Toxicological impacts of antibiotics on aquatic micro-organisms: A mini-review

Climate-Resilient Microbial Biotechnology: A Perspective on Sustainable Agriculture

We designed this review to describe a compilation of studies to enlighten the concepts of plant–microbe interactions, adopted protocols in smart crop farming, and biodiversity to reaffirm sustainable agriculture. The ever-increasing use of agrochemicals to boost crop production has created health hazards to humans and the environment. Microbes can bring up the hidden strength of plants, augmenting disease resistance and yield, hereafter, crops could be grown without chemicals by harnessing microbes that live in/on plants and soil. This review summarizes an understanding of the functions and importance of indigenous microbial communities; host–microbial and microbial–microbial interactions; simplified experimentally controlled synthetic flora used to perform targeted operations; maintaining the molecular mechanisms; and microbial agent application technology. It also analyzes existing problems and forecasts prospects. The real advancement of microbiome engineering requires a large number of cycles to obtain the necessary ecological principles, precise manipulation of the microbiome, and predictable results. To advance this approach, interdisciplinary collaboration in the areas of experimentation, computation, automation, and applications is required. The road to microbiome engineering seems to be long; however, research and biotechnology provide a promising approach for proceeding with microbial engineering and address persistent social and environmental issues.

The panorama of antibiotics and the related antibiotic resistance genes (ARGs) in landfill leachate

Landfill leachate is an important source and sink of antibiotics and antibiotic resistance genes (ARGs), which poses a potential threat to human health and ecological environment. Ten antibiotics and 8 ARGs in leachates collected from Zhejiang Province, China, were systematically investigated. The effects of multiple factors were considered: leachate age, season when the leachate was sampled (dry or rainy), heavy metal concentrations, and leachate quality parameters. Leachate age was crucial to the profile of the detectable antibiotics and ARGs. The total concentration of antibiotics were in the order of macrolides > sulfonamides > tetracyclines and they decreased significantly with leachate age. Similarly, fewer ARGs were harbored in aged leachate; the order of abundance of the ARGs was mexF (11.92 ± 0.22 log₁₀ gene copies/L) > sul2 > Intl1 > sul1 > ermB > mefA > tetM > tetQ (9.57 ± 1.32 log₁₀ gene copies/L). The extreme abundances (i.e., the maxima and minima) of ARGs relating to the same class of antibiotic were always surprisingly similar and appeared in leachate of the same age. Seasonal variation greatly affected the concentrations of antibiotics in the leachate-the concentration difference between the dry and rainy seasons could reach two orders of magnitude. Heavy metal concentrations and leachate quality parameters also had important effects on the distribution of antibiotics and ARGs. Overall, the profile of antibiotics and ARGs in leachates was influenced by numerous factors, and the pollution of antibiotics and ARGs may be reduced and controlled by adjusting the environmental factors.

Sustainable adsorptive removal of antibiotic residues by chitosan composites: An insight into current developments and future recommendations

During COVID-19 crisis, water pollution caused by pharmaceutical residuals have enormously aggravated since millions of patients worldwide are consuming tons of drugs daily. Antibiotics are the preponderance pharmaceutical pollutants in water bodies that surely cause a real threat to human life and ecosystems. The excellent characteristics of chitosan such as nontoxicity, easy functionality, biodegradability, availability in nature and the abundant hydroxyl and amine groups onto its backbone make it a promising adsorbent. Herein, we aimed to provide a comprehensive overview of recent published research papers regarding the removal of antibiotics by chitosan composite-based adsorbents. The structure, ionic form, optimum removal pH and λ_max of the most common antibiotics including Tetracycline, Ciprofloxacin, Amoxicillin, Levofloxacin, Ceftriaxone, Erythromycin, Norfloxacin, Ofloxacin, Doxycycline, Cefotaxime and Sulfamethoxazole were summarized. The development of chitosan composite-based adsorbents in order to enhance their adsorption capacity, reusability and validity were presented. Moreover, the adsorption mechanisms of these antibiotics were explored to provide more information about adsorbate-adsorbent interactions. Besides the dominant factors on the adsorption process including pH, dosage, coexisting ions, etc. were discussed. Moreover, conclusions and future recommendations are provided to inspire for further researches.

High yield M-BTC type MOFs as precursors to prepare N-doped carbon as peroxymonosulfate activator for removing sulfamethazine: The formation mechanism of surface-bound SO4•- on Co-Nx site

M-BTCs (M = Fe, Co and Mn)/melamine were used to prepare N-doped carbon materials, and their performances as activator of peroxymonosulfate (PMS) for sulfamethazine (SMZ) removal were compared. M-BTC type metal-organic frameworks (MOFs) were synthesized under room temperature, with their yield about 7.5 times of ZIF-67 which is the most used MOFs to prepare N-doped carbon materials as the catalyst of persulfate-based advanced oxidation processes. Co-BTC/melamine derived N-doped carbon materials (Co-BTC/5MNC) performed the best, even better than that of ZIF-67 derived N-doped carbon materials. Initial pH (3-9), 0-10 mM inorganic anions (Cl^-, NO₃^-, HCO₃^- and H₂PO₄^2-) and humic acid (5 and 10 mg/L) had no obvious inhibition on SMZ removal with Co-BTC/5MNC as catalyst. The results of both X-ray photoelectron spectroscopy and density functional theory (DFT) calculations indicated that N-coordinated cobalt single atom site (Co-N_x) was the possible active site of Co-BTC/5MNC. Importantly, surface-bound SO₄^•- was identified as the dominant reactive oxygen species for SMZ removal. The SO₄^•- generated through the charge transfer between PMS and catalyst, and was tightly adsorbed on Co-N_x site.

Efficacy of Ciprofloxacin and Amoxicillin Removal and the Effect on the Biochemical Composition of Chlorella vulgaris

Antibiotics are frequently detected in the aquatic environment due to their excessive usage and low-efficiency removal in wastewater treatment plants. This can provide the origin to the development of antibiotic-resistant genes in the microbial community, with considerable ecotoxicity to the environment. Among the antibiotics, the occurrence of ciprofloxacin (CIP) and amoxicillin (AMX) has been detected in various water matrices at different concentrations around the Earth. They are designated as emerging contaminants (ECs). Microalga Chlorella vulgaris (C. vulgaris) has been extensively employed in phycoremediation studies for its acclimatization property, non-target organisms for antibiotics, and the production of value-added bioproducts utilizing the nutrients from the wastewater. In this study, C. vulgaris medium was spiked with 5 mg/L of CIP and AMX, and investigated for its growth-stimulating effects, antibiotic removal capabilities, and its effects on the biochemical composition of algal cells compared to the control medium for 7 days. The results demonstrated that C. vulgaris adapted the antibiotic spiked medium and removed CIP (37 ± 2%) and AMX (25 ± 3%), respectively. The operating mechanisms were bioadsorption, followed by bioaccumulation, and biodegradation, with an increase in cell density up to 46 ± 3% (CIP) and 36 ± 4% (AMX), compared to the control medium. Further investigations revealed that, in the CIP stress-induced algal medium, an increase in major photosynthetic pigment chlorophyll-a (30%) and biochemical composition (lipids (50%), carbohydrates (32%), and proteins (65%)) was observed, respectively, compared to the control medium. In the AMX stress-induced algal medium, increases in chlorophyll-a (22%), lipids (46%), carbohydrates (45%), and proteins (49%) production were observed compared to the control medium. Comparing the two different stress conditions and considering that CIP is more toxic than AMX, this study provided insights on the photosynthetic activity and biochemical composition of C. vulgaris during the stress conditions and the response of algae towards the specific antibiotic stress. The current study confirmed the ability of C. vulgaris to adapt, bioadsorb, bioaccumulate, and biodegrade emerging contaminants. Moreover, the results showed that C. vulgaris is not only able to remove CIP and AMX from the medium but also can increase the production of valuable biomass usable in the production of various bioproducts.

Occurrence of antibiotics in waters, removal by microalgae-based systems, and their toxicological effects: A review

Global antibiotics consumption has been on the rise, leading to increased antibiotics release into the environment, which threatens public health by selecting for antibiotic resistant bacteria and resistance genes, and may endanger the entire ecosystem by impairing primary production. Conventional bacteria-based treatment methods are only moderately effective in antibiotics removal, while abiotic approaches such as advanced oxidation and adsorption are costly and energy/chemical intensive, and may cause secondary pollution. Considered as a promising alternative, microalgae-based technology requires no extra chemical addition, and can realize tremendous CO₂ mitigation accompanying growth related pollutants removal. Previous studies on microalgae-based antibiotics removal, however, focused more on the removal performances than on the removal mechanisms, and few studies have concerned the toxicity of antibiotics to microalgae during the treatment process. Yet understanding the removal mechanisms can be of great help for targeted microalgae-based antibiotics removal performances improvement. Moreover, most of the removal and toxicity studies were carried out using environment-irrelevant high concentrations of antibiotics, leading to reduced guidance for real-world situations. Integrating the two research fields can be helpful for both improving antibiotics removal and avoiding toxicological effects to primary producers by the residual pollutants. This study, therefore, aims to build a link connecting the occurrence of antibiotics in the aquatic environment, the removal of antibiotics by microalgae-based processes, and the toxicity of antibiotics to microalgae. Distribution of various categories of antibiotics in different water environments were summarized, together with the antibiotics removal mechanisms and performances in microalgae-based systems, and the toxicological mechanisms and toxicity of antibiotics to microalgae after either short-term or long-term exposure. Current research gaps and future prospects were also analyzed. The review could provide much valuable information to the related fields, and provoke interesting thoughts on integrating microalgae-based antibiotics removal research and toxicity research on the basis of environmentally relevant concentrations.

Antimicrobial Resistance in Rivers: A Review of the Genes Detected and New Challenges

River ecosystems are very important parts of the water cycle and an excellent habitat, food, and drinking water source for many organisms, including humans. Antibiotics are emerging contaminants which can enter rivers from various sources. Several antibiotics and their related antibiotic resistance genes (ARGs) have been detected in these ecosystems by various research programs and could constitute a substantial problem. The presence of antibiotics and other resistance cofactors can boost the development of ARGs in the chromosomes or mobile genetic elements of natural bacteria in rivers. The ARGs in environmental bacteria can also be transferred to clinically important pathogens. However, antibiotics and their resistance genes are both not currently monitored by national or international authorities responsible for controlling the quality of water bodies. For example, they are not included in the contaminant list in the European Water Framework Directive or in the US list of Water-Quality Benchmarks for Contaminants. Although ARGs are naturally present in the environment, very few studies have focused on non-impacted rivers to assess the background ARG levels in rivers, which could provide some useful indications for future environmental regulation and legislation. The present study reviews the antibiotics and associated ARGs most commonly measured and detected in rivers, including the primary analysis tools used for their assessment. In addition, other factors that could enhance antibiotic resistance, such as the effects of chemical mixtures, the effects of climate change, and the potential effects of the coronavirus disease 2019 pandemic, are discussed. Environ Toxicol Chem 2022;41:687-714. © 2022 SETAC.

Cyclodextrin modified green synthesized graphene oxide@iron nanoparticle composites for enhanced removal of oxytetracycline

The presence of residual antibiotics will lead to potential environmental risks. Here cyclodextrins (CDs) were successfully used to modify graphene-based iron nanoparticles (GO@Fe NPs) to enhance the absorption of oxytetracycline hydrochloride (OTC). The removal of OTC decreased in the order: γCD-GO@Fe NPs > βCD-GO@Fe NPs > αCD-GO@Fe NPs > GO@Fe NPs, with better performance than that of bare GO and Fe NPs. Characterization techniques were applied to better understand how CDs impact the structure of GO@Fe NPs and improve removal performance. Raman and X-ray diffraction analysis showed that GO acted as a carrier to support Fe NPs within the grafted cyclodextrin, where GO also participated in the removal process. Cyclodextrin modified GO@Fe NPs had relatively small particle sizes (15 nm), with a high surface area (61.7 m² · g^-1). X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy suggested that cyclodextrin acted as both a stabilizing and capping agent during green synthesis, which could protect the reactivity of Fe NPs and simultaneously reduce aggregation. A potential synthesis mechanism of cyclodextrins modified composites was also proposed, and subsequent wastewater testing indicated that γCD-GO@Fe NPs had high potential for practical applications.

Acute exposure effects of tetracycline, ampicillin, sulfamethoxazole, and their mixture on nutrient removal and microbial communities in the activated sludge of air-scouring and reciprocation membrane bioreactors

The fate of antibiotics, their effects on non-target species, and the spread of antibiotic resistance in wastewater treatment systems have been of concern in recent years. Despite its importance, the effects of these antibiotics on biological nutrient removal in WWTPs have not been completely elucidated. To evaluate the effects of antimicrobial compounds on nutrient removal performance and microbiome, batch experiments were performed using activated sludge samples taken from two distinct membrane bioreactor systems (reciprocation MBR vs. air-scouring MBR). We exposed the activated sludge to 0 mg/L, 0.1 mg/L, and 1.0 mg/L of tetracycline (TET), ampicillin (AMP), sulfamethoxazole (SUL), and their mixture. The mixture of antibiotics significantly decreased ammonia removal efficiency in the reciprocation MBR (rMBR) and air-scouring MBR (AS MBR) by 5% and 12%, respectively. A significant reduction (p < 0.05) in the amoA-AOB gene was observed in AS MBR, while this gene remained unaffected in the rMBR. Interestingly, the gene abundance of amoA from comammox Nitrospira increased from 2.8 × 10⁸ gene copies per gram sludge (0 mg/L) to 5.0 × 10⁸ gene copies per gram sludge (1.0 mg/L) in the setup with antibiotics in the mixture. Correlation analysis of the relative abundance of prevalent taxa and antibiotic concentrations showed that the microbial communities of the AS MBR were more susceptible to TET and MXD antibiotics than the rMBR microbiome.

Performance and bacterial community of bio-electrochemical system treating simulated domestic wastewater containing low concentration of cephalosporin antibiotics

This study investigated the effects of five cephalosporin antibiotics (ceftazidime, ceftriaxone, cefdinir, cefixime and cefepime) on performance and bacterial community structure in bio-electrochemical systems (BES) and sequencing batch biofilm reactor (SBBR). The results showed that the external electric field had no significant effect on the removal of COD and ammonia nitrogen in water. The removal rates of five antibiotics in BES increased by 28.5%, 20.0%, 9.1%, 21.0%, and 11.5%, respectively. High-through sequencing showed that microbial membrane-growing process increased species diversity, and antibiotics had a significant inhibitory effect on the initial biofilm of the reactor. As time progressed, the inhibitory effect was weakened, and the microorganism were tolerated and re-enriched. The increase in the type and concentration of antibiotics and the applied electric field had a significant effect on the microorganisms in the reactor. The dominant microorganisms for antibiotic removal in the SBBR were Luteococcus, Cloacibacterium, Dysgonomonas, and Ottowia. The dominant bacteria in the BES were Ottowia and Tahibacte. The abundance of these strains increased significantly during antibiotic acclimation. The abundance of Ottowia, Tahibacter, and Nakamurella were significantly higher than SBBR. Thus the BES system had a good antibiotic degradation effect. The BES can effectively treat simulated domestic sewage containing multiple antibiotics, laying a theoretical foundation for the actual wastewater treatment.

Antibiotics in mariculture systems: A review of occurrence, environmental behavior, and ecological effects

Antibiotics are widely applied to prevent and treat diseases occurred in mariculture. The often-open nature of mariculture production systems has led to antibiotic residue accumulation in the culturing and adjacent environments, which can adversely affect aquatic ecosystems, and even human. This review summarizes the occurrence, environmental behavior, and ecological effects of antibiotics in mariculture systems based on peer-reviewed papers. Forty-five different antibiotics (categorized into ten groups) have been detected in mariculture systems around the world, which is far greater than the number officially allowed. Indiscriminate use of antibiotics is relatively high among major producing countries in Asia, which highlights the need for stricter enforcement of regulations and policies and effective antibiotic removal methods. Compared with other environmental systems, some environmental characteristics of mariculture systems, such as high salinity and dissolved organic matter (DOM) content, can affect the migration and transformation processes of antibiotics. Residues of antibiotics favor the proliferation of antibiotic resistance genes (ARGs). Antibiotics and ARGs alter microbial communities and biogeochemical cycles, as well as posing threats to marine organisms and human health. This review may provide a valuable summary of the effects of antibiotics on mariculture systems.

The Biological Effects of Pharmaceuticals in the Marine Environment

Environmental pharmaceuticals represent a threat of emerging concern for marine ecosystems. Widely distributed and bioaccumulated, these contaminants could provoke adverse effects on aquatic organisms through modes of action like those reported for target species. In contrast to pharmacological uses, organisms in field conditions are exposed to complex mixtures of compounds with similar, different, or even opposing therapeutic effects. This review summarizes current knowledge of the main cellular pathways modulated by the most common classes of environmental pharmaceuticals occurring in marine ecosystems and accumulated by nontarget species-including nonsteroidal anti-inflammatory drugs, psychiatric drugs, cardiovascular and lipid regulator agents, steroidal hormones, and antibiotics-and describes an intricate network of possible interactions with both synergistic and antagonistic effects on the same cellular targets and metabolic pathways. This complexity reveals the intrinsic limits of the single-chemical approach to predict the long-term consequences and future impact of pharmaceuticals at organismal, population, and community levels.

Insights into the ecotoxicity of nitrofurazone in marine ecosystems based on body-size spectra of periphytic ciliates

In ecotoxicological studies, some biological responses known as biomarkers can be used as powerful tools to evaluate the ecotoxicity. In this study, we investigated the disparity of responses shown by body-size spectra of periphytic ciliate communities when used as biomarkers to detect the toxicity of the broad-spectrum veternary antibiotic nitrofurazone. Briefly, in chronic exposure experiments ciliate communities were exposed to different concentrations (0, 1, 2, 4 and 8 mg ml^-1) of nitrofurazone. Relative Abundance of ciliates in all body-size categories decreased significantly, whereas their frequency of occurrence and probability densities showed hormetic-like responses in a dose dependent manner. Additionally, body-size distinctness indices were influenced by toxic stress and significantly departed from an expectation at higher nitrofurazone concentrations. Taken together, our results demonstrated that body-size spectra and body-size distinctness offered clear evidence of nitrofurazone toxicity in periphytic ciliates. Body-size spectra can therefore be used as a pivotal biomarker to determine the ecotoxicity of nitrofurazone in aquatic environments.

A Review about Microalgae Wastewater Treatment for Bioremediation and Biomass Production—A New Challenge for Europe

Microalgae have received much attention in the last few years. Their use is being extended to different fields of application and technologies, such as food, animal feed, and production of valuable polymers. Additionally, there is interest in using microalgae for removal of nutrients from wastewater. Wastewater treatment with microalgae allows for a reduction in the main chemicals responsible for eutrophication (nitrogen and phosphate), the reduction of organic substrates (by decreasing parameters such as BOD and COD) and the removal of other substances such as heavy metals and pharmaceuticals. By selecting and reviewing 202 articles published in Scopus between 1992 and 2020, some aspects such as the feasibility of microalgae cultivation on wastewater and potential bioremediation have been investigated and evaluated. In this review, particular emphasis was placed on the different types of wastewaters on which the growth of microalgae is possible, the achievable bioremediation and the factors that make large-scale microalgae treatment feasible. The results indicated that the microalgae are able to grow on wastewater and carry out effective bioremediation. Furthermore, single-step treatment with mixotrophic microalgae could represent a valid alternative to conventional processes. The main bottlenecks are the large-scale feasibility and costs associated with biomass harvesting.

Occurrence and Effects of Antimicrobials Drugs in Aquatic Ecosystems

Currently, thanks to the development of sensitive analytical techniques, the presence of different emerging pollutants in aquatic ecosystems has been evidenced; however, most of them have not been submitted to any regulation so far. Among emerging contaminants, antimicrobials have received particular attention in recent decades, mainly due to the concerning development of antibiotic resistance observed in bacteria, but little is known about the toxicological and ecological impact that antimicrobials can have on aquatic ecosystems. Their high consumption in human and veterinary medicine, food-producing animals and aquaculture, as well as persistence and poor absorption have caused antimicrobials to be discharged into receiving waters, with or without prior treatment, where they have been detected at ng-mg L−1 levels with the potential to cause effects on the various organisms living within aquatic systems. This review presents the current knowledge on the occurrence of antimicrobials in aquatic ecosystems, emphasizing their occurrence in different environmental matrixes and the effects on aquatic organisms (cyanobacteria, microalgae, invertebrates and vertebrates).

Evaluation of growth and biochemical responses of freshwater microalgae Chlorella vulgaris due to exposure and uptake of sulfonamides and copper

Sulfonamides (SAs) and heavy metals are frequently detected together in livestock wastewater. In this study, evaluations regarding their potentially adverse effects on microalgae and according removals were investigated. Results showed that the growth of C. vulgaris was inhibited by SAs and Cu. There was an obvious recovery period in photosynthetic activity (Fv/Fm), indicating that the damage to the photosystem of microalgae was reversible. The co-existence of SAs and Cu significantly affected the biochemical characteristics, including the activities of antioxidant enzyme and the contents of photosynthetic pigments, proteins and polysaccharides. The addition of Cu obviously promoted the removal efficiencies of SMZ, SMX and SMM, which might be ascribed to the bridging effect of Cu in the bioadsorption of SAs. This study is conducive to understand the changes in the biochemical responses of microalgae under the combined impacts of SAs and Cu, and provides a new insight for the simultaneous removals.

Survey on storage, application and incorporation practices for organic fertilizers in Germany

Organic fertilizers from animal production might contain undesirable components, such as veterinary medical product (VMP) residues, that are released into the environment during application. In addition to measures to reduce the use of VMPs through animal health measures, manure management could be an expedient strategy to prevent VMPs from entering the environment. The quantity applied is mainly determined by the nitrogen content. In addition, the depth of incorporation into the soil plays a major role in the environmental risk assessment of VMPs. The new regulations of the German fertilizer ordinance (DüV, 2020), which came into force at the beginning of 2020, as well as the changes that have not yet been fully implemented, will result in adjustments to the storage, application and incorporation practices for organic fertilizer. The aim of this study was to gain more information about the practice of storage, application and incorporation and the challenges for farmers in Germany. An online survey among farmers was conducted to determine the status quo. Almost all of the 125 participants kept livestock, predominantly cattle (68%) and pigs (33%). A third of participants (30%) needed a temporary storage site, for example at neighboring farms. Of the participants, 81% (n = 125) owned cropland and/or grassland. On cropland, manure was mostly incorporated at a depth of 3-15 cm, whereas on grassland, it was mostly applied superficially. On grassland lower-emission application techniques such as slot drill or injector procedures have so far rarely been used. The survey results provided important insights about storage, application and incorporation practices for organic fertilizers in Germany which could be used for the calculation of predicted environmental concentrations (PEC) as part of the environmental risk assessments of veterinary pharmaceuticals.

Specific toxicity of azithromycin to the freshwater microalga Raphidocelis subcapitata

Pharmaceuticals are produced to inflict a specific physiological response in organisms. However, as only partially metabolized after administration, these types of compounds can also originate harmful side effects to non-target organisms. Additionally, there is still a lack of knowledge on the toxicological effects of legacy pharmaceuticals such as the antibiotic azithromycin. This macrolide occurs at high concentrations in the aquatic environment and can constitute a threat to aquatic organisms that are at the basis of the aquatic food chain, namely microalgae. This study established a high-throughput methodology to study the toxicity of azithromycin to the freshwater microalga Raphidocelis subcapitata. Flow cytometry and pulse amplitude modulated (PAM) fluorometry were used as screening tools. General toxicity was shown by effects in growth rate, cell size, cell complexity, cell viability and cell cycle. More specific outcomes were indicated by the analysis of mitochondrial and cytoplasmatic membrane potentials, DNA content, formation of ROS and LPO, natural pigments content and photosystem II performance. The specific mode of action (MoA) of azithromycin to crucial components of microalgae cells was revealed. Azithromycin had a negative impact on the regulation of energy dissipation at the PSII centers, along with an insufficient protection by the regulatory mechanisms leading to photodamage. The blockage of photosynthetic electrons led to ROS formation and consequent oxidative damage, affecting membranes and DNA. Overall, the used methodology exhibited its high potential for detecting the toxic MoA of compounds in microalgae and should be considered for future risk assessment of pharmaceuticals.

Mathematical modeling and numerical simulation of sulfamethoxazole adsorption onto sugarcane bagasse in a fixed-bed column

Having rigorous mathematical models is essential for the design and scaling of adsorption columns. In this study, the dynamic behavior of the sulfamethoxazole adsorption on sugarcane bagasse was studied and compared using analytical models and a theoretical mechanistic model. Initially, fixed-bed column tests were carried out at different flow rates and bed heights. Then, the experimental data were fitted with the most widely used analytical kinetic models, and their fit and fixed-bed parameters were compared with the mechanistic model. Of all analytical models analyzed, the Log-Gompertz model was the one that had the best agreed with experimental data. Although some analytical models fitted the experimental data accurately, their usefulness was questionable. Their parameters did not show a clear relationship with the change in operating conditions, and in certain cases had different behavior from that observed in experimentation. Conversely, the mechanistic model not only predicted the breakthrough curves with great accuracy in the initial and transition stage (R² > 0.92; SSE < 0.06), but it also estimated relevant parameters. Additionally, the effects of the global mass transfer coefficient (K_i) and the axial dispersion coefficient (D_z) on breakthrough curves were studied using the mechanistic model. Increasing K_i increased the slope of the breakthrough curves with a faster adsorption rate. Similarly, high values of D_z produced lower adsorption capacities of the adsorbent; and it was established that the axial dispersion is relevant in SMX adsorption on SB. The theoretical model presented can be used for the design, scaling, and optimization of adsorption columns.

Azithromycin induces dual effects on microalgae: Roles of photosynthetic damage and oxidative stress

Antibiotics are frequently detected in aquatic ecosystems, posing a potential threat to the freshwater environment. However, the response mechanism of freshwater microalgae to antibiotics remains inadequately understood. Here, the impacts of azithromycin (a broadly used antibiotic) on microalgae Chlorella pyrenoidosa were systematically studied. The results revealed that high concentrations (5-100 μg/L) of azithromycin inhibited algal growth, with a 96-h half maximal effective concentration of 41.6 μg/L. Azithromycin could weaken the photosynthetic activities of algae by promoting heat dissipation, inhibiting the absorption and trapping of light energy, impairing the reaction centre, and blocking electron transfer beyond Q_A. The blockage of the electron transport chain in the photosynthetic process further induced the generation of reactive oxygen species (ROS). The increases in the activities of superoxide dismutase, peroxidase and glutathione played important roles in antioxidant systems but were still not enough to scavenge the excessive ROS, thus resulting in the oxidative damage indicated by the elevated malondialdehyde level. Furthermore, azithromycin reduced the energy reserves (protein, carbohydrate and lipid) and impaired the cellular structure. In contrast, a hormesis effect on algal growth was found when exposed to low concentrations (0.5 and 1 μg/L) of azithromycin. Low concentrations of azithromycin could induce the activities of the PSII reaction centre by upregulating the mRNA expression of psbA. Additionally, increased chlorophyll b and carotenoids could improve the absorption of light energy and decrease oxidative damage, which further contributed to the increase in energy reserves (protein, carbohydrate and lipid). The risk quotients of azithromycin calculated in this study were higher than 1, suggesting that azithromycin could pose considerable ecological risks in real environments. The present work confirmed that azithromycin induced dual effects on microalgae, which provided new insight for understanding the ecological risk of antibiotics.

Biodegradation of sulfonamide antibiotics through the heterologous expression of laccases from bacteria and investigation of their potential degradation pathways

In this study, seven laccase genes from different bacteria were linked with the signal peptides PelB, Lpp or Ompa for heterologous expression in E. coli. The recombinant strains were applied for the removal of sulfadiazine (SDZ), sulfamethazine (SMZ), and sulfamethoxazole (SMX). The results obtained for different signal peptides did not provide insights into the removal mechanism. The removal ratios of SDZ, SMZ, and SMX obtained with the recombinant strain 6#P at 60 h were around 92.0%, 89.0%, and 88.0%, respectively. The degradation pathways of sulfonamides have been proposed, including SO₂ elimination, hydroxylation, oxidation, pyrimidine ring cleavage, and N-S bond cleavage. Different mediators participate in the degradation of antibiotics through different mechanisms, and different antibiotics have different responses to the same mediator. The addition of 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) slightly promoted the removal of sulfonamides by most recombinant strains with different signal peptides, especially for the recombinant strain 2#O. The removal of sulfonamides by 1-hydroxybenzotriazole (HBT) varied with the recombinant strains. Syringaldehyde (SA) had a slight inhibitory effect on the removal of sulfonamides, with the most significant effect on strains 7#L and 7#O.

Oxidation of antibiotics by ferrate(VI) in water: Evaluation of their removal efficiency and toxicity changes

Antibiotics in water and wastewater have been determined extensively. The treatment of antibiotics in water needs evaluation of possible harmful effects on aquatic ecosystems and human health. This paper presents the toxicity evaluation of antibiotics after their treatment with ferrate (VI) (Fe^VIO₄^2-, Fe(VI)) in water. The antibiotics (sulfamethoxazole (SMX), erythromycin (ERY), ofloxacin (OFL), ciprofloxacin (CIP), tetracycline (TET), oxytetracycline (OXY), and trimethoprim (TMP)) were treated at pH 8.0 by applying two concentrations of Fe(VI) to have molar ratios of 5:1 and 10:1 ([Fe(VI)]:[antibiotic]). Under the studied conditions, incomplete removal of antibiotics was observed, suggesting that the treated solutions contained parent antibiotics and their transformation products. The toxicity of antibiotics without Fe(VI) treatment was tested against freshwater green alga Raphidocelis subcapitata and cyanobacterium Synechococcus elongatus, which were determined to be generally sensitive to antibiotics, with EC₅₀ < 1.0 mg/L. The toxicity of Fe(VI) treated solution was tested against R. subcapitata. Results found no toxicity for the treated solutions of OFL, CIP, and OXY. However, SMX, ERY, and TET remained toxic after Fe(VI) treatment (i.e., more than 75% growth inhibition of R. subcapitata). Results demonstrated that R. subcapitata may be applied to test the toxicity of antibiotics after oxidative treatments.

The link between pharmaceuticals and cyanobacteria: a review regarding ecotoxicological, ecological, and sanitary aspects

Cyanobacteria are important for ecosystem functioning, but eutrophication may affect the surrounding biome by losing ecosystem services and/or through affecting the cyanotoxins production that threatens ecological and human health. Pollution is an environmental issue that affects aquatic ecosystems worldwide, and the knowledge of the role of synthetic chemicals such as pharmaceuticals is still scarce. Therefore, studies coupling these two relevant issues are essential to better understand the ecological risks and the potential threats to public health. Thus, an overview of ecotoxicological tests performed in the literature exposing cyanobacteria to pharmaceuticals and the possible consequences regarding ecological and sanitary aspects was conducted. Moreover, a risk assessment was performed to enable a better understanding of pharmaceuticals affecting cyanobacteria ecology. Most of the studies found in the literature tested isolated pharmaceuticals in laboratory conditions, while others assessed mixture effects on in situ conditions. The endpoints most assessed were growth, photosynthesis, and antioxidant enzyme activity. The studies also point out that cyanobacteria may present resistance or sensitivity depending on the concentrations and the therapeutic class, which may cause a change in the ecosystem dynamics and/or sanitary implications due to cyanotoxin production. The risk assessment highlighted that antibiotics are among the most relevant substances due to the chemical diversity and higher levels found in the environment than other therapeutic classes. This review highlighted gaps regarding cyanotoxin release into aquatic environments due to the occurrence of pharmaceuticals and the need for more realistic experiments to better understand the potential consequences for human and environmental health.

ZnCDs/ZnO@ZIF-8 Zeolite Composites for the Photocatalytic Degradation of Tetracycline

Considering the photocatalytic performance of CDs, ZnO, and the unique porous nanostructure and stability of ZIF-8, we prepared ZnCDs/ZnO@ZIF-8 zeolite composites. The resultant material represented an enhanced ability for the photodegradation of TC compared with that of ZnCDs and ZnO. The photocatalytic degradation efficiency reached over 85%. The catalytic activity of the composites was maintained after four cycles. The experimental result indicated that ⋅O2 radical was the active species in the reaction.

Record of trace organic contaminants in a river sediment core: From historical wastewater management to historical use

Some trace organic contaminants (TrOCs) can be considered as ubiquitous contaminants since the 1950s, and the study of their historical distribution within river sediments allows us to better understand the temporal variation of the chemical quality of sediments, and make assumptions about the most insightful forcings impacting these distributions. In this study, the occurrence of 41 TrOCs of various classes (i.e. pharmaceutical products and pesticides) was studied in a sedimentary core sampled in a disused dock along the Seine River, France. This core covers a 60 year-long period between 1944 and 2003, and 23 TrOCs were detected at least once. Their concentrations mainly ranged between 1 and 10 ng g^-1 within the core, except for tetracycline that exhibited higher concentrations (~hundreds of ng·g^-1). The dating of the core, based on previous studies, enabled the characterization of the changes since 1945, potentially impacted by (i) the sewer connectivity, (ii) the upgrading of wastewater treatment technologies, (iii) historical modifications in the use of each TrOC, and (iv) the sedimentary composition. In every case the deepest occurrence of each TrOC in the core matched its market authorization date, indicating the potential of TrOC to be used as chronomarkers. This study also reveals that the recent upgrading of wastewater treatment technologies within the watershed decreased the concentrations of each TrOC, despite an increase in TrOC diversity in the most recent years.

Light modulates the effect of antibiotic norfloxacin on photosynthetic processes of Microcystis aeruginosa

Norfloxacin is one of the widely used antibiotics, often detected in aquatic ecosystems, and difficultly degraded in the environment. However, how norfloxacin affects the photosynthetic process of freshwater phytoplankton is still largely unknown, especially under varied light conditions. In this study, we investigated photosynthetic mechanisms of Microcystis aeruginosa in responses to antibiotic norfloxacin (0-50 μg/L) for 72 h under low (LL; 50 μmol photons m^-2 s^-1) and high (HL; 250 μmol photons m^-2 s^-1) growth light regimes. We found that environmentally related concentrations of norfloxacin inhibited the growth rate and operational quantum yield of photosynthesis system II (PSII) of M. aeruginosa more under HL than under LL, suggesting HL increased the toxicity of norfloxacin to M. aeruginosa. Further analyses showed that norfloxacin deactivated PSII reaction centers under both growth light regimes with increased minimal fluorescence yields only under HL, suggesting that norfloxacin not only damaged reaction centers of PSII, but also inhibited energy transfer among phycobilisomes in M. aeruginosa under HL. However, non-photosynthetic quenching decreased in the studied species by norfloxacin exposure under both growth light regimes, suggesting that excess energy might not be efficiently dissipated as heat. Also, we found that reactive oxygen species (ROS) content increased under norfloxacin treatments with a higher ROS content under HL compared to LL. In addition, HL increased the absorption of norfloxacin by M. aeruginosa, which could partly explain the high sensitivity to norfloxacin of M. aeruginosa under HL. This study firstly reports that light can strongly affect the toxicity of norfloxacin to M. aeruginosa, and has vitally important implications for assessing the toxicity of norfloxacin to aquatic microorganisms.

Degradation of benzimidazoles by photoperoxidation: metabolites detection and ecotoxicity assessment using Raphidocelis subcapitata microalgae and Vibrio fischeri

Benzimidazoles (BZ) are among the most used drugs to treat parasitic diseases in both human and veterinary medicine. In this study, solutions fortified with albendazole (ABZ), fenbendazole (FBZ), and thiabendazole (TBZ) were subjected to photoperoxidation (UV/H₂O₂). The hydroxyl radicals generated by the process removed up to 99% of ABZ, and FBZ, in the highest dosage of H₂O₂ (i.e., 1.125 mmol L^-1; 4.8 kJ L^-1). In contrast, 20% of initial TBZ concentration remained in the residual solution. In the first 5 min of reaction (i.e., up to 0.750 mmol L^-1 of H₂O₂), formation of the primary metabolites of ABZ-ricobendazole (RBZ), albendazole sulfone (ABZ-SO₂), and oxfendazole (OFZ)-was observed. However, these reaction products were converted after the reaction time was doubled. The residual ecotoxicity was investigated using the Raphidocelis subcapitata microalgae and the marine bacteria Vibrio fischeri. The results for both microorganisms evidence that the residual solutions are less harmful to these microorganisms. However, after 30 min of reaction, the treated solution still presents a toxic effect for V. fischeri, meaning that longer reaction times are required to achieve an innocuous effluent.

Antibiotic resistance in the environment: a critical insight on its occurrence, fate, and eco-toxicity

The overuse, misuse, and underuse of antibiotics tend to increase the antibiotic burden in the environment resulting into the evolution in microbial community to possess resistance that renders antibiotics ineffective against them. The current review recapitulates the present state of knowledge about the occurrence and fate of antibiotics in various environmental matrices. Also, the prevalence of antibiotic-resistant bacteria/antibiotic-resistant genes (ARB/ARGs) in various biological and non-biological systems, eco-toxicity of antibiotics on non-target organisms, and remediation methods for antibiotics and ARB/ARGs removal were critically reviewed. Furthermore, a comparison of various technologies for their efficiency to eliminate antibiotic residues and ARB/ARGs is made. The study identified gaps in the investigation of toxic effects of low concentration of antibiotics and the mixture of multiple antibiotics on non-target organisms. The study of antibiotics' phytotoxicity and toxicity towards sediment and soil-dwelling organisms are also recognized as a knowledge gap. The review also details policies implemented across the globe to fight against antibiotic resistance, and the scarcity of data on lab to land transferred remediation technology was identified. The present study entails a critical review of literature providing guidelines for the articulation of policies for prudent use of antibiotics, limits on the amount of antibiotics in pharmaceutical formulations, and regular surveillance in the Indian context.

Degradation of antidepressant pharmaceuticals by photoperoxidation in diverse water matrices: a highlight in the evaluation of acute and chronic toxicity

Photoperoxidation (UV/H₂O₂) was used to degrade three of the worldwide most consumed antidepressant pharmaceuticals-bupropion, escitalopram, and fluoxetine-in ultrapure water, drinking tap water, surface water, and reclaimed water. The study was performed with antidepressants in concentration levels in which these compounds usually occur in the water matrices. Online solid-phase extraction coupled to UHPLC-MS/MS was used to quantify the analytes during degradation studies. The UV/H₂O₂ process was able to degrade bupropion and fluoxetine in ultrapure water, using 0.042 mmol L^-1 of H₂O₂ and 1.9 kJ of UV-C irradiation. Nevertheless, escitalopram, which had the most recalcitrant character among the studied antidepressants, needed a tenfold more oxidant and UV-C irradiation. The primary metabolites of the antidepressants were identified as the major by-products generated by the UV/H₂O₂ process, and they persisted in the solution even when the parent compound was degraded. The residual toxicity of the solution was evaluated for two different trophic levels. The UV/H₂O₂ process reduced the toxicity of the solution to Raphidocelis. subcapitata microalgae after 30 min of reaction. On the other hand, the toxicity of the residual solution increased over the reaction time to the marine bacteria Vibrio fischeri (reaching up to 48.3% of bioluminescence inhibition after 60 min of reaction). Thus, our results evidenced that the toxicity against different trophic levels and the monitoring of the by-products formed are important aspects to be considered regarding the safety of the treated solution and the optimization of the treatment process.

Qualitative and Quantitative Analysis of Certain Aspects of the Cytotoxic and Genotoxic Hazard of Hospital Wastewaters by Using a Range of In Vitro Assays

Health care facilities and hospitals generate significant amounts of wastewater which are released into the sewage system, either after a preliminary treatment or without any further treatment. Hospital wastewater may contain large amounts of hazardous chemicals and pharmaceuticals, some of which cannot be eliminated entirely by wastewater treatment plants. Moreover, hospital effluents may be loaded with a plethora of pathogenic microorganisms or other microbiota and microbiome residues. The need to monitor hospital effluents for their genotoxic hazard is of high importance, as detailed information is scarce. DNA-based information can be acquired directly from samples through the application of various molecular methods, while cell-based biomonitoring assays can provide important information about impaired cellular pathways or mechanisms of toxicity without prior knowledge of the identity of each toxicant. In our study, we evaluated samples of chlorinated hospital wastewater discharged into the sewage system after this disinfection process. The assessment of cytotoxicity, genotoxicity and mutagenicity of the hospital effluents was performed in vitro by using a broad battery of biomonitoring assays that are relevant for human health effects. All the tested hospital wastewater samples could be classified as potentially genotoxic, and it is concluded that the microbiota present in hospital wastewater might contribute to this genotoxic potential.

Effects of three antibiotics on growth and antioxidant response of Chlorella pyrenoidosa and Anabaena cylindrica

Antibiotics are essential for treatments of bacterial infection and play important roles in the fields of aquaculture and animal husbandry. Antibiotics are accumulated in water and soil due to the excessive consumption and incomplete treatment of antibiotic wastewater. The accumulation of antibiotics in ecological systems leads to global environmental risks. The toxic effects of spiramycin (SPI), tigecycline (TGC), and amoxicillin (AMX) on Chlorella pyrenoidesa and Anabaena cylindrica were evaluated based on growth inhibition experiments, and determinations of ROS production and antioxidant enzyme activities (catalase, superoxide dismutase, and malondialdehyde). Half maximal effective concentrations (EC50) of TGC, SPI, and AMX for A. cylindrica were 62.52 μg/L, 38.40 μg/L, and 7.66 mg/L, respectively. Those were 6.20 mg/L, 4.58 mg/L, and > 2 g/L for C. pyrenoidesa, respectively. It was shown that A. cylindrica was much more sensitive to these antibiotics than C. pyrenoidesa. In addition, EC50 values of SPI and TGC were lower than that of AMX. It was indicated that SPI and TGC had higher toxic than AMX to C. pyrenoidesa and A. cylindrica. The current study is helpful to evaluating possible ecological risks of TGC, SPI, and AMX by green microalgae and cyanobacteria.

Farmer perceptions of dairy farm antibiotic use and transport pathways as determinants of contaminant loads to the environment

Agricultural antibiotic contamination into milk and beef products has been considered extensively, but antibiotic transport into soil and water environments is less regulated and studied. Farmer perceptions of these transport processes are critical to understanding how antibiotics reach soils and surface waters and what management strategies can be implemented to reduce environmental antibiotic loads. We have conducted semi-structured interviews with twenty-seven dairy farmers in central New York to understand farmer perceptions of environmental transport of antibiotics and decisions that reduce environmental antibiotic loads. Interviews were qualitatively analyzed and coded using thematic analysis. We found that farmers extensively considered transport of antibiotics into milk and beef, while consideration of antibiotic transport into manure was less common, and no farmers discussed antibiotic transport from carcasses into soil from on-farm animal mortality. Farmers highlighted decisions that reduce antibiotic environmental loads through disease prevention actions, usage of non-antibiotic treatments, and culturing bacterial samples before antibiotic treatment. Farmers did not cite reduction of environmental antibiotic loads as a driver of their waste management decisions. Farmers perceived antibiotic usage was already minimized on farms in the region, suggesting future environmental antibiotic contamination mitigation strategies should focus on waste management pathways.

Copper carboxymethyl cellulose nanoparticles for efficient removal of tetracycline antibiotics in water

Copper carboxymethyl cellulose nanoparticles were prepared and characterized by FT-IR, XRD, SEM, TEM, and EDX techniques. Removal of tetracycline was obtained at 90% with optimized parameters of 500 μg/L concentration, 40 min contact time, 7.5 pH, 1.5 g/L dose, and 298 K temp. The adsorption followed Freundlich model very well in comparison to Langmuir. Tempkin model described good interactions between tetracycline and nanoparticles. Dubinin-Radushkevich isotherm confirmed the chemical nature of adsorption. The adsorption was pseudo-second order with a liquid film diffusion kinetics mechanism. The adsorption was endothermic and spontaneous as suggested by thermodynamics results. The supramolecular mechanism was developed for the process. Interestingly, the process was suitable at 7.5 pH with low contact time. These features of the adsorption made this process applicable at natural water conditions, making the process eco-friendly and feasible. Therefore, it may be an excellent method for the removal of tetracycline in any water system.

In situ construction bismuth oxycarbonate/bismuth oxybromide Z-scheme heterojunction for efficient photocatalytic removal of tetracycline and ciprofloxacin

Finely engineering the morphology and regulating the hybrid interface of each component in a heterojunction are important for facilitating charge carrier separation. In this study, a flower-like bismuth oxycarbonate/bismuth oxybromide (Bi₂O₂CO₃/BiOBr, BOC/BiOBr) Z-scheme heterojunction was prepared via generation of BOC followed by in situ self-growth of BiOBr on just generated BOC. The obtained photocatalyst has an interlaced nanosheet structure with oxygen vacancies, which enhances light adsorption and facilitates the migration and separation of charge carriers. The highest apparent rate constants (k) in the degradation of tetracycline and ciprofloxacin using the BOC/BiOBr-2 photocatalyst under visible-light irradiation were 0.0282 and 0.0220 min^-1, respectively; these values were 6.1 and 6.2 times, respectively higher than that achieved using BOC as a photocatalyst. The hybrid mode of BOC and BiOBr, and the Z-scheme electron transfer path and oxygen vacancies present in BOC/BiOBr are the factors responsible for its high photocatalytic activity.

Critical roles of cyanobacteria as reservoir and source for antibiotic resistance genes

The widespread occurrence of antibiotic resistance genes (ARGs) throughout aquatic environments has raised global concerns for public health, but understanding of the emergence and propagation of ARGs in diverse environmental media remains limited. This study investigated the occurrence and spatio-temporal patterns of six classes of ARGs in cyanobacteria isolated from Taihu Lake. Tetracycline and sulfonamide resistance genes were identified as dominant ARGs. The abundance of ARGs in cyanobacteria was significantly higher in the bloom period than in the non-bloom period. The contribution and persistence of ARGs were higher in extracellular DNA (eDNA) than in intracellular DNA (iDNA) from cyanobacteria. Cyanobacteria-associated eDNA carrying ARGs was more stable at lower temperature. The relative abundances of ARGs in Microcystis and Synechococcus, the dominant genera of cyanobacterial blooms in Taihu Lake, were significantly higher than those in other cyanobacterial strains. The conjugative transfer efficiency for bacterial assimilation of ARGs in cyanobacteria was facilitated by increasing temperature and cyanobacterial cell concentration. Our results demonstrated that cyanobacteria could act as a significant reservoir and source for the acquisition and dissemination of ARGs in aquatic environments, hence the definition of negative ecological effects of cyanobacterial blooms was expanded.

Individual and combined effects of amoxicillin, enrofloxacin, and oxytetracycline on Lemna minor physiology

We investigated individual and combined effects of environmentally representative concentrations of amoxicillin (AMX; 2 μg l^-1), enrofloxacin (ENR; 2 μg l^-1), and oxytetracycline (OXY; 1 μg l^-1) on the aquatic macrophyte Lemna minor. While the concentrations of AMX and ENR tested were not toxic, OXY decreased plant growth and cell division. OXY induced hydrogen peroxide (H₂O₂) accumulation and related oxidative stress through its interference with the activities of mitochondria electron transport chain enzymes, although those deleterious effects could be ameliorated by the presence of AMX and/or ENR, which prevented the overaccumulation of ROS by increasing catalase enzyme activity. L. minor plants accumulated significant quantities of AMX, ENR and OXY from the media, although competitive uptakes were observed when plants were submitted to binary or tertiary mixtures of those antibiotics. Our results therefore indicate L. minor as a candidate for phytoremediation of service waters contaminated by AMX, ENR, and/or OXY.

Responses of Hydrocharis dubia (Bl.) Backer and Trapa bispinosa roxb. to tetracycline exposure

The presence of tetracycline is ubiquitous and has adverse effects on aquatic systems. A hydroponic experiment was conducted to investigate the ecological sensitivity of Hydrocharis dubia (Bl.) Backer and Trapa bispinosa Roxb. Exposed to different concentrations of tetracycline (0, 0.1, 1, 10, 30 and 50 mg/L) for one day (1D) and 14 days (14D). The results showed that after 1D of tetracycline exposure, the physiological indices of H. dubia had no remarkable change except for proline which was significantly stimulated under 0.1 mg/L tetracycline. For T. bispinosa, guaiacol peroxidase (POD), polyphenol oxidase (PPO) and ascorbate peroxidase (APX) activity and protein and proline content were notably promoted under different concentrations of tetracycline, but PPO activity was significantly decreased in 50 mg/L. After 14D, tetracycline caused no harm to the growth and protein content of H. dubia, but negatively influenced lipid peroxidation product and chlorophyll content in H. dubia under high tetracycline concentrations. Superoxide dismutase (SOD) and POD activity of H. dubia significantly increased at high tetracycline concentrations, while catalase (CAT) and PPO activity significantly decreased. APX activity in H. dubia increased with tetracycline concentrations at low tetracycline concentrations. For T. bispinosa, high concentrations of tetracycline application significantly inhibited its growth and the content of protein and chlorophyll. SOD, POD, CAT, and PPO activity of T. bispinosa were induced under different concentrations of tetracycline and no lipid peroxidation was observed. APX activity in T. bispinosa was significantly inhibited at high tetracycline concentrations. The results suggest that tetracycline can cause oxidative damage in H. dubia but harm the metabolism process of T. bispinosa without inducing oxidative damage. Overall, the sensitivity of T. bispinosa exposed to tetracycline exposure is higher than that of H. dubia.

Removal of antibiotic from the water environment by the adsorption technologies: a review

Antibiotics are known as emergent pollutants because of their toxicological properties. Due to continuous discharge and persistence in the aquatic environment, antibiotics are detected almost in every environmental matrix. Therefore antibiotics that are polluting the aquatic environment have gained significant research interest for their removal. Several techniques have been used to remove pollutants, but appropriate technology is still to be found. This review addresses the use of modified and cheap materials for antibiotic removal from the environment.

Occurrence and toxicity of antibiotics in the aquatic environment: A review

In recent years, antibiotics have been used for human and animal disease treatment, growth promotion, and prophylaxis, and their consumption is rising worldwide. Antibiotics are often not fully metabolized by the body and are released into the aquatic environment, where they may have negative effects on the non-target species. This review examines the recent researches on eight representative antibiotics (erythromycin, trimethoprim, sulfamethoxazole, tetracycline, oxytetracycline, ofloxacin, ciprofloxacin, and amoxicillin). A detailed overview of their concentrations in surface waters, groundwater, and effluents is provided, supported by recent global human consumption and veterinary use data. Furthermore, we review the ecotoxicity of these antibiotics towards different groups of organisms, and assessment of the environmental risks to aquatic organisms. This review discusses and compares the suitability of currently used ecotoxicological bioassays, and identifies the knowledge gaps and future challenges. The risk data indicate that selected antibiotics may pose a threat to aquatic environments. Cyanobacteria were the most sensitive organisms when using standard ecotoxicological bioassays. Further studies on their chronic effects to aquatic organisms and the toxicity of antibiotic mixtures are necessary to fully understand the hazards these antibiotics present.

Effects of azithromycin on feeding behavior and nutrition accumulation of Daphnia magna under the different exposure pathways

Antibiotics had been paid more and more attention to their toxicity to non-target aquatic organisms in the aquatic environment. As azithromycin (AZI) was an important antibiotic pollutant in water, its toxicity to aquatic organisms had been investigated. In this study, the potential aquatic ecological risk of AZI was identified by assessing the toxicity on the feeding behavior and physiological function of Daphnia magna (D. magna) under the different exposure pathways (aqueous phase exposure vs. food phase exposure). For the food Chlorella pyrenoidosa (C. pyrenoidosa), AZI could inhibit the growth and nutrition accumulation with concentration- and time-response relationship. For D. magna, the feeding behavior was inhibited by AZI under the aqueous phase exposure pathway. However, the feeding behavior was inhibited firstly and then reversed into promotion in the low and medium concentration groups and was continually promoted in the high concentration group under the food phase exposure pathway. The accumulation of polysaccharides and total protein were decreased in D. magna n the high concentration group under the aqueous phase exposure pathway, while the accumulation of polysaccharides and crude fat were decreased in the high concentration group under the food phase exposure pathway. The activity of amylase (AMS) and trypsin in D. magna were decreased after exposure to AZI under the aqueous phase exposure pathway. On the other hand, the activity of AMS in the medium and high concentration groups was decreased under the food phase exposure pathway, but the activity of trypsin was decreased in the medium concentration group and increased in the high concentration group. The levels of ROS in D. magna were also measured and increased in both exposure pathways except in the low concentration group under the food phase exposure pathway, indicating the oxidative stress injury of D. magna. Our results showed that AZI could affect the digestive enzyme activities and oxidative stress-antioxidative system, ultimately leading to the change of D. magna's feeding behavior and nutrition accumulation. These results also provided a comprehensive perspective to evaluate the toxic effects of non-lethal dose antibiotics to non-target aquatic organisms via different exposure pathways.

Distribution and potential risk assessment of antibiotic pollution in the main drinking water sources of Nanjing, China

The distribution character of 41 antibiotics belonging to 6 groups, sulfonamides (SAs), quinolones (QUs), tetracyclines (TCs), macrolides (MLs), penicillins (PLs), and chloramphenicol (CHL), was investigated in drinking water sources of Nanjing during 2017-2019. MLs (42.98%) were the most abundant category, followed by SAs (25.94%) and QUs (22.52%). The dominant antibiotic was ofloxacin (OFX) in Dec. 2017 (average concentration, 3.14 ng/L; range, ND-35.20 ng/L) and Nov. 2018 (2.16 ng/L, ND-12.26 ng/L), and sulfadiazine (SDZ) in Mar. 2019 (16.37 ng/L, ND-25.90 ng/L). For Dec. 2017, the total concentrations in Zhongshan Waterworks (S15) and Jinniushan Reservoir (S16) were significantly higher than the other sampling sites, which may be attributed to point source pollution. The ecological and human risk of the main antibiotics was assessed by risk quotients (RQs) and target hazard quotient (THQ), respectively. Most of the RQ values were below 0.1, except enrofloxacin (ERX, 0.11) and enoxacin (ENX, 0.62) in Dec. 2017, lomefloxacin (LOM, 0.14) in Nov. 2018, and LOM (0.28) and ERX (0.10) in Mar. 2019. This indicated that the risk of the target antibiotics to aquatic organisms in the 3 years was moderate or low level. Meanwhile, results of the THQ values showed that antibiotic exposure caused no risk to human health. This research provides scientific information for antibiotic pollution control and enriches environmental monitoring data in the drinking water sources.

Resistance of cyanobacteria Microcystis aeruginosa to erythromycin with multiple exposure

Here we report a set of experiments in which water blooming cyanobacteria Microcystis aeruginosa was repeatedly exposed to erythromycin. Growth inhibition increased with increasing erythromycin concentration (1-150 μg/L) upon first exposure. Maximum inhibition rate (76.06%), occurred under 150 μg/L erythromycin. Moreover, 96-h 50% effective concentration (EC₅₀) was 22.97 μg/L, indicating that the growth of M. aeruginosa was affected by erythromycin under common environmental concentrations. Photosynthesis was hindered by chlorophyll and photosystem II limitations. Malondialdehyde, reactive oxygen species, and superoxide dismutase contents increased significantly under certain concentrations of erythromycin, but superoxide dismutase was suppressed by 150 μg/L erythromycin. Synthesis of intracellular and extracellular microcystins was promoted by 10-60 and by 20-60 μg/L erythromycin, respectively, but both were inhibited by 100-150 μg/L. Principal component analysis and Pearson's correlation revealed the accumulation of reactive oxygen species as the dominant mechanism of erythromycin toxicity to cells. M. aeruginosa repeatedly subjected to erythromycin exposure showed obvious resistance against the antibiotic, especially when treated twice with 60 μg/L erythromycin. The 96-h EC₅₀ was 81.29 μg/L. As compared to the first exposure to erythromycin, photosynthetic and antioxidant activities increased, while growth inhibition and oxidation stress decreased upon multiple exposures. Production and release of microcystins were enhanced by repeated exposure to the antibiotic. Thus, erythromycin persistence in water should be examined, as repeated exposure may lead to serious environmental and human health hazards.

Occurrence, distribution, and ecological risk of pharmaceuticals in a seasonally ice-sealed river: From ice formation to melting

Occurrence, distribution, and ecological risk of 21 pharmaceuticals in the Jilin Songhua River were investigated during its freeze-thaw periods, including ice formation, sealed, and breakup. Florfenicol was the most abundant pharmaceutical, with mean concentrations of 123.4 ± 61.1 ng L^-1 in water and 73.8 ± 66.3 ng kg^-1 in ice. Sulfadiazine occurred at a higher mean concentration in downstream areas (45.6 ± 7.4 ng L^-1) than in upstream areas (0.7 ± 0.7 ng L^-1). Most pharmaceuticals appeared in relatively high concentrations in water during the ice-breakup period. Complex factors including pharmaceutical usage patterns, ice-regulated photodegradation, biodegradation, water flow, and freeze-concentration effects, as well as the release of pharmaceuticals from ice, were responsible for the temporal variation of pharmaceuticals. Pseudo-ice/water distribution coefficients showed the distribution of pharmaceuticals in ice and demonstrated the effects of their release from the ice on their temporal variations. Most pharmaceuticals posed a risk to algae; of these, amoxicillin exhibited the highest risk. In addition, thawing increased the concentration of thiamphenicol in water, which elevated its ecological risk level. The findings suggest that the pharmaceuticals retained in ice should be considered with regard to regulating pharmaceuticals' temporal variations in seasonal ice-covered rivers during the freeze-thaw process.

Occurrence and distribution of priority pharmaceuticals in the Yellow River and the Huai River in Henan, China

The occurrence and spatial distribution of priority pharmaceuticals (PPs) in water samples from the Yellow River and the Huai River in the Henan region of China were investigated in this study. The concentration of the total PPs (ΣPPs; sum of the 10 observed PPs) ranged from not detected to 3474 ng L^-1 in samples from the Yellow River and from 4.35 to 146 ng L^-1 in samples from the Huai River. The level of the ΣPPs in the Huai River was much lower than that found in the Yellow River. The composition of the PPs differed between the two rivers. Norfloxacin, carbamazepine, and 5,5-diphenylhydantoin were detected at high concentrations in the Yellow River, whereas sulfamethazine, ampicillin trihydrate, carbamazepine, and 5,5-diphenylhydantoin were the dominant species in the Huai River, suggesting there were different pollution sources. In comparison to other studies around China, most of the PPs in water samples from the Yellow River and the Huai River were at low concentrations, except for norfloxacin and ofloxacin. There were significant seasonal variations among the PPs in water samples from the Huai River, whereas spatial distinctions were recorded among the PPs in the Yellow River. Dissolved organic carbon content did not correlate with the PPs in the studied area.

Characteristics of toxin production and release in Microcystis aeruginosa exposed to three tetracycline antibiotics

The application of antibiotics is remarkable globally. However, antibiotic residues in aquatic ecosystems can pose adverse effects on nontarget plants and animals. In the present study, the cell growth properties and the production and release of microcystin-LR and microcystin-RR in cyanobacterium Microcystis aeruginosa after exposure to three typical antibiotics were investigated. Results showed that the order of the degree of chronic toxicities of the three chemicals was oxytetracycline hydrochloride (OTC) > tetracycline hydrochloride (TC) > chlortetracycline hydrochloride (CTC). The target antibiotics interfered with the production and release of the toxins microcystin-LR and microcystin-RR to varying degrees. TC simultaneously increased MC-LR intracellular and extracellular concentrations and interfered with MC-RR intracellular and extracellular concentrations to varying degrees. CTC reduced MC-LR intracellular concentrations and simultaneously reduced the MC-RR intracellular and extracellular concentrations. OTC increased the MC-LR intracellular and extracellular concentrations but did not have an effect on MC-RR concentrations. The extracellular MC-LR concentrations increased dramatically from day 24 to 27 when the cells were saturated, while most MC-RRs stayed within the cells. MC-LR can easily enter the surrounding water body and pose a threat when the water blooms occurred. Our results may help illustrate the influence of tetracycline antibiotics on the production and release of toxin in M. aeruginosa. It is important for environmental protection and evaluation. The results may as well guide the use of antibiotics in agricultural settings.