Cyclotella, a diatom with a density of
1,114 kg m"3 and an average diameter 6 um, does
not settle rapidly and based on a Stokes’ Law
calculation for removal in a conventional settler at
overflow rate of 1 m h_l the required diameter for a
fioc of cells at the same density would be 88 pm
(Edzwald 1993). Alum flocculated Cyclorella has a
lower density of 1,001 kg m_3 than Cyclotella cells
and the fioc particle diameter would need to be
210 um for settlement at 20 °C (Edzwald 1993). Alum
flocs typically range in diameter from 30 to 400 um
(Hendricks 2010). but low density algal flocs can be
difficult to separate by sedimentation (Edzwald 1993)