english Shallow Air Flotation (SAF) is widely used in wastewater treatment for its high efficiency in separating oils, grease, and suspended solids. The oil removal rate of SAF units typically ranges between 90% to 98%, depending on several key factors:
1. Key Factors Affecting Oil Removal Efficiency
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Oil Type & Concentration:
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Free-floating oils (e.g., mineral oils) are easier to remove (95–98%).
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Emulsified oils require chemical pretreatment (coagulants like PAC or polymers) to achieve 85–95% removal.
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Bubble Size & Distribution:
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Microbubbles (30–100 µm) enhance oil adhesion, improving removal rates.
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Properly tuned dissolved air pressure (4–6 bar) ensures optimal bubble generation.
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Hydraulic Loading Rate:
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Surface loading rates of 2–5 m³/(m²·h) balance efficiency and throughput. Higher rates may reduce oil separation.
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Chemical Aids:
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Adding demulsifiers (e.g., 10–50 ppm) breaks oil emulsions, boosting removal by 10–20%.
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2. Performance Benchmarks
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Industrial Wastewater:
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Food processing (fats/oils): 90–97% removal.
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Petroleum refineries: 85–95% (with pretreatment).
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Municipal Wastewater:
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Restaurant grease traps: 92–96% removal.
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3. Optimization Techniques
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Adjustable Weirs: Control skimming depth to optimize floated oil layer removal.
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Polymer Addition: Enhances floc formation (e.g., 1–5 ppm anionic polymers).
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Regular Maintenance: Cleaning nozzles and diffusers prevents clogging, sustaining efficiency.
4. Limitations
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High surfactant content can reduce efficiency by stabilizing oil droplets.
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Cold temperatures (<10°C) may slow separation.
