ASTM_D_3739_-_06_2010.pdf

Designation:D373906(Reapproved 2010)Standard Practice forCalculation and Adjustment of the Langelier SaturationIndex for Reverse Osmosis1This standard is issued under the fixed designation D3739;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice covers the calculation and adjustment ofthe Langelier saturation index for the concentrate stream of areverse osmosis device.This index is used to determine theneed for calcium carbonate scale control in the operation anddesign of reverse osmosis installations.This practice is appli-cable for concentrate streams containing xx 10 to 10 000 mg/Lof total dissolved solids.For concentrate containing over10 000 mg/L see Practice D4582.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D511 Test Methods for Calcium and Magnesium In WaterD1067 Test Methods for Acidity or Alkalinity of WaterD1129 Terminology Relating to WaterD1293 Test Methods for pH of WaterD1888 Methods Of Test for Particulate and Dissolved Matterin Water(Withdrawn 1989)3D4194 Test Methods for Operating Characteristics of Re-verse Osmosis and Nanofiltration DevicesD4195 Guide for Water Analysis for Reverse Osmosis andNanofiltration ApplicationD4582 Practice for Calculation and Adjustment of the Stiffand Davis Stability Index for Reverse OsmosisD6161 Terminology Used for Microfiltration,Ultrafiltration,Nanofiltration and Reverse Osmosis Membrane Processes3.Terminology3.1 DefintionsFor definitions of terms used in thispractice,refer to Terminology D1129 and Terminology D6161.3.2 Definitions of Terms Specific to This Standard:3.2.1 For descriptions of terms relating to reverse osmosis,refer to Test Methods D4194.3.2.2 Langelier Saturation Indexan index calculated fromtotal dissolved solids,calcium concentration,total alkalinity,pH,and solution temperature that shows the tendency of awater solution to precipitate or dissolve calcium carbonate.4.Summary of Practice4.1 This practice consists of calculating the Langelier Satu-ration Index for a reverse osmosis concentrate stream from thetotal dissolved solids,calcium ion content,total alkalinity,pH,and temperature of the feed solution,and the recovery of thereverse osmosis system.4.2 This practice also presents techniques to lower theLangelier Saturation Index by decreasing the recovery,bydecreasing the calcium content of the feedwater,or by chang-ing the ratio of total alkalinity to free carbon dioxide in thefeedwater.5.Significance and Use5.1 In the design and operation of reverse osmosisinstallations,it is important to predict the calcium carbonatescaling properties of the concentrate stream.Because of theincrease in total dissolved solids in the concentrate stream andthe difference in passages for calcium ion,bicarbonate ion,andfree CO2,the calcium carbonate scaling properties of theconcentrate stream will generally be quite different from thoseof the feed solution.This practice permits the calculation of theLangelier Saturation Index for the concentrate stream from thefeed water analyses and the reverse osmosis operating param-eters.5.2 A positive Langelier Saturation Index indicates thetendency to form a calcium carbonate scale,which can be1This practice is under the jurisdiction of ASTM Committee D19 on Water andis the direct responsibility of Subcommittee D19.08 on Membranes and IonExchange Materials.Current edition approved May 1,2010.Published May 2010.Originallyapproved in 1978.Last previous edition approved in 2006 as D3739 06.DOI:10.1520/D3739-06R10.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 damaging to reverse osmosis performance.This practice givesvarious procedures for the adjustment of the Langelier satura-tion index.5.3 The tendency to form CaCo3scale can be suppressed bythe addition of antiscalents or crystal modifiers.Suppliers ofantisealents and crystal modifiers can provide information onthe scale inhibition peformance of these types of chemical.Their use may be appropriate for reducing scale formation inRO system