Optimization of bromocresol green degradation using ozone micro bubbles: response surface analysis and techno-commercial aspects of a 75 kL/day scale-up plant

Degradation of bromocresol green in alcohol-water solution using ozone micron sized bubbles is reported. A high speed impeller is used to generate micro bubbles of ozone in liquid while ozone is generated using a commercial ozone generator. A 3-level-3-factor Box–Behnken experimental design is used to statistically identify relative importance of the operating parameters studied namely impeller speed, initial concentration of dye and treatment time. Ozone dosage is kept fixed at 4 g/h. Impeller speed is found to be the most dominant factor according to Analysis of Variance (ANOVA) calculations. Kinetics for degradation of bromocresol green in solution is also reported. A second order kinetics is seen to fit the experimental (concentration–time) data, corresponding value of rate constant being 0.0153 L/mg-s. Based on the laboratory scale data a detailed techno-commercial analysis of a scaled up (75 kL/day) plant for ozone based degradation of bromocresol is presented. All relevant economic indicators pertaining to the scaled up plant are reported. A specific treatment cost of Rs. 100/m³ of treated water yields a return on investment (ROI) of 68.77 and discounted payback period of 5 years.