Brewery Wastewater Treatment with DAF

Dissolved air flotation removes 85–95% of suspended solids from brewery effluent — spent yeast, trub, kieselguhr fines and grain particles — but only 25–45% of COD, because brewery COD is overwhelmingly soluble. DAF is therefore a pretreatment step in a brewery, not a complete solution: it protects and de-loads the biological stage that follows.

Any proposal claiming a DAF alone will bring brewery effluent to a discharge consent that includes COD is wrong. This page sets out what the technology actually does with this stream, and how to size it.

Brewery effluent characteristics

Parameter	Typical range	Notes
Effluent volume	3 – 10 hL per hL beer	Modern efficient plants 3–5; older plants 7–10
COD	2,000 – 6,000 mg/L	Mostly soluble — sugars, ethanol, organic acids
BOD₅	1,200 – 3,600 mg/L	Highly biodegradable, COD:BOD around 1.6:1
TSS	200 – 1,000 mg/L	Yeast, trub, spent grain fines, filter aid
pH	3 – 12	Swings violently with CIP cycles
Temperature	25 – 40 °C	Matters for air solubility — see below
Total nitrogen	25 – 80 mg/L	Mainly from yeast
Total phosphorus	10 – 50 mg/L	Partly from phosphoric acid CIP
FOG	10 – 100 mg/L	Low compared with other food industries

Why brewery COD does not respond to DAF

Flotation is a physical separation process. It can only remove what exists as a particle or an emulsified droplet. Brewery COD is dominated by dissolved sugars, ethanol, and organic acids — molecules in true solution, which no bubble can attach to.

Parameter	DAF removal	Why
TSS	85 – 95%	Particulate — yeast, trub, grain fines float readily
COD	25 – 45%	Only the particulate fraction; soluble COD passes straight through
BOD₅	20 – 40%	As above
Total phosphorus	70 – 90%	With metal-salt coagulant dosing
Turbidity	85 – 95%	Tracks TSS

This is not a failing of the equipment. Removing 90% of the suspended solids and 35% of the COD ahead of an anaerobic or activated sludge stage is exactly what a brewery DAF is for. It cuts the organic load the biology has to handle, prevents solids accumulating in reactors, and stabilises what reaches the downstream process.

Where DAF sits in a brewery treatment train

A typical configuration for a brewery discharging to sewer or to surface water:

1. Screening — removes grain, labels, crown corks, glass fragments
2. Balance tank — the single most important unit in a brewery ETP. Evens out flow, temperature and above all pH between brews and CIP cycles
3. pH correction — to bring the stream into the coagulant’s working window
4. Coagulation and flocculation
5. DAF — solids removal, phosphorus removal, partial COD reduction
6. Biological stage — UASB or other anaerobic reactor for high-strength streams, or activated sludge/SBR
7. Polishing where the consent demands it

Skipping the balance tank is the most expensive false economy in brewery effluent treatment. A DAF fed directly from the drain sees pH 3 one hour and pH 12 the next as CIP caustic and acid arrive, and no coagulant works across that range. Sites that install a DAF without adequate balancing almost always report “the chemicals don’t work” within the first month.

Chemical regime

• pH correction: to 5.5–6.5 for ferric, 6.0–7.0 for aluminium-based coagulants. Brewery effluent is often acidic and needs caustic, but post-CIP slugs can need acid instead — dosing must be bidirectional
• Coagulant: ferric chloride 50–200 mg/L, or PAC 30–150 mg/L. Ferric performs well where phosphorus removal is also required
• Flocculant: anionic polyacrylamide 1–5 mg/L, typically. Yeast flocs are fragile — over-dosing polymer or over-mixing shears them and performance drops
• Contact time: 1–3 minutes rapid mix, 10–20 minutes flocculation at low velocity gradient

These are starting points for a jar test, not a prescription. Dose depends on your raw materials, filtration regime and CIP chemistry, and it will differ between two breweries producing the same beer.

The temperature problem in African breweries

Brewery effluent runs warm — 25–40 °C from wort cooling, bottle washing and hot CIP. Air solubility falls as water warms, and this is not a trivial correction.

Effluent temperature	Air solubility	Air delivered vs 20 °C design
20 °C	18.7 mL/L	baseline
30 °C	15.7 mL/L	−16%
35 °C	~15.0 mL/L	−20%
40 °C	14.2 mL/L	−24%

A DAF specified against 20 °C data and fed 35 °C brewery effluent delivers about a fifth less air than the design assumed, and the air-to-solids ratio falls with it. The unit then underperforms in a way that looks like a chemistry problem and gets treated as one, expensively and unsuccessfully. State your effluent temperature in the enquiry. A supplier who does not ask for it is not sizing your plant, they are sizing a generic one.

Worked example: 500,000 hL/year brewery

Basis: 500,000 hL beer/year, 5 hL effluent per hL beer, 300 operating days, 20 operating hours/day. Influent TSS 600 mg/L, effluent temperature 32 °C, target A/S 0.025, saturator 500 kPa gauge at 70% efficiency, conventional loading 8 m/h.

1. Annual effluent: 500,000 × 5 = 2,500,000 hL = 250,000 m³/year
2. Average flow: 250,000 ÷ (300 × 20) ≈ 42 m³/h
3. Design flow with peaking factor 1.5: ≈ 63 m³/h
4. Solids load: 63 × 600 ÷ 1,000 = 37.8 kg TSS/h
5. Air required: 37.8 × 0.025 = 0.95 kg/h
6. Air released per m³ recycle at 32 °C: s_a ≈ 15.4 mL/L; 1.3 × 15.4 × (0.7 × 5.94 − 1) ≈ 63 g/m³
7. Recycle flow: 945 ÷ 63 ≈ 15 m³/h → recycle ratio ≈ 24%
8. Total flow: 63 + 15 = 78 m³/h
9. Flotation area: 78 ÷ 8 ≈ 9.8 m² — say a 5.0 m × 2.0 m cell

Note what the temperature did. At 20 °C the same duty would need about 12.5 m³/h recycle; at 32 °C it needs 15 m³/h — 20% more pump and more hydraulic load on the cell. Design on the temperature you actually have.

Run your own numbers with the DAF sizing calculator.

Recovering value from the float

Brewery DAF float is 2–5% dry solids and consists largely of yeast and trub. Where it has not been contaminated with coagulant metals, it has value as animal feed, and several African breweries already route spent yeast to feed markets. Coagulant choice affects this: heavy ferric or aluminium dosing produces a float that is generally unsuitable for feed. If feed recovery matters to you, raise it before the chemical regime is fixed, not after.

Frequently asked questions

Can a DAF treat brewery wastewater on its own?

Only where the discharge consent covers suspended solids and pH but not COD or BOD. Brewery COD is mostly soluble and DAF removes just 25–45% of it, so any consent with a meaningful COD limit requires a biological stage after the DAF.

How much wastewater does a brewery produce?

Between 3 and 10 hectolitres of effluent per hectolitre of beer. Efficient modern plants achieve 3–5; older facilities with high water use run at 7–10. Water efficiency projects therefore reduce effluent plant sizing directly.

What COD does brewery effluent have?

Typically 2,000–6,000 mg/L, with BOD₅ of 1,200–3,600 mg/L. The stream is highly biodegradable, which makes it well suited to anaerobic treatment with biogas recovery once the solids have been taken out.

Why does brewery pH swing so much?

Clean-in-place cycles alternate caustic and acid, and both end up in the drain. Without an adequately sized balance tank the DAF sees pH 3 to pH 12 within a shift, and no coagulant works across that range. Balancing is not optional in a brewery.

---

Related: Complete DAF technical guide for Africa · DAF design parameters · Sizing calculator · Abattoir wastewater

Last reviewed July 2026. Ranges are indicative; confirm by composite sampling and jar test on your own effluent.