Nitrogen Removal Processes in Wastewater Treatment Systems
Summary
Efficient removal of nitrogen from wastewater is vital to prevent eutrophication, to curb greenhouse gas emissions and to reclaim nutrients for circular‐economy applications. Biological processes dominate treatment schemes and include nitrification, whereby ammonia is oxidised to nitrite and nitrate by specialised bacteria, and denitrification, in which nitrate is sequentially reduced to molecular nitrogen under anoxic conditions. The anaerobic ammonium oxidation (anammox) pathway provides a low‐energy shortcut by converting ammonium and nitrite directly to dinitrogen gas. Emerging strategies integrate these processes in membrane bioreactors or granular sludge systems to enhance retention of biomass and reduce sludge production. Physicochemical techniques—such as ammonia stripping, ion exchange and struvite precipitation—are increasingly coupled with biological stages to recover ammonium as value‐added products. Hybrid configurations now aim to minimise energy consumption and nitrous oxide release while maximising nitrogen removal and nutrient recovery at scale.
Research from Nature Portfolio
Recent studies have enriched novel nitric oxide‐reducing consortia in continuous bioreactors, revealing microorganisms capable of converting nitric oxide to dinitrogen with negligible nitrous oxide production, offering a route to mitigate climate‐active gas emissions during denitrification. A phyloecological investigation of nitrate ammonifiers across global terrestrial biomes has elucidated the distribution of nrfA‐encoding bacteria relative to traditional denitrifiers, demonstrating that soil carbon‐to‐nitrogen ratios primarily govern the prevalence of ammonification versus denitrification pathways. Foundational genome‐centric analysis of anammox granules has further advanced understanding of metabolic networks and interspecies interactions underpinning anaerobic ammonium oxidation in engineered reactors.
Nitrogen Removal Processes in Wastewater Treatment Systems publication trend
The graph below shows the total number of articles in nitrogen removal processes in wastewater treatment systems across all publications each year (not limited to Nature Index journals).
Technical terms
Nitrification: aerobic microbial oxidation of ammonia to nitrate via nitrite.
Denitrification: anaerobic reduction of nitrate to molecular nitrogen.
Anammox (Anaerobic ammonium oxidation): microbial conversion of ammonium and nitrite directly to nitrogen gas under anoxic conditions.
Nitrate ammonification: microbial reduction of nitrite to ammonium, contributing to nitrogen retention and influencing greenhouse gas fluxes.
Struvite precipitation: chemical recovery process forming magnesium ammonium phosphate crystals, enabling simultaneous removal of ammonium and phosphate.
References
- Strategies for ammonia recovery from wastewater: a review. Environmental Chemistry Letters (2024).
- Net-zero carbon condition in wastewater treatment plants: A systematic review of mitigation strategies and challenges. Renewable and Sustainable Energy Reviews (2023).
- Enrichment and characterization of a nitric oxide-reducing microbial community in a continuous bioreactor. Nature Microbiology (2023).
- Phyloecology of nitrate ammonifiers and their importance relative to denitrifiers in global terrestrial biomes. Nature Communications (2023).
- Metabolic network analysis reveals microbial community interactions in anammox granules. Nature Communications (2017).
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