Nitrite accumulation from simultaneous free-ammonia and free-nitrous-acid inhibition and oxygen limitation in a continuous-flow biofilm reactor

• Published in: Biotechnology and bioengineering Vol. 112; no. 1; pp. 43 - 52
• Main Authors: Park, Seongjun, Chung, Jinwook, Rittmann, Bruce E., Bae, Wookeun
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01.01.2015; Wiley Subscription Services, Inc
• Subjects: Accumulation; Ammonia; Ammonium Compounds - metabolism; ammonium oxidation; Bacteria; Bioengineering; biofilm; Biofilms; Bioreactors; Biotechnology - instrumentation; Biotechnology - methods; Dissolution; Equipment Design; Fatty Acids - metabolism; free ammonia inhibition; Inhibition; Nitrification; nitrite accumulation; Nitrites; Nitrites - metabolism; Nitrogen; Oxidation-Reduction; Oxygen; Oxygen - metabolism; oxygen limitation; Reactors; ammonium oxidation; nitrite accumulation; oxygen limitation; free ammonia inhibition; biofilm
• ISSN: 0006-3592; 1097-0290
• DOI: 10.1002/bit.25326

ABSTRACT To achieve nitrite accumulation for shortcut biological nitrogen removal (SBNR) in a biofilm process, we explored the simultaneous effects of oxygen limitation and free ammonia (FA) and free nitrous acid (FNA) inhibition in the nitrifying biofilm. We used the multi‐species nitrifying biofilm model (MSNBM) to identify conditions that should or should not lead to nitrite accumulation, and evaluated the effectiveness of those conditions with experiments in continuous flow biofilm reactors (CFBRs). CFBR experiments were organized into four sets with these expected outcomes based on the MSNBM as follows: (i) Control, giving full nitrification; (ii) oxygen limitation, giving modest long‐term nitrite build up; (iii) FA inhibition, giving no long‐term nitrite accumulation; and (iv) FA inhibition plus oxygen limitation, giving major long‐term nitrite accumulation. Consistent with MSNBM predictions, the experimental results showed that nitrite accumulated in sets 2–4 in the short term, but long‐term nitrite accumulation was maintained only in sets 2 and 4, which involved oxygen limitation. Furthermore, nitrite accumulation was substantially greater in set 4, which also included FA inhibition. However, FA inhibition (and accompanying FNA inhibition) alone in set 3 did not maintained long‐term nitrite accumulation. Nitrite‐oxidizing bacteria (NOB) activity batch tests confirmed that little NOB or only a small fraction of NOB were present in the biofilms for sets 4 and 2, respectively. The experimental data supported the previous modeling results that nitrite accumulation could be achieved with a lower ammonium concentration than had been required for a suspended‐growth process. Additional findings were that the biofilm exposed to low dissolved oxygen (DO) limitation and FA inhibition was substantially denser and probably had a lower detachment rate. Biotechnol. Bioeng. 2015;112: 43–52. © 2014 Wiley Periodicals, Inc. Long‐term nitrite accumulation was maintained in a continuous biofilm reactor only when oxygen limitation was involved. Nitrite accumulation was substantially greater when the reactor also included free‐ammonia (FA) inhibition, though FA inhibition alone did not maintain long‐term nitritation. Stable nitritation could be achieved with a lower ammonium concentration in a biofilm reactor than was required for a suspended‐growth process at a given dissolved oxygen concentration in the bulk liquid.