Effluent Treatment Plant (ETP)

An Effluent Treatment Plant (ETP) is a multi-stage facility that treats industrial wastewater by physical, chemical, and biological processes before discharge to drains, water bodies, or recycle systems. Indian industrial law (Water Act 1974, EP Rules 1986) mandates ETPs for any industrial activity generating wastewater above scheduled thresholds, with detailed design and performance specifications submitted in every SPCB CTE and CTO application. For CBG, recycling, and pyrolysis projects, ETP design is non-negotiable and typically accounts for 8–18% of total project capex.

A standard Indian industrial ETP comprises seven stages. Preliminary treatment (screens, grit chambers, oil-water separation) removes large solids and floatables. Primary treatment (equalisation tank, neutralisation, primary clarifier) balances flow and pH. Secondary biological treatment — activated sludge process, MBBR, or SBR — degrades organic load (BOD reduction of 85–95%). Tertiary treatment (filtration, ultrafiltration, RO) polishes the effluent for reuse or strict-norm discharge. Sludge handling (thickening, digestion, dewatering) processes the bio-solids. Disinfection (chlorination, UV) removes residual pathogens. Monitoring instruments (online COD, pH, TSS) and effluent flow meters complete the package.

Design specifications follow CPCB norms. Common discharge limits: BOD 30 mg/L, COD 250 mg/L, TSS 100 mg/L, pH 6.5–8.5, oil and grease 10 mg/L. Sector-specific norms apply to recyclers, pyrolysis units, and electroplating-adjacent operations. Capex scales roughly ₹3–8 crore per MLD treatment capacity, with smaller plants (under 50 KLD) at ₹40–120 lakh. O&M cost is ₹15–50 per cubic metre treated, dominated by power (50–60%), chemicals (20–30%), and sludge disposal (10–15%). For CBG plants, ETP is often integrated with the digestate handling line, treating wash-down water and the high-COD liquid fraction from dewatering. For pyrolysis plants, ETP capacity must absorb condenser blowdown and quench water with high TDS and trace hydrocarbon contamination.

• Multi-stage facility treating industrial wastewater before discharge or reuse.
• Mandatory under Water Act 1974 and EP Rules 1986 for any wastewater-generating industry.
• Seven stages: preliminary, primary, biological, tertiary, sludge, disinfection, monitoring.
• Capex 8–18% of total project; O&M ₹15–50/m³ treated. Performance specs anchored in CPCB norms.