CPCB Source Document
Schedule VI, Environment (Protection) Rules 1986 — General Effluent Standards; CPCB COINDS for Petrochemical Industry; MoEFCC EIA Notification for Chemical/Petrochemical Projects
Authority: CPCB under Environment (Protection) Act 1986 · Applicable to integrated petrochemical complexes, aromatic and olefin plants, polymer manufacturers
View effluent standards on cpcb.nic.in ↗CPCB website links may change — search "petrochemical effluent standards" on cpcb.nic.in if the link is broken.
Petrochemical Industry Sub-Sectors and Effluent Sources
India's petrochemical industry encompasses large integrated complexes and downstream processing units. Major sub-sectors with distinct effluent profiles:
- Olefin plants (crackers): Steam cracking of naphtha, ethane, or LPG to produce ethylene and propylene. Generates quench water, process condensate, and caustic tower effluent — high in phenol, sulphides, and hydrocarbons.
- Aromatic complexes: Catalytic reforming and extraction of benzene, toluene, and xylene (BTX). Generates solvent extraction raffinate, wash water, and column condensate with high BTEX content.
- Polymer plants (PE, PP, PVC, PS): Polymerisation of monomers. Generates catalyst wash water, slurry filtrate, and equipment cleaning effluent — lower BOD but contains polymer additives (stabilisers, antioxidants).
- Downstream chemical plants: Ethylene glycol, ethylene oxide, propylene oxide, acrylic acid — generate highly oxygenated, high-BOD process wash water and condenser effluent.
CPCB Pollution Category
All integrated petrochemical complexes are Red category under CPCB — they consume large volumes of water for process cooling, steam generation, and product washing, and discharge complex mixed effluent containing hydrocarbons, phenolics, sulphides, and priority pollutants. They are also typically included in the 17 Grossly Polluting Industries list requiring real-time OCEMS data transmission to CPCB servers.
Key Wastewater Streams and Characteristics
Major wastewater streams from a typical integrated petrochemical complex:
- Process condensate: Steam condensate from process heaters and columns — contains dissolved hydrocarbons, phenol (50–500 mg/L), ammonia, and H₂S. Highest-priority stream for treatment.
- Quench water (steam crackers): Water used to quench cracked gas — contains heavy aromatics, pyrolysis oils, and suspended coke particles. BOD 2,000–8,000 mg/L.
- Cooling tower blowdown: High TDS, biocide-treated water — must be treated separately for TDS and inhibitor removal before discharge.
- Amine unit wash water: From H₂S and CO₂ removal systems — contains degraded amines, heat stable amine salts, and sulphides.
- Equipment washings and floor drainage: Oil-contaminated wash water from maintenance and product spills — collected in oil interceptors before ETP.
CPCB Discharge Standards
| 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 |
| Phenol | ≤ 1 mg/L | ≤ 5 mg/L |
| Sulphide (as S) | ≤ 2 mg/L | ≤ 2 mg/L |
| Ammonia (as N) | ≤ 50 mg/L | ≤ 50 mg/L |
| Benzene | ≤ 0.01 mg/L (site-specific) | — |
Note: Benzene, toluene, ethylbenzene, xylene (BTEX) limits are typically set as site-specific consent conditions by SPCB for petrochemical plants — not in the general Schedule VI standards.
API Separator and Oil Removal
Oil removal is the first and most critical step in petrochemical ETP design:
- API (American Petroleum Institute) separator: Gravity-based free oil separation. Oil droplets > 150 microns (Stokes diameter) rise to the surface and are skimmed. Design surface overflow rate: 0.5–1.0 m³/m²·hour. Achieves free oil removal from 1,000–5,000 mg/L to < 50 mg/L. Mandatory for all oil-handling industrial ETPs under CPCB guidelines.
- DAF (Dissolved Air Flotation): Removes emulsified oil (droplets 10–150 microns) after API separator. Chemical coagulation with alum or polyaluminium chloride breaks the oil emulsion; microbubbles float the coagulated oil-floc to the surface. Achieves oil < 10 mg/L in DAF effluent.
- Oil skimming and recovery: API separator and DAF skimmings are recovered to slop oil tank for reprocessing or disposal as hazardous waste (Schedule I under HWM Rules 2016).
BTEX and Phenol Treatment
Phenol and BTEX are the most challenging pollutants in petrochemical wastewater:
- Sour water stripping: Process condensate containing H₂S and ammonia is first treated in a sour water stripper (steam stripping at 120–140°C) — removing H₂S and NH₃ before biological treatment. Stripped sour water enters the ETP at pH 7–8, sulphide < 5 mg/L, ammonia < 200 mg/L.
- Phenol steam stripping / extraction: For streams with phenol > 100 mg/L, steam stripping or solvent extraction (butyl acetate, diisopropyl ether) is used to recover phenol as a saleable byproduct. Stripping removes 95–99% of phenol; the stripped stream enters the ETP at < 20 mg/L for biological polishing.
- Biological phenol degradation: Acclimated activated sludge with phenol-adapted bacteria (Pseudomonas putida, Bacillus species) achieves phenol ≤ 1 mg/L from inlet concentrations of 20–50 mg/L with SRT > 15 days and HRT 12–24 hours.
- Air stripping for BTEX: Packed tower air strippers with air-to-water ratio 50–100:1 remove 90–99% of volatile BTEX. Off-gas is treated by thermal oxidation or carbon adsorption. Residual BTEX in the water phase is degraded in the biological treatment stage.
ETP Configuration for Petrochemical Plants
ETP configuration for an integrated petrochemical complex typically includes:
- Segregated collection system: process effluent, oily water, storm water, and sanitary sewage collected separately and treated appropriately before combining
- Sour water stripper → process condensate pre-treatment
- API separator → DAF → primary oil/suspended solids removal
- Equalization tank (24–48 hours HRT) → load buffering
- Biological treatment (activated sludge with extended SRT, or MBBR) → BOD/COD removal, phenol degradation, nitrification
- Secondary clarifier → sludge separation
- Polishing (sand filter + activated carbon filter) → final COD and trace organics removal
- OCEMS at final discharge point for real-time monitoring
Compliance and Monitoring Requirements
Compliance requirements for Red category petrochemical plants:
- EIA and Environmental Clearance (EC) from MoEFCC before construction — EC conditions specify ETP design, wastewater limits, and monitoring requirements.
- Consent to Establish and Consent to Operate from State PCB — both required before construction and before commissioning.
- OCEMS with real-time data transmission to CPCB/SPCB server — mandatory for all 17 GPI category plants including major petrochemical complexes.
- Monthly NABL-accredited laboratory monitoring of all consent parameters including phenol, BTEX (where specified), and priority pollutants.
- Oily sludge from API separator and DAF classified as Hazardous Waste (Category 5.2 — oil-contaminated solid/liquid) under HWM Rules 2016 — requires authorised TSDF disposal or co-processing in cement kiln.
- Annual environment audit and environment statement under EP Rules 1993.
Need ETP Design for Petrochemical Plants?
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Frequently Asked Questions
What CPCB category are petrochemical plants in India?
All integrated petrochemical complexes (producing olefins, aromatics, polymers, or downstream derivatives) are Red category under CPCB's industry categorisation — due to high water consumption, complex mixed effluent streams, and hazardous chemical content. They require Consent to Establish, Consent to Operate, formal ETP with API separator and biological treatment, OCEMS at the final discharge point, and annual environment statements. Standalone polymer processing units (pelletising, compounding) that do not produce chemicals may be Orange category with lower effluent generation.
What are the key pollutants in petrochemical effluent?
Key pollutants in petrochemical effluent: (1) Oil and grease — from process condensate, cooling water contamination, and pump seal leaks; (2) Phenol and phenolic compounds — from catalytic cracking and aromatic processing; (3) BTEX (benzene, toluene, ethylbenzene, xylene) — volatile aromatics from process streams; (4) Sulphides — from hydrodesulphurisation units; (5) Ammonia — from nitrogen-containing feedstocks and amine scrubbers; (6) BOD/COD from oxygenated compounds, glycols, and polymer additives in wash water.
Is an API separator mandatory for petrochemical ETP?
Yes. CPCB consent conditions for petrochemical plants invariably require an API (American Petroleum Institute) gravity separator as the first treatment unit — to remove free (non-emulsified) oil from process wastewater before any downstream biological treatment. The API separator is designed for oil droplet size > 150 microns using Stokes' Law (surface overflow rate 0.5–1.0 m³/m²·hour). Downstream, a DAF unit handles emulsified oil (droplet size 10–150 microns) before the biological treatment stage.
What phenol limit applies to petrochemical effluent under CPCB?
CPCB prescribes phenol ≤ 1 mg/L for discharge to inland surface water from petrochemical plants. Raw process condensate and stripper effluent from cracking units can contain phenol at 50–500 mg/L — requiring steam stripping for phenol recovery (where concentration justifies recovery economics) followed by biological treatment using phenol-adapted biomass to achieve the ≤ 1 mg/L limit. Sour water strippers ahead of biological treatment also reduce hydrogen sulphide and ammonia that would inhibit the phenol-degrading bacteria.
How is BTEX removed from petrochemical wastewater?
BTEX removal from petrochemical wastewater uses a multi-stage approach: (1) Source control — minimise BTEX entry to wastewater through closed-loop process design and condensate recovery; (2) Steam stripping — for high-BTEX streams (> 100 mg/L), steam stripping removes 90–99% of BTEX before biological treatment; (3) Air stripping towers — for moderate BTEX concentrations (10–100 mg/L); (4) Biological treatment — acclimated biomass in activated sludge or biofilm reactors can degrade residual BTEX to < 1 mg/L each. BTEX-rich off-gas from strippers must be recovered or thermally oxidised — not vented to atmosphere as BTEX are priority air pollutants.
This article summarises CPCB norms for petrochemical industry effluent for informational purposes. Always verify current standards with your State Pollution Control Board and MoEFCC Environmental Clearance conditions.