A new form of self-rotating biological contactors (sRBC) was used in the present study which was free rotating discs (without any mechanical power). A comparison of various reported models in the literature for computing volumetric oxygen transfer coefficient (KLa) has been done. The models were evaluated namely, Friedman et al. (1979), Sant’ Anna (1980), Kim and Molof (1982), Kubsad et al. (2004) and Chavan and Mukherji (2008). Self-RBC oxygen model was established in the present study based on dimensional analysis by performing non-linear regression for 45 runs of the experimental values. This model was expressed as a function of rotational speed (ω), disc diameter (ɸ) and area of discs (Ad). Increasing of rotational speed (ω) and disc diameter (ɸ), increase KLa. Regression coefficient (R2) obtained is 0.99. Two empirical models were also derived based on Sant’ Anna (1980) and Chavan and Mukherji (2008) models, where has regression coefficient (R2) 0.987 and 0.965 respectively. Results indicated that the proposed models provide a good fitting and correlation for a wide range of reactor design parameters and operating conditions as reported in the present study from the variation in flow rate, % of disc submergence in water and reactors size. These proposed empirical models will facilitate scale-up of sRBC discs. Due to the flow of water, revolution per minute (rpm) of sRBC disc occurs. Then, non-dimensional rpm formula was estimated as a function of flow rate, diameter and area of disc, working volume, area of tank and immersion factor. Regression coefficient (R2) is 0.994. Predicted values