Basics on Tube Floc

(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.

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

cleaning Protocol

After running 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 this might contribute to a false effluent turbidity reading. Additionally, if the setup sits too long without any action, particles can build up in horizontal pieces of tubing and any connections.

Flocculator Cleaning

The flocculator should be cleaned regularly. Since the tubing is clear, it is visually obvious when the tubes need to be cleaned. Ideally, cleaning can be done between each major experiment, as it is not hard and takes only moments.

1. Turn the Process Controller to the OFF state
2. Prepare a small piece of sponge (cleaning sponge) by the size of tube inner diameter by cutting the sponge with scissors
3. Insert the piece of sponge at the starting point of the tube flocculator (right at the beginning of the clear flocculator tube)
4. Press the pressure bottle (200kPa) to move the sponge in
5. Turn the Process Controller ON (State 1 - Clean Flocculator)
6. The piece of sponge will move through the flocculator tubing, cleaning the sides of the tubes of any flocs as it moves
7. Turn the Process Controller OFF when it almost reaches the end of tube
8. Clean out the sponge and repeat if the flocculator tubing is excessively dirty

Influent Turbidity Vial

The vial inside the influent turbidimeter accumulates dirty water and does not do adequate self-cleaning. The influent turbidimeter vial should be cleaned just as often as the flocculator, as it contributes to false influent turbidity readings.

1. Turn off the Turbidimeter
2. Twist in the plastic stoppers on the tubing before and after the turbidimeter to stop flow from coming into the turbidimeter
3. Follow the directions on the module to open the top
4. Carefully unscrew the vial
5. Leave the top of the turbidimeter vial in a careful place (facing up) while cleaning the vial
6. Rinse out the vial and fill it with clean water
7. Screw the vial back onto the top
8. Wipe the outside of the vial with a Kimwipe to remove all fingerprints and other blemishes
9. Place the top back into the module and into the lock position, unscrew the plastic stoppers on the tubing and turn the turbidimeter on