Moving Bed Biofilm Reactor (MBBR) vs. Bead Filters for Wastewater Treatment

Bead Filters and MBBR (Moving Bed Biofilm Reactor) are both biological wastewater treatment systems that use microorganisms to remove pollutants from water. The MBBR and the Bead Filter are both plastic floating media biofilters that can eliminate soluble Biological Oxygen Demand (BOD) from the system. However, they have different advantages and disadvantages.

MBBR Filter

RCPG Filter

MBBR systems use a moving bed of support material, such as plastic carriers or granular activated carbon, to grow microorganisms. The support material is constantly moving, which helps to keep the microorganisms active and prevents them from clogging the system. MBBR systems are very efficient at removing pollutants, and they can also be used to treat a wide variety of wastewater types. The MBBR focuses on the oxidation of soluble BOD and ammonia by aerating a bed of media used to grow biofilm, with no specific solids removal capacity. MBBR systems can be more difficult to operate and maintain than bead filters.

Bead Filters use a bed of beads, such as plastic or ceramic, to provide a surface for microorganisms to grow on. The bead filter forces the floating media against a screened outlet to form a static bed which gives them the ability to capture solids. Periodic backwashing is used to oxidize soluble BOD, ammonia and remove accumulated solids while constantly growing and abrading biofilm. Backwashing also provides aeration and breaks up the media preventing excessive head loss and improving the biofiltration rates. Bead Filters are less expensive and easier to operate than other biological wastewater treatment systems.

Both types of filters can operate with highly equivalent results as biofilters with the Bead Filter also providing solids capture, acting as a bio clarifier.

MBBR (Moving Bed Biofilm Reactor):

  • Filtration Mechanism: MBBR systems rely on a combination of physical filtration and biological treatment. They use plastic media with a large surface area to support the growth of biofilm, which helps break down organic matter in wastewater.
  • Treatment Efficiency: MBBR systems are highly efficient in removing both organic pollutants and ammonia from wastewater. The biofilm that develops on the media provides an effective surface for beneficial bacteria to attach and treat the wastewater.
  • Biological Treatment: MBBR systems are primarily designed for biological treatment. They are excellent at reducing organic contaminants and nitrogen compounds (like ammonia) through nitrification and denitrification processes.
  • Footprint: MBBR systems are compact and have similar space requirements compared to bead filters for similar treatment capacities. Solids removal requires an extra step, or footprint, in the treatment train.
  • Maintenance: MBBR systems require regular monitoring and maintenance to ensure optimal biological activity. This may involve media cleaning, occasional media replacement, and monitoring and cleaning of the coarse bubble diffuser aeration system.

Bead Filters:

  • Filtration Mechanism: AST Bead filters operate through biological and physical filtration. The use of proprietary small plastic beads as a filter media which in combination create a large surface area support the growth of biofilm, which helps break down organic matter in wastewater. This bead media will simultaneously capture and remove suspended solids from wastewater.
  • Treatment Efficiency: AST bead filters are effective at removing organic pollutants, ammonia, and suspended solids. AST bead filters provide high-efficiency biological treatment and solids removal.
  • Biological Treatment: Non-AST bead filters can support some biological activity on the surface of the beads, their primary function is mechanical filtration. Unlike other bead filters, AST filters* are as efficient as MBBR in terms of biological treatment. They are excellent at reducing organic contaminants and nitrogen compounds (like ammonia) through nitrification and denitrification processes.
  • Footprint: Bead filters require similar space compared to MBBR systems for equivalent treatment capacity. AST bead filters offer the ability to consolidate the footprint of the overall treatment train with its solid’s removal capabilities.
  • Maintenance: Maintenance of bead filters is relatively simple, involving periodic backwashing to clean the filter media and allow sludge to settle.  AST filter features automatic sludge removal.

*The AST bead filter has been used for nitrification and solids capture and are available in several distinct designs. The design that is a strong alternative to MBBR is the Recirculating PolyGeyser ( RCPG ) family of filters.

Here is a comparison table between bead filters and Moving Bed Biofilm Reactors (MBBR) in wastewater treatment:

In summary, the choice between bead filters and MBBR depends on the specific wastewater treatment needs of a given application:

  • If you need primarily mechanical filtration with some basic biological treatment, bead filters may be suitable and less expensive.
  • If you require efficient biological treatment, especially for the removal of organic matter and nitrogen compounds, MBBR and AST Bead Filters are a more effective choice.
  • MBBR systems were generally favored in the past. Today both AST bead filters and MBBR are both excellent choices; for their compact footprint and high treatment efficiency, especially in situations where space is limited or where stringent effluent quality standards must be met.

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