On-line Particle Size Measurements in Secondary Clarifiers

Secondary clarification is a crucial unit process in wastewater treatment; the particulate biocatalysts are separated from the clean water by gravitation. Their gravitational settling is highly dependent on the particles’ properties such as size, density and permeability. Hence, floc aggregation and disaggregation are essential to consider in the evaluation of the clarifier efficiency. The focused beam reflectance method (FBRM) is one of the rare techniques able to measure in situ the particle size distribution. This paper introduces the technique and demonstrates its capabilities in clarifier evaluation; benefits and drawbacks are mentioned too. In order to observe significant changes in size distribution, measurements have been performed around the flocculator under both constant and dynamic inlet flow conditions. This research has to be seen as a first exploration of this promising