RESUMEN
Cyanobacterial blooms are a common and serious problem in global freshwater environments. However, the response mechanisms of various cyanobacterial genera to multiple nutrients and pollutants, as well as the factors driving their competitive dominance, remain unclear or controversial. The relative abundance and cell density of two dominant cyanobacterial genera (i.e., Cyanobium and Microcystis) in river ecosystems along a gradient of anthropogenic disturbance were predicted by random forest with post-interpretability based on physicochemical indices. Results showed that the optimized predictions all reached strong fitting with R2 > 0.75, and conventional water quality indices played a dominant role. One-dimensional and two-dimensional partial dependence plot (PDP) revealed that the responses of Cyanobium and Microcystis to nutrients and temperature were similar, but they showed differences in preferrable nutrient utilization and response to pollutants. Further prediction and PDP for the ratio of Cyanobium and Microcystis unveiled that their distinct responses to PAHs and SPAHs were crucial drivers for their competitive dominance over each other. This study presents a new way for analyzing the response of cyanobacterial genera to multiple environmental factors and their dominance relationships by interpretable machine learning, which is suitable for the identification and interpretation of high-dimensional nonlinear ecosystems with complex interactions.
Asunto(s)
Cianobacterias , Monitoreo del Ambiente , Aprendizaje Automático , Ríos , Cianobacterias/crecimiento & desarrollo , Ríos/microbiología , Monitoreo del Ambiente/métodos , Ecosistema , EutrofizaciónRESUMEN
The COVID-19 outbreak has raised concerns about the efficacy of the disinfection process followed in water treatment plants in preventing the spread of viruses. Ultraviolet (UV) and chlorine multi-barrier disinfection processes are commonly used in water treatment plants; however, their effects on virus inactivation are still unclear. In this study, the effects of different disinfection processes (i.e., UV, free chlorine, and their combination) on waterborne viruses were analyzed using bacteriophage surrogates (i.e., MS2 and PR772) as alternative indicators. The results showed that the inactivation rates of PR772 by either UV or free chlorine disinfection were higher than those of MS2. PR772 was approximately 1.5 times more sensitive to UV disinfection and 8.4 times more sensitive to chlorine disinfection than MS2. Sequential UV-chlorine disinfection had a synergistic effect on virus inactivation, which was enhanced by an increase in the UV dose. As compared with single free chlorine disinfection, UV irradiation at 40 mJ cm-2 enhanced MS2 and PR772 inactivation significantly with a 2.7-fold (MS2) and a 1.7-fold (PR772) increase in the inactivation rate constants on subsequent chlorination in phosphate buffered saline. The synergistic effect was also observed in real wastewater samples, in which the MS2 inactivation rate increased 1.4-fold on subsequent chlorination following UV irradiation at 40 mJ cm-2. The mechanism of the synergistic effect of sequential UV-chlorine disinfection was determined via sodium dodecyl sulfate-polyacrylamide gel electrophoresis, using MS2 as an indicator. The results showed that the synergistic effect was due to damage to MS2 surface proteins caused by previous UV disinfection, which enhanced the sensitivity of MS2 to chlorination. This study provides a feasible approach for the efficient inactivation of viruses in water supply and drainage.
Asunto(s)
Bacteriófagos , COVID-19 , Purificación del Agua , Humanos , Desinfección/métodos , Cloro/farmacología , Inactivación de Virus , Bacteriófagos/efectos de la radiación , Purificación del Agua/métodos , Rayos UltravioletaRESUMEN
Water quality can change along a river system due to differences in adjacent land use patterns and discharge sources. These variations can induce rapid responses of the aquatic microbial community, which may be an indicator of water quality characteristics. In the current study, we used a random forest model to predict water sample sources from three different river ecosystems along a gradient of anthropogenic disturbance (i.e., less disturbed mountainous area, wastewater discharged urban area, and pesticide and fertilizer applied agricultural area) based on environmental physicochemical indices (PCIs), microbiological indices (MBIs), and their combination. Results showed that among the PCI-based models, using conventional water quality indices as inputs provided markedly better prediction of water sample source than using pharmaceutical and personal care products (PPCPs), and much better prediction than using polycyclic aromatic hydrocarbons (PAHs) and substituted PAHs (SPAHs). Among the MBI-based models, using the abundances of the top 30 bacteria combined with pathogenic antibiotic resistant bacteria (PARB) as inputs achieved the lowest median out-of-bag error rate (9.9%) and increased median kappa coefficient (0.8694), while adding fungal inputs reduced the kappa coefficient. The model based on the top 30 bacteria still showed an advantage compared with models based on PCIs or the combination of PCIs and MBIs. With improvement in sequencing technology and increase in data availability in the future, the proposed method provides an economical, rapid, and reliable way in which to identify water sample sources based on abundance data of microbial communities.
Asunto(s)
Intervención Coronaria Percutánea , Hidrocarburos Policíclicos Aromáticos , Contaminantes Químicos del Agua , Ecosistema , Monitoreo del Ambiente , Aprendizaje Automático , Hidrocarburos Policíclicos Aromáticos/análisis , Ríos , Aguas Residuales/análisis , Agua , Contaminantes Químicos del Agua/análisisRESUMEN
Upgrades of wastewater treatment plant (WWTP) and full-scale application of additional advanced oxidation processes have been proven to be effective in reducing the nutrient emissions to the environment; however, the impacts of WWTP upgrades on the receiving waters with regard to the occurrence and ecological risks of pharmaceuticals are still unclear. In this study, 27 pharmaceuticals with diverse physicochemical properties were monitored in four rivers in Beijing, each of which was heavily impacted by a large-scale WWTP. Three-year sampling campaigns were conducted, covering the periods before and after the WWTP upgrades. The results show that the newly added combined treatment processes (e.g., biological filter, ultrafiltration, ozonation, and NaClO disinfection) reduced the total pharmaceutical concentrations in the effluents by 45-74%. The composition profiles reveal that the upgrades of two studied WWTPs resulted in a significant reduction of pharmaceutical concentrations in the receiving rivers, while little impacts were observed for the other rivers. The risk assessment shows that the acute toxic pressures in the studied rivers were generally low and the WWTP upgrades were conducive to reduce the risks for most of pharmaceuticals. However, erythromycin and ofloxacin still posed high risk, indicating the potential adverse effect of pharmaceuticals on aquatic environment.
Asunto(s)
Preparaciones Farmacéuticas , Contaminantes Químicos del Agua , Purificación del Agua , Beijing , Monitoreo del Ambiente , Ríos , Aguas Residuales/análisis , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/toxicidadRESUMEN
The influence of compound microbial agents on antibiotic resistance genes (ARGs) in pig manure composting was investigated. The results show that the addition of microbial agents promoted the reduction of total ARGs and the maximum removal efficiencies for absolute abundance (77.2%) and relative abundance (64.5%) were observed in the repeated dose and high dose groups, respectively. Four categories of ARGs declined with the reduction of Firmicutes and Tn916/1545, whereas two categories increased with the proliferation of intI1 and various potential hosts in the composting. The ARG profiles and bacterial communities were shaped by composting stages (mesophilic-thermophilic and cooling-maturation stages) in all groups. However, the addition of microbial agents accelerated the variation of composting stages, and may change the potential ARG hosts which influences the removal of ARGs. Of note, intI1 and two potential pathogens (Mycobacterium and Bacillus) correlated positively to several increased ARGs, implying the possible risks of compost products.
Asunto(s)
Compostaje , Animales , Antibacterianos/farmacología , Farmacorresistencia Microbiana/efectos de los fármacos , Farmacorresistencia Microbiana/genética , Genes Bacterianos , Estiércol , PorcinosRESUMEN
The variation of antibiotic resistance genes (ARGs) and influential factors in pig manure composting were investigated by conducting simulated composting tests using four different supplement materials (wheat straw, corn straw, poplar sawdust and spent mushroom). The results show that the relative abundance of total ARGs increased by 0.19-1.61 logs after composting, and tetX, sulI, sulII, dfrA1 and aadA were the major contributors. The variations of ARG profiles and bacterial communities throughout the composting were clearly divided into mesophilic-thermophilic and cooling-maturation stages in all tests, while different supplement materials did not exert a noticeable influence. Network analysis demonstrated the diversity of bacterial hosts for ARGs, the existence of multiple antibiotic resistant bacteria, and the weak correlations between ARGs and physicochemical factors in the composting piles. Of note, integron intI1 and Mycobacterium (a potential pathogen) were positively correlated with eight and four ARGs, respectively, that displayed increased abundance after composting.
Asunto(s)
Compostaje , Farmacorresistencia Microbiana/genética , Agaricales , Animales , Antibacterianos , Bacterias/efectos de los fármacos , Genes Bacterianos/efectos de los fármacos , Integrones , Estiércol/análisis , Porcinos , Zea mays/efectos de los fármacosRESUMEN
This study investigated the occurrence of 27 pharmaceuticals with diverse physicochemical properties in a year-long monitoring campaign in the Chaobai River, China. The correlation between the distribution of pharmaceuticals in the river and the adjacent sources was elucidated. The results indicate that the agriculture area was the most polluted area with a median summed pharmaceutical concentration of 225.3 ng L-1, followed by the urban area and the mountain area with the corresponding values of 136.9 and 29.9 ng L-1, respectively. In terms of individual compounds, 22 out of 27 compounds were detected with concentrations ranging from <1 to 1972 ng L-1. Caffeine, carbamazepine, azithromycin, bezafibrate, metoprolol, sulfadiazine, sulfamethoxazole, clarithromycin, erythromycin, roxithromycin, and trimethoprim were pharmaceuticals with relatively high levels, with median concentrations ranging from 3.3 to 25.6 ng L-1 and detection frequencies ranging from 40% to 97%. Higher concentrations were mainly observed during cold seasons, with mean concentrations 1 to 52 times as high as those during warm seasons. Spatial analysis reveals that the pharmaceutical concentrations in different areas were impacted by different sources. A wastewater treatment plant was an important source in the urban area, while the agriculture area was impacted by various treated and untreated wastewater sources. The species sensitivity distribution model and risk quotient (RQ) method were combined in the ecological risk assessment. The results indicate that the multi-substance potentially affected fraction (msPAF) values of the sampling sites were below 0.04%, whereas nearly half of RQ values were higher than 1. Caffeine was proposed as a priority compound due to its high contribution rate (i.e., 79%) to the cumulative msPAF value, which implies that increased control and management of untreated wastewater sources along the Chaobai River is necessary.
Asunto(s)
Ríos , China , Monitoreo del Ambiente , Preparaciones Farmacéuticas , Medición de Riesgo , Contaminantes Químicos del AguaRESUMEN
Two sequencing batch reactors were established at bench-scale, with one used as an in-situ sludge ozone-reduction system and the other as a control system. Both systems were continuously operated for 90 days to comparatively investigate the elimination of nine typical antibiotics (i.e., tetracycline, oxytetracycline, doxytetracycline, norfloxacin, ofloxacin, ciprofloxacin, lomefloxacin, enrofloxacin, and azithromycin) during the in-situ sludge ozone-reduction process. Results indicated that the presence of target antibiotics in the influent (100 µg·L-1 each) had an insignificant influence on the removal of COD, total nitrogen, ammonia, and total phosphorus by the activated sludge. The antibiotic concentrations in the effluent of the reduction system remained fairly stable over the entire operation period, and were similar to those in the effluent of the control system; however, the antibiotic concentrations in the sludge of the reduction system were obviously lower than those in the control system sludge. Mass balance calculations revealed that the input and output of target antibiotics gradually approached balance in both the systems. Ozone degradation and excess sludge discharge were the main pathways for target antibiotic removal in the reduction and the control systems, respectively. The influent antibiotics could be degraded by 83% in the sludge ozonation module of the reduction system, while 82% of the influent antibiotics were discharged with excess sludge in the control system. Therefore, the in-situ sludge ozone-reduction process could greatly reduce the release of antibiotics from the activated sludge system, which is of great importance in practice.
Asunto(s)
Antibacterianos/aislamiento & purificación , Ozono/química , Aguas del Alcantarillado , Eliminación de Residuos Líquidos/métodos , Amoníaco , Reactores Biológicos , Nitrógeno , Oxígeno , FósforoRESUMEN
The combination of chlorine and UV (i.e., chlorine-UV process) has been attracting more attention in recent years due to its ready incorporation into existing water treatment facilities to remove PPCPs. However, limited information is available on the impact of total ammonia nitrogen (TAN). This study investigated two model PPCPs, N,N-diethyl-3-toluamide (DEET) and caffeine (CAF), in the two stages of the chlorine-UV process (i.e., chlorination and UV/chlor(am)ine) to elucidate the impact of TAN. During chlorination, the degradation of DEET and CAF was positively correlated with the overall consumption of total chlorine by TAN. Reactive nitrogen intermediates, including HNO/NO- and ONOOH/ONOO-, along with â¢OH were identified as major contributors to the removal of DEET and CAF. During UV irradiation, DEET and CAF were degraded under UV/chlorine or UV/NH2Cl conditions. â¢OH and â¢Cl were the major reactive species to degrade DEET and CAF under UV/NH2Cl conditions, whereas â¢OCl played a major role for degrading CAF under UV/chlorine conditions. Numerical models were developed to predict the removal of DEET and CAF under chlorination-UV process. Chlorinated disinfection byproducts were detected. Overall, this study presented kinetic features and mechanistic insights on the degradation of PPCPs under the chlorine-UV process in ammoniacal water.
Asunto(s)
Contaminantes Químicos del Agua , Purificación del Agua , Cloro , Desinfección , Halogenación , Rayos Ultravioleta , AguaRESUMEN
Ozonation is a promising means for the reduction of excess sludge in wastewater treatment plants. However, little information is available on the removal of antibiotics during sludge ozonation. Therefore, this study investigated first the behavior of four commonly-used hydrophobic antibiotics, including three tetracyclines (tetracycline, oxytetracycline, and doxycycline) and one macrolide (azithromycin) in activated sludge process and then their removal during sludge reduction by ozone. Results indicate that the studied antibiotics were primarily transferred into the solid phase of activated sludge via sorption, which was a reversible, spontaneous, and exothermic process governed by surface reactions. Sludge ozonation could effectively remove 86.4-93.6% of the antibiotics present in the sludge at an ozone dose of 102â¯mg per gram of mixed liquor suspended solids and pH 7.2. The removal of studied antibiotics mainly proceeded through desorption and subsequent oxidation. Increasing the initial pH from 5.0 to 9.5 obviously enhanced the antibiotic removal during sludge ozonation. This study demonstrated that the activated sludge process coupled with sludge ozonation can simultaneously reduce excess sludge and eliminate antibiotics.
Asunto(s)
Antibacterianos/química , Ozono/química , Aguas del Alcantarillado/química , Tetraciclina/químicaRESUMEN
The degradation kinetics and mechanism of two typical fluoroquinolones (FQs), norfloxacin (NF) and levofloxacin (LOF), by ozone in water were investigated. Semi-continuous mode and competition kinetics mode experiments were conducted to determine the reaction rate constants of target FQs with ozone and OH, separately. Results indicate that both NF and LOF were highly reactive toward ozone, and the reactivity was strongly impacted by the solution pH. The specific reaction rate constants of the diprotonated, monoprotonated and deprotonated species were determined to be 7.20â¯×â¯102, 8.59â¯×â¯103, 4.54â¯×â¯105â¯M-1â¯s-1 respectively for NF and 1.30â¯×â¯103, 1.40â¯×â¯104, 1.33â¯×â¯106â¯M-1â¯s-1 respectively for LOF. The reaction rate constants of target FQs toward OH were measured to be (4.81-7.41)â¯×â¯109â¯M-1â¯s-1 in the pH range of 6.3-8.3. Furthermore, NF was selected as a model compound to clarify the degradation pathways, with a particular focus on the defluorination reaction. The significant release of F- ions and the formation of three F-free organic byproducts indicated that defluorination was a prevalent pathway in ozonation of FQs, while six F-containing organic byproducts indicated that ozone also attacked the piperazinyl and quinolone moieties. Escherichia coli growth inhibition tests revealed that ozonation could effectively eliminate the antibacterial activity of target FQ solutions, and the residual antibacterial activity had a negative linear correlation with the released F- concentration.
Asunto(s)
Levofloxacino/química , Norfloxacino/química , Ozono/química , Agua/química , Antibacterianos/química , Fluoroquinolonas/química , Halogenación , Cinética , Contaminantes Químicos del Agua/químicaRESUMEN
This study investigated the occurrence, removal and risk of 42 organic micropollutants (MPs), including 30 pharmaceuticals and personal care products and 12 endocrine disrupting chemicals, in 14 municipal wastewater treatment plants (WWTPs) distributed across China. The composition profiles of different MP categories in the influent, effluent, and excess sludge were explored and the aqueous removal efficiencies of MPs were determined. Quantitative meta-analysis was performed to compare the efficacies of different wastewater treatment processes in eliminating MPs. Results indicate that different MP categories showed quite similar distributions among the studied WWTPs, with phenolic estrogenic compounds (PEs), macrolides, and fluoroquinolones being always dominant in the influent, effluent and excess sludge. Tetracyclines, bezafibrate, caffeine, steroid estrogens, and PEs showed high and stable aqueous removal efficiencies, whereas other MPs showed considerably varied aqueous removal efficiencies. Anaerobic/anoxic/oxic process combined with a moving-bed biofilm reactor achieved the highest aqueous removal of MPs among various secondary treatment processes. A combined process consisting of ultrafiltration, ozonation and ClO2 disinfection resulted in the highest removal of MPs among the tertiary treatment processes. Sulfamethoxazole, ofloxacin, ciprofloxacin, clarithromycin, erythromycin, estrone, and bisphenol A in the effluent, as well as ß-estradiol 3-sulfate in the excess sludge could pose high risks. This study draws an overall picture about the current status of MPs in WWTPs across China and provides useful information for better control of the risks associated with MPs.
Asunto(s)
Disruptores Endocrinos/análisis , Aguas Residuales/química , Contaminantes Químicos del Agua/análisis , Purificación del Agua/métodos , Reactores Biológicos , China , Riesgo , Aguas del Alcantarillado/química , Contaminantes Químicos del Agua/químicaRESUMEN
Natural estrogens (NEs) discharged from wastewater treatment plants (WWTPs) have drawn great attention because of their potential risks to aquatic ecosystems. However, neglect of the conjugated natural estrogens (C-NEs) has caused large discrepancies among different studies on the removal of NEs in WWTPs. The present work investigated the transformation and fate of three NEs and six corresponding C-NEs along wastewater treatment processes. The removal efficiencies of the target estrogens (i.e., NEs and C-NEs) and their correlations with the operational parameters were determined over a twelve-month monitoring period at a typical WWTP adopting a combined bio-treatment process (i.e., anaerobic/anoxic/oxic process followed by a moving-bed biofilm reactor). The concentration variations of the target estrogens along the treatment processes were examined to differentiate the transformation and fate of NEs and C-NEs. Moreover, lab-scale experiments were conducted to clarify the removal pathways of C-NEs in the bio-treatment process. Results indicate that both NEs and C-NEs could pass through the treatment processes, thus being frequently detected in the effluent and excess sludge. The aqueous removal efficiencies of NEs and C-NEs were significantly correlated with the sludge retention time and temperature, respectively. C-NEs were more persistent than NEs, so considerably high conjugated ratios (13.5-100.0%) were detected in the effluent. Sulfate conjugates presented a lower adsorption affinity to sludge and a slower hydrolysis rate than glucuronide conjugates, which makes the former more recalcitrant to biodegradation. This study highlights the challenge on the elimination of NEs, particularly their conjugates, by wastewater treatment processes.
Asunto(s)
Estrógenos/análisis , Aguas Residuales , Contaminantes Químicos del Agua/análisis , Monitoreo del Ambiente , Estrógenos/química , Aguas del Alcantarillado , Eliminación de Residuos Líquidos , Contaminantes Químicos del Agua/químicaRESUMEN
The detailed sorption steps and biodegradation characteristics of fluoroquinolones (FQs) including ciprofloxacin, enrofloxacin, lomefloxacin, norfloxacin, and ofloxacin were investigated through batch experiments. The results indicate that FQs at a total concentration of 500µg/L caused little inhibition of sludge bioactivity. Sorption was the primary removal pathway of FQs in the activated sludge process, followed by biodegradation, while hydrolysis and volatilization were negligible. FQ sorption on activated sludge was a reversible process governed by surface reaction. Henry and Freundlich models could describe the FQ sorption isotherms well in the concentration range of 100-300µg/L. Thermodynamic parameters revealed that FQ sorption on activated sludge is spontaneous, exothermic, and enthalpy-driven. Hydrophobicity-independent mechanisms determined the FQ sorption affinity with activated sludge. The zwitterion of FQs had the strongest sorption affinity, followed by cation and anion, and aerobic condition facilitated FQ sorption. FQs were slowly biodegradable, with long half-lives (>100hr). FQ biodegradation was enhanced with increasing temperature and under aerobic condition, and thus was possibly achieved through co-metabolism during nitrification. This study provides an insight into the removal kinetics and mechanism of FQs in the activated sludge process, but also helps assess the environmental risks of FQs resulting from sludge disposal.
Asunto(s)
Antibacterianos/análisis , Fluoroquinolonas/análisis , Eliminación de Residuos Líquidos/métodos , Contaminantes Químicos del Agua/análisis , Adsorción , Biodegradación Ambiental , Aguas del AlcantarilladoRESUMEN
Levofloxacin (LF) is a frequently detected fluoroquinolone in surface water, and permanganate (MnO4-) is a commonly used oxidant in drinking water treatment. This study investigated the impact of humic acid (HA) on LF degradation by aqueous MnO4- from both kinetic and mechanistic aspects. In the absence of HA, the second-order rate constant (k) of LF degradation by MnO4- was determined to be 3.9 M-1 s-1 at pH 7.5, which increased with decreasing pH. In the presence of HA, the pseudo-first-order rate constant (kobs) of LF degradation at pH 7.5 was significantly increased by 3.8- and 2.8-fold at [HA]o:[KMnO4]o (mass ratio) = 0.5 and 1, respectively. Secondary oxidant scavenging and electron paramagnetic resonance tests indicated that HA could form a complex with Mn(III), a strongly oxidative intermediate produced in the reaction of MnO4- with HA, to induce the successive formation of superoxide radicals (O2-) and hydroxyl radicals (OH). The resulting OH primarily contributed to the accelerated LF degradation, and the complex [HA-Mn(III)] could account for the rest of acceleration. The degradation of LF and its byproducts during MnO4- oxidation was mainly through hydroxylation, dehydrogenation and carboxylation, and the presence of HA led to a stronger destruction of LF. This study helps better understand the degradation of organic micropollutants by MnO4- in drinking water treatment.
Asunto(s)
Sustancias Húmicas , Levofloxacino/química , Contaminantes Químicos del Agua/química , Cinética , Compuestos de Manganeso , Oxidación-Reducción , ÓxidosRESUMEN
The occurrence of antibiotics in the environment has recently raised serious concern regarding their potential threat to aquatic ecosystem and human health. In this study, the magnetic ion exchange (MIEX) resin was applied for removing three commonly-used antibiotics, sulfamethoxazole (SMX), tetracycline (TCN) and amoxicillin (AMX) from water. The results of batch experiments show that the maximum adsorption capacities on the MIEX resin for SMX, TCN and AMX were 789.32, 443.18 and 155.15µg/mL at 25°C, respectively, which were 2-7 times that for the powdered activated carbon. The adsorption kinetics of antibiotics on the MIEX resin could be simulated by the pseudo-second-order model (R2=0.99), and the adsorption isotherm data were well described by the Langmuir model (R2=0.97). Solution pH exhibited a remarkable impact on the adsorption process and the absorbed concentrations of the tested antibiotics were obtained around the neutral pH. The MIEX resin could be easily regenerated by 2mol/L NaCl solution and maintained high adsorption removal for the tested antibiotics after regeneration. Anion exchange mechanism mainly controlled the adsorption of antibiotic and the formation of hydrogen binding between the antibiotic and resin can also result in the increase of adsorption capacity. The high adsorption capacity, fast adsorption rate and prominent reusability make the MIEX resin a potential adsorbent in the application for removing antibiotics from water.
Asunto(s)
Absorción Fisicoquímica , Antibacterianos/química , Resinas de Intercambio Iónico/química , Magnetismo , Contaminantes Químicos del Agua/química , Purificación del Agua/métodos , Intercambio IónicoRESUMEN
Municipal wastewater treatment plant (WWTP) effluents represent an important contamination source of antibiotic resistance, threatening the ecological safety of receiving environments. In this study, the release of antibiotic resistance to sulfonamides and tetracyclines in the effluents of ten WWTPs in China was investigated. Results indicate that the concentrations of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) ranged from 1.1 × 101 to 8.9 × 103 CFU mL-1 and 3.6 × 101 (tetW) to 5.4 × 106 (tetX) copies mL-1, respectively. There were insignificant correlations of the concentrations of ARB and ARGs with those of corresponding antibiotics. Strong correlations were observed between the total concentrations of tetracycline resistance genes and sulfonamide resistance genes, and both of which were significantly correlated with intI1 concentrations. Statistical analysis of the effluent ARG concentrations in different WWTPs revealed an important role of disinfection in eliminating antibiotic resistance. The release rates of ARB and ARGs through the effluents of ten WWTPs ranged from 5.9 × 1012 to 4.8 × 1015 CFU d-1 and 6.4 × 1012 (tetW) to 1.7 × 1018 (sul1) copies d-1, respectively. This study helps the effective assessment and scientific management of ecological risks induced by antibiotic resistance discharged from WWTPs.
Asunto(s)
Bacterias/genética , Farmacorresistencia Microbiana , Eliminación de Residuos Líquidos/métodos , Aguas Residuales/análisis , Microbiología del Agua , Purificación del Agua/métodos , Antibacterianos/análisis , Bacterias/efectos de los fármacos , China , Desinfectantes/química , Desinfección , Transferencia de Gen Horizontal , Genes Bacterianos , ARN Ribosómico 16S/química , Aguas del Alcantarillado/microbiología , Sulfonamidas/análisis , Resistencia a la Tetraciclina/genética , Tetraciclinas/análisis , Contaminantes Químicos del Agua/químicaRESUMEN
This work investigated the dissemination of antibiotic resistance genes (ARGs) encoding resistance to sulfonamide and tetracycline antibiotics in nine swine feedlots located in Shandong Province of China, and examined their potential removal by various on-farm treatment processes. Results indicate that the target ARGs were widely distributed in swine wastes, with mean relative abundances ranging from 3.3 × 10-5 (tetC) to 5.2 × 10-1 (tetO) in swine manure and from 7.3 × 10-3 (tetC) to 1.7 × 10-1 (tetO) in swine wastewater. The mean relative ARG abundances ranged from 9.9 × 10-5 (tetW) to 1.1 × 10-2 (tetO) in soils and from 3.1 × 10-4 (tetW) to 1.1 × 10-2 (sul2) in receiving river sediments, indicating that the farmland application of swine manure compost and the discharge of swine wastewater promoted the dissemination of ARGs into adjacent environments. Microbial fermentation bed (MFB) could reduce the relative ARG abundances by 0-1.18 logs. However, septic tank, biogas digester and natural drying methods were relatively ineffective for ARG removal, and the relative abundances of some ARGs (i.e., tetC, tetG, sul1, and sul2) even increased by 0.74-3.90 logs in treated wastes. Bacterial diversity analysis indicates that the evolution of bacterial communities in the MFB played a crucial role in eliminating the ARGs. This study helps the effective assessment and management of ecological risks arising from ARGs in swine feedlots.
Asunto(s)
Antibacterianos/análisis , Farmacorresistencia Microbiana/genética , Genes Bacterianos , Estiércol/microbiología , Aguas Residuales/microbiología , Contaminantes Químicos del Agua/análisis , Animales , Antibacterianos/toxicidad , China , Granjas , Sedimentos Geológicos/microbiología , Estiércol/análisis , ARN Ribosómico 16S/genética , Ríos/microbiología , Microbiología del Suelo , Porcinos , Aguas Residuales/química , Contaminantes Químicos del Agua/toxicidadRESUMEN
Swine feedlots are an important pollution source of antibiotics and antibiotic resistance genes (ARGs) to the environment. This study investigated the dissemination of two classes of commonly-used veterinary antibiotics, namely, tetracyclines (TCs) and sulfonamides (SAs), and their corresponding ARGs along the waste treatment paths from a concentrated swine feedlot located in Beijing, China. The highest total TC and total SA concentrations detected were 166.7mgkg(-1) and 64.5µgkg(-1) in swine manure as well as 388.7 and 7.56µgL(-1) in swine wastewater, respectively. Fourteen tetracycline resistance genes (TRGs) encoding ribosomal protection proteins (RPP), efflux proteins (EFP) and enzymatic inactivation proteins, three sulfonamide resistance genes (SRGs), and two integrase genes were detected along the waste treatment paths with detection frequencies of 33.3-75.0%. The relative abundances of target ARGs ranged from 2.74×10(-6) to 1.19. The antibiotics and ARGs generally declined along both waste treatment paths, but their degree of reduction was more significant along the manure treatment path. The RPP TRGs dominated in the upstream samples and then decreased continuously along both waste treatment paths, whilst the EFP TRGs and SRGs maintained relatively stable. Strong correlations between antibiotic concentrations and ARGs were observed among both manure and wastewater samples. In addition, seasonal temperature, and integrase genes, moisture content and nutrient level of tested samples could all impact the relative abundances of ARGs along the swine waste treatment paths. This study helps understand the evolution and spread of ARGs from swine feedlots to the environment as well as assess the environmental risk arising from swine waste treatment.
Asunto(s)
Antibacterianos/química , Antibacterianos/farmacología , Bacterias/genética , Eliminación de Residuos Líquidos , Aguas Residuales/química , Aguas Residuales/microbiología , Animales , Beijing , China , Farmacorresistencia Microbiana/genética , Ambiente , Monitoreo del Ambiente , Genes Bacterianos , Estiércol/análisis , Porcinos , Contaminantes Químicos del AguaRESUMEN
The co-exposure to UV irradiation and free chlorine may occur in certain drinking water and wastewater treatment systems. This study investigated the effects of simultaneous low pressure ultraviolet (LPUV) irradiation and free chlorination on the formation of chloroform from triclosan which is a commonly used antibacterial agent. Different treatment systems (i.e., combined UV/chlorine, UV alone, and chlorine alone) were applied to examine the degradation of triclosan and formation of chloroform. The fate of representative intermediates, including chlorinated triclosan, dechlorinated triclosan intermediates and 2,4-dichlorophenol, were tracked to deduce the effect of combined UV/chlorine on the transformation of chloroform formation precursors. The relation between intermediates degradation and chloroform formation was investigated in depth by conducting stepwise experiments with UV and chlorine in different sequences. Results indicate that the combined UV/chlorine notably enhanced the chloroform formation from triclosan. From the reaction mechanism perspective the combined UV/chlorine, where the direct photolysis may play an important role, could accelerate the decay of intermediates and facilitate the generation of productive chloroform precursors. The radicals had modest influence on the degradation of triclosan and intermediates and partly hindered the formation of chloroform. These results emphasize the necessity of considering disinfection by-products formation in the application of combined UV/chlorine technology during water treatment.