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This paper presents the effect of a water-droplet spray and gas-phase discharge in a method of water treatment by spraying wastewater into nonthermal plasma. Three water-treatment methods by pulsed-power discharge were investigated. These are treatment methods by gas-phase discharge in the water-droplet spray, by ozone gas injected in water, and by ozone gas injected in the water-droplet spray. The comparison of gas-phase discharge in the water droplets with ozone gas injected in the water-droplet spray shows the effect of free radicals except ozone. The comparison of ozone gas injected in the water with ozone gas injected in the water-droplet spray shows the effect of the water-droplet spray. Brilliant-blue FCF solution was used as wastewater in the treatment. The decolorization rate of the treatment by spraying the water droplets into the gas-phase discharge reached 80% at 4 min. The decolorization time of the treatment by spraying water droplets into an atmosphere of ozone concentration of 250 and 100 ppm took 12 and 20 min to reach the decolorization rate of 80%, respectively. These results show that other radicals including OH radical and excluding ozone mainly contribute to decompose brilliant-blue FCF in the former treatment. The decolorization rate of the treatment by injecting ozone gas of concentration of 100 ppm into the water solution was 55% in time elapse of 40 min. The result shows that spraying water droplets into reacting fields in the water treatment results in faster decolorization time.