Nitrifier growth parameters—the maximum growth rate (μ Amax) and yield ( YA)—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 μ Amax values for the Nitrobacter and Nitrosomonas cultures were 0.67 ± 0.03 day −1 and
0.54 ± 0.09 day −1, while the YA values were 0.072 ± 0.01 g volatile suspended solids (VSS) · g nitrogen (N) −1 and 0.14 ± 0.02 gVSS · gN −1, respectively.
For the activated sludge sample, μ Amax was observed to increase with pH (μ Amax = 0.72 · 3.3 (pH-7.1)) over the range 6.8 to 7.1. All μ Amax and YA values determined
by this method were similar to those previously reported. Compared with other μ Amax and YA estimation methods, this method allows for unique μ Amax and YA estimations for given conditions
from a single experiment.
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