Floc Blanket Formation

Although the plate settler spacing team is not directly concerned about the formation of floc blankets, we cannot ignore how they affect our system because of the effect they have on the quality of the effluent. Floc blankets may form at different rates based on how the system is set up; one of the differences we are testing is if the presence of a mesh is significant.

Our mesh is made out of a circular piece of plastic with the same diameter as the channel with lots of holes drilled into it. These holes are about 3/4 of a centimeter in diameter, so as to not break up the flocs that we formed. The whole purpose of this mesh is to assist the water to disperse evenly coming into the sedimentation channel.
For our tests, we have a digital camera set up that takes pictures of the floc blanket during formation. These pictures are taken every minute, allowing us to track the height of the floc blanket at any given time. We have tape on the sedimentation column that marks the height of the floc blanket to use as a reference.

This shows the height of the floc blanket in relation to the time the system has been on. There is a gap at the beginning of the data because there needs to be an initial accumulation of flocs in the column in order to form a blanket.

We noticed that the latter portion of the graph was linear, and created a trendline to give the data about the rate of formation. This would imply that about an hour and a half into formation, the floc blanket builds at a rate of about 0.3cm per minute, or 18.28cm per hour. It is hypothesized that during the initial hour and a half, the floc blanket is beginning to form and to compact upon itself, but only starts growing at a steady rate after this time has passed.

Without the Presence of a Mesh

This time, the experiment was run with the mesh removed, keeping everything else constant.

The slope of the trendline is different in this case. The floc blanket forms at a rate of 15.785cm per hour. This is slower than in the presence of a mesh, and therefore the full floc blanket takes about 4 hours to form, as opposed to 3.5 hours.