Food and beverage sites rarely have a wastewater problem in general - they have a fats, oils and grease problem, plus a COD peak that arrives with cleaning shifts. The municipality prices exactly those two parameters, month after month.
Dissolved air flotation removes both, provided it is sized for the production reality rather than for a daily average.
Typical performance in food industry duty
- FOG removal
- > 95 %
- TSS removal
- > 95 %
- COD reduction
- 60-85 %
- Phosphorus removal with precipitation
- > 90 %
Engineering Hub: get this sized for your plant
Describe your goal, effluent limit or sludge volume and receive a technology shortlist plus a sizing proposal – by email, no phone call required.
How dissolved air flotation works
A part stream of clarified water is saturated with air at 4-6 bar. When it is released into the flotation cell, micro bubbles of roughly 20-40 micrometres form. They attach to the flocs created upstream by coagulation and flocculation and carry them to the surface, where a scraper removes the float layer.
Process sequence
- 1pH correction to the optimum window for the coagulant
- 2Coagulation: metal salt destabilises colloids
- 3Flocculation: polymer builds transportable flocs
- 4Saturation and release: micro bubbles lift the flocs
- 5Skimming: float sludge is removed, clarified water leaves at the bottom
Chemistry decides, not the tank
Most underperforming DAF units are not undersized - they are chemically mistuned. pH window, coagulant type, dosing point and flocculation time matter more than a few square metres of surface.
Sizing for production, not for averages
Data needed for a reliable DAF proposal
- Flow profile over a full production day, including cleaning shifts
- COD, BOD, TSS and FOG as ranges with peak values
- pH and temperature range
- Discharge limits and the surcharge formula of your municipality
- Existing buffer volume - or the space to create it
- Sludge handling route for the float sludge
Buffering is usually cheaper than oversizing
A balancing tank that flattens the cleaning-shift peak lets you install a smaller DAF and run it at a constant, optimal load. Both capital and chemical costs fall.
What the surcharge saving really looks like
2-4 years
typical payback in food industry cases
1
additional stage needed before the sewer
> 90 %
of the surcharge parameters addressed by one unit
The calculation is straightforward once the load data exists: current surcharge per month, minus expected residual load after treatment, minus operating cost for chemicals, electricity and float sludge disposal. What often tips the case is the float sludge - it has to be dewatered or hauled away, so it belongs in the calculation from the start.
Float sludge: plan the downstream step
Float sludge from a DAF is typically 2-5 % dry solids. Hauling it wet is expensive. A screw press downstream reduces the volume substantially and turns a liquid waste stream into a stackable cake.
Equipment we supply for this
Prove it on your own wastewater
Food wastewater varies with recipe, season and cleaning regime. A rental or trial unit on site gives you the removal rates for your effluent - and the numbers to defend the investment internally.
Does a DAF unit replace a grease trap?+
It goes far beyond it. A grease trap removes free floating grease; a DAF removes emulsified fats, fine solids and, with precipitation, phosphorus.
How much space does a DAF unit need?+
Considerably less than a sedimentation basin of comparable capacity, because separation is driven by bubbles rather than by settling velocity. Layout depends on flow and the required surface loading.
Can we rent a unit first?+
Yes. Trial and rental units are the normal way to confirm removal rates before a capital decision, and rental fees are commonly credited against a later purchase.
Engineering Hub: get this sized for your plant
Describe your goal, effluent limit or sludge volume and receive a technology shortlist plus a sizing proposal – by email, no phone call required.