Specialised dissolved air flotation systems engineered for the food industry, delivering exceptional FOG and suspended solids removal to meet strict discharge consents and reduce sewer surcharge costs.
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.
Food industry DAF system with integrated chemical dosing
The food processing industry generates wastewater with some of the most challenging characteristics for treatment operators. Effluent streams are typically high in organic loading, with biochemical oxygen demand (BOD) ranging from 500 to 4,000 mg/l and chemical oxygen demand (COD) from 1,000 to 8,000 mg/l depending on the specific sub-sector. The presence of fats, oils, and grease (FOG) creates additional complications, with concentrations commonly reaching 200 to 2,000 mg/l. These parameters, combined with highly variable pH, elevated temperatures from cooking and cleaning operations, and significant seasonal production peaks, demand robust, flexible treatment solutions.
Dissolved Air Flotation has emerged as the pre-eminent primary treatment technology for food industry wastewater due to its exceptional ability to separate buoyant contaminants. Unlike gravity-based sedimentation systems that struggle with grease and low-density organic matter, DAF exploits the natural buoyancy of FOG-laden particles by attaching micro-bubbles that lift contaminants to the surface for rapid removal. This makes DAF particularly effective across diverse food sub-sectors including dairy processing, where butterfat and milk solids dominate; meat and poultry slaughter and further processing, where blood, fat, and protein solids are prevalent; bakery operations with high starch and fat loads; ready meals manufacturing with complex multi-ingredient waste streams; and vegetable processing, where soil, starch, and vegetable oils must be removed.
Reynolds & Bauhm is involved in the design and manufacture of DAF systems specifically optimised for the food processing environment. Our food-grade material options, automated chemical dosing systems, and integrated sludge handling solutions ensure consistent compliance with UK water company trade effluent consents and Environment Agency discharge permits. Whether you operate a single-site dairy or a multi-product food manufacturing complex, our engineers will size and configure a DAF system matched to your hydraulic and contaminant loading profile.
| Parameter | Typical Range | DAF Removal Efficiency |
|---|---|---|
| FOG | 200 – 2,000 mg/l | 90 – 99% |
| TSS | 300 – 3,000 mg/l | 85 – 95% |
| BOD | 500 – 4,000 mg/l | 40 – 60% |
| COD | 1,000 – 8,000 mg/l | 35 – 50% |
| pH | 4.0 – 10.5 | Neutralisation required |
| Temperature | 15 – 55 °C | Design consideration |
Note: Actual removal efficiencies depend on influent characteristics, chemical programme, hydraulic loading rate, and bubble size distribution. Jar testing and pilot trials are recommended for accurate performance prediction.
Influent wastewater passes through rotary drum or static screens to remove large solids, packaging debris, and fibrous material that could damage downstream DAF components or impair bubble-particle attachment.
Coagulants (ferric chloride or PAC) and anionic polyelectrolyte flocculants are precisely dosed to destabilise colloidal particles and promote floc formation. pH correction to 6.5–7.5 optimises chemical performance.
Pressurised recycle water saturated with dissolved air is released into the flotation cell, generating micro-bubbles (20–50 microns) that attach to FOG and solids. The buoyant sludge blanket rises to the surface.
A continuous chain-and-flight or bridge scraper system removes the floated sludge blanket into a collection hopper. High-organic food sludge is typically transferred to a screw press or centrifuge for dewatering.
Where tighter discharge limits apply, DAF effluent can be polished through sand filtration, multimedia filters, or advanced biological treatment to achieve residual FOG < 10 mg/l and TSS < 20 mg/l.
Food wastewater with elevated FOG requires conservative hydraulic loading rates (typically 4–8 m/h) to ensure adequate bubble residence time and prevent short-circuiting of buoyant material through the cell.
Ferric chloride, polyaluminium chloride (PAC), and anionic polyelectrolytes are selected through jar testing. Food-specific chemistries avoid tainting risks and optimise charge neutralisation for protein-fat flocs.
Food DAF sludge contains 3–6% solids with high volatile organic fraction. Integrated screw presses or chamber filter presses reduce disposal requirements, while fat recovery systems can render valuable by-products.
Anaerobic conditions in food sludge generate hydrogen sulphide and mercaptans. Our DAF systems can be supplied with enclosed flotation cells, venting to biological scrubbers or carbon filters to control nuisance odours.
Hot wastewater from cooking and CIP systems reduces air solubility, impacting bubble generation. Our saturator designs compensate with variable pressure control and temperature-adjusted recycle ratios.
Stainless steel 304 or 316 construction resists attack from chlorides, organic acids, and cleaning chemicals common in food plants. Epoxy-coated carbon steel options are available for budget-conscious projects.
Realistic project envelopes based on typical food industry applications. Contact us for a site-specific quotation.
Flow Rate: 150 m³/day (6.25 m³/h average)
Influent FOG: 800 mg/l
Influent TSS: 1,200 mg/l
Influent BOD: 2,500 mg/l
DAF Model: DF DAF-C 10 (Compact Series)
Key Equipment: SS 316 flotation cell, saturator with pall rings, chain scraper, sludge hopper, PLC control panel
Chemical Consumption: Ferric chloride ~45 kg/day; Anionic polyelectrolyte ~2.5 kg/day
Flow Rate: 400 m³/day (16.7 m³/h average, 25 m³/h peak)
Influent FOG: 1,500 mg/l
Influent TSS: 2,800 mg/l
Influent BOD: 3,800 mg/l
DAF Model: DF DAF-S 25 (Standard Series)
Key Equipment: SS 304 flotation cell, duplex saturator pumps, automated chemical station, sludge pump to screw press, SCADA-compatible PLC
Chemical Consumption: PAC ~120 kg/day; Anionic polyelectrolyte ~6 kg/day
Flow Rate: 80 m³/day (3.3 m³/h average)
Influent FOG: 250 mg/l
Influent TSS: 800 mg/l
Influent BOD: 900 mg/l
DAF Model: DF DAF-C 5 (Compact Series)
Key Equipment: Coated CS flotation cell, saturator with pall rings, bridge scraper, sludge collection tank, simple relay control
Chemical Consumption: Ferric chloride ~15 kg/day; Anionic polyelectrolyte ~1.0 kg/day
All figures are indicative budgets for budgetary planning purposes. Final Capital expenditure and Operating expenditure depend on site-specific factors including civil works, existing infrastructure, effluent consent limits, and sludge disposal routes. We strongly recommend a jar test and, where possible, on-site pilot testing to validate chemical selection and confirm hydraulic sizing before firm quotation.
Consistently achieve effluent FOG concentrations below 15 mg/l, satisfying UK water company trade effluent consents and avoiding enforcement action.
Removing FOG and solids before discharge reduces Mogden formula surcharge costs, often delivering project benefits within 18 to 36 months.
Concentrated food sludge and recovered fats can be sent for rendering into animal feed or bio-diesel, turning waste into output.
DAF systems occupy 30–50% less space than conventional clarifiers, fitting into congested food plant environments without building extensions.
PLC-controlled chemical dosing, level sensing, and sludge removal minimise operator attendance, freeing production staff for core duties.
DAF units reach stable performance within minutes of start-up, making them ideal for batch processing and variable production schedules.
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View PageFood & beverage effluent characteristics demand specific DAF tuning — FOG, high BOD, variable pH, sanitary materials.
Free + emulsified FOG: 200–3,000 mg/L. Free FOG floats readily; emulsified FOG requires acid pH shock or coagulation to break. DAF removes 95–99% with proper conditioning.
Inlet pH adjusted to 5.5–6.5 with H₂SO₄ or HCl prior to coagulant addition. Below 5.5: corrosion risk; above 6.5: coagulant inefficiency on FOG.
Ferric chloride 100–400 mg/L typical; alum less common (lower FOG efficiency). Polymer 1–5 mg/L cationic for floc strength. Jar testing validates.
Hot CIP wastewater (40–70°C) reduces FOG flotation efficiency by lowering specific gravity differential. Cool to <30°C with heat exchanger if technically viable.
SS304L minimum; SS316L for chloride-rich streams (cleaning agents, sea-water washing). Polished welds; sanitary clamps; CIP-able geometry.
Recovered FOG (5–15% solids) sold to renderers at –80/t. A 500 m³/d dairy plant recovers 2–4 t/week FOG — offsetting 30–50% of DAF Operating expenditure.
Speak to our engineers about a DAF system engineered for your specific food processing application.
Our expertise spans multiple industries with sector-specific water treatment solutions.