Chemplast Sanmar's Mettur ZLD Journey

Chemplast Sanmar's Mettur plant in Tamil Nadu runs PVC and chlorochemicals operations near the Stanley Reservoir on the Cauvery system. Several production streams feed one combined wastewater flow with oil and grease, volatile organic compounds and high chemical oxygen demand.

In 2007, Chemplast announced an approximately ₹26-crore project to treat and reuse approximately 2,000 kilolitres per day of treated effluent. Its zero liquid discharge (ZLD) system combines reverse osmosis, evaporation and crystallisation to recover water and prevent routine discharge of treated process effluent outside the plant.

The company reports that Mettur achieved ZLD in September 2009 and received CII recognition in 2010. Its 2025 compliance filing states the unit still operates with ZLD, and ZLD salt is reused as raw material in another Chemplast plant.

The FY2024-25 BRSR states water metrics were not externally assured. That year, total water withdrawal rose 6.9% to 14,395,195 KL, recycled water used in process fell 6.1% to 510,295 KL, and water discharge rose 35.2%.