english Sedimentation Dissolved Air Flotation (DAF) does possess the capability to remove oil, and this function is widely applied in wastewater treatment scenarios.
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Oil-Removal Mechanism
Its oil-removal mechanism relies on the interaction between tiny air bubbles and oil droplets in the water. During operation, air is dissolved in water under pressure, and when the pressure is released, a large number of fine, stable air bubbles are generated. These bubbles have strong affinity for oil droplets—since oil is hydrophobic, it easily attaches to the surface of the bubbles. As the bubbles rise to the water surface, they carry the oil droplets upward, forming a floating scum layer that can be skimmed off, thereby achieving oil separation from water.
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Effectiveness on Different Oil Types
The oil-removal effect of DAF varies with the type of oil. It performs well in removing dispersed oil and emulsified oil, which are common in industrial and domestic wastewater. Dispersed oil exists as small droplets suspended in water, and the bubbles can quickly capture these droplets. For emulsified oil, which is more stable due to surfactant action, DAF can still work effectively when combined with appropriate demulsifying agents—these agents break the emulsion structure, allowing oil droplets to aggregate and attach to bubbles more easily. However, for heavy oil with high density, the effect may be limited, as the density difference between heavy oil droplets and water is small, making it harder for bubbles to lift them to the surface; pre-treatment to reduce oil density or increase bubble buoyancy may be needed in such cases.
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Influence of Operating Conditions
Operating conditions also influence DAF's oil-removal performance. Adjusting the pH of the wastewater to a suitable range helps optimize the surface charge of oil droplets and bubbles, enhancing their adhesion. Temperature affects the stability of air bubbles—too low a temperature may reduce bubble activity, while excessively high temperatures can cause bubbles to burst prematurely, both of which weaken oil-removal efficiency. Additionally, adding flocculants can promote the aggregation of oil droplets into larger clusters, making them easier to be captured by bubbles, further improving the oil-removal rate.
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Practical Applications
In practical applications, DAF is often used to treat oil-containing wastewater from industries such as petroleum processing, food production, and mechanical manufacturing. After treatment, the oil content in the wastewater can be significantly reduced to meet discharge or reuse standards. This confirms that when properly designed and operated, DAF is a reliable and efficient technology for oil removal, with the flexibility to adapt to different oil-containing wastewater characteristics through parameter adjustments.
