Engineering Optimization of Filler Media for Vertical Moving Bed Biofilm Reactors: Material, Geometry, Size and Filling Fraction Selection for Process Intensification

Abstract

Moving Bed Biofilm Reactor (MBBR) technology has emerged as a robust and spatially efficient alternative to conventional suspended growth systems for decentralized wastewater treatment. The performance of MBBRs is strongly governed by the physicochemical characteristics of the carrier media, including material composition, geometry, size, density, and filling fraction. In vertical reactor configurations, where hydraulic gradients and aeration patterns differ significantly from horizontal systems, media selection becomes even more critical. The present study develops a conceptual design framework for optimizing filler media in vertical MBBRs to achieve process intensification, improved oxygen transfer, enhanced biofilm stability, and reduced reactor footprint. The framework integrates biofilm kinetics, hydrodynamic modeling principles, oxygen mass transfer theory, and lifecycle sustainability considerations. It is demonstrated that optimized cross-rib polymeric carriers at 70% filling fraction can increase COD removal from approximately 78% to above 91%, while reducing total reactor volume by 20–30% compared to conventional decentralized systems. The study establishes media engineering as a primary design variable in compact wastewater treatment infrastructure.