Department Surface Waters - Research and Management

Ecological stability of microbial communities in mixed nitritation-anammox systems (Subproject of IsoMol)

Autotrophic nitrogen (N) removal by anaerobic ammonium oxidation (anammox) is an important mechanism of fixed N elimination, both in engineered and natural systems. Deployed in the mainstream of wastewater treatment plants, it may even permit operation under energy autarky. Autotrophic N removal by anammox bacteria involves simultaneous oxidation of ammonium (NH4+) and reduction of nitrite (NO2-) under oxygen-deficient conditions in a reaction first discovered in a denitrifying pilot plant. The main metabolic product of anammox is dissolved N2, which makes it an efficient fixed N removal pathway in engineered systems.

The overarching objective of the multidisciplinary IsoMol project is to understand links between biochemical pathways, the performance of microbial communities, environmental conditions, and the microbial composition involved in autotrophic nitrogen (N) removal.

Within this project, the microbial ecology group at Eawag Kastanienbaum will investigate the activity and ecological stability of anammox biofilms. A better understanding of the activities of anammox consortia is crucial for maintaining process stability and thus for assessing the feasibility of autotrophic N removal at larger scale. Resistance (degree to which a community withstands changes in the face of disturbance) and resilience (ability of the community to return to the pre-disturbance state) are two quantifiable metrics that directly affect microbial community stability. Thus, our main goal is to identify and understand the key mechanisms underlying the resistance and resilience of microbial communities involved in the autotrophic N removal.
We will perform disturbance experiments in small-scale bioreactors at Eawag Dübendorf and by combining measurements of performance parameters, biodiversity indices and gene transcripts, we will be able to map stability landscapes and understand the mechanistic underpinnings of stability and collapse in complex anammox biofilms.

Figure 1: The anammox process