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

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.