Water Disinfection with Dual-Wavelength (222 + 275 nm) Ultraviolet Radiations: Microbial Inactivation and Reactivation.

Emerging mercury-free ultraviolet (UV) sources, such as krypton chloride excimer (KrCl*) lamps and UV light emitting diodes (UV-LEDs), emit diverse wavelengths with distinct inactivation mechanisms. The combined application has the potential to improve disinfection effectiveness through synergism. In this study, a mini-fluidic photoreaction system equipped with a KrCl* lamp (222 nm) and a strip of UV-LEDs (275 nm) was developed, which could individually/simultaneously deliver accurate UV radiation(s) at 222 nm (0.

Advancing illicit connection diagnosis of urban stormwater pipes: Comprehensive analysis with EEM fluorescence spectroscopy.

Urban drainage systems are significant contributors to the issue of black-odorous water bodies. The current application of stormwater pipe inspection technologies faces substantial limitations, especially in industrial areas with diverse wastewater. This study introduced an innovative approach using excitation-emission matrix (EEM) fluorescence spectroscopy for rapid and accurate diagnosis, providing a new perspective for diagnosing illicit connections.

Accelerated transformation of sodium dodecylbenzene sulfonate surfactant in the UV/chlorine process: Kinetics and formation of chlorinated disinfection by-products.

The degradation kinetics of Sodium dodecylbenzene sulfonate (SDBS) surfactant in the UV/chlorine process was comprehensively investigated, and the formation of chlorinated disinfection by-products (Cl-DBPs) were determined. Results showed that the degradation of SDBS by UV, chlorine and UV/chlorine all followed pseudo-first-order kinetics. The rate constant by UV/chlorine in ultrapure water was approximately 3 times higher than the sum of those by UV and chlorine, and decreased from 0.

Formation control of bromate and trihalomethanes during ozonation of bromide-containing water with chemical addition: Hydrogen peroxide or ammonia?

To ensure the safety of drinking water, ozone (O) has been extensively applied in drinking water treatment plants to further remove natural organic matter (NOM). However, the surface water and groundwater near the coastal areas often contain high concentrations of bromide ion (Br). Considering the risk of bromate (BrO) formation in ozonation of the sand-filtered water, the inhibitory efficiencies of hydrogen peroxide (HO) and ammonia (NH) on BrO formation during ozonation process were compared.

Dimethoate degradation by VUV/UV process: Kinetics, mechanism and economic feasibility.

Vacuum ultraviolet/ultraviolet (VUV/UV) process has been applied to water treatment recently, but little is known about its efficacy and mechanism for pesticide degradation. This study investigated the degradation kinetics and mechanism of a typical organophosphorus pesticide, dimethoate (DMT) by VUV/UV, and then the economic feasibility was assessed. DMT degradation followed well the pseudo-first-order reaction kinetics at an initial concentration of ≤5.

Reduction of bromate by zero valent iron (ZVI) enhances formation of brominated disinfection by-products during chlorination.

Bromate (BrO) is a predominant undesired toxic disinfection by-product (DBP) during ozonation of bromide-containing waters. The reduction of BrO by zero valent iron (ZVI) and its effect on formation of organic halogenated DBPs during chlorination were investigated in this study. The presence of ZVI could reduce BrO to bromide (Br), and Br formed could be transformed to free bromine (HOBr/OBr) during chlorination, further leading to organic brominated (Br-) DBPs formation.

Organic Amines Enhance the Formation of Iodinated Trihalomethanes during Chlorination of Iodide-Containing Waters.

The effects of organic amines (OAs) including glycine (Gly), sarcosine (Sar), and triethanolamine (Tea), representing primary, secondary, and tertiary amines, respectively, on iodinated trihalomethanes (I-THMs) formation during chlorination of iodide (I)-containing waters were investigated. The total concentration of I-THMs formed in the co-presence of an OA and natural organic matter (NOM) was more than 3 times the sum of those formed in the presence of an OA alone and NOM alone, as OAs competed for free chlorine (FC) to form organic chloramines. Taking Gly as an example, the transformation of I was determined.

Accelerated degradation of sulfamethazine in water by VUV/UV photo-Fenton process: Impact of sulfamethazine concentration on reaction mechanism.

The degradation of sulfamethazine (SMN) by VUV/UV photo-Fenton (VPF) process was investigated with a mini-fluidic VUV/UV photoreaction system. Compared with the conventional UV photo-Fenton process, the VPF process significantly enhanced the degradation and mineralization of SMN, because the VUV irradiation photolyzed HO and accelerated the redox cycle of Fe/Fe to generate more reactive oxygen species (ROS). Initial pH and concentrations of SMN, HO, Fe, inorganic anions (NO, HCO, and Cl), and humic acid all considerably impacted SMN degradation in the VPF process.