The effect of hydroxylamine on the activity and aggregate structure of autotrophic nitrifying bioreactor cultures

✍ Scribed by Willie F. Harper Jr.; Akihiko Terada; Franck Poly; Xavier Le Roux; Ken Kristensen; Mustafa Mazher; Barth F. Smets

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 634 KB
• Volume: 102
• Category: Article
• ISSN: 0006-3592
• DOI: 10.1002/bit.22121

✦ Synopsis

Abstract

Addition of hydroxylamine (NH~2~OH) to autotrophic biomass in nitrifying bioreactors affected the activity, physical structure, and microbial ecology of nitrifying aggregates. When NH~2~OH is added to nitrifying cultures in 6‐h batch experiments, the initial NH~3~‐N uptake rates were physiologically accelerated by a factor of 1.4–13. NH~2~OH addition caused a 20–40% decrease in the median aggregate size, broadened the shape of the aggregate size distribution by up to 230%, and caused some of the microcolonies to appear slightly more dispersed. Longer term NH~2~OH addition in fed batch bioreactors decreased the median aggregate size, broadened the aggregate size distribution, and decreased NH~3~‐N removal from >90% to values ranging between 75% and 17%. This altered performance is explained by quantitative fluorescence in situ hybridization (FISH) results that show inhibition of nitrifying populations, and by qPCR results showing that the copy numbers of amoA and nxrA genes gradually decreased by up to an order‐of‐magnitude. Longer term NH~2~OH addition damaged the active biomass. This research clarifies the effect of NH~2~OH on nitrification and demonstrates the need to incorporate NH~2~OH‐related dynamics of the nitrifying biomass into mathematical models, accounting for both ecophysiological and structural responses. Biotechnol. Bioeng. 2009; 102: 714–724. © 2008 Wiley Periodicals, Inc.