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Updated: May 29, 2026

Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O
Published on: October 7, 2020
Free nitrous acid selectively inhibits and eliminates nitrite oxidizers from nitrifying sequencing batch reactor
Dong-Jin Kim1, Doug-Won Seo, Seung-Hwan Lee
1Department of Environmental Sciences and Biotechnology, Hallym University, 1 Okchon, Chuncheon, Gangwon, Korea. dongjin@hallym.ac.kr
Abstract:
In a complete nitrification sequencing batch reactor (CNSBR), where ammonium containing wastewater (200-1,000 mg N/L) is completely oxidized to nitrate up to 2.4 kg NH(4) (+)-N/m(3) d, both ammonia oxidizers and nitrite oxidizers were enriched in the sludge granules. Quantitative fluorescence in situ hybridization analyses of the sludge granules of the CNSBR showed that ammonia oxidizers and nitrite oxidizers occupied 31 and 4.2% of total bacteria, respectively. Most of the nitrite oxidizers were Nitrobacter species (95% of the nitrite oxidizers) and the remainder was Nitrospira species. The population of nitrite oxidizers was significantly higher than that of partial nitrification SBR (PNSBR) where most of the ammonium was oxidized to nitrite. The PNSBR had 37% (ammonia oxidizers) and 0.4% (nitrite oxidizers) of total bacteria. Comparative study with CNSBR and PNSBR revealed that free nitrous acid, rather than free ammonia, played a critical inhibition role to wash out nitrite oxidizers from the reactor. The concentrations of free ammonia and nitrite as well as free nitrous acid in the CNSBR selected Nitrobacter as the dominant nitrite oxidizers rather than Nitrospira.
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