Floating Floc - From the Water and Wastewater.com Help Forum

Water and Wastewater.com Help Forum - Floating Floc: "Floating Floc

� on: Jan 25^th, 2005, 11:14pm �"

a part of the flocs is floating when their density is lower than water, obviously. Possible causes are entrapment of gases or oil or both.
The problem might be approached by
# implementing or improving oil/grease separation before coagulation/flocculation. This might also help to reduce costs for chemicals, sludge.
# reduction of or removal of gases entrapped. Perhaps the mixing regime can be modified.
# reduction of floc erosion or increase of time for floc formation to agglomerate the lighter flocs with the bulk of flocs.
# another flocculant might be more effective in forming flocs heavier than water only.

if you are unable to separate the oil before coagulation/flocculation I would suggest addition of bentonite or modified clays for binding of the oil.
As an alternative to add cationic or anionic polymer you should consider dual flocculation, i.e adding them on after the other.
This will require some extensive testing to determine the right order and concentration.
I would guess a small amount of anionic polymer first followed by cationic might work.