Hydrodynamic cavitation is being increasingly pursued for developing intensified and compact wastewater treatment process. Experimental data on the degradation of water contaminated with three commonly used solvents – acetone, ethyl acetate (EA) and isopropyl alcohol (IPA) using vortex based cavitation devices is presented. Influence of operating flow or pressure drop across cavitation device (150 to 300 kPa), operating temperature (20 to 45 oC), concentration of pollutant (1000 ppm to 50000 ppm) and scale of cavitation reactor (with scale – up factor of 4 maintaining the geometric similarity) has been reported. A new reaction engineering model based on the number of passes through cavitation device was developed to interpret degradation behaviour. The model provides a convenient way to estimate the per-pass degradation factor from batch experiments, allows its extension to continuous processes and to more sophisticated models of estimating generation of hydroxyl radicals. The model showed excellent agreement with experimental data. The per-pass degradation factor exhibited a maxima with respect to pressure drop (200 – 250 kPa) across cavitation device. Aeration was found to improve degradation performance up to 1 vvm ([L/min]gas/Lliquid]). The initial concentration of acetone (1000 to 50000 ppm) and IPA (1000 to 22000 ppm) was found to have negligible effect on degradation performance. The per-pass degradation factor for EA was 1.5 and 4 times of Acetone and IPA respectively. The effect of two sales (nominal capacities of the small and large-scale devices used were 0.3 m3/hr and 1.2 m3/hr respectively) was investigated for the first time and it was found that per-pass degradation factor decreased with scale. The presented model and experimental data provide new insights into application of hydrodynamic cavitation for wastewater treatment and provide a basis for further work on scale–up of hydrodynamic cavitation devices. The results will be useful to researchers as well as practicing engineers interested in harnessing hydrodynamic cavitation for water treatment.
- hydrodynamic cavitation, vortex, per-pass degradation, aeration, scale-up