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Significance and Use
5.1 In the design and operation of RO installations, it is important to predict the calcium carbonate scaling properties of the concentrate stream. Because of the increase in total dissolved solids in the concentrate stream and the difference in passages for calcium ion, bicarbonate ion, and free carbon dioxide, the calcium carbonate scaling properties of the concentrate stream will generally be quite different from those of the feed solution. This practice permits the calculation of the Langelier saturation index for the concentrate stream from the feed water analyses and the RO operating parameters.
5.2 A positive Langelier saturation index indicates the tendency to form a calcium carbonate scale, which can be damaging to RO performance. This practice gives various procedures for the adjustment of the Langelier saturation index.
5.3 The tendency to form calcium carbonate scale can be suppressed by the addition of antiscalents or crystal modifiers. Suppliers of antisealents and crystal modifiers can provide information on the scale inhibition peformance of these types of chemical. Their use may be appropriate for reducing scale formation in 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.
1.1 This practice covers the calculation and adjustment of the Langelier saturation index for the concentrate stream of a reverse osmosis (RO) device. This index is used to determine the need for calcium carbonate (CaCo3) scale control in the operation and design of RO installations. This practice is applicable for concentrate streams containing 10 to 10 000 mg/L of total dissolved solids. For concentrate containing over 10 000 mg/L, see Practice .
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4 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.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
D511 Test Methods for Calcium and Magnesium In Water
D1067 Test Methods for Acidity or Alkalinity of Water
D1129 Terminology Relating to Water
D1293 Test Methods for pH of Water
D1888 Methods Of Test for Particulate and Dissolved Matter in Water
D4194 Test Methods for Operating Characteristics of Reverse Osmosis and Nanofiltration Devices
D4195 Guide for Water Analysis for Reverse Osmosis and Nanofiltration Application
D4582 Practice for Calculation and Adjustment of the Stiff and Davis Stability Index for Reverse Osmosis
D6161 Terminology Used for Microfiltration, Ultrafiltration, Nanofiltration, and Reverse Osmosis Membrane Processes
ICS Number Code 07.030 (Physics. Chemistry)
|Link to Active (This link will always route to the current Active version of the standard.)|
ASTM D3739-19, Standard Practice for Calculation and Adjustment of the Langelier Saturation Index for Reverse Osmosis, ASTM International, West Conshohocken, PA, 2019, www.astm.orgBack to Top