Mechanisms of Fouling in Fine‐Pore Diffuser Aeration

Abstract

Diffuser fouling is classified as one of three types, A, B, and C, based on the nature of the foulant. The accumulation of inorganic foulants, such as fine particles and precipitates, characterize type A fouling, and the formation of biomass‐characterize type B fouling. Type C fouling is characterized by the formation of biofilm, fortified by the entrapment of inorganic particles within the biomass. Hypotheses were developed to describe the mechanisms of dynamic change in diffuser operating performance as a result of the three different types of diffuser fouling. The hypotheses specific to each type were evaluated by testing the appropriate hypothetical equations using the data produced in this study. Results indicate that the physical properties of the biofilm are important factors in fouling, causing a significant change in diffuser characteristics. Entrapment of inorganic particles, such as sands, within the biofilm, significantly increase the dynamic wet pressure (DWP) and alter the bubble size. The association between DWP and bubble size could be quantitatively described by a hypothetical fouling equation for the three different types of fouling in these laboratory studies.