Estimation of oxygen effective diffusion coefficient in a non-steady-state biofilm based on response time

In wastewater treatment, oxygen effective diffusion coefficient (D _eff ) is a key parameter in the study of oxygen diffusion-reaction process and mechanism in biofilms. Almost all the reported methods for estimating the D _eff rely on other biokinetic parameters, such as substrate consumption rate and reaction rate constant. Then, the estimation was complex. In this study, a method independent of other biokinetic parameters was proposed for estimating the dissolved oxygen (DO) D _eff in biofilms. It was based on the dynamic DO microdistribution in a non-steady-state inactive biofilm, which was measured by the oxygen transfer modeling device (OTMD) combining with an oxygen microelectrode system. A pure DO diffusion model was employed, and the expression of the DO D _eff was obtained by applying the analytical solution of the model to a selected critical DO concentration. DO D _eff in the biofilm from the bioreactor was calculated as (1.054 ± 0.041) × 10^-9 m²/s, and it was in the same order of magnitude with the reported results. Therefore, the method proposed in this study was effective and feasible. Without measurement of any other biokinetic parameters, this method was convenient and will benefit the study of oxygen transport-reaction process in biofilms and other biofouling deposits. Graphical abstract ᅟ.