Understanding the Moving Bed Biofilm Reactor

Understanding the Moving Bed Biofilm Reactor(MBBR)
The Moving Bed Biofilm Reactor(MBBR)is a highly efficient hybrid system bridging the activated sludge process and fixed biofilm technology.

The reactor is equipped with high-specific-surface-area carriers that move freely within the water through mechanical agitation. As wastewater flows continuously through the reactor containing these mobile carriers,biofilms develop on the carrier surfaces.
Within these biofilms, microorganisms proliferate extensively, with heterotrophic and autotrophic microbes utilizing carbon(C), nitrogen(N), and phosphorus(P)in the wastewater for metabolic processes, thereby achieving pollutant removal and water purification.

The MBBR media addresses the limitations of conventional systems such as:
- Fixed-bed reactors, which require periodic backwashing;
- Fluidized bed reactors, which necessitate carrier fluidization;
- Submerged biological filters, which are prone to clogging and require media cleaning and aerator replacement.
Simultaneously, the MBBR retains the inherent advantages of traditional biofilm processes, including:
- High resistance to shock loads (organic, hydraulic, or toxic);
- Reduced sludge production;
- Prolonged sludge retention time (SRT).
Compared to the activated sludge process, the extended SRT in MBBR systems enables the retention of a higher population of nitrifying bacteria (e.g., Nitrosomonas, Nitrobacter), thereby enhancing nitrogen removal efficiency through improved nitrification.

Core Mechanism:
As wastewater flows continuously through the reactor, biofilms colonize the surface of the high-specific-surface-area carriers. Microorganisms within these biofilms proliferate and metabolize organic pollutants via aerobic, anoxic, or anaerobic pathways, depending on operational conditions (e.g., dissolved oxygen levels). This substrate degradation occurs through enzymatic reactions and microbial assimilation, ultimately achieving organic matter mineralization, nutrient removal, and effluent purification.