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Task list

Introduction

For the first part of the semester (before the Spring 2011 break), the team will be working mainly on experiments and theory. The experiments are going to quantify the performance of variable tube diameter tubes diameters performances for different varying velocity gradients while keeping the capture velocity constant. We will try different sets of experimental setups, : presence or lack of a floc blanket in the sedimentation tank, with clay and maybe Natural Organic Matter (NOM). The theoretical part of the semester will be to

1. Explore the sensitivity of the Pi-ratio theory# to perturbations and
2. Develop the numerical dynamics model that was started previous semester.

The team will also prepare to publish the experimental results.

Throughout the semester, the team will be preparing to publish the experimental results. After collecting enough data the team will try to make draft design of small-scale sedimentation tank that will enable the PSS team to test close spacings to a greater scale.

Experiments

Team members: All active team members will help running experiments.
All the experiments will be run with a constant capture velocity of 0.10 mm/s. For each set of experiment, we will determine

• the tube effluent percent removal
• the tube effluent pC*
• the average tube effluent turbidity
• the tube and floc blanket effluent removal

We will compare the trends under different conditions in order to get a more complete understanding of possible failure mechanisms in the plate settlers.
Tubes inner diameter (ID) runs : 12.7 mm (1/2") 9.53 mm (3/8"), and 6.35 mm (1/4") with V.capture = 0.10 mm/s. The different experimental setups will be:

1. Clay Velocity Gradient Experiments with floc blanket and alum

• These experiments are experimental runs of past semester experiments for which the V.capture was not 0.10 mm/s
• We are planning to run the 3/8" and 1/4" tube at 3 different flow rates to get 3 different velocity gradients:
  Tube ID (mm) Flow rate 1 (mL/min) @ V.Gradient (1/s) Flow rate 2 (mL/min) @ V.Gradient (1/s) Flow rate 3 (mL/min) @ V.Gradient (1/s)
  6.35 1.9 @ 1.26 3.785 @ 2.51 9.486 @ 6.289
  9.53 4.278 @ 0.839 8.544 @ 1.676 21.343 @ 4.186

• We will also add three increasing velocity gradients on the ¼" ID tube to get a 6-points trend for more data in the range of really very high velocity gradients The team will design 3 extra ¼" ID diameter with very high velocity gradients but with V.capture=0.10 mm/s. The limit of the velocity gradient will be given by the maximum reasonable length of the tube, about 1.2 m. The tube lengths would be and 0.40 m, 1.429 m (6 ft minus 0.40 m), 1.829 m (6 ft).
• The team expects to see increasing decrease of performance in terms of percent-removal and pC* vs. velocity gradient.
• Sub total = 9 experiments

1. Clay Velocity Gradient Experiments without floc blanket and alum

• We will test all three selected tubes at the same flow rates as the #1. experiments to get comparable data with PSS fall 2010 experiments.

• The team expects to see an increase in effluent turbidity but a comparable pC*.

• SubTotal = 9 experiments (The 6 same runs as in set #1 and 2 more runs of ¼")

1. Clay Velocity Gradient Experiments with or without floc blanket and PAC (PolyAluminum Chloride)_

• Same runs as the "Clay Experiments without floc blanket and Alum". We will replace the Alum stock with the equivalent appropriate concentration of PAC as suggested in the guidelines..(this appropriate concentration will be determined later)

• We will see if the replacement of alum with PAC affects the results. If the performance results are comparable or better than with alum experiments, we will not carry further experiments.

• Subtotal <= 9 experiments

The total number of experiments will about 27 experiments. Each experiment takes approximately 1 day to run. We would need at most about 1 month and a half net of experiments. The experiments which are going to take most of the time will be the low flow rate experiments.

Data Analysis

Team members: Tanya and Cosme with the contributions of Karen Swetland (Fall 2010 Team Leader and member of the Flocculation Research team) and Michael Adelman (Stack Filtration Team)
The PSS Fall 2010 team experienced some setbacks due to wrong flow rates calculations. The flow rates used for the experiments did not always correspond to the V.capture of 0.10 mm/s. In addition, data analysis under Excel is a tedious process which requires many steps. Each of these steps can be automated. Furthermore, data analysis was done in Excel spreadsheets while calculations were done with MathCAD. This lead to discrepancies and resulted in non-comparable experiments. Therefore, the PSS team has decided to perform data analysis and calculations using MathCAD only. Aside from these issues, the comparison of performance from one experiment to another was set by comparing each run to a control case experiment. This created some confusion in the interpretation of the data.
The team will systematically recover statistics (i.e., average and standard deviation) about:

1. Raw water turbidity,

1. Floc blanket turbidity (Tube settler influent turbidity)

1. Tube effluent turbidity.

The team will recover the percent removal and pC* from 1., 2. and 3.

The team will cooperate with Karen Swetland and Michael Adelman to implement the data analysis in MathCAD. A log file (metadata file) containing information about each experiment will be used to log all the relevant information necessary for data analysis (e.g., dates of runs, tube ID, velocity gradients, results and comments).
This will be done the first week, before starting running experiments. But adjustments can be made throughout the semester to provide more information about the data.

Theory

Sensitivity of the PI ratio theorem
Team members (subject to slight changes): Adela, Ying, Cosme
Previous semester issues with the flow rates calculations also showed that the PI-ratio was sensitive to variations of flow rates. This sensitivity should be quantified in order to get an idea about the uncertainty of our experimental results. The calculations involves mainly algebra and MathCAD.
We expect to be able to have these theoretical results before the Spring break.
Dynamics model
Team members : Adela, Cosme, Richard
The PSS Fall 2010 team started to work on developing a numerical simulation of the plate settlers. The improvement of the current code (in Matlab) would help assess the possible effects of the presence of flocs in plate settlers.

1. Debug the current code so that it can give the same results as predicted by the pi ratio

1. Implement floc break-up and flocculation model

1. Look in literature about how to model the effect of flocs on the flow profile and implement this model into the code.
   We expect to achieve

1. 1 and 2 by before the spring break and 3# after the spring break.
   Design of a small-scale sedimentation tank for testing plate settlers spacing
   Team members: Adela, Ying, Ashleigh
   Based on understandings from the experimental results and theory the team will design a scaled version of the sedimentation tank with the optimal spacing. If time permitting, the small-scale facility will be constructed with the help from the CEE Machine Shop located in the basement of Hollister Hall. The design process is planned to start after the first research report. Hence, we expect the first draft design to be completed by April 8th.
   As part of the design we will calculate:

• Scaled dimensions/geometry of the sedimentation tank
• Amount of material needed
• Design constraints (pressure drop, flow uniformity, ...)

Paper

Team members: All team members
The team will compile the results from the relevant experiments to write a report. We will start writing the report after the first research report. The report will include:

• Theory: current knowledge review and detailed theory about failure
• Experiments: Analyzed data from the Fall 2010 and Spring 2011 experiments.