About 4000 km3 of water is used by humans each year around the world. Only 2.5% of Earth’s water resource is fresh water, and about 70% of fresh water present in the planet is frozen in the icecaps. Currently, one in three people in the planet is already facing water shortages and 1.8 billion people will face water shortages by 2025. Water scarcity and water quality degradation are therefore forcing consumers and industry to improve levels of water usage and reuse by implementing advanced water treatment technologies.
Wastewaters contain a wide variety of substances and complex mixtures of organic matter, often disposed into public sewage with little treatment. Studies show that existing wastewater treatment plants are not able to completely remove pharmaceuticals and pathogens.
Advanced Oxidation Processes (AOPs) have emerged as a suitable route for oxidation of organic contaminants and microorganism elimination. AOPs involve the generation of highly reactive species, the hydroxyl radicals (HO•). HO• are powerful non-selective oxidants and they gather several technologies such as ultraviolet irradiation (UV), ozonation, Fenton reagent, ultrasound and photocatalysis.
Despite the fact that numerous studies demonstrated that UV-driven treatments are effective in microorganisms and chemicals’ elimination, there are major barriers to the application of AOPs for the treatment of industrial wastewaters. Firstly, conventional UV-driven applications use mercury lamps. Several drawbacks are associated with these lamps: overheating, high energy consumption, short lifetime and end of life disposal issues since mercury is a hazardous pollutant. In this context, the quest for alternative cost-effective and efficient UV irradiation sources is ongoing. Secondly, wastewater treatment employing ozone is costly to break into the wastewater treatment market, which is related to the inefficiency of current designs of gas-liquid contacting reactors.
The OsciLEDs project addresses these two technological barriers to the commercial use of UV-driven water treatment processes by combining two innovative technologies: i) a reactor with outstanding gas-liquid contacting performance and ii) UV irradiation emitted by suspended light emitting diodes.
The development of LED technology has opened the possibility of employing LEDs as novel UV irradiation sources in photoreactors. LEDs offer significant advantages over traditional UV lamps such as high electrical efficiency, lower power requirement, compactness and robustness, much longer lifetime and construction of reactors with variable geometries. Hence, UV-LEDs are emerging as new photochemical light sources for water and wastewater remediation. However, until now LED systems cannot be used in a suspended liquid system.
The results obtained along the project reveal a cost-efficient UV LED-driven reactor for the inactivation of microorganisms and removal of pollutants from water, with particular focus on the removal of pharmaceuticals, comparatively to conventional reactors.
