MBBR

MBBR, or Moving Bed Biofilm Reactor, is a biological wastewater treatment process that uses plastic carrier media suspended in an aerated or mixed reactor to support a biofilm. Microorganisms attach to the carrier surfaces, forming biofilms that degrade organic matter and remove nutrients. The media are kept in motion by aeration and mixing, which enhances contact between wastewater and biofilm and helps retain biomass within the reactor. The system can operate as a standalone treatment or as a stage within a broader treatment line, and it is commonly used for BOD removal and nitrification, with potential denitrification occurring within the biofilm or in an adjacent anoxic zone.

Carriers are typically plastic shapes with high surface area to volume, such as beads or fins. They occupy a portion of the reactor volume, defined as the carrier fill fraction, to retain a high biomass concentration while maintaining adequate fluid flow. The moving media reduce the risk of biomass washout and enable shorter hydraulic retention times and greater resilience to loading variations.

Advantages of MBBR include a compact footprint, high biomass retention, flexibility for retrofitting existing plants, and robust performance under variable loads. It can be operated as a standalone process or integrated as a stage in a multi-step treatment system. Limitations involve higher initial capital costs for carrier media, potential issues with biofilm detachment or uneven media distribution, and the need for reliable aeration to keep the media in motion.

Applications cover municipal wastewater and various industrial effluents, where MBBR can function as secondary treatment, a polishing stage, or as part of a modular treatment train. History-wise, the approach emerged in the 1990s, with early media such as Kaldnes K1 contributing to widespread adoption. See also biofilm reactors and integrated fixed-film activated sludge systems.