effluent (effluent)
Also known as: industrial effluent · trade effluent · wastewater discharge · liquid waste
Liquid waste or wastewater discharged as a by-product of industrial processes, containing dissolved chemicals, suspended solids, or biological matter. Must be treated to meet SPCB discharge standards before release to water bodies or municipal sewers.
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What is effluent?
Effluent is any liquid waste or wastewater discharged from an industrial process — containing dissolved chemicals, suspended solids, organic matter, heavy metals, salts, or biological contaminants — that must be treated before release to the environment. The term is the regulatory anchor of India's water pollution control framework: the Water (Prevention and Control of Pollution) Act, 1974 was enacted specifically to control industrial effluent discharge, and every CTE/CTO consent issued by an SPCB specifies effluent generation rate (KLD), treatment system design, and outlet quality standards.
Effluents from recycling and CBG operations fall into several types:
- Process effluent — water-jet washing of plastic flakes (50–100 L/kg input, high organic load), digestate liquor from CBG (high COD, BOD, ammonia), tyre wash water (oily, suspended solids)
- Cooling and utility effluent — boiler blowdown, cooling tower bleed, RO reject; high TDS but otherwise relatively clean
- Spillage and washdown — floor wash, equipment cleaning; sporadic, variable composition
- Sanitary effluent — toilets, kitchen, canteen; standard sewage treatable in STP
CPCB discharge standards for industrial effluent to inland surface water (General Standards under EPR 1986 Schedule VI):
- pH — 5.5–9.0
- BOD₅ — 30 mg/L
- COD — 250 mg/L
- TSS — 100 mg/L
- Oil and grease — 10 mg/L
- Ammoniacal nitrogen — 50 mg/L
- Total dissolved solids — 2,100 mg/L (above this, ZLD typically required)
Treatment train selection depends on effluent characteristics. Low-COD streams (under 500 mg/L) can be treated by simple ASP or MBBR; high-COD/high-BOD streams (above 2,000 mg/L) typically need anaerobic pre-treatment followed by aerobic polishing; high-TDS streams need RO with brine evaporation. ETP capex for an Indian recycling plant ranges from ₹15 lakh for a basic 5 KLD system to ₹3–5 crore for a full ZLD train handling 100 KLD. The ETP is a mandatory deliverable in every SPCB CTE application and its underperformance is the single most common reason for CTO non-renewal.
Common questions about effluent
Plain-English answers to what people most often ask.
What is industrial effluent?
What effluent treatment is required for recycling plants in India?
What happens if a plant discharges untreated effluent?
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