ASTM D4582-91(2001)
(Practice)Standard Practice for Calculation and Adjustment of the Stiff and Davis Stability Index for Reverse Osmosis
Standard Practice for Calculation and Adjustment of the Stiff and Davis Stability Index for Reverse Osmosis
SCOPE
1.1 This practice covers the calculation and adjustment of the Stiff and Davis Stability Index (S & DSI) 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 more than 10 000 mg/L of total dissolved solids. For concentrate streams containing less than 10 000 mg/L of total dissolved solids, refer to Practice D3739.
1.2 This standard does not purport to address the safety problems, 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.
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An American National Standard
Designation:D 4582–91(Reapproved 2001)
Standard Practice for
Calculation and Adjustment of the Stiff and Davis Stability
Index for Reverse Osmosis
This standard is issued under the fixed designation D 4582; 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 3.2.1 For description of terms relating to reverse osmosis,
refer to Test Methods D4194.
1.1 This practice covers the calculation and adjustment of
3.2.2 Stiff and Davis Stability Index (S & DSI) —an index
the Stiff and Davis Stability Index (S & DSI) for the concen-
calculated from total dissolved solids, calcium concentration,
trate stream of a reverse osmosis device. This index is used to
total alkalinity, pH, and solution temperature that shows the
determine the need for calcium carbonate scale control in the
tendency of a water solution to precipitate or dissolve calcium
operation and design of reverse osmosis installations. This
carbonate.
practice is applicable for concentrate streams containing more
than 10 000 mg/L of total dissolved solids. For concentrate
4. Summary of Practice
streams containing less than 10 000 mg/L of total dissolved
4.1 This practice consists of calculating the S & DSI index
solids, refer to Practice D3739.
for a reverse osmosis concentrate stream from the total
1.2 This standard does not purport to address all of the
dissolved solids, calcium ion content, total alkalinity, pH, and
safety concerns, if any, associated with its use. It is the
temperatureofthefeedsolutionandtherecoveryofthereverse
responsibility of the user of this standard to establish appro-
osmosis system.
priate safety and health practices and determine the applica-
4.2 This practice also presents techniques to lower the S &
bility of regulatory limitations prior to use.
DSI by decreasing the recovery; decreasing the calcium and
2. Referenced Documents alkalinity concentrations; or by changing the ratio of total
alkalinity to free carbon dioxide in the feedwater.
2.1 ASTM Standards:
D511 TestMethodsforCalciumandMagnesiuminWater
5. Significance and Use
D1067 Test Methods for Acidity or Alkalinity of Water
5.1 In the design and operation of reverse osmosis installa-
D1129 Terminology Relating to Water
2 tions, it is important to predict the calcium carbonate scaling
D1293 Test Methods for pH of Water
propertiesoftheconcentratestream.Becauseoftheincreasein
D1888 Test Methods for Particulate and Dissolved Matter
3 total dissolved solids in the concentrate stream and the differ-
in Water
encesinsaltpassagesforcalciumion,bicarbonateion,andfree
D3739 Practice for Calculation and Adjustment of Lange-
4 CO , the calcium carbonate scaling properties of the concen-
lier Saturation Index for Reverse Osmosis
trate stream will generally be quite different from those of the
D4194 Test Methods for Operating Characteristics of Re-
4 feed solution. This practice permits the calculation of the S &
verse Osmosis Devices
DSI for the concentrate stream from the feed water analyses
D4195 Guide for Water Analysis for Reverse Osmosis
4 and the reverse osmosis operating parameters.
Application
5.2 A positive S & DSI indicates the tendency to form a
3. Terminology calcium carbonate scale, which can be damaging to reverse
osmosis performance. This practice gives procedures for the
3.1 Definitions—For definitions of terms used in the prac-
adjustment of the S & DSI.
tice, refer to Terminology D1129.
3.2 Definitions of Terms Specific to This Standard:
6. Procedure
6.1 Determine the calcium concentration in the feed solu-
1 tion in accordance with Test Methods D511 and express as
This practice is under the jurisdiction ofASTM Committee D19 on Water and
is the direct responsibility of Subcommittee D19.08 on Membranes and Ion CaCO .
Exchange Materials.
Current edition approved June 28, 1991. Published September 1991. Originally
published as D4582–86. Last previous edition D4582–86(1991).
2 5
Annual Book of ASTM Standards, Vol 11.01. Stiff, H. A. and Davis, L. E., “A Method for Predicting the Tendency of Oil
Discontinued; see 1990 Annual Book of ASTM Standards, Vol 11.01. Field Waters to Deposit Calcium Carbonate,” Petroleum Transactions, Vol 195,
Annual Book of ASTM Standards, Vol 11.02. 1952.
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D 4582–91 (2001)
6.2 Determine the total dissolved solids of the feed solution 7.4 Calculate the ion strength of the concentrate stream
using Test Methods D1888. from the ionic strength of the feed solution, the recovery, and
6.3 Determine the total alkalinity of the feed solution using the total dissolved solids of the feed solution by:
Test Methods D1067 and express as CaCO .
10 2TDS 1
f
6.4 MeasurethepHofthefeedsolutionusingTestMethods I 5I
F G
c f
1 1 2 y
F G
10 2 ~TDS !
D1293. S D
f
1 2 y
6.5 Measure the temperature of the feed solution.
6.6 Measure the concentration of all major ions using the
where:
methods cited in Guide D4195. At a minimum, measure the
++ + + 5 −
I = ionic strength of the concentrate stream and
c
concentration of Mg ,Na ,K ,SO , and Cl .
TDS = total dissolved solids of the feed solution, mg/L.
f
7.5 From Fig. 1, obtain pCa as a function of Ca and pAlk
c
7. Calculation
as a function of Alk . From Fig. 2 obtain the constant K as a
c
7.1 Calculate the calcium concentration in the concentrate
function of concentrate ionic strength and feed temperature.
streamfromthecalcium concentration in the feed solution,the
7.5.1 Calculate the pH at which the concentrate stream is
recovery of the reverse osmosis system, and the calcium ion
saturated with CaCO (pH ) as follows:
3 s
passage as follows:
pH 5 pCa 1 pAlk 1 K
s
1 2y~SP !
Ca
Ca 5Ca 3
7.6 Calculate the free carbon dioxide content (C) in the
c f
1 2 y
concentrate stream by assuming that the CO concentration in
where:
the co
...
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