Understanding the seasonal variation of greenhouse gas production in wastewater treatment plants

The international Doctoral Program Environment Water (ENWAT) of the Faculty of Civil and Environmental Engineering Sciences University of Stuttgart Germany in collaboration with the German Academic Exchange Service (DAAD) opens a call for max. 2 PhD positions for research in Environment Water. Each project involves high-quality research and state-of-the-art techniques and is supervised by excellent researchers. We are looking for highly motivated and talented students with a passion for science. Candidates must demonstrate an excellent performance in their previous academic education.

Title: Understanding the seasonal variation of greenhouse gas production in wastewater treatment plants

Advisor: Prof. Dr. Sara Kleindienst

Research group / department: Department of Environmental Microbiology Institute for Sanitary Engineering Water Quality and Solid Waste Management (ISWA)

Keywords: microorganisms denitrification nitrification (anaerobic) ammonia oxidation methanogenesis microbial community structure microbial activities cultivation microcosms emissions greenhouse gases

Introduction / Background:

Wastewater treatment plants (WWTPs) are estimated to contribute 8 11% of the methane and 2.7% of the nitrous oxide global gas emissions. Methane and nitrous oxide are greenhouse gases (GHG) and are 27 and 273 times more potent than CO2 respectively (Intergovernmental Panel On Climate Change (IPCC) 2023). Additionally nitrous oxide is considered to be the major anthropogenic contributor to the depletion of atmospheric ozone (Gruber Von Knel et al. 2021). These GHG are produced in the WWTPs by the action of methanogenic nitrifying and denitrifying microorganisms with the latter two being integral parts of the wastewater treatment process. For example previous studies have shown that a decrease in the number of nitrite-oxidizing bacteria could lead to an accumulation of nitrite in the system (Gruber Niederdorfer et al. 2021). Nitrite accumulation coupled with suboptimal aeration rates can induce the denitrification activity of ammonia-oxidizing bacteria leading to higher production of nitrous oxide (Chen et al. 2018). There is also seasonal and diurnal variations in nitrous oxide emissions which are correlated with the accumulation of nitrite or suboptimal oxygen concentrations in the system respectively (Daelman et al.; Gruber Von Knel et al. 2021). Seasonal variations in methane emission rates also occur and appear to be positively correlated with seasonal changes in water temperature (Masuda et al. 2015). Understanding how changes in the composition and flow rates of incoming wastewater can affect microbial community dynamics in WWTP is of the utmost importance. This will allow us find potential solutions that could lead to the reduction of GHG emissions from the wastewater treatment process.

References:

Li X

Chen X. Yuan Z. & Ni B.-J. (2018). Nitrite accumulation inside sludge flocs significantly influencing nitrous oxide production by ammonium-oxidizing bacteria. Water Research 143 99108. M. R. J. Van Voorthuizen E. M. Van Dongen L. G. J. M. Volcke E. I. P. & Van Loosdrecht M. C. M. (2013). Methane and nitrous oxide emissions from municipal wastewater treatment results from a long-term study. Water Science and Technology 67(10) . M. R. J. van Voorthuizen E. M. van Dongen U. G. J. M. Volcke E. I. P. & van Loosdrecht M. C. M. (2015). Seasonal and diurnal variability of N2O emissions from a full-scale municipal wastewater treatment plant. Science of The Total Environment 536 111. W. Niederdorfer R. Ringwald J. Morgenroth E. Brgmann H. & Joss A. (2021). Linking seasonal N2O emissions and nitrification failures to microbial dynamics in a SBR wastewater treatment plant. Water Research X 11 100098. W. Von Knel L. Vogt L. Luck M. Biolley L. Feller K. Moosmann A. Krhenbhl N. Kipf M. Loosli R. Vogel M. Morgenroth E. Braun D. & Joss A. (2021). Estimation of countrywide N2O emissions from wastewater treatment in Switzerland using long-term monitoring data. Water Research X 13 100122. Panel On Climate Change (IPCC). (2023). Climate Change 2021 The Physical Science Basis: Working Group I Contribution to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (1st ed.). Cambridge University Press. S. Suzuki S. Sano I. Li Y.-Y. & Nishimura O. (2015). The seasonal variation of emission of greenhouse gases from a full-scale sewage treatment plant. Chemosphere 140 167173. Tasks

Research goals

• To unravel the seasonal microbial interactions between key microbial communities involved in the production of GHGs in WWTPs.
• To establish laboratory microcosms using labelled substrates to determine how changes in the microbial community and environmental parameters lead to changes in GHG emissions.
• To perform in situ experiments at the WWTP located in ISWA to study how control parameters can be optimized to minimize changes in the plants microbiota leading to reduced GHG emissions.

Methods to be used

• Quantification of physicochemical parameters substrates and products (e.g. via HPLC IC GC-MS)
• Aerobic and anaerobic enrichment of WWTP microbial communities
• Electrochemical sensors to quantify dissolved nitrous oxide and other related parameters in the wastewater FTIR to quantify GHG emissions
• 16S rRNA gene amplicon sequencing
• Metagenomic and metatranscriptomic sequencing
• Statistical analysis of the obtained data sets

Prerequisites:

• Solid background in molecular ecology and environmental microbiology
• Ability to work independently and in a team
• Excellent management and communication skills
• Highly motivated and committed to pursuing interdisciplinary research
• Very good computer and language skills (English)

Further Prerequisites:

• Resume/CV showing the applicants background professional skills a list of publications and oral and poster presentations as well as additional achievements (scholarships awards etc.)
• . Dipl.-Ing. or equivalent degree in Civil Engineering Water Resources Management Environmental Engineering or related sciences
• . in Civil Engineering Water Resources Management Environmental Engineering or related sciences

Copies of Certificates and Transcripts including all undergraduate level certificates and university degrees. All documents which are not in English or in German must be accompanied by copies of a legally certified English translation (for the application we will accept copies; but please be aware that originals or legally certified copies will be needed for the final case any differences between the copies and the originals show up the application will be dismissed.)

Please make sure that the copies of the transcripts show not only the grades but also explain the home grades system (please add copy of the description of grade scale).

• At the time of nomination to the DAAD (Dec 2025) generally no more than 6 years should have passed since the last degree was gained.
• Only international (non-German) applicants can be accepted. At the time of nomination to the DAAD (Dec 2025) the candidate must not have been resident in Germany for more than the last 15 months.
• Unless native speaker: proficiency in English (e.g. TOEFL IELTS etc.) or proof that . and . programs were held in English.
• 2 Reference letters from university professors from the applicants home university issued during the last 2 years.
• Motivation letter describing the applicants work experience and research goals (1 page)
• Summary of all relevant information about the applicant (1 page) - please upload it in the slot designated for the third reference.

Research Environment

The Department of Environmental Microbiology at the Institute for Sanitary Engineering Water Quality and Solid Waste Management (ISWA) at the University of Stuttgart consists of an interdisciplinary international and dynamic team of environmental microbiologists microbial ecologists and chemists. The research group focuses on fundamental research with links to applied areas and studies topics related to microbial pollutant degradation. More information can be found on our webpage: The PhD candidate will get the opportunity to be creative and innovative and to work on a challenging and interdisciplinary topic.