DAF case studies and published performance data
Equipment suppliers publish case studies about their own projects, which is exactly the evidence a buyer cannot verify. This library does the opposite: it collects dissolved air flotation performance that has been measured, written up and published by someone else, with the source cited so you can check it.
Every figure on this page comes from a peer-reviewed paper, a research-council report or a published full-scale study, and every entry names its source. None of it is our own project work presented as a reference. Where a study reports poor performance, it is included on the same terms as one reporting excellent performance — the badly optimised plants are often the more useful reading.
Use these as evidence of what dissolved air flotation achieves on a given stream, and as a sanity check on any number a supplier quotes you. Do not use them as design values for your own plant: influent varies, and the only defensible design basis is a jar test on your effluent.
The evidence table
| Stream and setting | Scale | Reported influent | Reported removal | Chemistry | Source |
|---|---|---|---|---|---|
| Algae-laden reservoir water Lake Chivero, Harare, Zimbabwe | 60 L pilot, 7 m/h, 300–400 kPa | Turbidity 3.14–4.04 NTU Chlorophyll-a 0.36–2.12 µg/L pH 7.2–8.4 | Turbidity −64% Chlorophyll-a −95% (Conventional settling on the same water: −53% and −52%) | Alum 70 mg/L, sulphuric acid to pH 6.5–6.9 | Water Practice & Technology 18(1) 102, 2023 |
| Slaughterhouse effluent Improved primary treatment | Full scale | Not fully stated in abstract | FOG −95% COD −80% across primary treatment | Coagulation and flocculation ahead of DAF | Water Science & Technology 85(5) 1688, 2022 |
| Poultry slaughterhouse Operating strategy evaluation | Full scale | Slaughterhouse effluent, high FOG and protein | SS −43 ± 15% FOG −49 ± 8% | 24 mg/L as Al³⁺ plus 1.5 mg/L anionic polymer | Resources, Conservation and Recycling, 2008 |
| Abattoir wastewater Early full-scale evaluation | Laboratory and full scale | Abattoir effluent | Reported COD, SS and FOG reductions commonly 50–80% depending on air pressure and flocculant | Varied by trial | Water Research 20(1), 1986 |
| Municipal effluent, oil and grease Pressure and recirculation optimisation | Pilot, 1–5 bar, recirculation 1–20 min | TS 800 mg/L TSS 590 mg/L Oil & grease 450 mg/L BOD₅ 360 mg/L COD 710 mg/L | O&G −84.4% BOD₅ −88.9% COD −88.7% TSS −85% | Air only; Raschig-ring absorption column | Water (MDPI) 17(24) 3474, 2025 |
| Palm oil mill effluent Liquid–solid separation | Reported study | Digested POME | TSS −90% BOD −80% | 560 kPa saturator pressure | Environmental Technology Letters, 1988 |
| Palm oil mill effluent Flotation plus membrane bioreactor | Combined process | POME | COD −97% TSS −93.9% Turbidity −99.8% Fats and oils −99.9% | Air flotation pretreatment ahead of anaerobic membrane stage | Published combined-process study, 2016 |
| Southern African plants Clarification and sludge thickening | Survey of 26 operating plants | Range of municipal and industrial duties | Design and operating parameters compiled across the sample | Various | WRC Report TT 60/93, Water Research Commission, 1993; Water Science & Technology 31(3–4) 203, 1995 |
| Drinking water plant, South Africa Recycling of DAF residue | Full scale | Surface water | Feasibility of recycling wastewater including DAF residue within the works | Conventional potable coagulation | Water SA, July 2019 |
| Biodiesel wastewater Acidification and coagulation | Reported study | Biodiesel process water, very high FOG | Substantially enhanced flotation efficiency after acidification ahead of coagulation | Acid split then coagulant | Desalination, 2011 |
| Groundwater TOC, colour and arsenic | Reported study | Groundwater with organic colour and arsenic | Removal of TOC, colour and arsenic assessed for flotation duty | Coagulation ahead of flotation | Applied Sciences 15(20) 11255, 2025 |
What the spread actually tells you
Put the poultry slaughterhouse study next to the improved-primary slaughterhouse study and the point of this library becomes clear. Both are full-scale, both are meat processing, both use flotation. One reports 49% FOG removal; the other reports 95%. The difference is not the technology.
- Dose is the first variable. The poultry study ran at 24 mg/L as Al³⁺ with 1.5 mg/L of anionic polymer. That is a modest coagulant dose for a stream that heavily loaded, and the removals reflect it.
- Coagulation pH is the second. Aluminium coagulants outside 5.5–9.0 form poor floc regardless of dose, and slaughterhouse streams swing with cleaning cycles.
- Flocculation time and shear is the third. Floc that has not had 10–20 minutes of gentle mixing will shear apart at the recycle nozzle whatever the chemistry.
- Air-to-solids ratio is the fourth, and it is the one most often left at whatever the commissioning engineer set on the day.
A supplier quoting you 95% FOG removal is not lying — that figure is published and achievable. Whether your plant reaches it depends on four variables that are set at design and defended in operation. See the design parameters reference and the troubleshooting guide.
Case studies in detail
Further detailed entries are being added as the underlying papers are read in full rather than summarised from abstracts. The evidence table above is updated as new published data appears.
The Southern African design guide
One reference deserves separate mention. In 1993 the South African Water Research Commission published A South African Design Guide for Dissolved Air Flotation (Report TT 60/93), built by combining a literature survey with a detailed survey of 26 dissolved air flotation plants then operating in Southern Africa, covering both water clarification and activated sludge thickening. It remains, three decades on, the most substantial body of African DAF operating data in the public domain, and it is available free of charge from the Water Research Commission.
Anyone specifying flotation for an African plant should read it. The companion papers in Water Science & Technology volume 31, issues 3–4 (1995) summarise the same work in journal form.
Frequently asked questions
Why do you publish other people’s case studies rather than your own?
Because a supplier’s own case study is the one piece of evidence a buyer cannot check. Published work has been through review, states its method, and can be read in full by anyone who wants to argue with it. If we later publish our own project data, it will be labelled clearly as ours and held to the same standard of stating the influent, the chemistry and the method.
Can I use these removal percentages to size my plant?
No, and no responsible supplier would let you. These figures tell you what flotation is capable of on a broadly similar stream. They do not tell you what your stream will do, because influent characteristics, coagulant response, temperature and pH all differ. Use them to sanity-check a supplier’s claim; use a jar test on your own effluent to size the plant.
Why is a study reporting only 43% solids removal included?
Because it is real, it is full-scale, and it is more instructive than the successes. It shows what an under-dosed flotation plant achieves, which is the outcome a buyer is actually at risk of. Selecting only the flattering results would make this page marketing rather than evidence.
Are there published DAF case studies from African industrial plants?
Fewer than there should be. The substantial African material is the Water Research Commission survey of 26 Southern African plants, the Harare algae study, and a small number of South African drinking-water papers. Most African industrial flotation installations are never written up, which is precisely the gap this library exists to narrow. If you operate one and are willing to have the data published, we would rather publish it than not.
How often is this page updated?
As new published data is found, and reviewed at least quarterly. Each entry carries its publication year so you can see how current the evidence is. Studies from the 1980s are included where they remain the best available data on a stream — flotation physics has not changed, though coagulant chemistry has.