UV-LED 101: Fundamentals and applications of UV-LEDs in water treatment

Ultraviolet (UV) light irradiation has been recommended by the USEPA as an alternative to chemical disinfectants for water disinfection because of several advantages, including effective inactivation of chlorine-resistant pathogens, negligible formation of disinfection byproducts and ease of being retrofitted into existing treatment units (Pirnie et al. 2006). UV irradiation also has been used for direct photo-degradation (direct photolysis) of emerging micropollutants (Kim and Tanaka 2009, Stefan and Bolton 2002). It also is used to activate oxidant precursors, including hydrogen peroxide (H2 O2 ), persulfate (S2 O8 2-)/peroxymonosulfate (HSO5 - ), and chlorine (HOCl/OCl- ), to produce reactive radical species for the degradation (indirect photolysis) of emerging micropollutants (Cater et al. 2000, Patton et al. 2016). The global market for UV disinfection installations/devices is estimated to reach 2.8 billion USD by 2020 (Allied Analytics LLP, 2014). Meanwhile, more and more UV-based advanced oxidation processes (e.g., UV/H2 O2 and UV/chlorine) have been incorporated into the treatment trains in advanced drinking water production facilities and for advanced wastewater treatment targeting (in)direct potable water reuse.