S&DSI — Stiff & Davis Stability Index
High-TDS companion to LSI. Use for RO reject, seawater and brackish water above roughly 10,000 mg/L TDS, where LSI loses accuracy.
Ionic strength I
0.375mol/L
K(I,T)
2.29
Saturation pH (pHs)
6.69
S&DSI · Scale-forming
+1.11
Tendency to scale on RO membranes and heat surfaces. Antiscalant advised.
S&DSI verdict
At pH 7.8, 25 °C, TDS 15000 mg/L (ionic strength 0.375 mol/L): pHs = 6.69, S&DSI = +1.11. Water is scale-forming.
Tendency to scale on RO membranes and heat surfaces. Antiscalant advised.