SI

k_sp^a

CF around 3

Before recycling

after 4 d of recycling

after 11 d of recycling

pH of RO concentrate

-

-

7.4

7.1

6.9

Calcite

CaCO₃

2.80 × 10⁻⁹

−0.06

−0.21

−0.38

Gypsum

CaSO₄∙2H₂O

4.93 × 10⁻⁵

−1.29

−1.21

−1.10

Hydroxyapatite

Ca₅(PO₄)₃OH

2.34 × 10⁻⁵⁹

6.76

4.53

3.93