Sunlight driven photolytic ozonation as an advanced oxidation process in the oxidation of bezafibrate, cotinine and iopamidol

Characterization of cotinine degradation in a newly isolated Gram-negative strain Pseudomonas sp. JH-2

Cotinine, the primary metabolite of nicotine in the human body, is an emerging pollutant in aquatic environments. It causes environmental problems and is harmful to the health of humans and other mammals; however, the mechanisms of its biodegradation have been elucidated incompletely. In this study, a novel Gram-negative strain that could degrade and utilize cotinine as a sole carbon source was isolated from municipal wastewater samples, and its cotinine degradation characteristics and kinetics were determined. Pseudomonas sp. JH-2 was able to degrade 100 mg/L (0.56 mM) of cotinine with high efficiency within 5 days at 30 ℃, pH 7.0, and 1% NaCl. Two intermediates, 6-hydroxycotinine and 6-hydroxy-3-succinoylpyridine (HSP), were identified by high-performance liquid chromatography and liquid chromatograph mass spectrometer. The draft whole genome sequence of strain JH-2 was obtained and analyzed to determine genomic structure and function. No homologs of proteins predicted in Nocardioides sp. JQ2195 and reported in nicotine degradation Pyrrolidine pathway were found in strain JH-2, suggesting new enzymes that responsible for cotinine catabolism. These findings provide meaningful insights into the biodegradation of cotinine by Gram-negative bacteria.

Guidance document on the impact of water treatment processes on residues of active substances or their metabolites in water abstracted for the production of drinking water

This guidance document provides a tiered framework for risk assessors and facilitates risk managers in making decisions concerning the approval of active substances (AS) that are chemicals in plant protection products (PPPs) and biocidal products, and authorisation of the products. Based on the approaches presented in this document, a conclusion can be drawn on the impact of water treatment processes on residues of the AS or its metabolites in surface water and/or groundwater abstracted for the production of drinking water, i.e. the formation of transformation products (TPs). This guidance enables the identification of actual public health concerns from exposure to harmful compounds generated during the processing of water for the production of drinking water, and it focuses on water treatment methods commonly used in the European Union (EU). The tiered framework determines whether residues from PPP use or residues from biocidal product use can be present in water at water abstraction locations. Approaches, including experimental methods, are described that can be used to assess whether harmful TPs may form during water treatment and, if so, how to assess the impact of exposure to these water treatment TPs (tTPs) and other residues including environmental TPs (eTPs) on human and domesticated animal health through the consumption of TPs via drinking water. The types of studies or information that would be required are described while avoiding vertebrate testing as much as possible. The framework integrates the use of weight-of-evidence and, when possible alternative (new approach) methods to avoid as far as possible the need for additional testing.

Pharmaceutical Transformation Products Formed by Ozonation-Does Degradation Occur?

The efficiency of an advanced oxidation process (AOP) using direct and indirect ozonation for the removal of pharmaceutical residues from deliberately spiked deionized water was examined. Both direct and indirect ozonation demonstrated 34% to 100% removal of the parent compounds. However, based on the products' chemical structure and toxicity, we suggest that despite using accepted and affordable ozone and radical concentrations, the six parent compounds were not fully degraded, but merely transformed into 25 new intermediate products. The transformation products (TPs) differed slightly in structure but were mostly similar to their parent compounds in their persistence, stability and toxicity; a few of the TPs were found to be even more toxic than their parent compounds. Therefore, an additional treatment is required to improve and upgrade the traditional AOP toward degradation and removal of both parent compounds and their TPs for safer release into the environment.

Oxidation of 51 micropollutants during drinking water ozonation: Formation of transformation products and their fate during biological post-filtration

Micropollutants (MP) with varying ozone-reactive moieties were spiked to lake water in the influent of a drinking water pilot plant consisting of an ozonation followed by a biological sand filtration. During ozonation, 227 transformation products (OTPs) from 39 of the spiked 51 MPs were detected after solid phase extraction by liquid chromatography high-resolution mass spectrometry (LC-HRMS/MS). Based on the MS/MS data, tentative molecular structures are proposed. Reaction mechanisms for the formation of a large number of OTPs are suggested by combination of the kinetics of formation and abatement and state-of-the-art knowledge on ozone and hydroxyl radical chemistry. OTPs forming as primary or higher generation products from the oxidation of MPs could be differentiated. However, some expected products from the reactions of ozone with activated aromatic compounds and olefins were not detected with the applied analytical procedure. 187 OTPs were present in the sand filtration in sufficiently high concentrations to elucidate their fate in this treatment step. 35 of these OTPs (19%) were abated in the sand filtration step, most likely due to biodegradation. Only 24 (13%) of the OTPs were abated more efficiently than the parent compounds, with a dependency on the functional group of the parent MPs and OTPs. Overall, this study provides evidence, that the common assumption that OTPs are easily abated in biological post-treatment is not generally valid. Nevertheless, it is unknown how the OTPs, which escaped detection, would have behaved in the biological post-treatment.

Ultrasound for the remediation of contaminated waters with persistent organic pollutants: A short review

The rising amount of persistent organic contaminants released into water reservoirs in the last years became a cause of concern for the industry, academy, and public administration, due to their bioaccumulation, mutagenicity, and photosynthesis reduction. Therefore, the search for processes that efficiently remove such contaminants became of primary importance. In this context, ultrasound (US) is one of the most promising and economically viable alternatives to degrade organic pollutants in varied environments. Whereas the use of other advanced oxidation processes (AOPs), such as Fenton and photocatalysis, has been widely reported for this purpose, only a few papers deal with ultrasound application as a possible AOP. In this review, a general overview of ultrasound is provided, covering the last twenty years. It includes fundamental aspects of ultrasound and applications, individually or combined with other AOPs, to deplete organic pollutants from various classes in an aqueous environment. Finally, the review concludes by indicating that additional research should be conducted worldwide to explore the full potential of ultrasound as a useful AOP.

Cotinine Hydroxylase CotA Initiates Biodegradation of Wastewater Micropollutant Cotinine in Nocardioides sp. Strain JQ2195

Cotinine is a stable toxic contaminant, produced as a by-product of smoking. It is of emerging concern due to its global distribution in aquatic environments. Microorganisms have the potential to degrade cotinine; however, the genetic mechanisms of this process are unknown. Nocardioides sp. strain JQ2195 is a pure-culture strain that has been reported to degrade cotinine at micropollutant concentrations. This strain utilizes cotinine as its sole carbon and nitrogen source. In this study, a 50-kb gene cluster (designated cot), involved in cotinine degradation, was predicted based on genomic and transcriptomic analyses. A novel three-component cotinine hydroxylase gene (designated cotA1A2A3), which initiated cotinine catabolism, was identified and characterized. CotA from Shinella sp. strain HZN7 was heterologously expressed and purified and was shown to convert cotinine into 6-hydroxycotinine. H₂¹⁸O-labeling and electrospray ionization-mass spectrometry (ESI-MS) analysis confirmed that the hydroxyl group incorporated into 6-hydroxycotinine was derived from water. This study provides new molecular insights into the microbial metabolism of heterocyclic chemical pollutants. IMPORTANCE In the human body, cotinine is the major metabolite of nicotine, and 10 to 15% of generated cotinine is excreted in urine. Cotinine is a structural analogue of nicotine and is much more stable than nicotine. Increased tobacco consumption has led to high environmental concentrations of cotinine, which may have detrimental effects on aquatic ecosystems and human health. Nocardioides sp. strain JQ2195 is a unique cotinine-degrading bacterium. However, the underlying genetic and biochemical foundations of cotinine degradation are still unknown. In this study, a 50-kb gene cluster (designated cot) was identified by genomic and transcriptomic analyses as being involved in the degradation of cotinine. A novel three-component cotinine hydroxylase gene (designated cotA1A2A3) catalyzed cotinine to 6-hydroxy-cotinine. This study provides new molecular insights into the microbial degradation and enzymatic transformation of cotinine.

Comprehensive review on iodinated X-ray contrast media: Complete fate, occurrence, and formation of disinfection byproducts

Iodinated contrast media (ICM) are drugs which are used in medical examinations for organ imaging purposes. Wastewater treatment plants (WWTPs) have shown incapability to remove ICM, and as a consequence, ICM and their transformation products (TPs) have been detected in environmental waters. ICM show limited biotransformation and low sorption potential. ICM can act as iodine source and can react with commonly used disinfectants such as chlorine in presence of organic matter to yield iodinated disinfection byproducts (IDBPs) which are more cytotoxic and genotoxic than conventionally known disinfection byproducts (DBPs). Even highly efficient advanced treatment systems have failed to completely mineralize ICM, and TPs that are more toxic than parent ICM are produced. This raises issues regarding the efficacy of existing treatment technologies and serious concern over disinfection of ICM containing waters. Realizing this, the current review aims to capture the attention of scientific community on areas of less focus. The review features in depth knowledge regarding complete environmental fate of ICM along with their existing treatment options.

Scrutinizing the vital role of various ultraviolet irradiations on the comparative photocatalytic ozonation of albendazole and metronidazole: Integration and synergistic reactions mechanism

Herein, TiO₂ nanoparticles were immobilized on the ceramic surface using the sol-gel dip-coating method, which confirmed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Then, a semi-batch reactor containing the prepared ceramic plates, which irradiated by the various UV lights was used for the degradation of the albendazole (ALZ) and metronidazole (MTZ) pharmaceuticals by the photocatalytic ozonation process. The control experiments were performed to compare the photocatalysis, ozonation, photo-ozonation and photocatalytic ozonation processes under the same operational conditions with the UV-A, UV-B and UV-C irradiations. The synergistic effect of photocatalysis and ozonation was observed; moreover, the results revealed that the UV-A/TiO₂/O₃ had the highest efficiency for the ALZ and MTZ degradation owing to the synergistic heterogeneous reactions (SHRs), which led to more reactive oxygen species (ROS). The MTZ and ALZ degradation were probed by monitoring the dissolved ozone, oxygen and hydrogen peroxide concentrations during the various processes including the UV-A/TiO₂/O₃ process. The obtained results disclose that the ALZ degradation is lower than the MTZ due to its resistant nature with more direct attacks of the ozone in the bulk solution compared to the MTZ. Furthermore, the various compounds as the holes (h⁺) and ROS scavengers or ozone solubility enhancers were added to the reaction bulk to investigate the exact mechanism of the photocatalytic-ozonation. Eventually, the degradation intermediates of the pharmaceuticals generated in the photocatalytic-ozonation process were successfully recognized by the Gas chromatography-mass spectrometry (GC-MS) and the possible degradation paths were suggested for the degradation of pollutants considering the responsible ROS in each case.

Mechanism and stability of an Fe-based 2D MOF during the photoelectro-Fenton treatment of organic micropollutants under UVA and visible light irradiation

This work reports the novel application of an Fe-based 2D metal-organic framework (MOF), prepared with 2,2'-bipyridine-5,5'-dicarboxylate (bpydc) as organic linker, as highly active catalyst for heterogeneous photoelectro-Fenton (PEF) treatment of the lipid regulator bezafibrate in a model matrix and urban wastewater. Well-dispersed 2D structures were successfully synthesized and their morphological, physicochemical and photocatalytic properties were assessed. UV/Vis PEF using an IrO₂/air-diffusion cell with an extremely low catalyst concentration (0.05 g L^-1, tenfold lower than reported 3D MOFs) outperformed electro-oxidation with electrogenerated H₂O₂, electro-Fenton and visible-light PEF. Its excellent performance was explained by: (i) the enhanced mass transport of H₂O₂ (and organic molecules) at the 2D structure, providing active sites for heterogeneous Fenton's reaction and in-situ Fe(II) regeneration; (ii) the ability of photoinduced electrons to reduce H₂O₂ to ^•OH, and Fe(III) to Fe(II); and (iii) the enhanced charge transfer and excitation of Fe-O clusters, which increased the number of electron-hole pairs. LC-QToF-MS and GC-MS allowed the identification of 16 aromatic products of bezafibrate. The complete removal of four micropollutants mixed in urban wastewater at pH 7.4 revealed the great potential of (Fe-bpydc)-catalyzed PEF process.

Superfast degradation of refractory organic contaminants by ozone activated with thiosulfate: Efficiency and mechanisms

Thiosulfate (S₂O₃^2-) is frequently used as an ozone (O₃) quenching agent when investigating the ozonation of organic contaminants and the kinetics thereof. In this study, however, O₃ is activated by S₂O₃^2-, resulting in a superfast degradation of O₃-refractory contaminants. Therefore, the focus of this study is the exploration into the enhancing role of S₂O₃^2- in the degradation of refractory organic contaminants by O₃, which has been overlooked thus far. Results obtained from scavenging experiments and electron paramagnetic resonance (EPR) spectra verify that ^•OH generated from the reaction of S₂O₃^2- with O₃ is mainly responsible for the superfast degradation of O₃-refractory contaminants. The ^•OH yield from the O₃/S₂O₃^2- process is determined to be 0.216. A plausible mechanism for the generation of ^•OH from the O₃/S₂O₃^2- process is proposed with the implementation of density functional theory (DFT). Initially, ozone reacts with a sulfur of S₂O₃^2- to form OOOSSO₃^2-. The adduct then rearranges to OO(O)SSO₃^2- or HOO(O)SSO₃^2- in the presence of H⁺, which cleaves to give a sulfoxide radical cation and O₂^•-/HO₂^•. O₂^•-/HO₂^• is rapidly transformed into ^•OH by O₃ through a series of steps. Degradation efficiency of O₃-refractory contaminants of this process highly depends on the molar ratio of S₂O₃^2- and O₃ ([S₂O₃^2-]:[O₃]). The optimal [S₂O₃^2-]:[O₃] is pH dependent in synthetic water (e.g. 0.3 at pH 7). The presence of bicarbonate inhibits the degradation of refractory contaminants by the O₃/S₂O₃^2- process. Humic acid exhibits a slight enhancing effect at low concentrations (0.1-0.2 mg-C/L), and an inhibiting effect at higher concentrations (≥0.4 mg-C/L). In addition, the efficacy of the O₃/S₂O₃^2- process in real water matrices is also confirmed.

Trace amounts of fenofibrate acid sensitize the photodegradation of bezafibrate in effluents: Mechanisms, degradation pathways, and toxicity evaluation

Effluent organic matter (EfOM), which is composed of background natural organic matter (NOM), soluble microbial degradation products, and trace amounts of organic pollutants, can play an important role in the photodegradation of emerging pollutants in the effluent. In this study, the impact of organic pollutants, using fenofibrate acid (FNFA) as a representative, on the photodegradation of emerging contaminants, using bezafibrate (BZF) as a representative, in effluents was investigated. It is found that BZF undergo fast degradation in the presence of FNFA although BZF is recalcitrant to degradation under simulated sunlight irradiation. The promotional effect of FNFA is due to the generation of singlet oxygen (¹O₂) and hydrated electrons (e^-_aq). Based on the structures of the identified intermediates, ¹O₂ initiated oxidation and e^-_aq initiated reduction reactions were the main photodegradation pathways of BZF in the effluents. The toxicity of the main photodegradation intermediates for BZF and FNFA was higher than that of the parent compounds, and the acute toxicity increased during simulated sunlight irradiation. The results demonstrated that trace amounts of organic compounds in EfOM can play an important role in sensitizing the photodegradation of some emerging pollutants in the effluent.

Optimization of the Electro-Peroxone Process for Micropollutant Abatement Using Chemical Kinetic Approaches

The electro-peroxone (E-peroxone) process is an emerging electrocatalytic ozonation process that is enabled by in situ producing hydrogen peroxide (H₂O₂) from cathodic oxygen reduction during ozonation. The in situ-generated H₂O₂ can then promote ozone (O₃) transformation to hydroxyl radicals (•OH), and thus enhance the abatement of ozone-refractory pollutants compared to conventional ozonation. In this study, a chemical kinetic model was employed to simulate micropollutant abatement during the E-peroxone treatment of various water matrices (surface water, secondary wastewater effluent, and groundwater). Results show that by following the O₃ and •OH exposures during the E-peroxone process, the abatement kinetics of a variety of model micropollutants could be well predicted using the model. In addition, the effect of specific ozone doses on micropollutant abatement efficiencies could be quantitatively evaluated using the model. Therefore, the chemical kinetic model can be used to reveal important information for the design and optimization of the treatment time and ozone doses of the E-peroxone process for cost-effective micropollutant abatement in water and wastewater treatment.