Wastewater treatment systems using biofilms that grow attached to a support media can be either an alternative or an improvement to the widely used suspended growth activated sludge process. When the system is operated with a single pass and without return sludge it is called FBBR (Fixed bed Biofilm
reactor) or MBBR (Moving bed bio reactor). Especially for industrial pretreatment FBBRs are a good and advantageous alternative to activated sludge processes. If the system is operated with return sludge it is called IFAS (Integrated Fixed- Film activated sludge). IFAS systems are an easy and effective way to upgrade an existing activated sludge process by increasing the sludge amount (MLSS) in the aeration basin by up to 50%.

AET provides engineering consultation and product solutions for FBBRs, MBBRs, IFAS systems and trickling filters.

attached growth system
attached growth system

Fields of application

  • BOD removal and complete nitrification
  • Upgrade of existing activated sludge processes
  • Pretreatment of industrial waste water
  • Smaller municipal WWTPs
  • High organic loadings or high content of compounds with low biodegradability

Examples: Food processing and beverages, Dairy, lagoon bypasses, chemical, leachate, Pharmaceutics, Energy, Pulp and Paper and more.

“Advantages of biofilm attached growth systems”

  • Easy and fast installation for existing tanks
  • Low energy consumption
    Higher performance through increasing sludge-age and active biomass
  • Improved sludge settling characteristics
  • High resistance against toxic or complex substances
  • No immediate impact of electric shutdowns
  • Low overall cost

Fill media for water and wastewater applications is used as a carrier medium for Bio-film growth. The fill media blocks consist of corrugated foils which can be manufactured in various forms. These various forms result in different surface areas and channel designs. Additionally, fill media blocks can be manufactured from either Polypropylene (PP) or Polyvinyl Chloride (PVC). Moreover, our customers benefit from a customized fill media solution for their individual project case.

Fixed-bed biofilm reactors use fill media with a vertical flow channel shape. The vertical channel shape facilitates an easy sludge discharge for high organic loadings. This is due to increased biomass growth in FBBR applications. Depending on our customer needs, we design the appropriate fill media which provides the maximum allowable surface area. This also ensures an even distribution of liquid and air for the best treatment results. To learn more, contact us through our inquiry form

Product Application Material Surface Ft2/ft3 Corrugation Height mm Continuous operating temperature
Vertical flowModerately to strongly polluted water
BOD removal nitrification
PP or PVC38 to 7012 to 23Up to 160°F(pp)
Up to 130°F (PCV)
Vertical flow Net structureStrongly polluted water
BOD removal and partial nitrification
PP or HDPE3025Uo to 160°F
Cross flowBarely to strongly polluted water
Water distribution BOD removal and nitrification
PP or PVC21 to 7012 to 38Up to 160°F (PP)
Up to 130°F (PVC)


Lagoon upgrade with FBBR, MS, USA
AET in cooperation with Jaeger- aeration provided a FBBR system (incl. piping and blower setup) as an upgrade for a lagoon treatment plant in Mississippi, USA. Part of the influent water is going through the FBBR side stream to fulfill BOD and ammonia permits.
Trickling filter air distribution system, NY, USA
To remove odors from a trickling filter plant an air distribution system was installed underneath the fill media during a retrofit project. The distribution system is evenly releasing air so that the odors are removed when passing the biofilm fill media. AET assisted with the design and calculations of the trickling filter air distribution system.

Articles & Literature

Attached Growth

Biological processes in wastewater treatment can be classified into two main categories: suspended growth and attached growth/ biofilm processes. In suspended growth processes the microorganisms responsible for wastewater treatment are maintained in liquid suspension by appropriate mixing and aeration…

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