Abstract: Based on laboratory research and pilot experiments, an industrial water treatment system combining ozonation with hydrodynamic cavitation has been developed to remove algae from eutrophicated waterbodies. A comparative study was performed to compare the technologies of "complex cavitation/ozone", "extrusion cavitation/ozone", "suction cavitation/ozone", "ozonation alone" and "orifice plate aperture" in water treatment efficiency, relative to chlorophyll a, UV₂₅₄, COD and NH₃-N contents and turbidity in treated water. Meanwhile, comparison was done between "complex cavitation/ozone" and "ozone alone" in some economic and technological indices, such as ozone utilization rate and net purification rate per unit of ozone and energy consumed. Results show that the technology of "complex cavitation/ozone" reached 44.5% and 88.9% in chlorophyll removal rate and 0.89 and 1.78 kW·h·m^-3in per unit energy consumption, respectively, during the period of stable discharge, when operated at 10 or 5 m³·h^-1. Moreover, the indices of turbidity, UV₂₅₄ and COD all dropped significantly. The two technologies were also found better than the others in the other economic and technical indices. Therefore, it is concluded that the "hydrodynamic cavitation/ozone" system can be applied to quick and effective elimination of algae and chlorophyll, suppression of algal blooms, and reduction of ecological damage and economic losses that may be caused by algal blooms and dead algae.