Is additional fluid shear effective in removing coagulant stuck to the wall of the flocculator?

[Kanha-Matai]

To test whether additional fluid shear can remove coagulant stuck to the wall of the flocculator, we implemented a syringe into our experimental apparatus. With this syringe we injected 100ml of water at approximately 3.5 secs. Our results (see graph below) showed that injecting this amount of water removed all pressure build up in the flocculator. We were first able to reduce pressure build up from 150 cm to 80 cm ( as shown in the graph below).

After the pressure stabilizes at 80 cm, we determined that the syringe injection did not alter this stabilization (pressure remained at 80cm). These observations are shown in the ProCODA screenshot below.

[Roswell-Lo]

We replicated the experiment with similar results. We tried using injecting the 100 ml in the syringe in twice the time (ended up doing it in 10.5 seconds). The pressure dropped from 140 cm to 80 cm.

We would like to demonstrate the experiment for Tanvi/Monroe on Tuesday.

Our next steps would be

• finding a way to consistently introduce shear
• finding minimum shear needed to knock of coagulant.
• finding way to automate injection.

[monroews]

A big goal is to reduce how much water is being used to clean the nanoparticles off of the tubing. Presumably if 100 mL works in 10.5 seconds, then you should be able to replicate that exact shear level with 10 mL in 1.05 seconds. The only problem with using less water is that you must ensure that the injected volume doesn't just flow into the accumulator.

The reason why we don't want such a large injection (100 mL) is because it will displace much of the flocculator volume and cause a deterioration in performance during the flush. Thus a much smaller volume would be much preferred.

[monroews]

Did you try removing the coagulant by increasing the pump flow rate? You succeeded in removing the coagulant with a flow of about 10 mL/s AND it is possible that lower flow rates would work too. This suggests that the peristaltic pump might be able to do this for us.

[monroews]

Note that the Excel graph x axis is incorrect and it isn't clear when the pulse occurred because there was no corresponding pressure spike. It would be helpful to indicate on the graph when the high flow occurred.