ASTM D4993-08
(Practice)Standard Practice for Calculation and Adjustment of Silica (SiO2) Scaling for Reverse Osmosis
Standard Practice for Calculation and Adjustment of Silica (SiO<sub>2</sub>) Scaling for Reverse Osmosis
SIGNIFICANCE AND USE
In the design and operation of reverse osmosis installations, it is important to predict the SiO2 scaling properties of the concentrate stream. Because of the increase in the concentration of SiO2 and the change in pH, the scaling property of the concentrate stream will be quite different from that of the feed solution. This practice permits the calculation of the scaling potential for the concentrate stream from the feedwater analysis and the reverse osmosis operating parameters.
Scaling by SiO2 will adversely affect the reverse osmosis performance. This practice gives various procedures for the prevention of scaling.
The presence of certain metals, for example, Al+3, may significantly alter the solubility of SiO2 via formation of insoluble metal silicates. This practice does not address this phenomena.
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 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 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.
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Designation: D4993 − 08
StandardPractice for
Calculation and Adjustment of Silica (SiO ) Scaling for
2
1
Reverse Osmosis
This standard is issued under the fixed designation D4993; 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 4. Summary of Practice
1.1 This practice covers the calculation and adjustment of 4.1 This practice consists of calculating the potential for
silica (SiO ) for the concentrate stream of a reverse osmosis scaling by SiO in a reverse osmosis concentrate stream from
2 2
system. The calculations are used to determine the need for the concentration of SiO in the feed solution and the recovery
2
scale control in the operation and design of reverse osmosis of the reverse osmosis system.
installations. This practice is applicable for all types of reverse
4.2 This practice also presents techniques to eliminate
osmosis devices (tubular, spiral wound, and hollow fiber).
scaling by decreasing the recovery, decreasing the SiO con-
2
1.2 This practice is applicable to both brackish waters and centration in the feedwater, adjusting the pH of the feedwater,
seawaters. and increasing the temperature of the feedwater.
1.3 The values stated in SI units are to be regarded as
5. Significance and Use
standard. No other units of measurement are included in this
5.1 In the design and operation of reverse osmosis
standard.
installations, it is important to predict the SiO scaling prop-
2
1.4 This standard does not purport to address all of the
erties of the concentrate stream. Because of the increase in the
safety concerns, if any, associated with its use. It is the
concentration of SiO and the change in pH, the scaling
2
responsibility of the user of this standard to establish appro-
property of the concentrate stream will be quite different from
priate safety and health practices and determine the applica-
that of the feed solution. This practice permits the calculation
bility of regulatory limitations prior to use.
of the scaling potential for the concentrate stream from the
feedwater analysis and the reverse osmosis operating param-
2. Referenced Documents
eters.
2.1 ASTM Standards:
5.2 Scaling by SiO will adversely affect the reverse osmo-
2
D859 Test Method for Silica in Water
sis performance. This practice gives various procedures for the
D1067 Test Methods for Acidity or Alkalinity of Water
prevention of scaling.
D1129 Terminology Relating to Water
+3
5.3 The presence of certain metals, for example,Al , may
D1293 Test Methods for pH of Water
significantly alter the solubility of SiO via formation of
D3739 Practice for Calculation and Adjustment of the 2
insoluble metal silicates. This practice does not address this
Langelier Saturation Index for Reverse Osmosis
phenomena.
D4194 Test Methods for Operating Characteristics of Re-
verse Osmosis and Nanofiltration Devices
6. Procedure
D6161 Terminology Used for Microfiltration, Ultrafiltration,
6.1 Determine the concentration of SiO in the feed stream
Nanofiltration and Reverse Osmosis Membrane Processes
2
in accordance with Test Method D859.
3. Terminology
6.2 Measure the temperature of the feed solution.
3.1 Definitions—For definitions of terms relating to water
6.3 Measure the pH of the feed solution using Test Methods
used in this practice, refer to Terminology D1129 and D6161.
D1293.
NOTE 1—If acid is used for control of CaCO scale, measure the pH
3
after acid addition.
1
This practice is under the jurisdiction of ASTM Committee D19 on Water and
6.4 Determine the total alkalinity of the feed solution using
is the direct responsibility of Subcommittee D19.08 on Membranes and Ion
Exchange Materials.
Test Methods D1067 and express as CaCO .
3
Current edition approved May 1, 2008. Published May 2008. Originally
approved in 1989. Last previous edition approved in 2003 as D4993 – 89 (2003). NOTE2—Ifacidisusedforcontrolofcalciumcarbonate(CaCO )scale,
3
DOI: 10.1520/D4993-08. determine the total alkalinity after acid addition.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
D4993 − 08
FIG. 1 Solubility of SiO vs. Temperature
2
7. Calculation
7.1 Calculate the SiO concentration in the concentrate
2
stream from the SiO concentration in the feed solution, the
2
FIG. 2 SiO pH Correction Factor
recovery of the reverse osmosis system, and the SiO passage 2
2
as follows:
1 2 Y~SP !
SiO2
SiO 5 SiO 3
2c 2f
1 2 Y
7.5 Calculate the solubility of SiO corrected for pH
2
where:
(SiO ) by multiplying the solubility of SiO obtained in 7.3
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:D4993–89(Reapproved2003) Designation: D 4993 – 08
Standard Practice for
Calculation and Adjustment of Silica (SiO ) Scaling for
2
1
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.
1. Scope
1.1 This practice covers the calculation and adjustment of silica (SiO ) for the concentrate stream of a reverse osmosis system.
2
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
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 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.
2. Referenced Documents
2.1 ASTM Standards:
D 859 Test Method for Silica in Water
D 1067 Test Methods for Acidity or Alkalinity of Water
D 1129 Terminology Relating to Water
D 1293 Test Methods for pH of Water
D 3739Practice for Calculation and Adjustment of Langelier Saturation Index for Reverse Osmosis
Practice for Calculation and Adjustment of the Langelier Saturation Index for Reverse Osmosis
D 4194 Test Methods for Operating Characteristics of Reverse Osmosis and Nanofiltration Devices
3
D4194TestMethodsforOperatingCharacteristicsofReverseOsmosisandNanofiltrationDevices 6161 TerminologyUsedfor
Microfiltration, Ultrafiltration, Nanofiltration and Reverse Osmosis Membrane Processes
3. Terminology
3.1 For definitions of terms relating to water used in this practice, refer to Terminology D 1129 . For terms relating to reverse
osmosis, refer to Test Methods D4194and D 6161.
4. Summary of Practice
4.1 This practice consists of calculating the potential for scaling by SiO in a reverse osmosis concentrate stream from the
2
concentration of SiO in the feed solution and the recovery of the reverse osmosis system.
2
4.2 This practice also presents techniques to eliminate scaling by decreasing the recovery, decreasing the SiO concentration in
2
the feedwater, adjusting the pH of the feedwater, and increasing the temperature of the feedwater.
5. Significance and Use
5.1 In the design and operation of reverse osmosis installations, it is important to predict the SiO scaling properties of the
2
concentrate stream. Because of the increase in the concentration of SiO and the change in pH, the scaling property of the
2
concentratestreamwillbequitedifferentfromthatofthefeedsolution.Thispracticepermitsthecalculationofthescalingpotential
for the concentrate stream from the feedwater analysis and the reverse osmosis operating parameters.
5.2 Scaling by SiO will adversely affect the reverse osmosis performance. This practice gives various procedures for the
2
prevention of scaling.
1
This practice is under the jurisdiction of ASTM Committee D19 on Water and is the direct responsibility of Subcommittee D19.08 on Membranes and Ion Exchange
Materials.
e1
Current edition approved June 10, 2003. Published August 2003. Originally approved in 1989. Last previous edition approved in 1998 as D4993–89 (1998) .
Current edition approved May 1, 2008. Published May 2008. Originally approved in 1989. Last previous edition approved in 2003 as D 4993 – 89 (2003).
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1
---------------------- Page: 1 ----------------------
D4993–08
+3
5.3 The presence of certain metals, for example,Al , may significantly alter the solubility of SiO via formation of insoluble
2
metal silicates. This practice does not address this phenomena.
6. Procedure
6.1 Determine the concentration of SiO in the feed stream in accordance with Test Method D 859.
2
6.2 Measure the temperature of the feed solution.
6.3 Measure the pH of the feed solution using Test Methods D 1293.
NOTE 1—If acid is used for control of CaCO scale, measure the pH after acid addition.
3
6.4 Det
...
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