DAF Sizing Calculator
Size a dissolved air flotation (DAF) system for food & beverage industry wastewater. Get tank dimensions, sludge mass balance, material selection, and a preliminary bill of quantities.
DAF System Parameters
Results update live as you type. All values are preliminary engineering estimates.
1 KLD = 1 m³/day
Cross-section (to scale)
Circular DAF · total depth 2.5 m
Methodology & assumptions: Air/recirculation sized on the Metcalf & Eddy A/S relationship using temperature-dependent air solubility (~15.4 mL/L). Solids loading includes FOG (which reports to the float). Pump power = ΔP·Q; compressor power via isentropic compression (k = 1.4, P₁ = 101.325 kPa); efficiencies: recirc pump 70%, compressor 75%, feed pump 72%. Standard motor sizes rounded up (kW). Fluid density 1000 kg/m³; float ~4% dry solids.
Disclaimer: This BOQ is a preliminary equipment list for budgeting and planning only. Final design must be confirmed by detailed engineering, jar tests, and site conditions.
How DAF Works
Dissolved air flotation (DAF) is a physical-chemical separation process widely used as a primary treatment step in food and beverage wastewater treatment. It is particularly effective at removing fats, oils, grease (FOG), and suspended solids before downstream biological treatment.
The process works by dissolving air into a portion of recycled treated water under pressure (4–6 bar) in a pressure dissolving vessel. When this pressurised water is released back into the DAF tank at atmospheric pressure, millions of fine microbubbles (20–100 µm) form. These bubbles attach to suspended solids and FOG particles, making them buoyant. The particles float to the surface and are continuously skimmed off as a float layer (sludge).
Chemical conditioning — coagulation with alum, PAC, or ferric salts, followed by flocculation with a polyelectrolyte — significantly improves particle aggregation and DAF performance, achieving 88–93% TSS and 85–92% FOG removal in food industry applications.
Design Equations
# DAF Sizing — Key Equations
Peak flow (m³/hr) = Average flow × 1.25 (peaking factor)
Surface Area (m²) = Peak flow ÷ HLR (m³/m²/hr)
HLR_food = 4.5–6.0 m³/m²/hr [industry-specific]
# Recycle Ratio (ASR method)
R/Q = ASR × SS_in ÷ (1.3 × Sa × (f×P − 1))
ASR = 0.020 mL/mg | Sa = f(temperature) | P ≈ 5.4 atm abs
# Sludge Mass Balance
Dry sludge (kg/day) = TSS_removed + FOG_removed + Chemical_sludge
Wet volume (m³/day) = Dry sludge ÷ (solids% × ρ_sludge)
Solids% ≈ 4% | ρ_sludge ≈ 1020 kg/m³
Frequently Asked Questions
What wastewater types is DAF best suited for in food & beverage?
DAF excels at treating high-FOG wastewaters — dairy (milk, cheese, butter), meat and poultry processing, seafood, edible oil refining, and brewery effluents. It is used as a primary treatment step to reduce TSS and FOG loads before biological treatment (MBBR, SBR, activated sludge).
When should I specify SS 316L instead of SS 304?
Use SS 316L for seafood processing (chlorides from brine), coastal installations, or any application with high chloride levels or aggressive CIP chemicals. SS 304 is suitable for inland dairy, beverage, and general food & beverage applications.
What is typical DAF sludge solids content?
DAF float from food industry wastewater is typically 3–5% solids (95–97% moisture). Sludge thickening or dewatering is often required before disposal to reduce transport costs.
Is food industry DAF sludge hazardous?
Generally no — food industry DAF float is non-hazardous, rich in proteins and fats. It is suitable for composting, anaerobic digestion (biogas recovery), or approved land application. Always verify with your SPCB consent conditions.
What recycle ratio should I design for?
Typically 15–50% of feed flow. Higher solids loads (e.g. meat processing, edible oil) require higher recycle ratios to deliver sufficient air. The tool calculates the recycle ratio based on the air-to-solids ratio method.
What coagulant is recommended for food industry DAF?
PAC (Polyaluminium Chloride) is widely preferred for food industry DAF due to its lower sludge production, wider effective pH range, and lower aluminium residual vs alum. Ferric chloride is preferred where phosphorus removal is also required.
How does temperature affect DAF performance?
Higher temperatures reduce air solubility. At 30°C, Sa = 14.8 mL/L vs 18.0 mL/L at 20°C, requiring a higher recycle ratio for the same ASR. This tool applies temperature-corrected air solubility values automatically.
Can DAF treat the effluent to discharge standards alone?
Rarely on its own — DAF is a primary treatment step. It removes TSS and FOG effectively but does not significantly reduce BOD/COD from soluble organics. DAF is typically followed by biological treatment (MBBR, SBR, or activated sludge) to achieve CPCB discharge standards.
Designing a DAF System?
Spans Envirotech designs and supplies DAF systems for food & beverage, dairy, meat processing, and edible oil industries across India and internationally.