Acoustic and hydrodynamic cavitation-based combined treatment techniques for the treatment of industrial real effluent containing mainly pharmaceutical compounds

Abstract

The current work investigates the effectiveness of hybrid treatment techniques involving cavitation combined with AOPs for treating real industrial effluent obtained from common effluent treatment plant (CETP), which contains dominantly recalcitrant pharmaceutical pollutants. A laboratory scale study was performed initially using ultrasonic horn to optimize the operating parameters to be used for combination schemes as AC/H2O2, AC/Fe(II)/H2O2, AC/KPS and AC/O3. The maximum extent of Chemical Oxygen Demand (COD) reduction was observed as 83.53% for AC/Fe(II)/H2O2 system at 1:5 ratio of Fe(II) and H2O2 under the best operating conditions of 125 W ultrasonic power, 22 kHz frequency, pH of 3 and time of 60 min. The scaleup possibility of AC has been explored by utilizing a novel US reactor for the treatment of 4000 mL of effluent at the optimized conditions. Large scale US reactor also showed the best results for AC/ Fe(II)/H2O2 system yielding 81.47% COD reduction. A comparison of the efficacy of HC and AC has also been established by performing a set of experiments using the combinations as HC/ H2O2, HC/Fe(II)/ H2O2, HC/KPS, and HC/O3 at same capacity. A maximum COD reduction of 87.4% was achieved for the HC/Fe(II)/ H2O2 system at pH 3 and inlet pressure of 4 bar. The study also established the comparison of kinetic rate constants and treatment costs for different approaches. Overall, the large scale potential for the treatment of real industrial effluent involving the pharmaceutical pollutants using combination of cavitation and AOPs has been demonstrated.