Assessment of the biodegradability of selected sulfa drugs in two polluted rivers in Poland: Effects of seasonal variations, accidental contamination, turbidity and salinity

A multidirectional pairwise coupling approach with spectral features unmixing to quantify total phosphorus, total nitrogen, and chlorophyll-a in urban rivers

Comprehensive and effective water quality monitoring is vital to water environment management and prevention of water quality from degradation. Unmanned aerial vehicle (UAV) remote sensing techniques have gradually matured and prevailed in monitoring water quality of urban rivers, posing great opportunity for more effective and flexible quantitative estimation of water quality parameter (WQP) than satellite remote sensing techniques. However, current UAV remote sensing methods often entail large quantities of cost-prohibitive in-situ collected training samples with corresponding chemical analysis in different monitoring watersheds, laying time and fiscal pressure on local environmental protection department. They suffer relatively low calculation accuracy and stability and their applicability in various watersheds is constrained. This study developed a unified two-stage method, multidirectional pairwise coupling (MDPC) with information sharing and delivery of different modeling stages to efficiently predict concentrations of WQPs including total phosphorus (TP), total nitrogen (TN), and chlorophyll-a (Chl-a) from hyperspectral data. MDPC incorporates exterior and interior feature interaction and gravity model variant to improve prediction accuracy and stability with consideration of mutual effect in the proximity. The structure design and workflow of MDPC ensure high robustness and application prospect due to achievement of good performance with less training samples, improving applicability and feasibility. The experiments show that MDPC has achieved good performance on retrieval of WQPs concentrations including TP, TN, and Chl-a, the results mean absolute percent error (MAPE) and coefficient of determination (R2) ranging from 6.34 % to 11.94 % and from 0.74 to 0.93. This study provides a systematic and scientific reference to formulate a feasible and efficient water environment management scheme.

Application of Microbiological Screening Tests in Assessment of Environmental Exposure to Antibiotics: Preliminary Studies

Contact of aquatic microbiocenoses with antibiotics present in the environment can cause the former to develop resistance to antimicrobial drugs. Therefore, the search for methods to detect antibiotics and drug-resistant microorganisms in the environment is important. The presented paper proposes a simple procedure to assess environmental exposure to antibiotics and the presence of non-susceptible microorganisms. Medium solutions with selected antibiotics and a microbial growth indicator were applied to test plates, and were inoculated with water samples from various ecosystems. After incubation, the susceptibility of the microorganisms to antibiotics was determined and presented in chronic microbial toxic concentration (MTC) values. It was confirmed that the presented procedure enables the assessment of the antibiotic susceptibility and adaptation potential of unselected microorganisms from different aquatic ecosystems. However, the MTC values depend on the inoculum volume, the density and seasonal activity of the microorganisms, the method of inoculum preparation, and the incubation time of the test plate. The described procedure may be practically applied as a screening test to identify the presence of drug-resistant microorganisms. Additionally, it may also be suitable as a method to assess environmental exposure to antibiotics. However, prior standardisation is required before implementing this procedure in quantitative studies.

Advances and solutions in biological treatment for antibiotic wastewater with resistance genes: A review

Biological treatment represents a fundamental component of wastewater treatment plants (WWTPs). The transmission of antibiotic resistance bacteria (ARB) and resistance genes (ARGs) occurred through the continuous migration and transformation, attributed to the residual presence of antibiotics in WWTPs effluent, posing a significant threat to the entire ecosystem. It is necessary to propose novel biological strategies to address the challenge of refractory contaminants, such as antibiotics, ARGs and ARB. This review summarizes the occurrence of antibiotics in wastewater, categorized by high and low concentrations. Additionally, current biological treatments used in WWTPs, such as aerobic activated sludge, anaerobic digestion, sequencing batch reactor (SBR), constructed wetland, membrane-related bioreactors and biological aerated filter (BAF) are introduced. In particular, because microorganisms are the key to those biological treatments, the effect of high and low concentration of antibiotics on microorganisms are thoroughly discussed. Finally, solutions involving functional bacteria, partial nitrification (PN)-Anammox and lysozyme embedding are suggested from the perspective of the entire biological treatment process. Overall, this review provides valuable insights for the simultaneous removal of antibiotics and ARGs in antibiotics wastewater.

Isolation, identification, and optimization of conditions for the degradation of four sulfonamide antibiotics and their metabolic pathways in Pseudomonas stutzeri strain DLY-21

Overuse of sulfonamides in aquaculture and agriculture leads to residual drugs that cause serious pollution of the environment. However, the residues of sulfonamides in the environment are not unique, and the existing microbial degradation technology has a relatively low degradation rate of sulfonamides. Therefore, in this study, a Pseudomonas stutzeri strain (DLY-21) with the ability to degrade four common SAs was screened and isolated from aerobic compost. Under optimal conditions, the DLY-21 strain degraded four sulfonamides simultaneously within 48 h, and the degradation rates were all over 90%, with the average degradation rates of SAs being sulfoxide (SDM) ≈ sulfachloropyridazine (SCP) > sulfa quinoxaline (SQ) > sulfadiazine (SQ). In addition, the main compounds of the strain DLY-21-degrading SAs were identified by LC-MS analysis. On this basis, four detailed reaction pathways for SA degradation were deduced. This is the first report of the use of a P. stutzeri strain to degrade four sulfonamide antibiotics (SQ, SDM, SCP, and SM1), which can improve the removal efficiency of sulfonamide antibiotic pollutants and thus ameliorate environmental pollution. The results showed that DLY-21 had a good degradation effect on four SAs (SQ, SDM, SCP, and SM1).

Biodegradation, photolysis, and sorption of antibiotics in aquatic environments: A scoping review

The presence of antibiotics in surface waters is a potential driver of antibiotic resistance and thus of concern to human and environmental health. Key factors driving the potential impact of antibiotics are their persistence and transport in rivers and lakes. The goal of this study was to describe the peer-reviewed published literature on the photolysis (direct and indirect), sorption, and biodegradation of a selected group of antibiotic compounds following a scoping review methodology. Primary research from 2000 to 2021 was surveyed to compile information on these processes for 25 antibiotics from 6 classes. After compilation and assessment of the available parameters, the results indicate that information is present to predict the rates of direct photolysis and reaction with hydroxyl radical (an indirect photolysis process) for most of the selected antibiotics. There is insufficient or inconsistent information for including other indirect photolysis processes, biodegradation, or removal via sorption to settling particles for most of the targeted antibiotic compounds. Future research should focus on collecting fundamental parameters such as quantum yields, second-order rate constants, normalized biodegradation rates, and organic carbon or surface area normalized sorption coefficients rather than pseudo-first order rate constants or sorption equilibrium constants that apply only to specific conditions/sites.

Degradation of sulfamethoxazole and antibiotic resistance genes from surface water in the photocatalyst-loading bionic ecosystems

The behavior and removal of sulfamethoxazole (SMX) and 3 typical corresponding antibiotic resistance genes (ARGs) including sul1, sul2, sul3, and 16S rDNA in surface water were investigated in the photocatalyst-loading bionic ecosystems (PCBEs). Synthesized composite photocatalyst g-C3N4/TiO2 showing higher catalytic activity than Fe/g-C3N4/TiO2 was selected in the PCBEs. Five PCBEs, i.e., A-the control (without bionic grass or photocatalyst), B-bionic grass loaded with 4.12 g/m2 g-C3N4/TiO2, C-bionic grass loaded with 8.25 g/m2 g-C3N4/TiO2, D-bionic grass loaded with 12.37 g/m2 g-C3N4/TiO2, and E-bionic grass loaded with 16.5 g/m2 g-C3N4/TiO2 were constructed and operated in a medium-scale running cyclical flume. SMX could be photolyzed efficiently by g-C3N4/TiO2 with an optimal unit load on the bionic grass of 12.37 g/m2. 3-amino-5-methylisooxazole and p-aminobenzene sulfonamide were selected as main intermediates through the analyses of SMX degradation mechanisms and pathways, and detected in the aqueous phase and bionic grass. The intermediates were higher in the underwater part of the bionic grass than the above-water part. The overall removal of SMX ranged from 31.7 % to 82.3 % in 5 PCBEs, and the removal of sul1and sul2 were 0.2 %- 62.9 % in the aqueous phase and 8.4 %-63.2 % in the sediment. PCBE D might be the best construction when SMX and ARGs' removal was considered comprehensively. Moreover, the microbial structures showed Proteobacteria as the most dominant bacterial species had a relative abundance of 22.2 %-26.6 % and 33.4 %-68.2 % in the aquatic phase and sediment respectively, illustrating that the removal of the antibiotic and ARGs was bound up with the variations of dominant bacteria in the ecosystems. The findings illustrated that ecosystems with bionic grass and photocatalysts could be a promising technology for the removal of typical antibiotics and ARGs from surface water.

Copper regulates degradation of typical antibiotics by microalgal-fungal consortium in simulated swine wastewater: insights into metabolic routes and dissolved organic matters

Microalgae-based biotechnology for antibiotics biodegradation in swine wastewater has been receiving an increasing attention. In this study, microalgae and fungi co-cultivation system, regulated by copper (Cu(II)), was investigated in terms of nutrients and sulfonamides degradation in simulated swine wastewater. Results showed that the removal of ammonium nitrogen (NH4+-N), total nitrogen (TN), total phosphorus (TP) and chemical oxygen demand (COD) by microalgal-fungal consortium increased under 0.1-0.5 mg/L Cu(II) with the highest removal efficiency of 79.19%, 76.18%, 93.93% and 93.46%, respectively. The addition of Cu(II) (0-0.5 mg/L) enhanced the removal of sulfamonomethoxine (SMM), sulfamethoxazole (SMX) and sulfamethazine (SMZ) from 49.05% to 58.76%, from 59.31% to 63.51%, and from 37.51% to 63.9%, respectively, and the main removal mechanism was found to be biodegradation. Biodegradation followed a pseudo-first-order model with variable half-lives (10.12 to 15.51 days for SMM, 9.01 to 10.88 days for SMX, and 8.74 to 12.85 days for SMZ). Through mass spectrometry analysis, metabolites and intermediates of sulfonamides were accordingly identified, suggesting that the degradation routes were involved with hydroxylation, deamination, oxidation, de-sulfonation and bond cleavage. Dissolved organic matters released by microalgal-fungal consortium were induced by Cu(II). Fulvic acid-like and protein-like substances were bound to Cu(II), reducing its concentration and thus mitigating the organismal damage to microorganisms. These findings drew an insightful understanding of microalgal-fungal consortium for sulfonamides remediation by Cu(II) regulation in simulated swine wastewater.

Dynamics of drug contamination of the river-water in the rural, semirural and urban areas of the Mrežnica River in Croatia during COVID-19 pandemic (2020-2021)

Increased contamination of aquatic ecosystems with pharmaceuticals could have been expected due to the COVID-19 pandemic. Surface water from three domains (rural, semirural, urban) of the Mrežnica River (Croatia) was screened for 253 pharmaceuticals by SPE-UHPLC-MS/MS. At the beginning of the pandemic, the highest concentration of drugs (excluding veterinary) was detected at urban site (291.4 ng/L), followed by semirural (186.5 ng/L) and rural (141.6 ng/L). With the progression of pandemic, contamination increase was observed at all sites, but it was the most obvious at semirural (approximately 400-700 ng/L). The most pronounced concentration increases were observed for non-opioid analgesics, especially ibuprofen. In September 2021, the first notable occurrence of opioid analgesics was recorded. The most represented group of pharmaceuticals at the start of the pandemic (May 2020) was generally stimulants (caffeine, cotinine). In September 2021, the predominant group was analgesics at all sites (45-84%), whereas stimulants decreased to undetectable levels. The results of this study indicated that the epidemiological measures and medical treatments that were widely imposed/applied caused notable increase of the surface water contamination with drugs of a small river with limited dilution capacity, indirectly pointing to the changes that occurred in the behaviour and habits of the inhabitants of the affected areas.

Characterization and removal mechanism of a novel enrofloxacin-degrading microorganism, Microbacterium proteolyticum GJEE142 capable of simultaneous removal of enrofloxacin, nitrogen and phosphorus

In the study, a novel ENR-degrading microorganism, Microbacterium proteolyticum GJEE142 was isolated from aquaculture wastewater for the first time. The ENR removal of strain GJEE142 was reliant upon the provision of limited additional carbon source, and was adaptative to low temperature (13 ℃) and high salinity (50‰). The ENR removal process, to which intracellular enzymes made more contributions, was implemented in three proposed pathways. During the removal process, oxidative stress response of strain GJEE142 was activated and the bacterial toxicity of ENR was decreased. Strain GJEE142 could also achieve the synchronous removal of ammonium, nitrite, nitrate and phosphorus with the nitrogen removal pathways of nitrate → nitrite → ammonium → glutamine → glutamate → glutamate metabolism and nitrate → nitrite → gaseous nitrogen. The phosphorus removal was implemented under complete aerobic conditions with the assistance of polyphosphate kinase and exopolyphosphatase. Genomic analysis provided corresponding genetic insights for deciphering removal mechanisms of ENR, nitrogen and phosphorus. ENR, nitrogen and phosphorus in both actual aquaculture wastewater and domestic wastewater could be desirably removed. Desirable adaptation, excellent performance and wide distribution will make strain GJEE142 the hopeful strain in wastewater treatment.

Risk Threshold and Assessment of Chloramphenicol Antibiotics in Sediment in the Fenhe River Basin, China

Chloramphenicol antibiotics (CAs) are broad-spectrum antibiotics which are widely used in the prevention and treatment of infectious diseases in livestock and poultry breeding. However, overused CAs can enter the watershed and eventually enter the sediment. Antibiotics in sediment can cause secondary pollution through disturbance and suspension. In this study, taking the Fenhe River Basin as the research area, the risk of CAs in sediment were assessed by collecting sediment samples. The results showed that CAs were detected in all sediment samples of the Fenhe River Basin. The mean concentration of CAs was 79.1 μg/kg, and the concentration of thiamphenicol (THI) was dominant, which was up to 58.3 μg/kg. Temporally, there are great differences in different seasons; the concentration of CAs was higher in winter than that in summer, up to 4.79-174 times. Spatially, the mean concentration of CAs in midstream was 83.5 μg/kg, which was higher than that in the upstream and downstream. The concentration of CAs in tributaries were generally higher than that in the main stream, and the mean concentration of tributaries was 1.1 times that of the main stream. CAs in S2 (Lanhe River) was the most prominent among all sample sites; the concentration of CAs was 190.8 μg/kg. The risk threshold of CAs in the sediment was calculated using the Equilibrium Partitioning approach (EqP), based on the distribution coefficient (Kp) and the predicted no-effect concentration (PNEC) in the water, and the values were 0.091-1.44 mg/kg. Based on the risk threshold, the ecological risk of the CAs in sediment was assessed using risk quotients (RQ). The results showed that the Chloramphenicol (CHL) was the most prominent in the Fenhe River Basin, and the proportion of medium-risk areas reached 21.7%, while all the other areas showed low risk. Secondly, the proportion of medium-risk areas was 17.4% for THI, and all the other areas showed low risk. The risk for Florfenicol (FF) was least among all CAs, and the proportion of low-risk areas was only 8.7%, while all the other areas were of insignificant risk.

Antibiotic residues of drinking-water and its human exposure risk assessment in rural Eastern China

Trace levels of antibiotics were frequently found in drinking-water, leading a growing concern that drinking-water is an important exposure source to antibiotics in humans. In this study, we investigated antibiotics in tap water and well water in two rural residential areas in Eastern China to assess the related human health exposure risks in drinking-water. Twenty-seven antibiotics were analyzed using ultra performance liquid chromatography coupled with triple quadrupole tandem mass spectrometry (UPLC-MS/MS). The average daily dose (ADD) and the health risk quotient (HRQ) for exposure to antibiotics in humans were evaluated using 10000 times of Monte Carlo simulations. Ten antibiotics were detected in drinking-water samples, with the maximum concentrations of antibiotic mixture of 8.29 ng/L in tap water and 2.95 ng/L in well water, respectively. Macrolides and sulfonamides were the predominant contaminants and showed the seasonality. Azithromycin had the highest detection frequencies (79.71-100%), followed by roxithromycin (25.71-100%) and erythromycin (21.43-86.96%). The estimated ADD and HRQ for human exposure to antibiotic mixture through drinking-water was less than 0.01 μg/kg/day and 0.01, respectively, which varied over sites, water types, seasons and sex. Ingestion route was more important than dermal contact route (10-6 to 10-4 μg/kg/day magnitude vs. 10-11 to 10-8 μg/kg/day magnitude). Macrolides also contributed mainly to health exposure risks to antibiotics through drinking-water, whose HRQ accounted for 46% to 67% of the total HRQs. Although the individual antibiotic and their combined effects contributed to acceptable health risks for human, the long-term exposure patterns to low-dose antibiotics in drinking-water should not be ignored.

An extensive assessment of seasonal rainfall on intracellular and extracellular antibiotic resistance genes in Urban River systems

Rainfall events are responsible for the accelerated transfer of antibiotic-resistant contaminants to receiving environments. However, the specific profiles of various ARG types, including intra- and extracellular ARGs (iARGs and eARGs) responding to season rainfall needed more comprehensive assessments. Particularly, the key factors driving the distribution and transport of iARGs and eARGs have not been well characterized. Results revealed that the absolute abundance of eARGs was observed to be more than one order of magnitude greater than that of iARGs during the dry season in the reservoir. However, the absolute abundance of iARGs significantly increased after rainfall (p < 0.01). Meanwhile, seasonal rainfall significantly decreased the diversity of eARGs and the number of shared genes between iARGs and eARGs (p < 0.01). Results of structural equation models (SEM) and network analysis showed the rank and co-occurrence of influencing factors (e.g., microbial community, MGEs, environmental variables, and dissolved organic matter (DOM)) concerning the changes in iARGs and eARGs. DOM contributed majorly to eARGs in the reservoir and pathogens was responsible for eARGs in the river during the wet season. Network analysis revealed that the tnp-04 and IS613 genes-related MGEs co-occurred with eARGs in the dry and wet seasons, which were regarded as potential molecular indicators to shape eARGs profiles in urban rivers. Besides, the results demonstrated close relationships between DOM fluorescence signatures and two-typed ARGs. Specifically, humic acid was significantly and positively correlated with the eARGs in the reservoir during the wet season, while fulvic acid-like substances exhibited strong correlations of iARGs and eARGs in the river during the dry season (p < 0.01). This work provides extensive insights into the potential effect of seasonal rainfall on the dynamic distribution of iARGs and eARGs and the dominance of DOM in driving the fate of two-typed ARGs in urban river systems.

Prioritization, sources, and ecological risk of typical antibiotics in the Huai River, a Chinese major river: a warning about aquaculture

This is the first comprehensive report on antibiotics in the Huai River, a major Chinese river. To illuminate the concentrations, prioritization, spatial distributions, sources, and ecological risks of antibiotics, surface water samples were collected and three types of most widely used antibiotics (16 sulfonamides, 8 tetracyclines, and 14 quinolones) were analyzed. The results indicated that concentrations of ∑quinolones (86 ± 31 ng/L) > ∑tetracyclines (20 ± 13 ng/L) > ∑sulfonamides (11 ± 3.7 ng/L). Oxolinic acid (OXA), cinoxacin(CINX), norfloxacin (NFX), and methacycline (MTC) were the priority antibiotics with mean concentrations > or close to 10 ng/L, however, they were rarely included as target compounds in most previous Chinese investigations. Different spatial distributions of antibiotics were discovered across three reaches separated by two sluices, demonstrating that the sluices may impact antibiotic dissemination. According to the results of the source analysis, the aquaculture industry was the major source of observed antibiotics (49%), followed by livestock & poultry farming (26%) and mixed sources (25%). Because commercial fishing in the Huai River has been prohibited, the aquaculture industry will expand in the next years, and antibiotic contamination caused by the aquaculture industry deserves more attention. The risk quotients were calculated by comparing observed antibiotics to predicted no-effect concentrations, and the results showed that observed antibiotics posed negligible or low integrated risks for Green algae, and medium or low integrated risks for Daphnia magna.

A review of the influence of soil minerals and organic matter on the migration and transformation of sulfonamides

Sulfonamides (SAs) are common antibiotics that are widely present in the environment and can easily migrate in the environment, so they pose an environmental risk. Minerals and organic matter influence the antibiotic migration and transformation in sewage treatment plants, activated sludge, surface water, and soil environment. In the present paper, the influence of the process and mechanism of minerals and organic matter on the adsorption, degradation, and plant uptake of SAs in soil were summarized. In the impact process of mineral and organic matter on the SAs migration and transformation, the pH value is undoubtedly the most important factor because it determines the ionic state of SAs. In terms of influence mechanisms, the minerals absorb SAs well via cation exchange, complexation, H-bonding, and cation bridging. Mineral photodegradation is also one of the primary removal methods for SAs. Soil organic matter (SOM) can significantly increase the SAs adsorption. The adsorption forces of SAs and SOM or dissolved organic matter (DOM) were very similar, but SOM decreased SAs mobility in the environment, while DOM increased SAs availability. DOM generated active substances and aided in the photodegradation of SAs. This review describes the effects of minerals and organic matter on the fate of SAs in soil, which is useful in controlling the migration and transformation of SAs in the soil environment.

Adsorptive removal of antibiotic pollutants from wastewater using biomass/biochar-based adsorbents

This study explores adsorptive removal measures to shed light on current water treatment innovations for kinetic/isotherm models and their applications to antibiotic pollutants using a broad range of biomass-based adsorbents. The structure, classifications, sources, distribution, and different techniques for the remediation of antibiotics are discussed. Unlike previous studies, a wide range of adsorbents are covered and adsorption of comprehensive classes of antibiotics onto biomass/biochar-based adsorbents are categorized as β-lactam, fluoroquinolone, sulfonamide, tetracycline, macrolides, chloramphenicol, antiseptic additives, glycosamides, reductase inhibitors, and multiple antibiotic systems. This allows for an assessment of their performance and an understanding of current research breakthroughs in applying various adsorbent materials for antibiotic removal. Distinct from other studies in the field, the theoretical basis of different isotherm and kinetics models and the corresponding experimental insights into their applications to antibiotics are discussed extensively, thereby identifying the associated strengths, limitations, and efficacy of kinetics and isotherms for describing the performances of the adsorbents. In addition, we explore the regeneration of adsorbents and the potential applications of the adsorbents in engineering. Lastly, scholars will be able to grasp the present resources employed and the future necessities for antibiotic wastewater remediation.

Two low-toxic Klebsiella pneumoniae strains from gut of black soldier fly Hermetia illucens are multi-resistance to sulfonamides and cadmium

In recent years, pollution of antibiotics and heavy metal has often been reported in organic wastes. Saprophytic insects have been recorded as biological control agents in organic waste management. During organic waste conversion, the intestinal bacteria of the saprophytic insects play an important role in digestion, physiology, immunity and prevention of pathogen colonization. Black soldier fly (BSF) Hermetia illucens has been widely used as saprophytic insects and showed tolerance to sulfonamides (SAs) and cadmium (Cd). Diversity and changes in gut microbiota of black soldier fly larvae (BSFL) were evaluated through 16S rRNA high-throughput sequencing, and a decrease in diversity of gut microbiota along with an increase in SAs stress was recorded. Major members identified were Actinomycetaceae, Enterobacteriaceae, and Enterococcaceae. And fourteen multi-resistance Klebsiella pneumoniae strains were isolated. Two strains BSFL7-B-5 (from middle midgut of 7-day BSFL) and BSFL11-C-1 (from posterior midgut of 11-day BSFL) were found to be low-toxic and multi-resistance. The adsorption rate of SAs in 5 mg/kg solutions by these two strains reached 65.2% and 61.6%, respectively. Adsorption rate of Cd in 20 mg/L solutions was 77.2% for BSFL7-B-5. The strain BSFL11-C-1 showed higher than 70% adsorption rates of Cd in 20, 30 and 40 mg/L solutions. This study revealed that the presence of multi-resistance bacterial strains in the gut of BSFL helped the larvae against SAs or Cd stress. After determining how and where they are used, selected BSFL gut bacterial strains might be utilized in managing SAs or Cd contamination at suitable concentrations in the future.

Influence of pH on the Kinetics and Products of Photocatalytic Degradation of Sulfonamides in Aqueous Solutions

The aims of the study were to determine the kinetics of the photocatalytic degradation of six sulfonamides in the presence of TiO2-P25 in acidic, neutral, and alkaline solutions and to identify the structures of the stable products. It was stated that the pH of the solution significantly affected the photocatalytic degradation rate of sulfonamides in acidic and alkaline environments, and the effect likely depended on the susceptibility of sulfonamides to attack by hydroxyl radicals. In the post-reaction mixture, we identified the compounds resulting from the substitution of the aromatic rings with a hydroxyl group; the amide hydrolysis products; the hydroxylamine-, azo, and nitro derivatives; and the compounds formed via the elimination of the sulfone group. Moreover, previously unknown azo compounds were detected. Some degradation products of sulfonamides may exhibit marked bacteriostatic activity and high phytotoxicity. The azo and nitro compounds formed in an acidic environment may be potentially more toxic to aquatic ecosystems than the initial compounds.

Application of duckweed (Lemna sp.) and water fern (Azolla sp.) in the removal of pharmaceutical residues in water: State of art focus on antibiotics

In recent decades, antibiotic residues in the environment have increased, affecting components of biological communities, from bacteria to plants and animals. Different methods have been used to remove these compounds, including phytoremediation with floating aquatic species such as duckweed and aquatic fern, with positive results. This study analyses information about the removal efficiency of drugs, with a focus on antibiotics, using Lemna and Azolla, which will allow a better understanding of phytoremediation processes from the perspective of plant physiology. The physiological processes of macrophytes in an environment with this type of pollutant and the phytotoxic effects on plants at high concentrations are also analysed. The metabolization of toxic compounds occurs in three phases: phase I begins with the absorption of antibiotics and the secretion of reactive oxygen species (ROS); in phase II, the effects of ROS are neutralized and minimized by conjugation with enzymes such as glutathione transferase or metabolites such as glutathione; and phase III culminates with the storage of the assimilated compounds in the vacuoles, apoplast and cell wall. In this way, plants contribute to the removal of toxic compounds. In summary, there is sufficient scientific evidence on the efficiency of the elimination of pharmaceutical compounds by these floating macrophytes at the laboratory scale, which indicates that their application under real conditions can have good results.

Identification and Characterization of HD1, a Novel Ofloxacin-Degrading Bacillus Strain

In recent years, an increasing number of lakes and soils around the world have been polluted by antibiotics, seriously threatening the ecological balance and human health. Currently, there is a lack of understanding of the biodegradation mechanism of typical antibiotics by microorganisms. In this study HD1, a novel Bacillus sp. strain called capable of effectively degrading ofloxacin (OFL), a typical antibiotic with a high detection rate in the environment, was isolated from soil contaminated by OFL. The results of single-factor experiments showed that the optimal conditions for OFL degradation included 30°C, pH 7.0, and 10 g L^–1 NaCl. After 7 days of incubation under aerobic conditions, the degradation efficiency of OFL (5 mg L^–1) was about 66.2%. Five degradation products were detected by LC-MS analysis, and it was deduced that the possible degradation pathways of OFL included the oxidation of the piperazine ring, demethylation, hydroxylation, and methoxy cleavage. Metabolomics analysis indicated that key pathways with the highest difference with HD1 metabolites included the phenylalanine, arginine, and proline metabolism pathways. By regulating energy, amino acid metabolism, and carbohydrate metabolism, HD1 could alleviate OFL stress to degrade better. This study explored the degradation mechanism of OFL by HD1 and provides a theoretical basis and technical support for the remediation of OFL-contaminated environments by functional microorganisms.

Effective degradation of Chlortetracycline using dual bio catalyst

Chlortetracycline (CTC) degradation using potential microbial consortia or individual bacterial strains was useful method for improving bioremediation potential. The co-culture (Klebsiella pneumoniae CH3 and Bacillus amyloliquefaciens CS1) of bacterial strains have the ability to degrade chlortetracycline (91.8 ± 1.7%), followed by sulfamethoxazole (62.1 ± 1.2%) and amoxicillin (73.9 ± 3.3%). It was observed that the degradation potential was maximum after 10 days incubation, 8-10% inoculum, pH 7.5, and antibiotic concentration ranged from 150 to 200 mg/L. The initial concentrations of CTC significantly affected CTC degradation. In strain CH3, maximum biodegradation of CTC (99.4 ± 2.3%) was observed at 200 mg/L initial CTC concentrations. In CS1, maximum biodegradation of CTC was obtained at 150 mg/L concentration (80.5 ± 3.2%) after 10 days of culture. Alkaline pH was found to be suitable for the degradation of antibiotic than acidic range. After initial optimization by one factor at a time approach in free cells, the bacterial strains (CH3 and CS1) were co-immobilized. The co-immobilized bacterial cells showed improved degradation potential than free cells. To determine the biodegradation potential of immobilized cells, the selected strains were immobilized in polymer beads and treated with CTC with 175 mg/L initial concentration. The experimental results revealed that after 3 days of treatment the residual CTC concentration was 150.1 ± 3.2 mg/L and it decreased as 1.28 ± 0.01 mg/L after 10 days of treatment. The present study confirmed the effectiveness and feasibility of biodegradation ability of K. pneumoniae CH3 and B. amyloliquefaciens CS1 immobilized for CTC degradation in wastewater.

Knowledge gaps in the assessment of antimicrobial resistance in surface waters

The spread of antibiotic resistance in the water environment has been widely described. However, still many knowledge gaps exist regarding the selection pressure from antibiotics, heavy metals and other substances present in surface waters as a result of anthropogenic activities, as well as the extent and impact of this phenomenon on aquatic organisms and humans. In particular, the relationship between environmental concentrations of antibiotics and the acquisition of ARGs by antibiotic-sensitive bacteria as well as the impact of heavy metals and other selective agents on antimicrobial resistance (AMR) need to be defined. Currently, established safety values are based on the effects of antibiotic toxicity neglecting the question of AMR spread. In turn, risk assessment of antibiotics in waterbodies remains a complex question implicating multiple variables and unknowns reinforced by the lack of harmonized protocols and official guidelines. In the present review, we discussed current state-of-the-art and the knowledge gaps related to pressure exerted by antibiotics and heavy metals on aquatic environments and their relationship to the spread of AMR. Along with this latter, we reflected on (i) the risk assessment in surface waters, (ii) selective pressures contributing to its transfer and propagation and (iii) the advantages of metagenomics in investigating AMR. Furthermore, the role of microplastics in co-selection for metal and antibiotic resistance, together with the need for more studies in freshwater are highlighted.

Sulfadiazine removal using green zero-valent iron nanoparticles: A low-cost and eco-friendly alternative technology for water remediation

In this work, the effectiveness of green zero-valent iron nanoparticles (gnZVIs) for the removal of the antibiotic sulfadiazine (SDZ) from water via adsorption and reduction was tested. Additionally, the effectiveness of this material as a catalyst for the Fenton and photo-Fenton processes was also investigated. This represents the first study concerning the use of gnZVIs for the degradation of a sulfonamide antibiotic. The results obtained indicate that gnZVIs were able to remove up to 58% of SDZ via adsorption and up to 69% via adsorption plus reduction using a SDZ/Fe³⁺ molar ratio of 1:61.6. Furthermore, gnZVIs showed strong effectiveness as a catalyst for the Fenton and photo-Fenton reactions, with complete SDZ removal in 8 h and 5 min, respectively, using a SDZ/Fe³⁺/H₂O₂ molar ratio of 1:38.4:38.4. These results demonstrate that the use of gnZVIs constitutes an attractive and potential alternative technology for water remediation, reducing environmental impact and operational costs.

The fate of sulfonamides in the process of phytoremediation in hydroponics

Phytoremediation has been proven to be an alternative in-situ treatment technique for sulfonamide polluted wastewater. However, the fate of sulfonamides in the phytoremediation process of multiple sulfonamides coexistence is unclear. Therefore, the possibility and mechanism of phytoremediation of ten sulfonamides by different wetland plants through hydroponics were investigated in this study. The phytoremediation rates of Σsulfonamides by different wetland plants were from 44.5% to 56.9%. Mass balance analysis showed that rhizosphere biodegradation (90.2% - 92.2%) dominated the phytoremediation of Σsulfonamides, while hydrolysis (7.63% - 8.95%) and plant uptake (0.05% - 0.17%) accounted for a small proportion. It is worth mentioning that the dissipation of the target sulfonamides in the hydroponic system followed the first-order reaction kinetic model, with half-lives of 13.3 d to 53.3 d, which are close to or even lower than that of aerobic biodegradation in river water, sediment, and piggery wastewater. Six of the ten spiked sulfonamides were detected in plant samples demonstrated that the selective uptake of plants under the coexistence of multiple sulfonamides. The distribution of sulfonamides (concentrations and uptake amounts) in plant tissues followed the sequence of root > stem > leaf in this study, but the distribution in stems and leaves needs further study. The uptake and rhizosphere biodegradation of Cyperus papyrus to sulfonamides are optimally resulting that its phytoremediation rate is significantly higher than other plants (p < 0.05), which indicates that plant species is one of the key factors affecting the phytoremediation efficiency of sulfonamides. These findings verify the feasibility of phytoremediation of sulfonamides, and provide new insights into the fate of sulfonamides in the process of phytoremediation.

Occurrence, distribution, and partitioning of antibiotics in surface water and sediment in a typical tributary of Yellow River, China

The antibiotic distributions, partitioning, and migration pathways in river basins have withdrawn great attention in the past decades. This study investigates 26 antibiotics of five classifications in surface water and sediment samples at 23 sites in Fenhe River, a typical tributary of Yellow River. There are 21 antibiotics found in the water samples at the concentration from 113.8 to 1106.0 ng/L, in the decreasing order of SAs > QNs > MLs > TCs > CAs. Fifteen antibiotics were detected in the sediment at the concentrations from 25.11 to 73.22 μg/kg following the decreasing order of SAs > MLs > TCs > QNs > CAs. The antibiotic concentrations vary greatly in surface water, generally lower in upstream and in reservoirs, and reaching highest in the midstream of the Fenhe River after passing Taiyuan and Jinzhong, and then lower again in the downstream. The antibiotic concentrations in sediment have a less variation in the entire river basin, but become high in the downstream. The results show the water-sediment partitioning coefficients of antibiotics generally were lower than those in other areas, having a migration path from the water to suspended solids, and then accumulated in sediment. The water-sediment partitioning coefficients also vary across the basin. The water-sediment partitioning coefficients of sulfacetamide and tetracycline are higher than the water-sediment partitioning coefficients of other antibiotics, with less variation across the basin, the water-sediment partitioning coefficients of azithromycin, enrofloxacin, and roxithromycin are low in the midstream of the river, and high at the river source and downstream. The water-sediment partitioning coefficients are significantly affected by the pH of sediment and the particle size of sediment. The prediction models of water-sediment partitioning coefficients for antibiotics are constructed with the selected effecting factors. The simulation values of antibiotics except chlortetracycline and erythromycin are highly consistent with the observed values, indicating that the prediction model is reliable.

Efficiency and Energy Demand in Polishing Treatment of Wastewater Treatment Plants Effluents: Photoelectrocatalysis vs. Photocatalysis and Photolysis

Photoelectrocatalysis (PEC), photolysis (PL), and photocatalysis (PC) were applied to increase the biodegradability of wastewaters effluents sampled from a plant collecting both municipal wastewaters and aqueous waste. In PEC, the catalyst was a porous TiO2 photoanode obtained by plasma electrolytic oxidation and electrically polarized during operation. In PC a dispersion of TiO2 powders was used. The same irradiation shielding, and similar catalyst surface areas were set for PC and PEC, allowing a straightforward evaluation of the catalytic effect of the electrical polarization of TiO2 during operation. Results showed that the chemical oxygen demand (COD) and color removal rates follow the order: PEC > PL and PEC > PC. The specific biodegradability rate (SBR) increased following the same order, the PEC process allowing SBR values more than twice higher than PL and PC. The operating costs were calculated based on the electrical energy per order of COD, color, and SBR values, demonstrating that at the laboratory scale the energy demand of PEC is significantly lower than the other two tested processes.

Sulfadiazine dissipation as a function of soil bacterial diversity

Antibiotic residues in the environment are concerning since results in dispersion of resistance genes. Their degradation is often closely related to microbial metabolism. However, the impacts of soil bacterial community on sulfadiazine (SDZ) dissipation remains unclear, mainly in tropical soils. Our main goals were to evaluate effects of long-term swine manure application on soil bacterial structure as well as effects of soil microbial diversity depletion on SDZ dissipation, using "extinction dilution approach" and ¹⁴C-SDZ. Manure application affected several soil attributes, such as pH, organic carbon (OC), and macronutrient contents as well as bacterial community structure and diversity. Even minor bacterial diversity depletion impacted SDZ mineralization and non-extractible residue (NER) formation rates, but NER recovered along 42 d likely due to soil diversity recovery. However, this period may be enough to spread resistance genes into the environment. Surprisingly, the non-manured natural soil (NS-S1) showed faster SDZ dissipation rate (DT₉₀ = 2.0 versus 21 d) and had a great number of bacterial families involved in major SDZ dissipation pathways (mineralization and mainly NER), such as Isosphaeraceae, Ktedonobacteraceae, Acidobacteriaceae_(Subgroup_1), Micromonosporaceae, and Sphingobacteriaceae. This result is unique and contrasts our hypothesis that long-term manured soils would present adaptive advantages and, consequently, have higher SDZ dissipation rates. The literature suggests instantaneous chemical degradation of SDZ in acidic soils responsible to the fast formation of NER. Our results show that if chemical degradation happens, it is soon followed by microbial metabolism (biodegradation) performed by a pool of bacteria and the newly formed metabolites should favors NER formation since SDZ presented low sorption. It also showed that SDZ mineralization is a low redundancy function.

The remediation of sulfonamides from the environment by Pleurotus eryngii mycelium. Efficiency, products and mechanisms of mycodegradation

The objective of the study was to assess the applicability of the mycelium obtained from the in vitro cultures of nontoxic bracket fungus, Pleurotus eryngii, to sulfonamides mycodegradation. Samples containing one of the six selected sulfonamides, sulfanilamide derivatives, were incubated with the mycelium of P. eryngii for 7 and 14 days in vitro. Subsequently, change in the sulfonamide concentration was assessed in the samples using the UPLC-QTof. The transformation products were identified based on monoisotopic molecular mass and fragmentation spectra. The studied sulfonamides did not inhibit the growth of P. eryngii mycelium in the in vitro cultures. In addition, a considerable reduction of sulfonamide concentration was observed in all the incubated samples (from 73.7 ± 8.3% to 99.8 ± 0.3%). In the case of three sulfonamides, the reduction in concentration >90% occurred after 7 days of incubation. However, the transformation of sulfonamides was partially caused by their degradation to simpler organic compounds. After incubation, the products of condensation of sulfonamides with formyl, acyl, and sugar groups, and amino acid-derived compounds were identified in the samples. This indicated the partially reversible nature of the mycodegradation process.

Tetracycline and Sulfonamide Antibiotics in Soils: Presence, Fate and Environmental Risks

Veterinary antibiotics are widely used worldwide to treat and prevent infectious diseases, as well as (in countries where allowed) to promote growth and improve feeding efficiency of food-producing animals in livestock activities. Among the different antibiotic classes, tetracyclines and sulfonamides are two of the most used for veterinary proposals. Due to the fact that these compounds are poorly absorbed in the gut of animals, a significant proportion (up to ~90%) of them are excreted unchanged, thus reaching the environment mainly through the application of manures and slurries as fertilizers in agricultural fields. Once in the soil, antibiotics are subjected to a series of physicochemical and biological processes, which depend both on the antibiotic nature and soil characteristics. Adsorption/desorption to soil particles and degradation are the main processes that will affect the persistence, bioavailability, and environmental fate of these pollutants, thus determining their potential impacts and risks on human and ecological health. Taking all this into account, a literature review was conducted in order to shed light on the current knowledge about the occurrence of tetracycline and sulfonamide antibiotics in manures/slurries and agricultural soils, as well as on their fate in the environment. For that, the adsorption/desorption and the degradation (both abiotic and biotic) processes of these pollutants in soils were deeply discussed. Finally, the potential risks of deleterious effects on human and ecological health associated with the presence of these antibiotic residues were assessed. This review contributes to a deeper understanding of the lifecycle of tetracycline and sulfonamide antibiotics in the environment, thus facilitating decision-making for the application of preventive and mitigation measures to reduce its negative impacts and risks to public health.

The role of ballast specific gravity and velocity gradient in ballasted flocculation

This study investigated the concealed interaction between applied velocity gradient (G value) and ballast specific gravity (SG) in ballasted flocculation (BF). The objective was to unravel the participation of applied surface concentration (SC: 0.005 m²L^-1-0.02 m²L^-1) of high specific gravity ballasts (SG: 2.9-5.57) in BF aggregation phenomenon at varied velocity gradients (G value: 750s^-1-1250s^-1). Static mixer was used to perform the BF experiments, and aggregated flocs were characterized using charge coupled device (CCD) camera. The results revealed that conventionally adopted velocity gradient (G value: 150s^-1 - 300s^-1) in BF studies was insufficient for efficient floc development due to inadequate suspension of denser ballasts during mixing. This resulted in poor turbidity removal (< 40 %) and immature slow settling flocs (< 25 mh^-1) despite higher ballast consumption. However, appropriate optimization of G value (1250s^-1) corresponding to high specific gravity ballast (SG: 5.57) resulted in 99.5 % turbidity removal (residual turbidity: 1NTU) achieved in a shorter settling interval of 30 s consuming significantly less ballast concentration. This expeditious settling phenomenon was also evident in CCD camera observations of the ballasted flocs achieving superficial settling velocity (105mh^-1). Therefore, it was concluded that appropriate optimization of the G value corresponding to the pertinent concentration of denser ballasts can exhibit rapid elimination of micropollutants, and superficial sedimentation with efficient material and energy use. This can lead to efficient BF design with a short HRT, compact footprint, and ability to handle highly turbid influent.

Kinetic study on the sorption and degradation of antibiotics in the estuarine water: an evaluation based on single and multiple reactions

It is important to study the fate and transport of antibiotics in aquatic environments to reveal their pollution status. The premise behind fate and transport studies is to evaluate the reaction processes of the target antibiotics. However, available research on the environmental behaviors of antibiotics in certain natural waters, such as estuarine water, is scarce. In this study, single reactions such as sorption, biodegradation, and photolysis and multiple degradation reactions of sulfamethoxazole (SMX), trimethoprim (TMP), and ciprofloxacin (CIP) in the estuarine water were studied. The sorption rates of the target antibiotics in the estuarine water-sediment system were very fast, and the sorption amounts varied among sediments and antibiotics. Hydrolysis did not contribute to the degradation of the target antibiotics. Biodegradation had a low contribution to the degradation of the target antibiotics in the estuarine water. In comparison, photolysis was the dominant degradation process for SMX, TMP, and CIP. The rates of photolysis of the tested antibiotics in the estuarine water were greater than those in pure water; thereby, indicating photolysis of these antibiotics was more prone to occur in the estuarine water. In the multiple degradation experiments, it was found that there may be synergistic effects between the single degradation processes. Thus, the aqueous concentrations of antibiotics decreased rapidly by sorption after entering the estuarine water and then decreased relatively slowly by photolysis and biodegradation. This study provides information for evaluating the environmental behaviors of antibiotics in estuarine environments.

The degradation, biodegradability and toxicity evaluation of sulfamethazine antibiotics by gamma radiation

This study evaluated gamma radiation-enhanced sulfamethazine (SMT) degradation, which belongs to the heterocyclic sulfonamides, in different conditions in aqueous solution. The results showed that gamma irradiation could increase the SMT removal in aqueous solution, and the SMT degradation kinetic follow the modified pseudo-first-order kinetic. The degradation rate was nearly 95% at the absorbed dose of 4 kGy. The removal of total organic carbon (TOC) and total nitrogen (TN) could be also induced. When the radiation dose was 5 kGy, the removal rates were only about 6.8% and 10.5% for TOC and TN, respectively. Some ions including HCOO−, CH3COO− and SO42− released during SMT degradation were studied. The biodegradability and toxicity of intermediate products of the SMT degradation were also proposed in this experiment. The biodegradability of the SMT can be improved by the intermediate products of SMT degradation at the radiation dose of 1, 2 and 5 kGy. Gamma radiation could be used as a pretreatment technology before the biodegradation process of pharmaceutical waste water.

Isolation and characterization of a marine bacterium Vibrio diabolicus strain L2-2 capable of biotransforming sulfonamides

Sulfonamides (SAs) have attracted much attention because of their high detection rates in natural water. In this study, a marine bacterium Vibrio diabolicus strain L2-2 was isolated which could metabolize 9 SAs to a different extent. Compared with SAs and their analogs, SAs with N-oxides of heterocyclic structure were easier to be transformed to their N⁴-acetylated metabolites or their isoxazole ring rearrangement isomers by strain L2-2. And, gene vdnatA and vdnatG were likely to be the key genes in SAs acetylation process, which might code Arylamine N-acetyltransferase. The biotransformation rates of sulfathiazole(STZ), sulfamonomethoxine(SMT), sulfadiazine(SDZ), sulfamethoxazole(SMX) and sulfisoxazole(SIX) could reach 29.39 ± 5.63, 24.97 ± 4.45, 79.41 ± 4.05, 64.64 ± 1.71, 32.82 ± 4.46% in 6 days, respectively. Besides, the overall optimal conditions for SAs biotransformation were less than 100 mg/L for total SAs in neutral or weakly alkaline medium with the salinity of 10-20‰ and additional nutrients like glucose, sucrose or glycerine. Furthermore, toxicity was demonstrated to be significantly reduced after biotransformation. Together, this study introduced a strategy to use V. diabolicus strain L2-2 to realize simultaneous removal and detoxification of multiple SAs in freshwater and seawater, and revealed SAs removal pathways and relevant molecular mechanism.

Salinity-independent dissipation of antibiotics from flooded tropical soil: a microcosm study

River deltas are frequently facing salinity intrusion, thus challenging agricultural production in these areas. One adaption strategy to increasing salinity is shrimp production, which however, heavily relies on antibiotic usage. This study was performed to evaluate the effect of increasing salinity on the dissipation rates of antibiotics in tropical flooded soil systems. For this purpose, paddy top soil from a coastal Vietnamese delta was spiked with selected frequently used antibiotics (sulfadiazine, sulfamethazine, sulfamethoxazole, trimethoprim) and incubated with flood water of different salt concentrations (0, 10, 20 g L^-1). Antibiotic concentrations were monitored in water and soil phases over a period of 112 days using liquid chromatography and tandem mass spectrometry. We found that sulfamethazine was the most persistent antibiotic in the flooded soil system (DT₅₀ = 77 days), followed by sulfadiazine (DT₅₀ = 53 days), trimethoprim (DT₅₀ = 3 days) and sulfamethoxazole (DT₅₀ = 1 days). With the exception of sulfamethoxazole, the apparent distribution coefficient increased significantly (p < 0.05) for all antibiotics in course of the incubation, which indicates an accumulation of antibiotics in soil. On a whole system basis, including soil and water into the assessment, there was no overall salinity effect on the dissipation rates of antibiotics, suggesting that common e-fate models remain valid under varying salinity.

Biodegradation of Amoxicillin, Tetracyclines and Sulfonamides in Wastewater Sludge

The removal of antibiotics from the aquatic environment has received great interest. The aim of this study is to examine degradation of oxytetracycline (OTC), tetracycline (TC), chlortetracycline (CTC), amoxicillin (AMO), sulfamethazine (SMZ), sulfamethoxazole (SMX), sulfadimethoxine (SDM) in sludge. Four antibiotic-degrading bacterial strains, SF1 (Pseudmonas sp.), A12 (Pseudmonas sp.), strains B (Bacillus sp.), and SANA (Clostridium sp.), were isolated, identified and tested under aerobic and anaerobic conditions in this study. Batch experiments indicated that the addition of SF1 and A12 under aerobic conditions and the addition of B and SANA under anaerobic conditions increased the biodegradation of antibiotics in sludge. Moreover, the results of repeated addition experiments indicated that the efficiency of the biodegradation of antibiotics using the isolated bacterial strains could be maintained for three degradation cycles. Two groups of potential microbial communities associated with the aerobic and anaerobic degradation of SMX, AMO and CTC in sludge were revealed. Twenty-four reported antibiotics-degrading bacterial genera (Achromobacter, Acidovorax, Acinetobacter, Alcaligenes, Bacillus, Burkholderia, Castellaniella, Comamonas, Corynebacterium, Cupriavidus, Dechloromonas, Geobacter, Gordonia, Klebsiella, Mycobacterium, Novosphingobium, Pandoraea, Pseudomonas, Rhodococcus, Sphingomonas, Thauera, Treponema, Vibrio and Xanthobacter) were found in both the aerobic and anaerobic groups, suggesting that these 24 bacterial genera may be the major antibiotic-degrading bacteria in sludge.

The influence of waste from electronic cigarettes, conventional cigarettes and heat-not-burn tobacco products on microorganisms

Tobacco smoking, especially conventional cigarettes, is widespread throughout the world. Simultaneously, there is a growing interest in new alternative products that allow delivering nicotine to the users' organisms, including electronic cigarettes and heat-not-burn tobacco products. However, there are few scientific reports regarding the effect of waste generated from the above-mentioned products on microorganisms. The aim of the manuscript was to investigate the influence of substances leached from conventional cigarette butts, butts from heat-not-burn tobacco products, cartridges and e-liquids for electronic cigarettes on microorganisms. The commercial multispecies MARA (microbial assay for risk assessment) test and non-selected microorganisms from the Brynica River (Poland), as well as an effluent from the wastewater treatment plant (Sosnowiec-Zagórze, Poland), were used in the ecotoxicity assessment of the investigated waste. The results of the experiments revealed that the waste from electronic cigarettes, i.e. cartridges and e-liquids, does not pose a considerable threat to the microbiocenosis. On the other hand, a particularly strong ecotoxic effect on the investigated microorganisms has been reported for leachate from smoked cigarette butts and butts from heat-not-burn tobacco products. Their high ecotoxicity combined with a high supply is worrying and it can require interventions to protect the aquatic environment. The retention of the waste can have an adverse effect on microorganisms in reservoirs surface waters or a sludge activity in wastewater treatment plants.

Physicochemical properties of antibiotics: A review with an emphasis on detection in the aquatic environment

Antibiotics have extensively been applied to rescue a great number of lives through prevention and treatment of contagious diseases and infections. They are either natural or human-made substances, which are broadly employed for promoting the health condition of human, plant, and animal. However, antibiotics are known to exert detrimental impacts on useful and nontarget microbiota of the biological system due to the overuse, continuous discharge into the environment, and subsequently aggregation in various environmental matrices. Physical and chemical properties help to evaluate whether a substance is more likely to concentrate on the terrestrial, aquatic, or atmospheric environmental matrix as well as its fate. Therefore, appropriate characterization and proper understanding of physicochemical attributes of antibiotics are indispensable to protect ecosystem health. In this paper, the antibiotic classifications and their physicochemical properties were reviewed with emphasis on detection in the aqueous environment. PRACTITIONER POINTS: Antibiotic compounds were classified in main classes, groups, and their main use. Tetracyclines, sulfonamides, aminoglycosides, macrolides, β-lactams, quinolones, polyether ionophores, and glycopeptides are the most commonly detected antibiotics in the aquatic environment. Physical-chemical properties of the main antimicrobial classes were mentioned. Physicochemical properties can change under different environmental conditions such as pH and temperature.

Investigating the biodegradation of sulfadiazine in soil using Enterobacter cloacae T2 immobilized on bagasse

The application of the antibiotic sulfadiazine (SD) in veterinary medicine has created serious environmental issues due to its high mobility and non-degradability. A novel immobilized cell system has been developed and showed significant SD biodegradation potential in soil.

A novel discovery of a heterogeneous Fenton-like system based on natural siderite: A wide range of pH values from 3 to 9

Natural iron-bearing minerals have been proven to be effective for activating H₂O₂ to produce OH, which can be used to degrade organic pollutants. In this study, the performance of siderite to degrade sodium sulfadiazine via catalytic H₂O₂ degradation was investigated at different solution pH values from 3 to 9. An interesting discovery was made: the performance of the siderite-H₂O₂ system was excellent under acidic, neutral, and even alkaline conditions. The influence of various factors (e.g. initial concentration, anions, natural organic matters, etc.) on the system under different pH conditions was investigated, which confirmed that siderite exhibited an excellent catalytic performance. By combining EPR characterization with scavenger research, it was proposed that dissolved iron (Fe²⁺) mainly initiated the homogenous Fenton reaction to degrade pollutants under acidic conditions, while structural Fe²⁺ species present in siderite triggered Fenton-like reactions under neutral or even alkaline conditions. From the SEM and XPS characterizations, oxidation and dissolution of Fe²⁺ on the surface were also observed, confirming our inference concerning the different reaction mechanisms. The experimental findings show that this siderite-H₂O₂ system can be used in solutions with pH values from 3 to 9 and that siderite plays a positive role in soil and groundwater remediation when H₂O₂ is used as an oxidant.

Trends in the occurrence and risk assessment of antibiotics in shallow lakes in the lower-middle reaches of the Yangtze River basin, China

Antibiotics have become a global public concern because of their extensively usage and high toxicity on aquatic organisms, especially leading to the widespread of antibiotic resistance genes. The objective of this study was to evaluate the occurrence, spatial distribution and ecological risks of multi-classes commonly used human and veterinary antibiotics in both aqueous and sedimentary phases of 65 shallow lakes in the lower-middle reaches of the Yangtze River, China. In the target area, antibiotic concentrations in most of lakes (<20 ng/L in the water of 22 lakes and <20 ng/g in the sediments of 43 lakes) were generally lower than those documented in previous studies in China and other countries, and these differences were probably due to less pollutant sources, high temperatures and heavy rainfall in summer. The concentrations of antibiotics in water (>100 ng/L) or sediments (>100 ng/g) of nine lakes, such as Dianshan Lake, Ge Lake and Ce Lake, were comparable to those in rivers and lakes that were seriously polluted by urban and livestock wastewater in China. The Taihu lakes showed relatively higher antibiotic concentrations, followed by the Huaihe River lakes, Poyang lakes and Dongting lakes. The composition of antibiotics showed that agricultural source might be the main source of antibiotics in most of the lakes in the lower-middle reaches of the Yangtze River basin, China. The pseudo distribution coefficient (P-K_d) and significant relationship between antibiotics and environmental factors in the present study suggested the spatial of antibiotics in the lakes might be affected by antibiotics' physiochemical properties and environmental factors. The environmental risk assessment results showed that in general, sulfamethoxazole (SMX), erythromycin (ETM) and ofloxacin (OFX) in the surface water could pose medium risks to algae or bacteria in the aquatic ecosystem, while antibiotics ETM, roxithromycin (RTM), enrofloxacin (EFX) and sulfadiazine (SDZ) in the sediment might pose medium risks to algae or bacteria populations. High potential risk might occur in winter in most lakes due to lower water storage and less degradation. Overall, our study reveals the pollution trends and potential sources of antibiotics in shallow lakes in the lower-middle reaches of the Yangtze River basin.

Anthropogenic impacts on sulfonamide residues and sulfonamide resistant bacteria and genes in Larut and Sangga Besar River, Perak

The environmental reservoirs of sulfonamide (SA) resistome are still poorly understood. We investigated the potential sources and reservoir of SA resistance (SR) in Larut River and Sangga Besar River by measuring the SA residues, sulfamethoxazole resistant (SMX^r) in bacteria and their resistance genes (SRGs). The SA residues measured ranged from lower than quantification limits (LOQ) to 33.13 ng L^-1 with sulfadiazine (SDZ), sulfadimethoxine (SDM) and SMX as most detected. Hospital wastewater effluent was detected with the highest SA residues concentration followed by the slaughterhouse and zoo wastewater effluents. The wastewater effluents also harbored the highest abundance of SMX^r-bacteria (10⁷ CFU mL^-1) and SRGs (10^-1/16S copies mL^-1). Pearson correlation showed only positive correlation between the PO₄ and SMX^r-bacteria. In conclusion, wastewater effluents from the zoo, hospital and slaughterhouse could serve as important sources of SA residues that could lead to the consequent emergence of SMX^r-bacteria and SRGs in the river.

Veterinary pharmaceutical residues from natural water to tap water: Sales, occurrence and fate

Veterinary pharmaceuticals (VPs) increasingly used in animal husbandry have led to their presence in aquatic environments -surface water (SW) or groundwater (GW) - and even in tap water. This review focuses on studies from 2007 to 2017. Sixty-eight different veterinary pharmaceutical residues (VPRs) have been quantified worldwide in natural waters at concentrations ranging from nanograms per liter (ng L^-1) to several micrograms per liter (μg L^-1). An extensive up-to-date on sales and tonnages of VPs worldwide has been performed. Tetracyclines (TCs) antibiotics are the most sold veterinary pharmaceuticals worldwide. An overview of VPRs degradation pathways in natural waters is provided. VPRs can be degraded or transformed by biodegradation, hydrolysis or photolysis. Photo-degradation appears to be the major degradation pathway in SW. This review then reports occurrences of VPRs found in tap water, and presents data on VPRs removal in drinking water treatment plants (DWTPs) at each step of the process. VPRs have been quantified in tap water at ng L^-1 concentration levels in four studies of the eleven studies dealing with VPRs occurrence in tap water. Overall removals of VPRs in DWTPs generally exceed 90% and advanced treatment processes (oxidation processes, adsorption on activated carbon, membrane filtration) greatly contribute to these removals. However, studies performed on full-scale DWTPs are scarce. A large majority of fate studies in DWTPs have been conducted under laboratory at environmentally irrelevant conditions (high concentration of VPRs (mg L^-1), use of deionized water instead of natural water, high concentration of oxidant, high contact time etc.). Also, studies on VPRs occurrence and fate in tap water focus on antibiotics. There is a scientific gap on the occurrence and fate of antiparatic drugs in tap waters.

Degradation of sulfadiazine, sulfachloropyridazine and sulfamethazine in aqueous media

Antibiotics discharged to the environment constitute a main concern for which different treatment alternatives are being studied, some of them based on antibiotics removal or inactivation using by-products with adsorbent capacity, or which can act as catalyst for photo-degradation. But a preliminary step is to determine the general characteristics and magnitude of the degradation process effectively acting on antibiotics. A specific case is that of sulfonamides (SAs), one of the antibiotic groups most widely used in veterinary medicine, and which are considered the most mobile antibiotics, causing that they are frequently detected in both surface- and ground-waters, facilitating their entry in the food chain and causing public health hazards. In this work we investigated abiotic and biotic degradation of three sulfonamides (sulfadiazine -SDZ-, sulfachloropyridazine -SCP-, and sulfamethazine -SMT-) in aqueous media. The results indicated that, in filtered milliQ water and under simulated sunlight, the degradation sequence was: SCP > SDZ ≈ SMT. Furthermore, the rate of degradation clearly increased with the raise of pH: at pH 4.0, half-lives were 1.2, 70.5 and 84.4 h for SCP, SDZ and SMT, respectively, while at pH 7.2 they were 2.3, 9.4 and 13.2 h for SCP, SMT and SDZ. The addition of a culture medium hardly caused any change in degradation rates as compared to experiments performed in milliQ water at the same pH value (7.2), suggesting that in this case sulfonamides degradation rate was not affected by the presence of some chemical elements and compounds, such as sodium, chloride and phosphate. However, the addition of bacterial suspensions extracted from a soil and from poultry manure increased the rate of degradation of these antibiotics. This increase in degradation cannot be attributed to biodegradation, since there was no degradation in the dark during the time of the experiment (72 h). This indicates that photo-degradation constitutes the main removal mechanism for SAs in aqueous media, a mechanism that in this case was favored by humic acids supplied with the extracts from soil and manure. The overall results could contribute to the understanding of the environmental fate of the three sulfonamides studied, aiding to program actions that could favor their inactivation, which is especially relevant since its dissemination can involve serious environmental and public health risks.

Modelled phototransformation kinetics of the antibiotic sulfadiazine in organic matter-rich lakes

Xenobiotic compounds are commonly detected in inland waters. Sunlight-induced photochemical reactions contribute to xenobiotic degradation, but the role of different photoreactions on large geographic scales remains poorly understood. Here, we used a combination of photochemical modelling and large-scale field data from 1020 lakes across Sweden to elucidate the photodegradation kinetics of the commonly used antibiotic sulfadiazine (SDZ) in organic matter-rich lakes. SDZ occurs in two forms, namely acidic HSDZ (pK_a = 6.5) and basic/deprotonated SDZ^-. Both species are oxidised fast by the photogenerated triplet states of natural organic matter (³NOM*). However, they also undergo efficient back reactions because the partially oxidised HSDZ (and SDZ^- to a larger extent) can be reduced back to the initial compounds by the phenolic moieties contained in NOM. Typical lakes in Sweden are rich in NOM and have low pH, with the consequence that SDZ photochemistry would be dominated by HSDZ. Our simulation results showed that SDZ photodegradation kinetics in Swedish lakes would become significantly slower with increasing water depth and pH, while it depended little on latitude, which affects irradiance, or on organic matter content. As a consequence, SDZ would be particularly persistent in lakewater in some densely populated areas with relatively deep and high-pH lakes such as, most notably, the Stockholm region. Here the surface waters could be more heavily contaminated by pharmaceuticals compared to the scarcely populated regions in the centre-north of the country, where lakewater could otherwise promote an efficient photodegradation of SDZ.

Salinity impacts on river ecosystem processes: a critical mini-review

In many dry parts of the world, salinization of water resources threatens freshwater biodiversity and the livelihood of people. However, ecological impact studies remain scarce. Here, we review field-observations of salinity impacts on ecosystem processes such as leaf decomposition, metabolism, biomass production and nutrient cycling, with a special emphasis on dryland ecosystems. In addition, we discuss the potential linkages of these processes to ecosystem service delivery-the benefits that humans derive from ecosystems-as additional nature conservation arguments and the challenges associated with this endeavour.This article is part of the theme issue 'Salt in freshwaters: causes, ecological consequences and future prospects'.

Overview of sulfonamide biodegradation and the relevant pathways and microorganisms

Sulfonamide antibiotics have aroused increasing concerns due to their ability to enhance the resistance of pathogenic bacteria and promote the spread of antibiotic resistance. Biodegradation plays an important role in sulfonamide dissipation in both natural and engineered ecosystems. In this article, we provided an overview of sulfonamide biodegradation in different systems and summarized the relevant sulfonamide-degrading species and metabolic pathways. The removal of sulfonamides depends on a variety of factors, such as the type and initial concentration of sulfonamides, the properties of water or soil, and treatment process. The removal efficiency of sulfonamides by engineered ecosystems can be improved by optimizing their operating conditions. Much higher sulfonamide removal was also observed in upgraded or advanced treatment systems than in conventional activated sludge systems. Ammonia oxidation might promote sulfonamide biodegradation. In addition, sulfonamide-degraders from different bacterial genera have been isolated and classified, but no bioaugmentation practice has been reported. Different pathways have been detected in sulfonamide biodegradation. Further efforts will be necessary to elucidate in-situ degraders and the metabolic pathways and functional genes of sulfonamide biodegradation.

Effects of the antioxidant moieties of dissolved organic matter on triplet-sensitized phototransformation processes: Implications for the photochemical modeling of sulfadiazine

Previous studies have shown that the photodegradation of some pollutants, induced by the excited triplet states of chromophoric dissolved organic matter (³CDOM*), can be inhibited by back-reduction processes carried out by phenolic antioxidants occurring in dissolved organic matter (DOM). Here, for the first time to our knowledge, we included such an inhibition effect into a photochemical model and applied the model predictions to sulfadiazine (SDZ), a sulfonamide antibiotic that occurs in surface waters in two forms, neutral HSDZ and anionic SDZ^- (pK_a = 6.5). The input parameters of the photochemical model were obtained by means of dedicated experiments, which showed that the inhibition effect was more marked for SDZ^- than for HSDZ. Compared to the behavior of 2,4,6-trimethylphenol, which does not undergo antioxidant inhibition when irradiated in natural water samples, the back-reduction effect on the degradation of SDZ was proportional to the electron-donating capacity of the DOM. According to the model results, direct photolysis and OH reaction would account for the majority of both HSDZ and SDZ^- photodegradation in waters having low dissolved organic carbon (DOC < 1 mgC L^-1). With higher DOC values (>3-4 mgC L^-1) and despite the back-reduction processes, the ³CDOM* reactions are expected to account for the majority of HSDZ phototransformation. In the case of SDZ^- at high DOC, most of the photodegradation would be accounted for by direct photolysis. The relative importance of the triplet-sensitized phototransformation of both SDZ^- and (most importantly) HSDZ is expected to increase with increasing DOC, even in the presence of back reduction. An increase in water pH, favoring the occurrence of SDZ^- with respect to HSDZ, would enhance direct photolysis at the expense of triplet sensitization. SDZ should be fairly photolabile under summertime sunlight, with predicted half-lives ranging from a few days to a couple of months depending on water conditions.