Water treatment in WAPULEC devices occurs due to electric pulsed corona discharge (PCD) in a gas medium. Water is showered in droplets, jets and films directly to the discharge zone.

Schematic diagram of WAPULEC device is shown in figure. Water is fed to the top of the reactor and the down-flow stream is evenly distributed between electrodes by a sprinkling device such as nozzle, perforated plate or perforated tube, in a shower mode.

Pulsed corona discharge is formed in air or oxygen at atmospheric pressure and propagates in a form of multiple low-energy channels called streamers, uniformly distributed over the volume between electrodes. The discharge takes place between two electrodes of highly non-uniform geometry, e.g. using a thin wire as high-voltage electrode, and a grounded plate, resulted in a concentrated electric field at the wire. The corona glow appears at the high-voltage electrode. To avoid transition of corona glow to a spark, high-voltage pulses of short duration are applied to the electrodes.

Scheme of pulsed corona water treatment

Pulsed corona is an effective source of active oxidant species, such as hydroxyl radical (OH), atomic oxygen (O) and ozone (O3), known as the most powerful oxidizers. Hydroxyl radical and atomic oxygen are formed on the surface of water droplets, so they easily react with the impurities in water.

Oxygen-based oxidizers are safe for the environment - they are decomposed shortly after their formation in the discharge. Unlike chlorine, they do not form toxic byproducts (trihalomethanes), therefore reducing risk to human health.

Active species such as OH radicals, ozone and atomic oxygen are generated close to the water surface which improves oxidation efficiency

Photograph of pulsed corona discharge

Mechanism of plasma treatment

  • inorganic substances oxidation

    Dissolved Fe, Mn, As and other species are transferred into insoluble forms by oxidation.

  • Disinfection

    Bacteria are removed at a low energy dose of 10-50 W hr/m3

  • Organic substances removal

    Removal of phenols, micropollutants, natural organic matter and the decrease of COD

  • Deodoration

    Removal of dissolved gases and water deodoration