Performance and energetic analysis of hydrodynamic cavitation and potential integration with existing advanced oxidation processes: A case study for real life greywater treatment

The current work is a first of a kind report on the feasibility and efficacy of hydrodynamic cavitation integrated Advanced Oxidation Processes (AOP's) towards treatment of a real life greywater stream in form of kitchen wastewater. The work has been carried out in a sequential manner starting with geometry optimization of orifice plate (cavitating device) followed by studying the effects of inlet pressure, pH, effluent dilution ratio on degradation of TOC and COD. Under optimized conditions of pH 3, 4 bar pressure, TOC and COD reduction of 18.23 and 25% were obtained using HC for a period of 120 min. To improve the performance of HC, further studies were carried out by integrating H2O2 and O-3 with HC. Using 5 g/h optimum dosage of H2O2, 87.5% reduction in COD was obtained beyond which it started decreasing. Moreover, integrating O-3 (57.5% reduction in COD) increased the treatment cost. However, a hybrid process (HC + H2O2 + O-3) yielded 76.26 and 98.25% reductions in TOC and COD within 60 min. The energetics of all the processes and the treatment costs were studied in detail and it was concluded that combined process of HC + H2O2 + O-3 surpassed by far the performances of HC + H2O2 and HC + O-3.