Treatment of cold rolling mill (CRM) effluent of steel industry

The study establishes the performance of standalone ozonation and electrocoagulation processes for the treatment of Cold Rolling Mill (CRM) effluent consisting of phenol, COD, BOD, iron, and oil content from the Tata Steel Industry, India. The operational variables of both the standalone processes, viz. current density (electrocoagulation), ozone generation rate (ozonation), and treatment time, were addressed to analyse its effect on the removal efficiency of each process separately. Optimum experimental conditions of 200 A m(-2) (current density), 1.12 mg s(-1) (ozone generation rate), and 30 min (treatment time) were adequate in lowering the amount of pollutant content below its respective discharge limits. However, it was observed that, standalone electrocoagulation process proved to be more efficient compared to ozonation, both in terms of economy and pollutant reduction efficiency for the targeted effluent. Also, the cost of ozonation process was found to be about six times than that of electrocoagulation. The kinetic study conducted showed that pseudo-first-order reaction fitted best with the highest R-2 of 0.99 for phenol, COD, BOD, iron, and 0.98 for oil. Moreover, mass transfer analysis for ozonation indicates an increase in the volumetric mass transfer coefficient (Kla) with an increase in the ozone generation rate. The efficiencies and operating costs for both the standalone processes were found to be satisfactory compared to that of other methods reported in the literature.

Automated summary

The study shows that in treating effluent from the Cold Rolling Mill of Tata Steel Industry in India, the standalone electrocoagulation process is more efficient and cost-effective compared to ozonation. The optimal experimental conditions can reduce pollutant content below discharge limits, with the cost of ozonation process being about six times that of electrocoagulation.