Biofiltration (BBF)

Biofiltration (BBF) system is a versatile biofiltration system that can be used as primary, secondary, and tertiary treatment. Its features combining physical filtration and biological treatment make BBF the smart choice for applications from large scale municipal wastewater treatment to high strength livestock wastewater.


How Biofiltration works

  1. Larger size particles are pre-filtered by the fixed media layer at the bottom of the reactor (A)
  2. Suspended solid and fine particles are filtered by the bio-film attached on the floating media (B)
  3. Organic matter and nitrogen are also removed by the microbes that form the bio-film (C)

Structure of Biofiltration

BBF employs physical and biological treatments using a single up-flow reactor

  • Wastewater travels down from the influent water way located on top of the BBF reactor, and it enters the reactor at the bottom of the structure
  • The hydraulic head difference creates an up-flow condition inside of the reactor and water first travels through the fixed media layer (anoxic zone) which is located at the bottom of the system
  • Floating media layer is located in the middle of the reactor and is retained by strainer block
  • Depending on the process air diffusers location relative to the floating media, oxic, anoxic, or oxic/anoxic conditions can be designed
  • The effluent waterway conveys treated water from the system and the remaining water on top of floating media is used as backwash water source without requiring pump

Concrete Type

  • Rectangular concrete structures
  • For large volume flow
  • Above ground or underground design

Vessel Type

  • Cylindrical vessels (dual or quad unit)
  • For small volume flow
  • Outdoor or indoor installation

Operational Mode of BBF

Operation Mode

  • Influent enters the BBF reactor from the top through the influent pipe and by gravity reaches the bottom and then flows upward through both media layers
  • Larger particles are filtered by the fixed media and the smaller particles, soluble pollutants and nutrients that pass through the fixed media layer are removed in the floating media’s biofilm
  • The treated water exits the reactor through the effluent waterway on top of the reactor
  • As the up-flow treatment process continues, headloss will be increased by the excess solid deposits

Backwashing Mode

  • Head loss is recovered by two backwash methods, gravity draining for sludge removal(fixed media) and air scouring for excess bio-mass removal (floating media)
  • Monitoring system (pressure gauge) triggers automatic backwash
  • During backwashing, the air scouring facilitates the removal of suspended solid and excess biomass from the media layer
  • Backwashing sludge drains through the backwashing channel
  • The treated water remaining over the upper strainer block will be used for backwashing driven by gravity

BBF's Materials and Equipment


  • The uniform sized fixed media material is made from ceramic materials and is available with 5~20 mm diameter
  • The floating media is an expanded poly propylene (EPP) material which provides the ideal surface area to build bio-film
Media Material Size Density
Fixed Ceramic 0.2"~0.8" >93.6 lb/ft3
Floating EPP 0.08"~0.3" >6.24 lb/ft3
Fixed media

Fixed media

Floating media

Floating media

Air Supply System

  • Consists of air diffusers and air supplier
  • Supplies air to create oxic zone in floating media
  • Provides air supply to scour excess biomass deposits off of the media surface

Strainer Block

  • Prevents loss of the floating and/or fixed media
  • Maintains uniform discharge flow
  • Air in the floating media escapes through the nozzles attached under the strainer block