Tech Manual Excerpt
Water Chemistry and Pretreatment Calcium Fluoride Scale Prevention
Calcium Fluoride Fluoride levels in the feedwater of as low as 0.1 mg/L can create a scaling potential if Scale Prevention the calcium concentration is high. The calculation of the scaling potential is analogous to the procedure described in Calcium Sulfate Scale Prevention
(Form No. 45-D01553-en) for CaSO4. Calculation
1. Calculate the ionic strength of the concentrate stream (Ic) following the procedure described in Scaling Calculations (Form No. 45-D01551-en):
Eq. 1
2. Calculate the ion product (IPc) for CaF2 in the concentrate stream:
Eq. 2
where: m 2+ 2+ ( Ca )f = M Ca in feed, mol/L m – – ( F )f = M F in feed, mol/L
3. Compare IPc for CaF2 with the solubility product (Ksp) of CaF2 at the ionic
strength of the concentrate stream, Figure 2 /11/. If IPc ≥ Ksp, CaF2 scaling can occur, and adjustment is required.
Adjustments for CaF2 Scale Control The adjustments discussed in Calcium Sulfate Scale Prevention
(Form No. 45-D01553-en) for CaSO4 scale control apply as well for CaF2 scale control.
Page 1 of 3 Form No. 45-D01556-en, Rev. 4 April 2020 Figure 1: Ksp for SrSO4 versus ionic strength /10/
Page 2 of 3 Form No. 45-D01556-en, Rev. 4 April 2020 Figure 2: Ksp for CaF2 versus ionic strength /11/
Excerpt from FilmTec™ Reverse Osmosis Membranes Technical Manual (Form No. 45-D01504-en), Chapter 2, "Water Chemistry and Pretreatment."
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Page 3 of 3 Form No. 45-D01556-en, Rev. 4 April 2020