Kinetics of Ammonia Removal from Waste Water by Air Flow

By comparing their result and the experimental data, the authors of ref 1 find that β decreases with the total air flow rate but is independent of other control parameters such as pH of the solution, temperature, and the submerged airflow rate. However, the authors didn't provide any explanation about the dependence of saturation factor β on the total air flow rate. The other assumption in ref 1 is that the aqueous ammonia molecules NH₃ (aq) are in chemical equilibrium with the ammonium ions NH⁺₄ (aq) in the solution throughout the ammonia removal process. With use of these assumptions, the authors could derive a simple approximate solution that could provide a quantitative description of the experimental data reported in ref 1. In this note, we present the standard mass action law describing the kinetics of the ammonia removal process and find the exact solution of the kinetic equations without making the two assumptions assumed in ref 1. In addition, we show that the approximation invoked in eq 1 is, in fact, equivalent to the steady-state approximation often used in the conventional chemical kinetics. Furthermore, we establish the quantitative relationship between β and the rate of total air flow, which provides the clear explanation about the previously unexplained dependence of β on the total air flow rate shown in Figure 7 of ref 1. From the comparison to the exact solution, we define the application range of the assumptions assumed in ref 1