How Nereda compares on N2O emissions
Today, wastewater treatment plants (WwTPs) produce around 1.6% of all the world's greenhouse gas (GHG) emissions. The industry urgently needs to reduce harmful gases like nitrous oxide (N2O) for both environmental and practical reasons.
As urbanisation and population growth demand more capacity and effluent standards increase, water authorities are under pressure to do more – often in limited physical footprints and with CapEx and OpEx constraints. Funding and support to meet these challenges can depend on demonstrating the right sustainability credentials to public sector stakeholders.
A recent, peer-reviewed research paper shows that Nereda aerobic granular sludge (AGS) can help to address this issue. The paper compares Nereda to other wastewater treatment technologies in terms of their ability to tackle N2O.
Reducing nitrous oxide emissions economically and productively
When we talk about sustainability, we often focus on carbon dioxide (CO2). But N2O has a damaging effect on the environment than CO2 – 298 times more potent in fact.
N2O is produced during nitrification and denitrification processes in biological wastewater treatment which is relevant to any nitrifying activated sludge technology.The challenge for water authorities around the world is not only how to reduce N2O emissions from WwTP processes to achieve net zero, but how to do it more economically, productively, and sustainably.
Research to date on N2O emissions for any technology remains limited; however, the database continues to grow as more and more end users implement monitoring campaigns.
Game-changing research on N2O emissions for AGS plants
In 2021, Edward van Dijk, Mario Pronk, and Professor Mark van Loosdrecht published the results from a collaboration between Royal HaskoningDHV and the TU Delft showing that AGS could be a game-changer for WwTPs seeking to reduce GHG emissions.
The seven-month N2O measurement study took place in Dinxperlo, The Netherlands at the full-scale AGS plant, which has three Nereda reactors and a small influent buffer.
The results of the study, which was published in Water Research issue 198, show that Nereda’s N2O emissions is comparable to CAS systems, and better than conventional SBRs.
Nereda matches CAS and outperforms conventional SBRs
In the paper, van Dijk et al. compare their results with findings from a 2019 study, A decade of nitrous oxide (N2O) monitoring in full-scale wastewater treatment processes: A critical review, to compare all the wastewater treatment processes side by side.
The data shows that while the average emission factor (EF) for CAS is below 0.5%, the average EF for SBR is closer to 5%. By contrast, van Dijk’s paper showed an average EF for DinxperloNereda® plant of 0.33 % based on the total nitrogen concentration in the influent.
According to van Dijk et al. “This underlines that the values found in this study are comparable to many other wastewater treatment systems but are considerably lower than the values reported for conventional SBR systems.” This is significant, since the Nereda AGS process is operated as an SBR, so in absence of data, many default to these higher values.
Nereda’s higher information density makes it quicker to act
So, if Nereda operates as an SBR, how can it perform significantly better when it comes to N2O?
This study shows that you can have a batch system with low emissions. The process conditions, including those that impact N2O emissions, in a Nereda® plant differ from conventional SBR systems. The simultaneous nitrification / denitrification, which is typical for the AGS process will also remove a large part of any N2O formed.
The batch approach, along with the real-time data from instrumentation used by the Nereda Controller, also provides better visibility into the production and consumption of N2O, making it better suited for limiting these emissions as operators can see immediately what’s happening– and can act quicker to adjust processes that impact emissions.
Further, the Nereda controller uses artificial intelligence to continually improve the process which can be leveraged to even further minimise the nitrous oxide emissions.
Efficient, effective, and environmentally friendly N2O removal
These findings represent a significant opportunity for WwTPs – and the wastewater treatment industry overall – to make a significant reduction in GHG emissions.
Van Dijk et al.: “Although in general only a small fraction of the influent ammonium is emitted as nitrous oxide, the large greenhouse warming potential can make N2O emission the dominant factor in the carbon footprint of a wastewater treatment plant.”
Nereda technology provides several benefits for water utilities by enabling WwTPs to remove N2O at a fraction of the cost, energy consumption, and environmental impact of other technologies.
Compared to A/B CAS WwTPs, with EFs comparable to those found in the study for AGS, Nereda plants have up to 75% smaller physical footprints and 50% lower energy consumption. With less mechanical equipment and smart digital operation, they require lower maintenance and less manual operation time. Nereda also enables WwTPs to meet nutrient removal standards while using negligible-to-zero chemicals, further saving costs.
All these factors make it a more efficient, more cost-effective, and more environmentally friendly way to minimise emissions of harmful GHGs like N2O.
Monitoring N2O at Panheel
The study at Dinxperlo is by no means the only research in this area for AGS.
Since November, Royal HaskoningDHV has been working in cooperation with Dutch water board, Waterschapsbedrijf Limburg (WBL), and TU Delft on a project to measure N2O production and emission from a full-scale Nereda plant at Panheel in the Netherlands.
The project aims to discover the difference between the production and emission of N2O at both the liquid and gas phase of the treatment process to see how plant operators can lower emissions further. We expect the first results later this year.
Experts in wastewater consultancy and products
As one of the world’s leading wastewater treatment consultancies with over 140 years of engineering experience, Royal HaskoningDHV helps to overcome an array of business and sustainability challenges for WwTPs.
For decades, we have worked with forward-thinking water authorities, research universities, and globally renowned providers for wastewater solutions and projects. And we’re continually improving our solutions and knowledge. With over 100 projects in under two decades, Nereda has become a proven natural choice for treating wastewater. And we’ve been researching the causes, challenges, and impacts of N2O within WwTPs for 12 years.
Read the full study here: https://doi.org/10.1016/j.watres.2021.117159
1Edward J.H. van Dijk, Mark C.M. van Loosdrecht, Mario Pronk, Nitrous oxide emission from full-scale municipal aerobic granular sludge, Water Research, Volume 198, 2021, 117159, ISSN 0043-1354, https://doi.org/10.1016/j.watres.2021.117159.
