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Concurrent nitrite oxidation and aerobic denitrification in activated sludge exposed to volatile fatty acids
Author(s) -
Oguz Merve T.,
Robinson Kevin G.,
Layton Alice C.,
Sayler Gary S.
Publication year - 2007
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.21379
Subject(s) - chemistry , nitrospira , nitrite , activated sludge , nitrate , denitrification , nitrification , environmental chemistry , food science , nitrogen , environmental engineering , sewage treatment , organic chemistry , engineering
The goal of this research was to investigate the simultaneous occurrence of nitrification and denitrification by activated sludge exposed to volatile fatty acids (VFAs) during aerobic wastewater treatment using a single‐stage reactor. A mixture of VFAs was spiked directly into a continuous‐stirred tank reactor (CSTR) to assess subsequent impacts on nitrite removal, nitrate formation, CO 2 fixation, total bacterial density, and dominant nitrite oxidizing bacteria (NOB) concentration (i.e., Nitrospira ). The activity of the periplasmic nitrate reductase (NAP) enzyme and the presence of nap gene were also measured. A rapid decrease in the nitrate formation rate (>70% reduction) was measured for activated sludge exposed to VFAs; however, the nitrite removal rate was not reduced. The total bacterial density and Nitrospira concentration remained essentially constant; therefore, the reduction in nitrate formation rate was likely not due to heterotrophic uptake of nitrogen or to a decrease in the dominant NOB population. Additionally, VFA exposure did not impact microbial CO 2 fixation efficiency. The activity of NAP enzyme increased in the presence of VFAs suggesting that nitrate produced as a consequence of nitrite oxidation was likely further reduced to gaseous denitrification products via catalysis by NAP. Little, if any, nitrogen was discharged in the aqueous effluent of the CSTR after exposure to VFAs demonstrating that activated sludge treatment yielded compounds other than those typically produced solely by nitrification. Biotechnol. Bioeng. 2007; 97: 1562–1572. © 2007 Wiley Periodicals, Inc.