Spring 2009 Turbidity Profiles
Methods
Two setups of baffle configurations were built this semester (four 6' lengths of baffles), meaning while one configuration (2 strings) is in the flocculator and being tested, the other configuration can have its spacing being altered. Having multiple setups means wasting less time rearranging a setup after it is taken out of the tank, effectively eliminating dead time. Since each setup also has different length spacers, flocculator configurations where one channel has a certain baffle spacing (b) while the other channel has a different b, echoing the current plant design, can be tested as well.
Polyaluminum chloride (PAC) is the coagulant of choice of the Cornell Water Treatment Plant as well as many other plants across the United States. According to plant workers PAC is much more forgiving than alum in terms of dosing and forms flocs better in colder water temperature, a shortfall of alum when testing in Ithaca. Dosing with PAC was set up at the Pilot Plant. Since our goal is to collect turbidity profiles of the tank based upon energy dissipation (the spacing of the baffles), by removing the added variable of determining the alum dosage by using the easier-to-dose PAC, the profiles will be more comparable in terms of effect of baffle spacing.
In previous testings, many data samplings needed to be collected in one sitting to avoid having large fluctuations in turbidity which required experimenting and determining new alum dosages and lent itself to data that could not be directly compared. To keep our results consistent and relevant to one another every day of experimentation will start with a turbidity profile for a "normalizing" configuration, a configuration with .102 m baffle spacing so profiles can be adjusted based upon the results of the normalizing setup.
Calculations
Length of flocculator channel = 1.8288 m
K baffle = 4
Π cell = 4
w = .305 m
h = .764 m
|
Q 50 = 50 L/min |
|
|
Q 100 = 100 L/min |
|
|
b (m) |
ε (mW/kg) |
N (#baffles/channel) |
θ channel (residence time/channel) (sec) |
ε (mW/kg) |
N (#baffles/channel) |
θ channel (residence time/channel) (sec) |
.051 |
1.507 |
34 |
484.9 |
12.06 |
34 |
242.4 |
.076 |
.306 |
23 |
488.8 |
2.445 |
23 |
244.4 |
.102 |
.094 |
16 |
456.3 |
.754 |
16 |
228.2 |
.127 |
.039 |
13 |
461.7 |
.314 |
13 |
230.8 |
.152 |
.019 |
11 |
467.5 |
0.153 |
11 |
233.8 |
.178 |
.01 |
9 |
448.0 |
0.081 |
9 |
224.0 |
.203 |
.006 |
8 |
454.1 |
0.048 |
8 |
227.1 |
Turbidity Profiles
Configuration |
1st channel |
2nd channel |
θ flocculator (s) at Q 50 |
θ flocculator (s) at Q 100 |
1 |
.051 m |
.051 m |
969.7 |
484.9 |
2 |
.076 m |
.076 m |
977.6 |
488.8 |
3 |
.102 m |
.102 m |
9127 |
456.3 |
4 |
.127 m |
.127 m |
923.3 |
461.7 |
5 |
.152 m |
.152 m |
935.1 |
467.5 |
6 |
.178 m |
.178 m |
895.9 |
448.0 |
7 |
.203 m |
.203 m |
908.2 |
454.1 |
8 |
.051 m |
.076 m |
973.7 |
486.9 |
9 |
.051 m |
.102 m |
941.2 |
470.6 |
10 |
.051 m |
.152 m |
952.4 |
476.2 |
11 |
.051 m |
.203 m |
939.0 |
469.5 |
12 |
.076 m |
.102 m |
945.1 |
472.6 |
13 |
.102 m |
.152 m |
923.9 |
461.94 |