Regular articleEffect of nitrifiers enrichment and diffusion on their oxygen half-saturation value measurements

- The measured values of KO,AOB and KO,NOB were low under small floc diameter and low nitrifiers enrichment condition.
- The nitrifiers enrichment and floc diameter had higher impact on the KO,AOB measurement than on the KO,NOB measurement.
- The results explained the conflicting reports on the measured KO,AOB and KO,NOB values in the literatures.

It has been recognized that the size of activated sludge floc affected the measurement of substrate half-saturation value. The impact of bacteria enrichment on the half-saturation value measurement has not been studied. This study highlighted the importance of bacteria enrichment on the evaluation of the half-saturation values. Due to the critical importance of oxygen half-saturation value in achieving partial nitrification, the impact of floc diameter and nitrifier enrichment on the measurement of oxygen half-saturation value for AOB (KO,AOB) and NOB (KO,NOB) was evaluated both in experiment and in mathematical simulation. The experiment results showed low measured KO,AOB and KO,NOB values under small floc diameter and low nitrifiers concentration condition. The increase in floc diameter and nitrifiers enrichment caused a significant increase in the measured KO,AOB, while only slight increase in KO,NOB was noticed. The simulation results were consistent with the experiment results and indicated that the nitrifiers concentration and the floc diameter had higher impact on the KO,AOB measurement than on the KO,NOB measurement. The results could explain the conflicting reports on the measured KO,AOB and KO,NOB values.

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