A treatment system (10, 110, 210) for treating water in a water system with a plasma discharge, the treatment system comprising: a reaction chamber (36, 136, 236) comprising an inlet in fluid communication with part of the water system and configured to receive at least a portion of water from the water system, an outlet in fluid communication with part of the water system and configured to return the portion of water back to the water system, a body, a high voltage electrode, and a ground electrode, wherein the high voltage and ground electrodes are configured to be submerged in the water to be treated; a gas infusion system disposed upstream of the inlet or within the body of the reaction chamber; a high voltage generator (40, 140, 240) comprising a Marx generator disposed within a spark gap chamber, the spark gap chamber is provided within an outer housing that includes a dielectric barrier, air pumps or other devices to pressurize or blow air are provided to flush air across the electrodes of the Marx generator and out of the spark gap chamber, the high voltage generator (40, 140, 240) is adapted to generate a high frequency and high voltage over 200kV and is connected to the high voltage electrode (40, 140, 240), so that a plasma discharge is generated within the chamber (36, 136, 236); and an isolation transformer or uninterruptable power supply (146, 246) connected to the high voltage generator (40, 140, 240); and grounding devices (58, 56, 52, 488, 148, 156, 256, 248) connected to components of the water system; wherein the gas infusion system and the high voltage generator (40, 140, 240) are adapted so that ozone gas (30, 130, 230) is produced as a by-product by air flushing of the spark gap chamber in the high voltage generator (40, 140, 240) and supplied to the gas infusion system to treat the water. a reaction chamber (36, 136, 236) comprising an inlet in fluid communication with part of the water system and configured to receive at least a portion of water from the water system, an outlet in fluid communication with part of the water system and configured to return the portion of water back to the water system, a body, a high voltage electrode, and a ground electrode, wherein the high voltage and ground electrodes are configured to be submerged in the water to be treated; a gas infusion system disposed upstream of the inlet or within the body of the reaction chamber; a high voltage generator (40, 140, 240) comprising a Marx generator disposed within a spark gap chamber, the spark gap chamber is provided within an outer housing that includes a dielectric barrier, air pumps or other devices to pressurize or blow air are provided to flush air across the electrodes of the Marx generator and out of the spark gap chamber, the high voltage generator (40, 140, 240) is adapted to generate a high frequency and high voltage over 200kV and is connected to the high voltage electrode (40, 140, 240), so that a plasma discharge is generated within the chamber (36, 136, 236); and an isolation transformer or uninterruptable power supply (146, 246) connected to the high voltage generator (40, 140, 240); and grounding devices (58, 56, 52, 488, 148, 156, 256, 248) connected to components of the water system; wherein the gas infusion system and the high voltage generator (40, 140, 240) are adapted so that ozone gas (30, 130, 230) is produced as a by-product by air flushing of the spark gap chamber in the high voltage generator (40, 140, 240) and supplied to the gas infusion system to treat the water.