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Rheology Results for Sludge & Polymer
Brought to you by Albert Chang and Sheena Vince Cruz
Introduction
n King Country Waste Water South Treatment Plant is using more polymer than they want to and still not getting the separation efficiency desired.
n It has been speculated that given the high viscosity of the fluids, significant mixing is required to cause proper flocculation
n Maxing out on the presently installed Sharpe Mixer is still not producing the desired mixing results.
n Understanding flow and mixing properties of these unusual low index fluids will help solve the problem
Objectives
n The overall class objective is to model the flow and mixing of the polymer and sludge under various situations
n Experimentally determine fluid behavior of the two fluids and various mixtures thereof
Experimental Set Up
n Two cups of digested sludge and polymer (Ciba Zetag 8819) samples were obtained on site
n Transported to Sharpe Mixer Labs for Viscosity testing with a Brookfield DVII+ viscometer
n Different spindles were used for various viscosity ranges
Expectations and Analysis
bθκη =
Curve fits can quantify the behavior of this fluid which is known to have power law properties. Power law fluids are governed by the following equations:
& θη loglog ba +=
Viscosity of Digested Sludge
Digested Sludge Behavior
y = -0.749x + 3.3461R2 = 0.9818
2
2.5
3
3.5
4
4.5
-1.5 -1 -0.5 0 0.5 1 1.5
Log (Shear Rate)
Lo
g (
Vis
co
sit
y)
Viscosity Vs. Shear Rate
y = 2218.6x-0.749
R2 = 0.9818
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
20000
0 2 4 6 8 10 12 14
Shear Rate
Vis
cosi
ty
Viscosity of Polymer
Viscosity vs. Shear Rate
y = 2043.1x -0.7412
R2 = 0.9968
0
500
1000
1500
2000
2500
3000
3500
4000
4500
0 5 10 15 20 25
Shear Rate
Vis
co
sit
y
Polymer Behavior
y = -0.6808x + 3.2745R2 = 0.9795
2
2.2
2.4
2.6
2.8
3
3.2
3.4
3.6
3.8
4
4.2
-1.5 -1 -0.5 0 0.5 1 1.5
Log (Sheer Rate)
Lo
g (
Vis
cosi
ty)
Mixture of Sludge and Polymer n Recipe: 46 ml of polymer
per 235 ml sludge n Vigorous mixing produces
flocculation and coagulation
n Unable to measure viscosity of anything that’s not continuous because water forms a liquid bearing around coagulated solids
Observations
n Produced jello-like chunks in relatively clear liquid water
n Prolonged mixing produces chunks of smaller sizes and ultimately over-mixing reduces mixture back into a continuous fluid
Viscosity of Over-mixed Sludge
Combined Overmixed Behavior
y = -0.994x + 3.2054R2 = 0.9814
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
-1 -0.5 0 0.5 1 1.5
Log Shear Rate
Log
Vis
cosi
ty
50% polymer strength
50% Polymer Over-Mixed
y = -0.8278x + 3.5775R2 = 0.9991
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
-1.5 -1 -0.5 0 0.5 1 1.5
Log Shear Rate
Log
Visc
osity
75% polymer strength
75% Polymer Solution Over-Mixed
y = -0.806x + 3.3675R2 = 0.9952
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
-1.5 -1 -0.5 0 0.5 1 1.5
Log Shear Rate
Log
Vis
cosi
ty
Conclusions
n All solutions are strongly non-Newtonian, shear thinning, power law fluids
n Both the polymer and the sludge have very low power indexes (table)
n Viscosity data is crucial to FEMLAB modeling of flow and mixing situations
Solution Power law index Polymer 0.319 Sludge 0.251
Over-Mixed 0.055