of the specific reverse osmosis
system.
1 2 Y SP !
~
Ca
Ca 5 Ca 3 (1)
c f
1 2 Y
7.4 Calculate the free carbon dioxide content (C)inthe
concentrate stream by assuming that the CO concentration in
where:
the concentrate is equal to the CO concentration in the feed:
Ca 5 calcium concentration in concentrate, as CaCO ,
c 3
C 5 C . The concentration of free carbon dioxide in the feed
c f
mg/L,
solution is obtained from Fig. 1 as a function of the alkalinity
Ca 5 calcium concentration in feed, as CaCO , mg/L,
f 3
and the pH of the feed solution.
Y 5 re
...