Electroplating & Metal Finishing Wastewater Treatment

Electroplating and metal finishing effluent is among the most hazardous industrial wastewater streams regulated under Indian environmental law. Unlike organic-dominated effluent from food or textile industries that can be treated by biological processes, electroplating wastewater contains toxic inorganic pollutants — hexavalent chromium (Cr VI), cyanide, and heavy metals including nickel, copper, zinc, cadmium, and lead — that require specialised physico-chemical treatment. These compounds are acutely toxic at very low concentrations, are persistent in the environment, and bioaccumulate in the food chain.

India has a large and fragmented electroplating sector, with an estimated 7,000–10,000 units across industrial clusters in Pune (Bhosari), Mumbai (MIDC areas), Chennai (Ambattur), Bangalore, Ludhiana, Delhi NCR (Okhla, Noida), Faridabad, and Coimbatore. The majority of these units are small-to-medium enterprises in common industrial estates. State PCBs are increasingly cracking down on non-compliant ETP operation in these clusters, with CPCB's General Standards and Schedule VI standards specifying extremely tight discharge limits — hexavalent chromium at 0.1 mg/L and total chromium at 2.0 mg/L, cyanide (as CN) at 0.2 mg/L, and nickel/copper/zinc at 3–5 mg/L.

The complexity of electroplating ETP design lies in the requirement for stream segregation and sequential treatment. A chromic acid drag-out rinse cannot be sent to a biological treatment system — chromium is toxic to microorganisms at even low concentrations. Cyanide-bearing waste must be treated separately at alkaline pH before combining with acid streams. This segregation and sequential treatment approach requires careful P&ID design, appropriate chemical dosing systems, multiple reaction tanks, and a control system that manages the pH adjustment and chemical dosing sequence. Spans Envirotech has designed and commissioned electroplating ETPs for auto component manufacturers, consumer electronics suppliers, and defence equipment manufacturers across India.

Water reuse is increasingly important for electroplating units — rinsing operations consume significant volumes of deionised or demineralised water, and reducing freshwater consumption reduces both operational costs and environmental footprint. Treated effluent from the final polishing stages (activated carbon filter) can be partially recycled to rinsing operations if quality is adequate. For units pursuing full water recovery, an RO system after the polishing stage concentrates remaining dissolved solids for evaporation and disposal, recovering near-pure permeate for DI water production.