Application of image analysis to evaluate the flocculation process

We report a study of how better to evaluate the flocculation process, comparing the image-analyzing method with the turbidity measurement method from a series of jar tests. The size and shape of flocs were measured over a range of velocity gradients (G) and flocculation times (t). Several advantages of image analysis over the traditional turbidity measurement method were found. Two parameters developed from image analysis, the Feret Diameter (FD) and the Shape Factor (SF), gave direct information about the characteristics of floc particles whereas turbidity measurement gave only indirect information about the supernatant instead of about the particle itself. The results of image analysis can be obtained in real time whereas turbidity required 30 min of sedimentation time. Image analysis can be used to suggest and evaluate optimum conditions for subsequent processes, such as sedimentation, flotation, membrane and direct filtration, whereas turbidity measurements cannot.