(Fun) Facts about Tube Floc

What is a floc?

Floc is an aggregation of dirty particles in water. Particles are moving at different speed in the tube (as shown in the figure below) and cause particle collisions, thus forming "flocs". Our goal is to form as many flocs as possible, so that they precipitate out in the sedimentation process.

What is a tube floc?

The tube flocculator in the lab allows us to investigate the flocculation process in particular. Using Process Controller, we can isolate all parameters of flocculator in order to understand how each parameter affects the process.

Major Components

• Computer with process controller installed
• Alum stock solution
• Clay stock solution
• 3 pumps for alum, raw water, and clay solution
• Influent and Effluent turbidimeter
• Elongated vertical flocculator
• Settling column (long glass tube)
• Pressure sensor

What cool experiments have we done so far?
We've done so many cool things. Apart from collecting settling datasets to the process controller and analyze them, we also took videos and planning to track how the particles move and behave.

Checklist for the setup

• Make sure all connection is tight.
• Make sure that there is no clogging in the flocculator and pump tubes
• Get rid of bubbles in the flocculator tube
• Check the pump tube size and the setting on the pump panel
• Check if the tube all goes in the correct direction, especially if you have made changes with the tube setup
• The cables connecting pump and the computer are easily unplugged, so check them out!

Stock preparation

¹ Humic acid is added to the clay stock solution

Checklist for the Process Controller

The details on Process Controller can be viewed here

• Check the source page
• Check the location of data stored

Troubleshooting

What to do if you don't see any flocs forming in the settling tube?

• Always check tube connections and make sure there is no clogging in the connections.
• Check the stock solutions. Make sure that there is no sedimentation occurring in clay and alum stock solutions.
• Check the influent turbidimeter. If it displays lower turbidity, then check the clay and alum stock solutions. Check if the flow coming out of the pumps (You can check clay/alum flow rates with timer and graduated cylinder) Change in the process controller so that it will give correct value of clay/alum.
• Check bubbles in the flocculator and settling tubes, especially at the entrance of the settling column. Flocs could get trapped in the bubbles and get broken.

Tube Flocculator is too dirty! How should I clean tube flocculator? (Credit to Monroe)

After you run many sets of experiments, the particles get attached and accumulate in the flocculator tubes, so it's harder to observe what's going on in the tubes and might break up flocs.

Procedure:

1. Turn the Process Controller OFF
2. Prepare a small peg by the size of tube inner diameter by cutting the sponge
3. Insert the peg at the starting point of the tube flocculator
4. Press the pressure bottle (200kPa) to move the peg in
5. Turn the Process Controller ON (State 2 - Clean Flocculator)
6. Watch it does its magic
7. Turn the Process Controller OFF when it almost reaches the end of tube.

I opened up a Process Controller method, but all the states are gone.