Mathematical modeling analysis of Floating Bead Biofilter applications to domestic wastewater treatment

Abstract

Floating Bead Biofilters (FBFs) have been applied to aquacultural recirculating tanks and domestic wastewater treatment systems for controlling total ammonia nitrogen (TAN), biochemical oxygen demand (BOD), and total suspended solids (TSS). Support modified media in these FBFs provide a large surface area (1150~1475 m2/m3) so that the active biofilm can be retained in the FBF by attaching to the media surface. Understanding the theories involved in biofilm processes greatly helps in sizing, designing, and modeling of FBF systems. Fundamental biofilm processes like mass transport of various substrates into the biofilm and the substrate utilization within the biofilm were studied. A mathematical model (MSB Model) was set up to predict the development of the FBFs characteristics such as biofilm growth, substrates utilization, dissolved oxygen consumption, BOD loading removal, volumetric oxygen consumption rate by filter (OCF), and bead bed volume under the different conditions. This model was then calibrated with a set of bioclarification data. The model results were consistent with literature defining the relationships between dissolved oxygen consumption, BOD loading removal, and biofilm growth. This model is specifically used to predict design parameters for FBFs in a municipal sewage treatment systems. The entire study was based on the following experimental parameters: OCF, dissolved oxygen (DO), hydraulic loading, BOD loading, maximum ratio of BOD removal to OCF (MX-factor).