Reduction of N2O emissions from wastewater treatment plants - measurements, modeling and process optimization (RENEMO)

Content

The current regulatory paradigm for WWTPs focuses almost entirely on local water quality, at the unrecognized life cycle impacts mainly through energy consumption and greenhouse gas (GHG) emissions. In the face of the progressing global warming effect there has been a change of thinking within the wastewater treatment sector. During the last decade, the conflict between protection of receiving water bodies by all technical means available and the high energy input resulting in significant use of resources and release of greenhouse gasses has been identified and tackled. Optimization of existing treatment processes and development of innovative, energy-efficient processes especially for nitrogen removal have been the key objectives during the last years.

Recently, a more integrated view of greenhouse gas emissions from WWTPs has gained more and more attention. Preliminary studies indicated that apart from indirect emissions from electricity production the direct emissions of nitrous oxide (N2O) and methane (CH4) from biological processes at WWTPs might also play a major role in the CO2-footprint and should be included in life-cycle assessments. With concerns about the climate change, CO2 has received most of the attention, however, by weight N2O causes 300 times the warming effect of comparable amounts of CO2 in the atmosphere (IPCC, 2001).

In practise, the mechanisms and magnitudes of N2O emissions in WWTPs are poorly determined and subject of debate. To clarify this issue and create a basis for future process selection in line with climate-related requirements, it is important to close the current research gaps of reliable quantification of N2O and improving the understanding of the biological processes.

The RENEMO project is in line with these research needs and its main goals are defined as follows:

• Development of a general methodology of N2O measurements and estimation of N2O emissions in WWTPs,
• Comparison of the N2O emissions from different N removal processes (partial nitrification-anammox vs. simultaneous nitrification-denitrification; mainstream treatment vs. sidestream treatment),
• Development of a general model for N conversions in activated sludge systems (multi-step nitrification/denitrification, anammox) as a predictive tool for optimization of wastewater treatment processes,
• Derivation of operational strategies to minimize N2O emissions especially for innovative nitrogen removal processes, comparison and evaluation of these strategies supported by simulations and compilation of recommendations for optimized operation and process design.

Project partner:

Gdansk University of Technology, Faculty of Civil and Environmental Engineering; E&P Anlagenbau GmbH