Biofilm upgrade for activated sludge plants for added robustness and greater capacity

Hybas™ is the AnoxKaldnes Integrated Fixed Film Activated Sludge (IFAS) solution, requiring little process volume to achieve a reduction of organic material and nitrogen. This solution is a cost-effective way to upgrade an existing activated sludge system integrating nitrogen or full BNR removal or enhancing nitrogen removal capacity.

With Hybas™, MBBR carriers are strategically added to the whole or a part of the aerated activated sludge volume. High amounts of nitrifying bacteria are enriched on the carriers while BOD removal and denitrification occur in the suspended phase. This solution improves nitrification and reduces the sludge load on secondary clarifiers. Denitrification is also improved, as the sludge age in the activated sludge is reduced, and the risk of filamentous bacteria is reduced.

Although Hybas™ is commonly applied as an activated sludge upgrade, we have several references where Hybas™ has also been applied in greenfield projects, due to its many advantages. 



  • Simple upgrade to existing infrastructure/limited civil works
  • Compact footprint
  • Robust nitrification
  • Reduced filamentous growth/bulking sludge
  • Easy to combine biological P removal
  • Easy to add pre- and post denitrification to reach low Total N
  • Less sensitive to load and temperature variations
Hybas™ is a solution for nitrogen removal based on Integrated Fixed Film Activated sludge (IFAS) technology, where the best properties of MBBR and Activated Sludge (AS) are merged into one compact, energy-efficient system.


AnoxKaldnes’ technologies are found in more than 1,200 treatment plants around the world. Contact us for references related to your specific needs.

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