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Basics on Tube Flocculator
(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?
" is the name given to the colloidal aggregates formed during the process of coagulation and flocculation. Small, micron sized particles of dirt and other organic matter exist naturally in rivers and other surface water sources. When there is a high concentration of these suspended particles in the water (as is the case after a storm), the water will look very cloudy and unpleasant to drink. It takes a very very long time (really long if the fluid is not quiescent!) for these suspended particles to settle out. By mixing a coagulant like alum into the water, these suspended particles will begin to stick to one another upon collision. Flocculation is the process of bringing these ever growing aggregates together to form even bigger aggregates which we call flocs.
What is Tube Flocculator?
The tube flocculator consists of many segments of plastic tubing joined together into one long coiled unit that is capable to producing flocs. Velocity gradients established by flow in the tube facilitate particle collisions. The tube flocculator allows the team to study how various parameters affect flocculation in laminar flowThe 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 connections are 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
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Amount of water (L)
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Amount stock added (g)
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Stock concentration (g/L)
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Clay
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11
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22.2
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2.02
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Alum
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11
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16.5
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1.5
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Humic acid1
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0.375
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1 Humic acid is added to the clay stock solution
Checklist for
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Process Controller
The details on Process Controller can be viewed here. Before running an experiment, make sure:
- Check the source page
- Check the location of datalog path
- If a new set point has been added in the set point list (and not at the end of the list), check that all rules and states still are referencing the correct set point, and any variable set points are referencing the correct set point too.
Troubleshooting
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- 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.
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- Turn the Process Controller to the OFF state
- Prepare a small piece of sponge (cleaning sponge) by the size of tube inner diameter by cutting the sponge with scissors
- Insert the piece of sponge at the starting point of the tube flocculator (right at the beginning of the clear flocculator tube)
- Press the pressure bottle (200kPa) to move the sponge in
- Turn the Process Controller ON (State 1 - Clean Flocculator7 - Calibrate Influent Turbidity)
- The piece of sponge will move through the flocculator tubing, cleaning the sides of the tubes of any flocs as it moves
- Turn the Process Controller OFF when it almost reaches the end of tube
- Clean out the sponge and repeat if the flocculator tubing is excessively dirty
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The clay and alum stock solutions can get old after no experiments have been running for quite some time. Because of processes like evaporation that we can not control, we can never be sure that the concentrations in the stocks are the same as we made them. If an experiment is going to be started after a long time from the last experiment, than then the stocks should be remade in order to make sure that all parameters are the same across all experiments.
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