Discharges in water and applications to wasted water treatment

An electrical discharge in a bubble in water and above the water surface were applied to generate active radicals such as atomic oxygen, ozone and hydroxyl for wasted water treatment. The discharge along the inside of the bubble was optically observed. The onset voltage for different gases was measured with the different water conductivity. The use of discharge above the water surface was proposed for the treatment of water including the surfactant (i.e. Nonylphenol ethoxylate) exhausted from a factory. The effect of water treatment was estimated by the COD measurement. According to the experimental results, the active radicals such as atomic oxygen whose emission wavelength was 777 nm and OH radicals whose emission wavelength was 306.7 nm and 308.9 nm were confirmed for the different repetition rate of discharge (100-300 Hz). The COD removal of about 19 % was obtained and the efficiency of water treatment was 0.74 mg/kWh.