Nitrification at low levels of dissolved oxygen with and without organic loading in a suspended-growth reactor

Origin, causes and effects of increased nitrite concentrations in aquatic environments

“…In other words, oxygen deficiency due to low DO more significantly influences the activity of NOB than that of AOB (Leu et al 1998). This was nicely illustrated by Hanaki et al (1990b) (Figure 5). According to Hunik et al (1994) the half-saturation constant for O 2 is 0.16 mg O 2 L −1 and 0.54 for Nitrosomonas europaea and Nitrobacter agilis respectively.…”

“…Together with unaffected ammonia oxidation this resulted in accumulation of nitrite to 60 mg N L −1 (Hanaki et al 1990b). Moreover, according to Hanaki et al (1990b) these low DO levels even result in higher (doubled) growth yields of AOB while the growth yield of NOB was unchanged, which can possibly give rise to increased nitrite concentrations.…”

“…Together with unaffected ammonia oxidation this resulted in accumulation of nitrite to 60 mg N L −1 (Hanaki et al 1990b). Moreover, according to Hanaki et al (1990b) these low DO levels even result in higher (doubled) growth yields of AOB while the growth yield of NOB was unchanged, which can possibly give rise to increased nitrite concentrations. Experiments by Laanbroek et al (1994) resulted in yields of Nitrosomonas europaea at oxygen concentrations of 0 and 80% air saturation equal to 13.8 and 6.6 10 12 cells mol −1 NH + 4 respectively, which also implies more than a doubling of the growth yield for low DO levels.…”

“…However, AOB seem to be more robust towards low DO than NOB. Accumulation of nitrite at low DO is usually explained by the difference in saturation constant in terms of DO (K 0 ) between AOB and NOB (Hanaki et al 1990b). In other words, oxygen deficiency due to low DO more significantly influences the activity of NOB than that of AOB (Leu et al 1998).…”

“…Studies on nitrifying biofilms as a model for riverbeds indicate a critical temperature domain (16-22 • C) in which the activity of NOB seems to be more inhib- (----), on ammonia and nitrite oxidation in pure cultures of nitrifying bacteria after reaching steady state conditions for various hydraulic retention times (HRT) (after Hanaki et al 1990b). ited than the nitritation by AOB (Von Der Wiesche & Wetzel 1998). A modelling analysis on data collected from a nitrogen polluted lake (Gelda et al 1999) demonstrated that the distinct seasonal differences in NO − 2 , i.e., peak nitrite concentrations over the July to October interval (summer) compared to the rest of the year, are largely the result of differences in rate and temporal patterns of the two stages of nitrification.…”