2.3. Preparation of turbid water
Turbid water for coagulation tests was prepared by adding 1 g
kaolin to 1 L tap water. The suspension was stirred for 1 h to achieve
uniform dispersion of kaolin particles, and then it was allowed to
remain for 24 h for completing hydration of the particles. This suspension
was used as the stock suspension. Turbid water having
35 nephelometric turbidity units (NTU) was prepared by diluting of
stock suspension to 1000 mL tap water just before the coagulation
test. The initial pH of the synthetic water was adjusted to 9.0, 9.5 or
10.0 with 1 mol/L NaOH, in accordance to previous investigations
(ˇS ´ciban et al., 2005) just before experiments.