CPCB Effluent Standards for Recycled Paper Mills — Explained

Regulatory Basis and CPCB Schedule

Effluent standards for recycled paper and de-inking mills are notified under Schedule I (industry-specific norms) of the Environment Protection Rules, 1986 (EPR). The schedule distinguishes between three categories of paper mills: (a) large integrated pulp & paper mills using virgin fibres, (b) small paper mills using agro-residues, and (c) recycled fibre-based mills including those with de-inking facilities.

Recycled paper mills classified as Red Category industries by CPCB must obtain Consent to Establish (CTE) and Consent to Operate (CTO) from the State Pollution Control Board (SPCB) and install an online effluent quality monitoring system (CEQMS) if daily discharge exceeds 100 KLD. Medium-scale mills (10–100 KLD discharge) are required to connect to the state-level OCEMS network under the CPCB real-time monitoring framework.

Key Pollutants in Recycled Paper Mill Wastewater

Wastewater from recycled paper mills arises at multiple stages of the process and carries a characteristic mix of pollutants:

• Suspended solids (fibre fines & fillers): Kaolin, calcium carbonate, and titanium dioxide coatings from coated waste paper generate high TSS loads that are difficult to settle without coagulation.
• Ink particles: De-inking operations release hydrophobic ink droplets, carbon black, and UV-cured resin particles into flotation reject streams.
• BOD/COD from starch and sizing agents: Surface sizing chemicals, broke dissolving, and paper machine whitewater contribute soluble BOD and COD.
• Adsorbable Organic Halogens (AOX): Mills using sodium hypochlorite or chlorine dioxide for pulp brightening generate chlorinated organic compounds.
• Colour: Coloured waste-paper grades, dyes, and ink residues impart dark colouration that requires ozonation or coagulation to remove.
• Dissolved salts (conductivity): Repeated water recycling concentrates dissolved solids and can impair paper machine runnability.

Prescribed Effluent Discharge Standards

The following limits apply to recycled paper mills discharging treated effluent to inland surface water bodies. These are the regulatory thresholds that ETP design must achieve:

* AOX limit applies only to mills using elemental chlorine or chlorine compounds in bleaching/de-inking. Mills using totally chlorine-free (TCF) processes are exempt.

Specific Water Consumption and Volume Norms

Water consumption norms for recycled paper mills are expressed as Specific Water Consumption (SWC) — cubic metres of fresh water drawn per tonne of paper produced. Reducing SWC is both an environmental obligation and a cost-saving measure.

Mills exceeding these SWC norms during SPCB inspections face potential CTO suspension. Installation of sub-metering at each process stage (pulper, paper machine, coater, ETP) is required under CPCB effluent minimisation guidelines.

De-inking Process and AOX Control

De-inking is the core process in recycled newsprint and printing-grade paper production. Waste paper is pulped in a alkaline medium (NaOH + sodium silicate + hydrogen peroxide), and ink is removed via wash de-inking or flotation de-inking. AOX generation depends on the bleaching agent used:

• Elemental Chlorine Free (ECF): Chlorine dioxide replaces elemental chlorine, reducing AOX to 0.5–1.0 kg/tonne.
• Totally Chlorine Free (TCF): Hydrogen peroxide and ozone only — AOX is effectively zero; CPCB AOX standard not applicable.
• Conventional chlorine bleaching: AOX can reach 3–5 kg/tonne; upgrade to ECF or TCF is strongly recommended and increasingly enforced by SPCBs.

De-inking rejects (flotation froth, screen rejects, sludge) must be disposed of as solid waste per Solid Waste Management Rules, 2016. If rejects contain hazardous inks (e.g., heavy-metal based pigments), they must be treated as Hazardous Waste under Hazardous Waste Management Rules, 2016.

Recommended ETP Configuration

A robust ETP for a recycled paper mill with de-inking typically incorporates the following unit operations in sequence:

1. Screens and fiber recovery: Drum screens (1–6 mm) or vibrating screens ahead of the ETP recover paper fibre for reuse, reducing BOD and TSS loads.
2. Equalization tank: Minimum 8–12 hours HRT to buffer pH swings (4–10 from alkaline pulping vs. acidic paper machine whitewater) and flow variability.
3. Coagulation-flocculation and Dissolved Air Flotation (DAF): Alum or PAC at 50–150 mg/L followed by anionic polymer achieves 80–90% TSS removal and removes ink particles that would overwhelm biological treatment.
4. Aerobic biological treatment (ASP or MBBR): Extended aeration or MBBR at HRT 12–18 hours for BOD reduction to <30 mg/L. MBBR is preferred for mills with high suspended-solids recycle as it tolerates shock loads better.
5. Secondary clarifier: Surface overflow rate 20–30 m³/m²/day.
6. Tertiary treatment (optional): For colour removal, ozonation (5–10 mg/L O₃) or coagulation with lime achieves colour reduction to <100 Pt-Co units.
7. Sludge dewatering: Belt press or centrifuge; primary sludge from DAF has low dewaterability — polymer conditioning at 4–8 kg/tonne sludge DS is typical.

Grey-Water Recycling and ZLD Pathways

Recycled paper mills are well-suited for grey-water recycling because treated ETP effluent can be reused in non-critical applications (shower water on wires, seal water, cooling towers) without affecting paper quality:

• Paper machine white-water recovery: Closed loop recycling of paper machine white water (via save-all or micro-flotation) is the single largest water-saving measure, recovering 50–70% of process water internally.
• ETP treated water reuse: Secondary treated effluent (post-ASP) meeting ≤50 mg/L BOD can be recycled to the pulper, reducing SWC by 30–40%.
• ZLD requirement: Mills located in critically polluted areas (CPA) or notified industrial clusters may be directed by NGT or SPCB to achieve Zero Liquid Discharge (ZLD), requiring RO + MEE (Multiple Effect Evaporation) for the rejected brine stream.

Compliance Checklist and Best Practices

Use this checklist during SPCB inspections or internal audits to verify compliance:

• Daily BOD, COD, TSS, pH, TDS sampling records maintained for all consent points with lab reports.
• SWC sub-meters installed at pulper, paper machine, and ETP inlet; monthly water audit report submitted to SPCB.
• If using chlorine compounds in de-inking — AOX measured monthly by NABL-accredited lab; results kept on file for 3 years.
• OCEMS / CEQMS transmitter operational with real-time data transmission to SPCB server (required for discharge ≥100 KLD).
• De-inking rejects characterised and disposed through authorised waste disposal — hazardous waste manifest if heavy metals detected.
• ETP operator trained and certified per CPCB guidelines; logbook entries up to date.
• Annual Environment Statement (Form V) filed within 30 September each year.
• Consent to Operate renewal applied for 120 days before expiry.

Frequently Asked Questions

Disclaimer: This article is for general informational purposes only. Discharge standards are subject to amendment by CPCB/MoEFCC. Always verify applicable limits with your SPCB and the latest gazette notifications before designing or operating an ETP.