Dissolved Air Flotation systems for removing suspended solids, oils, and grease from industrial wastewater with exceptional efficiency.
Free interactive DAF sizing calculator. Calculate dissolved air flotation surface area, recycle flow, saturator volume, and power.
FOG removal food industry DAF systems for fat oil grease recovery food processing.
DAF systems for oil and gas produced water and refinery wastewater treatment.
Design DAF systems for correct hydraulic loading. Surface area, rise rate and detention time calculations for your flow.
Industrial DAF system with integrated piping and controls
Complete DAF flotation unit ready for installation
Our DAF systems use micro-bubble flotation to separate suspended solids, oils, and grease from wastewater streams, delivering superior treatment performance with minimal operational costs.
Produces fine air bubbles (20-50 microns) that attach to suspended particles, creating a buoyant sludge blanket that rises to the surface for removal.
Micro-Bubble TechnologyDesigned to handle high flow rates with compact footprint, achieving hydraulic loading rates up to 15 m/h depending on application.
Hydraulic Loading GuideFully automated systems with PLC control, level sensors, and variable speed drives for optimal performance and minimal operator intervention.
Automated Operation GuidePressurised recycle flow dissolves air into treated water, which is then released at atmospheric pressure to create the flotation bubble blanket.
Recycle Flow GuideOur DAF systems are trusted across diverse industries for effective wastewater treatment.
Removal of fats, oils, grease (FOG), and suspended solids from food production wastewater.
Effective treatment of high-protein wastewater containing blood, fat, and protein solids.
Removal of oil droplets and suspended solids from produced water and refinery wastewater.
Treatment of process water containing oils, coolants, and suspended solids from industrial operations.
Removal of algae, suspended solids, and organic matter before reverse osmosis membranes.
Phosphorus removal and primary clarification for municipal wastewater treatment plants.
Small footprint compared to conventional clarifiers, saving valuable floor space in existing facilities.
Energy-efficient design with optimised air dissolution and recycle systems to minimise operating overheads.
Available in various sizes and configurations to match your flow requirements and space constraints.
Designed with accessibility in mind for straightforward inspection, cleaning, and component replacement.
Built with high-quality materials including stainless steel components for long service life in demanding environments.
Reliable operation with consistent effluent quality even under varying influent conditions.
Detailed engineering guides, contaminant profiles, and example project proposals tailored to your industry.
FOG and solids removal for dairy, bakery, ready meals, and vegetable processing wastewater. Example proposals from comparable installations are available on request.
View SolutionsBlood, protein, and fat separation for abattoirs, cutting plants, and rendering facilities. Example proposals from comparable installations are available on request.
View SolutionsProduced water and refinery wastewater treatment with ATEX options. Example proposals from comparable installations are available on request.
View SolutionsCoolant, tramp oil, and metal fines removal for metalworking and industrial operations. Example proposals from comparable installations are available on request.
View SolutionsCEPT and phosphorus removal for wastewater treatment plants. Example proposals from comparable installations are available on request.
View SolutionsDiscuss your specific requirements with our technical team and receive a tailored proposal for your project.
Contact UsGas Solubility, Micro-Bubble Generation and the Air-to-Solids Ratio
DAF exploits the fact that gas solubility in water is roughly proportional to pressure. Water is supersaturated with air in a pressurised saturator, then released through a nozzle at atmospheric pressure. The dissolved air comes out of solution as a cloud of 20–50 µm micro-bubbles that nucleate on, and lift, the coagulated solids.
Mass of air dissolved per unit volume of water: Cg = H·P. For air in 20 °C water, H ≈ 22.8 mg/L per atm. At a saturator pressure of Psat = 5 bar abs, solubility is ~114 mg/L. When the recycle stream depressurises to 1 atm, the supersaturation ΔC = H(Psat − 1) ≈ 91 mg/L of released air — this is the bubble inventory available to lift solids. The saturator efficiency factor f (typically 0.6–0.9) accounts for incomplete dissolution.
The governing process parameter is the mass ratio of air released to influent solids: A/S = f·Csat·R / (Q·Si), where R is the recycle flow, Q the forward flow and Si the influent TSS (mg/L). Empirical optima sit in the range 0.01–0.05 kg air / kg solids. Below 0.01 the bubble:floc ratio is starvation-limited; above 0.05 excess gas drag breaks up flocs and the float layer becomes unstable.
An isolated 40 µm air bubble rises under Stokes’ law at v = g(ρw − ρair)d2 / 18μ ≈ 0.9 mm/s. Once bubble-floc aggregates form (effective ρagg ≈ 200–600 kg/m³, dagg ≈ 100–300 µm), rise velocity climbs to 2–10 mm/s (7–36 m/h). The DAF tank surface loading rate must be < vrise, which fixes the floor area for a given Q.
For a target A/S, the recycle ratio R/Q is found from R/Q = (A/S)·Si / (f·Csat). Typical values are 6–30% for industrial DAF and 30–100% for low-TSS desalination pre-treatment. The flotation tank itself is sized for an overflow rate of 5–15 m/h (high-rate lamella DAF up to 30 m/h), giving HRTs of 20–40 minutes. Saturator volume sets the air-water contact time and is typically 1.5–3.0 minutes of recycle flow.
Worked example. For Q = 50 m³/h with Si = 800 mg/L TSS (food processing), target A/S = 0.025, Psat = 5 bar (f·Csat ≈ 73 mg/L): R/Q = 0.025·800/73 = 0.27 → R = 14 m³/h. Tank floor area at SLR = 10 m/h: A = (Q+R)/SLR = 6.4 m². Saturator: V = 2 min × R/60 = 0.47 m³.
Quick-reference parameters for preliminary DAF specification. Use our interactive calculator for application-specific sizing.
DAF systems handle flows from 5 to 500 m³/h. Modular design allows capacity upgrades without major civil works, and multiple units can operate in parallel for larger flows.
Design & sizing guideSurface loading rates of 5–15 m/h ensure efficient solids separation. Optimised lamella plate spacing maintains performance across the full flow range.
Hydraulic loading explainedTotal suspended solids removal of 85–99% depending on influent characteristics and chemical conditioning. Consistent effluent quality meets discharge or reuse standards.
Coagulation & floc controlPrecisely controlled A/S ratio of 0.01–0.05 kg/kg ensures optimal bubble-particle attachment. Automated saturation pressure maintains the ratio across variable influent loads.
Recycle & A/S ratioRecycle stream pressurised to 400–600 kPa for micro-bubble generation. Variable-speed pumps adjust pressure to match influent solids loading and flow variations.
Saturator & air systemAir bubbles of 20–50 micron attach to oil droplets and suspended particles. Lamella plates enhance bubble-particle contact time for maximum separation efficiency.
Micro-bubble technologyContact Our Engineers to discuss your DAF requirements, or explore our calculators and case studies for design inspiration.
DAF flotation units in ISO containers for rapid deployment and relocatable operations.
Option B: DAFRapid mixing tanks for coagulant dispersion ahead of DAF flotation.
View Flash Mix TanksFrom bubble physics to skid layout: the core calculations behind every DAF unit.
Surface area sized for 4–12 m³/m²·h depending on solids type. Light flocs (algae, oil): 8–12 m/h. Dense flocs (metal precipitates): 4–6 m/h.
Critical sizing parameter: 0.005–0.06 kg air/kg solids. Oil-bearing wastewater: 0.01–0.04. Activated sludge thickening: 0.02–0.05. Below 0.005, bubble adhesion is poor.
4–6 bar standard; 6–8 bar for high-A/S duties. Henry’s Law: air solubility 110–180 mg/L at 5 bar, 20°C. Saturator efficiency 60–85% (packed) or 90–95% (cyclonic).
Pressurised recycle: 15–50% of feed flow. Higher recycle → more bubbles but more dilution. Optimum balances A/S with hydraulic loading.
20–80 μm optimal. Smaller bubbles have higher surface area per volume but slower rise. Achieved by specific saturator design and release-valve geometry.
30–60 minutes flotation cell + 10–20 minute contact zone. Plug-flow contact zone (G > 100 s⁻¹) for bubble-particle attachment; quiescent flotation zone.
| Parameter | Municipal / general | Industrial oily | Algal / WT |
|---|---|---|---|
| Hydraulic loading (m³/m²·h) | 5–8 | 4–6 | 8–12 |
| A/S ratio (kg air/kg solids) | 0.005–0.02 | 0.01–0.04 | 0.005–0.015 |
| Saturator pressure (bar) | 4–5 | 5–6 | 4–5 |
| Recycle ratio | 20–35% | 30–50% | 20–30% |
| Cell residence time (min) | 30–40 | 40–60 | 30–45 |
| Inlet solids removal | 80–95% | 90–98% | 85–95% |
Our DAF sizing calculator estimates surface area, recycle flow, and saturator volume from your flow rate and TSS. Or request a feasibility study and our engineers will validate technology selection, run jar testing, and size equipment for your specific wastewater.
Process and instrumentation diagrams for dissolved air flotation including saturation, recycle, and sludge lines.
View ServicePlan and elevation views for DAF influent, effluent, and air saturation piping.
View ServiceEquipment general arrangements showing DAF cell dimensions, nozzle positions, and access requirements.
View ServiceOptimised 3D pipe routing with clash detection for DAF saturation and recycle systems.
View ServiceCompare dissolved air flotation, lamella clarifiers, and conventional settling — performance, cost, and footprint.
Compare technologies →Diagnose and resolve common DAF faults: float carry-over, poor TSS removal, foaming, and saturator issues.
View troubleshooting guide →Answers to the most common questions on DAF sizing, chemicals, sludge, and operational parameters.
Read FAQs →How a 65 m³/h DAF installation reduced a dairy processor's BOD discharge by 96% and recovered fat for resale.
Read case study →Stokes’-law sizing, API Publication 421 design methodology, rectangular API / CPI / TPI configurations and refinery-train integration.
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