Significance and Use
In the design and operation of reverse osmosis 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 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.
A positive S & DSI indicates the tendency to form a calcium carbonate scale, which can be damaging to reverse osmosis performance. This practice gives procedures for the adjustment of the S & DSI.
1.1 This practice covers the calculation and adjustment 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 and design of reverse osmosis installations. This practice is applicable for concentrate streams containing more than 10 000 mg/L of total dissolved solids. For concentrate streams containing less than 10 000 mg/L of total dissolved solids, refer to Practice D3739.
1.2 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 (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
D3739 Practice for Calculation and Adjustment of the Langelier Saturation Index for Reverse Osmosis
D4194 Test Methods for Operating Characteristics of Reverse Osmosis and Nanofiltration Devices
D4195 Guide for Water Analysis for Reverse Osmosis and Nanofiltration Application
D6161 Terminology Used for Microfiltration, Ultrafiltration, Nanofiltration and Reverse Osmosis Membrane Processes
calcium carbonate; membrane scaling; reverse osmosis (RO); stability index for RO; Stiff and Davis Stability Index (S & DSI); Stability; Stiff and Davis stability index; Brackish water/brines; Calcium carbonate (CaCO3) scaling properties; Concentration (of elements); Desalinating (reverse osmosis) devices; Free carbon dioxide; Fresh water; Permeability; Reverse osmosis (RO) installations; Salt passage; S & DSI; Seawater (natural/synthetic) ;
ICS Number Code 71.120.99 (Other equipment for the chemical industry)
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