[Effect of Temperature on the Activity Kinetics of Nitrobacter].

A sequencing batch reactor (SBR) was operated in this study to investigate the effect of temperature on the kinetics of Nitrobacter activity among nitrite oxidizing bacteria. At the beginning of the experiment, the NO2--N concentration in the influent was changed to enrich Nitrobacter. Then, the sludge with enriched Nitrobacter was employed to determine the variation of the specific nitrite oxidation rate (SNiOR) during the nitrite oxidation process in batch tests. Metagenomics species annotation and abundance analysis showed that Nitrobacter accounted for 40.3% of the total bacterial population. The variation of SNiOR in the nitrite oxidation process was investigated under different NO2--N concentrations. The effect of temperature on the kinetics of Nitrobacter was investigated using the Monod model. Furthermore, the kinetics model of the effect of temperature on Nitrobacter activity was fitted for statistical analysis. The results showed that SNiOR reached its maximum at 30℃, which was 1.31 g·(g·d)-1. Statistical analysis showed that the Monod equation could describe the effect of substrate concentration on Nitrobacter activity under different temperature conditions. Calculating the temperature coefficient (θ) in different temperature intervals based on the Phelps equation, showed that when the system temperature is lower than 25℃ or higher than 30℃, the reaction rate is more sensitive to temperature changes.

[Inhibitory Kinetics of Free Ammonia (FA) on Ammonia-oxidizing Bacteria (AOB)].

In this study, a sequencing batch reactor (SBR) was operated to investigate the inhibitory kinetics of free ammonia (FA) on ammonia-oxidizing bacteria (AOB). At the beginning of the experiment, FA concentrations in influent were altered to achieve stable short-cut nitrification and enrich AOB. Nitritation sludge was then employed to study variations in the specific nitrite production rate (SNiPR) during the ammonia oxidation process of batch tests. Furthermore, a kinetic model of FA inhibition on AOB activity was fitted for statistical analysis. Results showed that SNiPR increased rapidly with increase in FA concentration (0.7 mg·L-1 ≤ FA ≤ 50.2 mg·L-1) but decreased with an increase in FA concentration (FA ≥ 50.2 mg·L-1). SNiPR was maintained at 0 g·(g·d)-1 when FA concentration was higher than 687.1 mg·L-1, implying that AOB activity was completely inhibited. Statistical analysis showed that, compared to Haldane, Edwards-1#, Edwards-2#, and Luong inhibition kinetics models, the Aiba model was the most suitable for describing the inhibitory effect of FA on AOB activity. The statistical constants, i.e., residual square sum (RSS) correlation coefficient (R2), F value of the fitting equation, and confidence degree (P) were 0.005, 0.932, 181.7, and 1.06×10-9, respectively. The dynamic constant values, i.e., maximum specific nitrite production rate (rmax), half saturation constant (KS), and inhibition constant (KI) were 0.37 g·(g·d)-1, 11.78 mg·L-1, and 153.74 mg·L-1, respectively.