A targeted study on possible free ammonia inhibition of Nitrospira

Abstract

Batch tests were carried out with Nitrospira in mixed and pure cultures using concentrations of free ammonia widely believed to be inhibitory to nitrite-oxidizing organisms. The mixed culture batch tests were conducted with mixed liquor from a bench scale completely stirred tank reactor (CSTR) treating a synthetic wastewater having a low C:N ratio. Nitrospira were confirmed as the dominant nitrite oxidizers via RNA slot blotting. Nitrospira moscoviensis were used for the pure culture trials. The results from this study suggest that free ammonia (NH3-N) concentrations of up to 10 mg/L were not inhibitory to Nitrospira either in situ or in pure culture. Key words: fatty acid methyl esters, free ammonia inhibition, molecular methods, nitrification, nitrite, Nitrobacter, Nitrospira, nitrous acid, nitrous oxide, RNA slot blotting, wastewater treatment.

Enhanced nitrite accumulation under mainstream conditions by a combination of free ammonia-based sludge treatment and low dissolved oxygen: reactor performance and microbiome analysis

“…Meanwhile, a higher nitrite accumulation in the experimental reactor indicated that FA treatment in phase II (130.6 mg NH 3 L −1 ) could inhibit the activity of Nitrospira , not contradictory with the previous study, where an FA concentration of 12.1 mg NH 3 L −1 was ineffective in the inhibition of Nitrospira . 36 Because the FA concentration in the side-stream sludge treatment was nearly eleven times higher than that in the literature, Nitrolancea was not favored at the operational conditions of this study for its thermophilic ecological niche. The relative abundance of Nitrospira increased to 0.5% in C3 and 0.7% in E3.…”

Relevance of Nitrospira for nitrite oxidation in a marine recirculation aquaculture system and physiological features of a Nitrospira marina‐like isolate

“…A particular sensitivity of NOB towards FA was stated elsewhere (Villaverde et al ., 2000; Kim et al ., 2006). However, this issue seems to be controversial, since authors recently reported relatively high FA tolerances for Nitrospira (mixed and pure cultures) and Nitrobacter (Simm et al ., 2006; Hawkins et al ., 2010). These are in accordance with the results in this study, where approximate 0.7 mM NH 3 ‐N did not inhibit growth of Ecomares 2.1.…”

Integrating Genome-Resolved Metagenomics with Trait-Based Process Modeling to Determine Biokinetics of Distinct Nitrifying Communities within Activated Sludge

“…The washout of NOB and promotion of shortcut nitrogen removal can provide up to 25% aeration energy savings compared to conventional nitrification–denitrification processes, or 60% aeration savings when combined with anammox . Consequently, much focus has been placed on developing operational selective pressures for AS that wash out NOB by means of dissolved oxygen limitation, , cyclic aeration, , solids retention time (SRT) control, or exposure of biomass to inhibitory agents like free ammonia (FA) and free nitrous acid. , However, NOB have been shown to adapt to many of these selective pressures, − likely due to their high metabolic flexibility and physiological diversity, especially in Nitrospira -related genera ,− ( e.g. , Nitrospira _A, Nitrospira _C, Nitrospira _D, Nitrospira ,_E, and Nitrospira _F in the Genome Taxonomy Database).…”