BIOSTYR Biologically Active Filter (BAF)

BIOSTYR® process combines biological treatment, and solids separation via filtration into one compact system. BIOSTYR® DUO (BAF + MBBR) adds a second media layer for increased carbon, solids and nitrogen loading capabilities. With over 160 installations throughout the world, BIOSTYR is proven to be an exceptional technology for BOD removal, nitrification, denitrification and solids removal, with improved energy efficiency and 20% of the footprint of conventional activated sludge technologies.

BIOSTYR Process for Innovative Biological Treatment

The BIOSTYR® process is a high-rate upflow submerged media biologically active filter (BAF).The process is carried out in a series of individual cells containing submerged buoyant media called BIOSTYRENE™. The incoming wastewater and air, both fed at the base of the cell, flow concurrently through the BIOSTYR cell. The BIOSTYRENE media provides a high specific surface area where microorganisms attach, treat the wastewater, and further enhance the filtration for suspended solids removal.The media is retained in the cells by a precast concrete nozzle deck integral to the structure.

BIOSTYR® Applications

Secondary Treatment

Following primary clarification, BIOSTYR is an optimal solution for the removal of BOD, suspended solids and ammonia. Typical effluent levels achieved are 10/10/1 (BOD, TSS, NH3-N). As a compact, fixed-film process. BIOSTYR offers more reliable treatment than activated sludge at low influent temperatures, and avoids the need for clarification. 


BIOSTYR can be used to expand existing secondary treatment processes to provide tertiary removal of ammonia while further polishing suspended solids. This is an ideal solution for existing pure oxygen plants or other activated sludge systems that provide limited or no nitrification. These facilities, when required to remove ammonia to meet new regulations or produce reuse water, can easily meet these new objectives by adding BIOSTYR at the end of the existing process.


BIOSTYR is an ideal choice for denite filter applications. It can be applied following any proceeding nitrification process, and offers denitrification to very low levels. Effluent Total Inorganic Nitrogen from BIOSTYR denitrification filters is typically < 1.5 mg/L. Due to the specific design of the BIOSTYRENE media, BIOSTYR denitrification filters operate at much higher loading rates than conventional, sand-based, denite filter technologies, and occupy a fraction of the footprint. 


  • Compact footprint; Ideal for constrained sites
  • Downstream clarifiers not necessary, decreasing operation and maintenance requirements
  • Treated water of exceptional quality, even in very cold climates
  • Footprint allows for process to be easily enclosed, neighborhood friendly
  • No periodic replenishment or replacement of media required, decreasing maintenance yearly costs
  • BIOSTYR cells do not require dedicated screening; Typical headworks screens only
  • Add on nitrification and/or denitrification in one process with minimal space required

BIOSTYR® DUO for Nutrient Removal

The BIOSTYR DUO system is a first-of-its-kind integration of Biological Aerated Filter (BAF) and Moving Bed Biofilm Reactor (MBBR) technologies. Biological treatment and filtration occur simultaneously within the system, and two separate media types are contained within the same treatment cell. Wastewater first flows through a dynamic MBBR media layer which provides a large surface area for biofilm growth and treatment. Flow then passes through the BIOSTYRENE media layer, which provides additional fixed film treatment and filtration as the water flows up through the fixed bed. The buoyant BIOSTYRENE media is retained by a concrete deck with multiple strainers, and the system uses a gravity driven backwash for excess solids removal with no pumping.

This innovative system offers significantly increased BOD and Ammonia loading rate capabilities compared to other BAF systems, while maintaining very low effluent BOD, TSS and Ammonia values.