Separation of pollutants from oil-containing restaurant wastewater by novel microbubble air flotation and traditional dissolved air flotation

Abstract

Novel microbubble air flotation (MAF) and traditional dissolved air flotation (DAF) systems were compared based on the separation ability of pollutants from oil-containing restaurant wastewater, which was used to verify the strengths of MAF system. The results showed that, when the operational parameters were a PAC dosage of 20 mg/L, reaction time of 15 min, operational pressure of 0.35 MPa, and reflux ratio of 25%, the removal efficiencies of oil, CODcr, and turbidity in MAF were 10.3%, 22.6%, and 15.0% higher than that in DAF, respectively. The maximum removal efficiencies of oil and turbidity in the MAF system were 98.0% and 97.5%. In addition, the minimum microbubble diameter in the MAF system was 20 μm under the operational pressure of 0.9 MPa, which could be successively and steadily produced. The maximum oil removal efficiency was achieved in the MAF system when the microbubbles and oil-droplets were similar sizes. Therefore, the application of the MAF technology could alleviate the pressure of downstream treatment of oil-containing wastewater.