Simultaneous analysis of multiple classes of antimicrobials in environmental water samples using SPE coupled with UHPLC-ESI-MS/MS and isotope dilution

The behavior of pharmaceutically active compounds and contrast agents during wastewater treatment - Combining sampling strategies and analytical techniques: A critical review

Increasing consumption of pharmaceuticals and the respective consequences for the aquatic environment have been the focus of many studies over the last thirty years. Various aspects in this field were investigated, considering diverse pharmaceutical groups and employing a wide range of research methodologies. Various questions from the perspectives of different research areas were devised and answered, resulting in a large mix of individual findings and conclusions. Collectively, the results of the studies offer a comprehensive overview. The large variety of methods and strategies, however, demands close attention when comparing and combining information from heterogeneous projects. This review critically examines the application of diverse sampling techniques as well as analytical methods in investigations concerning the behavior of pharmaceutically active compounds (PhACs) and contrast agents (CAs) in wastewater treatment plants (WWTPs). The combination of sampling and analysis is discussed with regard to its suitability for specific scientific problems. Different research focuses need different methods and answer different questions. An overview of studies dealing with the fate and degradation of PhACs and CAs in WWTPs is presented, discussing their strategic approaches and findings. This review includes surveys of anticancer drugs, antibiotics, analgesics and anti-inflammatory drugs, antidiabetics, beta blockers, hormonal contraceptives, lipid lowering agents, antidepressants as well as contrast agents for X-ray and magnetic resonance imaging.

External carbon source as a viable tool for controlling antibiotics and antibiotic resistance genes (ARGs) in effluent: Influence on antibiotic removal and ARGs dissemination

Fluoroquinolone antibiotics and antibiotic resistance genes (ARGs) regarded as emerging contaminants were poorly removed in conventional wastewater treatment plants (WWTPs). Nitrogen-containing heterocyclic organics were found to be biodegraded through denitrification co-metabolism. The feasibility to enhance antibiotics removal efficiency in WWTPs through denitrification co-metabolism needs to be further verified. Meanwhile, due to significant correlation between ARGs profiles and nitrogen removal that was previously observed, the dissemination of ARGs during denitrification was worthy of in-depth understanding. Herein, the antibiotic removal and ARGs dissemination in denitrification co-metabolism condition were investigated with different denitrifying consortiums that acclimated under different conditions in terms of carbon source and the exposure of Ofloxacin (OFL). The results suggest that the removal of OFL can be enhanced by the denitrification co-metabolism. The tolerance to OFL is different among various denitrifying communities. For the denitrifying consortiums acclimated with methanol, long-term exposure to trace OFL (1 μg/L) could reduce the capabilities of removal and tolerance to OFL. On the contrary, those acclimated with sodium acetate (NaAc), the capabilities of removal and tolerance to OFL, were enhanced by long-term exposure to trace OFL. According to the quantitative determination to 384 target genes with high-throughput quantitative PCR, the abundance of ARGs in consortiums greatly increased when exposed to OFL at the concentration of comparable to sewage, which was also much larger than that acclimated with methanol. It can be confirmed and supported by DNA sequencing results that the antibiotic removal and the dissemination of ARGs were determined by microbial community that could be shaped with carbon source. These conclusions suggest that selecting the right external carbon source can be a useful strategy for WWTPs to control antibiotics and ARGs in the effluent. From a new perspective on mitigating ARGs dissemination, NaAc was not an appropriate carbon source.

Removal efficiency of antibiotic residues, antibiotic resistant bacteria, and genes across parallel secondary settling tank and membrane bioreactor treatment trains in a water reclamation plant

Antimicrobial resistance is recognized as a potent threat to human health. Wastewater treatment facilities are viewed as hotspots for the spread of antimicrobial resistance. This study provides comprehensive data on the occurrences of 3 different antibiotic resistant opportunistic pathogens (with resistance to up to 5 antibiotics), 13 antibiotic resistant genes and intI1, and 22 different antimicrobial residues in a large water reclamation plant (176 million gallons per day) that runs a conventional Modified Ludzack-Ettinger (MLE) reactor followed by a secondary settling tank (SST) and membrane bioreactor (MBR) in parallel. All the antibiotic resistant bacteria and most of the antibiotic resistance genes were present in the raw influent, ranging from 2.5 × 102-3.7 × 106 CFU/mL and 1.2× 10-1-6.5 × 1010 GCN/mL, respectively. MBR outperformed the SST system in terms of ARB removal as the ARB targets were largely undetected in MBR effluent, with log removals ranging from 2.7 to 6.8, while SST only had log removals ranging from 0.27 to 4.6. Most of the ARG concentrations were found to have significantly higher in SST effluent than MBR permeate, and MBR had significantly higher removal efficiency for most targets (p < 0.05) except for sul1, sul2, blaOXA48, intI1 and 16S rRNA genes (p > 0.05). As for the antibiotic residues (AR), there was no significant removal from the start to the end of the treatment process, although MBR had higher removal efficiencies for azithromycin, chloramphenicol, erythromycin, erythromycin-H2O, lincomycin, sulfamethoxazole and triclosan, compared to the SST system. In conclusion, MBR outperformed SST in terms of ARB and ARGs removal. However low removal efficiencies of most AR targets were apparent.

Protecting the Last Line of Defense: Analytical Approaches for Sample Preparation and Determination of the Reserve Group of Antibiotics in the Environment

Drug resistance in microorganisms is a serious threat to life and health due to the limited number of antibiotics that show efficacy in treating infections and the difficulty in discovering new compounds with antibacterial activity. To address this issue, the World Health Organization created the AWaRe classification, a tool to support global and national antimicrobial stewardship programs. The AWaRe list categorizes antimicrobials into three groups - Access, Watch, and Reserve - according to their intended use. The Reserve group comprises "last resort" medicines used solely for treating infections caused by bacterial strains that are resistant to other treatments. It is therefore necessary to protect them, not only by using them as prudently as possible in humans and animals, but also by monitoring their subsequent fate. Unmetabolized antibiotics enter the environment through hospital and municipal wastewater or from manure, subsequently contaminating bodies of water and soils, thus contributing to the emergence and spread of antibiotic resistance. This article presents a review of determination methods for the Reserve group of antimicrobials in water, wastewater, and manure. Procedures for extracting and determining these substances in environmental samples are described, showing the limited research available, which is typically on a local level.

Metallo-β-lactamases immobilized by magnetic zeolitic imidazolate frameworks-8 for degradation of β-lactam antibiotics in an aqueous environment

Residual antibiotics in nature are an important cause of antimicrobial drug resistance, and how to deal with residual β-lactam antibiotics in aqueous environments has become an urgent issue. In this work, magnetic zeolitic imidazolate frameworks-8 (ZIF-8) for immobilizing metallo-β-lactamases (MBLs), or Fe3O4@ZIF-8@MBLs, were successfully synthesized using the one-pot method in aqueous solution. The morphology and chemical structure of Fe3O4@ZIF-8@MBLs were characterized by scanning electron microscopy, energy dispersive spectra, X-ray diffraction, infrared spectra, physical adsorption, and zeta potential. Further, the degradation performance of Fe3O4@ZIF-8@MBLs for β-lactam antibiotics (penicillin G, cefoperazone, meropenem) in an aqueous environment was investigated by UV-visible absorption spectrophotometry. The results indicated that Fe3O4@ZIF-8@MBLs, compared to control ZIF-8, exhibited superior degradation ability, excellent reusability, and better stability under several harsh conditions. The strategy of combining ZIF-8 and MBLs to form magnetic porous polymers may be suitable for removing β-lactam antibiotics from an aqueous environment. This work provided an original insight into future studies on the degradation of β-lactam antibiotics employing MBLs immobilized by magnetic metal-organic frameworks.

Co-occurrence pattern of ARGs and N-functional genes in the aerobic composting system with initial elevated temperature

Animal manure is known to harbor antibiotic resistance genes (ARGs). Aerobic composting is a prevalent cost-effective and sustainable method to treat animal waste. However, the effect of initially elevated temperature on antibiotic resistome during the composting process is unclear. In this study composting was subjected to initial external heating (EHC) for a period of 5 days compared to conventional composting (CC). After composting ARGs abundance was significantly reduced by 2.43 log in EHC and 1.95 log in CC. Mobile genetic elements (MGEs) also exhibited a reduction of 1.95 log in EHC and 1.49 log in CC. However, during the cooling phase, the genes resisting macrolide lincosamide and streptogramin B (MLSB) rebounded by 0.04 log in CC. The potential human pathogenic bacteria Pseudomonas (41.5-61.5%) and Actinobacteria (98.4-98.8%) were significantly reduced in both treatments and the bulk of targeted antibiotics were eliminated by 80.74% in EHC and 68.98% in CC. ARGs and N-functional genes (NFGs), mainly denitrification genes, were carried by the same microbial species, such as Corynebacterium sp. and Bacillus sp., of the dominant phylum. Redundancy analysis (RDA) revealed that CC microbial communities played a key role in the enrichment of ARGs while in EHC the variation of ARGs was attributed to the composting temperature. The number of high-risk ARGs was also lower in EHC (4) compared with CC (6) on day 30. These results provide insight into the effects of an initially enhanced temperature on ARGs removal and the relationship between ARGs and NFGs during the composting process.

Composting effect and antibiotic removal under a new temperature control strategy

The main objective of this study was to investigate the feasibility of a new temperature control strategy in the co-composting process to accelerate operation cycle and remove antibiotics from mixed organic wastes. The evaluation of the composting process showed that composting with temperature control (TC) was completed within 14 days. The final compost of TC exhibited a 10% higher degradation of organic matters, more humus formation and 11.25% lower heavy metals concentration than conventional composting (CC), which fully met the Chinese National Agricultural Organic Fertilizer Standard requirements. The degradation extent and kinetic of macrolides, tetracyclines, sulfonamides and fluoroquinolones showed that the removal efficiency of total antibiotics in TC was 23.58% higher than CC, with less half-life, which was significantly correlated with higher temperature. Particularly, the highest removal was observed for sulfonamides (87.45%) in TC, the half-life of which was reduced by 75.95% compared with CC. The higher degradation rate was attributed to enhanced decomposition of unstable antibiotics and degrading activity of microbes at high temperature. The microbiological analysis showed that the external heating led to a distinct composition and succession of bacterial community in TC. Firmicutes, Proteobacteria, Actinobacteriota and Bacteroidota were dominant and the emergence of Patescibacteria and Chloroflexi at cooling period in TC proved that the later composting environment was in an oligotrophic state. Current research provided a promising rapid composting approach for high-quality fertilizer production and antibiotic management in organic waste disposal.

Simultaneous electrochemical removal of Microcystis aeruginosa and sulfamethoxazole and its ecologic impacts on Vallisneria spiralis

In this study, the simultaneous removal effects of electrochemical oxidation with boron-doped diamond anodes at different current densities were tested on Microcystis aeruginosa and sulfamethoxazole. Flow cytometry and non-invasive micro-test technology were applied to study the physiological states of M. aeruginosa and Vallisneria spiralis leaf cells. As the current density increased, the degradation effect of electrochemical oxidation on sulfamethoxazole and microcystin-LR increased and exceeded 60% within 6 h. In addition, population density of M. aeruginosa, fluorescence response of chlorophyll a, and cytoplasmic membrane integrity decreased, whereas the proportion of cells with excessive accumulation of intracellular reactive oxygen species (ROS) increased. The effect of electrochemical oxidation on the cell population of M. aeruginosa continued after the power was turned off. The physiological state of V. spiralis leaf cells was not severely affected at 10 mA/cm² for 24 h. Higher current intensity and longer electrolysis time would induce apoptosis or necrosis. In order to achieve a higher target pollutant removal effect and simultaneously avoid damage to the lake ecosystem, the current intensity of the electrochemical oxidation device should not exceed 10 mA/cm², and a single electrolysis treatment should range from 6 h to 24 h.

Size-dependent adsorption of waterborne Benzophenone-3 on microplastics and its desorption under simulated gastrointestinal conditions

Microplastics (MPs) are global pollutants with heightened environmental and health concerns in recent years because of their worldwide distribution across aquatic environments, ability to load chemical contaminants and the potential for ingestion by animals, including human. In this study, three commonly used and environmentally detected plastics, i.e. polystyrene, polyethylene, polypropylene with sizes of 550, 250 and 75 μm, plus two submicron-sized polystyrene microplastics (5 and 0.5 μm) were assessed as solid adsorbents for a prevalent UV filter, benzophenone-3 (BP-3). The affinity and process of adsorption exhibited differentials among different sizes and types of MPs. Apparent desorption of BP-3 from MPs under simulated gastrointestinal conditions was not significantly enhanced, which might be due to the presence of the enzyme proteins, indicating potential risk of the contaminants carried by MPs. The desorption of BP-3 from MPs was affected by the size, type of MPs and the components of the gastrointestinal fluid.

Simultaneous Determination of Seven Antibiotics and Five of Their Metabolites in Municipal Wastewater and Evaluation of Their Stability under Laboratory Conditions

The selection and spread of antibiotic resistance poses risks to public health by reducing the therapeutic potential of antibiotics against human pathogens. Wastewater-based epidemiology (WBE) is potentially the most reliable approach to estimate antibiotics use. Previous WBE studies used parent antibiotics as biomarkers, which may lead to overestimation since parent antibiotics may be directly disposed of. Using metabolites as biomarkers can avoid this drawback. This study developed a simultaneous solid-phase extraction coupled with ultra-high-performance liquid chromatography tandem mass spectrometry method for analyzing 12 antibiotics and human metabolites in wastewater to help assess health risk. Optimum conditions were achieved using a PEP cartridge at pH 3.0. The extraction efficiencies were 73.3~95.4% in influent and 72.0~102.7% in effluent for most of the target analytes. Method detection limit ranged from 0.1 to 1.5 ng/L for influent wastewater and 0.03 to 0.7 ng/L for effluent wastewater. A stability experiment showed that sulfonamide parents and their metabolites were stable at 4 °C, −20 °C and −80 °C, while macrolides metabolites were more stable than their corresponding parents at 4 °C and −20 °C. Finally, the method was applied to measure these analytes in wastewater samples collected from three Beijing WWTPs and to derive apparent removal rates. All metabolites were detected in wastewater samples with concentrations ranging from 1.2 to 772.2 ng/L in influent, from <MDL to 235.6 ng/L in effluent. The apparent removal rates of five metabolites were above 72.6%. These results set a solid foundation for applying WBE to evaluate antibiotics use and its public health effects.

A rapid multiclass method for antibiotic residues in goat dairy products by UPLC-quadrupole/electrostatic field orbitrap high-resolution mass spectrometry

Background

Sulfanilamides, quinolones, nitroimidazoles, tetracyclines, cephalosporins, macrolides, and β-lactam are common tools in agriculture and can be found in animal-based foods such as goat milk and goat dried milk. To evaluate the risk of these species, reliable analytical methods are needed for accurate concentration determination, especially in goat milk and goat dried milk.

Method

We describe a method based on PRiME extraction coupled with UPLC-quadrupole/electrostatic field orbitrap high-resolution mass spectrometry to accomplish this task.

Result

Under optimal conditions, the limit of quantification for all antibiotics was 0.5–100 μg/L in goat milk and goat dried milk samples. The recoveries were 60.6–110.0% for goat milk and 60.1–109.6% for goat dried milk with a coefficient of variation less than 15%. The detection limits were 0.5–1.0 μg/kg. The limits of quantification for the analytes were 5.0–10.0 μg/kg. Finally, the method was used to screen veterinary antibiotics in 50 local goat milk and goat dried milk samples; metronidazole and enrofloxacin were detected in goat milk.

Conclusion

This method offers good reliability and the capacity for simultaneous detection can be used to detect residual contents and evaluate health risks in goat milk and goat dried milk.

Quality assessment of environmental water by a simple and fast non-ionic hydrophobic natural deep eutectic solvent-based extraction procedure combined with liquid chromatography tandem mass spectrometry for the determination of plastic migrants

A non-ionic hydrophobic natural deep eutectic solvent (HNADES) based on thymol and menthol was proposed for the liquid-liquid microextraction of fourteen phthalates and one adipate from environmental water samples. Separation, identification, and quantification were achieved by ultra-high-performance liquid chromatography coupled to tandem mass spectrometry. The main factors affecting the extraction efficiency were thoroughly studied. Sample pH of 8 and 100 μL of thymol:menthol at molar ratio 2:1 were selected as the best conditions, while ionic strength and type of dispersant solvent were not relevant for the extraction of the target compounds. The whole methodology was validated for treated wastewater, runoff, and pond water matrices, using di-n-butyl phthalate-3,4,5,6-d₄ and dihexyl phthalate-3,4,5,6-d₄ as surrogates. Recovery ranged from 70 to 127% with relative standard deviation values lower than 14%. Limits of quantification of the method were in the range 0.042-0.425 μg/L for treated wastewater, 0.015-0.386 μg/L for runoff, and 0.013-0.376 μg/L for pond water. The methodology was applied for the analysis of real treated wastewater, runoff, and pond water samples from different places of Tenerife and Gran Canaria (Canary Islands) finding the presence of diethyl phthalate, diallyl phthalate, dipropyl phthalate, benzylbutyl phthalate, di-n-butyl phthalate, bis-(2-n-butoxyethyl) phthalate, di-n-pentyl phthalate, dicyclohexyl phthalate, and bis-(2-ethylhexyl) phthalate at concentrations between 105.2 and 3414 ng/L.

Multi-phase distribution, spatiotemporal variation and risk assessment of antibiotics in a typical urban-rural watershed

The widespread consumption and continuous discharge of antibiotics have threatened the ecological health of urban-rural watershed. In this study, multi-phase distribution, spatiotemporal variation and ecological risk of 18 antibiotics in rivers and lakes from Suzhou City were investigated based on urban-rural gradient. The total antibiotic concentration in surface water, suspended particulate matter (SPM) and sediments was 39.28-2578 ng/L, 6.16-171.09 ng/L and 12.67-2249 ng/g, respectively. High detection frequency (>76%) and concentration of antibiotics in multi-phase suggested universal pollution. Quinolones (QNs) and tetracycline (TCs) were the dominant antibiotics detected. The partitioning coefficient (K_P) value of SPM-water was 1.43-29.93 times larger than sediment-water, indicating that SPM can greatly affect the fate and distribution of antibiotics. Significant positive correlations between antibiotics and environmental parameters (e.g. TOC, TP and TN) revealed combined contamination and similar pollution sources. Antibiotic pollution exhibited evident spatiotemporal variation. For spatial variation, urban area showed more serious antibiotic pollution and greater ecological risk than rural and suburb areas, especially for sediments. Besides, antibiotic level and risk in rivers were higher than lakes. For seasonal variation, in case of surface water, rural area exhibited higher content in winter, while greater content was detected in autumn and spring in urban and suburb areas, respectively. The highest antibiotic content in SPM and sediments was all measured in winter owing to weak degradation ability. Ecological risk assessment based on risk quotients (RQs) indicated that norfloxacin (NFX), ciprofloxacin (CFX) and anhydroerythromycin (ETM-H₂O) in surface water presented medium to high risk throughout the entire year, while sulfadiazine (SDZ) and enrofloxacin (EFX) in sediments showed higher accumulation potential. Thus, these five antibiotics were selected as the priority antibiotics for pollution control. In short, this study improves the understanding of antibiotic fates in the urban-rural watershed and provides scientific basis for the authorities to regulate antibiotic pollution.

Determination of estrogens by solid-phase quadruplex stable isotope dansylation coupled with liquid chromatography-high resolution mass spectrometry in environmental samples

Estrogens distribute widely in the environment as endocrine-disrupting chemicals (EDCs), which have to be monitored to evaluate their environmental impact. Aim to improve the analytical throughput of liquid chromatography-high resolution mass spectrometry (LC-HRMS), a quadruplex stable isotope dansylation method was developed, with which three real samples could be quantitatively analyzed in one injection. As the estrogens were at trace level in complex matrices, magnetic solid-phase extraction (MSPE) was applied to enrich these analytes and remove the interfaces. By integrating MSPE and quadruplex stable isotope dansylation, a solid-phase quadruplex labeling method was developed for the LC-HRMS analysis of estrogen analogues. For the tested seven estrogens, the developed method showed low detection limits (0.1-0.5 ng/L for pond water and 0.01-0.05 μg/kg for poultry manure), good precision (RSD < 5.5%) and accuracy (96.8-108.3%). The method was applied in the determination of estrogens in environmental samples, and the results revealed that all the tested estrogens were present in the estuary water (unquantifiable to 71.2 ng/L) and chicken manure (undetectable to 25.43 μg/kg).

A sensitive and accurate method for simultaneous analysis of algal toxins in freshwater using UPLC-MS/MS and 15N-microcystins as isotopically labelled internal standards

The development of analytical methods for the detection and accurate quantification of algal toxins is of importance to assess the health risk of exposure to algal toxins in freshwater sources. This study established a sensitive and accurate analytical method for the quantification of 13 algal toxins (microcystins and nodularin) based on solid phase extraction (SPE) coupled with UPLC-MS/MS, in which ¹⁵N-microcystins were used as surrogate/internal standards. SPE method was optimized to extract the target algal toxins in freshwater samples. Good SPE efficiencies (84-96%) were achieved for the overwhelming majority of the investigated algal toxins when SPE was performed using HLB (500 mg, 6 mL) under alkaline conditions (pH 11). An accurate quantitative analysis of the algal toxins in real freshwater samples was performed by using ¹⁵N-labelled microcystins as isotopically labelled internal standards (ILISs), which compensated for the loss of target toxins during the whole analytical process. In addition, ILISs also helped to correct the effects of environmental matrices and instrument fluctuation in UPLC-MS/MS analysis. The limit of method quantification (MQL) for the algal toxins was <2.0 ng/L that is sensitive enough to quantify extremely low levels of target toxins in freshwater samples.

Quantification of cylindrospermopsin, anatoxin-a and homoanatoxin-a in cyanobacterial bloom freshwater using direct injection/SPE coupled with UPLC-MS/MS

Analytical methods based on direct injection (DI) and solid phase extraction (SPE) coupled with ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC- MS/MS) were developed for the determination of anatoxin-a (ATX-a), cylindrospermopsin (CYN), and homoanatoxin-a (HATX-a) in freshwater samples impacted with cyanobacterial blooms. The presence of CYN in freshwater samples was detected and quantified based on direct injection method, while ATX-a and HATX-a could be determined by both DI and SPE-based methods. Matrix effects (ME) on the signal intensity of the cyanotoxins were systematically evaluated for both direct injection and SPE extract samples. CYN, ATX-a, and HATX-a suffered a significant suppression during UPLC-MS/MS. The selection of internal standards (ISs) for compensating/correcting the losses of target cyanotoxins during sample preparation and matrix effects in UPLC-MS/MS analyses were systematically evaluated. Acetaminophen-d₄ (an isotopically labelled acetaminophen) is a suitable internal standard for correcting the ME on the signal intensity of ATX-a and HATX-a, while the use of L-phenylalanine-d₅ or caffeine-d₉ as IS for correcting ME of these toxins was not efficient, as expected. The method detection limit (MDL) for the target cyanotoxins ranged from 0.6 to 15 ng/L, which is sensitive enough to detect the presence of these toxins in cyanobacterial bloom freshwater. The developed methods were successfully applied for routine monitoring of the occurrence of these cyanotoxins in a local water body. Monitoring results depicted that ATX-a, CYN and HATX-a were ubiquitously detected in water samples, at concentrations ranging from 70 to 24,600 ng/L.

Multi-class analysis of 46 antimicrobial drug residues in pond water using UHPLC-Orbitrap-HRMS and application to freshwater ponds in Flanders, Belgium

Increasing anthropogenic pressure and agricultural pollution raises concerns regarding antimicrobial resistance and biodiversity loss in aquatic environments. In order to protect and restore water resources and biodiversity, antimicrobial drug residues should be monitored in all aquatic environments including pond water. Consequently, the objective of this research was to develop and validate a novel multi-residue method for the simultaneous quantification of 46 targeted human and veterinary antimicrobial drugs in pond water. A suitable extraction method based on solid-phase extraction (SPE) was developed, assisted by a fractional factorial design. A broad polarity range of compounds was covered (log P from -4.05 to 4.38), including major representatives of the following classes: sulfonamides, tetracyclines, quinolones, macrolides, lincosamides, nitrofurans, penicillins, cephalosporins, diaminopyrimidines, pleuromutilins and phenicols. All analytes were separated using ultra-high performance liquid chromatography (UHPLC) and detected in full-scan by Orbitrap high resolution mass spectrometry (Orbitrap-HRMS). Good linearity was obtained for all compounds with R² ≥ 0.993 and goodness-of-fit coefficient (g) ≤ 11.56%. Method detection limits ranged from 10 to 50 ng L^-1 and method quantification limits were 50 ng L^-1 for all compounds. Acceptable values were obtained for within-day and between-day apparent recoveries (i.e. between 50 and 120%), precision (< 30% and < 45%) and measurement uncertainty (< 50%). Targeted analysis of 18 freshwater ponds throughout Flanders was performed to demonstrate the applicability of the newly developed UHPLC-HRMS method. Overall, 20 antimicrobial drugs were detected with highest concentrations observed for tetracyclines and their transformation products ranging between 51 and 248 ng L^-1. Finally, suspect screening was performed suggesting the presence of 14 additional pharmaceuticals including 3 antimicrobial degradation products (e.g. apo-oxytetracycline, amoxicillin penicilloic acid and penilloic acid) and 11 pesticides.

Determination of 19 anthelmintics in environmental water and sediment using an optimized PLE and SPE method coupled with UHPLC-MS/MS

A sensitive quantification method using pressurized liquid extraction (PLE) and solid phase extraction (SPE) coupled with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was developed for determination of 19 anthelmintic drugs (ADs) belonging to seven structural groups (Benzimidazoles, Diphenylsulfides, Imidazothiazoles, Hexahydropyrazines, Macrocylic lactones, Salicylanilides, Tetrahydropyrimidines) in environmental water and sediment samples. Eleven SPE cartridges, sample pH, elution solvents were tested to determine the optimal conditions for extraction. Among these investigated SPE types, the best recoveries for 19 target ADs were obtained from Oasis HLB cartridge with 37-102%, 45-103%, 37-88%, 28-82% and 31-90% for spiked river water, tap water, rainwater, wastewater, and sediment respectively (with RSD < 15%), except for closantel. The 19 ADs were separated within 10 min by a BEH C18 column and monitored in both positive and negative ions modes with switching electrospray ionization source. The cross-talk interferences were solved by identification of secondary mass spectrum of substances through MRM-IDA-EPI scanning using Qtrap. These interference peaks could be efficiently eliminated by setting MRM segments or using Qtrap to obtain tertiary fragmented information. The developed methods were satisfactory in terms of linearity, accuracy, and precision, and used eight isotopically labeled compounds as internal standards to correct matrix effects. Method quantification limit (MQL) for 19 ADs was below 1.1 ng/L, 0.4 ng/L, 5.4 ng/L and 2.3 ng/g for river water, tap water, wastewater, and sediment, respectively. The validated method was successfully used to investigate the occurrence of anthelmintics in water and sediment samples from Chengdu, China. All ADs were detected in environment with the concentrations at ng/L level.

Factorial Design Optimisation of Solid Phase Extraction for Preconcentration of Parabens in Wastewater Using Ultra-High Performance Liquid Chromatography Triple Quadrupole Mass Spectrometry

Background:

Parabens are synthetic esters used extensively as preservatives and/or bactericides in personal care personal products.

Objective:

Development and validation of a novel robust chemometric assisted analytical technique with superior analytical performances for the determination of ethylparaben, methylparaben and propylparaben, using simulated wastewater matrix.

Methods:

An automated Solid Phase Extraction (SPE) method coupled with liquid chromatographymass spectrometry was applied in this study. A gradient elution programme comprising of 0.1% formic acid in deionised water (A) and 0.1% formic acid in Methanol (B) was employed on a 100 x 2.1 mm, 3.0 μm a particle size biphenyl column. Two-level (2k) full factorial design coupled with response surface methodology was used for optimisation and investigation of SPE experimental variables that had the most significant outcome of the analytical response.

Results:

According to the analysis of variance (ANOVA), sample pH and eluent volume were statistically the most significant parameters. The method developed was validated for accuracy, precision, Limits of Detection (LOD) and Limit of Quantification (LOQ) and linearity. The LOD and LOQ established under those optimised conditions varied between 0.04-0.12 μgL−1 and 0.14-0.40 μgL−1 respectively. The use of matrix-matched external calibration provided extraction recoveries between 78-128% with relative standard deviations at 2-11% for two spike levels (10 and 100 μgL-1) in three different water matrices (simulated wastewater, influent and effluent water).

Conclusion:

The newly developed method was applied successfully to the analyses of parabens in wastewater samples at different sampling points of a wastewater treatment plant, revealing concentrations of up to 3 μgL−1.

TiO2 photocatalysis under natural solar radiation for the degradation of the carbapenem antibiotics imipenem and meropenem in aqueous solutions at pilot plant scale

This paper deals with the removal of two last-resort antibiotics, namely imipenem and meropenem, in aqueous solutions employing heterogeneous photocatalysis with TiO₂ under natural solar radiation at pilot plant scale. It was found that TiO₂ photocatalysis is a very efficient technique for the degradation of both compounds in aqueous solutions, albeit it's relatively low quantum efficiency. At the experimental conditions employed in the present work (compound parabolic collectors photoreactor) the optimal TiO₂ concentration was about 50 mg L^-1. Experiments conducted in various aqueous matrices lead to the conclusion that the method can be applied to real aqueous matrices, such as natural waters and wastewaters. The comparison of TiO₂ photocatalysis and natural photolysis showed an important decrease of the accumulated energy required to achieve the complete removal of both antibiotics which, in terms of normalized illumination time (t_30W), represented a reduction of 50 min for imipenem and 60 min for meropenem.

Occurrence and risk assessment of multiple classes of antibiotics in urban canals and lakes in Hanoi, Vietnam

Very little information on the occurrence and risk assessment of antibiotics in the aquatic environment is reported for Vietnam, where antibiotics are assumed to be omnipresent in urban canals and lakes at high concentrations due to the easy accessibility of antibiotics without doctor prescription. This study provides comprehensive analysis of the occurrence of 23 antibiotics in urban canals (To Lich and Kim Nguu) and lakes (West Lake, Hoan Kiem, and Yen So) in Hanoi, Vietnam. Of these 23 antibiotics, 18 were detected in urban canals at above 67.9% detection frequency (DF). The concentrations of detected antibiotics were in the range from below quantification limit (MQL) to almost 50,000 ng/L, depending on the compound and sampling site. In urban canals, median concentration of amoxicillin, erythromycin, and sulfamethoxazole was >1000 ng/L while other antibiotics such as ampicillin, chloramphenicol, clindamycin, sulfamethazine, tetracycline, tylosin and vancomycin were detected at median concentrations of <100 ng/L. Similarly, 16 target antibiotics were also detected in urban lakes. Macrolides (azithromycin, clarithromycin, and erythromycin-H₂O), fluoroquinolones (enrofloxacin and ofloxacin), lincosamides (clindamycin and lincomycin), and trimethoprim were ubiquitously detected in urban lakes (DF = 100%). In this study, potential risks of antibiotics in the investigated urban canals and lakes were assessed based on the predicted no-effect concentration (PNEC) from the existing literature for antibiotic resistance selection (PNEC_ARM) and ecological toxicity to aquatic organisms (PNEC_Ecotox). Ampicillin, amoxicillin, azithromycin, ciprofloxacin, clarithromycin, enrofloxacin, erythromycin, ofloxacin, tetracycline, and trimethoprim were found in the investigated urban canals at concentrations exceeding their PNEC_ARM and PNEC_Ecotox. Similarly, most of the target antibiotics (i.e. amoxicillin, ciprofloxacin, clarithromycin, clindamycin, enrofloxacin, erythromycin, lincomycin, ofloxacin, sulfamethoxazole, tetracycline, trimethoprim and tylosin) were detected in the investigated urban lakes at concentrations close to or exceeding PNEC_Ecotox for aquatic organisms. Further investigations on the occurrence and fate of antibiotic residues and antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in surface waters are recommended.

Graphene Oxide-Based Dispersive-Solid Phase Extraction for Preconcentration and Determination of Ampicillin Sodium and Clindamycin Hydrochloride Antibiotics in Environmental Water Samples Followed by HPLC-UV Detection

In this work, a reusable graphene oxide (GO) based dispersive-solid phase extraction (d-SPE) was synthesized and used for the analysis of trace ampicillin sodium (AMP) and clindamycin hydrochloride (CLI) in water samples followed by high performance liquid chromatography-UV detection (HPLC-UV). Batch experiments were conducted to investigate the effects of pH and volume of the sample solution, contact time, adsorption isotherms, temperature, and desorption conditions. The maximum adsorption capacities of AMP and CLI on GO nanosheets were found to be 33.33 mg g^-1 and 47 mg g^-1, respectively. The adsorption isotherm data can be well fitted by Temkin (AMP and CLI) and Freundlich (AMP), and the adsorption process followed the pseudo-second-order model. The thermodynamic parameters were calculated, indicated that the adsorption process of both analytes were spontaneous and exothermic. In addition, the d-SPE following HPLC analyses showed good linearity in the range of 0.5-200 ng mL^-1 (R²= 0.999) for AMP and 1-200 ng mL^-1 (R²= 0.999) for CLI, with LOD of 0.04 and 0.24 ng mL^-1 for AMP and CLI, respectively. The percent of extraction recoveries, intra and inter-day precisions (expressed as RSD %, n = 3) were in the range of 96.4-101.6%, 2.2-3.0, and 3.7-4.7 for AMP as well as 94.2-98.6%, 2.2-3.8, and 3.5-4.6 for CLI, respectively. The preconcentration factor of 20 was achieved for both analytes. From these results, it can be concluded that the validated method is a simple, cost-effective and repeatable method for analysis of AMP and CLI in water samples and provide a new platform for antibiotics decontamination.

Emerging contaminants in wastewater, stormwater runoff, and surface water: Application as chemical markers for diffuse sources

Diffuse sources of pollution such as sewer leakages, sewer overflows, illicit discharges and stormwater runoff affect the urban surface water quality but often remain unknown. Therefore, the development of chemical markers for identifying and characterizing the origin of diffuse sources of pollution in urban surface waters is a requisite for protecting and managing urban water resources. In this study, the occurrence of 31 emerging contaminants (ECs) in untreated wastewater, treated wastewater, urban stormwater runoff, agricultural stormwater runoff, and freshwater bodies was investigated. Artificial sweeteners (ASs), pharmaceuticals and personal care products (PPCPs) were more frequently detected in the collected water samples. In raw wastewater, 21 target ECs were detected 100% in the collected samples with median concentrations ranging from 49.6 to 77,721 ng/L, while in freshwater bodies, only 13 compounds were found with detection frequency >50%. The median concentration of the majority of detected ECs in freshwater samples was below 100 ng/L. The suitability of ECs as chemical markers of diffuse sources in an urban watershed was assessed using a suite of criteria, including the detection frequency (DF), detection ratio (DR) (i.e. the ratio between median concentration and method quantification limit of a compound) and attenuation rates (i.e., biodegradation, sorption and abiotic degradation) in wastewater treatment processes. In addition, we propose a new key criterion, the concentration ratio (CR) of labile to conservative compounds, to evaluate the applicability of suitable chemical markers for source tracking. Using this new set of criteria (i.e. CR, DF, DR and attenuation rates), our analysis showed that among the investigated ECs, only acesulfame (ACE), acetaminophen (ACT), cyclamate (CYC), saccharin (SAC) were suitable as chemical markers of diffuse sources in surface waters. For caffeine (CF), N,N-diethyl-meta-toluamide (DEET), crotamiton (CTMT), triclocarban (TCC) and triclosan (TCS), their median concentration ratio to sucralose (SUC) in water bodies was consistently higher than that in raw wastewater, suggesting that these compounds might be unsuitable as chemical markers of sewage leakage in surface waters for this study area.

Towards a harmonized method for the global reconnaissance of multi-class antimicrobials and other pharmaceuticals in wastewater and receiving surface waters

Antimicrobial resistance is a worldwide problem that is both pressing and challenging due to the rate at which it is spreading, and the lack of understanding of the mechanisms that link human, animal and environmental sources contributing to its proliferation. One knowledge gap that requires immediate attention is the significance of antimicrobial residues and other pharmaceuticals that are being discharged from wastewater treatment plants (WWTPs) on the dissemination of antimicrobial resistance in the environment. In this work we provide an approach to develop a harmonized analytical method for 8 classes of antimicrobials and other pharmaceuticals that can be used for global monitoring in wastewater and receiving waters. Analysis of these trace organic chemicals in the influent and effluent wastewater, and in the respective upstream and downstream receiving waters from different countries across the globe is not trivial. Here, we demonstrated that sample preparation using solid-phase extraction (SPE) not only provides a convenient and cost-effective shipping of samples, but also adds stability to the analytes during international shipping. It is important that SPE cartridges are maintained at cold temperature during shipment if the duration is longer than 7 days because a significant decrease in recoveries were observed after 7 days in the cartridges stored at room temperature, especially for sulfonamides and tetracyclines. To compensate for sample degradation during shipment, and matrix effects in liquid chromatography/mass spectrometry, the use of stable isotope labeled compounds should be employed when available and affordable. The importance of applying a defined tolerance for the ion ratios (Q/q) that have been optimized for wastewater and surface water is discussed. The tolerance range was set to be the mean Q/q of the analyte standard at various concentrations ±40% for the influent, and ±30% for the effluent, upstream, and downstream samples; for tetracyclines and quinolones, however, the tolerance range was ±80% in order to minimize false negative and false positive detection. The optimized procedures were employed to reveal differences in antimicrobial and pharmaceutical concentrations in influent, effluent, and surface water samples from Hong Kong, India, Philippines, Sweden, Switzerland, and United States. The antimicrobials with the highest concentrations in influent and effluent samples were ciprofloxacin (48,103 ng/L, Hong Kong WWTP 1) and clarithromycin (5178 ng/L, India WWTP 2), respectively. On the other hand, diclofenac (108,000 ng/L, Sweden WWTP 2), caffeine (67,000 ng/L, India WWTP 1), and acetaminophen (28,000 ng/L, India WWTP 1) were the highest detected pharmaceuticals in the receiving surface water samples. Hong Kong showed the highest total antimicrobial concentrations that included macrolides, quinolones, and sulfonamides with concentrations reaching 60,000 ng/L levels in the influent. Antidepressants were predominant in Sweden, Switzerland, and the United States.

Occurrence and bioconcentration of micropollutants in Silver Perch (Bidyanus bidyanus) in a reclaimed water reservoir

This study examined the occurrence of 49 micropollutants in reclaimed water and Silver Perch (Bidyanus bidyanus) living in a reclaimed water reservoir. The numbers of micropollutants detected in reclaimed water, Silver Perch liver, and Silver Perch flesh were 20, 23, and 19, respectively. Concentrations of all micropollutants in reclaimed water, except benzotriazole, were well below the Australian Guideline for Recycled Water (AGRW) values for potable purposes. The concentration of benzotriazole in reclaimed water was 675 ± 130 ng/L while the AGRW value for this compound was 7 ng/L. Not all micropollutants detected in the water phase were identified in the Silver Perch flesh and liver tissues. Likewise, not all micropollutants detected in the Silver Perch flesh and liver were identified in the reclaimed water. In general, micropollutant concentrations in the liver were higher than in the flesh. Perfluorooctane sulfonate (PFOS) was detected at a trace level in reclaimed water well below the AGRW guideline value for potable purposes, but showed a high and medium bioconcentration factor in Silver Perch liver and flesh, respectively. In addition, the risk quotient for PFOS was medium and high when considering its concentration in Silver Perch liver and flesh, respectively. Results reported here highlight the need to evaluate multiple parameters for a comprehensive risk assessment. The results also single out PFOS as a notable contaminant of concern for further investigation.

Additional reduction of antibiotic resistance genes and human bacterial pathogens via thermophilic aerobic digestion of anaerobically digested sludge

Thermophilic aerobic digestion (TAD) was applied to further reduce ARGs and heavy metal resistance genes (HMRGs) as well as class 1 integrons (intI1) in sludge from anaerobic digestion (AnD). Unlike after AnD, there was no enrichment of ARGs, HMRGs and intI1 after TAD. Residual gene fractions of intI1 and total ARGs (sum of targeted ARGs) were 0.03 and 0.08, respectively. Two kinetic models (Collins-Selleck and first-order) described the decay patterns of targeted genes, revealing rapid removal of intI1 during TAD. After TAD, the relative abundance of human bacterial pathogens (HBPs) and the numbers of HBPs species decreased to approximately 68% and 64% compared to anaerobically digested sludge, respectively. Thus, TAD, subsequent to AnD, may possess high potential for reducing biological risks resulting from ARGs, HMRGs, intI1 and HBPs in sewage sludge.

Monitoring Antimicrobial Resistance Dissemination in Aquatic Systems

This special issue on Antimicrobial Resistance in Environmental Waters features 11 articles on monitoring and surveillance of antimicrobial resistance (AMR) in natural aquatic systems (reservoirs, rivers), and effluent discharge from water treatment plants to assess the effectiveness of AMR removal and resulting loads in treated waters. The occurrence and distribution of antimicrobials, antibiotic resistant bacteria (ARB), antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) was determined by utilizing a variety of techniques including liquid chromatography—mass spectrometry in tandem (LC-MS/MS), traditional culturing, antibiotic susceptibility testing (AST), molecular and OMIC approaches. Some of the key elements of AMR studies presented in this special issue highlight the underlying drivers of AMR contamination in the environment and evaluation of the hazard imposed on aquatic organisms in receiving environments through ecological risk assessments. As described in this issue, screening antimicrobial peptide (AMP) libraries for biofilm disruption and antimicrobial candidates are promising avenues for the development of new treatment options to eradicate resistance. This editorial puts into perspective the current AMR problem in the environment and potential new methods which could be applied to surveillance and monitoring efforts.

Removal of antibiotic residues, antibiotic resistant bacteria and antibiotic resistance genes in municipal wastewater by membrane bioreactor systems

Antibiotic residues, antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are considered new classes of water contaminants due to their potential adverse effects on aquatic ecosystems and human health. This paper provides comprehensive data on the occurrences of 19 antibiotics, bacteria resistant to 10 antibiotics, and 15 ARGs in raw influent and different treatment stages of conventional activated sludge (CAS) and membrane bioreactor (MBR) systems. Seventeen out of the 19 target antibiotics were detected in raw influent with concentrations of up to ten micrograms per liter. Concentrations of antibiotics measured in the secondary effluent were much lower compared to those in the raw influent. Among the antibiotics, amoxicillin, azithromycin, ciprofloxacin, chloramphenicol, meropenem, minocycline, oxytetracycline, sulfamethazine and vancomycin had highest removal by CAS or MBR systems with median removal efficiency (RE) > 70%, while trimethoprim and lincomycin were recalcitrant in the CAS system with median RE <50%. Similarly, the target ARB and ARGs were omnipresent in the raw influent samples with average concentrations as high as 2.6 × 10⁶ CFU/mL and 2.0 × 10⁷ gene copies/mL, respectively. The concentrations of ARB in secondary effluent of the CAS system declined relative to the raw influent (i.e. lower than raw influent by 2-3 orders of magnitude) and no ARB were detected in the MF permeate of the MBR system. For ARGs, their concentrations in secondary effluent/MF permeate ranged from below method quantification limit (<MQL) to 10⁴ gene copies/mL. It is noteworthy that several ARGs, i.e. bla_KPC, bla_NDM, bla_SHV, ermB, intI1, sul1 and tetO, were still found in the MF permeate of the MBR system at average concentrations up to 10³ copies/mL. In conclusion, MBR outperformed CAS in the elimination of ARB, ARGs and most target antibiotics.

Removal of selected pharmaceuticals and personal care products in reclaimed water during simulated managed aquifer recharge

This study investigated the removal of selected pharmaceuticals and personal care products (PPCPs) in a simulated managed aquifer recharge (MAR) system. The PPCPs included antibiotic, antiepileptic, antihypertensive, anti-inflammatory, and antilipidemic drugs, contrast media, herbicides, and stimulants. We first monitored the occurrence and fate of 22 PPCPs at a water reclamation facility (WRF) in Korea, and found carbamazepine and primidone were not readily removed (below 25% removal in average) by the WRF. This reclaimed water passed through a laboratory-scale soil column set-up at 0.5 m/d over one year, simulating MAR system. Atenolol, propranolol, and trimethoprim exhibited higher removal rates (>80%) than other PPCPs through the simulated MAR, while atrazine, carbamazepine, lincomycin, primidone, and sulfamethazine were not readily removed, exhibiting removal rates below 20%. It can be efficient to monitor and manage these recalcitrant compounds at MAR systems to improve water quality.

Global review and analysis of erythromycin in the environment: Occurrence, bioaccumulation and antibiotic resistance hazards

Environmental observations of antibiotics and other pharmaceuticals have received attention as indicators of an urbanizing global water cycle. When connections between environment and development of antibiotic resistance (ABR) are considered, it is increasingly important to understand the life cycle of antibiotics. Here we examined the global occurrence of erythromycin (ERY) in: 1. wastewater effluent, inland waters, drinking water, groundwater, and estuarine and coastal systems; 2. sewage sludge, biosolids and sediments; and 3. tissues of aquatic organisms. We then performed probabilistic environmental hazard assessments to identify probabilities of exceeding the predicted no-effect concentration (PNEC) of 1.0 μg L^-1 for promoting ABR, based on previous modeling of minimum inhibitory concentrations and minimal selective concentrations of ERY, and measured levels from different geographic regions. Marked differences were observed among geographic regions and matrices. For example, more information was available for water matrices (312 publications) than solids (97 publications). ERY has primarily been studied in Asia, North America and Europe with the majority of studies performed in China, USA, Spain and the United Kingdom. In surface waters 72.4% of the Asian studies have been performed in China, while 85.4% of the observations from North America were from the USA; Spain represented 41.9% of the European surface water studies. Remarkably, results from PEHAs indicated that the likelihood of exceeding the ERY PNEC for ABR in effluents was markedly high in Asia (33.3%) followed by Europe (20%) and North America (17.8%). Unfortunately, ERY occurrence data is comparatively limited in coastal and marine systems across large geographic regions including Southwest Asia, Eastern Europe, Africa, and Central and South America. Future studies are needed to understand risks of ERY and other antibiotics to human health and the environment, particularly in developing regions where waste management systems and treatment infrastructure are being implemented slower than access to and consumption of pharmaceuticals is occurring.

Occurrence and fate of most prescribed antibiotics in different water environments of Tehran, Iran

The presence of most prescribed antibiotic compounds from four therapeutic classes (β-lactam, cephalosporins, macrolides, fluoroquinolones) were studied at two full-scale WWTPs, two rivers, thirteen groundwater resources, and five water treatment plants in Tehran. Analytical methodology was based on high performance liquid chromatography/tandem mass spectrometry after solid-phase extraction. Samples were collected at 33 sample locations on three sampling periods over four months from June to August 2016. None of the target antibiotics were detected in groundwater resources and water treatment plants, while seven out of nine target antibiotics were analyzed in two studied river waters as well as the influent and effluent of wastewater treatment plants at concentrations ranging from <LOQ to 926.32ng/L. Ciprofloxacin predominated in all analyzed influent (552.6-796.2ng/L) and effluent (127-248.7ng/L) samples of WWTP A, whereas cephalosporins including cephalexin (523.3-977.7ng/L) and cefixime (278.65 to 422.1ng/L) were the most abundant detected antibiotics in the influent and effluent of WWTP B. Aqueous phase removal efficiencies were assessed and ranged from 339.83% to 100% for the seven detected antibiotics. "Negative removals" were observed for erythromycin, azithromycin, and cefixime due to the deconjugation of conjugated metabolites via biological transformation in the studied WWTPs. From a statistical point of view, significant differences (p<0.05) were observed in the concentrations of cefixime, cephalexin, azithromycin, and erythromycin in the effluent of both studied WWTPs. Ciprofloxacin and cephalexin were the most abundant detected antibiotics in the two studied river waters. Statistical results revealed that there were significant differences in the concentrations of ciprofloxacin, azithromycin, and erythromycin (p<0.05) in Firozabad ditch (receiving WWTP effluent) and Kan River (non-receiving WWTP effluent) which demonstrated that WWTPs discharges could be an important source of antibiotics being released in water bodies.

Fast trace determination of nine odorant and estrogenic chloro- and bromo-phenolic compounds in real water samples through automated solid-phase extraction coupled with liquid chromatography tandem mass spectrometry

A fast and reliable method was developed for simultaneous trace determination of nine odorous and estrogenic chloro- and bromo-phenolic compounds (CPs and BPs) in water samples using solid-phase extraction (SPE) coupled with liquid chromatography tandem mass spectrometry (LC-MS/MS). For sample preparation, the extraction efficiencies of two widely applied cartridges Oasis HLB and Sep-Pak C18 were compared, and the Oasis HLB cartridge showed much better extraction performance; pH of water sample also plays important role on extraction, and pH = 2-3 was found to be most appropriate. For separation of the target compounds, small addition of ammonium hydroxide can obviously improve the detection sensitivity, and the optimized addition concentration was determined as 0.2%. The developed efficient method was validated and showed excellent linearity (R ² > 0.995), low limit of detection (LOD, 1.9-6.2 ng/L), and good recovery efficiencies of 57-95% in surface and tap water with low relative standard deviation (RSD, 1.3-17.4%). The developed method was finally applied to one tap and one surface water samples and most of these nine targets were detected, but all of them were below their odor thresholds, and their estrogen equivalent (EEQ) were also very low.

Photochemical degradation of the carbapenem antibiotics imipenem and meropenem in aqueous solutions under solar radiation

This paper deals with the photochemical fate of two representative carbapenem antibiotics, namely imipenem and meropenem, in aqueous solutions under solar radiation. The analytical method employed for the determination of the target compounds in various aqueous matrices, such as ultrapure water, municipal wastewater treatment plant effluents, and river water, at environmentally relevant concentrations, was liquid chromatography coupled with hybrid triple quadrupole-linear ion trap-mass spectrometry. The absorption spectra of both compounds were measured in aqueous solutions at pH values from 6 to 8, and both compounds showed a rather strong absorption band centered at about 300 nm, while their molar absorption coefficient was in the order from 9 × 10³-10⁴ L mol^-1 cm^-1. The kinetics of the photochemical degradation of the target compounds was studied in aqueous solutions under natural solar radiation in a solar reactor with compound parabolic collectors. It was found that the photochemical degradation of both compounds at environmentally relevant concentrations follows first order kinetics and the quantum yield was in the order of 10^-3 mol einsten^-1. Several parameters were studied, such as solution pH, the presence of nitrate ions and humic acids, and the effect of water matrix. In all cases, it was found that the presence of various organic and inorganic constituents in the aqueous matrices do not contribute significantly, either positively or negatively, to the photochemical degradation of both compounds under natural solar radiation. In a final set of photolysis experiments, the effect of the level of irradiance was studied under simulated solar radiation and it was found that the quantum yield for the direct photodegradation of both compounds remained practically constant by changing the incident solar irradiance from 28 to 50 W m^-2.

Occurrence and removal of pharmaceuticals, hormones, personal care products, and endocrine disrupters in a full-scale water reclamation plant

This study provided the first comprehensive data on the occurrence and removal of twenty-five target emerging contaminants (ECs) in a full-scale water reclamation plant (WRP) in the Southeast Asian region. Nineteen out of the twenty-five ECs were ubiquitously detected in raw influent samples. Concentrations of the detected ECs in raw influent samples ranged substantially from 44.3 to 124,966ng/L, depending upon the compound and sampling date. The elimination of ECs in full-scale conventional activated sludge (CAS) and membrane bioreactor (MBR) systems at a local WRP was evaluated and compared. Several ECs, such as acetaminophen, atenolol, fenoprofen, indomethacin, ibuprofen, and oxybenzone, exhibited excellent removal efficiencies (>90%) in biological wastewater treatment processes, while some of the investigated compounds (carbamazepine, crotamiton, diclofenac, and iopamidol) appeared to be persistent in the both CAS and MBR systems. Field-based monitoring results showed that MBR outperformed CAS in the elimination of most target ECs. The relationship between molecular characteristics of ECs (i.e. physicochemical properties and structural features) and their removal efficiencies during biological wastewater treatment was also elucidated. Excellent removal efficiencies (>90%) were often noted for ECs with the sole presence of electron donating groups (i.e. phenolic [OH], amine [NH₂], methoxy [OCH₃], phenoxy [OC₆H₅], or alkyl groups). Conversely, ECs with the absence of electron donating groups or the predominance of strong electron withdrawing groups (e.g. halogenated, carbonyl, carboxyl, and sulfonamide) tended to show poor removal efficiencies (<30%) in biological wastewater treatment processes.

Removal of selected PPCPs, EDCs, and antibiotic resistance genes in landfill leachate by a full-scale constructed wetlands system

Landfill leachate could be a significant source of emerging contaminants (ECs) and antibiotic resistance genes (ARGs) into the environment. This study provides the first information on the occurrence of selected ECs and ARGs in raw leachate from 16-year old closed landfill site in Singapore. Among the investigated ECs, acetaminophen (ACT), bisphenol A (BPA), clofibric acid (CA), caffeine (CF), crotamiton (CTMT), diclofenac (DCF), N,N-diethyl-m-toluamide (DEET), gemfibrozil (GFZ), lincomycin (LIN), salicylic acid (SA), and sulfamethazine (SMZ) were the most frequently detected compounds in raw landfill leachate. The concentrations of detected ECs in raw landfill leachate varied significantly, from below quantification limit to 473,977 ng/L, depending on the compound. In this study, Class I integron (intl1) gene and ten ARGs were detected in raw landfill leachate. Sulfonamide resistance (sul1, sul2, and dfrA), aminoglycoside resistance (aac6), tetracycline resistance (tetO), quinolone resistance (qnrA), and intl1 were ubiquitously present in raw landfill leachate. Other resistance genes, such as beta-lactam resistance (blaNMD1, blaKPC, and blaCTX) and macrolide-lincosamide resistance (ermB) were also detected, detection frequency of <50%. The removal of target ECs and ARGs by a full-scale hybrid constructed wetland (CW) was also evaluated. The vast majority of ECs exhibited excellent removal efficiencies (>90%) in the investigated hybrid CW system. This hybrid CW system was also found to be effective in the reduction of several ARGs (intl1, sul1, sul2, and qnrA). Aeration lagoons and reed beds appeared to be the most important treatment units of the hybrid CW for removing the majority of ECs from the leachate.

Biosynthesis of staphylococcal enterotoxin A by genetic engineering technology and determination of staphylococcal enterotoxin A in water by HPLC-ESI-TOF

Staphylococcal enterotoxin A (SEA) was the major virulence factor of Staphylococcus aureus and a biomarker of S. aureus. To establish a fast, low cost, high accuracy, reliable, and simple method for detecting S. aureus, SEA was analyzed by HPLC-ESI-TOF. SEA was not yet commercially available in universal, so SEA was prepared before it was analyzed by HPLC-ESI-TOF. The result showed that high purified SEA was successfully prepared and SEA has normal distribution in mass spectra. A large amount of recombinant SEA (rSEA) was obtained by engineering technology and was purified by Ni affinity chromatography column, and the expression and purity of rSEA and SEA were analyzed by SDS-PAGE. The factors effected on ionization of SEA were studied, and the qualitative analysis of SEA by HPLC-ESI-TOF. The result showed that large amount of SEs expressed within a short time at 28 °C or thereabouts, and there was no impurity bands in electrophorogram after rSEA was purified by Ni affinity chromatography column. In addition, the SEA which had homologous AA sequence with wild SEA was made by rSEA. The retention of SEA in column and ionization of SEA in ESI-TOF were studied for qualitative analysis of S. aureus. The result showed that the content of formic acid in mobile phase was an important factor for ionization of SEs in ESI-TOF. And the result provided theoretical foundation for qualitative detection of S. aureus. [SEs + nH⁺ + mNH₄⁺] ^n+m+ was shown on ESI-TOF spectra when SEA was detected by ESI-TOF in positive ion mode, and the numerical value of n+m was less than or equal to the number of basic amino acids in SEs. This method was applied to determine SEA in water samples preliminarily, and the detection limit of SEA in spiked water sample was 3 mg/kg. The limit of detection of 3 mg/kg was low sensitivity for low molecular weight matters, but it was high sensitivity for SEA which had a high molecular weight of 27 kDa. Of SEA, 3 mg/kg was equivalent to 10^-4 mmol/kg of SEA. This study can provide evidence for establishing method to determine SEA in real samples.

Occurrence and removal of multiple classes of antibiotics and antimicrobial agents in biological wastewater treatment processes

Very little information on the occurrence and fate of multiple classes of antimicrobials in the aquatic environment is reported for the Southeast Asian region. This study provides the first and comprehensive data on the occurrence of ten different classes of antimicrobials in wastewater samples for Singapore. Among the investigated antimicrobials, 19 out of 21 target compounds were detected in 100% of the collected raw influent samples. Concentrations of the detected antimicrobials in raw influent varied from 23.8 to 43,740 ng/L. Removal of antimicrobials by conventional activated sludge (CAS) and membrane bioreactor (MBR) systems at a local wastewater treatment plant was evaluated. MBR exhibited better performance over CAS for most target antimicrobials. Beta-lactam, glycopeptide, and fluoroquinolone classes were largely eliminated by biological wastewater treatment processes, whereas trimethoprim and lincosamides appeared to be persistent. Effects of physicochemical properties and chemical structures of target antimicrobials on their removal efficiencies/mechanisms during wastewater treatment process were also discussed.