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Effluent Treatment Plant (ETP)

Industrial wastewater treated to the limits in your consent to operate — or recycled back into the plant.

What an ETP is

An effluent treatment plant treats the wastewater an industry generates — process effluent, floor and equipment washings, CIP water, scrubber and utility blowdown — so that it can be legally discharged to a drain, a CETP or land, or reused inside the factory. In India the outlet limits come from the Environment (Protection) Rules and the unit's consent from the State Pollution Control Board: typically pH 5.5–9, BOD ≤ 30 mg/L, COD ≤ 250 mg/L, TSS ≤ 100 mg/L, oil & grease ≤ 10 mg/L, plus industry-specific parameters such as colour, phenol, ammonia, chromium or TDS.

No two effluents are alike, so an ETP is designed backwards from the inlet: flow and its daily variation, pH, BOD, COD, TSS, TDS, oil & grease, temperature, and the industry-specific pollutants. That characterisation decides which of the treatment stages below are needed and how large each one is.

Treatment stages — how the water is cleaned

Process flow — typical sequence
Preliminary01Equalisation02Neutralisation03Coagulation andflocculation04Primaryclarification orDAF05Anaerobictreatment06Aerobicbiologicaltreatment07Secondaryclarification08Tertiarypolishing09Advancedtreatment andZLD10Sludge handling11
  1. Preliminary: screening and oil removalBar screens catch rags and solids; an oil skimmer, tilted-plate interceptor or API separator removes free oil before it coats everything downstream.
  2. EqualisationBatch discharges and shift peaks are collected in an equalisation tank with mixing or coarse aeration, so the plant sees a steady flow and load.
  3. NeutralisationAcid or alkali dosing brings pH into the 6.5–8.5 window where chemical precipitation and biology both work.
  4. Coagulation and flocculationAlum, PAC or ferric chloride destabilises colloids; polymer bridges them into settleable floc. Lime precipitates metals and phosphate.
  5. Primary clarification or DAFA tube-settler clarifier lets floc settle; dissolved-air flotation lifts oily or light solids instead. Removes 60–90 % of TSS and much of the COD.
  6. Anaerobic treatment (high-COD streams)UASB or anaerobic reactors convert high organic load to biogas before aerobic treatment, cutting power and sludge.
  7. Aerobic biological treatmentMicro-organisms consume dissolved BOD and COD in an activated-sludge tank, MBBR, SAFF or MBR with fine-bubble aeration. This is the heart of the plant.
  8. Secondary clarificationSettles the biomass; part is returned to the reactor, the rest is wasted as sludge. MBR plants replace this with membranes.
  9. Tertiary polishingPressure sand filter and activated carbon filter remove residual solids, colour and odour; ultrafiltration where reuse is planned.
  10. Advanced treatment and ZLDReverse osmosis recovers water for reuse; the reject goes to a multiple-effect evaporator and crystalliser where zero liquid discharge is mandated.
  11. Sludge handlingThickening, then filter press, screw press or decanter; dewatered cake goes to authorised TSDF disposal.

Technologies we select from

Activated sludge (ASP)

Proven, flexible, low capital; needs space and attentive operation.

MBBR

Biofilm on plastic carriers — compact, robust to shock loads, easy to upgrade an existing tank.

SAFF

Submerged fixed-film media; simple and stable for medium loads.

MBR

Membrane bioreactor — smallest footprint and reuse-grade outlet; higher power and membrane cost.

UASB / anaerobic

For COD above ~3,000 mg/L; produces biogas, saves aeration power.

DAF

Dissolved-air flotation for oily, fatty or light-solid effluents (food, dairy, refinery).

Chemical precipitation

Hydroxide/sulphide precipitation for chromium, nickel, zinc, copper, fluoride.

RO + MEE (ZLD)

Membrane recovery plus evaporation where discharge is not permitted.

Industry by industry

Textile, dyeing and laundry
Strong colour, dyes, surfactants, high TDS and temperature. Colour removal by coagulation or ozone, biological treatment, and RO/ZLD where the CETP or consent requires it.
Pharmaceutical and API
High and variable COD, solvents, antibiotics, toxicity to biology. Stream segregation, solvent stripping, anaerobic + aerobic stages, MEE for high-TDS concentrates.
Speciality and fine chemicals
Wide pH swings, phenols, ammonia, salts. Robust chemical pre-treatment, equalisation sized for batch campaigns, resistant biology.
Food, beverage and dairy
High BOD, fats/oil/grease, CIP caustic and acid. DAF or fat trap, anaerobic pre-treatment for dairy and brewery, aerobic polishing.
Metal finishing, automotive, engineering
Chromium, nickel, zinc, copper, cyanide, phosphate, paint-booth effluent. Segregated chemical treatment, reduction/precipitation, filter press.
Hospitals and hotels
Laundry and kitchen streams, disinfection and pharmaceutical residues. Grease trap, biological treatment, chlorination/UV.
Refinery and petrochemical
Oil, sulphide, phenol, ammonia. API separator, DAF, biological, tertiary — to CPCB refinery norms.

How KK Enviro Engineers delivers an ETP

Sampling and inlet characterisation → process selection and mass balance → PFD, P&ID and equipment sizing → civil and mechanical drawings → BOQ and procurement → erection supervision → seeding, commissioning and performance guarantee test → O&M. As a packaged skid for small capacities, or a site-built turnkey plant for large ones.

Frequently asked questions

How much does an ETP cost?

It depends on flow, inlet strength and the outlet required. A simple physico-chemical plant for low-strength effluent costs a fraction of a high-COD pharma ETP with anaerobic, aerobic and ZLD stages. Send your inlet analysis and flow — we give a budget range within one working day.

How much space does an ETP need?

Roughly 1–2.5 m² per KLD for a conventional plant, less for MBR or packaged units. Anaerobic and ZLD stages add area. We give a footprint with every preliminary scheme.

What are the discharge norms for industrial effluent in India?

General standards under the Environment (Protection) Rules: pH 5.5–9, BOD ≤ 30 mg/L, COD ≤ 250 mg/L, TSS ≤ 100 mg/L, oil & grease ≤ 10 mg/L, with industry-specific limits for parameters such as colour, phenol, ammonia, chromium and TDS. Your consent to operate from the State Pollution Control Board states the exact limits that apply.

Can treated effluent be reused in the plant?

Yes — after tertiary filtration and, where needed, UF and RO, treated effluent is commonly reused for cooling towers, floor washing, gardening and, in many plants, process make-up. Reuse reduces fresh-water cost and is mandatory in ZLD areas.

How long does it take to build an ETP?

A packaged skid for small capacity: 8–12 weeks. A site-built turnkey plant of a few hundred KLD: 5–8 months including civil work, followed by 4–8 weeks of biological seeding and stabilisation.

Have an effluent to treat?

Share your inlet analysis, capacity and location — we reply with a preliminary scheme and budget range within one working day.