The core technology of Oily Wastewater Treatment Equipment utilizes multi-stage processes including physical, chemical, and biological methods to efficiently separate and remove floating oil, dispersed oil, emulsified oil, and dissolved oil from wastewater, meeting environmental emission standards or reclaimed water reuse requirements. The mainstream technology has formed a mature system of "pretreatment – ​​main treatment – ​​advanced treatment."

I. Core Technology Principles and Equipment

1. Physical Separation Technology (Pretreatment / Main Treatment)

(1) Gravity Separation

Principle: Utilizing the density difference between oil (density approximately 0.9–0.95 g/cm³) and water (1.0 g/cm³), oil droplets are allowed to float naturally through settling.

Typical Equipment: API oil separator, CPI inclined plate oil separator. CPI shortens the separation path by adding 60° inclined corrugated plates, achieving an efficiency 5 times higher than traditional API. Applications: Removal of floating oil (particle size > 100μm), efficiency approximately 70–90%, as primary pretreatment.

(2) Coalescence Separation
Principle: Utilizing oleophilic and hydrophobic materials (such as polypropylene, fiber balls), tiny oil droplets (<10μm) are adsorbed and collided on the material surface, coalescing into larger droplets that then float.

Typical Equipment: Coalescer, corrugated plate separator.

Applications: Processing dispersed oils and weakly emulsified oils, often combined with gravity separation.

(3) Air Flotation
Principle: Generating microbubbles (20–50μm) that adhere to oil droplets and suspended matter, causing them to float rapidly, forming scum that is then scraped off.

Main Types:
Dissolved Air Flotation (DAF): Most commonly used, producing fine bubbles with stable results, suitable for emulsified oils.

Cavity Air Flotation (CAF): Simple equipment, low energy consumption, but produces coarser bubbles. **Cyclone-type dissolved air flotation (CDFU):** Combining cyclone and air flotation, residence time < 5 minutes, efficiency 3–8 times that of traditional dissolved air flotation (DAF).

(4) Centrifugal Separation

Principle: High-speed rotation generates 200–1000G centrifugal force, forcing oil-water separation.

Equipment: Centrifuge, cyclone separator.

Features: Extremely small footprint, extremely high efficiency, but high energy consumption and maintenance costs; suitable for high concentration, low flow rate scenarios.

2. Membrane Separation Technology (Fine/Deep Treatment)

Principle: Utilizing semi-permeable membranes such as **ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO)** to precisely retain tiny oil droplets (<0.01μm), colloids, and organic matter.

Features: Extremely high effluent quality (oil content <5mg/L), directly reusable; however, membranes are prone to fouling and costs are high.

3. Chemical and Physicochemical Technologies

Demulsification: Adding acids, alkalis, salts, or demulsifiers disrupts the stability of emulsified oil, releasing oil droplets.

Coagulation: Adding PAC or PAM causes oil droplets and suspended solids to flocculate into large precipitates.

Adsorption: Using activated carbon or zeolite to adsorb dissolved oil and color for deep purification.

4. Biological Treatment Technologies (Organic Oily Wastewater)

Principle: Utilizing aerobic/anaerobic microorganisms to degrade oily organic matter (such as petroleum hydrocarbons) into CO₂ and H₂O.

Processes: SBR, biological contact oxidation, MBR membrane bioreactor.

Applicable to: Low-concentration, biodegradable oily wastewater (such as food processing and domestic sewage). II. Typical Process Flow (Industrial Grade)

Pretreatment: Bar screen → Equalization tank → Oil separator (removing floating oil)

Main treatment: Demulsification + coagulation → Air flotation (removing emulsified oil)

Advanced treatment: Filtration / Ultrafiltration (UF) → Activated carbon adsorption / RO → Discharge meeting standards / Reuse

III. Key Points for Technology Selection

Oil form: Floating oil → Gravity; Emulsified oil → Air flotation / Demulsification; Dissolved oil → Membrane / Adsorption / Biological treatment.

Water concentration: High concentration → Centrifugation / Gravity; Medium to low concentration → Air flotation / Biological treatment.

Effluent requirements: Direct discharge → Air flotation + filtration; Reuse → Membrane separation (UF/RO).

Cost: Gravity / Air flotation (low) → Biological treatment (medium) → Membrane separation (high).