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Decentralized urine treatment with the nitritation/anammox process Part 2 (DUNOX-2)

Gesuchsteller/in Udert Kai
Nummer 144498
Förderungsinstrument Projektförderung (Abt. I-III)
Forschungseinrichtung Eawag
Hochschule Eidg. Anstalt für Wasserversorgung, Abwasserreinigung und Gewässerschutz - EAWAG
Hauptdisziplin Andere Gebiete der Ingenieurwissenschaften
Beginn/Ende 01.10.2012 - 31.03.2013
Bewilligter Betrag 29'419.00
Alle Daten anzeigen

Alle Disziplinen (4)

Andere Gebiete der Ingenieurwissenschaften
Experimentelle Mikrobiologie

Keywords (6)

Decentralized wastewater treatment; Anaerobic ammonium oxidation ; Population dynamics ; Microbial ecology; Urine separation; Nitrogen removal

Lay Summary (Englisch)

Lay summary


Novel decentralized reactors can be the key to a more efficient and affordable wastewater treatment. This project investigates, whether a novel biological process – nitritation/anammox – can be used to remove nitrogen in small on-site reactors.



Combining sewers and centralized wastewater treatment has worked reasonably well for the industrialized part of the world, but for a number of reasons the success in developing and fast industrializing countries has been very limited. Recent research has shown that separation of wastewater streams at the source and decentralized treatment would be more resource-efficient, cheaper and easier to implement. Especially the separate treatment of urine would strongly reduce environmental pollution. Lately, a biological process – one-stage nitritation/anammox – has been implemented in some wastewater treatment plants to remove nitrogen more efficiently from digester supernatant than conventional processes. Our laboratory experiments have shown that the process can also be used to remove nitrogen from urine, but the experiments also revealed that small changes in the operational parameters can lead to a persistenly low performance. Our first study suggests that the decrease in performance coincided with a regime shift of the microbial population.



In this follow-up study, we conduct well-controlled experiments to elucidate the main reasons for the regime shift. The main focus is on biodegradable organic substances. In well-controlled experiments, we investigate how the ratio of biodegradable substances to ammonia influences the activity of the nitrogen removing bacteria. Additionally, we analyze, whether specific organic substances inhibit nitrogen removing bacteria. Finally, we will test whether upstream removal of the organic substances leads to a more stable operation of the nitritation/anammox reactor.



The overall goal of the project is to determine optimal conditions for stable biological nitrogen removal from urine in small on-site reactors. Our study will also result in a better understanding of the influence of organic substances on nitritation/anammox processes.



Decentralized reactors for nutrient removal can be essential tools to fight the deterioration of aquatic environments worldwide. Biological processes such as nitritation/anammox could be energy-efficient options for nutrient removal, but operating such processes in small on-site reactors requires precise process control and in-depth understanding of the critical influence factors.

Many researchers and practitioners have experienced that high contents of biodegradable organic substances can be problematic for the nitritation/anammox process, therefore the results will be interesting for other process applications beyond urine treatment.

Direktlink auf Lay Summary Letzte Aktualisierung: 21.02.2013

Verantw. Gesuchsteller/in und weitere Gesuchstellende


Name Institut


Observability of anammox activity in single-stage nitritation/anammox reactors using mass balances
(2015), Observability of anammox activity in single-stage nitritation/anammox reactors using mass balances, in Environmental Science: Water Research & Technology, 1, 523-534.
Biological nitrogen conversion processes.
(2013), Biological nitrogen conversion processes., 291-305.
Successful application of nitritation/anammox to wastewater with elevated organic carbon to ammonia ratios
, Successful application of nitritation/anammox to wastewater with elevated organic carbon to ammonia ratios, in Water Research.


Gruppe / Person Land
Formen der Zusammenarbeit
Labmet, Ghent University Belgien (Europa)
- vertiefter/weiterführender Austausch von Ansätzen, Methoden oder Resultaten
- Publikation
- Austausch von Mitarbeitern

Verbundene Projekte

Nummer Titel Start Förderungsinstrument
125133 Decentralized urine treatment with the nitritation/anammox process (DUNOX) 01.04.2009 Projektförderung (Abt. I-III)
125133 Decentralized urine treatment with the nitritation/anammox process (DUNOX) 01.04.2009 Projektförderung (Abt. I-III)
128778 Confocal Microscopy at Eawag 01.09.2010 R'EQUIP


We apply for funding to extend the SNF-sponsored project DUNOX (200021_125133/1). The aim of this project is to investigate the suitability of the nitritation/anammox process for nitrogen removal from source-separated urine. In source-separated urine, the concentration of biodegradable organic substances is too low for conventional nitrogen removal, but it is so high that it can impede the nitritation/anammox process. The nitritation/anammox process is mediated by two types of autotrophic microorganisms, aerobic ammonium oxidizing bacteria (AOB) and anaerobic ammonium oxidizing bacteria (anammox, AMX). There are several ways, how organic substances can interfere with these bacteria. Some organic compounds are known to inhibit autotrophic bacteria; recent research suggests that other compounds, such as acetate and propionate, can enhance the competitiveness of AMX. The presence of biodegradable organic substances generally supports the growth of heterotrophic bacteria, which compete with AOB for oxygen and with AMX for nitrite. In the first part of the study, we successfully operated a sequencing batch reactor (SBR) with nitritation/anammox for nitrogen removal from source-separated urine. However, the experi-ments also showed that forcing the system to a higher performance can cause a lasting process failure. A regime-shift analysis of the chemical and physical parameters and cluster and ordination analysis of the microbial community indicated that the reactor had experienced a transition to a new stable state, which was characterized by nitrite accumulation and low nitrogen removal rates. Activity tests in batch reactors showed that after the transition, AMX activity was negligible, but quantification with real-time quantitative polymerase chain reaction revealed that AMX were still present. In other experiments, changing the influent from digester supernatant to source-separated urine caused an immediate breakdown of the AMX activity. The breakdown was accompanied by an accumulation of nitrite, which indicates that competition by heterotrophic bacteria for oxygen or nitrite was not the cause for the decrease in AMX activity. Our previous experiments thus show that nitritation/anammox can be used to remove nitrogen from source-separated urine, but the operation parameters have to be chosen well. We hypothesize that the high content of organic substances per se is not problematic for the treatment of source-separated urine. However, source-separated urine contains some substances that inhibit AMX. If the concen-tration of these substances becomes too high AMX are strongly harmed and they cannot compete with heterotrophic bacteria anymore. To test this hypothesis, we will start a nitritation/anammox SBR with digester supernatant. Then, we will gradually increase the content of biodegradable organic substances by adding acetate to the digester supernatant, until the level of organic chemical oxygen demand (COD) in source-separated urine is reached. With this experiment we want to show that high amounts of reduced organic substrates in the influent can be tolerated by a nitrita-tion/anammox reactor. Parallel to this experiment, we will test inhibition effects by urine compounds, which we assume to be inhibiting for AMX. These tests will be done in batch reactors with activated sludge from a stable nitritation/anammox reactor running on digester supernatant. Based on these experiments, we will be able to develop strategies for the successful operation of the nitritation/anammox process for source-separated urine. A better understanding of the effect of organic substances on the nitritation/anammox process will not only be relevant for nitrogen removal from source-separated urine but also for the treatment of many other wastewaters, including the integration of nitritation/anammox in main stream wastewater treatment.