Tube Floc

Tube Flocculator

Introduction

Water turbidity is caused by colloidal particles in suspension (and the presence of natural organic matter and other organic and inorganic contaminants). These colloidal particles are too small to settle, and due to their negatively charged surfaces, they electrostatically repel each other. Flocculation transforms these repelling colloidal particles to attract and form into flocs that are large enough to settle out in the sedimentation tank. The probability (collision potential) that particles collide in a flocculator depends on the energy dissipation rate and residence time in the flocculator. As flocs collide, they grow in size making it easier to remove them in subsequent processes. 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 velocity. Therefore, it is important to research the parameters that affect flocculation and the resulting floc size distribution.
Conventional design guidelines for a hydraulic flocculator are incomplete, and the dynamics of how physical parameters affect flocculation are not well understood. The goal of the Tube Floc Team is to determine the parameters (such as optimal energy dissipation rate, hydraulic residence time, etc.) that will produce quickly settling flocs that can remove the greatest percentage of the turbidity for a variety of influent water qualities and provide better guidelines in designing a flocculation system.

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 the FReTA setup 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|^Ian Tse MS Thesis.doc]. This thesis contains detailed information on the [Process Controller] states, rules, and set points as well as descriptions of the data analysis process.

Current Research

Chemical Dosage Jar Test

We use the jar test to find the optimal dosage of PACl and Na2CO3, which controls the chemical stock concentration when running the tube flocculator apparatus. The Na2CO3 is used to control the pH of the water because we need to maintain the pH at 7.5 throughout each experiment.

Ion Effect on Flocculation

The current research showed a tap water with high ionic strength could perform quite well in flocculation, while the distill water with very low ionic strength could hardly form flocculator. We use the simulated tap water (by adding different known chemicals) to figure out which group of ion plays the key role in a good flocculation.

Challenges for Future Semesters

• Currently, we have figured out ionic strength and hardness could affect the flocculation performance, but we cannot tell which group of ions really work, and/or how they influenced the performance.
• Special Skills Needed: 
  • CEE 4540: This course could provide a fundamental understanding about municipal drinking water treatment.
  • MathCAD: We use this software to do the calculation for the research.
  • Lyx: This software is helpful when writing a scientific report.

More Information

Fall 2011 Research

Fall 2010 Research