Electrochemical Plasma for Treating 2,4,5-Trichlorophenoxyacetic Acid in a Water Environment Using Iron Electrodes.

Herbicide compounds containing aromatic rings and chlorine atoms, such as 2,4,5-trichlorophenoxyacetic (2,4,5-T), cause serious environmental pollution. Furthermore, these compounds are very difficult to decompose by chemical, physical, and biological techniques. Fortunately, the high-voltage direct current electrochemical technique can be controlled to form a plasma on metallic electrodes. It creates active species, such as H2, O2, and H2O2, and free radicals, such as H•, O•, and OH•. Free radicals that have a high oxidation potential (e.g., OH•) are highly effective in oxidizing benzene-oring compounds. Iron electrodes are used in the study to combine the dissolving process of the iron anode electrode to create Fe2+ ions and the electrochemical Fenton reaction. In addition, the flocculation process by Fe(OH)2 also occurs and the plasma appears with a voltage of 5 kV on the iron electrode in a solution of 30 mg L-1 of 2,4,5-T. After a period of time of the reaction, the aromatic-oring compounds containing chlorine were effectively treated, and the electric conductivity of the solution increased due to the amount of Cl- ions released in the solution and the decrease in the pH value. The degradable products of 2,4,5-T were qualitatively characterized by gas chromatography-mass spectrometry (GC-MS), and it was determined that straight-chain carboxylic acids are formed in the solution. These compounds are easy to oxidize thoroughly under appropriate conditions in a solution via OH• free radicals. Moreover, 2,4,5-T was also quantitatively analyzed using a calibration curve from GC-MS and high-performance liquid chromatography (HPLC). Furthermore, this work also suggests that the performance of the treatment process can be optimized by controlling the technological factors, such as the input voltage, the distance between anodic and cathodic electrodes, the initial concentration of 2,4,5-T, and flowing air through the solution that represents an approximately 99.83% degradable efficiency. Finally, the work demonstrates a potential technology for treating the 2,4,5-T compound, particularly for environmental pollution treatments.

The Ecological Dynamics of Fecal Contamination and Salmonella Typhi and Salmonella Paratyphi A in Municipal Kathmandu Drinking Water.

One of the UN sustainable development goals is to achieve universal access to safe and affordable drinking water by 2030. It is locations like Kathmandu, Nepal, a densely populated city in South Asia with endemic typhoid fever, where this goal is most pertinent. Aiming to understand the public health implications of water quality in Kathmandu we subjected weekly water samples from 10 sources for one year to a range of chemical and bacteriological analyses. We additionally aimed to detect the etiological agents of typhoid fever and longitudinally assess microbial diversity by 16S rRNA gene surveying. We found that the majority of water sources exhibited chemical and bacterial contamination exceeding WHO guidelines. Further analysis of the chemical and bacterial data indicated site-specific pollution, symptomatic of highly localized fecal contamination. Rainfall was found to be a key driver of this fecal contamination, correlating with nitrates and evidence of S. Typhi and S. Paratyphi A, for which DNA was detectable in 333 (77%) and 303 (70%) of 432 water samples, respectively. 16S rRNA gene surveying outlined a spectrum of fecal bacteria in the contaminated water, forming complex communities again displaying location-specific temporal signatures. Our data signify that the municipal water in Kathmandu is a predominant vehicle for the transmission of S. Typhi and S. Paratyphi A. This study represents the first extensive spatiotemporal investigation of water pollution in an endemic typhoid fever setting and implicates highly localized human waste as the major contributor to poor water quality in the Kathmandu Valley.