Moving Bed Biofilm Reactor (MBBR)
The Moving Bed Biofilm Reactor process was developed in the late 1980s.
This process is used to remove organics, nitrification and denitrification. The MBBR system consists of an activated sludge aeration system in which the sludge is recycled and collected in plastic carriers. These carriers with a large internal surface are optimized for contact with water, air and bacteria.
Bacteria / activated sludge grow on the inner surface of carriers. Bacteria break down the organics in the wastewater. Excess sludge is removed from the carriers and flows with the treated water to the final separator.
Depending on specific applications, this system can operate as a single or multi-stage system.
MBBR can be operated as a two-phase (anaerobic) or three-phase (aerobic) system with free plastic biofilm carriers. These systems can be used for treatment of municipal and industrial wastewater, aquaculture and denitrification of drinking water. The system includes a submerged biofilm reactor and a liquid-solid separation unit.
The main characteristic of Moving bed Biological Reactor (MBBR) configuration is that there is no sludge recycles from secondary clarifier, MBBR is essentially simple, once-through process, where all of the biological activity takes place on the biomass carriers. MBBR is usually followed by a solids separation system such as a secondary clarifier or DAF, in order to separate bio-solids produced in the process from the final effluent. The main advantage of MBBR is robust and simple reduction of soluble pollutants (soluble BOD or COD, NH4 +，etc.), with minimal process complexity, utilizing a significantly smaller footprint when compared to conventional aerobic treatment methods. MBBR is typically used for either high load industrial applications or for robust simple-to-operate municipal facilities.
Key MBBR Design Parameters
• Organic surface loading rate (g BOD/m2d) Normal rate: 10 – 13 g BOD 5/m 2d @25 o C
• Protected surface area of carrier (m2/m3)
• The Biomedia carrier filling fraction (%) Normally: 50 – 67 % (minimum 30%)
Operational parameters for MBBR system design:
Media specifications for the MBBR System:
• Its specific gravity is less than water; about 30.36 gr/cm3
• The media material can be polyethylene, polyurethane and other high-density plastics.
The MBBR process involves aerobic and anaerobic reactors:
1. MBBR Aerobic Reactor:
In aerobic aeration, the media is fully agitated and mixed with water; meanwhile the air is segmented into small bubbles, which increases the contact area between biological membrane ne and oxygen, it also could increases the efficiency of oxygen transfer
2. MBBR Anaerobic Reactor
Under anaerobic conditions, water flow and media be fully agitated by agitator, in order to let the biofilm and the pollutants are fully exposed, and achieve the purpose of biological decomposition
The advantages of the MBBR process include:
• Although treatment purposes similar to activated sludge systems involve carbon oxidation and denitrification but require less tank volume than the activated sludge system with clarifier.
• Biomass retention is independent of the clarifier, and the solids loading in the solid separation unit is significantly reduced compared to activated sludge systems.
• MBBR is a continuous process and does not require a special operating cycle for biofilm thickness.
• Liquid solids separation can be achieved by a variety of processes including conventional and high speed compression processes.
• Self-regulated biomass.
• Flexible design that increases capacity.
• No operating settings, only maintenance of equipment
• Stable under high load changes.
• Low investment cost.
• Multiple applications
• Compact and simple biological treatment system.
The disadvantages of the MBBR process include:
• The quality of the outlet water depends on the ability of the activated sludge to settle and the size of the tank.
• Outlet water quality may not be sustainable because it depends on various factors such as temperature, MLSS concentration, organic load, etc.
• Needs disinfection with chemicals
Comparison of MBBR process with the other processes: