Occurrence and removal of triclosan in Canadian wastewater systems

Endocrine disruptors and antimicrobial agents in an intercity study in England: Towards holistic environmental and public exposure assessment using water-based epidemiology and retrospective mass spectra data mining

An analytical framework was developed, allowing for suspect screening and retrospective quantification of hazardous household-derived chemicals (HDCs) in community wastewater and river water to assess public exposure and environmental health status. 11 HDCs (bisphenol A, 4 parabens, 5 antimicrobials and benzophenone-1) and 2 metabolites (bisphenol A sulfate and triclosan sulfate) were identified, confirmed and quantified in mass spectra from a multi-city study covering 5 contrasting towns and cities in England within a catchment served by 5 wastewater treatment plants (WwTPs), representing > 75 % of the whole catchment population (∼1.5 million people) and covering a 2000 km2 area. A further 5 HDC metabolites: hydroxytriclocarban,p-chlorocresol sulfate, 2,6-dimethyl-1,4-benzenediol, chloroxylenol sulfate, 2-benzyl-1,4-benzenediol were for the first time tentatively identified in wastewater and river water using suspect screening. Trends in daily loads and population normalised daily loads of HDCs were studied. Population size was identified as the key driver of environmental burden, however, impacts from industrial usage were also apparent in the case of BPA and parabens. For example, BPA population normalised daily loads indicated higher exposure estimated for communities with industrial presence indicating occupational exposure. Environmental risk assessment was also undertaken for 11 HDCs using the risk quotient (RQ) method. RQ values < 0.1, found for most HDCs in river water, suggested low risk. However, RQ values > 1 found for triclosan and triclocarban indicated potentially high risk to the environment, which is concerning due to their endocrine disruption and antimicrobial resistance properties. This study verified the potential for holistic assessment of both community and environmental exposure. It showed that different chemicals might need to be considered in the context of risks to humans and the environment (e.g., bisphenol A of high risk to humans vs triclosan and triclocarban being of high risk to the aquatic environment). Lack of analytical standards for metabolic biomarkers, as well as lack of understanding of metabolic pathways of HDCs were identified as the key limiting factors in establishing WBE as a holistic One Health tool for combined environmental and public health assessment of HDCs, especially those that are not intended for human consumption.

Long-term and low-dose exposure to triclosan induces POI phenotype in female offspring mice

Triclosan (TCS), a typical endocrine disruptor, is widely used as an antibacterial agent in consumer goods. However, there are few studies on the effects of long-term low-dose TCS exposure on ovarian function in F1 female mice. In this paper, F1 female mice were exposed to TCS (0-3000 μg/kg/day) from intrauterine to postnatal day (PND) 91 to investigate its effects on the ovary. The results revealed that the number of total follicles was decreased, while atretic follicles was increased after TCS exposure. At the hormonal level, the secretion of estradiol was reduced, while follicle-stimulating hormone and luteinizing hormone were increased after TCS exposure. Observation of vaginal smear showed that TCS disrupted the estrous cycle of F1 female mice, especially at the dose of 3000 μg/kg/day. Moreover, TCS promoted cell apoptosis by activating the p38-MAPK signaling pathway and oxidative stress in vitro. In addition, analysis of the fecal microbiome and serum metabolomics revealed that exposure to TCS may cause gut microbiota disruption and metabolic abnormalities in F1 female mice. In conclusion, long-term low-dose TCS exposure may induce primary ovarian insufficiency phenotype in F1 female mice via inducing cell apoptosis and disrupting gut microbiota and metabolism.

MnO2-Catalyzed electrocatalytic mineralization of triclosan in chlorinated wastewater

The rising concentrations of xenobiotic aromatic compounds in the environment pose significant risks to human and ecosystem health. Developing a universal, environmentally benign, and scalable platform for mineralizing organic pollutants before their release into the environment is therefore crucial. Electrocatalysis can be highly advantageous for wastewater treatment because it is immediately responsive upon applying potential, requires no additional chemicals, and typically uses heterogeneous catalysts. However, achieving efficient electrochemical mineralization of wastewater pollutants at parts-per-million (ppm) levels remains a challenge. Here, we report the use of manganese dioxide (MnO2), an Earth-abundant, chemically benign, and cost-effective electrocatalyst, to achieve over 99 % mineralization of triclosan (TCS) and other halogenated phenols at ppm levels. Two highly active MnO2 phases-α-MnO2-CC and δ-MnO2-CC-were fabricated on inexpensive carbon cloth (CC) support and evaluated for their ability to oxidatively degrade TCS in pH-neutral conditions, including simulated chlorinated wastewater, real wastewater, and both synthetic and real landfill leachates. Total organic carbon analysis confirmed the effective degradation of TCS. Electron paramagnetic resonance and ultraviolet-visible spectroscopy identified reactive oxygen species, enabling the construction of a detailed TCS degradation pathway. Upon optimization, the TCS removal rate reached 38.38 nmol min-1, surpassing previously reported rates achieved with precious and toxic metal co-catalysts. These findings highlight MnO2-CC as a promising, eco-friendly electrocatalyst with strong potential for upscaled remediation of organic pollutants in wastewater treatment.

Antibiotics and other micropollutants in Swiss sewage sludge and fecal compost

Antibiotics are of environmental concern. Their concentrations in the aquatic environment are frequently studied, while their occurrence in human excreta-derived fertilizers is less investigated. Therefore, levels of antibiotics, preservatives with antimicrobial properties, and various other micropollutants were determined in sewage sludge and in human fecal compost. Digested sludge of 29 Swiss wastewater treatment plants was analyzed, representing about 2.6 Mio people (30% of the Swiss population). This was compared with residues found in compost with dry toilet content after thermophilic composting, representing about 10 000 people. Fluoroquinolones and preservatives dominate in Swiss sewage sludge with weighted mean concentrations of 6500 μg kg-1 and 2300 μg kg-1. Levels of macrolides (240 μg kg-1), β-lactam transformation products (35 μg kg-1) and sulfonamides (15 μg kg-1) were lower. Pollution patterns in digested sewage sludge were relatively constant throughout Switzerland. Levels of contamination in fecal compost were approximately 30 times lower than in sewage sludge. Pollution patterns differed between compost and sludge. Chemicals used in down-the-drain-applications (e.g., preservatives from personal care products or corrosion inhibitors) are less relevant in compost. Based on the Swiss consumption and excretion data, a mass flow analysis was carried out for antibiotics and pharmaceuticals in sludge and compost. The mass flow analysis in sludge showed a good agreement of predicted and measured concentrations for compounds that tend to sorb to organic matter (e.g., fluoroquinolones). Currently, there is no specific legislation that regulates the use of fecal compost from dry toilets as fertilizer. However, the one to two order of magnitude lower levels of contaminants in fecal compost compared to sludge and manure indicate a lower environmental risk when applying it as fertilizer.

Pharmaceuticals and personal care products in Canadian municipal wastewater and biosolids: occurrence, fate, and time trends 2010-2013 to 2022

The concentrations of 135 pharmaceuticals and personal care products (PPCPs) were determined in raw influent, final effluent, and treated biosolids at Canadian wastewater treatment plants (WWTPs) to evaluate the fate of PPCPs through liquid and solids trains of typical treatment types used in Canada and to assess changes in PPCP concentrations in wastewater matrices between 2010-2013 and 2022. PPCPs dominant in influent and effluent included the antidiabetic metformin, analgesics/anti-inflammatories (acetaminophen, ibuprofen, 2-hydroxy-ibuprofen), caffeine and its metabolite (1,7 - dimethylxanthine), theophylline (a bronchodilator and metabolite of caffeine), an insect repellent (N,N-diethyl-m-toluamide, DEET), and iopamidol (a contrast media for X-rays). PPCPs dominant in biosolids differed from those in influent/effluent and included antibiotics (fluoroquinolones and doxycycline), antidepressants (sertraline, citalopram, and amitriptyline), a preservative and antimicrobial agent (triclosan), an antihistamine (diphenhydramine), and an antifungal (clotrimazole). These elevated concentrations in influent/effluent and biosolids reflected their use in Canadian communities. PPCPs dominant in influent/effluent had relatively low hydrophobicity whereas those in biosolids tended to be more hydrophobic, or electrostatic forces governed their sorption. Higher removal of PPCPs was generally observed at WWTPs that used biological treatment compared to primary physical/chemical treatment. PPCP concentration changes in wastewater matrices between 2010-2013 and 2022 were influenced by risk management measures, warnings, the development of new pharmaceuticals, the COVID-19 pandemic, and other factors. These time trends reflected the limited information available on PPCP use in Canada. Continued periodic monitoring of PPCPs is recommended to fill data gaps on community use and release to the environment.

Occurrence and distribution of emerging contaminants in wastewater treatment plants: A globally review over the past two decades

Emerging contaminants are pervasive in aquatic environments globally, encompassing pharmaceuticals, personal care products, steroid hormones, phenols, biocides, disinfectants and various other compounds. Concentrations of these contaminants are detected ranging from ng/L to μg/L. Even at trace levels, these contaminants can pose significant risks to ecosystems and human health. This article systematically summarises and categorizes data on the concentrations of 54 common emerging contaminants found in the influent and effluent of wastewater treatment plants across various geographical regions: North America, Europe, Oceania, Africa, and Asia. It reviews the occurrence and distribution of these contaminants, providing spatial and causal analyses based on data from these regions. Notably, the maximum concentrations of the pollutants observed vary significantly across different regions. The data from Africa, in particular, show more frequent detection of pharmaceutical maxima in wastewater treatment plants.

The effect of triclosan on intergeneric horizontal transmission of plasmid-mediated tigecycline resistance gene tet(X4) from Citrobacter freundii isolated from grass carp gut

The transmission of antibiotic resistance genes (ARGs) in pathogenic bacteria affects culture animal health, endangers food safety, and thus gravely threatens public health. However, information about the effect of disinfectants - triclosan (TCS) on ARGs dissemination of bacterial pathogens in aquatic animals is still limited. One Citrobacter freundii (C. freundii) strain harboring tet(X4)-resistant plasmid was isolated from farmed grass carp guts, and subsequently conjugative transfer frequency from C. freundii to Escherichia coli C600 (E. coli C600) was analyzed under different mating time, temperature, and ratio. The effect of different concentrations of TCS (0.02, 0.2, 2, 20, 200 and 2000 μg/L) on the conjugative transfer was detected. The optimum conditions for conjugative transfer were at 37 °C for 8h with mating ratio of 2:1 or 1:1 (C. freundii: E. coli C600). The conjugative transfer frequency was significantly promoted under TCS treatment and reached the maximum value under 2.00 μg/L TCS with 18.39 times that of the control group. Reactive oxygen species (ROS), superoxide dismutase (SOD) and catalase (CAT) activities, cell membrane permeability of C. freundii and E. coli C600 were obviously increased under TCS stress. Scanning electron microscope showed that the cell membrane surface of the conjugative strains was wrinkled and pitted, even broken at 2.00 μg/L TCS, while lysed or even ruptured at 200.00 μg/L TCS. In addition, TCS up-regulated expression levels of oxidative stress genes (katE, hemF, bcp, hemA, katG, ahpF, and ahpC) and cell membrane-related genes (fimC, bamE and ompA) of donor and recipient bacteria. Gene Ontology (GO) enrichment demonstrated significant changes in categories relevant to pilus, porin activity, transmembrane transporter activity, transferase activity, hydrolase activity, material transport and metabolism. Taken together, a tet(X4)-resistant plasmid could horizontal transmission among different pathogens, while TCS can promote the propagation of the resistant plasmid.

Assessing Contributions of Synthetic Musk Compounds from Wastewater Treatment Plants to Atmospheric and Aquatic Environments

The high environmental concentrations, persistence, and toxicity of synthetic musk compounds (SMCs) necessitate a better grasp of their fate in wastewater treatment plants (WWTPs). To investigate the importance of WWTPs as pathways of SMCs to the environment, air and wastewater samples were collected at four WWTPs in Ontario, Canada. Polycyclic musks (PCMs) were present at higher concentrations than nitro musks (NMs) and macrocyclic musks (MCMs). Three PCMs [galaxolide (HHCB), tonalide (AHTN), and iso-E super (OTNE)] were the most abundant compounds (0.30-680 ng/m3 in air, 0.40-15 μg/L in influent, and 0.007-6.0 μg/L in effluent). Analyses of multiyear data suggest that risk management measures put in place have been effective in reducing the release of many SMCs into the environment. The highest removal efficiency, up to almost 100% of some SMCs, was observed for the plant with the longest solid retention time. A fugacity-based model was established to simulate the transport and fate of SMCs in the WWTP, and good agreement was obtained between the measured and modeled values. These findings indicate that the levels of certain SMCs discharged into the atmospheric and aquatic environments were substantial, potentially resulting in exposure to both humans and wildlife.

Triclosan induces liver injury in long-life exposed mice via activation of TLR4/NF-κB/NLRP3 pathway

Triclosan (TCS) is a widely used synthetic, with broad-spectrum antibacterial properties found in both pharmaceuticals and personal care products. More specifically, it is hepatotoxic in rodents and exhibits differential effects in mice and humans. However, the mechanisms underlying TCS-induced liver toxicity have not been elucidated. This study examined the role of the toll-like receptor 4 (TLR4)/ nuclear factor kappa B (NF-κB)/ nod-like receptor protein 3 (NLRP3) pathway in TCS-exposed liver toxicity by established a long-life TCS-exposed mice liver injury model. The 24 C57BL/6 pregnant mice exposed to TCS (0, 50 and 100 mg/kg) every day during the gestation and nursing period. After weaning, the male mice were left to continue administrate with TCS until 8 weeks of age. Then, mice in each group were sacrificed for investigation. Long-life exposure to TCS resulted in a reduction of body weight in growth mice. TCS exposure caused the increase of serum ALT, AST and ALP. The situation of inflammatory cell infiltration, macrophage recruitment and collagen fiber deposition in TCS-exposed mice liver tissues were performed by histological analysis including hematoxylin-eosin, Masson, Sirius red, and immunohistochemistry staining. Protein expression levels in TLR4/NF-κB/NLRP3 pathway was measured through Western blot, and the NLRP3 inflammasome activation was measured using real-time quantitative PCR (RT-qPCR). The results showed that exposure to TCS elevated TLR4, myeloid differentiation factor 88 (Myd88), TNF receptor associated factor 6 (TRAF6), enhanced NF-κB activation, and affected NLRP3 inflammasome activation in mice liver. Collectively, these findings indicate that long-life exposure to TCS-induced mice by upregulating the TLR4-Myd88-TRAF6 pathway, activating the NF-κB signaling cascade, initiating the NLRP3 inflammasome pathway, and ultimately leading to liver injury, including inflammation, hepatocyte pyroptosis and hepatofibrosis. Henceforth, the TLR4/NF-κB/NLRP3 pathway may now provide a theoretical basis and valuable therapeutic targets for overcoming TCS-induced liver toxicity.

Potential application of 2D nano-layered MXene in analysing and remediating endocrine disruptor compounds and heavy metals in water

With the advancement of technologies and growth of the economy, it is inevitable that more complex processes are deployed, producing more heterogeneous wastewater that comes from biomedical, biochemical and various biotechnological industries. While the conventional way of wastewater treatment could effectively reduce the chemical oxygen demand, pH and turbidity of wastewater, trace pollutants, specifically the endocrine disruptor compounds (EDCs) that exist in µg L-1 or ng L-1 have further hardened the detection and removal of these biochemical pollutants. Even in small amounts, EDC could interfere human's hormone, causing severe implications on human body. Hence, this review elucidates the recent insights regarding the effectiveness of an advanced 2D material based on titanium carbide (Ti3C2Tx), also known as MXene, in detecting and removing EDCs. MXene's highly tunable feature also allows its surface chemistry to be adjusted by adding chemicals with different functional groups to adsorb different kinds of EDCs for biochemical pollution mitigation. At the same time, the incorporation of MXene into sample matrices also further eases the analysis of trace pollutants down to ng L-1 levels, thereby making way for a more cleaner and comprehensive wastewater treatment. In that sense, this review also highlights the progress in synthesizing MXene from the conventional method to the more modern approaches, together with their respective key parameters. To further understand and attest to the efficacy of MXene, the limitations and current gaps of this potential agent are also accentuated, targeting to seek resolutions for a more sustainable application.

Addressing the challenges of combined sewer overflows

Europe's ageing wastewater system often combines domestic sewage with surface runoff and industrial wastewaters. To reduce the associated risk of overloading wastewater treatment works during storms, and to prevent wastewater backing-up into properties, Combined Sewer Overflows (CSOs) are designed into wastewater networks to release excess discharge into rivers or coastal waters without treatment. In view of growing regulatory scrutiny and increasing public concern about their excessive discharge frequencies and potential impacts on environments and people, there is a need to better understand these impacts to allow prioritisation of cost-effective solutions.We review: i) the chemical, physical and biological composition of CSOs discharges; ii) spatio-temporal variations in the quantity, quality and load of overflows spilling into receiving waters; iii) the potential impacts on people, ecosystems and economies. Despite investigations illustrating the discharge frequency of CSOs, data on spill composition and loading of pollutants are too few to reach representative conclusions, particularly for emerging contaminants. Studies appraising impacts are also scarce, especially in contexts where there are multiple stressors affecting receiving waters. Given the costs of addressing CSOs problems, but also the likely long-term gains (e.g. economic stimulation as well as improvements to biodiversity, ecosystem services, public health and wellbeing), we highlight here the need to bolster these evidence gaps. We also advocate no-regrets options to alleviate CSO problems taking into consideration economic costs, carbon neutrality, ecosystem benefit and community well-being. Besides pragmatic, risk-based investment by utilities and local authorities to modernise wastewater systems, these include i) more systemic thinking, linking policy makers, consumers, utilities and regulators, to shift from local CSO issues to integrated catchment solutions with the aim of reducing contributions to wastewater from surface drainage and water consumption; ii) broader societal responsibilities for CSOs, for example through improved regulation, behavioural changes in water consumption and disposal of waste into wastewater networks, and iii) greater cost-sharing of wastewater use.

The pleiotropic role of Salinicoccus bacteria in enhancing ROS homeostasis and detoxification metabolism in soybean and oat to cope with pollution of triclosan

Triclosan has been extensively used as a preservative in cosmetics and personal care products. However, its accumulation represents a real environmental threat. Thus, its phytotoxic impact needs more consideration. Our study was conducted to highlight the phytotoxic effect of triclosan on the growth, ROS homeostasis, and detoxification metabolism of two different plant species i.e., legumes (Glycine max) and grass (Avena sativa). Moreover, we investigated the potentiality of plant growth-promoting bacteria (ST-PGPB) in mitigating the phytotoxic effect of triclosan. Triclosan induced biomass (fresh and dry weights) reduction in both plants, but to a higher extent in oats. This decline was associated with a noticeable increment in the oxidative damage (e.g., MDA and H2O2) and detoxification metabolites such as metallothionein (MTC), phytochelatins (PCs), and glutathione-S-transferase (GST). This elevation was associated with a remarkable reduction in both enzymatic and non-enzymatic antioxidants. On the other hand, the bioactive strain of ST-PGPB, Salinicoccus sp. JzA1 significantly alleviated the harmful effect of triclosan on both soybean and oat plants by enhancing their biomass, photosynthesis, as well as levels of minerals (K, Ca, P, Mn, and Zn). In parallel, a striking quenching in oxidative damage and an obvious improvement in non-enzymatic (polyphenols, tocopherols, flavonoids) and enzymatic antioxidants were observed. Furthermore, Salinicoccus sp. JzA1 augmented the detoxification metabolism by enhancing the levels of phytochelatins, metallothionein, and glutathione-S-transferase (GST) activity in a species-specific manner which is more apparent in soybean rather than in oat plants. To this end, stress mitigating impact of Salinicoccus sp. JzA1 provides a basis to improve the resilience of crop species under cosmetics and personal care products toxicity.

Ecotoxicological and human health risk assessment of triclosan antibacterial agent from municipal wastewater treatment plants

In this study, the occurrence and environmental risks related to triclosan (TCS) in the two wastewater treatment plants (WWTPs) were investigated in Isfahan, Iran. Influent and effluent samples were collected and analyzed by dispersive liquid-liquid microextraction (DLLME)-GC-MS method with derivatization. Moreover, the risk of TCS exposure was conducted for aquatic organisms (algae, crustaceans, and fishes) and humans (males and females). TCS mean concentrations in influent and effluent of WWTPs were in the range of 3.70-52.99 and 0.83-1.09 μg/L, respectively. There were also no differences in the quantity of TCS and physicochemical parameters among the two WWTPs. The mean risk quotient (RQ) for TCS was higher than 1 (in algae) with dilution factors (DFs) equal to 1 in WWTP1. Moreover, the RQ value was higher than 1 for humans based on the reference dose of MDH (RFDMDH) in WWTP1. Furthermore, TCS concentration in wastewater effluent was the influential factor in varying the risk of TCS exposure. The results of the present study showed the risk of TCS exposure from the discharge of effluent of WWTP1 was higher than WWTP2. Moreover, the results of this study may be suitable for promoting WWTP processes to completely remove micropollutants.

Applying weight of evidence methods to assessing exposure in aquatic environments: Comparing lines of evidence

Weight of evidence (WoE) is a useful approach to quantifying the relative relevance, strength, reliability, and uncertainty associated with estimates of exposure concentrations. WoE is often used in exposure assessments but rarely explored or discussed in detail. In this article, the utility of a WoE approach in aquatic exposure assessments is illustrated via two case studies using a tiered approach and the chemical triclosan. Each case study evaluates the same chemical and pathway to the environment but with substantially different data strength, reliability, and uncertainty. The collection and qualitative evaluation of relevant lines of evidence (LoE) using a three-tiered approach are discussed. Our results demonstrate how a higher tiered WoE approach can reduce uncertainty and improve decision-making based on predicted exposure concentrations. We also identify LoE that played a significant role in the final exposure determinations and describe a framework for conducting exposure assessments using WoE. Integr Environ Assess Manag 2023;19:1207-1219. © 2022 SETAC.

Triclosan and related compounds in the environment: Recent updates on sources, fates, distribution, analytical extraction, analysis, and removal techniques

Triclosan (TCS) has been widely used in daily life because of its broad-spectrum antibacterial activities. The residue of TCS and related compounds in the environment is one of the critical environmental safety problems, and the pandemic of COVID-19 aggravates the accumulation of TCS and related compounds in the environment. Therefore, detecting TCS and related compound residues in the environment is of great significance to human health and environmental safety. The distribution of TCS and related compounds are slightly different worldwide, and the removal methods also have advantages and disadvantages. This paper summarized the research progress on the source, distribution, degradation, analytical extraction, detection, and removal techniques of TCS and related compounds in different environmental samples. The commonly used analytical extraction methods for TCS and related compounds include solid-phase extraction, liquid-liquid extraction, solid-phase microextraction, liquid-phase microextraction, and so on. The determination methods include liquid chromatography coupled with different detectors, gas chromatography and related methods, sensors, electrochemical method, capillary electrophoresis. The removal techniques in various environmental samples mainly include biodegradation, advanced oxidation, and adsorption methods. Besides, both the pros and cons of different techniques have been compared and summarized, and the development and prospect of each technique have been given.

Assessment of potential mobility of selected micropollutants in agricultural soils of the Czech Republic using their sorption predicted from soil properties

The sorption of organic contaminants in soils and sediment is a crucial factor affecting their mobility in the vadose zone environment. The Freundlich sorption isotherms were evaluated for eleven micropollutants and eight soils. The highest Freundlich sorption coefficients, K_F, were obtained for triclosan (324 ± 153 cm^3/nμg^1-1/ng^-1) followed by sertraline (120 ± 74), venlafaxine (74.3 ± 41.2), telmisartan (33.3 ± 13.6), atorvastatin (8.66 ± 4.78), bisphenol S (8.03 ± 4.87), lamotrigine (6.92 ± 3.02), 2-phenylbenzimidazole-5-sulfonic acid (3.77 ± 2.25), memantine (3.42 ± 1.64), 1-methyl-1H-benzotriazole (2.05 ± 0.99), and valsartan (0.88 ± 0.89). The K_F values for the individual compounds were correlated with soil properties. Multiple linear regressions were used to derive equations for predicting the K_F values using the soil properties. The first set of equations contained mainly properties with the strongest correlations with the K_F values, e.g., a base cation saturation for positively charged compounds or a hydrolytic acidity for negatively charged compounds. The second set of equations contained properties included in the map of agricultural soils of the Czech Republic. These equations always indicated positive correlations with oxidizable organic carbon and clay content. They also included either a negative or positive correlation with pH_KCl. A positive correlation with pH_KCl was obtained for venlafaxine, memantine, and sertraline, which were mostly positively charged. A negative correlation with pH_KCl was obtained for the remaining compounds. The second set of equations, the soil map, and the database of soil properties were used to predict the K_F value distributions within the Czech agricultural soils. It resulted in similar K_F distributions' patterns for valsartan, lamotrigine, atorvastatin, and telmisartan (with a positive correlation between K_F and hydrolytic acidity), which considerably differed from the K_F patterns for the other compounds. These maps were used to delineate areas with a leaching potential of the compounds toward groundwater that will serve as a tool for assessing a potential groundwater vulnerability.

The effect of disinfectants and antiseptics on co- and cross-selection of resistance to antibiotics in aquatic environments and wastewater treatment plants

The outbreak of the SARS-CoV-2 pandemic led to increased use of disinfectants and antiseptics (DAs), resulting in higher concentrations of these compounds in wastewaters, wastewater treatment plant (WWTP) effluents and receiving water bodies. Their constant presence in water bodies may lead to development and acquisition of resistance against the DAs. In addition, they may also promote antibiotic resistance (AR) due to cross- and co-selection of AR among bacteria that are exposed to the DAs, which is a highly important issue with regards to human and environmental health. This review addresses this issue and provides an overview of DAs structure together with their modes of action against microorganisms. Relevant examples of the most effective treatment techniques to increase the DAs removal efficiency from wastewater are discussed. Moreover, insight on the resistance mechanisms to DAs and the mechanism of DAs enhancement of cross- and co-selection of ARs are presented. Furthermore, this review discusses the impact of DAs on resistance against antibiotics, the occurrence of DAs in aquatic systems, and DA removal mechanisms in WWTPs, which in principle serve as the final barrier before releasing these compounds into the receiving environment. By recognition of important research gaps, research needs to determine the impact of the majority of DAs in WWTPs and the consequences of their presence and spread of antibiotic resistance were identified.

Occurrence and Fate of Triclosan and Triclocarban in Selected Wastewater Systems across Durban Metropolis, KwaZulu-Natal, South Africa

Triclosan (TCS) and triclocarban (TCC) are antimicrobial agents that have been used in personal care and consumer products in the past decades. In this study, influent, effluent, and sludge samples collected in selected wastewater treatment plants across the Durban metropolis were qualitatively and quantitatively investigated. It was revealed that the concentration of TCS ranged from 1.906 to 73.462 µg/L, from 1.732 to 6.980 µg/L, and from 0.138 to 2.455 µg/kg in influent, effluent, and sludge samples, respectively. The concentrations of TCC were found to be between 0.320 and 45.261 µg/L, <LOQ−1.103 µg/L, and from 0.107 to 8.827 µg/kg in the influent, effluent, and sludge samples, respectively. Higher concentrations of TCS as compared with TCC were observed in the aqueous samples. However, the concentrations of TCC in the sludge samples were significantly higher than the level of TCS. More water solubility of TCS could be responsible for the observed trend in the influent and effluent samples, while the trend observed in the sludge could be due to the more hydrophobicity character of TCC. The results of this study indicated that substantial amounts of TCS and TCC are been removed during the treatment process which could be a major reason for the decline in the levels recorded in the effluent samples, therefore, reducing the amount of the TCS and TCC that would eventually end up in the surface rivers. Qualitative analyses of the samples indicated the presence of caffeine, tert-butylhydroquinone, chloroxylenol, phenol, 4-(1,1,3,3-tetramethyl butyl), and dimethyl-bisphenol A. Further investigative ecological risk assessment studies are crucial due to the potential threat the contaminants may pose to aquatic lives and humans.

Transcriptional response of a green alga (Raphidocelis subcapitata) exposed to triclosan: photosynthetic systems and DNA repair

Recent studies show that triclosan (TCS) exposure causes reduction in pigments, suppression of photosynthesis, and induction of oxidative stress at the physiological level, resulting in morphological alteration and growth inhibition in algae including Raphidocelis subcapitata (R. subcapitata, a freshwater model green alga). However, the underlying molecular mechanisms remain to be elucidated, especially at environmentally relevant concentrations. The present study uncovered the transcriptional profiles and molecular mechanisms of TCS toxicity in R. subcapitata using next-generation sequencing. The algal growth was drastically inhibited following a 7-day exposure at both 75 and 100 μg/L TCS, but not at 5 μg/L (environmentally realistic level). The transcriptomic analysis shows that molecular signaling pathways including porphyrin and chlorophyll metabolism, photosynthesis - antenna proteins, and photosynthesis were suppressed in all three TCS treatments, and the perturbations of these signaling pathways were exacerbated with increased TCS exposure concentrations. Additionally, signaling of replication-coupled DNA repair was only activated in 100 μg/L TCS treatment. These results indicate that photosynthesis systems were sensitive targets of TCS toxicity in R. subcapitata, which is distinct from the inhibition of lipid synthesis by TCS in bacteria. This study provides novel knowledge on molecular mechanisms of TCS toxicity in R. subcapitata.

Treatment of triclosan through enhanced microbial biodegradation

Triclosan (TCS) is extensively used in healthcare and personal care products as an antibacterial agent. Due to the persistent and toxic nature of TCS, it is not completely degraded in the biological wastewater treatment process. In this research work, identification of TCS degrading bacteria from municipal wastewater sludge and applying the same as bioaugmentation treatment for wastewater have been reported. Based on the 16S rRNA analysis of wastewater sludge, it was found that Providencia rettgeri MB-IIT strain was active and able to grow in higher TCS concentration. The identified bacterial strain was able to use TCS as carbon and energy source for its growth. The biodegradation experiment was optimized for the operational parameters viz. pH (5-10), inoculum size (1-5% (v/v)) and different initial concentration (2, 5, and 10 mg/L) of TCS. During the TCS degradation process, manganese peroxidase (MnP) and laccase (LAC) enzyme activity and specific growth rate of P. rettgeri strain were maximum at pH=7% and 2% (v/v) inoculum size, resulting in 98% of TCS removal efficiency. A total of six intermediate products were identified from the Liquid chromatography-high-resolution mass spectrometry (LC-HRMS) analysis, and the two mechanisms responsible for the degradation of TCS have been elucidated. The study highlights that P. rettgeri MB-IIT strain could be advantageously used to degrade triclosan present in the wastewater.

Simultaneous quantification of five pharmaceuticals and personal care products in biosolids and their fate in thermo-alkaline treatment

The presence of pharmaceuticals and personal care products (PPCPs) in biosolids applied to farmland is of concern due to their potential accumulation in the environment and the subsequent effects on humans. Thermo-alkaline hydrolysis (TAH) is a method used for greater stabilization of biosolids after anaerobic digestion. In this work, the effect of TAH on five selected PPCPs including fluoroquinolone antibiotics, ciprofloxacin (CIP), and ofloxacin (OFLX), and three commonly used antimicrobial agents, miconazole (MIC), triclosan (TCS) and triclocarban (TCC) was evaluated. At the onset, extraction and analytical methods were optimized for maximum simultaneous recovery and LC-MS quantification of the target PPCPs from both water and biosolids for improved accuracy. The compounds were detected in the range of 54 ± 3 to 6166 ± 532 ng/g in raw biosoilds collected from a local WWTP. Next, batch control adsorption experiments of the selected PPCPs were conducted in various sludges, which indicated about 89%-98% sorption of the PPCPs onto solid phase due to their high octanol-water coefficients. Subsequently, thermo-alkaline (pH 9.5, 75 °C, 45 min) hydrolysis (TAH) was conducted to determine the extent of degradation of these compounds in deionized (DI) water and biosolids due to treatment. The degradation of these compounds due to TAH ranged from 42% to 99% and 37%-41% in pure water and biosolids, respectively, potentially lowering their risk in the environment due to land application. A list of compounds for which the optimized analytical method potentially can be used for detection and quantification in environmental samples is provided in the supporting document.

A Review on the Fate of Legacy and Alternative Antimicrobials and Their Metabolites during Wastewater and Sludge Treatment

Antimicrobial compounds are used in a broad range of personal care, consumer and healthcare products and are frequently encountered in modern life. The use of these compounds is being reexamined as their safety, effectiveness and necessity are increasingly being questioned by regulators and consumers alike. Wastewater often contains significant amounts of these chemicals, much of which ends up being released into the environment as existing wastewater and sludge treatment processes are simply not designed to treat many of these contaminants. Furthermore, many biotic and abiotic processes during wastewater treatment can generate significant quantities of potentially toxic and persistent antimicrobial metabolites and byproducts, many of which may be even more concerning than their parent antimicrobials. This review article explores the occurrence and fate of two of the most common legacy antimicrobials, triclosan and triclocarban, their metabolites/byproducts during wastewater and sludge treatment and their potential impacts on the environment. This article also explores the fate and transformation of emerging alternative antimicrobials and addresses some of the growing concerns regarding these compounds. This is becoming increasingly important as consumers and regulators alike shift away from legacy antimicrobials to alternative chemicals which may have similar environmental and human health concerns.

Comparison of anaerobic, cycling aerobic/anoxic, and sequential anaerobic/aerobic/anoxic digestion to remove triclosan and triclosan metabolites from municipal biosolids

The antimicrobial triclosan (TCS) is a pervasive and persistent environmental micropollutant which can contaminate land, biota, and water through the land application of biosolids. Many existing sludge management techniques have limited effectiveness against TCS and TCS metabolites including triclosan-sulfate (TCS-SO₄). The objective of this study was to evaluate the impacts of different digestion types (anaerobic, aerobic/anoxic, and sequential anaerobic + aerobic/anoxic), temperatures, and digester sludge retention times (SRTs) on the destruction of organic matter, and on TCS/TCS metabolites. Conventional mesophilic anaerobic digesters (AD), room temperature cycling aerobic/anoxic digesters (AERO/ANOX), and sequential AD + AERO/ANOX digesters were all effective in removing organic matter. The optimum single-stage AD, and AERO/ANOX scenarios were both 20-day SRTs which had 52.3 ± 1.4 and 47.1 ± 3.7% chemical oxygen demand (COD) removals, respectively. Sequential AD + AERO/ANOX digesters improved organic matter destruction, removing up to 68.2 ± 2.1% of COD at an 8-day AD + 12-day AERO/ANOX second-stage (mesophilic) SRTs. While AD showed modest levels of TCS removals (all <40%), TCS was substantially more degradable aerobically with AERO/ANOX removing up to 80.3 ± 2.5% of TCS and nearly all TCS-SO₄ entering the digester at a 20-day SRT. Sequential AD + AERO/ANOX removed virtually all TCS-SO₄ entering the system and improved TCS removals from first stage ADs. However, they were less effective than a single-stage AERO/ANOX digester operating at the same overall SRT. These results demonstrate that AERO/ANOX and sequential AD + AERO/ANOX processes could be used to reduce the amount of TCS, TCS-SO₄ and TCS-related compounds in digested sludge, minimizing the environmental burden of the land application of biosolids.

Residuals, sludge, and biosolids: Advancements in the field

Advancements in the field of residuals, sludge, and biosolids have been made in 2019. This review outlines the major contributions of researchers that have been published in peer-reviewed journals and conference proceedings throughout 2019 and includes brief summaries from over 125 articles. The review is organized in sections including life cycle and risk assessments; characteristics, quality, and measurement including micropollutants, nanoparticles, pathogens, and metals; sludge treatment technologies including dewatering, digestion, composting, and wetlands; disposal and reuse including adsorbents, land application and agricultural uses, nutrient recovery, and innovative uses; odor and air emissions; and energy issues.

Comparison of Transcriptomics Changes Induced by TCS and MTCS Exposure in Human Hepatoma HepG2 Cells

Triclosan (TCS) has been a widely used antibacterial agent in medical and personal care products in the last few decades. Methyl TCS (MTCS) is the major biotransformation product of TCS through replacement of the hydroxyl group with methoxy. Previous studies revealed that MTCS showed reduced toxicity but enhanced environmental persistence, when compared with TCS. Till date, the toxicological molecular mechanisms of TCS and MTCS remain to be clarified. This study aimed to investigate the transcriptomic changes in HepG2 cells induced by TCS and MTCS using microarray chips and to identify key target genes and related signal pathways. The microarray data showed that there were 1664 and 7144 differentially expressed genes (DEGs) in TCS- and MTCS-treated groups, respectively. Gene ontology (GO) enrichment and Kyoto Encyclopedia of genes and genomes (KEGG) analysis revealed that TCS and MTCS induced overlapping as well as distinct transcriptome signatures in HepG2 cells. Both TCS and MTCS could result in various biological responses in HepG2 cells mainly responding to biosynthetic and metabolic processes but probably through different regulatory pathways. Among the selected 50 GO terms, 9 GO terms belonging to the cellular component category were only enriched in the MTCS group, which are mainly participating in the regulation of cellular organelle's function. KEGG analysis showed that 19 and 59 pathway terms were separately enriched in TCS and MTCS groups, with only seven identical pathways. The selected 10 TCS-specific signal pathways are mainly involved in cell proliferation and apoptosis, while the selected 10 MTCS-specific pathways mainly take part in the regulation of protein synthesis and modification. The overall data suggested that MTCS induced more enriched DEGs, GO terms, and pathway terms than TCS. In conclusion, compared with TCS, MTCS presents lower polarity and stronger lipophilicity, enabling MTCS to cause more extensive transcriptomic changes in HepG2 cells, activate differentiated signal pathways, and finally lead to differences in biological responses.