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

Dissipation of antibiotics by microalgae: Kinetics, identification of transformation products and pathways

Dissipation potential of four algae viz. Haematococcus pluvialis, Selenastrum capricornutum, Scenedesmus quadricauda and Chlorella vulgaris was investigated against ten antibiotics (sulfamerazine, sulfamethoxazole, sulfamonomethoxine, trimethoprim, clarithromycin, azithromycin, roxithromycin, lomefloxacin, levofloxacin and flumequine) in a series of synthetic wastewater batch culture experiments, maintained at 20, 50 and 100 μg L^-1 initial concentration levels and incubated over a period of 40 days. Generally, the antibiotic removal was achieved with overall dissipation percentage (%) varying among the algal species and different antibiotics. Biodegradation was the major antibiotic removal mechanism from the dissolved fraction, with minor contributions of bioadsorption, bioaccumulation, and abiotic factors. The antibiotics dissipation followed the pseudo-first-order-kinetics with the fastest antibiotic degradation rate achieved by H. pluvialis. The Monod kinetics was successfully applied to explain the relationship between the algal growth and the removal of antibiotics and nutrients in the batch cultures. S. capricornutum and C. vulgaris showed more affinity for the macrolides and fluoroquinolones than sulfonamides, while, H. pluvialis and S. quadiricauda showed relatively higher preference for sulfonamides than the other antibiotic groups. A total of 10 transformation products were identified and the transformation pathway was proposed, accordingly. Most of the transformation products had lower toxicity compared with their parent antibiotics.

A critical review on antibiotics and hormones in swine wastewater: Water pollution problems and control approaches

Swine wastewater (SW) is an important source of antibiotics and hormones (A&H) in the environment due to their large-scale application in swine industry. A&H in SW can be released into the water environment through the direct discharge of SW, effluent from SW treatment plants, and runoff and leaching from farmland polluted by swine wastes. The presence of A&H in the water environment has become an increasing global concern considering their adverse effects to the aquatic organism and human. This review critically discusses: (i) the occurrence of A&H in global water environment and their potential risks to water organisms and human; (ii) the management and technical approaches for reducing the emission of A&H in SW to the water environment. The development of antibiotic alternatives and the enhanced implementation of vaccination and biosecurity are promising management approaches to cut down the consumption of antibiotics during swine production. Through the comparison of different biological treatment technologies for removing A&H in SW, membrane-based bioprocesses have relatively higher and more stable removal efficiencies. Whereas, the combined system of bioprocesses and AOPs is expected to be a promising technology for elimination and mineralization of A&H in swine wastewater. Further study on this system is therefore necessary.

Removal process of antibiotics during anaerobic treatment of swine wastewater

High concentrations of antibiotics in swine wastewater pose potentially serious risks to the environment, human and animal health. Identifying the mechanism for removing antibiotics during the anaerobic treatment of swine wastewater is essential for reducing the serious damage they do to the environment. In this study, batch experiments were conducted to investigate the biosorption and biodegradation of tetracycline and sulfonamide antibiotics (TCs and SMs) in anaerobic processes. Results indicated that the removal of TCs in the anaerobic reactor contributed to biosorption, while biodegradation was responsible for the SMs' removal. The adsorption of TCs fitted well with the pseudo-second kinetic mode and the Freundlich isotherm, which suggested a heterogeneous chemisorption process. Cometabolism was the main mechanism for the biodegradation of SMs and the process fitted well with the first-order kinetic model. Microbial activity in the anaerobic sludge might be curtailed due to the presence of high concentrations of SMs.

Characterization of a novel herbicide and antibiotic-resistant Chlorella sp. with an extensive extracellular matrix

A herbicide and antibiotic-resistant microalgal strain, isolated from a eutrophic site at Giofyros river (Heraklion, Crete, Greece) was extensively characterized. In the presence of relatively high concentrations of common photosynthesis inhibitors (DCMU and atrazine), as well as various antibiotics (spectinomycin, kanamycin, and chloramphenicol), the green microalga was able to increase its biomass in approximately equal levels compared to the control. Despite the high concentrations of the inhibitors, photosynthetic efficiency and chlorophyll a amount per dry cell biomass were comparable to those of control cultures in almost all cases. 18S rDNA analysis showed that this microalga belongs to the Chlorella genus. Optical and electron microscopy studies revealed the presence of an extensive extracellular matrix (EM) that surrounds the cells and plays an important role in colony formation and cell-cell interactions. Fourier transform infrared spectroscopy provided evidence that the EM consists of a polysaccharide. This matrix could be separated from the cells with a simple centrifugation. Depending on growth conditions, the dry cell biomass of this Chlorella strain was found to contain 35-39% proteins and 27-42% carbohydrates. The results of this study have demonstrated that the EM plays a protective role for cell homeostasis maintenance against the various chemical agents. This green microalga is a suitable candidate for further studies regarding sustainable biomass production in waste waters for a series of applications.

Use of microalgae based technology for the removal of antibiotics from wastewater: A review

The antibiotic resistance induced by the release of antibiotics to the environment has urged research towards developing effective technologies for antibiotic removal from wastewater. Traditional technologies such as activated sludge processes are not effective for antibiotic removal. Recently, microalgae-based technology has been explored as a potential alternative for the treatment of wastewater containing antibiotics by adsorption, accumulation, biodegradation, photodegradation, and hydrolysis. In this review, the toxicities of antibiotics on microalgae, the mechanisms of antibiotic removal by microalgae, and the integration of microalgae with other technologies such as ultraviolet irradiation (photocatalysis), advanced oxidation, and complementary microorganism degradation for antibiotic removal were discussed. The limitations of current microalgae-based technology and future research needs were also discussed.

How long-term exposure of environmentally relevant antibiotics may stimulate the growth of Prorocentrum lima: A probable positive factor for red tides

Antibiotics have been widely detected in the ocean and have various impacts on the environment, while knowledge of their chronic influence on phytoplankton, especially red tide algae, is still limited. Dinoflagellates and green algae are common phytoplankton in marine ecosystems. The former is the main red tide algae, and the latter is an important primary producer. We investigated the long-term responses of two representative algae, Prorocentrum lima and Chlorella sp., to two common antibiotics (sulfamethoxazole (SMX) and norfloxacin (NFX)) at environmentally relevant levels (10 and 100 ng/L) during simulated natural conditions. The cell density and activities of three antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD)) were analyzed. The results showed that the influence of each antibiotic on Chlorella sp. was not significant (p > 0.05) during the first 10 days, but the influence of the antibiotics later began to show significant inhibition (p < 0.05) compared with the control group, especially during mixed exposure. P. lima was not inhibited, but its cell density increased. SMX had a superior stimulation effect on P. lima. The three enzymes activities of P. lima increased, and the antioxidant mechanism was not seriously impacted. However, for Chlorella sp., the activity of SOD increased while the activities of CAT and POD decreased, suggesting that this algae's antioxidant system was unbalanced due to oxidative stress. Based on our results, the growth of P. lima was different from green algae Chlorella sp. as well as other inhibited marine algae (such as diatom, golden algae) studied in previous studies. Therefore, as a typical pollutant in the ocean, antibiotics may play a positive role in the bloom of dinoflagellate red tides.

Antimicrobial pharmaceuticals in the aquatic environment - occurrence and environmental implications

The environmental occurrence of antimicrobial pharmaceuticals and antibiotic resistant bacteria and antibiotic resistant genes has become a global phenomenon and a multifaceted threat. Integrated actions of many parties are needed to prevent further aggravation of the problem. Well-directed actions require clear understanding of the problem, which can be ensured by frequent revaluation of the existing knowledge and disseminating it among relevant audiences. The goal of this review paper is to discuss the occurrence and abundance of antimicrobial pharmaceuticals in the aquatic environment in context of adverse effects caused directly by these substances and the threat associated with the antibiotics resistance phenomenon. Several classes of antimicrobial pharmaceuticals (aminoglycosides, β-lactams, glycopeptides, macrolides, fluoroquinolones, sulfonamides and trimethoprim, tetracyclines) have been selected to illustrate their sources, environmental abundance, degradation routes (transformation products) and environmental implications including their ecotoxic effect and the spread of antibiotic resistance within the compartments of the aquatic environment and wastewater treatment plants. Wastewater treatment plants are indeed the main source responsible for the prevalence of these factors in the aquatic environment, since predominantly the plants have not been designed to retain antimicrobial pharmaceuticals. In order to limit the prevalence of these impurities into the environment, better source control is recommended as well as the establishment of stricter environmental quality standards. Counteracting all the above-mentioned threats requires to undertake integrated activities based on cooperation of professionals and scientists from various fields of science or industry, such as environmental sciences, medicine, veterinary, pharmacology, chemical engineering and others.

Occurrence, Distribution, and Ecological Risk of Fluoroquinolones in Rivers and Wastewaters

The use of fluoroquinolones for the treatment of infections in humans and animals has increased in Argentina, and they can be found in large amounts in water bodies. The present study investigated the occurrence and associated ecological risk of 5 fluoroquinolones in rivers and farm wastewaters of San Luis, Santa Fe, Córdoba, Entre Ríos, and Buenos Aires provinces of Argentina by high-performance liquid chromatography coupled to fast-scanning fluorescence detection and ultra-high-performance liquid chromatography coupled to triple quadrupole mass spectrometry detection. The maximum concentrations of ciprofloxacin, enrofloxacin, ofloxacin, enoxacin, and difloxacin found in wastewater were 1.14, 11.9, 1.78, 22.1, and 14.2 μg L^-1 , respectively. In the case of river samples, only enrofloxacin was found, at a concentration of 0.97 μg L^-1 . The individual risk of aquatic organisms associated with water pollution due to fluoroquinolones was higher in bacteria, cyanobacteria, algae, plants, and anurans than in crustaceae and fish, with, in some cases, risk quotients >1. The proportion of samples classified as high risk was 87.5% for ofloxacin, 63.5% for enrofloxacin, 57.1% for ciprofloxacin, and 25% for enoxacin. Our results suggest that the prevalence of fluoroquinolones in water could be potentially risky for the aquatic ecosystem, and harmful to biodiversity. Environ Toxicol Chem 2019;38:2305-2313. © 2019 SETAC.

Antimicrobial resistance in water in Latin America and the Caribbean: a scoping review protocol

OBJECTIVE

The objective of this scoping review is to identify and map existing evidence of antimicrobial resistance (AMR) in water in Latin America and the Caribbean (LAC), while also identifying the gaps in AMR information in the region in eight themes of interest.

INTRODUCTION

Antimicrobial resistance is a public health concern that has gained increasing global awareness. Concerns have been raised toward the importance of the environment's role in the dissemination of clinically relevant AMR. Although studies on AMR have been conducted, the reality of the role of the environment in the LAC region has not been studied.

INCLUSION CRITERIA

Articles that examine AMR in water in the LAC region will be considered for inclusion. Antimicrobial resistance will be defined as a natural process that arises when the microorganisms that cause infection (e.g. bacteria) survive exposure to a drug that would normally kill them or stop their growth. The search will focus on eight themes of interest, as defined in the protocol, relating to the presence of resistant microorganisms in water sources and reported negative health effects. Qualitative and quantitative studies will be considered for inclusion. Reviews and gray literature will be excluded.

METHODS

The proposed scoping review will be conducted in accordance with the JBI methodology for scoping reviews. A search for published literature will be performed in PubMed, Web of Science and Scopus. Independent screening of articles will be performed by examining the abstracts and then the full texts, utilizing pre-defined inclusion and exclusion criteria. Data for specific variables will be extracted, and descriptive examination will be performed.

Moving bed biofilm reactor technology in municipal wastewater treatment: A review

The review encompasses the development of municipal wastewater treatment process using MBBR from early stages, established application, and recent advancements. An overview of main drivers leading to the MBBR technology development over its early stage is discussed. Biocarriers types and features together with biofilm development and role of extracellular polymeric substances (EPS) are presented, ultimately, addressing the challenge in decreasing startup time required for full operation. Furthermore, the review investigates the state of the art of MBBR technology for nutrient removal (i.e., COD and BOD, nitrogen and phosphorus) through process functionality and configuration of established (e.g., IFAS) and under development (e.g. PN/A) applications. Reactor operational characteristics such as filling fractions, mixing properties, dissolved oxygen requirements, and loading rates are presented and related to full scale examples. Current literature discussing the most recent studies on MBBR capability in reduction and removal of chemicals of emerging concern (CEC) released is presented. Ultimately, high rate carbon and nitrogen removal through A/B stage process are examined in its main operational parameters and its application towards energy neutrality suggesting novel MBBR application to further reduce energy requirements and plant footprint.

Current advances in biological swine wastewater treatment using microalgae-based processes

There is an exponential increase in swine farms around the world to meet the increasing demand for proteins, resulting in a significant amount of swine/piggery wastewater. The wastewater produced in swine farms are rich in ammonia with high eutrophication potential and negative environmental impacts. Safe methods for treatment and disposal of swine wastewater have attracted increased research attention in the recent decades. Conventional wastewater treatment methods are limited by the high ammonia content and chemical/biological oxygen demand of swine wastewater. Recently, microalgal cultivation is being proposed for the phytoremediation of swine wastewater. Microalgae are tolerant to high ammonia levels seen in swine wastewater and they also ensure phosphorus removal simultaneously. This review first gives a brief overview on the conventional methods used for swine wastewater treatment. Microalgae-based processes for the clean-up of swine wastewater are discussed in detail, with their potential advantages and limitations. Future research perspectives are also presented.

Graphene and graphene-based nanocomposites used for antibiotics removal in water treatment: A review

Due to their extensive application in human and veterinary medicine, antibiotics have been found worldwide and studied as new pollutants in the aquatic environment. In order to remove such pollutants, adsorption and photocatalysis have attracted tremendous attention because of their great potential in antibiotics removal from aqueous solutions. Graphene, as a novel two-dimensional nanomaterial, possesses unique structure and physicochemical properties, which can be used to efficiently adsorb and photodegrade antibiotics. This review provides an overview of the adsorptive and catalytic properties of graphene, and recent advances in adsorption and photodegradation of antibiotics by graphene and its derivatives. The factors that affect the adsorption and photodegradation of antibiotics are reviewed and discussed. Furthermore, the underlying mechanisms of adsorption and photodegradation are summarized and analyzed. Meanwhile, statistical analysis is conducted based on the number of papers and the maximum adsorption and photodegradation ability on various antibiotics removal. Finally, some unsolved problems together with major challenges that exist in the fabrication and application of graphene-based nanocomposites and the development for antibiotics removal is also proposed. This work provides theoretical guidance for subsequent research in the field of adsorption and photocatalytic removal of antibiotics from aqueous solution, especially on influence factors and mechanisms aspects.

Antibiotic resistance in urban runoff

Aquatic ecosystems subjected to anthropogenic pressures are places of rapid evolution of microbial communities and likely hotspots for selection and emergence of antibiotic resistant bacteria. In urban settings, water quality and the risk of infection are generally assessed in sewers and in effluents of wastewater treatment plants. Physical and chemical parameters as well as the presence of antibiotics, antibiotic-resistant bacteria and genes of resistance are driven by urban activities, with adverse effects on aquatic ecosystems. In this paper we review the environmental pressures exerted on bacterial communities in urban runoff waters and discuss the impact of these settings on antibiotic resistance. Considering the worrisome epidemiology of infectious diseases and estimated mortality due to antimicrobial resistance in the coming decades, there is an urgent need to identify all environmental reservoirs of resistant bacteria and resistance genes to complete our knowledge of the epidemiological cycle and of the dynamics of urban antibiotic resistance.

Identification of contaminants of concern in the upper Tagus river basin (central Spain). Part 1: Screening, quantitative analysis and comparison of sampling methods

Pesticides and point source contaminants (primarily pharmaceuticals) were monitored in 16 sampling sites of the upper Tagus river basin during spring, summer and autumn of 2016. A qualitative screening analysis was performed using a library of 430 compounds. Next, a novel method was implemented for the selection and quantification of contaminants with LC-MS/MS. The method is based on the frequency of detection in the screening, ecotoxicity data and the potential use in the watershed. Moreover, the efficacy of grab samples and passive samples (POCIS) in detecting compound-specific exposure patterns was compared during the summer sampling campaign. The screening method detected the presence of 268 compounds in the study area, out of which 52 were selected for the quantitative analysis (20 pesticides and 32 point source chemicals). Although very helpful in the prioritization exercise, the qualitative screening demonstrated some biases and the need for improvement by using more effective instruments for confirming positive results. Grab samples proved not to be fully suitable for contaminants with discontinuous exposure such as pesticides, which may be underestimated, but offer a sufficient basis for the characterization of contaminants coming from urban wastewaters. All selected chemicals showed a very high concentration variability due to differences among sampling sites, which are related to agricultural intensity and demographic pressure. Some insecticides (chlorpyrifos, dimethoate, imidacloprid), herbicides (diuron, metribuzine, simazine, terbuthylazine), and fungicides (carbendazim) were measured at concentrations exceeding 100 ng/L; while paracetamol, ibuprofen, some antibiotics (azithromycin, sulfamethoxazole, trimethoprim) and life-style compounds (caffeine, paraxanthine, nicotine) were found at very high concentrations (up to several μg/L). The results of this work represent the basis for the development of an ecological risk assessment for the aquatic ecosystem in the upper Tagus river basin and for the identification of basin-specific contaminant mixtures of environmental concern.

Dissolved Organic Matter Modulates Algal Oxidative Stress and Membrane System Responses to Binary Mixtures of Nano-Metal-Oxides (nCeO2, nMgO and nFe3O4) and Sulfadiazine

Joint biomarker responses, oxidative stress and membrane systems, were determined for nano-metal-oxides (nMeO, i.e., nCeO₂, nMgO, and nFe₃O₄) and sulfadiazine (SDZ) exposed at relevant low concentrations to two freshwater microalgae Scenedesmus obliquus and Chlorella pyrenoidosa. The impacts of dissolved organic matter (DOM) on the joint biomarker responses were also investigated. Results indicated that the presence of SDZ significantly decreased the level of intercellular reactive oxygen species (ROS) in the algal cells exposed to each nMeO. Reduction of cell membrane permeability (CMP) and mitochondrial membrane potential (MMP) in the algal cells was observed when the algae were exposed to the mixture of SDZ and the nMeO. The degree of reduction of the ROS level, CMP, and MMP significantly went down with the addition of DOM to a certain extent. Changes in cellular oxidative stress and membrane function depended on the types of both nMeO and algal species. This contribution provides an insight into the hazard assessment of a mixture consisting of emerging contaminants and DOM, as they can coexist in the aquatic environment.

Insight into antibiotics removal: Exploring the photocatalytic performance of a Fe3O4/ZnO nanocomposite in a novel magnetic sequential batch reactor

The purpose of this research was the preparation and photocatalytic evaluation of a novel nanocomposite (NC) based on Fe₃O₄/ZnO, to eliminate four persistent antibiotics in surface waters: sulfamethoxazole, trimethoprim, erythromycin and roxithromycin. Prior to the operation of the photocatalytic reactor, the influence of pH (3-9), catalyst concentration (50-800 mg L^-1), oxidant dose (0-100 mg L^-1) and concentration of different targets (10-100 μg L^-1) on the catalytic efficiency was evaluated. The analysis of reaction kinetics showed that degradation processes of the four antibiotics followed a pseudo-first-order kinetic model. Antibiotics adsorption onto the nanocomposite surface depended on their electrostatic nature and played an important role when decreasing the initial concentration of antibiotics. In this context, kinetic rates were higher at lower initial levels of organic pollutants, which is a favourable effect from a practical application perspective. On the other hand, a synergistic effect of the available Fe in the nanocomposite was found, contributing to the oxidation of antibiotics by photo-Fenton as a secondary reaction. Then, a magnetic photocatalytic reactor was operated under optimal conditions. The enhanced photonic efficiency of Fe₃O₄/ZnO in the system, as well as the ease of the magnetic separation and catalyst reusability, indicate the viability of this reactor configuration.

Impact of erythromycin on a non-target organism: Cellular effects on the freshwater microalga Pseudokirchneriella subcapitata

The increasing and indiscriminate use of antibiotics is the origin of their introduction in aquatic systems through domestic and livestock effluents. The occurrence of erythromycin (ERY), a macrolide antibiotic, in water bodies raises serious concerns about its potential toxic effect in aquatic biota (non-target organisms), particularly in microalgae, the first organisms in contact with aquatic contaminants. This study aimed to evaluate the possible toxic effects of ERY on relevant cell targets of the freshwater microalga Pseudokirchneriella subcapitata. Algal cells incubated with significant environmental ERY concentrations presented disturbance of the photosynthetic apparatus (increased algal autofluorescence and reduction of chlorophyll a content) and mitochondrial function (hyperpolarization of mitochondrial membrane). These perturbations can apparently be attributed to the similarity of the translational machinery of these organelles (chloroplasts and mitochondria) with the prokaryotic cells. P. subcapitata cells treated with ERY showed a modification of metabolic activity (increased esterase activity) and redox state (alteration of intracellular levels of reactive oxygen species and reduced glutathione content) and an increased biovolume. ERY induced an algistatic effect: reduction of growth rate without loss of cell viability (plasma membrane integrity). The present study shows that chronic exposure (72 h), at low (μg L^-1) ERY concentrations (within the range of concentrations detected in surface and ground waters), induce disturbances in the physiological state of the alga P. subcapitata. Additionally, this work alerts to the possible negative impact of the uncontrolled use of ERY on the aquatic systems.

Correlation between antibiotic-induced feeding depression and body size reduction in zooplankton (rotifer, Brachionus calyciflorus): Neural response and digestive enzyme inhibition

The study analyzed the correlation between the antibiotic-induced feeding depression and body size reduction in rotifer, Brachionus calyciflorus, involving exposure, post-exposure and re-exposure periods. The filtration and ingestion rates of the rotifers were inhibited in these three exposure periods at any given concentration of the antibiotic sulfamethazine (SMZ). As food for rotifer, the cell size of the green algae was unchanged, which indicated that it could not drive feeding depression. Secondly, several corresponding physiological responses were considered. Reactive oxygen species (ROS) levels increased in the post-exposure and the re-exposure; acetylcholinesterase (AChE) activity was significantly decreased in the exposure and the re-exposure, whereas it was induced in the post-exposure. The activities of amylase and lipase were always inhibited in these three exposure periods. Additionally, significant decreases in lorica length, width and biovolume of rotifers occurred after the feeding depression. Statistical analysis indicated a positive correlation between the activity of the digestive enzyme and the body size. Our results demonstrated that SMZ could influence the neurotransmission, inhibit the activity of the digestive enzyme, and finally result in body size reduction. These results provided an integrated perspective on assessing the toxicity effects of antibiotic in non-lethal dosage on the feeding behavior of non-target aquatic organisms.

The synergetic effect of a structure-engineered mesoporous SiO2–ZnO composite for doxycycline adsorption

The design and synthesis of an efficient adsorbent for antibiotics-based pollutants is challenging due to the unique physicochemical properties of antibiotics. The development of a mesoporous SiO₂–ZnO composite is a novel way to achieve excellent adsorption efficiency for doxycycline hydrochloride (DOX) in aqueous solutions due to the engineered highly open mesoporous structure and the ZnO-modified framework. Unlike the traditional method of obtaining mesoporous composites by post-synthesis techniques, the novel one-step method developed in this study is both effective and environment-friendly. The adsorption mechanism based on the novel synergetic effect between SiO₂ and ZnO was demonstrated through several experiments. SiO₂ led to the creation of a 3D open framework structure that provides sufficient space and rapid transport channels for adsorption, ensuring rapid adsorption kinetics. A higher number of active sites and enhanced affinity of the contaminants are provided by ZnO, ensuring high adsorption capacity. The mesoporous SiO₂–ZnO could be easily regenerated without a significant decrease in its adsorption efficiency. These results indicate that the developed strategy afforded a simple approach for synthesizing the novel mesoporous composites, and that mesoporous SiO₂–ZnO is a possible alternative adsorbent for the removal of DOX from wastewater.

The design and synthesis of an efficient adsorbent for antibiotics-based pollutants is challenging due to the unique physicochemical properties of antibiotics.

The design of a sunlight-focusing and solar tracking system: A potential application for the degradation of pharmaceuticals in water

Photolysis is considered one of the most important mechanisms for the degradation of pharmaceuticals. Photodecomposition processes to remove pharmaceuticals in water treatment presently use artificial UV light incorporated in advanced oxidation processes. However, UV lighting devices consume a substantial amount of energy and have high operational costs. To develop low energy treatment systems and make good use of abundant sunlight, a natural energy resource as a green technology is needed. As such, a system that combines sunlight focusing, solar tracking and continuous reaction was designed and constructed in the present study, and its application potential as a pharmaceutical water treatment option was tested. Two representative photolabile pharmaceuticals, ciprofloxacin and sulfamethoxazole, were chosen as the target pollutants. The results indicate that the sunlight-focusing system consisting of a UV-enhancing-coated parabolic receiver can concentrate solar energy effectively and hence result in a more than 40% improvement in the direct photolysis efficiency of easily photoconvertible ciprofloxacin. The sunlight-focusing coupled with a solar tracker (SFST) system can improve the sunlight-focusing efficiency by more than 2-fold, thus leading to the maximization of the efficient use of solar energy. Sulfamethoxazole, which is difficult to photoconvert, was successfully degraded by more than 60% compared to direct photolysis through the designed SFST system in the presence of persulfate. The treatment system exhibited good and consistent performance during clear and cloudy days of summer. It is proven that the UV-enhanced coated SFST system with the addition of persulfate indeed has development potential for application in the degradation of pharmaceuticals in water.

Effect of sulfadiazine and trimethoprim on activated sludge performance and microbial community dynamics in laboratory-scale membrane bioreactors and sequencing batch reactors at 8°C

The effect of antibiotics sulfadiazine and trimethoprim on activated sludge operated at 8°C was investigated. Performance and microbial communities of sequencing batch reactors (SBRs) and Membrane Bioreactors (MBRs) were compared before and after the exposure of antibiotics to the synthetic wastewater. The results revealed irreversible negative effect of these antibiotics in environmentally relevant concentrations on nitrifying microbial community of SBR activated sludge. In opposite, MBR sludge demonstrated fast adaptation and more stable performance during the antibiotics exposure. Dynamics of microbial community was greatly affected by presence of antibiotics. Bacteria from classes Betaproteobacteria and Bacteroidetes demonstrated the potential to develop antibiotic resistance in both wastewater treatment systems while Actinobacteria disappeared from all of the reactors after 60 days of antibiotics exposure. Altogether, results showed that operational parameters such as sludge retention time (SRT) and reactor configuration had great effect on microbial community composition of activated sludge and its vulnerability to antibiotics. Operation at long SRT allowed archaea, including ammonium oxidizing species (AOA) such as Nitrososphaera viennensis to grow in MBRs. AOA could have an important role in stable nitrification performance of MBR-activated sludge as a result of tolerance of archaea to antibiotics. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2708, 2019.

Cephalosporin antibiotics in the aquatic environment: A critical review of occurrence, fate, ecotoxicity and removal technologies

Due to their widespread occurrence in the aquatic environment, human and veterinary cephalosporin antibiotics have been studied as water pollutants. In order to characterize environmental risks of this compound class, this review evaluates relevant data about physicochemical properties, occurrence, ecotoxicity and degradation of cephalosporins. Although application of cephalosporins is rather low compared to other antibiotics and their environmental life-time is believed to be short (i.e. days), the available data is insufficient to draw conclusions on their environmental relevance. Few studies concerning the fate of cephalosporins in soil are available, while hydrolysis and photo-degradation are suggested as the main attenuation processes in the aquatic environment. Cephalosporins have been detected in different aqueous matrices in concentrations ranging from 0.30 ng L^-1 to 0.03 mg L^-1, with sewage and wastewater being the main matrices with positive findings. For wastewater treatment purposes, several technologies have been tested for the abatement of cephalosporins, including photolysis and adsorption. In most cases, the technology employed led to complete or significant removal (>95%) of parental drugs but few authors reported on cephalosporins' metabolites and transformation products. Furthermore, the present ecotoxicological data are insufficient for comprehensive ecological risk quotient calculations. Considering the total of 53 cephalosporins, effective values (EC, LC, NOAEC, NOAEL, etc.) are only available for around 30% of parental drugs and are very scarce for cyanobacteria, which is considered to be the most sensitive group of organisms to antibiotics. Furthermore, it has been demonstrated that cephalosporins' transformation products can be more toxic and more persistent than the parental drugs. Few investigations considering this possibility are available. Consequently, more effort on ecotoxicological data generation and verification of biological inactivation of cephalosporins-related products is needed. Likewise, the lack of natural depletion rates and knowledge gaps on mixture effects for cephalosporins' degradation and toxicity have to be overcome.

Pharmaceuticals in the aquatic environments: Evidence of emerged threat and future challenges for marine organisms

Pharmaceuticals are nowadays recognized as a threat for aquatic ecosystems. The growing consumption of these compounds and the enhancement of human health in the past two decades have been paralleled by the continuous input of such biologically active molecules in natural environments. Waste water treatment plants (WWTPs) have been identified as a major route for release of pharmaceuticals in aquatic bodies where concentrations ranging from ng/L to μg/L are ubiquitously detected. Since medicines principles are designed to be effective at very low concentrations, they have the potential to interfere with biochemical and physiological processes of aquatic species over their entire life cycle. Investigations on occurrence, bioaccumulation and effects in non target organisms are fragmentary, particularly for marine ecosystems, and related to only a limited number over the 4000 substances classified as pharmaceuticals: hence, there is a urgent need to prioritize the environmental sustainability of the most relevant compounds. The aim of this review is to summarize the main adverse effects documented for marine species exposed in both field and laboratory conditions to different classes of pharmaceuticals including non-steroidal anti-inflammatory drugs, psychiatric, cardiovascular, hypocholesterolaemic drugs, steroid hormones and antibiotics. Despite a great scientific advancement has been achieved, our knowledge is still limited on pharmaceuticals behavior in chemical mixtures, as well as their interactions with other environmental stressors. Complex ecotoxicological effects are increasingly documented and multidisciplinary, integrated approaches will be helpful to clarify the environmental hazard of these "emerged" pollutants in marine environment.

Occurrence and ecological risk of pharmaceuticals in river surface water of Bangladesh

Pharmaceutical contamination in the aquatic environment is a global issue that affects aquatic animals, micro-organisms and human health. The occurrence and preliminary ecological risk of 12 (11 antibiotics and 1 antiepileptic drug) pharmaceuticals were investigated for the first time in the surface water of the old Brahmaputra River, where open-water-fed aquaculture activities are being practiced in Bangladesh. The pharmaceuticals were quantified by high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS), operated with positive electrospray ionization (ESI⁺) and a multiple reaction monitoring (MRM) mode. Nine pharmaceuticals were detected in the river surface water, whereas three were below the limit of detection (LOD). Metronidazole was detected in all the samples with concentrations ranging from 0.05 to 13.51 ng L^-1. Trimethoprim had the second highest frequency of detection (95%) with the highest concentration (17.20 ng L^-1). The ranges of concentration and detection frequency of sulfonamides and macrolides were <LOD-11.35 and <LOD-16.68 ng L^-1; 35-70 and 60-85%, respectively, whereas carbamazepine was in the range of <LOD-8.80 ng L^-1 and had a detection frequency of 65%. The concentrations of sulfamethoxazole, trimethoprim, erythromycin-H₂O and tylosin were distinctly higher in the fed aquaculture areas. The principal component analysis confirmed that fed aquaculture activities contributed most of the pharmaceutical contamination in the river surface water. Hospitals, nursing homes, sewage wastewater or surface runoff from the surrounding areas might all contribute to the presence of metronidazole and carbamazepine. The preliminary ecological risk assessment revealed that sulfamethoxazole, erythromycin-H₂O and tylosin showed medium risk, and carbamazepine displayed low risk to sensitive aquatic organisms for maximum measured concentrations. Thus, this study suggests that pharmaceutical contamination in different rivers and seasons needs to be quantified, and ecological as well as human health risks need to be assessed in Bangladesh.

Enantioselective degradation of ofloxacin and levofloxacin by the bacterial strains Labrys portucalensis F11 and Rhodococcus sp. FP1

Fluoroquinolones are a class of antibiotics widely prescribed in both human and veterinary medicine of high environmental concern and characterized as environmental micropollutants due to their ecotoxicity and persistence and antibacterial resistance potential. Ofloxacin and levofloxacin are chiral fluoroquinolones commercialized as racemate and in enantiomerically pure form, respectively. Since the pharmacological properties and toxicity of the enantiomers may be very different, understanding the stereochemistry of these compounds should be a priority in environmental monitoring. This work presents the biodegradation of racemic ofloxacin and its (S)-enantiomer levofloxacin by the bacterial strains Labrys portucalensis F11 and Rhodococcus sp. FP1 at a laboratory-scale microcosm following the removal and the behavior of the enantiomers. Strain F11 could degrade both antibiotics almost completely when acetate was supplied regularly to the cultures. Enrichment of the (R)-enantiomer was observed in FP1 and F11 cultures supplied with ofloxacin. Racemization was observed in the biodegradation of the pure (S)-ofloxacin (levofloxacin) by strain F11, which was confirmed by liquid chromatography - exact mass spectrometry. Biodegradation of ofloxacin at 450 µg L^-1 by both bacterial strains expressed good linear fits (R² > 0.98) according to the Rayleigh equation. The enantiomeric enrichment factors were comprised between - 22.5% to - 9.1%, and - 18.7% to - 9.0% in the biodegradation of ofloxacin by strains F11 and FP1, respectively, with no significant differences for the two bacteria under the same conditions. This is the first time that enantioselective biodegradation of ofloxacin and levofloxacin by single bacteria is reported.

Antibiotics and antibiotic resistance genes in global lakes: A review and meta-analysis

Lakes are an important source of freshwater, containing nearly 90% of the liquid surface fresh water worldwide. Long retention times in lakes mean pollutants from discharges slowly circulate around the lakes and may lead to high ecological risk for ecosystem and human health. In recent decades, antibiotics and antibiotic resistance genes (ARGs) have been regarded as emerging pollutants. The occurrence and distribution of antibiotics and ARGs in global freshwater lakes are summarized to show the pollution level of antibiotics and ARGs and to identify some of the potential risks to ecosystem and human health. Fifty-seven antibiotics were reported at least once in the studied lakes. Our meta-analysis shows that sulfamethoxazole, sulfamerazine, sulfameter, tetracycline, oxytetracycline, erythromycin, and roxithromycin were found at high concentrations in both lake water and lake sediment. There is no significant difference in the concentration of sulfonamides in lake water from China and that from other countries worldwide; however, there was a significant difference in quinolones. Erythromycin had the lowest predicted hazardous concentration for 5% of the species (HC₅) and the highest ecological risk in lakes. There was no significant difference in the concentration of sulfonamide resistance genes (sul1 and sul2) in lake water and river water. There is surprisingly limited research on the role of aquatic biota in propagation of ARGs in freshwater lakes. As an environment that is susceptible to cumulative build-up of pollutants, lakes provide an important environment to study the fate of antibiotics and transport of ARGs with a broad range of niches including bacterial community, aquatic plants and animals.

Low-level concentrations of aminoglycoside antibiotics induce the aggregation of cyanobacteria

The interactions between antibiotics and microorganisms have attracted enormous research attentions. In this study, we investigated the effects of two typical aminoglycoside antibiotics on the aggregation of the model cyanobacterium, Synechococcus elongatus, and the dominating strain in algal blooms, Microcystis aeruginosa, via the analysis of zeta potentials, hydrophobicity, and extracellular polymeric substances (EPS) secretion. The results showed that low-level antibiotics promoted the aggregation of S. elongatus and M. aeruginosa by 40 and 18% under 0.10 and 0.02 μg/mL of kanamycin, respectively, which was mainly attributed to the combined effects of increased zeta potentials and the ratio between extracellular proteins and polysaccharides. Tobramycin exerted similar effects. Additionally, we discovered that at low pH (pH 5) and ionic strength (1 mM Na⁺ and 2 mM Mg²⁺), the inducing effects of antibiotics would be even larger than those with higher pH and ionic strength. As aggregation is important to cyanobacteria in either the basic physiology of biofilm formation or the algal bloom, our study demonstrated that low-level antibiotics exert ecological impacts via interfered aggregation. We believe this study will shed light on the mechanisms underlying antibiotic-induced biofilm formation and help with the evaluation of the environmental and ecological risks of antibiotics and other emerging pollutants.

Characterization of antibiotics in a large-scale river system of China: Occurrence pattern, spatiotemporal distribution and environmental risks

Antibiotics and antibiotic resistance genes in the river system have received growing attention in recent years due to their potential threat to aquatic ecosystems and public health. Recognizing the occurrence and distribution of antibiotics in river environment and assessing their ecological risks are of important precondition for proposing effective strategies to protect basin safety. In this study, a comprehensive investigation was conducted to identify the contamination and risk characteristics of antibiotics in the aquatic environment of Hai River system (HRS) which is the largest water system in northern China. To attain this objective, several tools and methods were considered on the data set of water and sediment samples collected in the past ten years. The occurrence pattern, concentration levels and spatiotemporal distribution of antibiotics in the HRS were characterized utilizing statistical and comparative analysis. Risk quotients were employed to assess the adverse ecology effects caused by single antibiotic or their mixtures. Screening tool with priority factor and accumulation growth factor was used auxiliarily to prioritize antibiotics that should be of highly concern. Results indicated that the occurrence frequencies and concentration levels of 16 representative antibiotics in HRS were generally higher than those reported in global waters. Most antibiotics showed significant seasonal and spatial variations. Comparatively speaking, sulfamethoxazole, norfloxacin, erythromycin and roxithromycin posed higher risks to aquatic organisms in the HRS individually, and the combination of tetracycline and enrofloxacin indicated synergistical actions. Overall, due to their potential risks, considerable levels or quick increasing trends, 13 antibiotics were identified as priority contaminants in the HRS and should be paid special attention to be strictly regulated in the future.