Floc Blanket Research

Motivation

AguaClara is committed to improving drinking water quality in Hondurasthrough the design and construction of gravity-driven water treatment plants. High concentrations of suspended and colloidal particles can increase the prevalence of pathogenic organisms, interfere with disinfection, and negatively impact drinking water quality.  The goal of the AguaClara project is to provide an average effluent turbidity of less than 1 NTU after sedimentation to achieve a high level of water treatment, thus, a crucial component of design is optimization of the sedimentation tank.

We have built a laboratory scale plant  to simulate a water treatment process sequence of rapid mix, flocculation, and sedimentation plate settlers to accomplish removal of colloidal particles. We hope to optimize performance of this plant to achieve an effluent turbidity after sedimentation of less than 1 NTU for a large range of turbidities.

A brief history of sedimentation in AguaClara

 La 34, the first plant designed by AguaClara, utilized horizontal sedimentation. The goal in design of horizontal sedimentation is to design a capture velocity of the tank (1) that is less than or equal to the terminal settling velocity (v_S) of the smallest particle size to be captured. We can approximate terminal settling velocity (v_t) based upon Stoke's law for a spherical particle.  

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                                                                                                               (1)       

Once a particle has settled, it may be resuspended if there is not relatively uniform, quiescent flow in the tank.  Inlet design is additionally important to ensure that flocculated particles are not broken up.

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