Degradation and removal methods of antibiotics from aqueous matrices--a review

Novel Insights into Selection for Antibiotic Resistance in Complex Microbial Communities

Recent research has demonstrated that selection for antibiotic resistance occurs at very low antibiotic concentrations in single-species experiments, but the relevance of these findings when species are embedded in complex microbial communities is unclear. We show that the strength of selection for naturally occurring resistance alleles in a complex community remains constant from low subinhibitory to above clinically relevant concentrations. Selection increases with antibiotic concentration before reaching a plateau where selection remains constant over a 2-order-magnitude concentration range. This is likely to be due to cross protection of the susceptible bacteria in the community following rapid extracellular antibiotic degradation by the resistant population, shown experimentally through a combination of chemical quantification and bacterial growth experiments. Metagenome and 16S rRNA analyses of sewage-derived bacterial communities evolved under cefotaxime exposure show preferential enrichment for bla_CTX-M genes over all other beta-lactamase genes, as well as positive selection and co-selection for antibiotic resistant, opportunistic pathogens. These findings have far-reaching implications for our understanding of the evolution of antibiotic resistance, by challenging the long-standing assumption that selection occurs in a dose-dependent manner.

Antibiotic resistance is one of the greatest global issues facing society. Still, comparatively little is known about selection for resistance at very low antibiotic concentrations. We show that the strength of selection for clinically important resistance genes within a complex bacterial community can remain constant across a large antibiotic concentration range (wide selective space). Therefore, largely understudied ecological compartments could be just as important as clinical environments for selection of antibiotic resistance.

Elimination of Isoxazolyl-Penicillins antibiotics in waters by the ligninolytic native Colombian strain Leptosphaerulina sp. considerations on biodegradation process and antimicrobial activity removal

In this work, Leptosphaerulina sp. (a Colombian native fungus) significantly removed three Isoxazolyl-Penicillin antibiotics (IP): oxacillin (OXA, 16000 μg L^-1), cloxacillin (CLX, 17500 μg L^-1) and dicloxacillin (DCX, 19000 μg L^-1) from water. The biological treatment was performed at pH 5.6, 28 °C, and 160 rpm for 15 days. The biotransformation process and lack of toxicity of the final solutions (antibacterial activity (AA) and cytotoxicity) were tested. The role of enzymes in IP removal was analysed through in vitro studies with enzymatic extracts (crude and pre-purified) from Leptosphaerulina sp., commercial enzymes and enzymatic inhibitors. Furthermore, the applicability of mycoremediation process to a complex matrix (simulated hospital wastewater) was evaluated. IP were considerably abated by the fungus, OXA was the fastest degraded (day 6), followed by CLX (day 7) and DCX (day 8). Antibiotics biodegradation was associated to laccase and versatile peroxidase action. Assays using commercial enzymes (i.e. laccase from Trametes versicolor and horseradish peroxidase) and inhibitors (EDTA, NaCl, sodium acetate, manganese (II) ions) confirmed the significant role of enzymatic transformation. Whereas, biomass sorption was not an important process in the antibiotics elimination. Evaluation of AA against Staphylococcus aureus ATCC 6538 revealed that Leptosphaerulina sp. also eliminated the AA. In addition, the cytotoxicity assay (MTT) on the HepG2 cell line demonstrated that the IP final solutions were non-toxic. Finally, Leptosphaerulina sp. eliminated OXA and its AA from synthetic hospital wastewater at 6 days. All these results evidenced the potential of Leptosphaerulina sp. mycoremediation as a novel environmentally friendly process for the removal of IP from aqueous systems.

Removal of atenolol from aqueous solutions by multiwalled carbon nanotubes modified with ozone: kinetic and equilibrium study

The aim of study is removal of atenolol from aqueous solutions by multiwalled carbon nanotubes modified with ozone. The design of the experiment was adopted across four levels with the L16 matrix arrangement. The factors influencing atenolol adsorption include changes in the pH value, contact time, the dose of the modified multiwall carbon nanotube, and the initial concentration of atenolol in the solution; these factors were evaluated along with the extent of their influence on removal efficiency. Data analyses were performed by the Design Expert 6 software. The results indicated that the pH, contact time, adsorbent dose, and the initial concentration were 7, 20 min, 0.15 g/L and 1 mg/L, respectively. In this state, the removal efficiency was calculated to be 75.79%. The maximum adsorption capacity was obtained as 5.05 mg/g under optimal conditions. The data were analyzed using adsorption models obtained from the isotherm fitting tool software. The results suggested that the data had a greater congruence with the Freundlich model (corrected Akaike information criterion = 2.58). Furthermore, the kinetics of the reactions followed pseudo second order kinetics (R² = 0.95). Based on this study, it can be concluded that modified multiwall carbon nanotubes enjoy high potential and efficiency as adsorbents for the removal of atenolol from aqueous solutions.

Removal of β-lactam antibiotics from pharmaceutical wastewaters using photo-Fenton process at near-neutral pH

In this work, the photo-Fenton process at near-neutral pH was applied for the removal of the β-lactam antibiotic oxacillin (OXA) in water using artificial and sunlight. Initially, the main variables of the process (Fe(II), H₂O₂, and light power) were optimized by a statistical factorial design (2³ with center points). The experimental design indicated that 90 μmol L^-1 of Fe(II), 10 mmol L^-1 of H₂O₂, and 30 W of power light were the favorable conditions for degradation of OXA at 203 μmol L^-1. In the photo-Fenton system, the H₂O₂ alone, UV-light/H₂O₂, and Fe(II)/H₂O₂ subsystems presented a significant participation on antibiotic removal. Moreover, based on the primary organic transformation products, a mechanism of OXA degradation was proposed. Under the favorable operational conditions, both the pollutant and the antimicrobial activity were eliminated after 50 min of process application. Although at 480 min of treatment, only 5% of mineralization was achieved, the level of biodegradability of the solutions increased from 0.08 to 0.98. Interestingly, the presence of pharmaceutical additives (glucose, isopropanol, and oxalic acid) had a moderate interference on the efficiency of the pollutant removal. Additionally, the treatment at pilot scale of the β-lactam antibiotic in a pharmaceutical complex matrix using solar radiation allowed the complete removal of the pollutant and its associated antimicrobial activity in a very short time period (5 min). These results evidenced the applicability of the photo-Fenton process to treat wastewaters from pharmaceutical industry loaded with β-lactam antibiotics at near neutral pH values efficiently.

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.

Enhanced photocatalytic degradation of doxycycline using a magnetic polymer-ZnO composite

A novel magnetic polymer-ZnO composite was prepared by incorporating Fe₃O₄ and ZnO nano-particles in the structure of an adsorbent polymer. Precipitation polymerization was used for synthesizing the adsorbent polymer and its efficiency for extracting doxycycline from aqueous solution was optimized according to several parameters including time, pH and amount of polymer. Results showed the highest extraction efficiency at neutral pH of the doxycycline solution in 20 min, and the capacity of the polymer was about 20 mg/g. The magnetic property of a material is important for fast and facile separation of composite particles after each use. Magnetic polymer-ZnO composite was synthesized by adding Fe₃O₄ and ZnO nano-particles to the polymerization mixture in order to take advantage of both sorption and photocatalytic degradation mechanisms. The obtained composite was characterized using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy equipped with wavelength dispersive X-ray spectroscopy and used for enhanced photocatalytic degradation of doxycycline in aqueous solution. Results showed 76.5% degradation of doxycycline in 6 hours which was significantly higher than the degradation observed by an equivalent amount of ZnO nano-particles. Photocatalytic degradation of doxycycline fitted the pseudo first order kinetic model with a rate constant of 4 × 10^-3 μg mL^-1 min^-1.

Antibiotics in the aquatic environments: A review of lakes, China

The potential threat of antibiotics to the environment and human health has raised significant concerns in recent years. The consumption and production of antibiotics in China are the highest in the world due to its rapid economic development and huge population, possibly resulting in the high detection frequencies and concentrations of antibiotics in aquatic environments of China. As a water resource, lakes in China play an important role in sustainable economic and social development. Understanding the current state of antibiotics in lakes in China is important. Closed and semi-closed lakes provide an ideal medium for the accumulation of antibiotics and antibiotic resistance genes (ARGs). This review summarizes the current levels of antibiotic exposure in relevant environmental compartments in lakes. The ecological and health risks of antibiotics are also evaluated. This review concludes that 39 antibiotics have been detected in the aquatic environments of lakes in China. The levels of antibiotic contamination in lakes in China is relatively high on the global scale. Antibiotic contamination is higher in sediment than water and aquatic organisms. Quinolone antibiotics (QNs) pose the greatest risks. The contents of antibiotics in aquatic organisms are far lower than their maximum residual limits (MRLs), with the exception of the organisms in Honghu Lake. The lakes experience high levels of ARG contamination. A greater assessment of ARG presence and antibiotic exposure are urgent.

Intimate contacted two-dimensional/zero-dimensional composite of bismuth titanate nanosheets supported ultrafine bismuth oxychloride nanoparticles for enhanced antibiotic residue degradation

Constructing a two-dimensional/zero-dimensional (2D/0D) composite with matched crystal structure, suitable energy band structure as well as intimate contact interface is an effective way to improve carriers separation for achieving highly photocatalytic performance. In this work, a novel bismuth titanate/bismuth oxychloride (Bi₄Ti₃O₁₂/BiOCl) composite consisting of 2D Bi₄Ti₃O₁₂ nanosheets and 0D BiOCl nanoparticles was constructed for the first time. Germinating ultrafine BiOCl nanoparticles on Bi₄Ti₃O₁₂ nanosheets can provide abundant contact interface and shorten migration distance of photoinduced carriers via two-step synthesis contained molten salt process and facile chemical transformation process. The obtained Bi₄Ti₃O₁₂/BiOCl 2D/0D composites exhibited enhanced photocatalytic performance for antibiotic tetracycline hydrochloride degradation. The rate constant of optimal Bi₄Ti₃O₁₂/BiOCl composite was about 4.4 times higher than that of bare Bi₄Ti₃O₁₂ although Bi₄Ti₃O₁₂/BiOCl composite appeared lesser photoabsorption. The enhanced photocatalytic performance can be mainly ascribed to matched crystal structure, suitable energy band structure and intimate contact interface between Bi₄Ti₃O₁₂ nanosheets and ultrafine BiOCl nanoparticles as well as unique 2D/0D composite structure. Besides, a probable degradation mechanism on the basis of active species trapping experiments, electrochemical impedance spectroscopy, photocurrent responses and energy band structures was proposed. This work may be stretched to other 2D/0D composite photocatalysts construction, which is inspiring for antibiotic residue treatment.

Evidence for Environmental Dissemination of Antibiotic Resistance Mediated by Wild Birds

The aquatic bird, egret, could carry antibiotic resistance (AR) from a contaminated waterway (Jin River, Chengdu, China) into the surrounding environment (Wangjianglou Park). A systematic study was carried out on the unique environmental dissemination mode of AR mediated by birds. The minimum inhibitory concentrations of various antibiotics against the environmental Escherichia coli isolates were used to evaluate the bacterial AR at the environmental locations where these isolates were recovered, i.e., the Jin River water, the egret feces, the park soil, and the campus soil. The level of AR in the park soil was significantly higher than that in the campus soil that was seldom affected by the egrets, which suggested that the egrets mediated the transportation of AR from the polluted waterway to the park. Genotyping of the resistant E. coli isolates via repetitive-element PCR gave no strong correlation between the genotypes and the AR patterns of the bacteria. So, the transfer of resistant strains should not be the main mode of AR transportation in this process. The results of real-time PCR revealed that the abundance of antibiotic resistance genes (ARGs) and mobile genetic element (MGE) sequences (transposase and integrase genes) declined along the putative transportation route. The transportation of ARGs could be due to their linkage with MGE sequences, and horizontal gene transfer should have contributed to the process. The movable colistin-resistance gene mcr-1 was detected among the colistin-resistant E. coli strains isolated from the river water and the egret feces, which indicated the possibility of the environmental dissemination of this gene. Birds, especially the migratory birds, for the role they played on the dissemination of environmental AR, should be considered when studying the ecology of AR.

Highly efficient degradation of berberine chloride form wastewater by a novel three-dimensional electrode photoelectrocatalytic system

Fe₂O₃/graphite (Fe₂O₃/C) and nano-TiO₂-coated glass bead were prepared by impregnation and sol-gel method respectively and employed as the catalyst of a novel three-dimensional electrode photoelectrocatalytic (3-D PEC) system. The photoexcited electrons can transfer from TiO₂, Fe₂O₃ to counter electrode. It improves the migration of photoexcited charges, retards the fast recombination of electron-hole, and increases the lifetime of photogenerated holes (h⁺). In addition, the cycle reaction of Fe³⁺/Fe²⁺ on Fe₂O₃/C surface enhanced the Fenton reaction which can produce more hydroxyl radicals (·OH) and promote the capacity of mineralization of the pollutants. This novel 3-D PEC system showed excellent performance for the degradation of berberine chloride form (BCF). At the pH value of 3, 93% BCF was removed within 60 min; besides, 98.64% COD removal rate, 78.96% mineralization, 21.47% mineralization current efficiency, and just 3.16 kW h g^-1TOC energy cost were obtained in 120 min. In this study, we proposed the 3-D PEC mechanism. Electron spin resonance (ESR) and scavenging experiments suggest that the major reactive oxygen species (ROS) are superoxide radicals (O₂^·-), ·OH, and h⁺, while the role of sulfate radical (SO₄^·-) is insignificant. This work provides a new dimension for the design of reactors for wastewater treatment and the construction of the 3-D PEC system can potentially be utilized in water purification.

Antibiotic Use in Agriculture and Its Consequential Resistance in Environmental Sources: Potential Public Health Implications

Due to the increased demand of animal protein in developing countries, intensive farming is instigated, which results in antibiotic residues in animal-derived products, and eventually, antibiotic resistance. Antibiotic resistance is of great public health concern because the antibiotic-resistant bacteria associated with the animals may be pathogenic to humans, easily transmitted to humans via food chains, and widely disseminated in the environment via animal wastes. These may cause complicated, untreatable, and prolonged infections in humans, leading to higher healthcare cost and sometimes death. In the said countries, antibiotic resistance is so complex and difficult, due to irrational use of antibiotics both in the clinical and agriculture settings, low socioeconomic status, poor sanitation and hygienic status, as well as that zoonotic bacterial pathogens are not regularly cultured, and their resistance to commonly used antibiotics are scarcely investigated (poor surveillance systems). The challenges that follow are of local, national, regional, and international dimensions, as there are no geographic boundaries to impede the spread of antibiotic resistance. In addition, the information assembled in this study through a thorough review of published findings, emphasized the presence of antibiotics in animal-derived products and the phenomenon of multidrug resistance in environmental samples. This therefore calls for strengthening of regulations that direct antibiotic manufacture, distribution, dispensing, and prescription, hence fostering antibiotic stewardship. Joint collaboration across the world with international bodies is needed to assist the developing countries to implement good surveillance of antibiotic use and antibiotic resistance.

Adsorption of Polyelectrolyte onto Nanosilica Synthesized from Rice Husk: Characteristics, Mechanisms, and Application for Antibiotic Removal

Adsorption of the polyelectrolyte polydiallyldimethylammonium chloride (PDADMAC) onto nanosilica (SiO₂) fabricated from rice husk was studied in this work. Nanosilica was characterized by X-ray diffraction, Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Adsorption of PDADMAC onto SiO₂ increased with increasing pH because the negative charge of SiO₂ is higher at high pH. Adsorption isotherms of PDADMAC onto silica at different KCl concentrations were fitted well by a two-step adsorption model. Adsorption mechanisms of PDADMAC onto SiO₂ are discussed on the basis of surface charge change, evaluation by ζ potential, surface modification by FTIR measurements, and the adsorption isotherm. The application of PDADMAC adsorption onto SiO₂ to remove amoxicillin antibiotic (AMX) was also studied. Experimental conditions such as contact time, pH, and adsorbent dosage for removal of AMX using SiO₂ modified with PDADMAC were systematically optimized and found to be 180 min, pH 10, and 10 mg/mL, respectively. The removal efficiency of AMX using PDADMAC-modified SiO₂ increased significantly from 19.1% to 92.3% under optimum adsorptive conditions. We indicate that PDADMAC-modified SiO₂ rice husk is a novel adsorbent for removal of antibiotics from aqueous solution.

Metal-mediated oxidation of fluoroquinolone antibiotics in water: A review on kinetics, transformation products, and toxicity assessment

Fluoroquinolones (FQs) are among the most potent antimicrobial agents, which have seen their increasing use as human and veterinary medicines to control bacterial infections. FQs have been extensively found in surface water and municipal wastewaters, which has raised great concerns due to their negative impacts to humans and ecological health. It is of utmost importance that FQs are treated before their release into the environment. This paper reviews oxidative removal of FQs using reactive oxygen (O₃ and OH), sulfate radicals (SO₄^-), and high-valent transition metal (Mn^VII and Fe^VI) species. The role of metals in enhancing the performance of reactive oxygen and sulfur species is presented. The catalysts can significantly enhance the production of OH and/or SO₄^- radicals. At neutral pH, the second-order rate constants (k, M^-1s^-1) of the reactions between FQs and oxidants follow the order as k(OH)>k(O₃)>k(Fe^VI)>k(Mn^VII). Moieties involved to transform target FQs to oxidized products and participation of the catalysts in the reaction pathways are discussed. Generally, the piperazinyl ring of FQs was found as the preferential attack site by each oxidant. Meanwhile, evaluation of aquatic ecotoxicity of the transformation products of FQs by these treatments is summarized.

Application of effect-directed analysis to identify mutagenic nitrogenous disinfection by-products of advanced oxidation drinking water treatment

Advanced oxidation processes are important barriers for organic micropollutants in (drinking) water treatment. It is however known that medium pressure UV/H₂O₂ treatment may lead to mutagenicity in the Ames test, which is no longer present after granulated activated carbon (GAC) filtration. Many nitrogen-containing disinfection by-products (N-DBPs) result from the reaction of photolysis products of nitrate with (photolysis products of) natural organic material (NOM) during medium pressure UV treatment of water. Identification of the N-DBPs and the application of effect-directed analysis to combine chemical screening results with biological activity would provide more insight into the relation of specific N-DBPs with the observed mutagenicity and was the subject of this study. To this end, fractions of medium pressure UV-treated and untreated water extracts were prepared using preparative HPLC and tested using the Ames fluctuation test. In addition, high-resolution mass spectrometry was performed on all fractions to assess the presence of N-DBPs. Based on toxicity data and read across analysis, we could identify five N-DBPs that are potentially genotoxic and were present in relatively high concentrations in the fractions in which mutagenicity was observed. The results of this study offer opportunities to further evaluate the identity and potential health concern of N-DBPs formed during advanced oxidation UV drinking water treatment.

Waste-based alternative adsorbents for the remediation of pharmaceutical contaminated waters: Has a step forward already been taken?

When adsorption is considered for water treatment, commercial activated carbon is usually the chosen adsorbent for the removal of pollutants from the aqueous phase, particularly pharmaceuticals. In order to decrease costs and save natural resources, attempts have been made to use wastes as raw materials for the production of alternative carbon adsorbents. This approach intends to increase efficiency, cost-effectiveness, and also to propose an alternative and sustainable way for the valorization/management of residues. This review aims to provide an overview on waste-based adsorbents used on pharmaceuticals' adsorption. Experimental facts related to the adsorption behaviour of each adsorbent/pharmaceutical pair and some key factors were addressed. Also, research gaps that subsist in this research area, as well as future needs, were identified. Simultaneously, this review aims to clarify the current status of the research on pharmaceuticals' adsorption by waste-based adsorbents in order to recognize if the right direction is being taken.

What happens with organic micropollutants during UV disinfection in WWTPs? A global perspective from laboratory to full-scale

The phototransformation of 18 organic micropollutants (OMPs) commonly detected in wastewater treatment plant (WWTP) effluents was examined attempting to explain their fate during UV disinfection in WWTPs. For this purpose, a lab-scale UV reactor (lamp emitting at 254nm) was used to study the influence of the operational conditions (UV dose, temperature and water matrix) on OMPs abatement and disinfection efficiency. Chemical properties of OMPs and the quality of treated effluent were identified as key factors affecting the phototransformation rate of these compounds. Sampling campaigns were carried out at the inlet and outlet of UV systems of three WWTPs, and the results evidenced that only the most photosensitive compounds, such as sulfamethoxazole and diclofenac, are eliminated. Therefore, despite UV treatment is an effective technology to phototransform OMPs, the UV doses typically applied for disinfection (10-50mJ/cm²) are not sufficient to remove them. Consequently, small modifications (increase of UV dose, use of catalysts) should be applied in WWTPs to enhance the abatement of OMPs in UV systems.

Biodegradation of sulfonamides by Shewanella oneidensis MR-1 and Shewanella sp. strain MR-4

Because of extensive sulfonamides application in aquaculture and animal husbandry and the consequent increase in sulfonamides discharged into the environment, strategies to remediate sulfonamide-contaminated environments are essential. In this study, the resistance of Shewanella oneidensis MR-1 and Shewanella sp. strain MR-4 to the sulfonamides sulfapyridine (SPY) and sulfamethoxazole (SMX) were determined, and sulfonamides degradation by these strains was assessed. Shewanella oneidensis MR-1 and Shewanella sp. strain MR-4 were resistant to SPY and SMX concentrations as high as 60 mg/L. After incubation for 5 days, 23.91 ± 1.80 and 23.43 ± 2.98% of SPY and 59.88 ± 1.23 and 63.89 ± 3.09% of SMX contained in the medium were degraded by S. oneidensis MR-1 and Shewanella sp. strain MR-4, respectively. The effects of the initial concentration of the sulfonamides and initial pH of the medium on biodegradation, and the degradation of different sulfonamides were assessed. The products were measured by LC-MS; with SPY as a substrate, 2-AP (2-aminopyridine) was the main stable metabolite, and with SMX as a substrate, 3A5MI (3-amino-5-methyl-isoxazole) was the main stable metabolite. The co-occurrence of 2-AP or 3A5MI and 4-aminobenzenesulfonic acid suggests that the initial step in the biodegradation of the two sulfonamides is S-N bond cleavage. These results suggest that S. oneidensis MR-1 and Shewanella sp. strain MR-4 are potential bacterial resources for biodegrading sulfonamides and therefore bioremediation of sulfonamide-polluted environments.

Recognition of trace organic pollutant and toxic metal ions via a tailored fluorescent metal–organic coordination polymer in water environment

A novel fluorescence material H₂Sr₂(bqdc)₃(phen)₂ (1) for trace recognition of organic pollutant and toxic metal ions is designed and prepared by two weak fluorescent ligands and Sr²⁺. The latter was selected although it played no role in the modulation process of luminescence and despite low-cost, alkaline earth, metal–organic coordination polymers lacking competitive functionality. The strong fluorescence of the fluorescence material was based on the propeller configuration of the metal–organic coordination polymer, which was characterized by X-ray single crystal diffraction showing that the N active sites inside the crystal channels can interact with external guests. Convenient fluorescence detection of 3-AT can be realized using an ultraviolet lamp and test strip and the determination of Cd²⁺ showed good reusability with a detection limit of 1 × 10⁻⁹ mol L⁻¹, which is lower than the standard stipulated by the Environmental Protection Agency. Detailed experiments results revealed that the material was a promising candidate for specifically recognizing amitrole and Cd²⁺ because of its selective fluorescence quenching and sensitive detection in water.

Complexes with strong fluorescence can conveniently detect the trace organic pollutant amitrole and repeatedly recognize toxic Cd²⁺with a low detection limit.

Synthesis of CdSe quantum dots decorated SnO2 nanotubes as anode for photo-assisted electrochemical degradation of hydrochlorothiazide: Kinetic process

Pharmaceutical residues have been increasingly detected in the aquatic environment and are considered important contaminants of emerging concern. This study examines the photo assisted electrochemical degradation of the Hydrochlorothiazide by using CdSe quantum dots decorated SnO₂ nanotubes. The characteristic devices such as Scanning electron microscopy, X-ray diffraction, UV-vis diffuse reflectance Transmission electron Microscopy were used to analyze information structure of CdSe QDs/SnO₂ nanotubes. All the experiments were perform with influence of the current density (10-60mAcm^-2) and sodium chloride (0.02-0.10molL^-1) in the supporting electrolyte composition was analyzed. The results showed that the Hydrochlorothiazide and TOC removal was achieved in the current density range used. As expected, the degradation kinetics presented a pseudo first order behavior. Comparison of the efficiencies of the photocatalytic, electrochemical (EC) and photo-assisted electrochemical (PAEC) techniques verified that the combined process showed a synergism for HCT and TOC removal.

Efficient Removal of Tetracycline from Aqueous Media with a Fe₃O₄ Nanoparticles@graphene Oxide Nanosheets Assembly

A readily separated composite was prepared via direct assembly of Fe₃O4 magnetic nanoparticles onto the surface of graphene oxide (GO) (labeled as Fe₃O₄@GO) and used as an adsorbent for the removal of tetracycline (TC) from wastewater. The effects of external environmental conditions, such as pH, ionic strength, humic acid (HA), TC concentration, and temperature, on the adsorption process were studied. The adsorption data were analyzed by kinetics and isothermal models. The results show that the Fe₃O₄@GO composite has excellent sorptive properties and can efficiently remove TC. At low pH, the adsorption capacity of Fe₃O₄@GO toward TC decreases slowly with increasing pH value, while the adsorption capacity decreases rapidly at higher pH values. The ionic strength has insignificant effect on TC adsorption. The presence of HA affects the affinity of Fe₃O₄@GO to TC. The pseudo-second-order kinetics model and Langmuir model fit the adsorption data well. When the initial concentration of TC is 100 mg/L, a slow adsorption process dominates. Film diffusion is the rate limiting step of the adsorption. Importantly, Fe₃O₄@GO has good regeneration performance. The above results are of great significance to promote the application of Fe₃O₄@GO in the treatment of antibiotic wastewater.

Removal of antibiotics (sulfamethazine, tetracycline and chloramphenicol) from aqueous solution by raw and nitrogen plasma modified steel shavings

The removal of sulfamethazine (SMT), tetracycline (TC) and chloramphenicol (CP) from synthetic wastewater by raw (M₃) and nitrogen plasma modified steel shavings (M₃-plN₂) was investigated using batch experiments. The adsorption kinetics could be expressed by both pseudo-first-order kinetic (PFO) and pseudo-second-order kinetic (PSO) models, where correlation coefficient r² values were high. The values of PFO rate constant k_1p and PSO rate constant k_2p decreased as SMT-M₃>SMT-M₃-plN₂>TC-M₃-plN₂>TC-M₃>CP-M₃>CP-M₃-plN₂ and SMT-M₃>SMT-M₃-plN₂>TC-M₃>TC-M₃-plN₂>CP-M₃>CP-M₃-plN₂, respectively. Solution pH, adsorbent dose and temperature exerted great influences on the adsorption process. The plasma modification with nitrogen gas cleaned and enhanced 1.7-fold the surface area and 1.4-fold the pore volume of steel shavings. Consequently, the removal capacity of SMT, TC, CP on the adsorbent rose from 2519.98 to 2702.55, 1720.20 to 2158.36, and 2772.81 to 2920.11μg/g, respectively. Typical chemical states of iron (XPS in Fe2p3 region) in the adsorbents which are mainly responsible for removing antibiotics through hydrogen bonding, electrostatic and non- electrostatic interactions and redox reaction were as follows: Fe₃O₄/Fe²⁺, Fe₃O₄/Fe³⁺, FeO/Fe²⁺ and Fe₂O₃/Fe³⁺.

Redox-mediator-free degradation of sulfathiazole and tetracycline using Phanerochaete chrysosporium

The removal of two of the most commonly used antibiotics, tetracycline (TC) and sulfathiazole (STZ), using laccase-producing Phanerochaete chrysosporium was studied in liquid-phase batch experiments in the absence of any synthetic redox mediator. The removal of STZ and TC from single antibiotic spikes varied from 97.8% to 15.4% and 98.8% to 31%, respectively, with increasing initial doses of 10-250 mg L^-1 within 14 days of incubation. The enzyme activity of P. chrysosporium was only minimally influenced by the concentrations of these antibiotics. The degradation of antibiotics initiated before an appreciable extracellular enzyme activity was noted in the fungal culture. The appearance of low-molecular weight molecular fragments from parent antibiotics in liquid chromatography-mass spectrometry confirmed the biodegradation process.

Mechanism of Ampicillin Degradation by Non-Thermal Plasma Treatment with FE-DBD

This research focused on determining the effectiveness of non-thermal atmospheric pressure plasma as an alternative to advanced oxidation processes (AOP) for antibiotic removal in solution. For this study, 20 mM (6.988 g/L) solutions of ampicillin were treated with a floating electrode dielectric barrier discharge (FE-DBD) plasma for varying treatment times. The treated solutions were analyzed primarily using mass spectrometry (MS) and nuclear magnetic resonance spectroscopy (NMR). The preliminary product formed was Ampicillin Sulfoxide, however, many more species are formed as plasma treatment time is increased. Ampicillin was completely eliminated after five minutes of air-plasma treatment. The primary mechanism of ampicillin degradation by plasma treatment is investigated in this study.

Electrochemical treatment of penicillin, cephalosporin, and fluoroquinolone antibiotics via active chlorine: evaluation of antimicrobial activity, toxicity, matrix, and their correlation with the degradation pathways

Antibiotics are pharmaceuticals widely consumed and frequently detected in environmental water, where they can induce toxic effects and development of resistant bacteria. Their structural variety makes the problem of antibiotics in natural water more complex. In this work, six highly used antibiotics (at 40 μmol L^-1) belonging to three different classes (penicillins, cephalosporins, and fluoroquinolones) were treated using an electrochemical system with a Ti/IrO₂ anode and a Zr cathode in the presence of NaCl (0.05 μmol L^-1). The attack of electrogenerated active chlorine was found to be the main degradation route. After only 20 min of treatment, the process decreased more than 90% of the initial concentration of antibiotics, following the degradation order: fluoroquinolones > penicillins > cephalosporins. The primary interactions of the degrading agent with fluoroquinolones occurred at the cyclic amine (i.e., piperazyl ring) and the benzene ring. Meanwhile, the cephalosporins and penicillins were initially attacked on the β-lactam and sulfide groups. However, the tested penicillins presented an additional reaction on the central amide. In all cases, the transformations of antibiotics led to the antimicrobial activity decreasing. On the contrary, the toxicity level showed diverse results: increasing, decreasing, and no change, depending on the antibiotic type. In fact, due to the conservation of quinolone nucleus in the fluoroquinolone by-products, the toxicity of the treated solutions remained unchanged. With penicillins, the production of chloro-phenyl-isoxazole fragments increased the toxicity level of the resultant solution. However, the opening of β-lactam ring of cephalosporin antibiotics decreased the toxicity level of the treated solutions. Finally, the application of the treatment to synthetic hospital wastewater and seawater containing a representative antibiotic showed that the high amount of chloride ions in seawater accelerates the pollutant degradation. In contrast, the urea and ammonium presence in the hospital wastewater retarded the removal of this pharmaceutical.

Study of the simulated sunlight photolysis mechanism of ketoprofen: the role of superoxide anion radicals, transformation byproducts, and ecotoxicity assessment

The aim of this study was to investigate the photolysis mechanism of ketoprofen (KET) under simulated sunlight. The results demonstrated that the photolysis of KET aligned well with pseudo first-order kinetics. Radical scavenging experiments and dissolved oxygen experiments revealed that the superoxide anion radical (O₂˙^-) played a primary role in the photolytic process in pure water. Bicarbonate slightly increased the photodegradation of KET through generating carbonate radicals, while DOM inhibited the photolysis via both attenuating light and competing radicals. Moreover, Zhujiang river water inhibited KET phototransformation. Potential KET degradation pathways were proposed based on the identification of products using LC/MS/MS and GC/MS techniques. The theoretical prediction of reaction sites was derived from Frontier Electron Densities (FEDs), which primarily involved the KET decarboxylation reaction. The ecotoxicity of the treated solutions was evaluated by employing Daphnia magna and V. fischeri as biological indicators. Ecotoxicity was also hypothetically predicted through the "ecological structure-activity relationship" (ECOSAR) program, which revealed that toxic products might be generated during the photolysis process.

Anaerobic Membrane Bioreactor Effluent Reuse: A Review of Microbial Safety Concerns

Broad and increasing interest in sustainable wastewater treatment has led a paradigm shift towards more efficient means of treatment system operation. A key aspect of improving overall sustainability is the potential for direct wastewater effluent reuse. Anaerobic membrane bioreactors (AnMBRs) have been identified as an attractive option for producing high quality and nutrient-rich effluents during the treatment of municipal wastewaters. The introduction of direct effluent reuse does, however, raise several safety concerns related to its application. Among those concerns are the microbial threats associated with pathogenic bacteria as well as the emerging issues associated with antibiotic-resistant bacteria and the potential for proliferation of antibiotic resistance genes. Although there is substantial research evaluating these topics from the perspectives of anaerobic digestion and membrane bioreactors separately, little is known regarding how AnMBR systems can contribute to pathogen and antibiotic resistance removal and propagation in wastewater effluents. The aim of this review is to provide a current assessment of existing literature on anaerobic and membrane-based treatment systems as they relate to these microbial safety issues and utilize this assessment to identify areas of potential future research to evaluate the suitability of AnMBRs for direct effluent reuse.

Contaminants of emerging concern: a review of new approach in AOP technologies

The presence of contaminants of emerging concern (CECs) such as pharmaceuticals and personal care products (PPCPs), endocrine-disrupting compounds (EDCs), flame retardants (FRs), pesticides, and artificial sweeteners (ASWs) in the aquatic environments remains a major challenge to the environment and human health. In this review, the classification and occurrence of emerging contaminants in aquatic environments were discussed in detail. It is well documented that CECs are susceptible to poor removal during the conventional wastewater treatment plants, which introduce them back to the environment ranging from nanogram per liter (e.g., carbamazepine) up to milligram per liter (e.g., acesulfame) concentration level. Meanwhile, a deep insight into the application of advanced oxidation processes (AOPs) on mitigation of the CECs from aquatic environment was presented. In this regard, the utilization of various treatment technologies based on AOPs including ozonation, Fenton processes, sonochemical, and TiO₂ heterogeneous photocatalysis was reviewed. Additionally, some innovations (e.g., visible light heterogeneous photocatalysis, electro-Fenton) concerning the AOPs and the combined utilization of AOPs (e.g., sono-Fenton) were documented.

Ferrous-activated peroxymonosulfate oxidation of antimicrobial agent sulfaquinoxaline and structurally related compounds in aqueous solution: kinetics, products, and transformation pathways

Sulfaquinoxaline (SQX) is a coccidiostatic drug widely used in poultry and swine production and has been frequently detected in various environmental compartments such as surface water, groundwater, soils, and sediments. In the present study, degradation of SQX by ferrous ion-activated peroxymonosulfate oxidation process (Fe(II)/PMS), a promising in situ chemical oxidation (ISCO) technique, was systematically investigated. Experimental results showed that Fe(II)/PMS process appeared to be more efficient for SQX removal relative to Fe(II)/persulfate process (Fe(II)/PS). An optimal Fe(II):PMS molar ratio of 1:1 was found to be necessary for efficient removal of SQX. Increasing the solution pH hampered the degradation of SQX, and no enhancement in SQX degradation was observed when chelating agents S,S'-ethylenediamine-N,N'-disuccinic acid (EDDS) and citrate were present. The presence of Suwannee River fulvic acid (SRFA), as a representative of aquatic natural organic matter (NOM), could inhibit the degradation of SQX. SQX was more susceptible to Fe(II)/PMS oxidation in comparison to its substructural analog 2-amino-quinoxaline (2-AQ) and other sulfonamides, i.e., sulfapyridine (SPD) and sulfadiazine (SDZ). Transformation products of SQX were enriched by solid-phase extraction (SPE) and identified by liquid chromatography-electrospray ionization-triple quadrupole mass spectrometry (LC-ESI-MS/MS). On the basis of the TPs identified, detailed reaction pathways for SQX degradation including sulfonamide bond cleavage, SO₂ extrusion, and aniline moiety oxidation were proposed. Our contribution may provide some useful information for better understanding the kinetics and mechanisms of SQX degradation by sulfate radical-based advanced oxidation processes (SR-AOPs).

Bioinspired Synthesis of Photocatalytic Nanocomposite Membranes Based on Synergy of Au-TiO2 and Polydopamine for Degradation of Tetracycline under Visible Light

A bioinspired photocatalytic nanocomposite membrane was successfully prepared via polydopamine (pDA)-coated poly(vinylidene fluoride) (PVDF) membrane, as a secondary platform for vacuum-filtrated Au-TiO₂ nanocomposites, with enhanced photocatalytic activity. The degradation efficiency of Au-TiO₂/pDA/PVDF membranes reached 92% when exposed to visible light for 120 min, and the degradation efficiency of Au-TiO₂/pDA/PVDF membranes increased by 26% compared to that of Au-TiO₂ powder and increased by 51% compared to that of TiO₂/pDA/PVDF nanocomposite membranes. The degradation efficiency remained about 90% after five cycle experiments, and the Au-TiO₂/pDA/PVDF nanocomposite membranes showed good stability, regeneration performance, and easy recycling. The pDA coating not only served as a bioadhesion interface to improve the bonding force between the catalyst and the membrane substrate but also acted as a photosensitizer to broaden the wavelength response range of TiO₂, and the structure of Au-TiO₂/pDA/PVDF also improves the transfer rate of photogenerated electrons; the surface plasmon resonance effect of Au also played a positive role in improving the activity of the catalyst. Therefore, we believe that this study opens up a new strategy in preparing the bioinspired photocatalytic nanocomposite membrane for potential wastewater purification, catalysis, and as a membrane separation field.

Investigation of the removal mechanism of antibiotic ceftazidime by green algae and subsequent microbic impact assessment

The present study provides an integrated view of algal removal of the antibiotic ceftazidime and its basic parent structure 7-aminocephalosporanic acid (7-ACA), including contribution analysis, bacteriostatic and aquatic toxic assessment and metabolite verification. 92.70% and 96.07% of the two target compounds was removed after the algal treatment, respectively. The algal removal can be separated into three steps: a rapid adsorption, a slow cell wall-transmission and the final biodegradation. Additionally, while ceftazidime demonstrated an excellent inhibitory effect on Escherichia coli, there was no bacteriostasis introduced after the algal treatment, which could avoid favoring the harmful selective pressure. On the other hand, no significant aquatic impact of the two target compounds on rotifers was observed and it was not enhanced after the algal treatment. To better reveal the mechanism involved, metabolite analyses were performed. Δ-3 ceftazidime and trans-ceftazidime were regarded as the metabolites of ceftazidime and the metabolite of 7-ACA was regarded as a compound which shared the similar structure with 4-chlorocinnamic acid. Our study indicated that the green algae performed a satisfactory growth capacity and played a dominant role for the biodegradation of the target antibiotics, which achieved high removal efficiency and low environmental impact.

Improvement of Soil Ecosystem Multifunctionality by Dissipating Manure-Induced Antibiotics and Resistance Genes

The application of animal manure containing antibiotic residues to farmlands as an organic fertilizer causes a long-term potential threat to the ecological environment of farmland. This study analyzed the effects of abating typical antibiotics and resistance genes (ARGs) applied with pig manure on farmland soil as well as on soil ecosystem multifunctionality (EMF) and its influencing factor. The results showed that Lolium multiflorum exhibited significantly stronger abatement of typical antibiotics and ARGs when combined with biochar than when used alone (p < 0.05). The dissipation of antibiotics significantly enhanced the soil functions (respiratory, ammonification, and nitrification activities) (p < 0.05). A structural equation model was established to explore the effects of abating antibiotics and ARGs in different treatment systems on soil EMF. The treatment of plant roots with ryegrass alone and in combination with biochar exerted direct positive effects on the physical structure and EMF (p < 0.001). The improvement in soil physical structure directly promoted the abatement of antibiotics and ARGs (p < 0.01). Soil pH and trace elements exerted weaker effects on antibiotics and ARGs after the application of biochar. Plant roots were the most important factor in promoting the EMF of soil containing antibiotics and ARGs.

Ecotoxicity of veterinary enrofloxacin and ciprofloxacin antibiotics on anuran amphibian larvae

The ecological risks posed by two β-diketone antibiotics (DKAs, enrofloxacin, ENR and ciprofloxacin, CPX), characterized by their long persistence in aqueous environments and known deleterious effect on model organisms such as zebrafish were analysed using Rhinella arenarum larvae. Sublethal tests were conducted using environmentally relevant concentrations of both ENR and CPX (1-1000μgL^-1) under standard laboratory conditions for 96h. Biological endpoints and biomarkers evaluated were body size, shape, development and growth rates, and antioxidant enzymes (glutathione-S-transferase, GST; Catalase, CAT). Risk assessment was analysed based on ration quotients (RQ). The size and shape measurements of the larvae exposed to concentrations greater than 10μgL^-1 of CPX were lower compared to controls (Dunnett post hoc p<0.05) and presented signs of emaciation. Concentrations of 1000μgL^-1of CPX induced GST activity, in contrast with inhibited GST and CAT of larvae exposed to ENR. Risk assessments indicated that concentrations greater than or equal to10μgL^-1 of CPX and ENR are ecotoxic for development, growth, detoxifying, and oxidative stress enzymes. It is suggested that additional risk assessments may provide evidence of bioaccumulation of CPX and ENR in tissues or organs of amphibian larvae by mesocosm sediment test conditions. Finally, intestinal microbiome studies should be considered to establish the mechanisms of action of both antibiotics.

Uptake and translocation of sulfamethazine by alfalfa grown under hydroponic conditions

Antibiotics are routinely used in intensive animal agriculture operations collectively known as Concentrated Animal Feed Operations (CAFO) which include dairy, poultry and swine farms. Wastewater generated by CAFOs often contains low levels of antibiotics and is typically managed in an anaerobic lagoon. The objective of this research is to investigate the uptake and fate of aqueous sulfamethazine (SMN) antibiotic by alfalfa (Medicago sativa) grass grown under hydroponic conditions. Uptake studies were conducted using hydroponically grown alfalfa in a commercially available nutrient solution supplemented with 10mg/L of SMN antibiotic. Analysis of alfalfa sap, root zone, middle one-third, and top portion of the foliage showed varying uptake rate and translocation of SMN. The highest average amount of SMN (8.58μg/kg) was detected in the root zone, followed by the top portion (1.89μg/kg), middle one-third (1.30μg/kg), and sap (0.38μg/kg) samples, indicating a clear distribution of SMN within the sampled regions. The ultraviolet (UV) spectra of parent SMN and translocated SMN identified in different parts of the plant present the possibility of metabolization during the uptake process. Uptake of SMN using alfalfa grown under hydroponic conditions has potential as a promising remediation technology for removal of similar antibiotics from wastewater lagoons.