Description:
Nitrifier growth parameters-the maximum growth rate ( $\mu _{Amax}$ ) and yield ( $Y_{A}$ )-were estimated by measuring the rate of carbon dioxide uptake and additional rates of oxygen uptake and ammonia (or nitrite) use. Batch tests in a combined titrimetric and offgas analyzer with enriched Nitrobacter and Nitrosomonas cultures and an activated sludge sample were performed. The measured $\mu _{Amax}$ values for the Nitrobacter and Nitrosomonas cultures were 0.67 ± 0.03 $\text{day}^{-1}$ and 0.54 ± 0.09 $\text{day}^{-1}$ , while the $Y_{A}$ values were 0.072 ± 0.01 g volatile suspended solids (VSS)·g nitrogen $({\rm N})^{-1}$ and 0.14 ± 0.02 ${\rm gVSS}\cdot {\rm gN}^{-1}$ , respectively. For the activated sludge sample, $\mu _{Amax}$ was observed to increase with pH ( $\mu _{Amax}=0.72\cdot 3.3^{({\rm pH}\text{-}7.1)}$ over the range 6.8 to 7.1. All $\mu _{Amax}$ and $Y_{A}$ values determined by this method were similar to those previously reported. Compared with other $\mu _{Amax}$ and $Y_{A}$ estimation methods, this method allows for unique $\mu _{Amax}$ and $Y_{A}$ estimations for given conditions from a single experiment.