Design of hydrodynamic cavitation-based advanced oxidation process for degradation of recalcitrant micropollutants originating from tertiary effluent streams: a case study with norfloxacin

Treatment of micropollutants even after tertiary treatment and developing cost-effective, sustainable and energy-efficient technology for the same still remains an active area of research. The present study reports the feasibility and efficacy of hydrodynamic cavitation (HC)-based advanced oxidation process (AOP) for the degradation of norfloxacin. Experiments using HC were carried out in a sequential manner starting with the optimization of the cavitating device (orifice plate) using computational fluid dynamics (CFD) followed by optimizing the operational parameters such as pH, inlet pressure and initial concentration. An experimental study revealed that under optimized conditions of pH - 2, inlet pressure - 6 bar and initial conc - 250 mu g/L, NRF degradation of 22.26% was obtained using HC in an experimental run of 60 min. For further improvement of the HC process, experiments were carried out by integrating with H2O2, O-3 and Fenton's reagent. Under the optimized conditions, integrating with H2O2, O-3 and Fenton's reagent enhanced the extent of NRF degradation. The energetics of the process was further evaluated to understand the techno-economic viability. The study revealed that HC + H2O2 consumed less energy of 8.01 kWh/m(3) at the economics of Rs. 82.53/m(3). Thus, HC combined with oxidizing agents can be a novel technique in the genre of AOP for the degradation of micropollutants.