he combination of hydrodynamically generated cavitation with disinfectants is a new approach for disinfection of water. The aim of this study was to investigate the inactivation of Escherichia coli at high cell densities (∼107 cells mL–1) with a combination of hydrodynamic cavitation and chlorine dioxide. A new type of hydrodynamic cavitation reactor (micro wire mesh with downstream nozzle) was developed, which consumes 30% less energy than conventionally used orifice plates at similar flow rates. Compared with sole chlorine dioxide incubation the combination of chlorine dioxide with hydrodynamically generated cavitation resulted in a reduction of 50–70% of incubation time for 99% cell inactivation at an initial chlorine dioxide concentration of 0.25 mg L–1. The final viable cell number was reduced by a factor of 100–1000 compared to sole chlorine dioxide disinfection. An energy demand of ∼0.1–0.2 kWh m–1 is necessary to induce hydrodynamic cavitation at these optimum operation conditions (cavitation number of 0.13–0.17). Higher inactivation rates, the reduction of surviving cells by orders of magnitude compared to sole chlorine dioxide inactivation or the reduction of initial chlorine dioxide concentration compensate for the additional energy demand.
Combination of hydrodynamic cavitation and chlorine dioxide for disinfection of water