The Project

The Project


The knowledge about sources and sinks for N2O during biological wastewater treatment (WWT) is rudimentary: Both nitrification and denitrification are, however, considered as sources (see Figure 1). In nitrification, two separate groups of autotrophic microbes oxidize NH4+ to NO2- and NO2- to NO3-  through a two-step aerobic process. N2O can be produced via two different reactions by aerobic ammonium-oxidizing microbes (NH4+ to NO2-): 1) the oxidation of NH2OH to N2O (the hydroxylamine pathway) or 2) the reduction of NO2- to N2O (the nitrifier-denitrification pathway. In heterotrophic denitrification, bacteria reduce NO3- or NO2- via N2O to N2 under anoxic conditions. Depending on the balance between NO2- reduction and N2O reduction, denitrification is either a source or a sink for N2O.

This project focuses on the environmental biochemistry, microbial ecology and environmental and cellular control of N2O production during biological WWT.

Figure 1: Potential microbial pathways for N2O production in WWTPs. 
NH2OH = hydroxylamine. Abbreviation for specific enzymes is as following: AMO = Ammonia monooxygenase. HAO = Hydroxylamine oxidoreductase. NOR = Nitric oxide reductase. NAP/NAR = Nitrate reductase. NIR = Nitrite reductase. NOZ = Nitrous oxide reductase. Redrawn after Wrage N et al. (2005) Rapid communications in mass spectrometry 19: 3298-3306.