Model-based design and control of granular sludge reactors


Partial nitritation – anammox reaction in a granule
Partial nitritation – anammox reaction in a granule

Present wastewater treatment plants (WWTPs) are designed to obtain a high degree of organic matter and nitrogen removal by applying long sludge retention times. This requires a lot of aeration energy and does not take advantage of the energy present in the wastewater and in the sludge. In future, WWTP design is expected to be based on a high–loaded activated sludge system, where organic matter is removed and concentrated for energy formation through anaerobic digestion, followed by innovative nitrogen removal in a granular sludge anammox reactor. The latter process requires less aeration energy and no carbon source addition in comparison to conventional nitrification-denitrification over nitrate, while minimizing CO2 emissions and sludge production. Challenges to overcome for the implementation of this process in practice include its operation at typical (low) wastewater temperatures and uncertainty about the formation of N2O, being a very strong greenhouse gas.

Research objective

Optimization of the design and control of granular sludge anammox reactors in terms of

  • Effective nitrogen removal
  • Minimum energy requirements (cost-effectivenes)
  • Minimum GHG emissions (N2O)


  • Modelling and simulation
  • Lab-scale experiments
  • Full-scale monitoring


wastewater treatment; biological nitrogen removal; granular sludge reactor; partial nitritation-anammox; greenhouse gasses (N2O)

Project Administration

Researcher: Celia Maria Castro Barros

Financing: EU - Marie Curie Network of Initial Training "Sanitas"

Project duration: 01.05.2012 - 30.04.2015