An apparatus includes a fine bubble generator, a gas supplying source, a first plasma generator, a second plasma generator, a power source and a control module. The fine bubble generator is configured to generate fine bubbles in a liquid. The gas supplying source is configured to supply a working gas. The first plasma generator is configured to generate a first plasma gas from the working gas. The second plasma generator is configured to generate a second plasma gas from the working gas. The power source is configured to supply electricity to the first plasma generator and the second plasma generator. The control module is configured to adjust the power source to provide power to the first plasma generator and the second plasma generator. The first plasma gas and the second plasma gas are directed into the liquid.