The subject of the research involves a rotating biological contractor with a bi-directional longitudinal flow as an element of a synchronized system of disposal and biological treatment of domestic wastewater in small-bore sewerage. The rotor design is based on a system of corrugated protective pipes, arranged in coils wound around its rotation axis. The pipes are wound in a way that enables a bi-directional flow of liquids. During the rotor rotation in wastewater, the contactor is simultaneously emptied and filled with wastewater. The role of corrugated protective pipes is twofold; on the one hand, they constitute a surface for the biofilm development and on the other, they enable the flow of liquids, thus ensuring its aeration. The contactor design aims to achieve intensive aeration of transported wastewater, which will allow for greater development of microorganism populations participating in hybrid wastewater treatment, i.e. the methods involving activated sludge and trickling filter. An analysis on the influence of rotor operation kinematics on the efficiency of liquid aeration was conducted. The aeration capacity for variable rotational speed (0.7 rpm, 1.5 rpm, 2.0 rpm, 3.0 rpm) and direction of the contactor rotating element were calculated. In the considered case, oxygen transfer coefficient KLa was within the range of 0.011÷0.023 1/min. The obtained results indicate a clear connection between the system kinematics and the degree of liquid aeration in the contactor.