Physicochemical wastewater treatment improvement by hydrodynamic cavitation nanobubbles

Abstract

Hydrodynamic nanobubble aeration is proposed as an innovative approach to enhancing physicochemical wastewater treatment. Integrating a novel cavitation system to replace conventional aeration significantly improves standard oxygen transfer efficiency and energy consumption. The changes in size and surface charge of air, oxygen (O2), ozone (O3), and chitosan nanobubbles were studied as a function of the reactor diameter. Interestingly, it was found that increasing the radial dispersion length had no significant effect on the measured parameters. Flotation, Coagulation-flocculation (CF), and Advanced Oxidation (AOPs) processes of municipal wastewater comparing convective air and O3 NBs aeration were carried out at pilot plant scale. The use of O3 NBs in the flotation process improves 160 % the suspended solids removal compared to the air-NBs- process. The CF process was evaluated by adding a chitosan dose to the convective processes and monitoring the water quality parameters in real-time. The results demonstrated that the interaction of chitosan with O3 NBs eliminates more than 80 % of the initial chemical oxygen demand (COD). Finally, the AOP carried out with O3 NBs reaches a removal efficiency of 99.8 % total suspended solids and 90 % COD. This modular system presents a practical and efficient alternative for removing municipal and industrial wastewater contaminants.