Abstarct: This research was carried out with the goal of experimental investigation of Micro-Nano bubbles (MNBs) impact on improving the aerobic treatment of wastewater taken from Shahrood swage facilities. At the first step, the production methods and characteristics of MNBs were studied. The water enriched with MNBs using a generator made by Minab Toos Co. (Model T2S1-375, registration No. 83998). To compare the oxygen concentrations and other properties of water enriched with MNBs versus the conventional ceramic aerator, some preliminary tests were performed. The result showed that volumetric oxygen transfer coefficient in MNB system was approximately 7 times more than ceramic aerator. The reason behind this, could be size of bubbles and gas solution in MNBs. Furthermore, it was shown that MNBs are more stable than the bubbles generated from ceramic aerators. Other qualitative experiments on wastewater of Shahrood refinery showed that BOD5, COD, TDS, EC and turbidity in the treated wastewater by MNBs were less than ceramic aerator system samples. It should be noted that the pH in both samples were almost equal in the wastewater treated samples while pH in water with MNBs was higher than those from ceramic aerator.