Coagulation test
Coagulation activity of fractions of natural coagulant prepared
by ultrafiltration as well as crude extract was evaluated in jar tester
VELP model FC6S. 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:
Coagulation activity (%)
= RTB −
RTS
RTB
·
100