Water treatment in WAPULEC device occurs due to electric pulsed corona discharge (PCD) in a gas medium, to which water is showered in droplets, jets and films directly to the discharge zone.
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.
Corona discharge arrangement
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.
Photograph of pulsed corona discharge
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.
Results of oxidation are:
- Decomposition of organic substances (they are either completely mineralized to water and carbon dioxide or transformed into less toxic compounds)
- Transformation of inorganic substances (e.g. iron, manganese) into insoluble forms, easily removable by mechanical filtration or precipitation.
- Abatement of microorganisms (water disinfection)