Application Instructions of Air Flotation Sedimentation Integrated Unit in Sewage Treatment

The dissolved air flotation (DAF) sedimentation integrated unit is a water treatment equipment that efficiently combines flotation and sedimentation processes. Through dual mechanisms of "microbubble flotation separation" and "gravity sedimentation," it achieves rapid removal of pollutants such as suspended solids, oils, and colloids from wastewater. The effluent suspended solids (SS) can be reduced to below 20 mg/L, with an oil removal rate exceeding 95%.

Based on a "one-unit, dual-function" design, the front-end DAF unit utilizes a dissolved air system to pressurize and dissolve air into water, releasing 20-50 μm microbubbles that adsorb hydrophobic pollutants (e.g., oil droplets, algae) and float them to the surface for collection by a skimming device. The rear-end sedimentation unit employs inclined tube modules to increase the settling area, enabling dense solid particles (e.g., sand, metal hydroxides) to quickly sink and be discharged through a sludge removal system. This synergistic process achieves "flotation for scum removal and sedimentation for heavy pollutant removal," making it suitable for pretreatment and advanced purification of oily wastewater and high-suspended-solid wastewater.

The main body of the equipment is constructed from corrosion-resistant carbon steel or stainless steel, integrating a dissolved air tank, flotation reaction zone, inclined tube sedimentation zone, skimming system, and automatic control unit. Its compact structure (40% smaller footprint compared to traditional separate systems) enables fully automated operation from "influent to treated effluent." The dissolved air system uses a high-efficiency jet dissolved air pump (dissolution efficiency ≥90%) paired with an intelligent pressure sensor (controlled pressure 0.3-0.5 MPa) to ensure stable microbubble generation. Coagulants (e.g., PAC) and flocculants (PAM) are dosed in the flotation reaction zone, where a mixing device forms "bubble-floc" complexes to enhance flotation efficiency. The sedimentation zone features 60° inclined polypropylene tubes (80 mm diameter) with a surface loading rate of 8-10 m³/(m²·h), reducing solid-liquid separation time to 15-20 minutes.

Equipped with a PLC control system, the unit monitors parameters such as influent flow rate, dissolved air pressure, and liquid level in real time, automatically adjusting chemical dosing and skimming frequency while supporting remote monitoring and fault alerts to reduce manual intervention costs. Compared to traditional separate flotation and sedimentation systems, the integrated unit offers significant advantages of "high efficiency, space savings, and low energy consumption." The flotation unit removes hydrophobic particles ≥1 μm through efficient microbubble adsorption, achieving over 90% removal of emulsified oils (e.g., oil droplets in machining wastewater), while the sedimentation unit removes over 95% of inorganic particles with density ≥1.2 g/cm³ (e.g., metal oxides). Their synergy improves overall treatment efficiency by 30% compared to conventional processes. Energy consumption is minimized with dissolved air pump power of only 0.75-2.2 kW (for treatment capacity of 5-50 m³/h) and an intermittent skimming system (operating 5 minutes every 30 minutes), reducing electricity consumption to 0.1-0.2 kW·h per ton of water treated, saving 25% energy compared to separate systems.

Additionally, the unit features a fully enclosed structure with auxiliary exhaust gas collection (e.g., activated carbon adsorption) to prevent volatile emissions during flotation, complying with environmental standards. It is widely used in industrial wastewater pretreatment (e.g., petrochemicals, machining, food and beverage industries), oil separation in餐饮 wastewater, municipal wastewater upgrading, and emergency treatment of black and odorous water bodies. For petrochemical wastewater, it removes emulsified oils (effluent ≤10 mg/L when influent oil content is 200 mg/L) and suspended solids (SS reduced from 500 mg/L to 30 mg/L), creating favorable conditions for subsequent biological treatment.

In餐饮 wastewater treatment, the front-end flotation unit rapidly separates oils (95% removal rate), while the rear-end sedimentation removes food residues, ensuring effluent meets the "Water Quality Standard for Discharge to Municipal Sewers" (GB/T 31962). For emergency river treatment, the unit can be mobile (vehicle-mounted design), quickly treating high-turbidity water (turbidity reduced from 200 NTU to below 15 NTU) to improve water clarity.

For varying water qualities, the unit allows flexible adjustment of process parameters: for high-concentration oily wastewater, increase dissolved air pressure (0.5 MPa) and PAC dosage (50-80 ppm); for high inorganic suspended solids, enhance sludge discharge frequency in the sedimentation zone (once per hour) to ensure stable treatment performance.

In terms of operation and maintenance, the design emphasizes convenience and durability: the dissolved air tank includes anti-clogging nozzles (2 mm aperture) with regular backwashing (weekly) to prevent scaling; the skimming device uses stainless steel chain drives (5+ years lifespan) with overload protection sensors to avoid jamming; inclined tubes in the sedimentation zone are detachable for cleaning (annually) to prevent sludge accumulation affecting efficiency. Daily operation only requires periodic chemical replenishment, checking dissolved air pump lubricant levels, and cleaning sludge discharge pipes, significantly reducing maintenance efforts. Economically, a single unit costs 80,000-500,000 RMB (treatment capacity 10-200 m³/h), with operating costs of 0.3-0.8 RMB/ton (including electricity and chemicals), and a lifespan exceeding 10 years. It is particularly suitable for small-to-medium enterprises and decentralized wastewater treatment scenarios, achieving multiple goals of "efficient treatment, low operational costs, and rapid compliance."