Enhancement of wastewater and sludge treatment processes by hydrodynamic cavitation

In the past decades, hydrodynamic cavitation (HC) process was the subject of study by many researchers worldwide. This phenomenon was widely studied in order to understand the reason of its negative effects on hydraulic machinery such as pumps,turbines, valves, etc. Many efforts were made in order to better understand mechanisms of HC process with the main aim of preventing its generation and trying to avoid severe physical damage such as erosions, vibrations and noises. In recent years, in order to cope with a decrease in available water resources worldwide, an increasing demand of water by population in developing/developed countries and more restrictive environmental legislations on water quality, HC was increasingly used as a novel energy-efficient technique in the field of wastewaters treatment. The main purpose of this thesis is to investigate on the effectiveness of a modified swirling-jet device called Ecowirl reactor, patented by Econovation GmbH, Germany and produced and commercialized by Officine Parisi s.r.l., Italy. Experimental studies were carried out in order to evaluate the effects of different operative conditions and parameters such as reactor geometry, flow rate, flow velocity, pressure, medium pH, medium concentration and medium temperature on (i) the degradation of a toxic and carcinogenic pollutant dye (Rhodamine B, RhB) in waste dye aqueous solutions and on (ii) the improvement of activated sludge solubilisation and aerobic sludge biodegradability in the field of biological wastewater treatments. In order to better understand the fluid dynamics into Ecowirl reactor, it was modelled. The model based on previous experimental data was implemented in a Computational Fluid Dynamics software (ANSYS, 16.2).