Cyclonic state micro-bubble flotation column in oil-in-water emulsion separation

• A novel flotation column was developed to enhance oily wastewater separation.
• The flotation column combines a column separator with a cyclonic separator.
• An oil removal of 92.19% was obtained with feed oil droplet size of 25.01 μm.
• The flotation column has higher oil removal than DAF column for fine oil droplets.

In order to improve the separation efficiency of oil-in-water emulsion, a novel cyclonic state micro-bubble flotation column was developed to enhance the separation efficiency. The flotation column comprises a column separator and a cyclonic separator provided on the bottom plate of the flotation apparatus. The process parameters, namely the feed volume flow rate, initial oil concentration, aeration rate, and oil droplet size on removal efficiency were investigated. The process efficiencies between the cyclonic state micro-bubble flotation column (FCSMC) and dissolved air flotation column (DAF) were compared. Results show that this FCSMC has higher oil removal efficiency and treated water with lower oil levels than the DAF, especially for the process of fine oil droplets (<10 μm). An oil removal efficiency of 92.19% was obtained with the treated wastewater effluent containing a final oil concentration of 37.10 mg/L using FCSMC (an oil removal efficiency of 76.65% with a final oil concentration of 110.92 mg/L using DAF) under conditions as following: a 18.75 min of residence time, a 475.05 mg/L of initial oil concentration, a 1.8 L/min of aeration rate and a 25.01 μm of mean oil droplet size in feed. The mean oil droplet size is 1.84 μm with 4.81% of the oil droplets above 5 μm in diameter in the treated effluent. It shows that the FCSMC is especially advantageous for the separation of fine oil droplets.

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