During the years 2012-2016, VA SYD carried out a pilot project to study the introduction of anaerobic ammonium oxidation (anammox) to make the nitrogen removal in the mainstream more efficient at the Sjölunda Wastewater Treatment Plant (WWTP).

An introduction of anammox bacteria, as a significant nitrogen removal process in the mainstream of WWTPs, could reduce electrical energy use, replace needs of external carbon source dosing, dramatically increase biogas production, and remove the need for nitrate recirculation at the WWTPs.

A functioning process with anammox requires that the desired microbial cooperation is favoured and that unwanted competition is reduced. The anammox process has been implemented at more than 100 WWTPs worldwide for the treatment of warm, highly concentrated liquors from the dewatering of digested sewage sludge and industrial effluents. But the challenge of successfully introducing the anammox process into the mainstream of municipal WWTPs remains.

The main purpose of the project was to introduce the anammox process in the form of a nitritation-anammox process after the high-loaded activated sludge plant at Sjölunda WWTP. The pilot reactors contained moving carrier material, and were so-called moving-bed biofilm reactors (MBBRs). The pilot included both a mainstream process and a sludge liquor treatment. During most of the pilot study, carriers were moved between the mainstream and the reject water treatment. Nitritation-anammox was studied both as a one-step and as a two-step process.

The main conclusions of the project were:

  • The anammox bacteria managed to be maintained in the mainstream for more than 900 days.
  • Nitritation and anammox failed to become the completely dominant nitrogen removal processes. Nitratation, i.e. the nitrite-oxidising bacteria (NOB) that need to be inhibited for a successful anammox process, was not fully inhibited despite different aeration strategies.
  • The nitrogen removal rates were acceptable, but the nitrate residue was too high, which means that an external carbon source needs to be dosed.

The above conclusions and more are described in more detail in the publications below.

Suarez, C., Sedlacek, C.J., Gustavsson, D., Eiler, A., Modin, O., Hermansson, M., Persson, F. (2022) Disturbance-based management of ecosystem services and disservices in partial nitritation-anammox biofilms Nature,

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Pérez, J., Laureni, M., van Loosdrecht, M.C.M., Persson, F., Gustavsson, D. (2020) The role of the external mass transfer resistance in nitrite oxidizing bacteria repression in biofilm-based partial nitritation/anammox reactors Science Direct Water Research,

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Gustavsson, D.J.I., Suarez, C., Wilén, B.-M., Hermansson, M. & Persson, F. (2020) Long-term stability of partial nitritation-anammox for treatment of municipal wastewater in a moving bed biofilm reactor pilot system Science of the Total Environment 714, 136342. ,

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Gustavsson, D.J.I., Persson, G., Suarez, C., Persson, F. (2017) Four years of piloting mainstream nitritation-anammox. Nordic Wastewater Conference (NORDIWA) 2017. 10-12 October 2017, Aarhus, Denmark.,

Bårdskär S. (2016) Monitoring of denitrifying activities in moving bed biofilm reactors with an ex-situ manometric batch test. Master´s thesis. Lund University, Sweden.,

Gustavsson D. J. I. (2016) Pilot and prototype experiences at Sjölunda WWTP. Workshop – The future is here: experiences in the full-scale implementation of mainstream deammonification for leading edge nitrogen removal. The 13th IWA Leading Edge Conference on Water and Wastewater Technologies. Jerez de la Frontera, Spain, June 13-16, 2016.,

Hepdarcan E. G. (2016) Nitritation in mainstream conditions at Sjölunda WWTP. Master´s thesis. Lund University, Sweden.,

Ekström S., Domingo Felez C., Mark Jensen M., Gustavsson D. J. I., Persson F., la Cour Jansen J. & Smets B. F. (2015) Influence of aeration strategy on N2O emissions from a pilot-scale mainstream anammox process. Abstract: 14th Nordic Wastewater Conference – NORDIWA 2015, Bergen, Norway.,

Gustavsson D. J. I. (2015) Manammox – future nitrogen removal at Sjölunda WWTP? (In Swedish). Svensk Vatten Utveckling 25 år – då, nu och framtid. Stockholm, Sweden, December 2-3, 2015.,

Gustavsson D. J. I., Okhravi A., Persson F., Llano Alvarez N. & la Cour Jansen J. (2015) Experiences of repression of nitrite production in nitritation-anammox on municipal wastewater. Article: Proceedings of IWA Specialist Conference on Nutrient Removal and Recovery: moving innovation into practice, Gdansk, Poland, May 18-21, 2015, pp. 230-236.,

Okhravi A. (2015) Evaluation of the suppressive effect of intermittent aeration on nitrite-oxidising bacteria in a mainstream nitritation-anammox process. Master´s thesis. Uppsala University, Sweden.,

Persson F., Suarez C., Hermansson M., Plaza E., Sultana R., Gustavsson D. J. I. & Wilén B.-M. (2015) Microbial community structure of nitritation-anammox biofilms at main stream conditions. Article: Proceedings of IWA Conference Nutrient Removal and Recovery 2015: moving into practice. Gdansk, Poland, May 18-21, 2015, pp. 465-471.,

Suarez C., Persson F. & Hermansson M. (2015) Predation of nitritation-anammox biofilms used for nitrogen removal from wastewater. FEMS Microbiology Ecology 91(11),

Gustavsson D. J. I. (2014) Anammox – saves energy and resources. (In Swedish). Envisys Höstmöte Ny teknik inom avloppsvattenhantering 2014. Lund, Sweden, November 26-27, 2014.,

Gustavsson D. J. I., Persson F. & la Cour Jansen J. (2014) Manammox – mainstream anammox at Sjölunda WWTP. Article: Proceedings of 9th IWA World Water Congress and Exhibition, Lisbon, Portugal, September 21-26, 2014.,

Llano N. & Galkin V. (2014) Evaluation of bacteria population dynamics of mainstream anammox. Master´s thesis. Lund University, Sweden.,

Olofsson M. (2014) Method development of OUR test for measuring the activity of AOB, NOB and HB. (In Swedish). Internal report.,

Stefansdottir D. (2014) Manometric method for evaluation of anammox activity in mainstream anammox at Sjölunda WWTP. Master´s thesis. Lund University, Sweden.,