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Figure 1. Experimental apparatus
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.