Laminar Tube Flocculator
Ian Tse's M.S. Thesis on Fluid shear influences on hydraulic flocculation systems characterized using a newly developed method for quantitative analysis of flocculation performance
Site Map
- Tube Flocculator Past Research and Experimentation
- Tube Floc Settling Data Analysis
- New Setup for Spring 2008
- Miscellaneous
Objective and Motivations
Introduction
In the flocculation process, suspended particles collide with each other to coagulate and transform into larger flocs, with the help of a coagulant, The goal of any flocculation process is to transform suspended colloidal particles into flocs that can be removed by sedimentation. The design of sedimentation tanks is dictated by the To improve the performance of flocculators, we need to research how the design and operational parameters affect the aggregation and settling velocity of the flocs. Floc capture requires that the fluid residence time in a sedimentation tank or in plate or tube settlers be greater than the time required for the flocs to settle out. Therefore, one design goal of flocculators is to create flocs with sufficiently high sedimentation velocities. Unfortunately, guidelines for proper design and operation of hydraulic flocculators are incomplete. The appropriate energy dissipation rate required at different points along the flocculator that will produce the best flocs is not well understood. It is expected that high energy dissipation rates will initially enhance the collision frequency of small particles creating larger floc aggregates, however high energy dissipation rates are also likely to cause break up of large flocs.
In orthokinetic flocculation, differential velocities cause flocs to collide. A percentage of these collisions result in adhesion and the further growth of flocs. It has been shown that the frequency of collisions is related to the magnitude of the energy dissipation rate present during orthokinetic flocculation. As flocs grow larger, they become more susceptible to breakup. Thus, a continuum of energy dissipation rates affects floc growth and breakup in orthokinetic flocculation. Eventually the particle size distribution can reach a pseudo-steady state during which breakup balances aggregation (Spicer & Pratsinis, 1996).
Our goal is to determine the parameters (such as optimal energy dissipation rate, hydraulic residence time, etc.) that will produce fast settling flocs that can remove the greatest percentage of the turbidity in the water.
Previous Research
Our previous research prior to Fall 2009 includes the development of FReTA and the accompanying data analysis tools that are capable of capturing the settling velocity distribution and post-sedimentation residual turbidity of a flocculent suspension. FReTA was also used to explore fluid shear and hydraulic residence time influences on hydraulic flocculator performance.
Spring Semester 2008 Research Goals
The team has discussed and agreed on several important goals to focus on for the Spring semester 2008:
- Analyze the data from the Fall Semester 2007 and make solid conclusions. The team will look into further analytical tools such as Excel, MatLab, and MathCAD to handle and display the data in a better, more user friendly format. The team last semester found that the current MathCAD file is hard to use, for example if the user wants to isolate one run in a series of iterated experiments or compare certain runs to each other on the same graph.
- Develop models to describe what is happening in the flocculator. The team will use this to determine what parameters are important in regulating the flocculation process.
- Literature research to compare research, to see if previous similar experiments have been conducted, or for inspiration for further experiments or data analysis.
- Find the relationship between G and Gθ. This is the ultimate goal that the team is trying to determine, it will take a combination of data analyses, modeling, and maybe more experimentation.
Ongoing Research - Spring 2008
- Developing analytical methods for understanding flocculation/settling data from our tube flocculator apparatus
- Augmenting sampling frequency and accuracy of our nephthelometric turbidimeters by accessing raw voltages directly from sensor
- Reevaluating the efficacy of tube flocculator setup & designing methods to eliminate sedimentation within flocculator and maintaining quiescent conditions in the settling volume
- Determining settling velocity and floc concentration using PIV.
- Writing tutorials on Process Controller.
Future Research - Beyond Spring 2008
- Using PIV to evaluate floc formation from previous experiments: varying alum dose and varying G in flocculator
- Once the new IR turbidimeter is up and running, re-run previous experiments from last semester and compare settling curves
- Develop Process Controller Tutorial and exercises for future team members
Tube Floc Presentations
February 20, 2008
Our understandings on the tube floc research is summarized in the teach-in presentation.
March 25, 2008
Ken Brown's visit presentation
May 10, 2008
Final presentation
FAQs, Basics, and Cleaning
These parameters include energy dissipation rate, hydraulic residence time, coagulant dose, influent turbidity, etc. One of the goals for the AguaClara team is to develop a sedimentation tank that will form a fluidized floc blanket, which will help clean water as it flows into the sedimentation tank from the flocculator. To develop this floc blanket the flocculator must produce flocs that fall within a particular range of settling velocities. Our apparatus (flocculation residual turbidity analyzer or FReTA) is capable of measuring both settling velocity and residual turbidity under different flocculator operating conditions. Complete description and sketches of current apparatus setup can be found here.
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The goals of the Laminar Tube Floc Team are to determine the parameters that will affect influent turbidity removal and to develop flocculation models as a guideline for flocculation design. |
If you are new to the team or would like to know more about the upkeep of our experimental setup, check out the basics. An excellent resource for information on tube flocculator is Ian Tse's M.S. thesis: Fluid shear influences on hydraulic flocculation systems characterized using a newly developed method for quantitative analysis of flocculation performance. Detailed information on the ProCoDA Software as well as descriptions of the data analysis process can be found in the appendix of this M.S. thesis.
Ongoing Research
* Determine the optimal orifice size for floc break up systems with four, eight, and sixteen clamps by gradually decreasing the clamp size based on the relationships between energy dissipation rate, floc size, terminal velocity, and clamp size until the flocculator performance worsens.
- Determine optimal positioning for floc break up points by comparing the residual turbidity of an evenly distributed clamp system with clamp systems that gradually decrease the number of clamps toward one or both ends of the flocculator. As residual turbidity decreases the flocculator performance improves.
- Compare the performance of tapered tube flocculation with regular tube flocculation. Design a tapered system -- small tube at the beginning, medium tube in the middle, and large tube at the end (same length for each size of the tubing) using 10 mg/L PACl dose and 28 m tube flocculator length (N://files.Cornell.edu/EN/aguaclara/RESEARCH/Tube Floc/Spring 2013/Experiments/Single PACl 10 mgL.pcm/). As tube size (diameter) increases, energy dissipation rate decreases, allowing flocs to continue to grow. The larger that flocs can grow, the lower the residual turbidity will be.2. Determine optimal positioning for floc break up points by comparing the residual turbidity of an evenly distributed clamp system with clamp systems that gradually decrease the number of clamps toward one or both ends of the flocculator. As residual turbidity decreases the flocculator performance improves.
Current Research (Spring 2015)
* Design and implement a settled water turbidity (SWaT) measurement system that can more accurately measure low turbidities than the previous FReTA system. Using this new SWaT system, repeat experiments using only one clamp of variable size on the middle of the tubing arrangement. Compare the results of these experiments with the results of the same experiments run using the FReTA system from the Fall 2013 research.
* Depending on the results of the middle-clamp testing, either run more experiments with variable number of clamps to further test the effects of clamps, or design and implement a tapered flocculator system with energy dissipation rates starting from 1000 mW/kg.
Challenges for Future Semesters
- Special Skills Needed:
More Information
Troubleshooting of the apparatus, Process Controller and Data Processor.
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If you are new to the team or would like to know more about the upkeep of our experimental setup, check out the basics.