ASTM D4993-89(1998)e1

Standard Practice for Calculation and Adjustment of Silica (SiO₂) Scaling for Reverse Osmosis

SCOPE
1.1 This practice covers the calculation and adjustment of silica (SiO2) for the concentrate stream of a reverse osmosis system. The calculations are used to determine the need for scale control in the operation and design of reverse osmosis installations. This practice is applicable for all types of reverse osmosis devices (tubular, spiral wound, and hollow fiber).
1.2 This practice is applicable to both brackish waters and seawaters.
1.3 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems 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: 71.060.20 - Oxides
• Technical Committee: D19 - Water
• Drafting Committee: D19.08 - Membranes and Ion Exchange Materials

Relations

• Replaced By: ASTM D4993-89(2003) - Standard Practice for Calculation and Adjustment of Silica (SiO₂) Scaling for Reverse Osmosis
• Effective Date: 10-Jun-2003

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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.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.
e1
Designation: D 4993 – 89 (Reapproved 1998)
Standard Practice for
Calculation and Adjustment of Silica (SiO ) Scaling for
Reverse Osmosis
This standard is issued under the fixed designation D 4993; 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.
e NOTE—Keywords were added editorially in December 1998.
1. Scope of the reverse osmosis system.
4.2 This practice also presents techniques to eliminate
1.1 This practice covers the calculation and adjustment of
scaling by decreasing the recovery, decreasing the SiO con-
silica (SiO ) for the concentrate stream of a reverse osmosis
centration in the feedwater, adjusting the pH of the feedwater,
system. The calculations are used to determine the need for
and increasing the temperature of the feedwater.
scale control in the operation and design of reverse osmosis
installations. This practice is applicable for all types of reverse
5. Significance and Use
osmosis devices (tubular, spiral wound, and hollow fiber).
5.1 In the design and operation of reverse osmosis installa-
1.2 This practice is applicable to both brackish waters and
tions, it is important to predict the SiO scaling properties of
seawaters.
the concentrate stream. Because of the increase in the concen-
1.3 This standard does not purport to address all of the
tration of SiO and the change in pH, the scaling property of
safety concerns, if any, associated with its use. It is the
the concentrate stream will be quite different from that of the
responsibility of the user of this standard to establish appro-
feed solution. This practice permits the calculation of the
priate safety and health practices and determine the applica-
scaling potential for the concentrate stream from the feedwater
bility of regulatory limitations prior to use.
analysis and the reverse osmosis operating parameters.
2. Referenced Documents 5.2 Scaling by SiO will adversely affect the reverse osmo-
sis performance. This practice gives various procedures for the
2.1 ASTM Standards:
prevention of scaling.
D 859 Test Method for Silica in Water
+3
5.3 The presence of certain metals, for example, Al , may
D 1067 Test Methods for Acidity or Alkalinity in Water
significantly alter the solubility of SiO via formation of
D 1129 Terminology Relating to Water
insoluble metal silicates. This practice does not address this
D 1293 Test Methods for pH of Water
phenomena.
D 3739 Practice for Calculation and Adjustment of Lange-
lier Saturation Index for Reverse Osmosis
6. Procedure
D 4194 Test Methods for Operating Characteristics of Re-
3 6.1 Determine the concentration of SiO in the feed stream
verse Osmosis Devices
in accordance with Test Method D 859.
3. Terminology 6.2 Measure the temperature of the feed solution.
6.3 Measure the pH of the feed solution using Test Methods
3.1 For definitions of terms relating to water used in this
D 1293.
practice, refer to Terminology D 1129. For terms relating to
reverse osmosis, refer to Test Methods D 4194.
NOTE 1—If acid is used for control of CaCO scale, measure the pH
after acid addition.
4. Summary of Practice
6.4 Determine the total alkalinity of the feed solution using
4.1 This practice consists of calculating the potential for
Test Methods D 1067 and express as CaCO .
scaling by SiO in a reverse osmosis concentrate stream from
NOTE 2—If acid is used for control of calcium carbonate (CaCO )
the concentration of SiO in the feed solution and the recovery 3
scale, determine the total alkalinity after acid addition.
7. Calculation
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
7.1 Calculate the SiO concentration in the concentrate
Exchange Materials.
stream from the SiO concentration in the feed solution, the
Current edition approved Oct. 27, 1989. Published March 1990.
2 recovery of the reverse osmosis system, and the SiO passage
Annual Book of ASTM Standards, Vol 11.01.
Annual Book of ASTM Standards, Vol 11.02. as follows:
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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 4993
of the feed stream using the procedure given in Practice
D 3739.
NOTE 4—For seawater systems, the calculated pH of the concentrate
stream can be 0.1 to 0.2 higher than measured pH values if the feed pH is
above 7.0. In these cases, empirical correlations between the feed pH and
the concentrate pH as a function of conversion can be used to more
accurately calculate the concentrate pH. Check with the supplier of the
reverse osmosis device to determine if empirical correlations should be
used.
7.3 From Fig. 1, obtain the solubility of SiO as a function
of temperature (SiO ).
2temp.
NOTE 5—Temperature of the
...