Tube Flocculator

Objective and Motivations

The turbidity of water is caused by colloidal particles in suspension (and the presence of natural organic matter and other organic and inorganic contaminants). Colloidal particles are too small to settle and due to their negatively charged surfaces, electrostatically repel each other. Flocculation transforms colloidal particles into larger flocs that can settle out in the sedimentation tank. The probability (collision potential) that particles collide in a flocculator depends on 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 velocities. 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 try to 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 for a variety of influent water qualities and provide better guidelines in designing a flocculation system.

The apparatus

Experimental apparatus

Research

*Influence of flocculator length and alum dosage on flocculation
*Fluid shear influences on flocculation
*Archive

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. 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. This thesis contains detailed information on the Process Controller states, rules, and set points as well as descriptions of the data analysis process.

References

Pratsinis, S., & Spicer, P. (1996). Shear-induced flocculation: the evolution of floc structure and the shape of the size distribution at steady state. Water Research, 30(5), 1049. Retrieved from Environment Index database.