The gas laughing (nitrous oxide or n₂o) is mainly released by microorganisms responsible for cleaning our wastewater. These microbes live in complex communities, each group playing a specific role. The emissions vary throughout the day and between the seasons, and the complex microbial processes behind them remain largely unknown, which makes it difficult to design effective strategies to reduce emissions.
Motivated by the need to resolve this longtime puzzle, Michele Laureni (Deputy Professor BIOPROCESS Engineering) and Mark Van Loosdrecht (Professor Biotechnology Environmental Biotechnology) joined the Dutch Water Authorities and Stowa. According to their supervision, Dr. Nina’s roothans applied advanced techniques-including DNA and protein analyzes-to study, in detail, how individual microorganisms interact in TPA over a period of two years.
Amsterdam West WWTP from Water Authority Amstel, Gooo and Vecht, operated by Waternet, was its model ecosystem. Research, published in Natural waterrevealed how environmental and operational factors – such as temperature and oxygen levels – Impact of nitrous oxide emissions.
Oxygen has an impact
One of the main discoveries of turners was that the accumulation of nitrite – a central intermediary in the degradation of nitrogen compounds – is linked to an imbalance between two groups of bacteria: those which convert ammonia into nitrite and those which convert nitrite into nitrate. Because nitrite is a precursor of nitrous oxide, this imbalance has been identified as the main cause of nitrous oxide or gas emissions laughing.
-Above all, the coatings have also identified the oxygen concentration – something that operators have direct control – as the main factor inducing this imbalance.
And that, notes Laureni, is precisely where the opportunity is. “The right thing is that, in principle, the solution may not require major infrastructure changes. The idea is that the gradual increase in oxygen, rather than doing it suddenly when winter is approaching, can already considerably reduce emissions.
Simple and profitable
These results are particularly relevant to the water authorities because they not only indicate potential means of reducing nitrous oxide emissions, but also suggests that the required interventions can be both simple and profitable. The question of whether the strategy identified proves in practice will become clear in the years to come.
Two new doctoral students. The candidates are now continuing work to develop and validate the approach, in collaboration with the water authorities and Royal Haskoningdhv. The fundamental ideas of turners’ work should also benefit the agricultural sector, where microbial nitrous oxide emissions pose an even greater challenge.
