Efficiency of plasma treatment of water contaminated with persistent organic molecules

The authors examined the efficiency of plasma-pulse-driven dielectric barrier discharge oxidation of a solution of methylene blue (C₁₆H₁₈ClN₂S) and wastewater from dye-producing plants, in which the main component is 2,4-dinitrotoluene (CH₃C₄H₃(NO₂)₂), as well as models of the organic component of wastewater of nuclear power plants, the main constituent of which is a phosphate (PO₄ ³⁻)-based detergent with a 26.8% surfactant content. Water films with a thickness of 0.1 mm were processed with a discharge voltage equal to 3 × 10¹¹ V/s. The energy efficiency of water treatment was studied against the specific energy input, the frequency of the repetition of the discharge pulses and the parameters of the fluid and gas going through the discharge chamber. The highest energy output was reached at an air velocity in the discharge chamber of ∼1 cm/s, which provides a concentration of ozone (O₃) of ∼1.5 mg/l. The highest energy output, the processing of 87 g of wastewater with 1 kWh, was obtained by treating an aqueous solution of methylene blue with an initial concentration of 50 mg/l at 65% decomposition. An energy consumption of 10 J is the most efficient value for treatment of the tested 10 ml wastewater samples.