Floc Analysis: A Comparison between two Techniques

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Abstract

The characterization of flocculation rates is often done through floc size distribution over time. This distribution in size also affects settling rates. Besides sizes, settling velocities are dependent on floc density. This density is estimated using Stokes law, by recording the velocity and equivalent radius of a settling particle. This work compares two experimental setups used to calculate the floc size distribution and their settling velocities. The two floc measurement instruments as shown in figure 1, one is called LabSFLOC-2 [1,2] and the other is referred to as FLOCCAM [3]. Both setups have a telecentric lens which effectively reduces the pixel distortion. Polystyrene particles are used to benchmark the results. Different clay types are used to create flocs with the addition of industrial flocculant zetag 4110. The post-processing of the recorded floc videos for size, settling velocities and shapes of flocs is done with the help of an image analysis tool based on Matlab for LabSFLOC-2, whereas FLOCCAM analysis is done with the help of Safas [4].