Paper industry
Recovery and reuse of white-water pulp.
Confirm fibre loading, recycle objectives and downstream water-quality requirements.
Wastewater solid-liquid separation
Dissolved Air Flotation System
A QF-series combined dissolved air flotation system for separating suspended solids, oil, colour-bearing matter and other floatable material from industrial wastewater.
- QF-series horizontal-flow configuration
- 0.3-0.5 MPa working-pressure reference
- 20-30 μm bubble-diameter reference
- Clarified-water recycle and automatic skimming
Product overview
Integrated Flotation for Industrial Wastewater Clarification
A product-level view of the equipment duty, process position and functional zones.
The QF series is a combined flotation unit for solid-liquid separation where fine suspended matter has a density close to water. Its treatment scope includes suspended solids, oil and colour-bearing material in wastewater.
A portion of clarified water is recirculated through the dissolved-air system. After pressure release, microbubbles attach to conditioned flocs in the contact zone. The bubble-floc complexes rise in the separation zone, where the surface layer is removed by the skimmer and clarified water leaves through the collection system.
QF model capacities, power, dimensions, weight and construction grades require an approved project data sheet before equipment selection.
For an independent explanation of pressure release, fine-bubble formation and bubble-assisted separation, see the U.S. EPA dissolved air flotation fact sheet (PDF). This historical source supports the stable process principles described above, not current costs or KUOSI performance guarantees.
Functional mapEquipment-level view
- 01
Conditioning and mixing
Receives wastewater and the selected coagulant or flocculant before separation.
- 02
Contact zone
Introduces dissolved-air water so released microbubbles can attach to conditioned flocs.
- 03
Separation zone
Allows bubble-floc complexes to rise while clarified water remains below.
- 04
Skimming and sludge collection
Moves the floated surface layer into the sludge compartment.
- 05
Clarified-water collection
Discharges treated water and returns a selected portion to the dissolved-air system.
Engineering advantages
Why Use a DAF System?
Evaluate the equipment through operating implications, not decorative feature claims.
- 01
Integrated separation train
The QF arrangement combines contact, flotation, skimming, clarified-water collection and recycle functions in one system.
- 02
Clarified-water recycle
A portion of the clarified effluent is returned to the dissolved-air system instead of requiring a separate recycle source.
- 03
Automatic skimming option
Automatic skimmer timing and travel-switch reversal are available, with a manual mode for special operating conditions.
- 04
Anti-blocking release device
A dedicated anti-blocking microbubble release device adjusts its flow with dissolved-air pressure.
- 05
Flexible equipment elevation
The unit can be installed at ground level or overhead when the project layout and foundation are designed accordingly.
- 06
Defined commissioning sequence
Site commissioning covers startup, clean-water trial, pressure, skimmer, water-level and shutdown checks.
Applications
Typical Dissolved Air Flotation Applications
Representative wastewater analysis and treatability testing are required before selecting the system for these industries and duties.
Oil-containing wastewater
Separation of oil and grease from industrial wastewater.
Provide free and emulsified oil data and confirm whether chemical destabilisation is required.
Textile wastewater
Removal of colour-bearing matter and impurities from dyeing wastewater.
Bench testing should confirm chemical response and the required clarification duty.
Leather processing
Removal of impurities from tannery wastewater.
Confirm wastewater chemistry, corrosion conditions and the selected pretreatment sequence.
Pharmaceutical wastewater
Removal of suspended solids and colour.
Review wastewater variability and treatability before defining the equipment duty.
Heavy-metal treatment
Solid-liquid separation after chemical treatment for heavy-metal removal.
The chemical treatment basis, target metals and achievable result require laboratory confirmation.
Post-biological separation
Separation of sludge and suspended material after biological treatment.
Provide biological solids characteristics, flow variation and the required downstream route.
Performance
Key Operating Parameters
The table shows operating references. They are not guaranteed project performance or a substitute for an approved model data sheet.
| Parameter | Value / range | Engineering note |
|---|---|---|
| Dissolved-air working pressure | 0.3-0.5 MPa | Confirm the final pressure setpoint and equipment rating for the selected project. |
| Released bubble diameter | 20-30 μm | This range applies under reduced-pressure release; project performance remains wastewater-specific. |
| Clarified-water recycle | 30% of wastewater flow reference | Use this as a general control reference and adjust the actual amount to influent SS. |
| Flocculation reaction time | About 5 minutes | Determine the optimum time, dose and response through laboratory testing. |
| Wastewater pH during operation | 7.5-8.5 reference | Final chemical conditions depend on actual wastewater and treatment targets. |
| PAC / PAM reference | PAC 20-50 mg/L; PAM about 1/10 of PAC | These are preliminary references only. Coagulant and flocculant selection and dose must be established by testing. |
Working principle
How the DAF System Works
The sequence runs from chemical conditioning and dissolved-air recycle through flotation, skimming and clarified-water discharge.
This equipment photo identifies the recycle pump and connected piping. It is not a process diagram or a model-specific data sheet.
- 01
Coagulation and flocculation
Wastewater is mixed with the selected treatment chemicals under conditions established from wastewater testing.
- 02
Dissolved-air recycle
A portion of clarified water is pressurised with air in the dissolved-air system.
- 03
Pressure release and contact
The recycle stream is released into the contact zone, forming microbubbles that attach to flocs.
- 04
Flotation separation
Bubble-floc complexes rise to the surface while clarified water remains in the lower layer.
- 05
Surface skimming
The skimmer moves floated material into the sludge compartment.
- 06
Clarified-water discharge
Clarified water leaves through the collection system, with a selected portion returned for dissolved-air generation.
Equipment video
See the DAF System in Operation
See an installed dissolved air flotation system operating in an on-site wastewater separation setting. The footage complements the process explanation on this page by showing the equipment at working scale and the practical arrangement around the flotation vessel. It is presented as an operating reference rather than a quantified treatment result. Effluent quality, solids loading, recycle conditions and chemical demand must still be confirmed from the actual wastewater and approved design basis.
What to look for
- The physical scale and arrangement of an installed DAF system.
- An operating flotation vessel in a real wastewater-treatment environment.
- The difference between visual operating evidence and verified water-quality results.
System configuration
Typical DAF System Configuration
The DAF duty combines conditioning, dissolved-air generation, pressure release, flotation, surface skimming, clarified-water collection and recycle.
Final interfaces and included equipment are defined by the agreed project scope.
Before releaseConfiguration decisions to confirm
- 01
Wastewater conditioning
Confirm pH, chemical selection, dose, mixing and flocculation time from representative wastewater testing.
- 02
Recycle and pressure duty
Set the recycle flow and dissolved-air pressure from influent SS, hydraulic duty and verified treatment response.
- 03
Skimming cycle
Define automatic skimming time and sludge-compartment routing for the actual floated-solids loading.
- 04
Water-level setting
Adjust the operating level so the surface layer can enter the sludge outlet without excessive water carryover.
- 05
Installation elevation
Confirm ground-level or overhead placement, access, lifting and the required foundation arrangement.
- 06
Electrical environment
Locate the electrical box for safe access and protect it from moisture, dampness and corrosive gases.
- P1
Influent conditioning
Wastewater is adjusted and mixed with the selected coagulant or flocculant.
- P2
Contact zone
Conditioned wastewater meets the pressure-released dissolved-air recycle stream.
- A1
Dissolved-air system
The working pump, ejector, dissolved-air tank, air supply and release device prepare the recycle stream.
- P3
Flotation zone
Attached solids rise and separate from the clarified lower water layer.
- R1
Skimmed sludge
The skimmer transfers floated material to the sludge compartment.
- R2
Clarified water
Collected water is discharged, with a selected portion returned to the dissolved-air system.
Main equipment
- QF-Series Horizontal Flow Dissolved Air Flotation Unit
Supporting / optional equipment
- Working / Recycle Pump
- Dissolved-Air Tank
- Ejector and Air Release Device
- Air Compressor
- Skimmer
- Agitator
- Chemical Dosing Pumps
- Electrical Control Cabinet
Technical data
Confirmed Operating & Installation Data
These values are operating references, not a QF model comparison. Rated capacity, power, dimensions, weight, control-system specification and construction grade require an approved project-specific data sheet.
Scroll horizontally to review all technical fields on smaller screens.
| Operating item | Reference value | Project confirmation |
|---|---|---|
| Dissolved-air pressure | 0.3-0.5 MPa | Confirm the selected operating setpoint and equipment rating. |
| Released bubble diameter | 20-30 μm | Confirm performance with the selected release device and wastewater. |
| Clarified-water recycle | 30% of wastewater flow reference | Adjust from influent SS and verified flotation response. |
| Flocculation time | About 5 minutes | Determine optimum time and mixing conditions through testing. |
| Concrete foundation allowance | (L + 500) × (B + 500) | Use the approved equipment dimensions and include separate equipment foundations where required. |
| Operating water level | 1-2 cm below the scum outlet | Commission the level to avoid poor skimming or excess water in the sludge compartment. |
| Dissolved-air stabilisation | Approximately 10 minutes during clean-water trial | Verify stable dissolved-air water before introducing wastewater. |
Equipment selection
How to Select the Right DAF System
Selection begins with wastewater flow, influent characteristics, treatment target and verified coagulation and flocculation response.
- 01
Wastewater source
Identify the production process and the upstream and downstream treatment steps.
- 02
Design flow
Provide average, peak and batch flow conditions together with the intended operating schedule.
- 03
Influent characteristics
Share representative SS, oil and grease, colour, pH and other relevant wastewater analysis.
- 04
Treatment target
Define the required clarification duty and the next process or discharge route.
- 05
Chemical response
Provide jar-test or site-test results for coagulant, flocculant, pH and flocculation time when available.
- 06
Floated-solids handling
Confirm the sludge storage, transfer and downstream dewatering arrangement.
- 07
Site constraints
Confirm footprint, elevation, lifting access, foundation, climate, corrosion conditions, voltage and control interfaces.
Manufacturing & installation evidence
Real DAF System Equipment Views
These approved images show KUOSI DAF equipment and installation contexts. They are not presented as quantified customer case studies.
01
Installation & operation views
Registered DAF media showing outdoor, sheltered and side-view installation contexts.
Engineering support
From Equipment Selection to System Integration
Support is presented as a practical engineering workflow, without unverified company statistics or outcome claims.
- 01
Wastewater review
Review the available flow, water-quality and treatment-target data before equipment selection.
- 02
Treatability planning
Define the laboratory or site testing needed to confirm pH, chemical selection and flocculation response.
- 03
Equipment sizing
Evaluate hydraulic duty, recycle requirements and operating schedule from confirmed project inputs.
- 04
System integration
Define dosing, dissolved-air, skimming, sludge, clarified-water and control interfaces.
- 05
Commissioning guidance
Provide the applicable clean-water trial, pressure, water-level, skimmer and startup checks for the agreed scope.
Technical FAQ
DAF System Frequently Asked Questions
The answers separate general selection logic from the values that require a project-specific technical review.
01What is a dissolved air flotation system?+
The KUOSI QF system is a horizontal-flow solid-liquid separation unit. It releases dissolved air into conditioned wastewater so microbubbles attach to flocs, lift them to the surface for skimming and leave clarified water below.
02How does this DAF system work?+
Conditioned wastewater enters the contact zone and meets pressure-released dissolved-air recycle water. Bubble-floc complexes rise in the separation zone, the skimmer transfers floated material to the sludge compartment, and clarified water is discharged with a portion returned to the dissolved-air system.
03What wastewater applications can be evaluated?+
Applications include paper white-water recovery, oil-containing wastewater, leather, textile dyeing, pharmaceutical wastewater, heavy-metal treatment and post-biological solid-liquid separation. Final suitability still depends on representative wastewater data and testing.
04What dissolved-air pressure is used?+
The working-pressure reference is 0.3-0.5 MPa. The final operating setpoint and equipment rating must be confirmed for the selected project and release device.
05How much clarified water is recycled?+
Use 30% of wastewater flow as a general dissolved-air-water reference, then determine the actual amount from influent suspended solids. It is not a universal fixed ratio.
06Are coagulants or flocculants required?+
PAC and PAM references, pH adjustment and an approximately five-minute flocculation reaction provide a preliminary basis. Chemical type, dose, pH and reaction time must be selected from actual wastewater testing rather than applied as guaranteed universal settings.
07What information is needed to select a DAF system?+
Provide average and peak flow, wastewater source, SS, oil and grease, colour, pH, treatment target, chemical-test results, operating schedule, sludge route, site utilities and installation constraints. A rated QF model-capacity table must be confirmed for the project.
08What installation checks are required?+
Installation checks include a level foundation, debris removal, pump and transmission checks, correct motor rotation, skimmer and agitator checks, clean-water trial operation, dissolved-air pressure verification, water-level adjustment and protection of the electrical box from moisture and corrosive gases.
Engineering inquiry
Need Help Selecting the Right DAF System?
Share your wastewater flow, influent analysis, treatment target, chemical-test results and site conditions. KUOSI can use the available data to evaluate the appropriate DAF duty and system configuration.