Pretreatment Of Oil-Bearing Kitchen Wastewater With A New Microbubble Air Flotation Technology

A new kind of aeration equipment of microbubble was introduced for microbubble air flotation in this paper. The purpose of the research is to make this microbubble air flotation become a highly effective pretreatment equipment for oil-bearing wastewater. The advantages in technic, efficiency, cost and investment of microbubble flotation and mechanism were studied.The contrast experiments of the new microbubble air flotation and traditional dissolved air flotation (DAF) in the dosage of coagulant, hydrodynamic residence time (HRT), pressure and regurgitant were conducted in this research. The best dosage of PAC of the new microbubble air flotation and traditional dissolved air flotation is 20mg/L and 60mg/L. The best HRT of the two systems were same (15min), but 98.99% of oil, 97.77% of turbidity and 83.4% of COD could be removed by the new microbubble air flotation contrast to 87.41%, 81.36%, and 64.6% by traditional dissolved air flotation. When pressure and regurgitant is increasing, the new microbubble air flotation and traditional dissolved air flotation both have a trend of increase in disposal efficiency. The economic and technical analysis was conducted, it was indicated that the new microbubble air flotation (9.39 yuan/hundred ton) had the lower operating cost than traditional dissolved air flotation (19.64 yuan/hundred ton). Moreover, the new microbubble air flotation system is less invested and has a lower rate of malfunction.The connection of pressure, bubble size, oil bubble size and flocculation size were studied. The results were those: The higher pressure, the smaller bubble size, the more concentrated extension of bubble particle size distribution. When pressure is 0.9MPa, the mass bubble diameter of microbubble air flotation is less than 20μm. The mass oil bubble size of simulated kitchen wastewater is between 3~30μm, and the oil bubble below 10μm size account for 73.38%. The relation of bubble size and oil bubble size is that when oil bubble size is close to bubble size, the oil disposal efficiency is best. At low dosage of coagulant, flocculation was small and close-grained. Microbubble air flotation can conglutinate small flocculation comparing with traditional dissolved air flotation.In conclusion, when microbubble air flotation treats oil-bearing wastewater, the system has excellencies of high oil disposal of wastewater, low investment, low medicament cost, simple manipulate, low rate of malfunction, etc, so this microbubble air flotation can be a highly effective pretreatment equipment for oil-bearing wastewater.