| Analysis of Free Ammonia Inhibition of Nitrite Oxidizing Bacteria
Using a Dissolved Oxygen Respirometer |
| Dong-Jin Kim1†, Dong-Ig Lee1, Gi-Cheol Cha2, and Jürg Keller3 |
1Department of Environmental Sciences and Biotechnology, Hallym University, Chunchon, Korea
2Division of Environmental Engineering, Yonsei University, Wonju, Korea
3Advanced Water Management Centre, The University of Queensland, Brisbane, Australia |
Corresponding Author:
Dong-Jin Kim ,Tel: +82-33-248-2154, Fax: +82-33-256-3420, Email: dongjin@hallym.ac.kr
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Received: January 8, 2008; Accepted: June 7, 2008. |
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| ABSTRACT |
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Free ammonia (NH3-N) inhibition of nitrite-oxidizing bacteria (NOB) has been widely studied for partial nitrification (or nitrite accumulation)
and denitrification via nitrite (NO2
--N) as a low-cost treatment of ammonium containing wastewater. The literature on NH3-N inhibition of NOB,
however, shows disagreement about the threshold NH3-N concentration and its degree of inhibition. In order to clarify the confusion, a simple and
cheap respirometric method was devised to investigate the effect of free ammonia inhibition of NOB. Sludge samples from an autotrophic nitrifying
reactor were exposed to various NH3-N concentrations to measure the maximum specific nitrite oxidation rate (KNO
) using a respirometer. NOB
biomass was estimated from the yield values in the literature. Free ammonia inhibition of nitrite oxidizing bacteria was reversible and the specific
nitrite oxidation rate (KNO) decreased from 0.141 to 0.116, 0.100, 0.097 and 0.081 mg NO2
--N/mg NOB․h, respectively, as the NH3-N concentration
increased from 0.0 to 1.0, 4.1, 9.7 and 22.9 mg/L. A nonlinear regression based on the noncompetitive inhibition mode gave an estimate of the
Inhibition concentration (KI) of free ammonia to be 21.3 mg NH3-N/L. Previous studies gave KNO
of Nitrobacter and Nitrospira as 0.120 and 0.032
mg/mg VSS․h. The free ammonia concentration which inhibits Nitrobacter was 30 ~ 50 mg NH3-N/L and Nitrospira was inhibited at 0.04 ~ 0.08
mg NH3-N/L. The results support the fact that Nitrobacter is the dominant NOB in the reactor. The variations in the reported values of free ammonia
inhibition may be due to the different species of nitrite oxidizers present in the reactors. The respirometric method provides rapid and reliable
analysis of the behavior and community of the nitrite oxidizing bacteria. |
| Keywords:
Free ammonia inhibition | Nitrification | Nitrite-oxidizing bacteria | Respirometer |
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