Ozone Generator in Effluent Treatment Plant (ETP)

In ETP applications, ozone is injected into secondary-treated effluent (post-biological treatment) or directly into primary effluent for specific high-strength waste streams. The ozone contact system uses a Venturi injector or static mixer to achieve intimate gas-liquid contact, followed by a reaction tank with 15–30 minutes hydraulic retention time. For textile ETP colour removal, the optimal ozone dose is 3–6 mg/L; for pharmaceutical API removal, 5–10 mg/L; for food processing BOD reduction, 2–4 mg/L — each determined by the specific pollutant profile.

The mechanism of colour removal in textile ETP is ozone's attack on chromophore groups — the molecular structures responsible for light absorption and colour. Reactive dyes contain azo (-N=N-) and anthraquinone chromophores that ozone cleaves within seconds of contact, converting coloured dye molecules to small, colourless organic acid fragments. The apparent colour removal (measured by ADMI or spectrophotometer) reaches 90–95% at ozone doses of 4–6 mg/L, transforming highly coloured textile ETP effluent into water clear enough for river discharge or reuse in non-critical processes.

For pharmaceutical ETP applications, ozone attacks the aromatic ring structures and heterocyclic groups of API molecules that give them biological activity. Penicillin, fluoroquinolones, sulfonamides, and steroid hormones — all regulated under draft pharmaceutical ETP guidelines — are oxidised and mineralised at ozone doses of 5–10 mg/L. The hydroxyl radical pathway (•OH, generated when ozone reacts with water at neutral-to-alkaline pH) provides additional oxidation power, particularly for chlorinated compounds and persistent organic pollutants.

The OZ India ozone generator in ETP includes a dissolved ozone monitor that maintains real-time control of the ozone dose. During peak production periods when ETP influent load is highest, the ozone generator automatically increases output to maintain the target dissolved ozone residual. During shift changes or production shutdowns when ETP flow reduces, ozone production decreases proportionally — preventing over-dosing and wasting electricity. This automatic control reduces specific energy consumption by 20–30% compared to fixed-output ozone systems.

For ETP applications with high suspended solids (>50 mg/L) in the ozone contact feed, OZ India recommends installing a sand filter or dissolved air flotation (DAF) unit upstream of the ozone contactor. Suspended particles shield bacteria and organic compounds from ozone attack, reducing disinfection efficacy and increasing ozone demand. A turbidity below 5 NTU in the ozone contact feed ensures optimum ozone utilisation efficiency and minimum ozone dose requirement.

The ozone contact chamber off-gas — containing unreacted ozone at 0.5–2% concentration — must be safely destructed before venting to atmosphere. OZ India supplies catalytic ozone destructors (thermal-catalytic type using MnO₂ catalyst at 60°C) as standard with all ETP ozone systems, reducing off-gas ozone concentration below the OSHA 0.1 ppm limit. The destructor is sized for maximum ozone generator output and requires only annual catalyst replacement — ensuring safe operation without atmosphere contamination.

OZ India Technology ETP ozone systems are engineered for the specific pollutant profile of each industrial sector. Textile ETP systems are optimised for colour removal using intermediate pH adjustment (pH 9–10) to enhance hydroxyl radical generation, achieving >95% ADMI colour removal. Pharmaceutical ETP systems use extended contact time (30–45 min) and higher ozone doses for complete API mineralisation. Food processing ETP systems combine ozone with UV (AOP) for synergistic BOD reduction and odour elimination. Each system is preceded by a pilot study or design calculation from effluent characterisation data.

Standard OZ India ETP ozone package includes: CE-certified ozone generator (10-350g/hr), PSA oxygen generator or air preparation unit, ozone Venturi injector, PVDF non-return valve, PVDF ozone piping, dissolved ozone monitor with automatic control, ozone destructor for off-gas treatment, and ozone ambient air safety monitor. All components are 316L stainless steel and PVDF — materials fully resistant to ozone and industrial ETP chemicals. Skid-mounted package with factory testing before dispatch minimises site installation time.

OZ India provides process guarantees for ETP ozone systems based on the influent characterisation data provided by the client. Our standard guarantee: >90% colour removal for textile ETP (ADMI reduction from >500 to <50), >70% COD reduction for food processing ETP, and API reduction to below detection limits for pharmaceutical ETP at the specified ozone dose. If effluent quality targets are not achieved during commissioning, OZ India adjusts the system at no additional cost.

All OZ India ETP ozone installations include: detailed design report (P&ID, equipment layout, electrical load list), equipment supply with test certificates and CE declarations of conformity, installation supervision by certified engineers, 2-day operator training programme, and 1-year comprehensive warranty. Annual Maintenance Contracts are available with 4 preventive visits, emergency support, and all consumables (ozone electrodes, sensor membranes, catalyst) included. Our ETP installations in Surat textile cluster and Baddi pharmaceutical zone demonstrate sector-specific expertise.

ETP ozone sizing requires an effluent characterisation report: COD (mg/L), colour (ADMI or Pt-Co units), BOD, TSS, pH, and for pharmaceutical ETPs — the API compound and target removal standard. The specific ozone dose (mg O₃ per mg COD removed) depends on effluent type: 0.5–1.0 mg O₃/mg COD for food processing effluent; 1.5–2.5 mg O₃/mg COD for pharmaceutical effluent; 2.0–4.0 mg O₃/mg colour unit for textile effluent. Ozone generator capacity (g/hr) = ETP flow (m³/hr) × specific ozone dose × target removal.

For a typical 500 m³/day textile ETP with colour 800 ADMI and target <50 ADMI (94% removal), using a specific dose of 3.0 mg O₃/ADMI: Ozone required = 500/24 m³/hr × 750 ADMI × 3.0 mg/ADMI ÷ 1,000,000 = approximately 46 kg/day ÷ 24 = 1.9 kg/hr = 1,900 g/hr. This would require two 30-50g/hr units in parallel, or one 75-350g/hr unit with an oxygen generator. Contact OZ India with your effluent data for a precise sizing calculation and techno-economic comparison.

Contact time for ETP applications is 15–30 minutes HRT in a baffled reactor. For colour removal, 20 minutes HRT at pH 9–10 with turbulence (for hydroxyl radical promotion) is optimal. Existing ETP equalisation tanks, aeration basins (offline), or new concrete reactors can serve as ozone contact chambers — OZ India provides reactor design drawings with each project. Pilot-scale ozone testing (bench-scale or skid) is recommended for ETPs with unusual or complex effluent before final system sizing.