A method for treating a liquid using an apparatus includes: (a) a pump volute or hydrocyclone head having an inlet, and a throat having an outlet and a central axis, (b) a tank connected to the second opening of the throat, wherein the tank has a maximum inner diameter that is larger than an inner diameter of the outlet of the throat, and (d) a wave energy source having a first electrode within the pump volute or hydrocyclone head that extends through the outlet of the throat along the central axis, and a second electrode within the tank that is spaced apart and axially aligned with first electrode along the central axis. The method includes the steps of providing the above-described apparatus, supplying the liquid to the inlet of the pump volute or hydrocyclone head, and irradiating the liquid with one or more wave energies produced by the wave energy source.