CPCB Source Document
CPCB Comprehensive Industry Document — Dairy Industry; Schedule VI, Environment (Protection) Rules 1986
Authority: CPCB under Environment (Protection) Act 1986 · Applicable to all dairy processing plants
View effluent standards on cpcb.nic.in ↗CPCB website links may change — search "dairy effluent standards" on cpcb.nic.in if the link is broken.
Why Dairy Effluent Requires Careful Treatment
Dairy processing is one of India's largest agro-industrial sectors — handling over 230 million tonnes of milk annually. Dairy wastewater is generated from washing of milking equipment, pasteurisation plant cleaning, butter and ghee production, cheese making, milk powder spray dryers, and CIP (Clean-In-Place) operations. Despite appearing relatively harmless, this effluent has very high organic strength — milk spills and dairy residues are among the highest BOD-per-unit-volume streams in the food industry.
Untreated dairy effluent discharged to rivers or water bodies rapidly depletes dissolved oxygen, killing fish and aquatic life. CPCB classifies most dairy processing plants as Orange or Red category industries requiring formal consent and ETP installation.
CPCB Pollution Category for Dairy Plants
CPCB's industry categorization places dairy units based on production scale:
- Green category: Small milk chilling centres and BMCs handling raw milk collection only — minimal wastewater generation, exempt from ETP requirements.
- Orange category: Dairy plants processing 10,000–50,000 litres/day including pasteurisation, homogenisation, and packaging — must obtain Consent to Operate and install ETP.
- Red category: Large dairies (>50,000 litres/day), cooperative dairy plants, integrated units producing multiple products (ghee, cheese, milk powder, UHT) — full ETP required with monthly third-party monitoring.
Effluent Characteristics of Dairy Wastewater
Dairy effluent characteristics vary by product but typically include:
- High BOD: 500–3,000 mg/L — from milk solids, lactose, fat, and protein losses during processing and cleaning.
- High COD: 1,000–5,000 mg/L from the same organic fractions.
- High fat content: 100–400 mg/L oil & grease — from cream, butter, and ghee production areas.
- Alkaline pH: CIP cleaning with NaOH makes dairy effluent alkaline (pH 8–12) during cleaning cycles; acid cleaning with HNO₃ makes it acidic — pH swings require equalization.
- High TKN: From milk proteins — requires biological nitrification if discharge is to sensitive water bodies.
- Phosphorus: From milk and detergent residues — may require chemical precipitation for sensitive receiving waters.
CPCB Discharge Standards: Key Parameters
| Parameter | Inland Surface Water | Public Sewer |
|---|---|---|
| pH | 6.5–8.5 | 5.5–9.0 |
| BOD (5-day, 20°C) | ≤ 30 mg/L | ≤ 350 mg/L |
| COD | ≤ 250 mg/L | ≤ 600 mg/L |
| Total Suspended Solids | ≤ 100 mg/L | ≤ 600 mg/L |
| Oil & Grease | ≤ 10 mg/L | ≤ 20 mg/L |
| Total Kjeldahl Nitrogen | ≤ 100 mg/L | — |
| Total Phosphorus | ≤ 5 mg/L | — |
| Temperature | ≤ 40°C | ≤ 45°C |
Recommended ETP Configuration for Dairy Units
A typical dairy ETP consists of:
- Screen and grease trap: Removes milk solids and floating fat before primary treatment.
- Equalisation tank: Critical for dairy ETPs due to highly variable pH (alkaline during NaOH CIP, acidic during HNO₃ CIP) and flow (peaks at end of each shift).
- Dissolved Air Flotation (DAF): Most effective primary treatment for dairy — removes 80–95% of fat and 40–60% of BOD by floating fat-protein complexes to the surface for skimming.
- Biological treatment: Extended aeration, SBR, or MBBR removes remaining BOD to <30 mg/L. UASB or anaerobic contact process is cost-effective for high-strength streams (cheese whey, cream wash).
- Secondary clarifier and polishing: Clarification and multimedia filtration to meet TSS standards.
Fat, Oil, and Grease Management
Fat management is the key operational challenge in dairy ETPs:
- Grease traps at kitchen and processing area drains capture gross fat before it enters the main ETP.
- DAF units use pressurised water dissolved with air — released bubbles attach to fat globules and float them to the surface as a fat-rich cream skimmings.
- Skimmings from DAF must be collected and disposed — they can be co-processed in cement kilns or sent to waste cooking oil recyclers if quality allows.
- Heating dairy effluent before DAF improves fat removal efficiency — fat liquefies above 40°C and floats more readily.
Sludge Management and Reuse
Dairy ETP sludge is typically non-hazardous and amenable to composting or land application:
- Biological sludge from dairy ETPs is protein and fat-rich — making it a high-quality compost feedstock when mixed with carbonaceous bulking agents.
- Sludge should be tested for pathogens (E. coli, Salmonella) before use as agricultural compost — pathogens from dairy can persist in sludge if not treated.
- Filter-pressed sludge cake (25–35% dry solids) from dairy ETPs can be used directly as soil amendment in nearby farms.
Consent Requirements and Compliance Documentation
Orange and Red category dairy plants must maintain:
- Consent to Establish and Operate from the State PCB — renewed annually or as specified.
- Monthly effluent monitoring by NABL-accredited third-party lab — covering all consent parameters.
- ETP operation log: Daily records of flow treated, chemical dosing, MLSS, and effluent quality.
- Annual environment statement under EP (Amendment) Rules 1993.
- OCEMS for large plants (>1 MLD wastewater generation) — as per CPCB directions.
Need Help with Dairy ETP Design or Compliance?
Spans Envirotech designs and commissions ETPs for dairy plants — from small cooperative dairies to large integrated milk processing complexes.
Contact us: bd@spans.co.in · +91-98100 00233
Frequently Asked Questions
What BOD limit applies to dairy plant effluent?
CPCB prescribes BOD ≤ 30 mg/L for dairy effluent discharged to inland surface water. For discharge to public sewers, BOD up to 350 mg/L is typically permitted by the local ULB, but the receiving water body standard of ≤ 30 mg/L must ultimately be met at the final disposal point.
Why is dairy effluent high in BOD?
Dairy wastewater contains milk solids, fat, lactose, proteins, and cleaning chemicals — all of which exert significant oxygen demand when discharged to water bodies. A single litre of whole milk can have a BOD of 100,000 mg/L; even small milk losses in cleaning water dramatically increase the BOD of the resulting effluent stream.
What treatment is recommended for dairy effluent?
CPCB recommends a combination of dissolved air flotation (DAF) for fat/oil removal, followed by biological treatment (activated sludge or SBR) for BOD reduction, and tertiary polishing. Anaerobic pre-treatment (UASB or anaerobic pond) is beneficial for high-strength streams from cheese or casein production.
Do small milk collection centres need an ETP?
Small bulk milk cooling (BMC) centres with minimal water use may be Green category and exempt from ETP requirements. However, dairy processing plants (pasteurisation, ghee, cheese, ice cream, powder) are Orange or Red category and must install ETPs and obtain Consent to Operate from the State PCB.
Can dairy sludge be composted?
Yes. Biological sludge from dairy ETPs is typically non-hazardous and protein-rich — making it suitable for composting. The resulting compost is a useful soil amendment. However, sludge must be tested to confirm it is free from heavy metals or harmful pathogens before land application.
This article summarises CPCB norms for dairy industry effluent for informational purposes. Always verify current standards with your State Pollution Control Board.