Insight into the generation of toxic by-products during UV/H2O2 degradation of carbamazepine: Mechanisms, N-transformation and toxicity.

Carbamazepine (CBZ) is a widely used anticonvulsant drug that has been detected in aquatic environments. This study investigated the toxicity of its by-products (CBZ-BPs), which may surpass CBZ. Unlike the previous studies, this study offered a more systematic approach to identifying toxic BPs and inferring degradation pathways. Furthermore, quadrupole time-of-flight (QTOF) and density functional theory (DFT) calculations were employed to analyze CBZ-BP structures and degradation pathways. Evaluation of total organic carbon (TOC) and total nitrogen (TN) mineralization rates, revealed carbon (C) greater susceptibility to mineralization compared with nitrogen (N). Furthermore, three rules were established for CBZ decarbonization and N removal during degradation, observing the transformation of aromatic compounds into aliphatic hydrocarbons and stable N-containing organic matter over time. Five potentially highly toxic BPs were screened from 14 identified BPs, with toxicity predictions guiding the selection of commercial standards for quantification and true toxicity testing. Additionally, BP207 emerged as the most toxic, supported by the predictive toxicity accumulation model (PTAM). Notably, highly toxic BPs feature an acridine structure, indicating its significant contribution to toxicity. These findings offered valuable insights into the degradation mechanisms of emerging contaminants and the biosafety of aquatic environments during deep oxidation.

Synergistic nanowire-assisted electroporation and chlorination for inactivation of chlorine-resistant bacteria in drinking water systems via inducing cell pores for chlorine permeation.

The widespread use of chlorination (Cl2) in drinking water systems causes the selection of chlorine-resistant bacteria commonly with dense extracellular polymeric substance (EPS) against chlorine permeation, posing significant threat to public health. Herein, a nanowire-assisted electroporation (EP) via locally enhanced electric field was combined with Cl2 to construct the synergistic EP/Cl2 disinfection, with the purposes of inducing cell pores for chlorine permeation and bacterial inactivation. The synergistic effects of EP/Cl2 were observed for inactivation of chlorine-resistant Bacillus cereus (G+, 304 µg DOC-EPS/109 CFU) and Aeromonas media (G-, 35.8 µg), and chlorine-sensitive Escherichia coli (G-, 5.1 µg) that were frequent occurrence in drinking water systems. The EP/Cl2 enabled above 6 log B. cereus inactivation (undetectable live bacteria) at 1.5 V-EP and 0.9 mg/L-Cl2, which was much higher than the individual EP (1.11 log) and Cl2 (1.13 log) disinfection. The cell membrane integrity, intracellular free chlorine levels, and morphology analyses revealed that the electroporation-induced pores on cell wall/membrane destructed the bound EPS barrier for chlorine permeation, and the pore sizes were further enlarged by chlorine oxidation, hence facilitating bacterial inactivation via destroying the cell structures. The excellent disinfection performance for tap water and lake water also suggested its sound application potentials.