Membrane-aerated biofilm reactor (MABR) technology is an exciting alternative to conventional activated sludge, with promising results in bench and pilot-scale systems. Nevertheless, there is still a lack of long-term and full-scale data under different operational conditions. This study aims to report the performance of a full-scale hybrid MABR located in the North of Europe. Influent, effluent, and exhaust data were collected for 1 year (September 2019 to September 2020) using online sensors/gas-analyzers and off-line laboratory analysis. Next, oxygen transfer rate (OTR), oxygen transfer efficiency (OTE), and nitrification rates (NR) were quantified as process indicators. Finally, multivariate methods were used to find patterns among monitored variables. Observations revealed that lower airflows achieved higher OTE at the same values of OTR and OTR was strongly correlated to ammonia/um concentration in the MABR tank (NHx,eff). The dynamics between oxygen concentration in the exhaust (O2,exh) and NHx,eff indicated that a nitrifying biofilm was established within 3 weeks. Average NR were calculated using four different methods and ranged between 1 and 2 g N m−2d−1. Principal component analysis (PCA) explained 81.4% of the sample variance with the first three components and cluster analysis (CA) divided the yearly data into five distinctive periods. Hence, it was possible to identify typical Nordic episodes with high frequency of heavy rain, low temperature, and high variations in pollution load. The study concludes that nitrification capacity obtained with MABR is robust during cold weather conditions, and its volumetric value is comparable to other well-established biofilm-based technologies. Moreover, the aeration efficiency (AE) obtained in this study, 5.8 kg O2 kW h−1, would suppose an average reduction in energy consumption of 55% compared to fine pore diffused aeration and 74% to the existing surface aeration at the facility.
Bibliographical noteThis is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Nerea Uri-Carreño gratefully acknowledges the Industrial Ph.D. program's financial support from Innovation Fund Denmark , through the project “MANTRA” (Contract-No: 7091-00038A ). Dr. Flores-Alsina also thanks the Danish Council for Independent Research in the frame of the DFF FTP research project GREENLOGIC (Contract-No:7017–00175A) and the Danida fellowship center (DFC) research project ERASE (Contract-No: 18-M09-DTU). The authors would like to thank Dr. Dwight Houweling for the careful reviewing of the manuscript which clearly improved its final quality.
- Cluster analysis
- Low temperature
- Nitrogen removal
- Oxygen transfer