Designation: D 4582 – 91 (Reapproved 2001)
An American National Standard
Standard Practice for
Calculation and Adjustment of the Stiff and Davis Stability Index for Reverse Osmosis 1 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. A number in parentheses indicates the year of last reapproval. A superscript supers cript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Sco Scope pe
3.2.1 For description description of term termss relat relating ing to rever reverse se osmo osmosis, sis, refer to Test Methods D 4194. 3.2.2 Stiff and Davis Stability Index (S & DSI) 5—an index calculated from total dissolved solids, calcium concentration, total alkalinity, pH, and solution temperature that shows the tendency of a water solution to precipitate or dissolve calcium carbonate.
1.1 This practice practice cove covers rs the calculation calculation and adju adjustme stment nt 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 opera tion and desi design gn of rever reverse se osmo osmosis sis inst installa allations tions.. This practice is applicable for concentrate streams containing more than 10 000 mg/L of tota totall dissolved dissolved soli solids. ds. For conce concentra ntrate te streams strea ms containing containing less than 10 000 mg/L of tota totall diss dissolved olved solids, refer to Practice D 3739. 1.2 This sta standa ndard rd does not purport purport to add addre ress ss all of the safe sa fety ty co conc ncer erns ns,, if an anyy, as asso soci ciat ated ed wi with th it itss us use. e. It is th thee responsibility of the user of this standard to establish appro priate safety and health practices and determine the applicability of regulatory limitations prior to use.
4. Summ Summary ary of Practice Practice 4.1 This practice practice consists consists of calculating calculating the S & DSI index forr a re fo reve vers rsee os osmo mosi siss co conc ncen entr trat atee st stre ream am fr from om th thee to tota tall dissolved solids, calcium ion content, total alkalinity, pH, and temperature of the feed solution and the recovery of the reverse osmosis system. 4.2 This practice practice also presents presents techniques techniques to lower the S & DSI by decreasing the recovery; decreasing the calcium and alkali alk alinit nity y con concen centra tratio tions; ns; or by cha changi nging ng the rat ratio io of tot total al alkalinity to free carbon dioxide in the feedwater.
2. Referenced Documents 2.1 ASTM Standards: D 511 Te Test st Methods for Calcium and Magnesium in Water Water 2 D 1067 Test Methods for Acidity or Alkalinity Alkalinity of Water Water 2 D 1129 Ter Terminology minology Relating to Water 2 D 1293 Test Methods Methods for pH of Water 2 D 1888 Test Methods for Parti Particulat culatee and Dissolved Dissolved Matt Matter er in Water 3 D 3739 Pract Practice ice for Calcu Calculati lation on and Adjustment Adjustment of Lange Lange-lier Saturation Index for Reverse Osmosis 4 D 4194 Test Methods for Opera Operating ting Characteris Characteristics tics of Reverse Osmosis Devices 4 D 419 4195 5 Gui Guide de for Wate aterr Ana Analys lysis is for Rev Revers ersee Osm Osmosi osiss Application 4
5. Signi Significanc ficancee and Use 5.1 In the desig design n and oper operatio ation n of reverse osmosis osmosis installainstallations, 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 differences in salt passages for calcium ion, bicarbonate ion, and free CO2, 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 S & DSI for the concentrate stream from the feed water analyses and the reverse osmosis operating parameters. 5.2 A positive positive S & DSI indicat indicates es the ten tenden dency cy to for form m a calcium calc ium carbonate carbonate scal scale, e, whic which h can be dama damaging ging to rever reverse se osmosis performance. This practice gives procedures for the adjustment of the S & DSI.
3. Terminology 3.1 Definitions—For definitions of terms used in the practice, refer to Terminology D 1129. 3.2 Definitions of Terms Specific to This Standard:
6. Proc Procedur eduree 6.1 Deter Determine mine the calcium concentrati concentration on in the feed solu solu-tion in accordance with Test Methods D 511 and express as CaCO3.
1 This practice is under the jurisdiction of ASTM Committee D19 on Wa Water ter and is the dir direct ect resp respons onsibil ibility ity of Sub Subcom committ mittee ee D19 D19.08 .08 on Mem Membran branes es and Ion Exchange Materials. Currentt edition approved June 28, 1991. Publis Curren Published hed September 1991 1991.. Origin Originally ally published publis hed as D 4582 – 86. Last previo previous us edition D 4582 – 86 (1991). (1991). 2 Annual Book of ASTM Standard Standardss, Vol 11.01. 3 Discontinued Discon tinued;; see 1990 1990 Annual Annual Book of ASTM Standards, Standards , Vol 11.01. 4 Annual Book of ASTM Standard Standardss, Vol 11.02.
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Stiff, H. A. and Davis, L. E., “A Method for Predicting the Tendency of Oil Field Waters Waters to Deposit Deposit Calcium Carbonate,” Carbonate,” Petroleum Petroleum Trans Transactions actions,, Vol 195, 1952.
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