Partial denitritation coupled with anammox

Municipal wastewater treatment plants possess the capacity to be energy-positive through allocation of organic carbon to biogas production. This is, however, in direct conflict with the need of readily available organic carbon source in the traditional biological nutrient removal (BNR) processes. The anaerobic ammonium oxidation (anammox) process is autotrophic, but dependent of a nitrite provider. Inhibition of nitrite oxidising bacteria (NOB) have shown to be difficult in cold and weak municipal wastewaters. Instead, heterotrophic partial denitrification seems to be a better nitrite provider.

Partial denitritation coupled to anammox (PDA) is a novel process and only one study has investigated fermented sludge as a carbon source for the PDA process. The PDA process coupled with preceding partial nitrification has the potential of decreasing the aeration need up to 50% and organic carbon need up to 80% compared to conventional nitrification-denitrification.

VA SYD is a municipal joint authority, operating several wastewater treatment plants (WWTPs) in southern Sweden. VA SYD explores the possibilities implementing the PDA process in the next generation of wastewater treatment plants.


The main objectives of this project are (i) to study and analyse the operational results of a one-stage PDA biofilm process with preceding partial degradation of organics and partial nitrification in pilot-scale treating real pre-filtrated wastewater, and (ii) to follow the dynamics of the microbial communities in the biofilms by ex-situ batch activity tests.


Data gained by 24-hour flow-proportional samples, grab samples and online measurements are processed and analysed. Ex-situ batch activity tests are performed in lab-scale reactors in the laboratory

Project supervisors

David Gustavsson, research leader, VA SYD/Sweden Water Research (

Elin Ossiansson, industrial PhD student, VA SYD/Sweden Water Research (

Per Falås, researcher, Lund University (