The effect of disk rotational speed on oxygen transfer in rotating biological contactors

Lab-scale experiments using a synthetic wastewater were carried out to assess the influence of disk rotational speed on oxygen transfer rate in a RBC unit in the presence of biomass. The overall oxygen transfer coefficient (KLa) was computed. Five different disk rotational speeds were tested, in the typical RBC operating range (3–10 RPM). The soluble organic substrate was monitored through TOC analysis. Influent hydraulic organic loadings were in the range of 5.4–35.2 g TOC/m2 d. The set of kinetic coefficients calculated fitting the experimental data by the selected model resulted in good agreement with the value reported in literature. A correlation for KLa as a function of disk rotational speed and disk diameter was obtained. Accordingly, a new expression of the enhancement factor of oxygen transfer was found, and compared to literature data.