Removal of the antiviral agent oseltamivir and its biological activity by oxidative processes

Assessing the impact of antiviral drugs commonly utilized during the COVID-19 pandemic on the embryonic development of Xenopus laevis

The antiviral drugs favipiravir and oseltamivir are widely used to treat viral infections, including coronavirus 2019 (COVID-19), and their levels are expected to increase in the aquatic environment. In this study, the potential toxic and teratogenic effects of these drugs were evaluated using the frog embryo teratogenesis assay Xenopus (FETAX). In addition, glutathione S-transferase (GST), glutathione reductase (GR), catalase, carboxylesterase (CaE), and acetylcholinesterase (AChE) enzyme activities and malondialdehyde levels were measured as biochemical markers in embryos and tadpoles for comparative assessment of the sublethal effects of the test compounds. Prior to embryo exposure, drug concentrations in the exposure medium were measured with high-performance liquid chromatography. The 96-h median lethal concentration (LC50) was 137.9 and 32.3 mg/L for favipiravir and oseltamivir, respectively. The teratogenic index for favipiravir was 4.67. Both favipiravir and oseltamivir inhibited GR, CaE, and AChE activities in embryos, while favipiravir increased the GST and CaE activities in tadpoles. In conclusion, favipiravir, for which teratogenicity data are available in mammalian test organisms and human teratogenicity is controversial, inhibited Xenopus laevis embryo development and was teratogenic. In addition, sublethal concentrations of both drugs altered the biochemical responses in embryos and tadpoles, with differences between the developmental stages.

Oxidation processes and me

This publication summarizes my journey in the field of chemical oxidation processes for water treatment over the last 30+ years. Initially, the efficiency of the application of chemical oxidants for micropollutant abatement was assessed by the abatement of the target compounds only. This is controlled by reaction kinetics and therefore, second-order rate constant for these reactions are the pre-requisite to assess the efficiency and feasibility of such processes. Due to the tremendous efforts in this area, we currently have a good experimental data base for second-order rate constants for many chemical oxidants, including radicals. Based on this, predictions can be made for compounds without experimental data with Quantitative Structure Activity Relationships with Hammet/Taft constants or energies of highest occupied molecular orbitals from quantum chemical computations. Chemical oxidation in water treatment has to be economically feasible and therefore, the extent of transformation of micropollutants is often limited and mineralization of target compounds cannot be achieved under realistic conditions. The formation of transformation products from the reactions of the target compounds with chemical oxidants is inherent to oxidation processes and the following questions have evolved over the years: Are the formed transformation products biologically less active than the target compounds? Is there a new toxicity associated with transformation products? Are transformation products more biodegradable than the corresponding target compounds? In addition to the positive effects on water quality related to abatement of micropollutants, chemical oxidants react mainly with water matrix components such as the dissolved organic matter (DOM), bromide and iodide. As a matter of fact, the fraction of oxidants consumed by the DOM is typically > 99%, which makes such processes inherently inefficient. The consequences are loss of oxidation capacity and the formation of organic and inorganic disinfection byproducts also involving bromide and iodide, which can be oxidized to reactive bromine and iodine with their ensuing reactions with DOM. Overall, it has turned out in the last three decades, that chemical oxidation processes are complex to understand and to manage. However, the tremendous research efforts have led to a good understanding of the underlying processes and allow a widespread and optimized application of such processes in water treatment practice such as drinking water, municipal and industrial wastewater and water reuse systems.

Tracing COVID-19 drugs in the environment: Are we focusing on the right environmental compartment?

The Coronavirus Disease 2019 (COVID-19) pandemic led to over 770 million confirmed cases, straining public healthcare systems and necessitating extensive and prolonged use of synthetic chemical drugs around the globe for medical treatment and symptom relief. Concerns have arisen regarding the massive release of active pharmaceutical ingredients (APIs) and their metabolites into the environment, particularly through domestic sewage. While discussions surrounding this issue have primarily centered on their discharge into aquatic environments, particularly through treated effluent from municipal wastewater treatment plants (WWTPs), one often overlooked aspect is the terrestrial environment as a significant receptor of pharmaceutical-laden waste. This occurs through the disposal of sewage sludge, for instance, by applying biosolids to land or non-compliant disposal of sewage sludge, in addition to the routine disposal of expired and unused medications in municipal solid wastes. In this article, we surveyed sixteen approved pharmaceuticals for treating COVID-19 and bacterial co-infections, along with their primary metabolites. For this, we delved into their physiochemical properties, ecological toxicities, environmental persistence, and fate within municipal WWTPs. Emphasis was given on lipophilic substances with log Kow >3.0, which are more likely to be found in sewage sludge at significant factions (25.2%-75.0%) of their inputs in raw sewage and subsequently enter the terrestrial environment through land application of biosolids, e.g., 43% in the United States and as high as 96% in Ireland or non-compliant practices of sewage sludge disposal in developing communities, such as open dumping and land application without prior anaerobic digestion. The available evidence underscores the importance of adequately treating and disposing of sewage sludge before its final disposal or land application in an epidemic or pandemic scenario, as mismanaged sewage sludge could be a significant vector for releasing pharmaceutical compounds and their metabolites into the terrestrial environment.

Predicting Transformation Products during Aqueous Oxidation Processes: Current State and Outlook

Water quality and its impacts on human and ecosystem health presents tremendous global challenges. While oxidative water treatment can solve many of these problems related to hygiene and micropollutants, identifying and predicting transformation products from a large variety of micropollutants induced by dosed chemical oxidants and in situ formed radicals is still a major challenge. To this end, a better understanding of the formed transformation products and their potential toxicity is needed. Currently, no theoretical tools alone can predict oxidatively induced transformation products in aqueous systems. Coupling experimental and theoretical studies has advanced the understanding of reaction kinetics and mechanisms significantly. This perspective article highlights the key progress made concerning experimental and computational approaches to predict transformation products. Knowledge gaps are identified, and the research required to advance the predictive capability is discussed.

A sustainable approach for the removal methods and analytical determination methods of antiviral drugs from water/wastewater: A review

In the last years, antiviral drugs especially used for the treatment of COVID-19 have been considered emerging contaminants because of their continuous occurrence and persistence in water/wastewater even at low concentrations. Furthermore, as compared to antiviral drugs, their metabolites and transformation products of these pharmaceuticals are more persistent in the environment. They have been found in environmental matrices all over the world, demonstrating that conventional treatment technologies are unsuccessful for removing them from water/wastewater. Several approaches for degrading/removing antiviral drugs have been studied to avoid this contamination. In this study, the present level of knowledge on the input sources, occurrence, determination methods and, especially, the degradation and removal methods of antiviral drugs are discussed in water/wastewater. Different removal methods, such as conventional treatment methods (i.e. activated sludge), advanced oxidation processes (AOPs), adsorption, membrane processes, and combined processes, were evaluated. In addition, the antiviral drugs and these metabolites, as well as the transformation products created as a result of treatment, were examined. Future perspectives for removing antiviral drugs, their metabolites, and transformation products were also considered.

Decentralized systems for the treatment of antimicrobial compounds released from hospital aquatic wastes

In many developing countries, untreated hospital effluents are discharged and treated simultaneously with municipal wastewater. However, if the hospital effluents are not treated separately, they pose concerning health risks due to the possible transport of the antimicrobial genes and microbes in the environment. Such effluent is considered as a point source for a number of potentially infectious microorganisms, waste antimicrobial compounds and other contaminants that could promote antimicrobial resistance development. The removal of these contaminants prior to discharge reduces the exposure of antimicrobials to the environment and this should lower the risk of superbug development. At an effluent discharge site, suitable pre-treatment of wastewater containing antimicrobials could maximise the ecological impact with potentially reduced risk to human health. In addressing these points, this paper reviews the applications of decentralized treatment systems toward reducing the concentration of antimicrobials in wastewater. The most commonly used techniques in decentralized wastewater treatment systems for onsite removal of antimicrobials were discussed and evidence suggests that hybrid techniques should be more useful for the efficient removal of antimicrobials. It is concluded that alongside the cooperation of administration departments, health industries, water treatment authorities and general public, decentralized treatment technology can efficiently enhance the removal of antimicrobial compounds, thereby decreasing the concentration of contaminants released to the environment that could pose risks to human and ecological health due to development of antimicrobial resistance in microbes.

Antiviral drugs against influenza: Treatment methods, environmental risk assessment and analytical determination

Over the past few years, antiviral drugs against influenza are considered emerging contaminants since they cause environmental toxicity even at low concentrations. They have been found in environmental matrices all around the world, showing that conventional treatment methods fail to remove them from water and wastewater. In addition, the metabolites and transformation products of these drugs can be more persistent than original in the environment. Several techniques to degrade/remove antiviral drugs against influenza have been investigated to prevent this contamination. In this study, the characteristics of antiviral drugs against influenza, their measurement by analytical methods, and their removal in both water and wastewater treatment plants (WWTPs) were presented. Different treatment methods, such as traditional procedures (biological processes, filtration, coagulation, flocculation, and sedimentation), advanced oxidation processes (AOPs), adsorption and combined methods, were assessed. Ecotoxicological effects of both the antiviral drug and its metabolites as well as the transformation products formed as a result of treatment were evaluated. In addition, future perspectives for improving the removal of antiviral drugs against influenza, their metabolites and transformation products were further discussed. The research indicated that the main tested techniques in this study were ozonation, photolysis and photocatalysis. Combined methods, particularly those that use renewable energy and waste materials, appear to be the optimum approach for the treatment of effluents containing antiviral drugs against influenza. In light of high concentrations or probable antiviral resistance, this comprehensive assessment suggests that antiviral drug monitoring is required, and some of those substances may cause toxicological effects.

SARS-CoV-2 pharmaceutical drugs: a critical review on the environmental impacts, chemical characteristics, and behavior of advanced oxidation processes in water

This review summarizes research data on the pharmaceutical drugs used to treat the novel SARS-CoV-2 virus, their characteristics, environmental impacts, and the advanced oxidation processes (AOP) applied to remove them. A literature survey was conducted using the electronic databases Science Direct, Scopus, Taylor & Francis, Google Scholar, PubMed, and Springer. This complete research includes and discusses relevant studies that involve the introduction, pharmaceutical drugs used in the SARS-CoV-2 pandemic: chemical characteristics and environmental impact, advanced oxidation process (AOP), future trends and discussion, and conclusions. The results show a full approach in the versatility of AOPs as a promising solution to minimize the environmental impact associated with these compounds by the fact that they offer different ways for hydroxyl radical production. Moreover, this article focuses on introducing the fundamentals of each AOP, the main parameters involved, and the concomitance with other sources and modifications over the years. Photocatalysis, sonochemical technologies, electro-oxidation, photolysis, Fenton reaction, ozone, and sulfate radical AOP have been used to mineralize SARS-CoV-2 pharmaceutical compounds, and the efficiencies are greater than 65%. According to the results, photocatalysis is the main technology currently applied to remove these pharmaceuticals. This process has garnered attention because solar energy can be directly utilized; however, low photocatalytic efficiencies and high costs in large-scale practical applications limit its use. Furthermore, pharmaceuticals in the environment are diverse and complex. Finally, the review also provides ideas for further research needs and major concerns.

Changes in Organics and Nitrogen during Ozonation of Anaerobic Digester Effluent

The objective of this study is to investigate the consequence of ozone dosage rate on the qualitative change in organic compounds and nitrogen in anaerobic digester effluent during the ozone process. Therefore, ozonation improves the biodegradability of recalcitrant organic compounds, quickly oxidizes the unsaturated bond, and forms radicals that continue to deteriorate other organic matter. In this study, ozonation was performed in a microbubble column reactor; the use of microbubble ozone improves the status of chemical oxygen demand (COD) and changes of organic nitrogen to inorganic compounds. The ozone injection rates were 1.0, 3.2, and 6.2 mg/L/min. The samples obtained during the ozone treatments were monitored for CODMn, CODCr, TOC, NO2−-N, NO3−-N, NH4+-N, T-N, and Org-N. The ozone dose increased 1.0 to 6.2 mg/L and it increased the degradation ratio 40% and the total organic carbon 20% during 20 min of reaction time. During the ozonation, the CODCr and CODMn values were increased per unit of ozone consumption. The ozone treatment showed organic nitrogen mineralization and degradation of organic compounds with the contribution of the microbubble ozone oxidation process and is a good option for removing non-biodegradable organic compounds. The original application of the microbubble ozone process, with the degradation of organic compounds from a domestic wastewater treatment plant, was investigated.

Ozonation of organic compounds in water and wastewater: A critical review

Ozonation has been applied in water treatment for more than a century, first for disinfection, later for oxidation of inorganic and organic pollutants. In recent years, ozone has been increasingly applied for enhanced municipal wastewater treatment for ecosystem protection and for potable water reuse. These applications triggered significant research efforts on the abatement efficiency of organic contaminants and the ensuing formation of transformation products. This endeavor was accompanied by developments in analytical and computational chemistry, which allowed to improve the mechanistic understanding of ozone reactions. This critical review assesses the challenges of ozonation of impaired water qualities such as wastewaters and provides an up-to-date compilation of the recent kinetic and mechanistic findings of ozone reactions with dissolved organic matter, various functional groups (olefins, aromatic compounds, heterocyclic compounds, aliphatic nitrogen-containing compounds, sulfur-containing compounds, hydrocarbons, carbanions, β-diketones) and antibiotic resistance genes.

COVID-19 drugs in aquatic systems: a review

The outbreak of the human coronavirus disease 2019 (COVID-19) has induced an unprecedented increase in the use of several old and repurposed therapeutic drugs such as veterinary medicines, e.g. ivermectin, nonsteroidal anti-inflammatory drugs, protein and peptide therapeutics, disease-modifying anti-rheumatic drugs and antimalarial drugs, antiretrovirals, analgesics, and supporting agents, e.g. azithromycin and corticosteroids. Excretion of drugs and their metabolites in stools and urine release these drugs into wastewater, and ultimately into surface waters and groundwater systems. Here, we review the sources, behaviour, environmental fate, risks, and remediation of those drugs. We discuss drug transformation in aquatic environments and in wastewater treatment systems. Degradation mechanisms and metabolite toxicity are poorly known. Potential risks include endocrine disruption, acute and chronic toxicity, disruption of ecosystem functions and trophic interactions in aquatic organisms, and the emergence of antimicrobial resistance.

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.

Formation of transformation products during ozonation of secondary wastewater effluent and their fate in post-treatment: From laboratory- to full-scale

Ozonation is increasingly applied in water and wastewater treatment for the abatement of micropollutants (MPs). However, the transformation products formed during ozonation (OTPs) and their fate in biological or sorptive post-treatments is largely unknown. In this project, a high-throughput approach, combining laboratory ozonation experiments and detection by liquid chromatography high-resolution mass spectrometry (LC-HR-MS/MS), was developed and applied to identify OTPs formed during ozonation of wastewater effluent for a large number of relevant MPs (total 87). For the laboratory ozonation experiments, a simplified experimental solution, consisting of surrogate organic matter (methanol and acetate), was created, which produced ozonation conditions similar to realistic conditions in terms of ozone and hydroxyl radical exposures. The 87 selected parent MPs were divided into 19 mixtures, which enabled the identification of OTPs with an optimized number of experiments. The following two approaches were considered to identify OTPs. (1) A screening of LC-HR-MS signal formation in these experiments was performed and revealed a list of 1749 potential OTP candidate signals associated to 70 parent MPs. This list can be used in future suspect screening studies. (2) A screening was performed for signals that were formed in both batch experiments and in samples of wastewater treatment plants (WWTPs). This second approach was ultimately more time-efficient and was applied to four different WWTPs with ozonation (specific ozone doses in the range 0.23-0.55 gO₃/gDOC), leading to the identification of 84 relevant OTPs of 40 parent MPs in wastewater effluent. Chemical structures could be proposed for 83 OTPs through the interpretation of MS/MS spectra and expert knowledge in ozone chemistry. Forty-eight OTPs (58%) have not been reported previously. The fate of the verified OTPs was studied in different post-treatment steps. During sand filtration, 87-89% of the OTPs were stable. In granular activated carbon (GAC) filters, OTPs were abated with decreasing efficiency with increasing run times of the filters. For example, in a GAC filter with 16,000 bed volumes, 53% of the OTPs were abated, while in a GAC filter with 35,000 bed volumes, 40% of the OTPs were abated. The highest abatement (87% of OTPs) was observed when 13 mg/L powdered activated carbon (PAC) was dosed onto a sand filter.

A chronicle of SARS-CoV-2: Seasonality, environmental fate, transport, inactivation, and antiviral drug resistance

In this review, we present the environmental perspectives of the viruses and antiviral drugs related to SARS-CoV-2. The present review paper discusses occurrence, fate, transport, susceptibility, and inactivation mechanisms of viruses in the environment as well as environmental occurrence and fate of antiviral drugs, and prospects (prevalence and occurrence) of antiviral drug resistance (both antiviral drug resistant viruses and antiviral resistance in the human). During winter, the number of viral disease cases and environmental occurrence of antiviral drug surge due to various biotic and abiotic factors such as transmission pathways, human behaviour, susceptibility, and immunity as well as cold climatic conditions. Adsorption and persistence critically determine the fate and transport of viruses in the environment. Inactivation and disinfection of virus include UV, alcohol, and other chemical-base methods but the susceptibility of virus against these methods varies. Wastewater treatment plants (WWTPs) are major reserviors of antiviral drugs and their metabolites and transformation products. Ecotoxicity of antiviral drug residues against aquatic organisms have been reported, however more threatening is the development of antiviral resistance, both in humans and in wild animal reservoirs. In particular, emergence of antiviral drug-resistant viruses via exposure of wild animals to high loads of antiviral residues during the current pandemic needs further evaluation.

Occurrence and risk assessment of pharmaceutically active compounds in water supply systems in Brazil

The presence of pharmaceutically active compounds (PhACs) in water supply systems has been generating great concern about their effects on the environment and human health. Twenty-eight PhACs were monitored during one year in four Brazilian water sources, aiming to understand the factors that influence their occurrence and removal in conventional drinking water treatment plants (DWTPs) and to assess the environmental and human health risks. Trace levels of PhACs were detected in surface and drinking water in all assessed water sources. Effects of seasonality and socioeconomic aspects were observed in PhACs occurrence, like their higher concentrations during winter and in locales with higher values of gross domestic product per capita and human development index. Betamethasone, prednisone, and fluconazole were the most commonly detected PhACs, and also presented the highest concentrations. However, they were not related to toxicological risks. Nonetheless, all surface waters were subject to toxicological risk owing to at least one PhAC. PhACs related to the highest toxicological risks were loratadine, atorvastatin, norfloxacin, caffeine, and ranitidine, however, all these PhACs presented low quantification frequency. DWTPs capacity to remove PhACs was only partial, so treated water was still contaminated with these compounds. Furthermore, atorvastatin presented a margin of exposure below 100, indicating possible risk for public health. Thus, additional advanced treatment steps should be considered to improve PhACs removal during drinking water treatment.

Antiviral drugs in aquatic environment and wastewater treatment plants: A review on occurrence, fate, removal and ecotoxicity

The environmental release of antiviral drugs is of considerable concern due to potential ecosystem alterations and the development of antiviral resistance. As a result, interest on their occurrence and fate in natural and engineered systems has grown substantially in recent years. The main scope of this review is to fill the void of information on the knowledge on the worldwide occurrence of antiviral drugs in wastewaters and natural waters and correlate their levels with their environmental fate. According to the conducted literature survey, few monitoring data exists for several European countries, such as Germany, France, and the UK. Lesser data are available for Asia, where approximately 80% of the studies focus on Japan. Several articles study the occurrence of mostly antiretroantivirals in sub-Saharan African countries, while there is a lack of data for other developing regions of the world, including the rest of Africa, South America, and the biggest part of Asia. An importantly smaller number of studies exists for North America, while no studies exist for Oceania. The against innfluenza drug oseltamivir along with its active carboxy metabolite is found to be the most studied antiviral drug. The distribution of antiviral drugs across all geographic regions varies from low ng L^-1 to high μg L^-1 levels, in some cases, even in surface waters. This overarching review reveals that monitoring of antiviral drugs is necessary, and some of those compounds may require toxicological attention, in the light of either spatial and temporal high concentration or potential antiviral resistance. Based on the information provided herein, the need for a better understanding of the water quality hazards posed by antiviral drugs existence in wastewater outputs and freshwater ecosystems is demosntrated. Finally, the future challenges concerning the occurrence, fate, and potential ecotoxicological risk to organisms posed by antiviral drug residues are discussed.

Application of advanced oxidation processes and toxicity assessment of transformation products

Advanced Oxidation Processes (AOPs) are the techniques employed for oxidation of various organic contaminants in polluted water with the objective of making it suitable for human consumption like household and drinking purpose. AOPs use potent chemical oxidants to bring down the contaminant level in the water. In addition to this function, these processes are also capable to kills microbes (as disinfectant) and remove odor as well as improve taste of the drinking water. The non-photochemical AOPs methods include generation of hydroxyl radical in absence of light either by ozonation or through Fenton reaction. The photochemical AOPs methods use UV light along with H₂O₂, O₃ and/or Fe⁺² to generate reactive hydroxyl radical. Non-photochemical method is the commonly used whereas, photochemical method is used when conventional O₃ and H₂O₂ cannot completely oxidize organic pollutants. However, the choice of AOPs methods is depended upon the type of contaminant to be removed. AOPs cause loss of biological activity of the pollutant present in drinking water without generation of any toxicity. Conventional ozonation and AOPs can inactivate estrogenic compounds, antiviral compounds, antibiotics, and herbicides. However, the study of different AOPs methods for the treatment of drinking water has shown that oxidation of parent compound can also lead to the generation of a degradation/transformation product having biological activity/chemical toxicity similar to or different from the parent compound. Furthermore, an increased toxicity can also occur in AOPs treated drinking water. This review discusses various methods of AOPs, their merits, its application in drinking water treatment, the related issue of the evolution of toxicity in AOPs treated drinking water, biocatalyst, and analytical methods for identification of pollutants /transformed products and provides future directions to address such an issue.

Oxidation Processes in Water Treatment: Are We on Track?

Chemical oxidants have been applied in water treatment for more than a century, first as disinfectants and later to abate inorganic and organic contaminants. The challenge of oxidative abatement of organic micropollutants is the formation of transformation products with unknown (eco)toxicological consequences. Four aspects need to be considered for oxidative micropollutant abatement: (i) Reaction kinetics, controlling the efficiency of the process, (ii) mechanisms of transformation product formation, (iii) extent of formation of disinfection byproducts from the matrix, (iv) oxidation induced biological effects, resulting from transformation products and/or disinfection byproducts. It is impossible to test all the thousands of organic micropollutants in the urban water cycle experimentally to assess potential adverse outcomes of an oxidation. Rather, we need multidisciplinary and automated knowledge-based systems, which couple predictions of kinetics, transformation and disinfection byproducts and their toxicological consequences to assess the overall benefits of oxidation processes. A wide range of oxidation processes has been developed in the last decades with a recent focus on novel electricity-driven oxidation processes. To evaluate these processes, they have to be compared to established benchmark ozone- and UV-based oxidation processes by considering the energy demands, economics, the feasibilty, and the integration into future water treatment systems.

Ozonation of Para-Substituted Phenolic Compounds Yields p-Benzoquinones, Other Cyclic α,β-Unsaturated Ketones, and Substituted Catechols

Phenolic moieties are common functional groups in organic micropollutants and in dissolved organic matter, and are exposed to ozone during drinking water and wastewater ozonation. Although unsubstituted phenol is known to yield potentially genotoxic p-benzoquinone during ozonation, little is known about the effects of substitution of the phenol ring on transformation product formation. With batch experiments employing differing ozone/target compound ratios, it is shown that para-substituted phenols ( p-alkyl, p-halo, p-cyano, p-methoxy, p-formyl, p-carboxy) yield p-benzoquinones, p-substituted catechols, and 4-hydroxy-4-alkyl-cyclohexadien-1-ones as common ozonation products. Only in a few cases did para-substitution prevent the formation of these potentially harmful products. Quantum chemical calculations showed that different reaction mechanisms lead to p-benzoquinone, and that cyclohexadienone can be expected to form if no such pathway is possible. These products can thus be expected from most phenolic moieties. Kinetic considerations showed that substitution of the phenolic ring results in rather small changes of the apparent second order rate constants for phenol-ozone reactions at pH 7. Thus, in mixtures, most phenolic structures can be expected to react with ozone. However, redox cross-reactions between different transformation products, as well as hydrolysis, can be expected to further alter product distributions under realistic treatment scenarios.

Effect of operational and water quality parameters on conventional ozonation and the advanced oxidation process O3/H2O2: Kinetics of micropollutant abatement, transformation product and bromate formation in a surface water

The efficiency of ozone-based processes under various conditions was studied for the treatment of a surface water (Lake Zürich water, Switzerland) spiked with 19 micropollutants (pharmaceuticals, pesticides, industrial chemical, X-ray contrast medium, sweetener) each at 1 μg L^-1. Two pilot-scale ozonation reactors (4-5 m³ h^-1), a 4-chamber reactor and a tubular reactor, were investigated by either conventional ozonation and/or the advanced oxidation process (AOP) O₃/H₂O₂. The effects of selected operational parameters, such as ozone dose (0.5-3 mg L^-1) and H₂O₂ dose (O₃:H₂O₂ = 1:3-3:1 (mass ratio)), and selected water quality parameters, such as pH (6.5-8.5) and initial bromide concentration (15-200 μg L^-1), on micropollutant abatement and bromate formation were investigated. Under the studied conditions, compounds with high second-order rate constants k_O3>10⁴ M^-1 s^-1 for their reaction with ozone were well abated (>90%) even for the lowest ozone dose of 0.5 mg L^-1. Conversely, the abatement efficiency of sucralose, which only reacts with hydroxyl radicals (OH), varied between 19 and 90%. Generally, the abatement efficiency increased with higher ozone doses and higher pH and lower bromide concentrations. H₂O₂ addition accelerated the ozone conversion to OH, which enables a faster abatement of ozone-resistant micropollutants. Interestingly, the abatement of micropollutants decreased with higher bromide concentrations during conventional ozonation due to competitive ozone-consuming reactions, except for lamotrigine, due to the suspected reaction of HOBr/OBr^- with the primary amine moieties. In addition to the abatement of micropollutants, the evolution of the two main transformation products (TPs) of hydrochlorothiazide (HCTZ) and tramadol (TRA), chlorothiazide (CTZ) and tramadol N-oxide (TRA-NOX), respectively, was assessed by chemical analysis and kinetic modeling. Both selected TPs were quickly formed initially to reach a maximum concentration followed by a decrease of their concentrations for longer contact times. For the studied conditions, the TP's concentrations at the outlet of the reactors ranged from 0 to 61% of the initial parent compound concentration, CTZ being a more persistent TP against further oxidation than TRA-NOX. Finally, it was demonstrated in both reactors that the formation of bromate (BrO₃^-), a potentially carcinogenic oxidation by-product, could be controlled by H₂O₂ addition with a general improvement on micropollutant abatement. Post-treatment by granular activated carbon (GAC) filtration enabled the reduction of micropollutants and TPs concentrations but no changes in bromate were observed. The combined algae assay showed that water quality was significantly improved after oxidation and GAC post-treatment, driven by the abatement of the spiked pesticides (diuron and atrazine).

Contaminants of emerging concern: a review of new approach in AOP technologies

The presence of contaminants of emerging concern (CECs) such as pharmaceuticals and personal care products (PPCPs), endocrine-disrupting compounds (EDCs), flame retardants (FRs), pesticides, and artificial sweeteners (ASWs) in the aquatic environments remains a major challenge to the environment and human health. In this review, the classification and occurrence of emerging contaminants in aquatic environments were discussed in detail. It is well documented that CECs are susceptible to poor removal during the conventional wastewater treatment plants, which introduce them back to the environment ranging from nanogram per liter (e.g., carbamazepine) up to milligram per liter (e.g., acesulfame) concentration level. Meanwhile, a deep insight into the application of advanced oxidation processes (AOPs) on mitigation of the CECs from aquatic environment was presented. In this regard, the utilization of various treatment technologies based on AOPs including ozonation, Fenton processes, sonochemical, and TiO₂ heterogeneous photocatalysis was reviewed. Additionally, some innovations (e.g., visible light heterogeneous photocatalysis, electro-Fenton) concerning the AOPs and the combined utilization of AOPs (e.g., sono-Fenton) were documented.

A computer-based prediction platform for the reaction of ozone with organic compounds in aqueous solution: kinetics and mechanisms

Ozonation of secondary wastewater effluents can reduce the discharge of micropollutants by transforming their chemical structures. Therefore, a better understanding of the formation of transformation products during ozonation is important. In this study, a computer-based prediction platform for the kinetics and mechanisms of the reactions of ozone with organic compounds was developed to enable in silico predictions of transformation products. With the developed prediction platform, reaction kinetics expressed as second-order rate constants for the reactions of ozone with selected organic compounds (k_O3, M^-1 s^-1) can be predicted based on an adapted k_O3 prediction model from a previous study (Lee et al., Environ. Sci. Technol., 2015, 49, 9925-9935) (average model error of about a factor of 6 for 14 compound classes with 284 model compounds). Ozone reaction mechanisms reported in the literature have been reviewed and, using chemoinformatics tools, encoded into about 340 individual reaction rules that can be generally applied to predict the transformation products of micropollutants. Predictions for k_O3 and/or transformation products were overall consistent with the experimental data for three micropollutants used as validation compounds (e.g., carbamazepine, tramadol, and triclosan). However, limitations of the current k_O3 prediction platform were also identified: ambiguous assignment of the n-th highest occupied molecular orbital energy (E_HOMO-n) to the reactive sites, potential errors associated with the use of a gas-phase geometry, and a poor k_O3 prediction for certain compounds (cetirizine). Therefore, the current prediction tool should not be considered as a substitute for experimental studies and experimental data are still required in the future to obtain a more robust prediction model. Nonetheless, the developed prediction platform, made available as a stand-alone graphical user interface (GUI) application, will provide useful information about aqueous ozone chemistry to various groups of end-users such as environmental chemists, engineers, or toxicologists.

The chlorination behaviour and environmental fate of the antiretroviral drug nevirapine in South African surface water

The wastewater treatment process, besides discharging pharmaceuticals into the environment, has been found to result in the formation of a variety of undescribed compounds. Here we investigate the laboratory scale chlorination of the commonly used anti-HIV drug Nevirapine, characterise its disinfection transformation products (DTPs), and using liquid chromatography with high resolution mass spectrometry, screen environmental surface water for these DTPs. Chlorination of Nevirapine was scaled up, fractioned by preparative chromatography and the fractions were tested in vitro for toxicity and anti-HIV activity. Nevirapine was found to be resistant to degradation at relevant chlorination levels, which may partially explain its ubiquitous presence in South African surface water. During simulated chlorination, a variety of DTPs with varying properties were formed, some of which were detected in the environment, close to wastewater treatment plants. Interestingly, some of these compounds, although not as toxic as Nevirapine, retained antiviral activity. Further purification and synthesis is required to fully characterise these novel molecules.

Risk of resistant avian influenza A virus in wild waterfowl as a result of environmental release of oseltamivir

Oseltamivir is the best available anti-influenza drug and has therefore been stockpiled worldwide in large quantities as part of influenza pandemic preparedness planning. The active metabolite oseltamivir carboxylate (OC) is stable and is not removed by conventional sewage treatment. Active OC has been detected in river water at concentrations up to 0.86 µg/L. Although the natural reservoir hosts of influenza A virus (IAV) are wild waterfowl that reside in aquatic environments, the ecologic risks associated with environmental OC release and its potential to generate resistant viral variants among wild birds has largely been unknown. However, in recent years a number of in vivo mallard (Anas platyrhynchos) studies have been conducted regarding the potential of avian IAVs to become resistant to OC in natural reservoir birds if these are drug exposed. Development of resistance to OC was observed both in Group 1 (N1) and Group 2 (N2, N9) neuraminidase subtypes, when infected ducks were exposed to OC at concentrations between 0.95 and 12 µg/L in their water. All resistant variants maintained replication and transmission between ducks during drug exposure. In an A(H1N1)/H274Y virus, the OC resistance mutation persisted without selective drug pressure, demonstrating the potential of an IAV with a permissive genetic background to acquire and maintain OC resistance, potentially allowing circulation of the resistant variant among wild birds. The experimental studies have improved the appreciation of the risks associated with the environmental release of OC related to resistance development of avian IAVs among wild birds. Combined with knowledge of efficient methods for improved sewage treatment, the observations warrant implementation of novel efficient wastewater treatment methods, rational use of anti-influenza drugs, and improved surveillance of IAV resistance in wild birds.

Transformation of Contaminant Candidate List (CCL3) compounds during ozonation and advanced oxidation processes in drinking water: Assessment of biological effects

The removal of emerging contaminants during water treatment is a current issue and various technologies are being explored. These include UV- and ozone-based advanced oxidation processes (AOPs). In this study, AOPs were explored for their degradation capabilities of 25 chemical contaminants on the US Environmental Protection Agency's Contaminant Candidate List 3 (CCL3) in drinking water. Twenty-three of these were found to be amenable to hydroxyl radical-based treatment, with second-order rate constants for their reactions with hydroxyl radicals (OH) in the range of 3-8 × 10(9) M(-1) s(-1). The development of biological activity of the contaminants, focusing on mutagenicity and estrogenicity, was followed in parallel with their degradation using the Ames and YES bioassays to detect potential changes in biological effects during oxidative treatment. The majority of treatment cases resulted in a loss of biological activity upon oxidation of the parent compounds without generation of any form of estrogenicity or mutagenicity. However, an increase in mutagenic activity was detected by oxidative transformation of the following CCL3 parent compounds: nitrobenzene (OH, UV photolysis), quinoline (OH, ozone), methamidophos (OH), N-nitrosopyrolidine (OH), N-nitrosodi-n-propylamine (OH), aniline (UV photolysis), and N-nitrosodiphenylamine (UV photolysis). Only one case of formation of estrogenic activity was observed, namely, for the oxidation of quinoline by OH. Overall, this study provides fundamental and practical information on AOP-based treatment of specific compounds of concern and represents a framework for evaluating the performance of transformation-based treatment processes.

Spoilt for choice: A critical review on the chemical and biological assessment of current wastewater treatment technologies

The knowledge we have gained in recent years on the presence and effects of compounds discharged by wastewater treatment plants (WWTPs) brings us to a point where we must question the appropriateness of current water quality evaluation methodologies. An increasing number of anthropogenic chemicals is detected in treated wastewater and there is increasing evidence of adverse environmental effects related to WWTP discharges. It has thus become clear that new strategies are needed to assess overall quality of conventional and advanced treated wastewaters. There is an urgent need for multidisciplinary approaches combining expertise from engineering, analytical and environmental chemistry, (eco)toxicology, and microbiology. This review summarizes the current approaches used to assess treated wastewater quality from the chemical and ecotoxicological perspective. Discussed chemical approaches include target, non-target and suspect analysis, sum parameters, identification and monitoring of transformation products, computational modeling as well as effect directed analysis and toxicity identification evaluation. The discussed ecotoxicological methodologies encompass in vitro testing (cytotoxicity, genotoxicity, mutagenicity, endocrine disruption, adaptive stress response activation, toxicogenomics) and in vivo tests (single and multi species, biomonitoring). We critically discuss the benefits and limitations of the different methodologies reviewed. Additionally, we provide an overview of the current state of research regarding the chemical and ecotoxicological evaluation of conventional as well as the most widely used advanced wastewater treatment technologies, i.e., ozonation, advanced oxidation processes, chlorination, activated carbon, and membrane filtration. In particular, possible directions for future research activities in this area are provided.

Novel test procedure to evaluate the treatability of wastewater with ozone

Organic micropollutants such as pharmaceuticals, estrogens or pesticides enter the environment continuously through the effluent of municipal wastewater treatment plants (WWTPs). Enhanced treatment of wastewater (WW) by ozone (O3) is probably one of the simplest measures for abatement of organic micropollutants to avoid their discharge to the aquatic environment. During ozonation most organic micropollutants present in treated WW are oxidized either by a direct reaction with O3 or by secondarily formed hydroxyl radicals (OH). However, undesired oxidation by-products from the oxidative transformation of matrix components can also be formed. A modular laboratory decision tool based on the findings of previous investigations is presented to test the feasibility of ozonation as an option to upgrade specific WWTPs. These modules consist of investigations to assess (i) the matrix effects on ozone stability, (ii) the efficiency of micropollutant removal, (iii) the oxidation by-product formation, as well as (iv) bioassays to measure specific and unspecific toxicity of the treated WWs. Matrix effects on ozone stability (quantified as O3 and OH exposures) can give first indications on the suitability of an ozonation step. Ozonation of WWs yielding O3 and OH exposures and micropollutant abatement similar to reference values evoked a significant improvement of the water quality as indicated by a broad range of bioassays. Irregular behavior of the ozonation points towards unknown compounds, possibly leading to the formation of undesired degradation products. It has been observed that in such WWs ozonation partly enhanced toxicity. In summary, the presented tiered laboratory test procedure represents a relatively cheap and straight-forward methodology to evaluate the feasibility of ozonation to upgrade specific WWTPs for micropollutant removal based on chemical and biological measurements.

Degradation of pharmaceuticals and metabolite in synthetic human urine by UV, UV/H2O2, and UV/PDS

To minimize environmental pharmaceutical micropollutants, treatment of human urine could be an efficient approach due to the high pharmaceutical concentration and toxic potential excreted in urine. This study investigated the degradation kinetics and mechanisms of sulfamethoxazole (SMX), trimethoprim (TMP) and N4-acetyl-sulfamethoxazole (acetyl-SMX) in synthetic fresh and hydrolyzed human urines by low-pressure UV, and UV combined with H2O2 and peroxydisulfate (PDS). The objective was to compare the two advanced oxidation processes (AOPs) and assess the impact of urine matrices. All three compounds reacted quickly in the AOPs, exhibiting rate constants of (6.09-8.53) × 10(9) M(-1)·s(-1) with hydroxyl radical, and (2.35-16.1) × 10(9) M(-1)·s(-1) with sulfate radical. In fresh urine matrix, the pharmaceuticals' indirect photolysis was significantly suppressed by the scavenging effect of urine citrate and urea. In hydrolyzed urine matrix, the indirect photolysis was strongly affected by inorganic urine constituents. Chloride had no apparent impact on UV/H2O2, but significantly raised the hydroxyl radical concentration in UV/PDS. Carbonate species reacted with hydroxyl or sulfate radical to generate carbonate radical, which degraded SMX and TMP, primarily due to the presence of aromatic amino group(s) (k = 2.68 × 10(8) and 3.45 × 10(7) M(-1)·s(-1)) but reacted slowly with acetyl-SMX. Ammonia reacted with hydroxyl or sulfate radical to generate reactive nitrogen species that could react appreciably only with SMX. Kinetic simulation of radical concentrations, along with products analysis, helped elucidate the major reactive species in the pharmaceuticals' degradation. Overall, the AOPs' performance was higher in the hydrolyzed urine than fresh urine matrix with UV/PDS better than UV/H2O2, and varied significantly depending on pharmaceutical's structure.

Evaluation of the persistence of transformation products from ozonation of trace organic compounds - a critical review

Ozonation is an efficient treatment system to reduce the concentration of trace organic compounds (TrOCs) from technical aquatic systems such as drinking water, wastewater and industrial water, etc. Although it is well established that ozonation generally improves the removal of organic matter in biological post-treatment, little is known about the biodegradability of individual transformation products resulting from ozonation of TrOCs. This publication provides a qualified assessment of the persistence of ozone-induced transformation products based on a review of published product studies and an evaluation of the biodegradability of transformation products with the biodegradability probability program (BIOWIN) and the University of Minnesota Pathway Prediction System (UM-PPS). The oxidation of TrOCs containing the four major ozone-reactive sites (olefins, amines, aromatics and sulfur-containing compounds) follows well described reaction pathways leading to characteristic transformation products. Assessment of biodegradability revealed a high sensitivity to the formed products and hence the ozone-reactive site present in the target compound. Based on BIOWIN, efficient removal can be expected for products from cleavage of olefin groups and aromatic rings. In contrast, estimations and literature indicate that hydroxylamines and N-oxides, the major products from ozonation of secondary and tertiary amines are not necessarily better removed in biological post-treatment. According to UM-PPS, degradation of these products might even occur via reformation of the corresponding amine. Some product studies with sulfide-containing TrOCs showed a stoichiometric formation of sulfoxides from oxygen transfer reactions. However, conclusions on the fate of transformation products in biological post-treatment cannot be drawn based on BIOWIN and UM-PPS.

Assessing exposure risks for aquatic organisms posed by Tamiflu use under seasonal influenza and pandemic conditions

Environmental pollution by anti-influenza drugs is increasingly recognized as a threat to aquatic environments. However, little is known about empirical data on risk effects posed by environmentally relevant concentrations of anti-influenza drug based on recently published ecotoxicological researches in Taiwan. Here we linked ecotoxicology models with an epidemiological scheme to assess exposure risks of aquatic organisms and environmental hazards posed by antiviral oseltamivir (Tamiflu) use in Taiwan. Built on published bioassays, we used probabilistic risk assessment model to estimate potential threats of environmentally relevant hazards on algae, daphnid, and zerbrafish. We found that Tamiflu use was unlikely to pose a significant chronic environmental risk to daphnia and zebrafish during seasonal influenza. However, the chronic environmental risk posed by Tamiflu use during pandemic was alarming. We conclude that no significant risk to algal growth was found during seasonal influenza and high pandemic Tamiflu use.

Profile and behavior of antiviral drugs in aquatic environments of the Pearl River Delta, China

Occurrence and behavior of six antiviral pharmaceuticals (acyclovir, ganciclovir, oseltamivir, ribavirin, stavudine and zidovudine) and one active metabolite oseltamivir carboxylate were investigated in wastewater, landfill leachate, river water, reservoir and well water in the vicinity of municipal landfills in the Pearl River Delta, China. Acyclovir was the only antiviral detected in the wastewater at 177-406 (mean=238) and 114-205 (mean=154) ng L(-1) in the influent and final effluent, respectively. Aerobic biodegradation appeared to be the main process for the elimination of acyclovir in the wastewater. Acyclovir was also the only antiviral quantitatively detected in the Pearl River and its tributaries, with a maximum concentration up to 113 ng L(-1). Treated wastewater was a major source of acyclovir in the rivers. The highest concentration of acyclovir was observed in winter in the river water and the dilution effect by precipitation was suggested to be the dominant factor impacting the seasonal pattern of acyclovir in the rivers. No antivirals were quantitatively detected in the well water whereas acyclovir was frequently detected in the reservoirs at a maximal concentration of 33.6 ng L(-1) in the vicinity of the municipal landfills. However, source identification and fate of acyclovir in the reservoirs pend on further research.