Fate of pharmaceuticals and antibiotic resistance genes in a full-scale on-farm livestock waste treatment plant

Current scenario of emerging pollutants in farmlands and water reservoirs: Prospects and challenges

Globally, roughly more than 400 million metric tons of plastics are produced annually. Similarly, the pharmaceuticals business is rising exponentially yearly, 5.8 %. It is expected to increase from USD 714 billion to USD 1454 billion by 2029. Beyond their intended uses, these substances are released into the environment as contaminants due to improper usage and management practices. Therefore, pharmaceuticals and microplastics (MPs) are classified as emerging pollutants (EPs), and their existence in agricultural ecosystems adversely affects soil and environmental health, ultimately impacting both ecological and human well-being. Pharmaceuticals and MP-loaded organic amendments (especially manure) are a primary cause of emerging soil pollutants. The increasing application of treated wastewater or biosolids as irrigation water or soil conditioners, mainly when derived from untreated sewage sludge, can introduce pharmaceuticals and MPs into the farmlands, merging these pollutants within the soil medium. The co-occurrence of MPs and pharmaceuticals leads to prolonged environmental presence and gradual bioaccumulation in organisms over time, contributing to persistent contamination and long-lasting effects on ecosystems. Moreover, these EPs have the potential to alter the composition of soil biogeochemistry and disrupt overall soil health and productivity. Numerous methods have been developed to address this emerging issue, including electrochemical degradation, advanced oxidation processes, photocatalytic degradation, biosurfactants, micro- and nano-bubble systems, ultrasonic cavitation, nanotechnology, constructed wetlands, and many hybrid approaches. This review explores the extent of EPs, their interactions, and management strategies in EPs-contaminated environments.

Biotransformation of chloramphenicol by enriched bacterial consortia and the newly isolated bacterial strain Bordetella sp. C3: Detoxifying biotransformation pathway and its potential application in agriculture

Limited sources of consortia/pure cultures that degrade chloramphenicol (CAP) and the incomplete biodegradation profiles of CAP hinder the remediation of CAP pollution. In this study, two CAP-degrading consortia (designated as CM and PM) were obtained after long-term acclimation, and Alcaligenaceae and Enterobacteriaceae enriched in CM and PM, respectively. Notably, Bordetella sp. C3, a new isolate belonging to the family Alcaligenaceae, was isolated from CM and capable of degrading 85.7 % 10 mg/L CAP at 30 ℃ and pH 7 in 10 d. The biotransformation of CAP by Bordetella sp. C3 was proposed as a detoxification process, including a novel initial degradation pathway: dechlorination of CAP into AP. Strain C3 can also function as a plant growth-promoting bacterium that solubilizes inorganic phosphate and produces siderophores and indole-3-acetic acid (IAA). This study expands our knowledge of the migration and transformation pathways of CAP and microbial community profiles during acclimatization.

Valorizing meat processing industry brines to produce added-value organic acids

During the production of certain meat processed products, such as cured ham and cold meat, large amounts of wastewater with high organic matter and salt content are generated. In contrast with the conventional management processes, which involves high energy consumption, this study proposes the valorisation of such meat brines through anaerobic fermentation to produce added-value organic acids. Several brines coming from different meat processing processes were tested to evaluate their acidification potential as well as to establish the main operation parameters in the fermenter: pH and the substrate-to-inoculum ratio. The brine with the best acidification results in both experiments was selected to be fed into a fed-batch fermenter at pH close to neutrality (6.5-7.3) and with an HRT of 6 d. With such conditions, a 27% of acidification in average was observed under an electrical conductivity up to 155 mS cm-1. Acetic and propionic acid were the most produced volatile fatty acids (VFAs) (39% and 22.0%, respectively), being the rest (up to 40%) ≥ C4 (including butyric, valeric and their isomeric forms). Finally, a selective separation between the salt and the VFAs were achieved working at low current density (<100 A m-2) in an electrodialysis system (80% of recovery in the diluate). The technological approach proposed in this study can be considered as a starting point to valorize high-salinity industrial wastewater, aligning with the circular economy model principles.

Fate of intracellular and extracellular antibiotic resistance genes in sewage sludge by full-scale anaerobic digestion

Storage tank (ST) is a promising strategy for solid-liquid separation following anaerobic digestion (AD). However, little is known regarding the effects of ST on antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), and microbial communities. Therefore, this study first investigated eight typical ARGs (sul1, sul2, tetW, tetA, tetO, tetX, ermF, and ermB) and three MGEs (int1, int2, and tnpA) during full-scale AD of sludge and the liquid and biosolids phases of ST. Following that, intracellular ARGs (iARGs), extracellular polymeric substances (EPS)-associated ARGs, and cell-free ARGs removal were quantified in AD process, which is largely unknown for full-scale AD of sludge. The qPCR results showed that both AD and ST significantly removed ARGs, with ST biosolids showing the highest removal efficiency for the total measured relative (82.27 ± 2.09 %) and absolute (92.38 ± 0.89 %) abundance of ARGs compared to the raw sludge. Proteobacteria, Bacteroidota, Firmicutes and Campilobacterota were the main potential ARGs hosts in the sludge. Moreover, the results of different ARGs fractions showed that the total relative and absolute abundance of iARGs decreased by 90.12 ± 0.83 % and 79.89 ± 1.41 %, respectively, following AD. The same trend was observed for the abundance of EPS-associated ARGs, while those of cell-free ARGs increased after AD. These results underscore the risk of extracellular ARGs and provided new insights on extracellular ARGs dissemination evaluation.

Selective electrodialysis for nutrient recovery and pharmaceutical removal from liquid digestate: Pilot-scale investigation and potential fertilizer production

The present research employs a pilot-scale selective electrodialysis system to treat liquid digestate, fractionating nutrient ions and exploring fertilizer creation via ammonia stripping and phosphorus precipitation, while studying pharmaceutical transport behavior and examining membrane fouling. The influence of diverse potentials was studied in simulated and real digestate, with 30 V application proven more efficient overall. Applying consecutive runs resulted in products that were 7.9, 7.4, 1.7, 5.3, and 6 times more concentrated compared to the feed solution for NH4+, K+, PO43-, Ca2+, and Mg2+, respectively. Pharmaceuticals analysis showed that ciprofloxacin was completely retained in the liquid digestate, while ibuprofen was detected in the anionic product. Diclofenac was initially present in the digestate but was undetectable in the final products, suggesting it adhered to the membrane. Membranes showed inorganic and organic fouling. The monovalent cation exchange membrane had severe salt scaling, showing calcium and magnesium deposits, and fewer functional groups.

Fate of micropollutants in struvite production from swine wastewater with sacrificial magnesium anode

Struvite recovery shows significant potential for simultaneously recovering nitrogen (N) and phosphorus (P) from swine wastewater but is challenged by the occurrence and transformation of antibiotic residuals. Electrochemically mediated struvite precipitation with sacrificial magnesium anode (EMSP-Mg) is promising due to its automation and chemical-free merits. However, the fate of antibiotics remains underexplored. We investigated the behavior of sulfadiazine (SD), an antibiotic frequently detected but less studied than others within the EMSP-Mg system. Significantly less SD (≤ 5%) was co-precipitated with recovered struvite in EMSP-Mg than conventional chemical struvite precipitation (CSP) processes (15.0 to 50.0%). The reduced SD accumulation in struvite recovered via EMSP was associated with increased pH and electric potential differences, which likely enhanced the electrostatic repulsion between SD and struvite. In contrast, the typical strategies used in enhancing P removal in the EMSP-Mg system, including increasing the Mg/P ratio or the Mg-release rates, have shown negligible effects on SD adsorption. Furthermore, typical coexisting ions (Ca2+, Cl-, and HCO3-) inhibited SD adsorption onto recovered products. These results provide new insights into the interactions between antibiotics and struvite within the EMSP-Mg system, enhancing our understanding of antibiotic migration pathways and aiding the development of novel EMSP processes for cleaner struvite recovery.

The fate of antibiotics and antibiotic resistance genes in Large-Scale chicken farm Environments: Preliminary view of the performance of National veterinary Antimicrobial use reduction Action in Guangdong, China

In 2018, China implemented the Veterinary Antimicrobial Use Reduction Action to curb the rapid development of antibiotic resistance (AR). However, the AR-related pollutions in animal farms after the reduction policy has been poorly investigated. Here, we performed a comprehensive investigation combining UPLC-MS/MS, metagenomic, and bacterial genomic analyses in eight representative large-scale chicken farms in Guangdong, China. Our results showed that antibiotics and ARGs contaminations were more severe in broiler farms than in layer farms. Notably, diverse tet(X) variants were prevalent in the chicken farms. These tet(X)s was carried by diverse E. coli lineages and obviously correlated with ISCR2 and IS1B transposases. The resistomes in chicken farms was significantly correlated with microbial community, and multiple factor analyses indicated that the joint effect of antibiotics-microbial community-MGEs was the most dominant driver of ARGs. Host tracking identified a variety of ARG bacterial hosts and the co-occurrence of ARGs-MRGs-MGEs. Source tracking indicated that the inherent component represented the main feature of resistomes in different hosts, while ARG transfer between the chicken gut and farm environments were frequent. A multiperspective evaluation of AR risk revealed that the early effect of antibiotic reduction was exhibited by the mitigation of maximum level of risky ARGs, prevalence of environmental AR pathogens, and HGT potential of ARGs mediated by phage structures. Overall, our findings provide insights into the antibiotic and ARG profiles in large-scale chicken farms with different rearing strategies and demonstrate a preliminary view of the performance of antibiotic reduction actions in China.

Fate of florfenicol and linezolid resistance genes and their bacterial hosts during two waste treatment models in swine feedlots

Florfenicol resistance genes (FRGs) are widely present in livestock farms. The aim of this study was to evaluate the removal efficiencies of FRGs as well as the relationships between FRGs, mobile genetic elements (MGEs) and bacterial communities during the natural drying (ND) and anaerobic digestion (AD) processes of manure treatment in swine farms by combining bacterial isolation, quantitative PCR and metagenomic approaches. Solid manure showed a higher abundance of FRGs than fresh manure and was the main contamination source of fexA and fexB in ND farms, whilst biogas slurry displayed a lower abundance of FRGs than the wastewater in AD farms. Moreover, fresh manure and wastewater showed a high abundance of optrA, and wastewater was the main contamination source of cfr in both ND and AD farms. Both optrA/fexA-positive enterococci and cfr/fexA-positive staphylococci were mainly isolated along the farms' treatment processes. The cfr-positive staphylococci were highly prevalent in wastewater (57.14 % - 100 %) and may be associated with nasal-derived cfr-positive porcine staphylococci. An increased abundance of Enterococcus, Jeotgalibaca and Vagococcus in the bacterial community structures may account for the high optrA abundance in wastewater and Jeotgalibaca may be another potential host of optrA. Furthermore, the abundance of FRG-related MGEs increased by 22.63 % after the ND process and decreased by 66.96 % in AD farms. A significant correlation was observed between cfr and ISEnfa4, whereas no significance was found between optrA and IS1216E, although IS1216E is the predominant insertion sequence involved in the transfer of optrA. In conclusion, manure and wastewater represented independent pollution sources of FRGs in swine farms. Associated MGEs might play a key role in the transfer and persistence of FRGs. The AD process was more efficient in the removal of FRGs than the ND method, nevertheless a longer storage of slurry may be required for a complete removal.

Distinctive effects of graphene oxide and reduced graphene oxide on methane production kinetics and pharmaceuticals removal in anaerobic reactors

Graphene oxide (GO) addition to anaerobic digestion has been suggested to enhance direct electron transfer. The impact of GO (0.075 g GO g-1 VS) and biologically and hydrothermally reduced GO (bio-rGO and h-rGO, respectively) on the methane production kinetics and removal of 12 pharmaceuticals was assessed in Fed-batch reactors. A decrease of 15 % in methane production was observed in the tests with GO addition compared with the control and the h-rGO. However, bio-rGO and h-rGO substantially increased the methane production rate compared to the control tests (+40 %), in the third fed-batch test. Removal of pharmaceuticals was enhanced only during the bio-reduction of GO (1st fed-batch test), whereas once the GO was bio-reduced, it followed a similar trend in the control and h-rGO tests. The addition of GO can enhance the methane production rate and, therefore, reduce the anaerobic treatment time.

Treatment of anaerobically digested pig manure by applying membrane processes for nutrient recovery and antibiotics removal

A combination of membrane processes was applied to treat the digestate produced after the anaerobic treatment of pig manure in a biogas plant, aiming towards the recovery of nutrients and effective water treatment for potential reuse. Initially, coarse filtration (sieving and microfiltration) was used to remove particles larger than 1 µm, followed by ultrafiltration, to reduce the suspended solids concentrations below 1 g/L. Subsequently, selective electrodialysis is employed to recover the main nutrient ions, primarily ammonium and potassium. The ion-depleted digestate is then fed to a reverse osmosis unit, where clean water was recovered, yielding a by-product (concentrate) stream enriched in phosphates and organics content. The presence of antibiotics and the concentrations of heavy metals were monitored during all treatment stages to assess their behavior/removal in the various membrane processes. The results indicate that almost 51% of the digestate could be recovered as water free from ions and antibiotics, suitable for reuse in the biogas plant for process needs and irrigation purposes. The selective electrodialysis process can recover 51% of initial NH4+ content (corresponding to 96% of the electrodialysis feed), while the remainder largely ended up in the ultrafiltration concentrate. A similar behavior was observed for the case of K+, while approximately 68% of the phosphates content was retained by the coarse filtration process, with another 24% remaining in the ultrafiltration concentrate and the remaining 8% in the reverse osmosis concentrate. Most of the antibiotics and heavy metals were retained by the coarse and ultrafiltration steps, with smaller amounts detected in the reverse osmosis concentrate.

Presence of pharmaceutical contaminants of emerging concerns in two rivers of western Cuba and their relationship with the extracellular enzymatic activity of microbial communities

In recent years, the concern derived from the presence of emerging contaminants in the environment and the possible effects on the One Health trilogy has increased. This study determined the concentration of pharmaceutical contaminants of emerging concern and their relationship with the extracellular enzymatic activity of microbial communities from two rivers in western Cuba. Two sampling stations were analyzed; one in the Almendares River (urban) and the other in the San Juan River (rural), taking into account the pollution sources that arrive at these stations and previous physicochemical characterizations. Extracellular protease, acid phosphatase, alkaline phosphatase, lipase, and catalase activities in water and sediments were determined and correlated with contaminants of emerging concern determined by liquid chromatography with mass spectrometry. This study evidenced the presence of different pharmaceutical contaminants found in the categories of antihypertensives, stimulants, anti-inflammatories, and antibiotics in both rivers. Concentrations of contaminants of emerging concern were greater in the Almendares River compared to the San Juan River. In addition, through the canonical redundancy analysis, the influence of these contaminants on the extracellular enzymatic activities of microbial communities was documented, where in most cases they inhibit protease, phosphatase, and lipase activities and enhance catalase activity in response to oxidative stress. The present investigation constitutes the first report in Cuba of the presence of pharmaceutical contaminants of emerging concern and one of the few works that exist in the Latin American region.

Fate of fluoroquinolones in field soil environment after incorporation of poultry litter from a farm with enrofloxacin administration via drinking water

The practice of incorporating animal manure into soil is supported within the European Circular economy as a possible substitute for mineral fertilizers and will become crucial for the sustainability of agriculture. However, this practice may indirectly contribute to the dissemination of antibiotics, resistance bacteria, and resistance genes. In this study, medicated drinking water and poultry litter samples were obtained from a broiler-chick farm. The obtained poultry litter was incorporated into the soil at the experimental field site. The objectives of this research project were first to develop analytical methods able to quantify fluoroquinolones (FQs) in medicated drinking water, poultry litter, and soil samples by LC-MS; second to study the fate of these FQs in the soil environment after incorporation of poultry litter from flock medicated by enrofloxacin (ENR); and third to screen the occurrence of selected fluoroquinolone resistance encoding genes in poultry litter and soil samples (PCR analysis). FQs were quantified in the broiler farm's medicated drinking water (41.0 ± 0.3 mg∙L-1 of ENR) and poultry litter (up to 70 mg∙kg-1 of FQs). The persistence of FQs in the soil environment over 112 days was monitored and evaluated (ENR concentrations ranged from 36 μg∙kg-1 to 9 μg∙kg-1 after 100 days). The presence of resistance genes was confirmed in both poultry litter and soil samples, in agreement with the risk assessment for the selection of AMR in soil based on ENR concentrations. This work provides a new, comprehensive perspective on the entry and long-term fate of antimicrobials in the terrestrial environment and their consequences after the incorporation of poultry litter into agricultural fields.

Biodegradation strategies of veterinary medicines in the environment: Enzymatic degradation

One Health closely integrates healthy farming, human medicine, and environmental ecology. Due to the ecotoxicity and risk of transmission of drug resistance, veterinary medicines (VMs) are regarded as emerging environmental pollutants. To reduce or mitigate the environmental risk of VMs, developing friendly, safe, and effective removal technologies is an important means of environmental remediation for VMs. Many previous studies have proved that biodegradation has significant advantages in removing VMs, and biodegradation based on enzyme catalysis presents higher operability and specificity. This review focused on biodegradation strategies of environmental pollutants and reviewed the enzymatic degradation of VMs including antimicrobial drugs, insecticides, and disinfectants. We reviewed the sources and catalytic mechanisms of peroxidase, laccase, and organophosphorus hydrolases, and summarized the latest research status of immobilization methods and bioengineering techniques in improving the performance of degrading enzymes. The mechanism of enzymatic degradation for VMs was elucidated in the current research. Suggestions and prospects for researching and developing enzymatic degradation of VMs were also put forward. This review will offer new ideas for the biodegradation of VMs and have a guide significance for the risk mitigation and detoxification of VMs in the environment.

Pharmaceuticals, hazard and ecotoxicity in surface and wastewater in a tropical dairy production area in Latin America

Pharmaceuticals comprise a complex group of emerging pollutants. Despite the significant number of pharmaceuticals used in veterinary medicine, the input of these compounds into the environment due to livestock activities has been scarcely described. This work assays for the first time in Central America the occurrence of pharmaceuticals in farm wastewater in an area devoted to dairy production, and in the surrounding surface waters. Among 69 monitored pharmaceuticals, a total of eight compounds were detected in wastewater samples collected from seven dairy farms after three sampling campaigns. Six pharmaceuticals were considered either of high (albendazole, lovastatin and caffeine) or intermediate estimated hazard (ciprofloxacin, acetaminophen and ketoprofen) based on the HQ approach, while 26% of the samples were considered of high estimated hazard according to the cumulative ∑HQ approach. Similarly, when ecotoxicological tests were applied, all the samples showed some level of toxicity towards Daphnia magna, and most samples towards Vibrio fischeri and Lactuca sativa. Fourteen pharmaceuticals were detected in surface water samples collected in the surroundings of the dairy production farms, including rural and urban areas. Seven out of these compounds showed high estimated risk (risperidone, diphenhydramine, trimethoprim, fluoxetine, ofloxacin, caffeine and ibuprofen), while three (gemfibrozil, ciprofloxacin and cephalexin) exhibited intermediate estimated risk. In a similar worrisome way, 27% of these samples were estimated to pose high environmental risk according to the pharmaceutical content. Despite being nontoxic for D. magna or V. fischeri, frequent inhibition (>20%) of GI in L. sativa was determined in 34% of surface water samples; such findings raise concern on the apparent inceptive environmental pollution and risk within the area. According to the pharmaceutical content patterns in both kinds of studied matrices, no clear evidence of significant contamination in surface water due to livestock activities could be retrieved, suggesting a main role of urban influence.

Removal of contaminants of emerging concern from the supernatant of anaerobically digested sludge by O3 and O3/H2O2: Ozone requirements, effects of the matrix, and toxicity

Digestate is a rich source of nutrients that can be applied in agricultural fields as fertilizer or irrigation water. However, most of the research about application of digestate have focused on its agronomic properties and neglected the potential harm of the presence of contaminants of emerging concern (CECs). Aadvanced oxidation processes (AOPs) have proved to be effective for removing these compounds from drinking water, yet there are some constrains to treat wastewater and digestate mainly due to their complex matrix. In this study, the feasibility to remove different CECs from digestate using O3 and O3/H2O2 was assessed, and the general effect of the matrix in the oxidation was explained. While the lab-scale ozonation provided an ozone dose of 1.49 mg O3/mg DOC in 5 h treatment, almost all the compounds were removed at a lower ozone dose of maximum 0.48 mg O3/mg DOC; only ibuprofen required a higher dose of 1.1 mg O3/mg DOC to be oxidized. The digestate matrix slowed down the kinetic ozonation rate to approximately 1% compared to the removal rate in demineralized water. The combined treatment (O3/H2O2) showed the additional contribution of H2O2 by decreasing the ozone demand by 59-75% for all the compounds. The acute toxicity of the digestate, measured by the inhibition of Vibrio fisheries luminescence, decreased by 18.1% during 5 h ozonation, and by 34% during 5 h O3/H2O2 treatment. Despite the high ozone consumption, the ozone dose (mg O3/mg DOC) required to remove all CECs from digestate supernatant was in the range or lower than what has been reported for other (waste-)water matrix, implying that ozonation can be considered as a post-AD treatment to produce cleaner stream for agricultural purposes.

Impact of graphene oxide addition on pharmaceuticals removal in anaerobic membrane bioreactor

The addition of conductive materials to the anaerobic digestion bioreactor was suggested to enhance microbial activity. In the present work, an anaerobic membrane bioreactor treating municipal wastewater was operated for 385 days. The impact of different graphene oxide concentrations on the removal target pharmaceuticals and microbial community dynamics was investigated. The addition of graphene oxide did not impact the reactor stability, whereas the removals of antibiotics (e.g., trimethoprim and metronidazole) were enhanced. A shift in the microbial community was detected after the addition of 50-900 mg L^-1 of graphene oxide, with the proliferation hydrogenotrophic methanogens. The proliferation of syntrophic microorganisms may indicate interactions via direct interspecific electron transfer. The obtained results suggest that the addition of graphene oxide at low mg L^-1 concentrations to an anaerobic membrane bioreactor may be considered to improve the removal of antibiotics from municipal wastewater.

Porous biochar derived from walnut shell as an efficient adsorbent for tetracycline removal

In this study, a high-performance porous adsorbent was prepared from biochar through a simple one-step alkali-activated pyrolysis treatment of walnut shells, and it was effective in removing tetracycline (TC). The specific surface area (SSA) of potassium hydroxide-pretreated walnut shell-derived biochar pyrolyzed at 900°C (KWS900) increased remarkably compared to that of the pristine walnut shell and reached 1713.87±37.05 m²·g^-1. The maximum adsorption capacity of KWS900 toward TC was 607.00±31.87 mg·g^-1. The pseudo-second-order kinetic and Langmuir isotherm models were well suited to describe the TC adsorption process onto KWS900. The KWS900 exhibited high stability and reusability for TC adsorption in the presence of co-existing anions or cations over a wide pH range of 1.0-11.0. Further investigations demonstrated that the proposed adsorption mechanism involved pore filling, hydrogen bonding, π-π stacking, and electrostatic interaction. These findings provide a valuable reference for developing biochar-based adsorbents for pollutant removal.

Graphene oxide addition to anaerobic digestion of waste activated sludge: Impact on methane production and removal of emerging contaminants

The effect of graphene oxide on the anaerobic digestion of waste activated sludge was investigated at two graphene oxide concentrations (0.025 and 0.075 g graphene oxide per g volatile solids) using biochemical methane potential tests. The occurrence of 36 pharmaceuticals was monitored in the solid and liquid phases before and after the anaerobic treatment. The addition of graphene oxide improved the removal of most pharmaceuticals detected, even those that are considered persistent to biological degradation, such as azithromycin, carbamazepine, and diclofenac. No significant differences were observed in the final specific methane production without graphene oxide and with the lowest graphene oxide concentration, yet the highest graphene oxide concentration partially inhibited methane production. The relative abundance of antibiotic resistance genes was not affected by the graphene oxide addition. Finally, significant changes in the microbial community including bacteria and archaea were detected with graphene oxide addition.

Digestate from Agricultural Biogas Plants as a Reservoir of Antimicrobials and Antibiotic Resistance Genes-Implications for the Environment

Antimicrobials and antibiotic resistance genes (ARGs) in substrates processed during anaerobic digestion in agricultural biogas plants (BPs) can reach the digestate (D), which is used as fertilizer. Antimicrobials and ARGs can be transferred to agricultural land, which increases their concentrations in the environment. The concentrations of 13 antibiotics in digestate samples from biogas plants (BPs) were investigated in this study. The abundance of ARGs encoding resistance to beta-lactams, tetracyclines, sulfonamides, fluoroquinolones, macrolide-lincosamide-streptogramin antibiotics, and the integrase genes were determined in the analyzed samples. The presence of cadmium, lead, nickel, chromium, zinc, and mercury was also examined. Antimicrobials were not eliminated during anaerobic digestion. Their concentrations differed in digestates obtained from different substrates and in liquid and solid fractions (ranging from 62.8 ng/g clarithromycin in the solid fraction of sewage sludge digestate to 1555.9 ng/L doxycycline in the liquid fraction of cattle manure digestate). Digestates obtained from plant-based substrates were characterized by high concentrations of ARGs (ranging from 5.73 × 102 copies/gDcfxA to 2.98 × 109 copies/gDsul1). The samples also contained mercury (0.5 mg/kg dry mass (dm)) and zinc (830 mg/kg dm). The results confirmed that digestate is a reservoir of ARGs (5.73 × 102 to 8.89 × 1010 copies/gD) and heavy metals (HMs). In addition, high concentrations of integrase genes (105 to 107 copies/gD) in the samples indicate that mobile genetic elements may be involved in the spread of antibiotic resistance. The study suggested that the risk of soil contamination with antibiotics, HMs, and ARGs is high in farms where digestate is used as fertilizer.

Antibiotics, antibiotic resistance and associated risk in natural springs from an agroecosystem environment

This study investigates the occurrence, transport, and risks associated to antibiotic residues, antibiotic resistance genes (ARGs) and antibiotic resistant Escherichia coli (AR-E. coli) in eleven natural springs in an agroecosystem environment with intense livestock production, where groundwater nitrate concentration usually sets above 50 mg L^-1. Out of 23 multiple-class antibiotics monitored, tetracycline and sulfonamide residues were the most ubiquitous, and they were detected at concentrations ranging from ng L^-1 to μg L^-1. Five ARGs were monitored, conferring resistance to the antibiotic classes of major use in livestock production. Thus, genes conferring resistance to sulfonamides (sul1 and sul2) and tetracyclines (tetW) as well as a gene proxy for anthropogenic pollution (intI1) were present in most springs. sul1 was the most abundant, with absolute concentrations ranging from 4 × 10² to 5.6 × 10⁶ gene copies L^-1 water. AR-E. coli showing resistance to sulfonamides and tetracyclines was also detected, with a prevalence up to approximately 40 % in some sites but with poor correlations with the concentration of antibiotic residues and ARGs. The occurrence of antibiotics, ARGs and AR-E. coli was characterized by large seasonal variations which were mostly associated to both hydrological factors and reactive transport processes. Finally, a risk assessment approach pointed out towards low risk for both the groundwater environment and human health, when spring water is used for direct human consumption, associated with the occurrence of antibiotics, ARGs and AR-E. coli. However, long-term effects cannot be neglected, and proper actions must be taken to preserve groundwater quality.

Cow manure simultaneously reshaped antibiotic and metal resistome in the earthworm gut tract by metagenomic analysis

Earthworm conversion is an eco-friendly biological process that converts livestock waste into a benign nutrient-rich organic fertilizer. However, little is known about the impacts of earthworm-converted livestock manure on the antibiotic resistome in the earthworm gut microbiota. Herein, lab-scale vermicomposting was performed to comprehensively evaluate the shift of antibiotic resistance genes (ARGs) in the earthworm gut-feeding on cow manure (CM)-by metagenomic analysis. The effects of copper (Cu) as a food addictive were also evaluated. CM substantially enriched the antibiotic resistome in the foregut and midgut, while it decreased in the hindgut. A similar trend was observed for metal resistance genes (MRGs). Notably, Cu in the CM had little effect on composition of ARGs and MRGs in earthworm gut. The earthworm gut microbiome altered by CM was responsible for the shift of ARGs and MRGs. In wormcast, Cu (100 and 300 mg/kg) significantly increased the abundance of ARGs and MRGs. Our study provides valuable insight into the response of ARGs and MRGs to CM in earthworm gut, and underscores the need for the judicious use of heavy metals as feed additives in livestock and poultry farming.

Insights into the impact of manure on the environmental antibiotic residues and resistance pool

The intensive use of antibiotics in the veterinary sector, linked to the application of manure-derived amendments in agriculture, translates into increased environmental levels of chemical residues, AR bacteria (ARB) and antibiotic resistance genes (ARG). The aim of this review was to evaluate the current evidence regarding the impact of animal farming and manure application on the antibiotic resistance pool in the environment. Several studies reported correlations between the prevalence of clinically relevant ARB and the amount and classes of antibiotics used in animal farming (high resistance rates being reported for medically important antibiotics such as penicillins, tetracyclines, sulfonamides and fluoroquinolones). However, the results are difficult to compare, due to the diversity of the used antimicrobials quantification techniques and to the different amounts and types of antibiotics, exhibiting various degradation times, given in animal feed in different countries. The soils fertilized with manure-derived products harbor a higher and chronic abundance of ARB, multiple ARG and an enriched associated mobilome, which is also sometimes seen in the crops grown on the amended soils. Different manure processing techniques have various efficiencies in the removal of antibiotic residues, ARB and ARGs, but there is only a small amount of data from commercial farms. The efficiency of sludge anaerobic digestion appears to be dependent on the microbial communities composition, the ARB/ARG and operating temperature (mesophilic vs. thermophilic conditions). Composting seems to reduce or eliminate most of antibiotics residues, enteric bacteria, ARB and different representative ARG in manure more rapidly and effectively than lagoon storage. Our review highlights that despite the body of research accumulated in the last years, there are still important knowledge gaps regarding the contribution of manure to the AMR emergence, accumulation, spread and risk of human exposure in countries with high clinical resistance rates. Land microbiome before and after manure application, efficiency of different manure treatment techniques in decreasing the AMR levels in the natural environments and along the food chain must be investigated in depth, covering different geographical regions and countries and using harmonized methodologies. The support of stakeholders is required for the development of specific best practices for prudent – cautious use of antibiotics on farm animals. The use of human reserve antibiotics in veterinary medicine and of unprescribed animal antimicrobials should be stopped and the use of antibiotics on farms must be limited. This integrated approach is needed to determine the optimal conditions for the removal of antibiotic residues, ARB and ARG, to formulate specific recommendations for livestock manure treatment, storage and handling procedures and to translate them into practical on-farm management decisions, to ultimately prevent exposure of human population.

Application of Vibrating Reverse Osmosis Technology for Nutrient Recovery from Pig Slurry in a Circular Economy Model

The rapid growth of the livestock sector in some areas of Europe has caused an imbalance between the generation of livestock manure and the availability of agricultural soil for its direct application as a fertilizer. Since the transport of pig slurry to other areas with nutrient-deficient soils is costly from an economic point of view due to its high water content, the application of new technologies for the concentration of this waste is considered key for reducing management costs. Consequently, the main objective of this study was to demonstrate the potential of vibratory shear enhanced processing (VSEP) operated with reverse osmosis membranes to recover nutrients from the liquid fractions of pig slurry (LF-pig slurry) and digestate (LF-digestate) and obtain concentrated fertilizing products. Use of the VSEP unit permitted reductions in the water contents of the LF-pig slurry and LF-digestate, around 77% and 67%, respectively. Both VSEP concentrates were characterized by their significant nutrient contents and showed a nitrogen fertilizer replacement value similar to that of mineral fertilizer as demonstrated in a barley crop pot-test, although the salinity of the digestate concentrate was identified as a key limitation, negatively impacting the agronomic yield of the test crop.

Current status and future perspective of antimicrobial-resistant bacteria and resistance genes in animal-breeding environments

The emergence and spread of antimicrobial-resistant bacteria (ARB) and antimicrobial resistance genes (ARGs) are a global public health concern. ARB are transmitted directly or indirectly from animals to humans. The importance of environmental transmission of ARB and ARGs has recently been demonstrated, given the relationships between compost, livestock wastewater, insects, and wildlife. In addition, companion animals and their surrounding environments (veterinary hospitals and homes with companion animals) should be considered owing to their close relationship with humans. This review discusses the current status and future perspectives of ARB and ARGs in animal-breeding environments.

Removal of Diverse and Abundant ARGs by MF-NF Process from Pig Manure and Digestate

Antimicrobial resistances are emerging as one main threat to worldwide human health and are expected to kill 10 million people by 2050. Intensive livestock husbandry, along with biogas digestate, are considered as one of the biggest ARG reservoirs. Despite major concerns, little information is available on the diversity and abundance of various ARGs in small to large scale pig farms and biogas digestate slurry in Germany, followed by their consequent removal using microfiltration (MF)-nanofiltration (NF) process. Here, we report the identification and quantification of 189 ARGs in raw manure and digestate samples, out of which 66 ARGs were shared among manures and 53 ARGs were shared among both manure and digestate samples. The highest reported total ARG copy numbers in a single manure sampling site was 1.15 × 10⁸ copies/100 µL. In addition, we found the absolute concentrations of 37 ARGs were above 10⁵ copies/100 μL. Filtration results showed that the highly concentrated ARGs (except aminoglycoside resistance ARGs) in feed presented high log retention value (LRV) from 3 to as high as 5 after the MF-NF process. Additionally, LRV below 2 was noticed where the initial absolute ARG concentrations were ≤10³ copies/100 μL. Therefore, ARG removal was found to be directly proportional to its initial concentration in the raw manure and in digestate samples. Consequently, some ARGs (tetH, strB) can still be found within the permeate of NF with up to 10⁴ copies/100 μL.

Occurrence of veterinary drugs and resistance genes during anaerobic digestion of poultry and cattle manures

In the present paper, the mesophilic (35 °C) and thermophilic (55 °C) biomethanization of poultry and cattle manures were investigated using biochemical methane potential (BMP) tests. Specific methane production (SMP), 24 pharmaceutical compounds (PhACs), and five antibiotic resistance genes (ARGs) (bla_KPC, ermB, qnrS, sul1 and tetW) together with the microbial community were analyzed. Mesophilic BMP tests resulted in the highest SMP when poultry manure was used (285.5 mL CH₄/g VSS with poultry vs 239.6 mL CH₄/g VSS with cattle manure) while thermophilic temperatures led to the highest SMP with cattle manure (231.2 mL CH₄/g VSS with poultry vs 238.0 mL CH₄/g VSS with cattle manure). Higher removals of veterinary pharmaceuticals were detected at 55 °C with both manures indicating that thermophilic digestion is better suited for the removal of these compounds. Tylosin, tilmicosin, chlortetracycline, and sulfamethoxazole presented removals higher than 50%, being the first two completely removed under mesophilic and thermophilic conditions. When comparing the relative abundance of ARGs at the end of each treatment, the most significant removal was found for qnrS which was not detected after the anaerobic treatment. The remaining ARGs did not suffer significant changes. Finally, microbial composition analysis showed that temperature affected the final microbial population more than the microorganisms present in the substrate or inoculum.

Morphological crystal adsorbing tetracyclines and its interaction with magnesium ion in the process of struvite crystallization by using synthetic wastewater

Struvite (MgNH₄PO₄·6H₂O) crystallization is a promising method of phosphorus recovery from wastewater. As for digestive livestock wastewater, the extensive residues of antibiotics could induce struvite recovery to spread antibiotic resistance and thereafter pose ecological risks to the environment. In this study, struvite crystals with different morphologies were produced from synthetic swine wastewater, and tetracyclines (TCs) adsorbing capacities were investigated. The important factors, including the existence of Mg²⁺ ions and initial TCs concentration, were examined. The predominant adsorption between TCs and struvite crystals was electrostatic interaction, with the maximum capacity at doxycycline (DXC) 876.5 μg/Kg, oxytetracycline (OTC) 1946.7 μg/Kg and tetracycline (TC) 2376.2 μg/Kg, respectively. Well-faceted struvite crystallites possessed high adsorption capacities than those of dendritic crystallite, due to higher Mg intensities on the crystallite surface. The increment of phosphorus concentration could trigger the transformation of struvite morphology from needle to dendritic shapes with X-shape as an intermediate stage, which would reduce Mg density in specific crystallite facets and therefore limit TCs adsorption onto struvite crystals. The existence of Mg²⁺ ion would inhibit TCs deprotonation and thereafter improve TCs adsorption onto struvite crystals. Further investigation revealed that continuously elevating initial TCs concentration would promote the formation of 1:2 transferring to 1:1 TCs-Mg chelates, which would result in a fluctuation following a drastic augment of TCs adsorption capacity.

Pharmaceutical Pollution in Aquatic Environments: A Concise Review of Environmental Impacts and Bioremediation Systems

The presence of emerging contaminants in the environment, such as pharmaceuticals, is a growing global concern. The excessive use of medication globally, together with the recalcitrance of pharmaceuticals in traditional wastewater treatment systems, has caused these compounds to present a severe environmental problem. In recent years, the increase in their availability, access and use of drugs has caused concentrations in water bodies to rise substantially. Considered as emerging contaminants, pharmaceuticals represent a challenge in the field of environmental remediation; therefore, alternative add-on systems for traditional wastewater treatment plants are continuously being developed to mitigate their impact and reduce their effects on the environment and human health. In this review, we describe the current status and impact of pharmaceutical compounds as emerging contaminants, focusing on their presence in water bodies, and analyzing the development of bioremediation systems, especially mycoremediation, for the removal of these pharmaceutical compounds with a special focus on fungal technologies.

Anaerobic treatment of swine manure under mesophilic and thermophilic temperatures: Fate of veterinary drugs and resistance genes

The effect of anaerobic treatment of swine manure at 35 °C (mesophilic) and 55 °C (thermophilic) on methane production, microbial community and contaminants of emerging concern was investigated. Pasteurization pretreatment and post treatment was also investigated in combination with anaerobic treatment at 35 °C. Specific methane production (SMP), 26 pharmaceutical compounds (PhACs) and five antibiotic resistance genes (ARGs) (qnrS, tetW, ermB, sul1 and bla_TEM) were evaluated. Mesophilic treatment resulted in the highest SMP regardless of whether pasteurization was applied. Marbofloxacin was the most abundant antibiotic in swine manure. In general, all groups of PhACs showed higher removals under thermophilic temperatures as compared to mesophilic. In general, pasteurization pretreatment followed by mesophilic anaerobic digestion provided the highest removals of ARGs. Finally, the genera Streptococcus, Clostridium and Pseudomonas which contain pathogenic species, were present in the swine manure. Streptococcus, which was the most abundant, was decreased during all the treatments, while the others only decreased under certain treatments.

Response behavior of antibiotic resistance genes to zinc oxide nanoparticles in cattle manure thermophilic anaerobic digestion process: A metagenomic analysis

This work investigated the metagenomics-based behavior of antibiotic resistance genes (ARGs) during cattle manure anaerobic digestion with zinc oxide nanoparticles (ZnO NPs) that are commonly used as animal feed additives. The 6.6% decrease in total ARGs abundance while remained unchanged ARGs diversity with ZnO NPs (5 mg/g total solid), suggested ZnO NPs may mitigate ARGs risk by abundance. Also, ZnO NPs affected ARGs with mechanisms specifically of antibiotic inactivation and antibiotic target change, and declined potential hosts' abundance (bacterial genus Ruminiclostridium, Riminococcus, and Paenibacillus) which mainly contributed to the decreased ARGs' abundance. Besides, microbial chemotaxis decreased by 17% with ZnO NPs compared to that without nanoparticles indicated a depression on potential hosts, who could develop the mechanism to adapt to altered digestion conditions, which probably inhibited the ARGs' propagation. These findings are important to promote understanding of the potential ARGs risks in treatments of livestock wastes containing animal feed additives.

Enhanced treatment of organic matter in slaughter wastewater through live Bacillus velezensis strain using nano zinc oxide microsphere

Slaughter wastewater is an important and wide range of environmental issues, and even threaten human health through meat production. A high efficiency and stability microsphere-immobilized Bacillus velezensis strain was designed to remove organic matter and inhibit the growth of harmful bacteria in process of slaughter wastewater. Bacillus velezensis was immobilized on the surface of sodium alginate (SA)/Polyvinyl alcohol (PVA)/Nano Zinc Oxide (Nano-ZnO) microsphere with the adhesion to bio-carrier through direct physical adsorption. Results indicated that SA/PVA/ZnO and SA/ZnO microspheres could inhibit E.coli growth with adding 0.15 g/L nano-ZnO and not affect Bacillus velezensis strain, and the removal the chemical oxygen demand (COD) rates of SA/PVA/ZnO microsphere immobilized cells are 16.99%, followed by SA/ZnO (13.69%) and free bacteria (7.61%) from 50% concentration slaughter wastewater within 24 h at 37 °C, pH 7.0, and 120 rpm, a significant difference was found between the microsphere and control group. Moreover, when the processing time reaches 36 h, COD degradation of SA/PVA/ZnO microsphere is obviously higher than other groups (SA/PVA/ZnO:SA/ZnO:control vs 18.535 : 15.446: 10.812). Similar results were obtained from 30% concentration slaughter wastewater. Moreover, protein degradation assay was detected, and there are no significant difference (SA/PVA/ZnO:SA/ZnO:control vs 35.4 : 34.4: 36.0). The design of this strategy could greatly enhance the degradation efficiency, inhibit the growth of other bacteria and no effect on the activity of protease in slaughter wastewater. These findings suggested that the nano-ZnO hydrogel immobilization Bacillus velezensis system wastewater treatment is a valuable alternative method for the remediation of pollutants from slaughter wastewater with a novel and eco-friendly with low-cost investment as an advantage.

Groundwater antibiotic pollution and its relationship with dissolved organic matter: Identification and environmental implications

The occurrence of veterinary antibiotics and hydro-chemical parameters in eleven natural springs in a livestock production area is evaluated, jointly with the characterization of their DOM fingerprint by Orbitrap HRMS. Tetracycline and sulfonamide antibiotics were ubiquitous in all sites, and they were detected at low ng L^-1 concentrations, except for doxycycline, that was present at μg L^-1 in one location. DOM analysis revealed that most molecular formulas were CHO compounds (49 %-68 %), with a remarkable percentage containing nitrogen and sulphur (16 %-23 % and 11 %-24 %, respectively). Major DOM components were phenolic and highly unsaturated compounds (~90 %), typical for soil-derived organic matter, while approximately 11 % were unsaturated aliphatic, suggesting that springs may be susceptible to anthropogenic contamination sources. Comparing the DOM fingerprint among sites, the spring showing the most different profile was the one with surface water interaction and characterized by having lower CHO and higher CHOS formulas and aliphatic compounds. Correlations between antibiotics and DOM showed that tetracyclines positively correlate with unsaturated oxygen-rich substances, while sulfonamides relate with aliphatic and unsaturated oxygen-poor compounds. This indicates that the fate of different antibiotics will be controlled by the type of DOM present in groundwater.

Magnetic porous biochar as a renewable and highly effective adsorbent for the removal of tetracycline hydrochloride in water

In this study, discarded cigarette butts were used as a precursor for preparing magnetic porous biochar with a facile annealing method. The magnetic porous biochar was applied to remove tetracycline hydrochloride (TCH) from aqueous solution. It exhibited excellent adsorption capacity for TCH, which was much higher than various similar materials reported. At the same time, the adsorption kinetics and adsorption isotherms of TCH were well fitted to the pseudo-second-order models and Freundlich models, respectively. The thermodynamics experiments proved that the adsorption on magnetic porous biochar was an endothermic reaction. Furthermore, the adsorption mechanism was explored, and the outstanding adsorption ability was mainly dependent on the pore filling effect, electrostatic interaction, and π-π interaction. By using the magnetic porous biochar, the real water samples were treated and high removal efficiency to TCH was obtained. What's more, the excellent reusability endowed the magnetic porous biochar with great potential as adsorbents for practical application.

Assessing the occurrence of pharmaceuticals and antibiotic resistance genes during the anaerobic treatment of slaughterhouse wastewater at different temperatures

This study investigates the effect of psychrophilic, mesophilic and thermophilic temperatures on the anaerobic treatment of slaughterhouse wastewater, in terms of biogas production, occurrence of 30 pharmaceutical compounds of veterinary use, 4 antibiotic resistance genes (ARGs) which provide resistance to tetracyclines (tetW), fluoroquinolones (qnrS), macrolide-lincosamide-streptogramin (ermB) and sulfonamides (sul1) antibiotics, as well as class I integron-integrase gene (intI1), related to horizontal gene transfer. The highest methane yield was obtained at a mesophilic temperature (35 °C) (323 mL CH₄/g TCOD) followed by the yield obtained at thermophilic temperature (53 °C) (242 mL CH₄/g TCOD). Regarding pharmaceuticals, chlortetracycline, oxytetracycline, tilmicosin, and lincomycin were the most abundant in the slaughterhouse wastewater, being detected predominantly in the solid phase (with median concentrations >200 μg/kg dry weight). On the other hand, ciprofloxacin, ofloxacin, norfloxacin, lincomycin and ibuprofen were the most predominant in the anaerobic digestate regardless of the treatment temperature. Psychrophilic temperatures (21 °C) exhibited moderate to low pharmaceuticals removal, while a large fraction of them were removed at a thermophilic temperature reaching 70-90% removals for tetracycline, macrolides and one sulfonamide (sulfapyridine). The highest relative abundance of the quantified ARGs was found at 53 °C, suggesting that thermophilic temperatures normally associated with better removals of pathogens do not necessarily show better removals of antibiotic resistance genes.

A review targeting veterinary antibiotics removal from livestock manure management systems and future outlook

Veterinary antibiotics (VAs) contamination has been considered as a worldwide environmental and health concern in recent decades. This paper reviewed the variability of contents of VAs and their release from the animal breeding industry into the surrounding environment along with the performance of the manure treatment technologies. The data collected revealed that VAs were mostly excreted in animal feces and observed in manure, soil, water, and sediment. The findings illustrate the disparity of VAs in excretion rates, consumption, and their residues in the environment with relatively high distribution for tetracyclines, fluoroquinolones, and sulfonamides. Anaerobic digestion has a capacity to remove of 73% VAs while manure composting and constructed wetlands can remove 84.7%, and 90% VAs. Due to the profound effect of antibiotics on the environment, further research and intensive management strategies for livestock manure need to be designed to improve the removal efficiency and manure management technologies.

Antibacterial Residue Excretion via Urine as an Indicator for Therapeutical Treatment Choice and Farm Waste Treatment

Many of the infectious diseases that affect livestock have bacteria as etiological agents. Thus, therapy is based on antimicrobials that leave the animal's tissues mainly via urine, reaching the environment through slurry and waste water. Once there, antimicrobial residues may lead to antibacterial resistance as well as toxicity for plants, animals, or humans. Hence, the objective was to describe the rate of antimicrobial excretion in urine in order to select the most appropriate molecule while reducing harmful effects. Thus, 62 pigs were treated with sulfamethoxypyridazine, oxytetracycline, and enrofloxacin. Urine was collected through the withdrawal period and analysed via LC-MS/MS. Oxytetracycline had the slowest rate of degradation (a half-life time of 4.18 days) and the most extended elimination period in urine (over 2 months), followed by enrofloxacin (a half-life time of 1.48 days, total urine elimination in ca. 3 weeks) and sulfamethoxypyridazine (a half-life time of 0.49 days, total urine elimination in ca. 1 week). Bacterial sensitivity and recommendations for responsible use are limiting when selecting the treatment. Nevertheless, with similar effectiveness, sulfamethoxypyridazine would be the choice, as waste treatment would only need to be implemented for 1 week after treatment. Thus, more in-depth knowledge regarding antibacterial elimination would improve resource management, while protecting animals and consumers' health.

Role of anaerobic sludge digestion in handling antibiotic resistant bacteria and antibiotic resistance genes - A review

Currently, anaerobic sludge digestion (ASD) is considered not only for treating residual sewage sludge and energy recovery but also for the reduction of antibiotic resistance genes (ARGs). The current review highlights the reasons why antibiotic resistant bacteria (ARB) and ARGs exist in ASD and how ASD performs in the reduction of ARB and ARGs. ARGs and ARB have been detected in ASD with some reports indicating some of the ARGs can be completely removed during the ASD process, while other studies reported the enrichment of ARB and ARGs after ASD. This paper reviews the performance of ASD based on operational parameters as well as environmental chemistry. More studies are needed to improve the performance of ASD in reducing ARGs that are difficult to handle and also differentiate between extracellular (eARGs) and intracellular ARGs (iARGs) to achieve more accurate quantification of the ARGs.

Dispersion of Antibiotic Resistance Genes (ARGs) from stored swine manure biogas digestate to the atmosphere

Biogas digestate is a reservoir of antibiotic resistance genes (ARGs) and could pose a high health risk to both human and animals if the host microorganisms of ARGs become aerosolized. The purpose of this study was to investigate the diversity and relative abundance characteristics of aerosol-loaded ARGs from biogas digestate during storage, and to explore whether the change of ARGs in biogas digestate directly affect the dispersion of aerosol-loaded ARGs. This study reported for the first time that 28 of 42 ARG subtypes detected in the biogas digestate could be dispersed to the atmosphere via aerosol dispersion in a lab-scale dynamic emission vessels experiment. The relative abundance or diversity of ARGs in aerosols were different from that in biogas digestate, and no significant correlation were observed between the relative abundance of ARGs in biogas digestate and aerosols. The dominant ARGs were tetracycline resistance genes in biogas digestate and β-lactam resistance genes in aerosols. The process of biogas digestate storage reduced the total relative abundance of targeted ARGs in biogas digestate, decreased by 0.35 copies/16S rRNA after 30 days of storage, but increased the abundance of some ARG subtypes, including tetM, tetX, tetQ, tetS, ermF and sul2. High-concerned ARGs, including NDM-1, mcr-1 and vancomycin resistance genes (including vanA, vanB, vanRA and vanSA), were found in biogas digestate, and NDM-1 and vanB were also detected in aerosols. These results indicated a potential risk of ARGs dispersion during biogas digestate storage. Further research on the dispersion of ARGs from biogas digestate is required to elucidate the emission mechanism and develop mitigation measures.

Fate of antibiotics during membrane separation followed by physical-chemical treatment processes

Membrane separation technology has been widely utilised to obtain clean permeate and concentrated nutrients from biogas digested slurry. However, some antibiotics are frequently found in digested slurry. Antibiotic removal during the steps, including paper filtration (PF), hollow-fibre membrane ultrafiltration (HF), nanofiltration (NF) and reverse osmosis (RO), of combined membrane separation processing (CMP) remain poorly understood. Experiments were performed on a pilot-scale CMP plant to investigate antibiotic transport and rejection efficiencies in CMP products and analyse the antibiotic removal performances of additional treatments. Results showed average relative antibiotic rejection efficiencies of 50%, 83%, 28% and 14% for PF, HF, NF and RO during CMP, respectively. Each CMP product needed additional treatment for antibiotic removal. Antibiotic removal capacity followed the order of fine halloysite > P25 > activated charcoal > coarse halloysite. The average antibiotic removal rates for different CMP products ranged from 73.3% to 99.9%. But antibiotics can only be adsorbed by fine halloysite and must be degraded through other treatments, Thus, P25 has considerable practical importance for the removal of antibiotics, as antibiotics can be degraded during photocatalysis.

Direct Purification of Digestate Using Ultrafiltration Membranes: Influence of Pore Size on Filtration Behavior and Fouling Characteristics

Ultrafiltration (UF) can effectively remove large particles, suspended solids, and colloidal substances from anaerobic digestate. However, membrane fouling is a technical challenge in the purification of the digestate by UF. In this study, polyethersulfone (PES) membranes with four pore sizes (50.0, 20.0, 10.0 and 5.0 kDa) were employed to filter anaerobic digestate from swine manure. The effects of temperature, transmembrane pressure (TMP), and cross-flow velocity (CFV) on flux were investigated. The purification effects and fouling characteristics of the four membranes were analyzed. The results revealed that the increase of temperature and CFV can effectively promote UF separation efficiency, but as the TMP exceeded 3.0 bar, the flux increase rates of the four membranes were almost zero. The larger membrane pore size caused the faster flux increase with the increase in pressure. During the batch experiment, the 20.0 kDa membrane showed the lowest flux maintenance ability, while the 5.0 kDa showed the highest ability due to the smaller pore size. All four membranes can effectively remove tetracyclines residues. Elements C, O, and S were the major membrane foulant elements. The dominant bacteria orders of membrane fouling were Pseudomonadales, Xanthomonadales and Burkholderiales. Compared with tap water and citric acid, the membrane cleaning by NaOH and NaClO showed higher flux recovery rates. The 50.0 kDa membrane achieved the best cleaning effects under all cleaning methods.

Distribution of antibiotics in water, sediments and biofilm in an urban river (Córdoba, Argentina, LA)

In this study, we evaluated the distribution of up to forty-three antibiotics and 4 metabolites residues in different environmental compartments of an urban river receiving both diffuse and point sources of pollution. This is the first study to assess the fate of different antibiotic families in water, biofilms and sediments simultaneously under a real urban river scenario. Solid phase extraction, bead-beating disruption and pressurized liquid extraction were applied for sample preparation of water, biofilm and sediment respectively, followed by the quantification of target antibiotics by UPLC-ESI-MS/MS. Twelve antibiotics belonging to eight chemical families were detected in Suquía River samples (67% positive samples). Sites downstream the WWTP discharge were the most polluted ones. Concentrations of positive samples ranged 0.003-0.29 µg L^-1 in water (max. cephalexin), 2-652 µg kg^-1_d.w. in biofilm (max. ciprofloxacin) and 2-34 µg kg^-1_d.w. in sediment (max. ofloxacin). Fluoroquinolones, macrolides and trimethoprim were the most frequently detected antibiotics in the three compartments. However cephalexin was the prevalent antibiotic in water. Antibiotics exhibited preference for their accumulation from water into biofilms rather than in sediments (bioaccumulation factors > 1,000 L kg^-1_d.w. in biofilms, while pseudo-partition coefficients in sediments < 1,000 L kg^-1_d.w.). Downstream the WWTP there was an association of antibiotics levels in biofilms with ash-free dry weight, opposite to chlorophyll-a (indicative of heterotrophic communities). Cephalexin and clarithromycin in river water were found to pose high risk for the aquatic ecosystem, while ciprofloxacin presented high risk for development of antimicrobial resistance. This study contributes to the understanding of the fate and distribution of antibiotic pollution in urban rivers, reveals biofilm accumulation as an important environmental fate, and calls for attention to government authorities to manage identified highly risk antibiotics.

Changes and distributions of antibiotic resistance genes in liquid and solid fractions in mesophilic and thermophilic anaerobic digestion of dairy manure

This study mainly explored the changes and distributions of antibiotic resistance genes (ARGs) in liquid fraction (L_F) and solid fraction (S_F) in anaerobic digestion (AD) of dairy manure. After mesophilic and thermophilic AD, the copy numbers of ARGs in L_F decreased by 0.06-1.80 logs while those in S_F increased by 0.08-7.85 logs, suggesting the enrichment of ARGs in S_F. Statistical analysis elucidated that high total solids promoted the enrichment of ARGs in S_F. The increased abundances of genera such as Ruminofilibacter, Treponema and Sphaerochaeta in S_F were responsible for the enrichment of most ARGs. These insights demonstrated the digested solid had the potential risks to promote the spread of ARGs in the environment, and the digested solid of livestock manure should be post-treated before the application.

Occurrence of Antibiotics, Antibiotic Resistance Genes and Viral Genomes in Wastewater Effluents and Their Treatment by a Pilot Scale Nanofiltration Unit

Broad-spectrum fluoroquinolone antibiotics (ciprofloxacin and levofloxacin), carbapenem and fluoroquinolone resistance genes, as well as viral genomes, were detected in grab samples of wastewater effluents. Passive samplers, which are simpler and easier to use and provide information about the concentrations and combination of contaminants present in a certain fluid matrix over time, proved to be extremely promising devices to monitor the presence of the target antibiotics in wastewater effluents. Nanofiltration was tested with a pilot-scale unit installed at a domestic wastewater treatment facility, using a Desal 5DK membrane operated at a constant transmembrane pressure of 6 bar and 70% recovery rate. In a 24 h experimental assay, the variation of the membrane permeance was low (6.3%). High rejections of the target contaminants from the wastewater effluent were obtained by the pilot-scale treatment. Hence, nanofiltration using the Desal 5DK membrane is considered to be a promising treatment to cope with chemical and biological contaminants present in wastewater effluents.

Struvite crystallization induced the discrepant transports of antibiotics and antibiotic resistance genes in phosphorus recovery from swine wastewater

Struvite (MgNH₄PO₃·6H₂O) crystallization is one of important methods of phosphorus recovery from wastewater. As to livestock wastewater, the high-strength occurrence of antibiotics and antibiotic resistance genes might induce struvite recovery to spread antibiotic resistance to the environment. However, limited information has been reported on the simultaneous transport of antibiotics and ARGs in struvite recovery. In the present study, tetracyclines (TCs) and tetracyclines antibiotic resistance genes (ARGs) were selected as the targeted pollutants, and their discrepant residues in struvite recovery from swine wastewater were investigated. TCs and ARGs were obviously detected, with their contents of 4.88-79.5 mg/kg and 6.99 × 10⁷-2.14 × 10¹¹ copies/g, notably higher than those of TCs 0.550-1.94 mg/kg and ARGs 3.98 × 10⁴-5.66 × 10⁷ copies/g obtained from synthetic wastewater. The correlational relationship revealed that predominant factors affecting TCs and ARGs transports were different. Results from network analyses indicated that among the total edges, the negative correlations between TCs and ARGs predominately occupied 18.0%. The redundancy analysis revealed that mineral components in the recovered products, including struvite, K-struvite and amorphous calcium phosphate, coupling with organic contents, displayed insignificant roles on TCs residues, where heavy metals exerted positive and remarkable functions to boost TCs migration. Unexpectedly, mineral components and heavy metals did not displayed significant promotion on ARGs transport as a whole.

Effect of Pretreatment on Hydraulic Performance of the Integrated Membrane Process for Concentrating Nutrient in Biogas Digestate from Swine Manure

Nanofiltration (NF) or reverse osmosis (RO) process has been widely applied for concentrating nutrient in biogas digestate. However, efficient pretreatment is key to the sustainable operation of NF or RO. In this study, the combination of NF and RO for concentrating biogas digestate was compared using different pretreatments of hollow fiber ultrafiltration membrane (HFUFM) and ceramic membrane (CUFM). Pilot-scale batch tests were conducted (500 L). CUFM showed a higher membrane flux than HFUFM (100 ~ 180 L·(m²·h)⁻¹ vs. 17 ~ 35 L·(m²·h)⁻¹), but they showed little impact on the NF + RO process. Membrane fluxes of NF and RO were 20 ~ 48 L·(m²·h)⁻¹ and 16 ~ 40 L·(m²·h)⁻¹, respectively. In the RO permeates, the removal rates of total suspended solids (TSS), total solids (TS), chemical oxygen demand (COD), total nitrogen (TN), NH₄⁺-N, and Cl⁻ were above 91%. In the concentrates, TN and total potassium (TK) were concentrated by 1.60 and 2.00 folds in the NF stage, and by 2.10 and 2.30 folds in the RO stage. Further attention should be paid to the antibiotics risks in the concentrates before they are utilized as plant fertilizers.

A critical review on the occurrence of resistomes in the environment and their removal from wastewater using apposite treatment technologies: Limitations, successes and future improvement

Recent reports are pointing towards the potential increasing risks of resistomes in human host. With no permissible limit in sight, resistomes are continually multiplying at an alarming rate in the ecosystem, with a disturbing level in drinking water source. The morphology and chemical constituent of resistomes afford them to resist degradation, elude membrane and counter ionic charge, thereby, rendering both conventional and advanced water and wastewater treatment inefficient. Water and wastewater matrix may govern the propagation of individual resistomes sub-type, co-selection and specific interaction towards precise condition may have enhanced the current challenge. This review covers recent reports (2011-2019) on the occurrence of ARB/ARGs and ease of spread of resistance genes in the aquatic ecosystem. The contributions of water matrix to the spread and mitigation, treatment options, via bulk removal or capture, and intracellular and extracellular DNA lysis were discussed. A complete summary of recent occurrences of ARB/ARGs, fate after disinfection and optimum conditions of individual treatment technology or in tandem, including process limitations, with a brief assessment of removal or degradation mechanism were highlighted.

Pharmaceuticals removal in an on-farm pig slurry treatment plant based on solid-liquid separation and nitrification-denitrification systems

The fate and degradation of 28 multiple-class veterinary pharmaceuticals in an on-farm pig slurry treatment plant based on solid-liquid separation and a nitrification-denitrification (NDN) sequence batch reactor (SBR) were evaluated for the first time. The pharmaceuticals detected at the highest concentrations in raw pig slurries belonged to the group of tetracycline antibiotics. Fluoroquinolone, lincosamide and pleuromutilin antibiotics and other drugs such as flubendazole and flunixin were also frequently detected. After solid-liquid separation, target compounds were distributed in an average of 64% onto the liquid fraction. Pharmaceuticals distributed in this fraction were removed in an average of almost 50% after being treated in NDN-SBR. Lincomycin was the compound with the highest removal percentage, reaching 100% reduction, while tetracyclines and fluoroquinolones showed moderate removal percentages (50 and 40%, respectively). Regarding nitrogen removal, NDN-SBR reduced a 77% of the content of this nutrient in the liquid slurry fraction.

Increasing Prevalence of ESBL-Producing Multidrug Resistance Escherichia coli From Diseased Pets in Beijing, China From 2012 to 2017

We investigated antimicrobial resistance trends and characteristics of ESBL-producing Escherichia coli isolates from pets and whether this correlates with antibiotic usage in the clinic. Clinical samples containing E. coli from diseased cats and dogs were screened for antibiotic sensitivity and associated genotypic features. We identified 127 E. coli isolates from 1886 samples from dogs (n = 1565) and cats (n = 321) with the majority from urinary tract infections (n = 108, 85%). High rates of resistance were observed for β-lactams and fluoroquinolones and resistance to > 3 antibiotic classes (MDR) increased from 67% in 2012 to 75% in 2017 (P < 0.0001). This was especially true for strains resistant to 6-9 antibiotics that increased from 26.67 to 60.71%. Increased rates in β-lactam use for clinical treatment accompanied these increasing resistance rates. Accordingly, the most frequently encountered subtypes were bla _CTX-M (n = 44, 34.65%), bla _CTX-M-65 (n = 19) and bla _CTX-M-15 (n = 18) and qnrB (n = 119, 93.70%). The bla _CTX-M-isolates possessed 36 unique pulsed field electrophoretic types (PFGEs) and 28 different sequence types (STs) in ST405 (7, 15.9%), ST131 (3, 6.8%), ST73, ST101, ST372, and ST827 (2, 4.5% each) were the most prevalent. This data demonstrated a high level of diversity for the bla _CTX-M-positive E. coli isolates. Additionally, bla _NDM-5 was detected in three isolates (n = 3, 2.36%), comprised of two ST101 and one ST405 isolates, and mcr-1 was also observed in three colistin-resistant E. coli with three different STs (ST6316, ST405, and ST46). Our study demonstrates an increasing trend in MDR and ESBL-producing E. coli and this correlated with β-lactam antibiotic usage for treatment of these animals. This data indicates that there is significant risk for the spread of resistant bacteria from pets to humans and antibiotic use for pets should be more strictly regulated.