Mainstream anammox, potential & feasibility of autotrophic nitrogen removal

Maaike Hoekstra

Research output: ThesisDissertation (TU Delft)

118 Downloads (Pure)


Currently wastewater treatment plants (WWTP) consume a lot of energy and surface area. While the incoming water contains chemical energy (BOD) and reusable resources which are not effectively utilized. The ideal is to develop a treatment scheme which allows for the efficient removal of pollutants while minimizing the energy input and maximizing the recovery of energy and resources present in the wastewater. This thesis describes the potential and feasibility of implementing of the partial nitritation/anammox (PN/A) process in the mainstream of a municipal WWTP. Implementation of this technology will allow a complete re-design of the conventional wastewater treatment scheme from an energy consuming into an energy producing system.
In wastewater treatment plants nitrogen is currently removed in two sequential microbial conversions: nitrification and denitrification. For the nitrification step oxygen is needed and for the denitrification step anoxic conditions and BOD are required. The PN/A technology can be used to optimize the municipal mainstream wastewater treatment technology. In the PN/A process the incomplete oxidation of ammonium to nitrite (by aerobic ammonium oxidising bacteria, AOB) is combined with the anaerobic ammonium oxidation (by anammox bacteria). The first advantage is; due to the autotrophic nature of the pathways used, there is no longer a need for carbon to remove nitrogen through denitrification. The carbon in the wastewater can therefore be used for different means for instance for the production of biogas. A second advantage of the PN/A technology is the use of biofilms for (part of) the biomass. Biofilms/granules can lead to higher biomass concentrations in the reactor and therefore higher volumetric loading rates can be applied. Biofilms are easier to separate from water compared to sludge flocs, so a more compact sludge retention system can be built (compared to current secondary clarifiers). Thirdly all nitrogen conversions can take place in the same reactor, omitting the two different zones/tanks for nitrification/denitrification.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Delft University of Technology
  • van Loosdrecht, M.C.M., Supervisor
  • Kleerebezem, R., Advisor
Award date6 Dec 2017
Print ISBNs978-94-6332-276-8
Electronic ISBNs978-94-6332-276-8
Publication statusPublished - 2017


  • Wastewater
  • Nitrogen removal
  • Anammox
  • Biofilm


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