Understanding the Interplay Between Fluid Mechanics and Particle Size Distributions for Filtration of Flocculated Mixtures

The breakdown of nutrients in biological processes in wastewater treatment require a sub- stantial amount of energy, contributing to greater greenhouse gas (GHG) emissions. Floc- culation can be used to reduce the loading on a biological process by increasing removals during primary treatment in devices such as a rotating belt filter (RBF). The relationship between shear conditions, defined by velocity gradients (G-values) and floc size is crucial. Understanding G-value magnitudes and distributions within an RBF, corresponding trans- port network, and the effects on floc size degradation are needed to maximize removals. G-values were calculated using a newly developed approach, improving accuracy com- pared to traditional expressions. Floc strength was quantified at calculated G-value ranges, where flocs were found to resist breakage as G-values increased. The effects of varying PSD on RBF modelling constants were explored, where a strong response to PSD size fractions at or above the nominal pore size of the filter was found