Continuous anaerobic oxidation of methane: Impact of semi-continuous liquid operation and nitrate load on N2O production and microbial community. (September 2021)

• Record Type: Journal Article
• Authors: Valenzuela, Edgardo I.; Ortiz-Zúñiga, María F.; Carrillo-Reyes, Julián; Moreno-Andrade, Iván; Quijano, Guillermo
• Is Part Of: Chemosphere. Volume 278(2021)
• Publication Date: 2021-09
• Subjects: Anaerobic oxidation of methane -- Greenhouse gas -- Microbial community -- Nitrate removal -- Nitrous oxide production; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2021.130441
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: This work proves the feasibility of employing regular secondary activated sludge for the enrichment of a microbial community able to perform the anaerobic oxidation of methane coupled to nitrate reduction (N-AOM). After 96 days of activated sludge enrichment, a clear N-AOM activity was observed in the resulting microbial community. The methane removal potential of the enriched N-AOM culture was then studied in a stirred tank reactor (STR) operated in continuous mode for methane supply and semi-continuous mode for the liquid phase. The effect of applying nitrate loads of ∼22, 44, 66, and 88 g NO3 − m −3 h −1 on (i) STR methane and nitrate removal performance, (ii) N2 O emission, and (iii) microbial composition was investigated. Methane elimination capacities from 21 ± 13.3 to 55 ± 12 g CH4 m −3 h −1 were recorded, coupled to nitrate removal rates ranging from 6 ± 3.2 to 43 ± 14.9 g NO3 − m −3 h −1 . N2 O production was not detected under the three nitrate loading rates applied for the assessment of potential N2 O emission in the continuous N-AOM process (i.e. ∼22–66 g NO −3 m −3 h −1 ). The lack of N2 O emissions during the process was attributed to the N2 O reducing capacity of the bacterial taxa identified and the rigorous control of dissolved O2 and pH implemented (dissolved O2 values ≤ 0.07 g m −3 and pH of 7.6 ± 0.4). Microbial characterization showed that the N-AOM process was performed in absence of putative N-AOM archaea and bacteria (ANME-2d, M. oxyfera ). Instead, microbial activity was driven by methane-oxidizing bacteria and denitrifying bacteria (Bacteroidetes, α-, and γ-proteobacteria). Graphical abstract: Image 1 Highlights: Continuous N-AOM was successfully implemented from activated sludge. N2 O was not detected at nitrate loading rates of 22–66 gNO3 - m −3 h −1 . A maximum CH4 elimination capacity of ∼55 g m −3 h −1 was recorded. M. nitroreducens (ANME-2d) and M. oxyfera were absent.