Treatment of steel plant generated biological oxidation treated (BOT) wastewater by hybrid process

Abstract

This work describes the combined effect of ozonation and electrocoagulation for the treatment of steel industry wastewater since only ozonation or electrocoagulation is incompetent to reduce the pollutant level below the permissible limit. Biological oxidation treated (BOT) effluent consisting of colored compounds, phenol, iron, and ammonia from a steel industry, was considered here. The effects of operating variables like ozone generation rate and current density on pollutant removal were analyzed for the hybrid process. It was observed that experimental conditions such as an ozone generation rate of 1.33 mg/s, ozonation time of 40 min, a current density of 100 A/m2, and an electrolysis time of 30 min were sufficient for reducing all the pollutant concentration below the permissible limits. The removal capacity of the combined process was found to be 98.2%, 99.5%, 90.6%, and 62.8% for color, phenol, iron, and ammonia, respectively. A kinetic study was performed for the degradation of the pollutants during the hybrid process. The pseudo-first-order kinetic model was found to be best suited for the analysis with the R2 value of about 0.99 for iron, ammonia, phenol, and color, respectively, for an optimum ozone generation rate of 1.33 mg/s. The mass transfer study illustrates an increase in the dissolved ozone concentration in the solution for an increase in the volumetric mass transfer coefficient, Kla. The readers of this article will be highly benefitted after acquiring comprehensive knowledge on the efficacy of a hybrid process for the treatment of BOT water from the steel industry.