What Are STP and ETP Effluent Standards in India?
STP and ETP effluent standards in India set inland BOD ≤ 30 mg/L, COD ≤ 250 mg/L, and TSS ≤ 100 mg/L under Schedule VI. pH is 6.5–8.5 and oil & grease ≤ 10 mg/L. Reuse STP bars use BOD ≤ 10 mg/L, TSS ≤ 10 mg/L, COD ≤ 50 mg/L, and fecal coliform ≤ 100 MPN/100 mL.
Three legal instruments govern every cubic metre a plant releases in 2026. First, the MoEFCC Environment (Protection) Rules, 1986 — Schedules I and VI — set general and sector-specific effluent standards originally notified under G.S.R. 422(E) of 19 May 1993 and amended through 2024. Second, CPCB online continuous effluent monitoring directions require real-time data push to the CPCB/SPCB server, including uptime. Third, sector-specific ZLD directions — distillery (2004), textile (2024 draft), and select pharma — override general Schedule VI limits with a zero-discharge obligation.
Where you discharge determines which Schedule column applies. Effluent to inland surface water sits under Schedule VI Part A. Discharge to public sewers uses a separate Part A column. Marine and coastal outfalls follow Schedule VI Part B. Land for irrigation must meet Schedule VI plus soil-crop loading norms in the SPCB consent. Treating these four routes as interchangeable is the most common compliance error in Indian plant audits.
What Are CPCB Effluent Discharge Standards?
CPCB effluent discharge standards map each regulated parameter to a receiving-water or reuse objective — the number on the page is an engineering result, not an arbitrary cap. The table below consolidates values most often cited by SPCB consent officers in 2026; verify against the live CPCB tables at cpcb.gov.in before any consent application.
| Parameter | Inland Surface Water | Public Sewers | Marine / Coastal | Land for Irrigation | STP Reuse |
|---|---|---|---|---|---|
| pH | 6.5–8.5 | 6.5–8.5 | 6.5–8.5 | 6.5–8.5 | 6.5–8.5 |
| BOD (3-day, 27 °C) | 30 mg/L | 100 mg/L | 100 mg/L | 100 mg/L | 10 mg/L |
| COD | 250 mg/L | — | 250 mg/L | — | 50 mg/L |
| TSS | 100 mg/L | 200 mg/L | 100 mg/L (offshore) | 200 mg/L | 10 mg/L |
| Total Dissolved Solids | 2100 mg/L | — | — | — | 500–1000 mg/L (state-specific) |
| Oil & Grease | 10 mg/L | 20 mg/L | 20 mg/L | 10 mg/L | — |
| Chloride (as Cl⁻) | 1000 mg/L | — | — | 600 mg/L | 200–250 mg/L |
| Sulphate (as SO₄) | 1000 mg/L | — | — | 1000 mg/L | — |
| Total Nitrogen | 100 mg/L | — | 100 mg/L | — | — |
| Ammoniacal Nitrogen | 50 mg/L | 50 mg/L | 50 mg/L | — | — |
| Total Phosphorus | 5 mg/L | — | — | — | — |
| Fecal Coliform | — | — | — | — | ≤ 100 MPN/100 mL (none detectable in 10 mL for drinking reuse) |
| Total Residual Chlorine | 1.0 mg/L | — | 1.0 mg/L | — | — |
Earlier plant checklists often listed public-sewer BOD at 100 mg/L and TSS at 200 mg/L. Schedule VI sets public-sewer BOD at 350 mg/L and TSS at 600 mg/L, with sewer pH 5.5–9.0 (Schedule VI general standards). CETP inlet consents frequently overwrite those Schedule VI sewer columns with much tighter BOD, TDS, and colour caps — always design to the signed consent, not the national floor alone.
Three engineering points sit behind these columns. The BOD ≤ 30 mg/L inland-surface-water cap exists to keep dissolved oxygen above 4 mg/L in the receiving stream. Conventional secondary biology routinely reaches 20–25 mg/L. The 30 mg/L ceiling protects the river during low-flow summer months. The 10 mg/L reuse cap on BOD and TSS is operational proof that cooling towers or horticulture systems will not foul. CPCB also applies that bar to STPs claiming treated wastewater reuse under Namami Gange. The 1.0 mg/L total residual chlorine ceiling prevents trihalomethane formation in the receiving water — going higher does not buy more disinfection credit, it only raises downstream toxicity.
For pesticide and pharma streams, the bioassay / 96-hr LC₅₀ fish-toxicity pass is a separate consent condition; failing the bioassay is, in practice, a non-discharge event regardless of whether BOD and COD are within limits. For a deeper dive on biological removal, see the BOD removal engineering guide and these pollution control rules regarding bod and cod.
Which Schedule Applies to Your Industry
Every industry is named somewhere in the Schedules, but most engineers read the wrong column first. The table below maps the principal sectors to the operative Schedule and the headline non-standard parameter that triggers their sectoral cap.
| Industry Sector | Governing Schedule / Direction | Headline Sectoral Limit (beyond general) |
|---|---|---|
| Distillery (molasses / grain) | ZLD direction, 2004 (reaffirmed 2024 draft) | Zero liquid discharge — no surface-water discharge permitted |
| Tannery | Schedule VI sectoral | Total Chromium ≤ 2 mg/L, Sulphide ≤ 1 mg/L, TDS stricter in TN/Karnataka cluster consents |
| Textile (dyeing & printing) | Schedule VI + 2024 draft ZLD clusters | TDS ≤ 2100 mg/L; Tirupur / Erode CETP inlet norms typically stricter |
| Pulp & Paper | Schedule VI sectoral | AOX, colour, lignin-specific limits; ZLD for new capacities under CPCB 2024 draft |
| Sugar | Schedule VI sectoral | BOD ≤ 30 mg/L; condensate recycling expected |
| Pharma (formulation / API) | Schedule VI + 2024 draft ZLD list | Specific COD / product-API residual limits; bioassay 96-hr LC₅₀ pass mandatory |
| Pesticide / Insecticide | Schedule VI sectoral | Bioassay mandatory; no discharge consent without pass |
| Electroplating | Schedule VI sectoral | Heavy metals per metal: Ni, Cr(VI), Cu, Zn each capped at 2–3 mg/L; CN⁻ ≤ 0.2 mg/L |
| Dairy / Food Processing | Schedule VI general | Pre-sewer BOD often ≤ 100 mg/L in state consent; oil & grease ≤ 10 mg/L |
| Iron & Steel | Schedule VI sectoral | Oil & grease ≤ 10 mg/L, phenols ≤ 1 mg/L, cyanide ≤ 0.2 mg/L |
| Refinery / Petrochemical | Schedule VI sectoral | Oil & grease ≤ 5 mg/L (tighter), sulphide, phenols |
| Thermal Power | Schedule VI sectoral | TDS, free chlorine, temperature Δ ≤ 5 °C at point of mixing |
| Hotels / Hospitals | Schedule VI general (treated as municipal) | Fecal coliform ≤ 100 MPN/100 mL if reuse claimed |
Two operational caveats matter in the field. SPCBs routinely impose limits stricter than CPCB Schedule VI on a case-by-case consent basis — Maharashtra MPCB, Tamil Nadu TNPCB, and Gujarat GPCB are noticeably harder on CETP inlet norms than the Centre's general numbers. Always read your consent draft against your state's cluster-specific orders before signing. The 2024–2025 draft directions expand ZLD coverage to additional textile sub-categories and to new pharma capacities — a plant that is not ZLD today may be told to become one at the next CTE renewal.
Steel and metallurgical units should also cross-check the new norms of water as per cpcb for steel plants in india against their sectoral schedule before sizing oil traps and cyanide treatment. Broader state STP overlays are summarized in this wastewater treatment regulations India guide.
What Are CPCB Cd and Ni Limits?
CPCB cadmium and nickel limits under Schedule VI for inland surface water are Cd ≤ 2.0 mg/L and Ni ≤ 3.0 mg/L. Electroplating sectoral lists commonly keep nickel at 2–3 mg/L per metal. Hexavalent chromium is far tighter at ≤ 0.1 mg/L inland, while total chromium sits at ≤ 2.0 mg/L. A plating shop that only tracks total chromium can still fail Cr(VI).
Most plants we size for electroplating and surface finishing run metals polishing at the lower end of the consent band, not at the numeric ceiling. Cyanide must stay ≤ 0.2 mg/L inland; that limit, not BOD, usually drives the chemical destruction step. If your CTO lists metal caps below Schedule VI, the CTO wins — dilution to meet metals is prohibited.
Engineering the Treatment Train to Meet CPCB Limits
Each limit in the table is a design specification for a specific unit operation. A workable train for a 200–1000 KLD Indian industrial plant in 2026, in line with Schedule VI and OCEMS, runs:
- Front-end screening & equalisation. A rotary mechanical bar screen with 6–10 mm aperture protects downstream pumps. A flow-equalisation tank at 8–12 hours HRT damps shock loads so biology never sees a slug above 30 mg/L BOD. A DAF pre-treatment unit is the gatekeeper for oil & grease ≤ 10 mg/L. Without it, free oil emulsifies through biology and pins discharge above the inland 10 mg/L oil and grease cap.
- Primary biological stage (BOD 250–500 mg/L raw → 30 mg/L). Conventional activated sludge (F/M 0.2–0.4, HRT 6–8 hr) covers general industry. Moving-bed biofilm reactor (MBBR) handles high-strength, variable textile and pharma loads with 30–40% less footprint. Upflow anaerobic sludge blanket (UASB) reactor is the right call for distillery and sugar — organic loading 8–12 kg COD/m³·day with biogas recovery offsets operating cost and is the foundation of the mandated ZLD economics.
- Polishing (BOD 30 mg/L → reuse 10 mg/L). A submerged flat-sheet MBR membrane bioreactor system with PVDF DF-series membranes at 0.1–0.4 µm eliminates the secondary clarifier. It reliably delivers TSS ≤ 10 mg/L, with verified discharge of 2–5 mg/L TSS at 0.3 µm (HydropureWater field data, 2026). The MBR also gives a 0.5–1 log BOD margin over a well-run CAS, which is the safety cushion for consent renewal.
- Tertiary (COD 50 mg/L → reuse, or TDS cut). Multi-media filtration (sand + anthracite + garnet) ahead of RO protects the membranes from fouling; RO brings TDS from 1500–2500 mg/L down to the 200–500 mg/L typically required for reuse. For discharge-only paths, this stage is sometimes replaced with pressure sand filtration alone.
- Disinfection. A ClO₂ disinfection generator dosing 1.5–2 mg/L ClO₂ with 30 minutes contact hits fecal coliform ≤ 100 MPN/100 mL. It keeps TRC ≤ 1.0 mg/L at the outlet; sodium hypochlorite tends to overshoot TRC under variable load.
- Sludge line. A plate-and-frame filter press brings the biological and DAF sludge to 25–35% dry solids for TSDF disposal, cutting sludge volume by 80–85% versus drying beds.
The full flow: Raw → Bar Screen → Equalisation → DAF → Biological (MBBR / UASB + MBR) → Polishing Filtration → RO (if reuse) → ClO₂ → Reuse / Discharge; sludge to filter press. Compare oil and grease handling against international practice in this oil & grease discharge limit 2026 comparison, and against regional TDS / phenol caps via this regional discharge limit benchmark.
OCEMS, Consent, and Enforcement Under CPCB Directions
The compliance bar in 2026 is not just what you discharge — it is also what you continuously prove you discharge. Under CPCB OCEMS directions, industries drawing ≥ 100 KLD of water or discharging ≥ 50 KLD of effluent must install continuous online analysers for pH, TSS, COD, BOD, and flow. Data must push every 15 minutes to the CPCB/SPCB server with ≥ 95% availability, 24×7, for 365 days. Non-availability is treated as non-compliance.
According to CPCB's OCEMS information portal (2025–2026 updates), industries are migrating to the new portal at cems.cpcb.gov.in. SPCB onboarding directions run through March 2026, and revised calibration and alert protocols were published in July 2025. Treat portal connectivity failures the same way you treat analyser downtime — both register as compliance gaps.
Consent to Establish (CTE) is the pre-construction approval; Consent to Operate (CTO) is the operational green light, typically valid for 5 years subject to annual compliance returns. Cluster-area plants — Tirupur, Erode, Kanpur, Surat, Pali, Vatva — face longer CTE and CTO timelines because the SPCB applies additional CETP-inlet and cluster-load scrutiny. The penalty regime under Water Act Sections 15–16 runs up to 6 years imprisonment and/or a fine of ₹1 lakh per day continuing. The 2024 CPCB Environmental Compensation direction adds a composite formula, typically 1.5× to 5× avoided pollution-control cost, recoverable through the District Collector. SPCB special drives against non-complying CETPs in 2024–2025 have resulted in closure notices; the trajectory is enforcement, not relaxation.
Who This Is For and Next Step
This guide is for plant engineers, EPC contractors, and procurement managers sizing or renewing an STP/ETP under Indian consent conditions. Look elsewhere if you need only municipal drinking-water standards or non-Indian discharge codes. Selection checklist before you freeze the P&ID:
- Confirm discharge mode (inland / sewer / marine / land) in the draft CTO.
- Pull the sectoral Schedule or ZLD direction, not only Schedule VI general.
- Match BOD/COD/TSS and oil & grease to unit operations with stated HRT and F/M.
- Budget OCEMS analysers, 15-minute data push, and ≥ 95% uptime.
- Check CETP inlet norms if you are a member unit — they often beat Schedule VI.
- Verify Cd, Ni, Cr(VI), and cyanide caps for metal-bearing streams.
- Document sludge path to a licensed TSDF at 25–35% dry solids.
If you need a train sized to your consent limits and OCEMS package, request a technical quote with your influent data and CTO draft.
Frequently Asked Questions
What are the general CPCB effluent limits for inland surface water?
BOD 30 mg/L, COD 250 mg/L, TSS 100 mg/L, pH 6.5–8.5, oil & grease 10 mg/L, and total residual chlorine 1.0 mg/L apply for inland surface water. Those values come from Schedule VI of the EPA Rules 1986 (G.S.R. 422(E), as amended through 2024). Your SPCB CTO may set stricter values; design to the tighter number.
Does every industry need ZLD under CPCB norms 2026?
No. Mandated ZLD categories remain distillery under the 2004 direction, and CPCB 2024 draft text extends ZLD pressure to additional textile sub-sectors and new pharma capacities. Most general industries still meet Schedule VI limits with conventional biological treatment plus polishing where reuse is claimed.
What is the OCEMS monitoring uptime requirement?
≥ 95% data availability, a 15-minute push interval, and 24×7 operation are required, with pH, TSS, COD, BOD, and flow as the minimum parameter set under CPCB OCEMS directions. CPCB's 2025–2026 portal migration and July 2025 calibration/alert protocols make sustained connectivity part of the same compliance bar.
How long does it take to get CTO from an SPCB?
Typically 60–120 days if CTE, consent conditions, and OCEMS connectivity are clear before filing. Cluster-area scrutiny in Tirupur, Kanpur, Surat, and Pali can extend this to 4–8 months because CETP inlet load and cumulative cluster discharge are reviewed together with the unit consent package.
Can I discharge to a CETP and bypass Schedule VI limits?
No. CETPs have their own SPCB-issued inlet norms, frequently stricter than Schedule VI — especially BOD, TDS, and colour for textile and tannery clusters — and the CETP operator enforces them at the inlet. Member units remain liable for inlet exceedances even when the CETP outlet meets its own consent.
