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MBBR Media Types

The main carrier families used in moving bed biofilm reactors and how their geometry shapes performance.

MBBR media are small, buoyant plastic carriers that provide a protected surface for biofilm to grow. Over the years several generations have emerged — differing mainly in shape, size and the amount of protected internal surface they offer per cubic metre. The right type depends on the treatment target, the loading and the reactor geometry.

Handful of clean cylindrical MBBR biofilm carriers with internal cross-walls and external fins, showing the wheel-type geometry used in moving bed biofilm reactors
Classic wheel-type MBBR carriers: the cylindrical body, internal cross-partitions and external longitudinal fins provide protected internal surface area for biofilm while keeping the media easy to fluidise.

The main carrier families

Classic wheel / cylinder carriers feature a cylindrical body with internal cross-walls and external longitudinal fins. They are robust, well understood and mix easily. High-surface-area carriers use finer internal lattices to pack more protected area into the same volume, which can reduce reactor size for surface-limited processes such as nitrification. Saddle and chip-type carriers use flatter geometries to expose a large area while remaining easy to fluidise.

No single geometry is universally best. Higher internal surface area is only useful if the biofilm inside stays thin, well-oxygenated and free of clogging — which is why carrier selection is always a balance between surface area, self-cleaning behaviour and the specific pollutant being treated.

How the generations differ

The figures below are indicative literature ranges to illustrate the differences between families. Actual carrier data must be taken from the manufacturer's datasheet and confirmed per project.

Indicative carrier families (confirm per project)

ParameterTypical ValueUnitNotes
Classic wheel / cylinderModeratesurface areaRobust, easy to fluidise, widely referenced.
High-surface-area latticeHighersurface areaMore protected area per m³; needs good mixing to stay clean.
Saddle / chip typeVariablesurface areaFlatter geometry, large exposed area.
Selection driverProcess target—Nitrification favours high protected area; carbon removal is more forgiving.

Frequently Asked Questions

Which MBBR media type is best?
There is no single best type. Surface-limited processes such as nitrification benefit from high protected surface area, while high-load carbon removal is more forgiving and often uses robust classic carriers. The best choice balances surface area, self-cleaning behaviour and the treatment target.
Can I mix different carrier types in one reactor?
It is generally avoided within a single reactor because different carriers have different densities and fluidisation behaviour, which can lead to uneven mixing and separation. Different stages of a plant can, however, use different carriers suited to each stage.
Does a higher surface area always mean better performance?
No. Extra internal surface only helps if the biofilm there stays thin and well-oxygenated. If pores clog or oxygen cannot penetrate, the theoretical area is not used. This is why protected surface area and self-cleaning behaviour matter more than the nominal figure.

Related Pages

Specific Surface Area

How total surface area per m³ is defined.

Protected Surface Area

The effective area that actually drives design.

Carrier Shape

How geometry affects area and mixing.

How to Select MBBR Media

A step-by-step selection methodology.

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