Samples were added to the beakers at different
dosages (from 0.125 to 2.5 mL/L turbid water) and the content was stirred at 200 rpm for 1 min. The mixing speed was then reduced
to 60 rpm and was kept for 30 min. Then, the suspensions were
left to allow sedimentation. After 1 h of sedimentation, upper clarified
liquid was collected and residual turbidity was measured. The
residual turbidity of sample was RTS. The same coagulation test was
performed with no coagulant as the blank. The residual turbidity
in the blank was RTB. Coagulation activity was calculated as: