Vicki Chou's Individual Contribution Page

Laminar Tube Floc Team

Spring 2014 Semester Contributions

Semester Goals:

The team's goals this semester include designing and setting up a new settled water turbidity (SWaT) measurement system to replace the flocculator residucal turbidity analyzer (FReTA) system. Once the SWaT system is properly installed and running, we will repeat clamp tests that we had performed last semester to compare the performance results of the two different systems. Once these experiments are analyzed, we will decide what experiments will best help us progress in understanding the consequences of floc breakup.

Progress:

Fall 2013 Semester Contributions

Semester Goals:

The Laminar Tube Floc Team is extending the work of previous semesters testing the hypothesis that "large flocs are useless." To do so, we are first testing a base case as a control experiment. The setup of the laminar tube flocculator is a series of three coiled tube arrangements (83m long). Our experiments will consist of testing the effects different sized clamps and different numbers of clamps on the middle tube arrangement have on floc breakup and residual turbidity. The results from our experiments will be used to further understand floc breakup and how to better improve the laminar flocculation system.

Progress:

The team ran three base case experiments. One with PACl dosages of 0, 5-10 mg/L (increments of 1 mg/L) and two with PACl dosages according to the power law: PACl dosage = coefficient x base^maxreps (where coefficient = .25, base = 1.25, and maxreps = 10)

Preliminary results from the base case described above suggest that a PACl dose of 2 mg/L is sufficient in achieving the desired mean residual turbidity because  PACl doses above 2 mg/L yield similar results for residual turbidity of around 1 NTU (+/- .5 NTU) for the effluent.

Using this dosage range, we conducted another base case with dosages of 0, .8, and 1.8 mg/L of PACl. We then began one clamp tests, where we placed one clamp in the middle of the tubing arrangement. The purpose of the clamp is to breakup flocs by increasing the energy dissipation rate where the clamp is located. Clamp sizes of 4 and 5 mm were tested. These two sizes were chosen from the results of the summer research, where they found 4 and 5 mm clamps showed significant floc breakup.

The results of our one clamp testing has shown that a 4 mm clamp significantly increases residual turbidity and a 5 mm clamp decreases the residual turbidity, as compared with the base case, where no clamp was used.  Our results suggest that perhaps a 4 mm clamp breaks up flocs too much, to a point where they cannot fully recover and collect more colloids. The results for the 5mm clamp testing showed no significant difference from the base case with no clamp. The results from our one clamp testing suggest that floc breakup may actually decrease flocculator performance, but more testing should be done with larger clamp sizes to test our theory about the 4 mm clamps breaking up the flocs too much.

Our progress was greatly hindered by challenges with malfunctioning equipment and software errors. The pump for the synthetic raw water was replaced, the code in Mathcad was edited, and various changes have been made in Process Controller to fix the problems we have encountered.