A treatment system for treating water, such as produced water that is produced during hydraulic fracturing. The system employs a combination of a plasma spark discharge and an RF oscillating electric field. The plasma spark discharge and the RF oscillating electric field may be employed simultaneously or in an overlapping manner within a chamber to treat the water. The treatment system is able to kill microorganisms as well as reduce or eliminate fouling due to, for example, bicarbonates. In some embodiments, grids are employed to further enhance the heat produced by the RF oscillating electric field.