A critical comparison of extant batch respirometric and substrate depletion assays for estimation of nitrification biokinetics

Abstract

Estimation of nitrification biokinetics has been conducted using different batch techniques via measurement of nitrogen species or surrogates such as oxygen (respirometry). However, there are no reports that specifically compare kinetic parameters estimated from respirometry with those from direct nitrogen species measurements. In this study, we evaluated the ability of parameter estimates from isolated and optimally designed complete extant respirometric assays to describe concurrently obtained ammonia and nitrite depletion profiles. Additionally, we mapped the different parameter sets to steady-state bioreactor performance. Using multivariate analysis of variance, we found that estimates from respirometric and substrate depletion assays were predominantly statistically different at the 95% confidence level. The sensitivity of predicted stead-state nitrifying reactor performance to differences in parameter estimates was highest close to the limiting solids retention time (SRT). However, at characteristic nitrifying SRTs the predicted reactor performance using parameter estimates from respirometry and substrate depletion assays were in very close correspondence. Therefore, parameters estimated from extant respirometric assays can be used to adequately predict nitrifying reactor performance.

Respirometric Microbioreactors for Biokinetic Estimation of Nitrification Activity

“…4). This range is in good agreement with values in literature [6]. Notably, the µ max and K S values were completely un-correlated, suggesting a significant improvement in the quality and practical identifiabiity of the parameter estimates obtained, as described previously [2].…”

“…Fitting of real-time online respirometric profiles (dissolved oxygen vs time) obtained in response to short-term ammonia or nitrite spikes results in estimates of the maximum specific growth rate (µ max ), the half-saturation coefficient (K S ), the specific decay coefficient (b) and the biomass yield coefficient (Y) [1][2][3][4] and also to quantify the impact of different stressors and stimuli such as toxicity, low dissolved oxygen, nitrite or ammonia on nitrifying bacteria [5][6][7]. Typically respirometry is carried out in batch vessels with a working volume in the range 50 -100 mL.…”

Strategies of Nitrosomonas europaea 19718 to counter low dissolved oxygen and high nitrite concentrations

“…However, the lag phase at DO = 0.5 mg O 2 /L was one day longer than at DO = 1.5 or 3.0 mg O 2 /L pointing to the impact of electron acceptor limitation on the cell synthesizing machinery of N. europaea (Figure 2, A2-C2). Estimates of the maximum specific growth rate (obtained via non-linear estimation [14]) at DO = 0.5 mg O 2 /L (0.043 ± 0.005 h -1 ), 1.5 mg O 2 /L (0.057 ± 0.012 h -1 ) and 3.0 mg O 2 /L (0.060 ± 0.011 h -1 ) were not statistically different at α = 0.05. At all three DO concentrations tested, low levels of NH 2 OH transiently accumulated in the growth medium during the exponential phase, in keeping with its role as an obligate intermediate of NH 3 oxidation [5] (Figure 2, A1-C1).…”

Activated Sludge – 100 Years and Counting

“…Expanding upon this work, Nowak et al (1995) and Chandran (Chandran & Smets, 2000Chandran et al, 2008) developed two-step approaches for mathematically describing the process of nitrification that considered the growth dynamics of AerAOB and NOB separately and allowed for a more realistic representation of the nitrifier microbial consortia.…”