Dissolved Air Flotation Machine Food Factory Oil Sewage Treatment Equipment / DAF

Air flotation machine is a machine that uses small bubbles or small bubbles to surface impurities in the medium. This air flotation device can be used for small particles with a specific gravity close to that of water, which are difficult to sink or float due to their own weight.
In terms of water supply and drainage, the pre-treatment water quality, except for some raw water bodies with high sand content and sewage with heavy mechanical impurities, is mostly composed of lightweight suspended particles. For example, algae in lakes, reservoirs, and some rivers; Plant residues and small colloidal impurities; Dye particles in the printing and dyeing industry; Short fibers in the papermaking and chemical fiber industries; Microdroplets of petroleum and organic solvents in the refining and chemical industries; Heavy metal ions in electroplating and pickling wastewater; Electrophoretic paint wastewater, etc; They are lightweight particles with a specific gravity very close to that of water. For these raw water, if traditional sedimentation methods are used, the effect will inevitably be poor, especially in low temperature winter conditions, where coagulation and hydraulic conditions deteriorate, making it more difficult to ensure the treatment effect. It can be imagined that if it is difficult to settle flocs, forcing them to sink will inevitably result in half the effort. Instead, it is better to use the situation to artificially introduce bubbles into the water body, making them adhere to the flocs, thereby greatly reducing the overall density of the flocs, and using the speed of bubble rise to force them to float up, thus achieving rapid solid-liquid separation. In this sense, the emergence of air flotation technology is a revolution in the gravity sedimentation method, which has opened up new fields of solid-liquid separation technology.

Dissolved Air Flotation Machine for Food Factory Oil and Sewage Treatment

A Dissolved Air Flotation Machine (DAF) is an industrial wastewater treatment system designed to separate suspended solids, oil, grease, fats, colloidal particles, and other floatable contaminants from wastewater. It is widely suited for food factories, food processing plants, edible oil facilities, meat and poultry processing, dairy operations, seafood processing, and other industrial wastewater applications where conventional gravity separation may not provide sufficient performance.

The DAF process works by dissolving air into water under pressure and then releasing the pressure inside a flotation tank. The resulting microscopic bubbles attach to suspended particles and oil or grease droplets, causing them to rise to the surface. A mechanical skimmer removes the accumulated float material, while clarified water exits the flotation chamber. EPA technical documents describe DAF as a common process for removing suspended solids and dispersed oil and grease from industrial wastewater.

DAF for Food Factory Wastewater

Food factories can generate wastewater containing fats, oils, grease, proteins, food particles, fibers, suspended solids, organic matter, and other process residues. The wastewater characteristics can vary according to raw materials, production processes, cleaning operations, and water consumption.

A DAF wastewater treatment system can serve as primary treatment or pretreatment before biological treatment. By removing a substantial portion of suspended and floatable material, the system can reduce the pollutant load entering downstream biological reactors, filters, membranes, or other treatment units.

Typical food industry applications include:

Food Processing Wastewater
Meat Processing Wastewater
Poultry Processing Wastewater
Slaughterhouse Wastewater
Dairy Wastewater
Seafood Processing Wastewater
Vegetable Processing Wastewater
Fruit Processing Wastewater
Edible Oil Wastewater
Beverage Factory Wastewater
Food Packaging Wastewater
Rendering Plant Wastewater

EPA documentation for the meat and poultry industry identifies DAF as a primary treatment technology capable of removing suspended solids, fatty tissue, oils, grease, and other pollutants, and notes that it can also contribute to BOD and COD reduction.

How Does a Dissolved Air Flotation Machine Work?

A typical DAF system consists of a flotation tank, pressurizing pump, air injection or saturation system, pressure-release device, surface skimmer, sludge collection system, and associated controls. Larger installations may also include coagulation and flocculation tanks.

The wastewater first passes through preliminary treatment when necessary. Screening can remove larger food particles, fibers, packaging residues, hair, or other debris.

Depending on wastewater characteristics, coagulants and polymers may then be added. These chemicals destabilize colloidal particles and help form larger flocs that can be more effectively floated.

A portion of clarified water is commonly recycled and pressurized with air. When the pressurized recycle stream passes through the pressure-release device, dissolved air forms very small bubbles.

These bubbles attach to oil droplets, grease, suspended solids, and chemical flocs. The combined bubble-particle structures rise to the surface and form a floating sludge layer.

The surface skimmer continuously or intermittently removes this material into a sludge collection chamber. Clarified wastewater is collected from the flotation tank and discharged to the next treatment stage.

EPA describes this pressure-release mechanism as the basis of DAF, with microscopic bubbles attaching to oil and suspended particles and carrying them upward for surface removal.

Oil and Grease Removal

One of the major advantages of a DAF Oil Wastewater Treatment System is its ability to separate dispersed oil, grease, fats, and other low-density materials.

Oil and grease can be difficult to remove through conventional sedimentation because many droplets have a density close to or lower than water. DAF changes the separation mechanism by attaching air bubbles to these particles and accelerating their movement toward the water surface.

EPA technical documentation notes that DAF is commonly used to remove oil and grease from industrial wastewater and can be particularly useful for particles with densities close to that of water.

When chemical coagulation and flocculation are properly applied, oil and grease and suspended-solids removal can be improved. Actual removal performance depends on wastewater composition, particle characteristics, chemical dosage, hydraulic loading, air-to-solids ratio, temperature, and other operating parameters.

Suspended Solids Removal

Food factory wastewater can contain fine organic particles, proteins, fibers, soil, food residues, and other suspended materials.

DAF can separate many of these particles by flotation, particularly when they are light, hydrophobic, or chemically conditioned to form suitable flocs.

Removing suspended solids before biological treatment can help stabilize downstream processes and reduce solids loading on secondary treatment equipment.

For wastewater with heavier inorganic solids, screening or sedimentation may be installed before DAF. This creates a combined treatment process that handles different particle types according to their physical characteristics.

Coagulation and Flocculation

Coagulation and flocculation are optional but important components for many industrial DAF applications.

A coagulant destabilizes fine particles and colloids. A flocculant can then encourage these particles to form larger aggregates. The larger flocs provide more surface area for bubble attachment and are easier to float.

Common chemical systems may use aluminum- or iron-based coagulants and polymeric flocculants, but the correct chemicals and dosage must be determined from actual wastewater characteristics.

EPA documentation reports that chemical conditioning can improve DAF performance for suspended solids and oil and grease removal.

Main Features of DAF Sewage Treatment Equipment

A food factory DAF system can be configured with:

Dissolved Air Flotation Tank
Recycle Water Pump
Air Saturation System
Pressure Release Valve
Air Compressor
Coagulation Tank
Flocculation Tank
Chemical Dosing System
Surface Sludge Scraper
Bottom Sludge Collection
Sludge Discharge System
Automatic Control Cabinet
Flow And Pressure Monitoring

The system can be designed for continuous operation and connected with upstream screening, equalization, biological treatment, filtration, membrane treatment, sludge dewatering, and disinfection equipment.

Typical Food Factory Treatment Process

A complete food wastewater treatment plant may use a process such as:

Coarse Screening → Fine Screening → Equalization → pH Adjustment → Coagulation → Flocculation → DAF → Biological Treatment → Secondary Clarification → Filtration/MBR → Disinfection

The actual process should be selected according to wastewater flow, TSS, COD, BOD, oil and grease, pH, temperature, production schedule, discharge requirements, and water reuse objectives.

DAF is not normally intended to replace biological treatment where the wastewater contains substantial dissolved biodegradable organic matter. Instead, it is often used to reduce the particulate and floatable load before biological treatment.

Why Choose Us?

We provide DAF wastewater treatment solutions for food factories, industrial plants, and wastewater treatment projects. Our equipment can be configured according to actual influent conditions rather than relying only on nominal flow capacity.

For food factory applications, important design parameters include average and peak wastewater flow, suspended solids, oil and grease, COD, BOD, pH, temperature, wastewater variability, and required effluent quality.

We can supply standalone DAF units or integrate DAF with screening, equalization, chemical dosing, biological treatment, filtration, MBR, RO pretreatment, sludge dewatering, and disinfection systems.

For difficult wastewater streams, laboratory jar testing or pilot testing can help determine the appropriate chemical program and flotation conditions before final equipment selection.

Operation and Maintenance

Routine maintenance helps keep DAF equipment operating consistently. Operators should inspect the recycle pump, air saturation equipment, pressure-release components, skimmer, chemical dosing system, valves, gauges, and sludge discharge system.

The flotation surface should be monitored to prevent excessive accumulation of float sludge. The skimmer should operate smoothly and remove the collected material at an appropriate frequency.

Chemical dosage should be adjusted when food production processes or wastewater characteristics change. Periodic cleaning of the flotation tank, pipes, valves, pumps, and air-release components can also help maintain stable operation.

The separated sludge should be transferred to appropriate thickening or dewatering equipment according to its characteristics.

Frequently Asked Questions
1. What is a Dissolved Air Flotation Machine?

A DAF machine is a wastewater treatment device that uses microscopic air bubbles to float suspended solids, oil, grease, and other suitable contaminants to the water surface for removal.

2. Can DAF treat food factory wastewater?

Yes. DAF is widely applicable to food processing wastewater containing fats, oils, grease, suspended solids, proteins, and other floatable or particulate contaminants.

3. Can DAF remove oil and grease?

Yes. Oil and grease removal is one of the major applications of DAF wastewater treatment.

4. Can DAF remove suspended solids?

Yes. DAF can remove many suspended and colloidal solids, especially lighter particles and particles that have been chemically flocculated.

5. Is coagulation required before DAF?

Not always. However, coagulation and flocculation can improve performance when wastewater contains fine colloidal particles, emulsified oil, or difficult-to-float solids.

6. Can DAF reduce COD and BOD?

Yes, DAF can reduce the portion of COD and BOD associated with suspended, oily, or particulate organic matter. Dissolved biodegradable organics generally require additional biological treatment.

7. Can DAF replace biological wastewater treatment?

Usually not. DAF is commonly used as primary treatment or pretreatment before biological processes such as MBBR, SBR, activated sludge, UASB, or MBR.

8. What food industries use DAF?

Common applications include meat processing, poultry, dairy, seafood, edible oil, beverage, fruit and vegetable processing, and other food manufacturing facilities.

9. How is DAF capacity selected?

Capacity should be based on average and peak flow, wastewater characteristics, hydraulic loading, required removal performance, and downstream treatment requirements.

10. Can the DAF system be automated?

Yes. PLC-based automation can control pumps, valves, chemical dosing, skimming, sludge discharge, alarms, and other operating functions.

11. What happens to the DAF sludge?

The concentrated float sludge is collected and can be transferred to sludge thickening, dewatering, disposal, digestion, or other appropriate solids-handling processes.

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