The Central Pollution Control Board's Zero Liquid Discharge notification has been on the books since 2016. But in 2025, enforcement is a different matter. The National Green Tribunal has issued closure orders to over 400 textile units in Gujarat and Tamil Nadu. PCBs are conducting surprise inspections. The days of ignoring ZLD compliance are over.
What is Zero Liquid Discharge?
Zero Liquid Discharge is not a single technology — it is a treatment outcome. A ZLD plant eliminates all liquid effluent discharge from an industrial site by treating wastewater to recover usable water and converting residual waste to a dry solid (typically salt). The plant boundary has no liquid outlet.
In practice, a ZLD train for a textile unit looks like this: raw effluent → ETP (biological + chemical) → RO concentration → Multiple Effect Evaporator (MEE) → Agitated Thin Film Dryer (ATFD) → dry salt. The recovered RO permeate (70–80% of the feed) returns to your process.
Which industries are affected by the ZLD mandate?
- Textile processing units in notified clusters (Tirupur, Surat, Panipat, Ludhiana)
- Pharmaceutical manufacturers classified as "Red" category
- Tanneries and leather processing units
- Dye and dye-intermediate manufacturers
- Caustic soda, soda ash, and chlor-alkali plants
- Sugar mills with attached distilleries
- Large hotels (>100 rooms) in some states per SPCB consent conditions
Penalties and enforcement actions
The Environment Protection Act (1986) empowers the CPCB and State PCBs to issue closure directions, environmental compensation orders, and FIRs under Section 15 (which carries imprisonment up to 7 years). The National Green Tribunal has issued closure orders to over 400 textile units in Gujarat and Tamil Nadu alone.
Enforcement timelines have shortened significantly since 2023. In Gujarat, show-cause notices are now followed by closure orders within 30–45 days if no compliance plan is submitted.
Technical requirements for a compliant ZLD plant
| Stage | Technology | Key Output Parameter |
|---|---|---|
| Pre-treatment | Primary ETP | TSS <50 mg/L, COD <500 mg/L (RO feed) |
| Secondary treatment | Biological (MBBR/SBR) | BOD <30 mg/L |
| RO concentration | High-rejection RO | Permeate TDS <100 mg/L; reject TDS 15,000–30,000 mg/L |
| Thermal evaporation | MEE (3-effect) | Condensate TDS <50 mg/L; concentrate 25–30% solids |
| Final drying | ATFD | Dry salt >98% purity |
What does ZLD cost?
Capital cost for a 500 KLD ZLD plant (ETP + RO + MEE + ATFD) typically ranges from ₹3.5 Cr to ₹5.5 Cr depending on inlet water quality, technology selection, and site constraints. Operating costs are ₹80–120 per KL treated.
How long does it take to commission a ZLD plant?
For a 500 KLD system: detailed engineering 6 weeks, procurement 8 weeks (overlapping), civil construction 10–12 weeks (overlapping), erection and commissioning 4–6 weeks. Total: 22–28 weeks from order placement to operation.
Ready to discuss your ZLD requirement?
Navbharat Water engineers have commissioned ZLD plants from 10 KLD to 10 MLD across India. Tell us your inlet profile and compliance target.
Request a Technical Audit