INDUSTRIES / DAIRY
Dairy effluent treatment
built around fat, whey and CIP.
Milk plant wastewater is strong, fatty and swings from acid to alkaline with every clean-in-place (CIP) cycle. A standard ETP struggles with it. We design dairy effluent treatment plants that take the fat out first, steady the pH, and turn the organic load into biogas and reusable water.
In short
How dairy wastewater is treated.
A dairy effluent treatment plant (ETP) cleans the wastewater from milk reception, pasteurisation, CIP cleaning and products such as paneer, cheese, butter and ghee. This water is rich in milk fat, protein and lactose, so it has a high BOD and COD, and its pH swings sharply with caustic and acid cleaning. It is treated in this order: screening and fat removal (fat trap and DAF), equalisation with pH correction, anaerobic treatment (UASB or a high-rate reactor) for strong effluent, aerobic polishing, and filtration and disinfection for reuse. Under CPCB's dairy standard, treated effluent must meet pH 6.5 to 8.5, BOD 100 mg/L, suspended solids 150 mg/L and oil and grease 10 mg/L, or the tighter limits in your consent.
- 3m³
- CPCB benchmark: wastewater per kilolitre of milk processed
- 100mg/L
- BOD limit in CPCB's dairy effluent standard
- 10mg/L
- Oil and grease limit for treated dairy effluent
- 94%+
- Water recoverable from paneer and cheese whey with our forward osmosis process
Your effluent
Where does dairy wastewater come from?
Almost all of it is diluted milk and cleaning water. Milk itself has a BOD of roughly 1,00,000 mg/L, so every litre of milk, cream or whey that reaches the drain adds a large load to the ETP. That is why milk loss control is the cheapest treatment step.
| Section of the plant | What goes to drain | Effect on the ETP |
|---|---|---|
| Milk reception and tanker washing | Rinse water from tankers, cans and silos with milk residues | Moderate load, large volume in the morning and evening |
| Pasteurisation and chilling | Milk-water mixtures at start-up, product change and shut-down; plate heat exchanger flushing | Sudden spikes of BOD and fat |
| CIP cleaning | Caustic soda wash (typically 1 to 2% NaOH, hot), acid wash (nitric or phosphoric acid), rinses and sanitiser | pH swings from below 4 to above 11; phosphorus and sodium; heat |
| Paneer, cheese and chhena | Whey and whey-washings; curd fines | The strongest stream: whey COD runs to tens of thousands of mg/L |
| Butter, ghee and cream | Buttermilk, ghee residue, fat-laden wash water | High oil and grease that coats pipes and biology |
| Milk powder and evaporators | Condensate from evaporating milk ("cow water"), evaporator CIP | Condensate is fairly clean and is the easiest water to recover |
| Ice cream, curd and flavoured milk | Sugar, stabilisers, fruit and colour residues | Adds easily degraded sugar; acidifies quickly in tanks |
| Utilities and colony | Boiler and cooling tower blowdown, softener regeneration, domestic sewage | Adds dissolved salts (TDS) that limit reuse |
Typical dairy effluent characteristics
| Parameter | Typical raw range | Target after treatment | Why it matters |
|---|---|---|---|
| pH | 5.5 to 9.0 on average; much wider during CIP | 6.5 to 8.5 | Acid and caustic slugs kill or upset the bacteria |
| BOD (biochemical oxygen demand) | 1,000 to 4,000 mg/L | Below 30 to 100 mg/L, per consent | Sets the size of the biological stage and the air needed |
| COD (chemical oxygen demand) | 2,000 to 7,000 mg/L | Below 100 to 250 mg/L, per consent | High COD makes an anaerobic stage worth it |
| Total suspended solids (TSS) | 300 to 1,000 mg/L | Below 50 to 150 mg/L | Curd fines and casein settle as sludge |
| Oil and grease (milk fat) | 100 to 500 mg/L | Below 10 mg/L | Coats bacteria, media and membranes; causes scum and odour |
| Total dissolved solids (TDS) | 1,000 to 5,000 mg/L, higher with heavy CIP use | As per consent; RO needed for boiler or process reuse | Rises every time water is recycled |
| Temperature | 30 to 40 °C, hotter near CIP and pasteuriser drains | Close to ambient | Warm effluent helps anaerobic treatment but cuts oxygen transfer |
BOD is the oxygen bacteria need to break down the organic matter in five days (Indian standards use 3 days at 27 °C). COD measures all oxidisable matter chemically. In dairy effluent the COD is usually 1.5 to 2 times the BOD, which means most of it is easily biodegradable.
Standards
What limits must a dairy ETP meet?
Dairies are one of the sectors with their own effluent standard under the Environment (Protection) Rules, 1986, published by CPCB. Your State Pollution Control Board writes the actual limits into your consent to operate (CTO), and these are often tighter.
| Parameter | Dairy standard | General standard, inland surface water (for comparison) |
|---|---|---|
| pH | 6.5 to 8.5 | 5.5 to 9.0 |
| BOD (3 days at 27 °C) | 100 | 30 |
| Suspended solids | 150 | 100 |
| Oil and grease | 10 | 10 |
| COD | Not specified in the dairy table | 250 |
| Wastewater generation | 3 m³ per kilolitre of milk processed (benchmark) | Not applicable |
The notified dairy standard also carries notes that relax some limits for discharge into a sewer with downstream treatment and for chilling plants that use treated water on their own land. Many boards ignore these relaxations in practice and write BOD 30 mg/L and COD 250 mg/L into new consents, especially where effluent reaches a river or drinking-water source.
Treatment
The dairy ETP, stage by stage.
The rule for dairy is fat first, pH second, biology third. If fat and pH are not handled up front, no biological process downstream will stay stable.
| Stage | What it does | Design points for dairy |
|---|---|---|
| 1. Screening | Removes curd pieces, packaging bits and debris | Fine screen (a few millimetres) so curd does not settle in the sump; easy access for daily cleaning |
| 2. Fat trap (oil and grease trap) | Lets free butterfat float and be skimmed off | Kept cool and skimmed daily; hot CIP water melts trapped fat and pushes it downstream |
| 3. Equalisation and pH correction | Holds a day's uneven flow and mixes acid and caustic washes together before dosing | Sized to absorb at least a full CIP cycle; mixed or aerated to stop it turning septic; automatic pH dosing with lime, caustic or acid |
| 4. Dissolved air flotation (DAF) | Coagulant and polymer clump emulsified fat and protein; fine air bubbles float them as scum | Published dairy studies report 50 to 80% removal of COD, TSS and fat here; jar tests choose the chemical and dose |
| 5. Anaerobic reactor (UASB or high-rate) | Bacteria without oxygen convert most of the COD into biogas | Worth it when COD stays above a few thousand mg/L; needs fat removed first, stable pH and a warm reactor |
| 6. Aerobic polishing | Extended aeration, MBBR or SBR removes the remaining BOD and some ammonia | Typical extended-aeration MLSS 1,500 to 3,000 mg/L; nutrients rarely needed because milk protein supplies nitrogen |
| 7. Clarifier and sludge dewatering | Settles the biomass; surplus sludge goes to a filter press or screw press | Watch for floating and bulking sludge (see problems below) |
| 8. Tertiary treatment | Pressure sand filter, activated carbon filter and disinfection | Meets discharge limits and supplies gardening, washing and cooling make-up water |
| 9. Reuse (optional) | UF and RO produce low-TDS water for boilers, crate washing or utilities | RO reject must go somewhere: see RO reject management |
Which scheme suits your dairy?
| Scheme | Best for | Strengths | Watch-outs |
|---|---|---|---|
| Fat trap + DAF + extended aeration | Milk chilling centres and liquid-milk plants with moderate COD | Simple, robust, easy to operate | High power for aeration; large tanks; more sludge |
| DAF + MBBR | Plants short of space, or upgrading an overloaded aeration tank | Compact; copes with load swings | Fat that escapes the DAF coats the media |
| DAF + SBR | Plants with batch discharges and one or two shifts | Good outlet quality and nitrogen removal in one tank | Depends on reliable automation |
| DAF + UASB + aerobic polish | Large dairies, cheese, paneer and powder plants with high COD | Lower power, less sludge, biogas for the boiler | Slow start-up; sensitive to fat, temperature and pH shocks |
| Any of the above + MBR or UF/RO | Plants that must reuse water or are under ZLD conditions | Reuse-quality water; small footprint | Membrane cleaning and replacement cost; reject handling |
Published studies show UASB reactors on dairy effluent removing anywhere from about 60% to over 90% of COD, depending mainly on reactor temperature, sludge age and how well fat is removed beforehand. We size the anaerobic stage on your measured load, not on best-case figures.
Our NABL-accredited laboratory tests composite samples across a full CIP and production cycle for pH, BOD, COD, TSS, TDS, oil and grease, nitrogen and phosphorus, so the plant is sized for your real load.
Recovery
Biogas, whey and water: what a dairy can recover.
Keep whey out of the drain
Whey from paneer, cheese and chhena carries most of a small dairy's organic load in a fraction of its water. Sending it to the ETP can double or triple the plant you need. Segregate it and use it: whey drinks, whey powder, animal feed, or a biogas digester. Our dairy whey water recovery process uses field-proven forward osmosis to recover over 94% of the water in paneer and cheese whey and concentrate the lactose about 12-fold, using under 8 kWh per tonne.
Biogas from the anaerobic stage
An anaerobic reactor turns COD into methane. In theory each kilogram of COD removed can give up to about 0.35 m³ of methane; real plants get less. The biogas, usually 60 to 70% methane, can replace furnace oil, LPG or briquettes in the boiler. It pays back fastest at large plants and plants that make cheese or paneer. See waste-to-energy and biogas.
Water reuse
Treated, filtered and disinfected effluent suits gardening, floor and crate washing, and cooling tower make-up. For boiler feed or CIP rinses it needs UF and RO. Evaporator condensate from milk powder plants is the easiest stream to recover, often with only polishing. Soft water for boilers comes from our industrial water softeners.
Sludge and DAF float
DAF float is mostly fat and protein; it can feed a digester instead of going to landfill. Dewatered biological sludge is often used as manure where the board allows it, after a sludge test.
Cost
How much does a dairy ETP cost?
For a dairy, the organic load matters more than the flow. Two plants of the same KLD can differ by a factor of two in cost if one sends whey to drain. These ranges are for budgeting before we see your data.
| ETP capacity | Typical dairy | Usual scheme | Indicative plant cost* |
|---|---|---|---|
| 20 to 50 KLD | Chilling centre, small paneer or curd unit | Fat trap, equalisation, DAF or packaged aerobic plant | ₹12 to 35 lakh |
| 100 KLD | Liquid milk plant processing several tens of thousands of litres a day | Fat trap, DAF, extended aeration or MBBR, tertiary | ₹35 to 75 lakh |
| 300 KLD | Mid-size dairy with products | DAF, MBBR or SBR; UASB if COD is high | ₹80 lakh to 1.8 crore |
| 500 KLD and above | Large dairy, cheese or powder plant | DAF, UASB with biogas use, aerobic polish, reuse | ₹1.5 crore upwards |
*Indicative 2026 ranges for equipment, electricals and installation, excluding land, civil works, taxes, RO and ZLD stages and biogas utilisation equipment. A dairy that segregates whey and controls milk losses needs a smaller plant. We give a firm price only after testing your effluent and visiting the site.
What raises the cost
- Whey and buttermilk sent to drain
- Strict consent limits (BOD 30, COD 250 or reuse)
- Little space, so compact processes
- RO for boiler-quality reuse
- Seasonal peaks in the flush season
What drives running cost
- Aeration power, the largest item
- DAF coagulant and polymer
- pH correction chemicals after CIP
- Sludge and fat disposal
- Operators and daily lab checks
What brings it down
- Milk loss audits and drip trays
- Recovering CIP solutions instead of dumping
- Anaerobic stage with biogas use
- Blower speed control on dissolved oxygen
- Chemicals chosen by jar test
We audit existing dairy ETPs stage by stage, tune DAF dosing and aeration, retrofit MBBR into old tanks and supply treatment chemicals tested on your effluent.
Troubleshooting
Common dairy ETP problems, and how we fix them.
- 01The problem
Fat builds up in sumps, pipes and the aeration tank; thick scum forms.
What we doKeep hot CIP water away from the fat trap, fix skimming routines, and add or re-tune a DAF with the right coagulant so fat stops reaching the biology.
- 02The problem
Sludge will not settle and pours over the clarifier weir (filamentous bulking).
What we doIdentify the filaments under the microscope; dairy bulking is usually caused by fat, low dissolved oxygen or a low food-to-microorganism ratio. We fix the cause, then use a selector or temporary dosing if needed.
- 03The problem
Bad odour from the equalisation tank and a sour, acidic effluent.
What we doMilk sugar ferments fast without oxygen. We add mixing or aeration in equalisation, shorten hold-up in sumps and automate pH correction.
- 04The problem
Biology dies or the UASB sours after a CIP dump or a milk spill.
What we doAdd a diversion tank for spills and spent CIP, online pH alarms at the inlet, and controlled feeding from equalisation instead of direct flow.
- 05The problem
The plant copes in summer but fails in the winter flush season when milk intake peaks.
What we doRe-rate the plant on peak-season load, add MBBR media or a DAF to raise capacity in the same tanks, and plan the anaerobic stage for cold-weather temperatures.
What we offer
Rispri services for dairies.
Dairy ETP and STP
Design, build, commissioning and upgrades of dairy effluent and sewage plants.
Effluent treatment plants →Effluent and water testing
NABL-accredited tests for design, consent renewal and monthly compliance.
Water and wastewater testing →Whey water recovery
Forward osmosis that recovers water and concentrates lactose from whey.
Whey water recovery →Biogas from effluent and waste
Anaerobic reactors and digesters that turn dairy load into boiler fuel.
Waste-to-energy →Treatment chemicals and soft water
DAF coagulants, polymers, boiler and cooling chemicals, and softeners for boiler feed.
Water treatment chemicals →ZLD and evaporators
RO reject evaporation with air instead of steam, at a fraction of MEE cost.
Non-thermal evaporators →Buying guide
What to ask before you buy a dairy ETP.
Use this list with any supplier, including us.
- Was the design based on composite samples across CIP and production? A single grab sample misses the peaks.
- How is fat removed before the biology? Ask for the fat trap and DAF design, not just the aeration tank.
- How big is equalisation, and is pH corrected automatically? It must absorb a full CIP cycle.
- Is whey kept out of the design load? If not, ask what it would cost to segregate it.
- Which outlet values are guaranteed in writing? Against the limits in your consent, not the dairy table alone.
- What are power and chemical costs per cubic metre? With the calculation behind them.
- Is biogas recovery worth it at my scale? Ask for a simple payback estimate.
- Who operates it and who tests the outlet? Training, O&M support and NABL-accredited reports.
Why Rispri
One team from sample to running plant.
Our own NABL lab
We test your dairy effluent before design and certify the outlet after start-up.
Engineering since 1999
1,498+ plants and turnkey projects for industries, hotels, hospitals and cities.
Research collaborations
Proven whey water recovery, RO reject recovery and non-thermal evaporation, in collaboration with IIT Bombay, IIT Kharagpur and ICT Mumbai.
Chemicals, spares and O&M
Our own treatment chemicals, softeners and spares, plus operation and maintenance contracts.
Questions
Dairy effluent treatment FAQs.
What is a dairy effluent treatment plant?
A dairy effluent treatment plant is an ETP designed for milk plant wastewater, which is high in fat, protein and lactose and swings in pH with CIP cleaning. It usually combines a fat trap and DAF, equalisation with pH correction, anaerobic and aerobic biological treatment, and filtration and disinfection.
What are the CPCB standards for dairy effluent?
CPCB's dairy effluent standard sets pH 6.5 to 8.5, BOD 100 mg/L, suspended solids 150 mg/L and oil and grease 10 mg/L, with a benchmark of 3 m³ of wastewater per kilolitre of milk processed. Your state board's consent to operate can be stricter and often is.
Does CPCB set a COD limit for dairy effluent?
The dairy-specific table does not list a COD limit; it covers pH, BOD, suspended solids and oil and grease. Many consents still specify COD, often 250 mg/L from the general standards, so check your own CTO.
How much wastewater does a dairy produce?
Well-run dairies produce roughly 1 to 3 litres of wastewater per litre of milk processed; older plants with more losses produce more. CPCB uses 3 m³ per kilolitre of milk as its benchmark.
Why is fat removal so important in a dairy ETP?
Milk fat coats bacteria, MBBR media and membranes, causes scum and odour, and encourages filamentous bulking. Removing it with a fat trap and DAF before the biological stage keeps the rest of the plant stable and cheaper to run.
Is UASB suitable for dairy wastewater?
Yes, when the COD stays high, typically above a few thousand mg/L, and fat is removed first. It cuts power and sludge and produces biogas, but it needs stable pH and temperature and a careful start-up. Small dairies with weak effluent are usually better off with aerobic treatment only.
How much does a dairy ETP cost in India?
As an indication, a 100 KLD dairy ETP costs about ₹35 to 75 lakh for equipment and installation, excluding civil work, land, taxes and RO. Cost depends mostly on how strong the effluent is, so we price after testing it.
Can a dairy reuse its treated effluent?
Yes. Filtered and disinfected effluent suits gardening, washing and cooling towers, and UF plus RO makes it fit for boilers and utilities. Evaporator condensate from powder plants is the easiest stream to recover.
What should a dairy do with whey?
Keep it out of the ETP if you can. Whey is valuable as a product or feed and is far stronger than other wastewater. Where it must be handled on site, a digester or our forward osmosis whey water recovery process recovers water and concentrates the lactose.
Why does my dairy ETP smell?
Lactose ferments quickly when wastewater sits without oxygen, producing acids and odour, and trapped fat goes rancid. Mixing or aerating the equalisation tank, cleaning fat traps and avoiding long hold-ups usually solves it.
How do I handle CIP wastewater?
Recover and reuse CIP caustic and acid where possible, and send spent solutions to equalisation slowly so they neutralise each other. Automatic pH dosing before the biology protects it from shocks.
Is dairy ETP sludge hazardous waste?
Biological sludge from a dairy ETP is usually treated as non-hazardous, and is often used as manure where the board permits. Your consent and SPCB decide, so we test the sludge and follow their direction.
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