Tube Flocculator
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 is the definitive document as of the summer of 2009 on tube flocculation and FReTA. Some of the child pages here appear to be out of date.
Site Map
Objective and Motivations
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 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.
Research Goals
The research goals for each semester are provided below:
Future Challenges
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.
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
If you are new to the team or would like to know more about the upkeep of our experimental setup, check out the basics.