Modified pinhole discharge for water treatment

A modified pinhole discharge with coaxial electrodes has been developed. An inner tubular stainless steel anode (O 12 mm) is coaxial with a cylindrical outer cathode (O 100 mm). The anode is covered by a polyethylene insulator and one or three small holes (O 0.7 mm) are drilled in the central part of the anode. Treated liquids are pumped into the inner volume of the anode; it flows into the interelectrode volume through the holes and circulates back to the anode volume. Pulse power supply consists of a 7 or 14 nF storage capacitor charged up to 30 kV and rotating spark gap switch. Pulse repetition frequency was 50 Hz and the solution conductivity was varied in the range of 0.3-1 mS/cm. Production of hydrogen peroxide at a similar rate as in the needle-plate reactors has been measured. Decolorizing of the organic dye "reactive blue 137" and reduction of the number of living bacteria by four orders of magnitude have been demonstrated.