CPCB General Effluent Discharge Standards — Schedule VI of EPA 1986 Explained

Every industrial unit that discharges treated effluent in India must comply with a discharge standard. Where CPCB has not issued an industry-specific standard, Schedule VI of the Environment (Protection) Rules 1986 provides the applicable limits. This article explains what Schedule VI covers, what the actual numeric limits are across all four discharge scenarios, and how to apply them correctly.

Schedule VI limits are the national floor — your SPCB Consent to Operate (CTO) conditions may be stricter. Always treat your CTO as the binding document, with Schedule VI as the minimum baseline.

About This CPCB Standard

The Environment (Protection) Act 1986 (EPA 1986) empowers the Central Government and CPCB to set standards for discharge of environmental pollutants. These standards are notified through the Environment (Protection) Rules 1986. Schedule VI of those Rules contains the general standards — the default limits that apply when no sector-specific standard has been issued.

CPCB has also notified industry-specific standards for approximately 30 categories of industries — tanneries, distilleries, sugar mills, textile processing units, thermal power plants, and others. These are listed separately in the Rules. For industries not in that list, and for parameters not specified even in industry-specific standards, Schedule VI is the governing document.

The schedule covers four discharge scenarios: inland surface water, public sewers (municipal drains or CETPs), land disposal for irrigation, and marine coastal areas. Each scenario has its own set of limits reflecting the receiving environment's treatment capacity and sensitivity.

What is Schedule VI and When Does It Apply

Schedule VI is best understood as the "default standard" in India's effluent discharge framework. It operates as follows:

• No industry-specific standard exists — Schedule VI applies in full to all parameters and all discharge scenarios. This covers food processing (except specific sub-categories), hotels, hospitals, commercial establishments, educational institutions, and most service-sector industries.
• Industry-specific standard exists but is silent on a parameter — For any parameter not specified in the industry-specific standard, Schedule VI fills the gap automatically. For example, if the standard for a specific industry specifies BOD, COD, and TSS but not fluoride, the fluoride limit from Schedule VI (15 mg/L for inland surface water) applies.
• Both a specific and a general standard apply — Where two standards address the same parameter, the more stringent limit governs. You cannot claim the more relaxed limit simply because it appears in one of the two applicable standards.
• SPCB conditions in the CTO — State Pollution Control Boards may set conditions stricter than Schedule VI in your Consent to Operate. The CTO conditions override Schedule VI where they are more stringent.

Industries that most commonly operate entirely under Schedule VI include: hotels and resorts, hospitals and healthcare facilities, food manufacturing plants not covered by a sector-specific standard, pharmaceutical formulation units (API manufacturing has its own standard), educational campuses, commercial complexes, and industrial estates without a CETP-specific notification.

Inland Surface Water Discharge Limits

Inland surface water includes rivers, streams, lakes, ponds, canals, and backwaters. This is the most stringent discharge scenario because the receiving water body is directly used for human and ecological purposes. The limits below are from Schedule VI.

A few practical notes on reading this table. The BOD measurement standard in India is 3 days at 27°C — different from the European 5-day BOD (BOD₅ at 20°C) standard. Ensure your laboratory is reporting using the Indian standard when checking compliance. The COD limit of 250 mg/L is a general limit; for a high-strength effluent (food processing, dairy), achieving this at the ETP outlet typically requires a biological treatment stage followed by tertiary polishing. The heavy metal limits listed above are for the general standard — electroplating, surface finishing, and battery industries have dedicated standards with typically stricter limits for their relevant metals.

Discharge to Public Sewers (Municipal Sewer/CETP)

When an industry discharges to a municipal sewer (which leads to a Sewage Treatment Plant) or to a Common Effluent Treatment Plant (CETP), the limits are relaxed compared to direct surface water discharge. This is because the downstream treatment facility provides an additional treatment step before the effluent reaches a water body.

The relaxation in BOD, COD, and SS limits for sewer discharge reflects the treatment capacity of the downstream STP or CETP. However, two important caveats apply. First, the CETP or municipal authority's own Consent to Operate will specify inlet quality requirements — these are the operational limits for member industries and may be stricter than Schedule VI for that category. Always confirm the CETP inlet standards before designing your pre-treatment. Second, heavy metal limits are not relaxed for sewer discharge. This is because most municipal STPs do not have metal removal capability, and heavy metals pass through to the final discharge point and into the receiving water body.

For industries discharging to a CETP, the CETP CTO conditions govern inlet quality. The CETP operator is legally responsible for the quality of the combined effluent leaving the CETP — and they will enforce inlet standards on member industries accordingly.

Land Disposal / Irrigation Limits

Some industries with suitable land holdings discharge treated effluent for land disposal or irrigation purposes. Schedule VI specifies separate limits for this scenario. These limits are designed to protect soil quality, groundwater, and crop health.

Land disposal is permitted only for actual irrigation of land — not as a route to percolate effluent to groundwater. The Sodium Absorption Ratio (SAR) limit of ≤26 and the sodium limit of ≤60 mg/L are critical for protecting soil structure: high-sodium effluent causes clay dispersion, reducing soil permeability over time. The boron limit of ≤2 mg/L protects sensitive crops — boron toxicity is a risk in cooling tower blowdown and some process effluents.

The area of land required for effluent disposal must be calculated based on both hydraulic loading (how much effluent volume per hectare per day the soil can absorb without waterlogging or runoff) and nutrient loading (nitrogen and phosphorus in the effluent versus what the crop can take up). Both calculations should be documented in the EMP submitted with the SPCB consent application for land disposal.

Marine Coastal Areas Discharge Limits

Coastal industries — ports, refineries, petrochemical complexes, fish processing plants, desalination plants, and coastal power stations — that discharge through a marine outfall to coastal waters are subject to separate limits under Schedule VI.

The marine coastal limits sit between the stringent inland surface water limits and the relaxed sewer discharge limits. The wider pH range (5.5–9.0) and relaxed Oil & Grease limit (20 mg/L) reflect the higher dilution capacity of coastal waters, but the BOD limit of 100 mg/L is actually more relaxed than the 30 mg/L required for inland discharge, recognising the natural BOD removal in marine environments. Coastal dischargers are also subject to Coastal Regulation Zone (CRZ) notifications, which may impose additional conditions on outfall location, mixing zone, and monitoring requirements beyond Schedule VI parameter limits.

How to Read and Apply These Standards

Several practical issues arise when industries try to apply Schedule VI limits. Understanding these correctly avoids both non-compliance and over-design.

Daily maximum vs. monthly average. Schedule VI limits are stated as concentrations that must be met at the point of discharge. Unless your CTO conditions explicitly specify monthly average limits, the limits are treated as daily maximum concentrations — meaning every sample taken at the final discharge point must comply. Some SPCBs specify both a daily maximum and a monthly average in the CTO; in that case, both apply independently.

Dilution is prohibited. You cannot add clean water, cooling water, or utility water to your effluent stream to reduce concentration and achieve compliance. The standard must be met through treatment. Adding dilution water is an explicit violation and is treated identically to exceeding the limit.

Compliance point is the final discharge. Limits apply at the point where the treated effluent leaves the plant boundary and enters the receiving environment — the ETP outlet, the connection point to the sewer, or the marine outfall. Internal process streams or intermediate ETP stages are not required to meet these limits individually.

SPCB CTO conditions may be stricter. Your Consent to Operate issued by the State Pollution Control Board is the legally binding compliance document. The SPCB can, and often does, specify limits stricter than Schedule VI — for example, a lower BOD limit for discharge to a protected river segment, or a lower TSS limit in a water-stressed state. Treat your CTO conditions as the design standard for your ETP, not Schedule VI.

When two standards apply, the more stringent prevails. If both a Schedule VI general limit and an industry-specific limit exist for the same parameter, always apply the more stringent (lower/narrower) limit. There is no averaging or choosing between them.

Online Continuous Effluent Monitoring Systems (OCEMS). CPCB has mandated OCEMS installation for large industries (17 categories of heavily polluting industries and units with discharge above a threshold flow). OCEMS data is transmitted in real time to SPCB and CPCB servers. This means non-compliance is now detected automatically and continuously, not only during periodic inspections.

Penalties for Exceeding Standards

The Environment Protection Act 1986 establishes a tiered enforcement framework with significant penalties for discharge standard violations.

Criminal penalties under EP Act Section 15. Violation of any discharge standard notified under the EP Act carries a penalty of up to 5 years imprisonment and/or a fine of up to ₹1 lakh for the first offence. If the violation continues after conviction, an additional fine of ₹5,000 per day applies for every day the violation persists. Directors, managers, and officers of companies are individually liable in addition to the company itself where the offence was committed with their consent or negligence.

SPCB closure and restraint powers. Under Section 33A of the Water (Prevention and Control of Pollution) Act 1974, the SPCB can issue a show-cause notice to a defaulting industry and, after giving an opportunity to respond, direct the closure of the unit or restraint of electricity and water supply. Closure directions can be issued without court intervention — making this the most immediately impactful enforcement tool. Closure orders are immediately effective and require compliance to be demonstrated before the SPCB will consider revocation.

National Green Tribunal (NGT) environmental compensation. The NGT can award environmental compensation for damage caused by effluent discharge standard violations. Compensation awards are assessed based on the nature and extent of environmental harm, the volume and toxicity of the discharge, and the period of non-compliance. NGT compensation orders are separate from criminal penalties and civil liability — all three can apply simultaneously for the same violation.

Consent to Operate suspension and cancellation. Beyond closure directions, the SPCB can suspend or cancel a Consent to Operate for recurring or serious violations. Operating without a valid CTO is itself a separate offence under the Water Act and Air Act, compounding the liability.

For industries with OCEMS installations, data showing continuous exceedance is automatically flagged and can trigger enforcement action without a physical inspection visit. The standard regulatory process — show-cause notice, reply period, closure direction — can be initiated based on OCEMS data alone.