Comparison of UV-LEDs and LPUV on inactivation and subsequent reactivation of waterborne fungal spores

Near-Ultraviolet Light-Driven Photocatalytic Chlorine Activation Process with Novel Chlorine Activation Mechanisms

“…The low EE/Os of the UV 365 /TiO 2 /chlorine process are due to the efficient radical production from the chlorine activation by h vb + and e cb – and the use of UV 365 -LED. The mercury-free UV 365 -LED with a longer lifetime is much more environmentally friendly compared with the fragile UV lamps containing hazardous mercury . It is also expected to be even more energy-saving with the further improvement of their wall-plug efficiency.…”

A Novel UVA/ClO2 Advanced Oxidation Process for the Degradation of Micropollutants in Water

“…ClO 2 is known as an alternative disinfectant/oxidant to chlorine and chloramine in water treatment practices. , The UV photolysis of ClO 2 produces a spectrum of reactive species [e.g., chlorine oxide radicals (ClO • ), chlorine radicals (Cl • ), hydroxyl radicals (HO • ), and ozone; generation mechanisms of these reactive species are provided in Text S1]. − These reactive species are produced in different AOPs and are known to degrade micropollutants in water, implying that the combination of UV irradiation and ClO 2 can function as an AOP (i.e., the UV/ClO 2 AOP) for water treatment and reuse. ,,, Attempts have been made to evaluate micropollutant degradation by the UV/ClO 2 AOP using low-pressure mercury ultraviolet (LPUV) lamps as the radiation sources at a wavelength of 254 nm (hereafter referred to the UVC 254 /ClO 2 AOP). ,, The investigations reported in the literature demonstrated that the UVC 254 /ClO 2 AOP generated reactive species (e.g., HO • and Cl • ) to enable the degradation of several micropollutants (e.g., sulfamethoxazole, triclosan, and ciprofloxacin) in water, but was less effective than the well-documented UVC 254 /H 2 O 2 , UVC 254 /chlorine, and UVC 254 /monochloramine AOPs in degrading micropollutants under the comparable conditions (e.g., same initial oxidant dosages). ,, The UVC 254 /ClO 2 AOP also has several limitations: (1) the low concentrations of reactive species generated from UVC photolysis of ClO 2 due to the low absorption of ClO 2 in the UVC range (e.g., 60.7 M –1 cm –1 at 254 nm) and the strong scavenging effects of ClO 2 itself and chlorite (one of the products of ClO 2 photodecay) on radicals; , (2) the low energy efficiency of LPUV lamps, for example, the wall plug efficiency (the energy conversion efficiency with which the system converts electrical power into optical power) of LPUV lamps is only 30–35%; and (3) the emitted photons can be easily absorbed by background matrix components (e.g., dissolved organic matter, metal oxides, and nitrate) in water and wastewater. − …”

“…12,18,19 The investigations reported in the literature demonstrated that the UVC 254 /ClO reactive species (e.g., HO • and Cl • ) to enable the degradation of several micropollutants (e.g., sulfamethoxazole, triclosan, and ciprofloxacin) in water, 12 but was less effective than the well-documented UVC 254 /H 2 O 2 , UVC 254 /chlorine, and UVC 254 /monochloramine AOPs in degrading micropollutants under the comparable conditions (e.g., same initial oxidant dosages). 3,12,18 The UVC 254 /ClO 2 AOP also has several limitations: (1) the low concentrations of reactive species generated from UVC photolysis of ClO 2 due to the low absorption of ClO 2 in the UVC range (e.g., 60.7 M −1 cm −1 at 254 nm) and the strong scavenging effects of ClO 2 itself and chlorite (one of the products of ClO 2 photodecay) on radicals; 20,21 (2) the low energy efficiency of LPUV lamps, for example, the wall plug efficiency (the energy conversion efficiency with which the system converts electrical power into optical power) 22 of LPUV lamps is only 30−35%; 23 and (3) the emitted photons can be easily absorbed by background matrix components (e.g., dissolved organic matter, metal oxides, and nitrate) in water and wastewater. 24−26 ClO 2 has high absorption coefficients (619.1−1284.2 M −1 cm −1 ) in the UVA range (320−400 nm), with an absorption peak at 360 nm (ClO 2 absorption spectrum provided in Figure S1).…”

Retention and Inactivation of Quality Indicator Bacteria Using a Photocatalytic Membrane Reactor

“…Some studies reported the use of different LED wavelengths for the inactivation of microorganisms in water [4,8,9,11,[17][18][19]. The choice of wavelength differs according to the purpose.…”