A method for treating a liquid includes providing an apparatus: (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 outlet 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 comprising a first electrode within the pump volute or hydrocyclone head that is aligned with 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 liquid is supplied to the inlet of the pump volute or hydrocyclone head. The first electrode, second electrode or both electrodes are moved along the central axis. The liquid is irradiated with one or more wave energies produced by the wave energy source.
