DAF systems and equipment
Dissolved air flotation plant from 2 to 1,200 m³/h, in four configurations. The right one is decided by flow, by how much civil work the site can absorb, and by how aggressive the effluent is.
DAF systems fall into four types. Packaged skid units (2–150 m³/h) arrive pre-piped and pre-wired and need only a level slab — the default for single industrial sites. High-rate cells (200–1,200 m³/h) run at 15–30 m/h for municipal works and large industrial duty. Containerised plant (5–60 m³/h) puts the whole treatment train inside a 20 or 40 ft shipping container for remote or temporary sites. Circular flotation cells suit sludge thickening and large-diameter municipal duty. Every configuration shares the same three sub-systems: a saturator and recycle loop, a coagulation and flocculation stage, and the flotation cell with skimmer.
Choose by flow and site constraint
Capacity and footprint table
| Model class | Flow m³/h | Flotation area m² | Overall footprint | Installed power | Typical duty |
|---|---|---|---|---|---|
| Micro packaged | 2 – 10 | 0.4 – 1.5 | 2.2 × 1.2 m | 2 – 4 kW | Car wash, small dairy, laundry |
| Small packaged | 10 – 30 | 1.5 – 4 | 3.5 × 1.6 m | 4 – 9 kW | Abattoir, small food plant |
| Medium packaged | 30 – 80 | 4 – 11 | 6.0 × 2.2 m | 9 – 20 kW | Brewery, edible oil, tannery |
| Large packaged | 80 – 150 | 11 – 20 | 9.5 × 2.6 m | 20 – 35 kW | Large food plant, paper saveall |
| High-rate cell | 200 – 500 | 10 – 25 | 7.0 × 4.0 m | 35 – 70 kW | Municipal, WWTP uprating |
| High-rate, multi-cell | 500 – 1,200 | 25 – 60 | Site specific | 70 – 160 kW | Large municipal, surface water |
| Containerised | 5 – 60 | 1 – 8 | 20 or 40 ft ISO | 6 – 25 kW | Remote, temporary, rental |
What is on a complete skid
- Flotation cell with inclined plate or open flotation zone, adjustable effluent weir and sludge hopper.
- Surface skimmer — chain-and-flight or rotating blade, variable speed, with a bottom scraper where settleable solids are present.
- Saturator — pressure vessel at 4–6 bar with packed or unpacked contact section, level control, safety relief and air injection.
- Recycle pump — multistage centrifugal, sized on the calculated recycle flow at saturator pressure, not on a percentage rule of thumb.
- Air supply — oil-free compressor or blower with receiver, dryer and pressure regulation.
- Release nozzles or needle valves — the component that determines bubble size distribution and therefore performance.
- Coagulation and flocculation stage — inline static mixer or stirred chambers with 1–3 min flocculation at G of 30–70 s⁻¹.
- Dosing skid — coagulant, polymer make-up and dosing, pH correction, all with calibration columns.
- Control panel — PLC with HMI, level and pressure instrumentation, optional pH and turbidity monitoring, remote access.
Materials of construction
Materials are selected against your effluent, not against a price list. This is the specification decision with the largest effect on whole-life cost, and the one most often compromised to win a price comparison.
| Material | Use where | Avoid where | Relative cost |
|---|---|---|---|
| Carbon steel + epoxy | Neutral pH, chloride <200 mg/L, municipal, brewery, paper effluent | Any acid or chloride exposure | 1.0 |
| SS304 | Food, dairy, general industrial, warm water | Chloride >200 mg/L, pH <4 | 1.3 – 1.5 |
| SS316L | Edible oil, textile, chloride to ~5,000 mg/L, low pH | Chloride >5,000 mg/L at elevated temperature | 1.6 – 1.9 |
| Duplex 2205 | Tannery, mining, produced water, high chloride | Rarely — cost is the constraint | 2.2 – 2.8 |
| GRP / FRP | Chemically aggressive, corrosive vapour, coastal sites | High mechanical loading, UV without gelcoat | 1.2 – 1.8 |
| Concrete + lining | Large municipal cells, permanent installations | Where speed of delivery matters | Site dependent |
Scope of supply and delivery
Standard scope covers process sizing and design, the flotation unit with saturator and recycle system, the coagulation and flocculation stage, dosing skid, control panel and instrumentation, documentation (general arrangement, P&ID, foundation loading, electrical schedule, O&M manual, commissioning procedure), and commissioning support on site. Delivery is CIF to any African port.
Installation is normally executed by a local contractor to our drawings, which keeps mobilisation cost and time down. Full scope of services →
Frequently asked questions
What is the difference between conventional and high-rate DAF?
Surface loading rate and internal hydraulics. A conventional DAF runs at 5–12 m/h in an open rectangular flotation zone. A high-rate unit runs at 15–30 m/h using engineered inlet distribution and often inclined plates in the separation zone to maintain the bubble blanket at higher velocity. High-rate gives two to three times the throughput per square metre but is less tolerant of variable influent and needs more attentive chemical control.
How much space does a DAF need?
A 30 m³/h packaged unit occupies roughly 3.5 × 1.6 m of skid, and about 6 × 4 m including access, chemical storage and the dosing skid. A 500 m³/h high-rate cell occupies about 7 × 4 m of tank and 12 × 9 m of plant area. Both need a balance tank upstream, which is often the larger structure — and the one most frequently omitted from a supplier’s footprint drawing.
What is the lead time for a DAF unit?
Typically 8–14 weeks from order for packaged carbon steel or SS304 units, 12–20 weeks for stainless and duplex, and longer where the control philosophy is bespoke. Sea freight to an African port adds 3–7 weeks depending on routing. Jar testing and process confirmation should be complete before the order is placed, not during manufacture.
Can a DAF be rented rather than bought?
Containerised units are suited to rental and short-campaign duty — mine site dewatering, construction, a factory bridging a compliance deadline, or a pilot before committing to a permanent plant. The economics generally favour purchase beyond about twelve to eighteen months of continuous operation.