India's CPCB Wastewater Discharge Standards: What Industrial Operators Need to Know
India's CPCB wastewater discharge standards under the Environment (Protection) Rules, 1986 Schedule VI set inland-surface-water limits at BOD 30 mg/L, COD 250 mg/L, TSS 100 mg/L, pH 5.5–9.0, and oil & grease 10 mg/L. Separate columns cover public sewers, land for irrigation, and marine coastal areas. SPCBs such as MPCB and TNPCB may set stricter consent limits.
The Role of the CPCB and SPCBs in Industrial Compliance
The CPCB, established under the Water (Prevention and Control of Pollution) Act, 1974, is India's national authority for industrial wastewater standards. It publishes the General Standards for Discharge of Environmental Pollutants Part-A: Effluents, which every factory discharging wastewater must satisfy. Penalties for non-compliance include daily fines, consent revocation, and operational shutdowns.
Day-to-day enforcement runs through State Pollution Control Boards. A textile plant in Gujarat and a pharmaceutical unit in Telangana will see different consent conditions, even though the CPCB baseline is identical, because SPCBs can tighten limits based on local river assimilative capacity or downstream drinking-water intakes. In sizing a treatment train, the binding number is almost always the SPCB consent, not the CPCB schedule.
The core parameters — BOD, COD, TSS, pH, oil & grease, ammoniacal nitrogen, and total residual chlorine — protect against oxygen depletion, toxicity, eutrophication, and infrastructure corrosion. Getting these right early in ETP design is cheaper than retrofitting after consent refusal.
General Standards for Discharge of Environmental Pollutants Part-A: Effluents
Schedule VI of the Environment (Protection) Rules, 1986 defines four discharge scenarios, each with its own parameter limits. The table below consolidates the current CPCB wastewater discharge standards and is the reference most consent engineers work from:
| Parameter | Inland Surface Water | Public Sewers | Land for Irrigation | Marine Coastal Areas |
|---|---|---|---|---|
| Colour and odour | Shall not be objectionable | Shall not be objectionable | Shall not be objectionable | Shall not be objectionable |
| Suspended Solids (mg/L, max) | 100 (process wastewater) 10% above influent (cooling water) |
600 | 200 | 100 (process wastewater) |
| Particulate size of suspended solids | Shall pass 850-micron IS sieve | — | — | Floatable solids: <3 mm Settleable solids: <850 microns |
| pH Value | 5.5–9.0 | 5.5–9.0 | 5.5–9.0 | 5.5–9.0 |
| Temperature | Shall not exceed 5°C above receiving water temperature | — | — | Shall not exceed 5°C above receiving water temperature |
| Oil and Grease (mg/L, max) | 10 | 20 | 10 | 20 |
| Total Residual Chlorine (mg/L, max) | 1.0 | — | — | 1.0 |
| Ammonical Nitrogen (as N, mg/L, max) | 50 | 50 | — | 50 |
| Total Kjeldahl Nitrogen (as NH₃, mg/L, max) | 100 | — | — | 100 |
| Biochemical Oxygen Demand (BOD, mg/L, max) | 30 | 350 | 100 | 100 |
| Chemical Oxygen Demand (COD, mg/L, max) | 250 | — | — | 250 |
These are minimum national limits. Industry-specific schedules (textiles, pharmaceuticals, tanneries, sugar, distilleries, iron & steel) layer additional or tighter thresholds on top. For a deeper breakdown of one commonly cited threshold, see our guide to cpcb oil and grease discharge limit 10 mg/l inland surface water.
Key Parameters: Industrial Significance and Monitoring
Each limit in the schedule exists because the parameter causes a specific harm downstream. Reading them as engineering numbers, not as paperwork, is what separates a passing ETP from a consent violation.
Biochemical Oxygen Demand (BOD)
Limit: 30 mg/L for discharge to inland surface water.
Significance: BOD measures oxygen consumed by microbes breaking down organic matter. High BOD strips dissolved oxygen from rivers and triggers fish kills. Food processing, distillery, and pulp & paper plants generate the highest BOD loads and must design biological stages around this 30 mg/L ceiling.
Monitoring: Under Indian CPCB methods, BOD is measured over 3 days at 27°C. Most plants we size run between 18–25 mg/L at the ETP outlet to leave headroom for sampling variability.
Chemical Oxygen Demand (COD)
Limit: 250 mg/L for discharge to inland surface water.
Significance: COD captures both biodegradable and non-biodegradable oxidisable matter, so it always exceeds BOD. A COD/BOD ratio above 3 typically signals refractory organics that need tertiary polishing. Refineries and chemical plants lean on MBR systems or advanced oxidation to close this gap.
Monitoring: COD tests complete in 2–4 hours using closed-reflux colorimetric methods, which is why operators use it for daily process control.
Total Suspended Solids (TSS)
Limit: 100 mg/L for inland surface water, 600 mg/L for public sewers.
Significance: TSS smothers benthic habitat, blocks UV disinfection, and clogs drip irrigation. Mining, textile, and metal-finishing streams need consistent removal; most plants we audit hit 60–80 mg/L with a well-tuned DAF unit ahead of the biological stage.
Monitoring: Gravimetric TSS via 1.2 µm filter papers, run daily at minimum.
pH Value
Limit: 5.5–9.0 across all four discharge scenarios.
Significance: Out-of-range pH corrodes sewers, kills aquatic life, and crashes nitrification. Electroplating and tannery streams often swing by 2–3 pH units during a shift, so inline neutralisation with redundant dosing pumps is the safe path.
Monitoring: Continuous inline pH meters with auto-shutoff on the discharge line.
Oil and Grease
Limit: 10 mg/L for inland surface water, 20 mg/L for public sewers.
Significance: Oil films cut oxygen transfer and clog diffusers. Petroleum, metalworking, and edible-oil plants should plan oil-water separators as the first unit operation, not an afterthought.
Monitoring: Solvent extraction (n-hexane) on a weekly composite sample.
Nitrogen Compounds (Ammonical Nitrogen and TKN)
Limits: Ammoniacal N 50 mg/L, TKN 100 mg/L for inland and marine discharge.
Significance: Excess nitrogen drives eutrophication. Fertilizer, pharma, and food plants typically need a dedicated nitrification-denitrification stage or an MBR system to land below 50 mg/L ammoniacal N.
Monitoring: Daily colorimetric ammonia; weekly TKN by digestion/distillation.
For guidance on instrumentation choices for COD, ammonia, and total phosphorus, refer to our analyzer selection guide.
Treatment Train Design for CPCB Compliance
A compliant ETP is a sequence of unit operations, each sized against the binding parameter at its outlet. The five-step framework below covers most Indian industrial streams.
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Wastewater Characterization:
Profile at least one week of composite samples for BOD, COD, TSS, pH, oil & grease, ammoniacal N, and any sector-specific metals. Without this baseline, treatment design is guesswork.
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Regulatory Assessment:
Match the characterization against CPCB Schedule VI and your SPCB consent. The textile sector, for example, carries additional limits on colour and chromium that the general schedule does not list.
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Treatment Plant Design:
A typical train for inland-surface-water discharge runs:
- Pre-treatment: Screening, flow equalisation, oil & grease removal via DAF.
- Primary: Clarifier or flotation for settleables and TSS.
- Secondary biological: Activated sludge, SBR, or MBR to cut BOD/COD and nitrify ammonia.
- Tertiary: Sand/UF filtration, disinfection via chlorine dioxide or UV, plus polishing for residual COD.
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Implementation and Optimisation:
Targets worth writing into your operating manual: HRT 6–8 h at 20°C for conventional activated sludge, MLSS 3,000–4,000 mg/L, F/M 0.2–0.4/day, and SVI below 150 mL/g. Dewater sludge with plate-and-frame filter presses to reach 22–25% DS.
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Monitoring and Reporting:
Online sensors for pH, TSS, COD, and flow on the final outlet, with a data logger that archives at least one year of records for SPCB audits.
For the process in more detail, see our 7-step wastewater treatment guide, and for sizing equipment, the industrial wastewater treatment equipment selection guide.
Steel Plants, CETPs, and Sector-Specific Schedules
Integrated steel plants sit under a dedicated CPCB schedule with limits tighter than the general standard for oil & grease (10 mg/L), phenol (1 mg/L), cyanide (0.2 mg/L), and ammonia (50 mg/L), plus flow-normalised load caps at kg/tonne of finished steel. Most modern Indian steelworks pair a physico-chemical primary stage (lime softening, DAF) with a two-stage biological train and reuse treated water in coke quenching and slag cooling. Buyers comparing CPCB wastewater discharge standards for Indian steel plants should pull both the general effluent schedule and the sector-specific notification before locking in equipment sizes.
What Are CETP Discharge Standards in India?
Common Effluent Treatment Plants (CETPs) handling combined member effluent face an additional layer: the CETP outlet must meet CPCB norms while individual member discharges meet the inlet consent given to the CETP operator. Sizing the biological stage for a CETP typically assumes a 1.4–1.6× peaking factor over the daily average flow.
What Are STP and ETP Effluent Standards?
STP and ETP effluent standards in India both draw from Schedule VI, but the binding consent differs by discharge point and sector schedule. An industrial ETP discharging to inland surface water must hit BOD 30 mg/L and COD 250 mg/L; a municipal STP or sewer-connected plant may work to the public-sewer column (BOD 350 mg/L, TSS 600 mg/L) where the downstream STP provides secondary treatment.
Future Outlook: Stricter Enforcement, ZLD, and Digital Monitoring
Four forces are reshaping compliance economics across Indian industry in 2026 and beyond.
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Stricter Enforcement:
CPCB and SPCBs have raised inspection frequency, and the National Green Tribunal (NGT) has levied recurring fines on repeated violators. Plants without real-time effluent data are the first to be shut down.
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Water Reuse and Zero Liquid Discharge (ZLD):
Distilleries, dyes, and pharma units in water-stressed states are moving to ZLD using MBR followed by RO and brine recovery. A typical ZLD retrofit adds 35–60% to ETP capex but removes freshwater risk and most compliance exposure.
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Digital Monitoring:
IoT effluent sensors feeding a cloud dashboard are now standard in consent applications for plants above 100 m³/d. Predictive analytics on aeration blower load and polymer dosing typically trim chemical OPEX by 10–15%.
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Sustainable Practices:
Anaerobic digestion with biogas capture turns a sludge liability into a steam offset, paying back in 3–5 years at sites above 500 m³/d.
For the broader framework, see our industrial water management guide and the water reuse playbook. For a comparison with another emerging-market regime, see South Africa's 2025 industrial discharge limits.
Who This Guide Is For and Next Step
This page is for plant engineers, EPC contractors, and procurement managers designing or auditing an ETP, STP, or CETP for an Indian facility. It is less useful for municipal-only STP operations without industrial loads, where the CPCB Schedule VI for sewage typically applies.
Selection checklist before you commit to a treatment train:
- Confirmed discharge scenario (inland water, sewer, irrigation, marine).
- Latest SPCB consent letter with parameter-wise limits.
- One-week minimum characterisation of influent BOD, COD, TSS, NH₃-N, oil & grease.
- Defined reuse target (cooling, boiler, gardening) if ZLD is on the roadmap.
- Online instrumentation list and data retention policy for SPCB reporting.
- Sludge disposal route and TS% target from the dewatering device.
Send your influent profile and consent conditions to our process team for a sized ETP proposal and a comparative quote on MBR, DAF, and filter press packages.
Frequently Asked Questions
What is the BOD limit for wastewater discharge in India?
The CPCB BOD limit for discharge to inland surface water is 30 mg/L max, 100 mg/L for land irrigation, and 350 mg/L max for discharge to a public sewer. Marine coastal areas allow 100 mg/L max. Most inland-discharge plants we see run between 18–25 mg/L at the outlet to absorb sampling variability.
What are the CPCB standards for industrial effluent discharge to inland surface water?
The binding numbers for inland surface water are BOD 30 mg/L, COD 250 mg/L, TSS 100 mg/L (process wastewater), pH 5.5–9.0, oil & grease 10 mg/L, ammoniacal N 50 mg/L, TKN 100 mg/L, and total residual chlorine 1.0 mg/L. Industry-specific schedules add tighter limits on top.
Do wastewater discharge standards differ between public sewers and rivers in India?
Yes. TSS is 600 mg/L for public sewers versus 100 mg/L for inland surface water, and BOD is 350 mg/L for sewers versus 30 mg/L for rivers. Sewer discharge assumes downstream biological treatment at the municipal STP; river discharge does not.
How often does CPCB update its wastewater discharge standards?
The general effluent schedule was last substantively revised in 1993 and remains in force under the 1986 Environment (Protection) Rules. Sector-specific notifications and SPCB consents are updated more frequently, so always confirm the latest version before design.
Which Act governs wastewater discharge standards in India?
The Environment (Protection) Rules, 1986, made under the Environment (Protection) Act, 1986, carry the Schedule VI effluent limits. The Water (Prevention and Control of Pollution) Act, 1974 underpins the CPCB and SPCBs that enforce those limits.
Further Reading
Explore these in-depth articles on related wastewater treatment topics:
