Sedimentation Tank Hydraulics
| Wiki Markup |
|---|
{float:border=none}
!benryanconversion.jpg|width=200, border=0!
!AguaClara Honduras Trip 2011 323.jpg|width=200, border=0!
!AguaClara Honduras Trip 2011 317.jpg|width=200, border=0!
{float} |
Introduction
A floc blanket is a dense, fluidized bed of particles that forms in the sedimentation tank below the plate settlers. A floc blanket works like a mesh to trap small flocs, thereby reducing effluent turbidity. As flocs are continually resuspended in the blanket, sludge build up on the tank bottom is reduced. The sedimentation needs to be drained and cleaned less frequently, reducing the amount of clean water wasted.
The latest working design of the AguaClara sedimentation tank consists of an inlet manifold with vertical diffusers to channel water into the tank as a line source. A semi-circular half-pipe beneath the diffusers serve as a jet reverser to resuspend flocs. Plate
...
Sedimentation Tank Hydraulics
...
settlers placed above the inlet manifold that catch flocs
...
while allowing water to flow past the settlers into exit launders. The flocs
...
that settle out at the bottom of the sedimentation tank
...
are removed regularly by a sludge drain.
...
Implementing a floc blanket and a floc hopper in the sedimentation tank provide an additional method of filtration and will reduce sludge build up, instead allowing flocs to be wasted at a constant rate from the floc hopper.
Current and Future Research
| Excerpt |
|---|
One of our main goals of the semester was switching our coagulant to PACl instead of alum and see how the change affects performance. The PACl seemed to be much stickier than alum and we had problems with it sticking to the glass and insides of the flocculator. We also conducted experiments switching energy dissipation rates in the jet reverser. We were expecting to find a point where the energy dissipation rate is too high and performance decreased. We didn’t find a point where the floc breakup caused a decrease in performance. During these tests we actually found that momentum can play a large role in floc blanket failure because if the momentum of the floc sliding down the incline gets too large it can overpower the pet reverser and cause it to fill up. We also looked at sludge consolidation depending on the depth of the floc hopper. We found that the depth can make a large difference in consolidation. |
More Information
Sedimentation Team Research Rationale
Sedimentation Team Research Rationale2
Sedimentation Team Research Report 1
We wish to determine the geometry of sedimentation tanks so that uniform flow is achieved and dead zones are eliminated, which would improve the efficiency of the current tank design and decrease the labor needed to maintain a clean tank. Given a particular upflow velocity, under these hydraulic conditions we may also experiment with floc blanket formation, which we believe will provide a second filtration stage for upward flowing flocs in the sedimentation tank and lower the turbidity of the effluent. Flocs may then be drawn off the blanket with a weir, minimizing the effort needed to clean the tank.
While our team is specifically looking at the floc blanket, some other aspects of the sedimentation tank may also be considered for an overall optimal design such as inlet manifold and the launder. You will be able to find past research on inlet manifold on the side bar.
...
...
| Section | ||||||
|---|---|---|---|---|---|---|
|