Chlorite (ClO) is a regulated byproduct of chlorine dioxide water treatment processes. The transformation of chlorite under UV irradiation into chloride (Cl) and chlorate (ClO) involves reactive species chain reactions that could enhance chlorine dioxide water treatment efficiency while reducing residual chlorite levels. This study conducted a mechanistic investigation of chlorite phototransformation by analyzing reaction intermediates and stable end products, including chlorine dioxide (ClO), free chlorine (HOCl/OCl), hydroxyl‑radical (OH), Cl, and ClO through combined experimental and modeling approaches.
View Article and Find Full Text PDFAdvanced oxidation processes (AOPs) are a growing research field with a large variety of different process variants and materials being tested at laboratory scale. However, despite extensive research in recent years and decades, many variants have not been transitioned to pilot- and full-scale operation. One major concern are the inconsistent experimental approaches applied across different studies that impede identification, comparison, and upscaling of the most promising AOPs.
View Article and Find Full Text PDFThe absolute radical quantum yield () is a critical parameter to evaluate the efficiency of radical-based processes in engineered water treatment. However, measuring is fraught with challenges, as current quantification methods lack selectivity, specificity, and anti-interference capabilities, resulting in significant error propagation. Herein, we report a direct and reliable time-resolved technique to determine at pH 7.
View Article and Find Full Text PDFFree-living (FL) and particulate-associated (PA) communities are distinct bacterioplankton lifestyles with different mobility and dissemination routes. Understanding spatio-temporal dynamics of PA and FL fractions will allow improvement to wastewater treatment processes including pathogen and AMR bacteria removal. In this study, PA, FL and sediment community composition and antimicrobial resistance gene (ARG; tetW, ermB, sul1, intI1) dynamics were investigated in a full-scale municipal wastewater free-water surface polishing constructed wetland.
View Article and Find Full Text PDFThe combination of urbanization and global warming leads to urban overheating and compounds the frequency and intensity of extreme heat events due to climate change. Yet, the risk of urban overheating can be mitigated by urban green-blue-grey infrastructure (GBGI), such as parks, wetlands, and engineered greening, which have the potential to effectively reduce summer air temperatures. Despite many reviews, the evidence bases on quantified GBGI cooling benefits remains partial and the practical recommendations for implementation are unclear.
View Article and Find Full Text PDFMicroplastics in wastewater are colonized by biofilms containing pathogens and antimicrobial resistance (AMR) genes that can be exported into receiving water bodies. This study investigated establishment and changes in microplastic-associated biofilm and AMR during a conventional full-scale 2100 population equivalent wastewater treatment process combined with a free water surface polishing constructed wetland. Sequential microplastic colonization experiments were conducted at different stages of the wastewater treatment process, including in raw sewage, treated effluent and the constructed wetland.
View Article and Find Full Text PDFZnO is a widely studied photocatalyst, but practical use is hindered by its low resistance to photocorrosion in water, which leads to metal leaching and loss of performance over time. In this work, highly porous and mechanically stable ZnO foams, called MolFoams, were doped by adding 1% or 2% Co, Ni or Cu salts to the starting Zn salt, followed by air insufflation during a sol-gel rection and sintering. The resulting doped foams showed a major increase in stability, with a 60-85% reduction in Zn leaching after irradiation, albeit with a reduction in photocatalytic activity.
View Article and Find Full Text PDFThis study investigates microplastic (MPs) dynamics of a recently established surface flow 2100 population equivalent polishing constructed wetland (CW) receiving 1.4 ML per day of secondary treated wastewater. MPs type, size ranges and concentrations were measured along the CW at a 2-months sampling campaign.
View Article and Find Full Text PDFMembrane ozonation of bromide-containing, high-color natural organic matter (NOM) containing groundwater was performed using single-tube polydimethylsiloxane (PDMS) and multi-tube polytetrafluoroethylene (PTFE) membrane contactors, and compared to batch ozonation. For membrane ozonation, dissolved ozone concentration, water color (VIS), ultraviolet light absorption (UV) and bromate formation were correlated with ozone dose, ozone gas concentration, hydraulic retention time and Hatta number (Ha). NOM color removal of up to 45 % for the single-tube contactor and 17 % for the multi-tube contactor were achieved while containing bromate formation below 10 µg L.
View Article and Find Full Text PDFGraphitic carbon nitride (g-CN) is known to photogenerate hydrogen peroxide in the presence of hole quenchers in aqueous environments. Here, the g-CN photocatalyst is embedded into a host polymer of intrinsic microporosity (PIM-1) to provide recoverable heterogenized photocatalysts without loss of activity. Different types of g-CN (including Pt@g-CN, Pd@g-CN, and Au@g-CN) and different quenchers are investigated.
View Article and Find Full Text PDFAcclimation and flexible response mechanisms are survival adaptations allowing prokaryotic cells to colonize diverse habitats and maintain viability in nature. Lack of water significantly impacts cellular response, which can be partially compensated for through community interactions and accessing survival means beyond the cell's boundaries. In the present study, higher numbers of cultivable Gram-positive Arthrobacter sp.
View Article and Find Full Text PDFPhage bacteria interactions can affect structure, dynamics, and function of microbial communities. In the context of biological wastewater treatment (BWT), the presence of phages can alter the efficiency of the treatment process and influence the quality of the treated effluent. The active role of phages in BWT has been demonstrated, but many questions remain unanswered regarding the diversity of phages in these engineered environments, the dynamics of infection, the determination of bacterial hosts, and the impact of their activity in full-scale processes.
View Article and Find Full Text PDFDissolved organic matter (DOM) has a dual role in indirect phototransformations of aquatic contaminants by acting both as a photosensitizer and an inhibitor. Herein, the pH dependence of the inhibitory effect of DOM and the underlying mechanisms were studied in more than 400 kinetic irradiation experiments over the pH range of 6-11. Experiments employed various combinations of one of three DOM isolates, one of two model photosensitizers, the model antioxidant phenol, and one of nine target compounds (TCs), comprising several aromatic amines, in particular anilines and sulfonamides, and 4-cyanophenol.
View Article and Find Full Text PDFAzuFluor® 435-DPA-Zn, an azulene fluorophore bearing two zinc(II)-dipicolylamine receptor motifs, exhibits fluorescence enhancement in the presence of adenosine diphosphate. Selectivity for ADP over ATP, AMP and PPi results from appropriate positioning of the receptor motifs, since an isomeric sensor cannot discriminate between ADP and ATP.
View Article and Find Full Text PDFDespite the widespread occurrence of furan moieties in synthetic and natural compounds, their fate in aqueous ozonation has not been investigated in detail. Reaction rate constants of seven commonly used furans with ozone were measured and ranged from k = 8.5 × 10 to 3.
View Article and Find Full Text PDFAzulene is a bicyclic aromatic chromophore that absorbs in the visible region. Its absorption maximum undergoes a hypsochromic shift if a conjugated electron-withdrawing group is introduced at the C1 position. This fact can be exploited in the design of a colorimetric chemodosimeter that functions by the transformation of a dithioacetal to the corresponding aldehyde upon exposure to Hg2+ ions.
View Article and Find Full Text PDFColorimetry is an advantageous method for detecting fluoride in drinking water in a resource-limited context, e. g., in parts of the developing world where excess fluoride intake leads to harmful health effects.
View Article and Find Full Text PDFTwo-photon fluorescence microscopy has become an indispensable technique for cellular imaging. Whereas most two-photon fluorescent probes rely on well-known fluorophores, here we report a new fluorophore for bioimaging, namely azulene. A chemodosimeter, comprising a boronate ester receptor motif conjugated to an appropriately substituted azulene, is shown to be an effective two-photon fluorescent probe for reactive oxygen species, showing good cell penetration, high selectivity for peroxynitrite, no cytotoxicity, and excellent photostability.
View Article and Find Full Text PDFZinc oxide (ZnO) displays superior properties as a photocatalyst, compared to the more widely used TiO. However, widespread application of ZnO is hampered by its high photo-corrosion in aqueous environments under UV irradiation. A systematic investigation of the effect of (i) post-production annealing, (ii) dissolved oxygen levels during photocatalysis and (iii) reactor configuration on the stability and photocatalytic activity (PCA) of ZnO nanowires, grown on either flat or circular supports, was conducted.
View Article and Find Full Text PDFDissolved organic matter (DOM) is a natural photosensitizer that contributes to the inactivation of microbial pathogens. In constructed treatment wetlands with open water areas DOM can promote sunlight disinfection of wastewater effluent, but a better understanding of DOM spectroscopic and photochemical properties and how they are impacted by different unit process wetlands is needed to inform design. The goals of this study were: (1) to investigate whether DOM isolates realistically represent the photochemistry of the source DOM in its original water and (2) to observe how changes of DOM along a treatment wetland affect its photochemistry, including pathogen inactivation.
View Article and Find Full Text PDFAs water scarcity intensifies, point-of-use and point-of-entry treatment may provide a means of exploiting locally available water resources that are currently considered to be unsafe for human consumption. Among the different classes of drinking water contaminants, toxic trace elements (e.g.
View Article and Find Full Text PDFLow cost and in situ fluoride detection by non-experts is important for the determination of drinking water safety in developing countries. Colour reagents can provide results quickly without expensive equipment, but colorimetric fluoride indicators are often nonspecific, complex to use or do not work in water. Here we show that azulene-boronate indicators respond selectively to fluoride at concentrations relevant to the WHO limit of 1.
View Article and Find Full Text PDFIt is presently unknown to what extent the endogenous direct, endogenous indirect, and exogenous indirect mechanisms contribute to bacterial photoinactivation in natural surface waters. In this study, we investigated the importance of the exogenous indirect mechanism by conducting photoinactivation experiments with eight health-relevant bacterial species (Bacteroides thetaiotaomicron, Campylobacter jejuni, Enterococcus faecalis, Escherichia coli K12, E. coli O157:H7, Salmonella enterica serovar Typhimurium LT2, Staphylococcus aureus, and Streptococcus bovis).
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