Redirecting methane for a novel biological nitrogen removal process using methanotrophic mixed culture in a sequential batch reactor

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2021-01, Vol.404, p.126487, Article 126487
• Main Authors: Bishoff, Danelle, AlSayed, Ahmed, Fergala, Ahmed, Eldyasti, Ahmed
• Format: Article
• Language: English
• Subjects: Biogas; Biological nitrogen removal; Denitrification; Methane redirection; Methanotrophic bacteria; Nitrification
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2020.126487

•Methanotrophic-based nitrogen removal was validated in a sequential batch reactor.•Methanotrophic ammonium removal was attained by assimilation and nitrification.•The first study to demonstrate high nitrate production in methanotrophic bioreactor.•At a NLR of 0.2 and 0.1 kg/m3.day, ammonium to nitrate conversion ratio was >85%.•Further research is needed to maintain nitrification/denitrification with same sludge. Wastewater treatment plants (WWTP) are focusing more on water reuse and resources recovery where it is equally important to meet the discharge requirements and recover higher-value resources. Methanotrophs can be employed as a stepping-stone to consolidate such shift in WWTPs’ perspective by exploiting the untapped biogas and dissolved methane generated from anaerobic treatment of sludge and/or wastewater. Methanotrophic sludge can be used in multiple resources recovery processes such as biopolymers and single-cell proteins production. Fortunately, methanotrophs can couple nitrogen removal by methane utilization. Thus, this research investigates methane redirection for methanotrophic-based nitrogen removal enriched from activated sludge. Different phases allowed evaluation of the nitrogen removal capacity of the methanotrophic culture in a sequential batch reactor. When removing ammonium by assimilation, the ammonium removal efficiency (ARE) was 98 ± 1%. Under elevated ammonium concentration and mainstream-like conditions, the ARE was 89 ± 5% and 87 ± 7% and the ammonium conversion to nitrate was 87 ± 11% and 87 ± 7%, respectively. This study is the first to maintain stable nitrate accumulation using methanotrophic mixed cultures. Despite attained in batch experiments, the maintenance of nitrification-denitrification activity using the same sludge found to be challenging. This study successfully demonstrates the potential of using methanotrophic bacteria as an alternative for nitrogen removal.