Vertical up-flow constructed wetlands exhibited efficient antibiotic removal but induced antibiotic resistance genes in effluent

Removal performance of antibiotics and antibiotic resistance genes in swine wastewater by integrated vertical-flow constructed wetlands with zeolite substrate

Antibiotics and antibiotic resistance genes (ARGs) in swine wastewater have an irreversible impact on the surrounding water and soil ecosystems. Herein, integrated vertical-flow constructed wetlands (IVCWs) were constructed to assess the effects of zeolite and plants on the removal of sulfonamides (SMs), tetracyclines (TCs), and related ARGs (tetW, tetO, tetM, sul I, sul II, and sul III) from digested swine wastewater. The microorganism community structure was also investigated. Results showed that IVCWs with a zeolite substrate and plant system (ZP) exhibited a favorable removal performance for N, antibiotics, and ARGs at 97.9%, 95.0%, and 95.1%, respectively. Moreover, zeolite systems showed higher adsorption of SMs, lower adsorption of TCs. The higher removal rate of antibiotics in ZP systems might be due to the enhanced microbial degradation with the enrichment of Pseudomonas, Acinetobacter, and Bacillus in zeolite. Furthermore, Arundo donax had limited impact on antibiotics removal and was not conducive to the removal of ARGs. The absolute abundances of sul(I), sul(II), sul(III), tet(M), and tet(O) were significantly positively correlated with the absolute abundance of 16S rDNA. However, no significant correlation was found between the concentration of antibiotics and the abundance of related ARGs in the effluent.

Evaluation of the fate of nutrients, antibiotics, and antibiotic resistance genes in sludge treatment wetlands

The aim of this research was to analyze the elimination of nutrients, antibiotics as well as antibiotic resistance genes (ARGs) in different sludge treatment wetlands (STWs) with or without reeds and aeration tubes. Five antibiotics, including oxytetracycline, tetracycline, azithromycin, sulfamethoxazole, and sulfadiazine; five ARGs, including two tetracycline ARGs (tetC and tetA), one macrolide ARGs (ermB), and two sulfonamide ARGs (sul1 and sul2); and one integrase gene (intI1) were determined in the surface and bottom layers of three STWs, respectively. The removal efficiencies of antibiotics in the bottom layer were lower than that in the surface layer, while the elimination efficiencies of ARGs showed opposite trend. Strong correlations were observed among the contents of antibiotics as well as related ARGs, and the abundance of ARGs had a strong correlation with intI1. The results demonstrated that the contents of these pollutants decreased during the resting period in all the STWs, while the wetland had reeds and aeration tubes performed the best.

Microbial assisted phytodepuration for water reclamation: Environmental benefits and threats

Climate changes push for water reuse as a priority to counteract water scarcity and minimize water footprint especially in agriculture, one of the highest water consuming human activities. Phytodepuration is indicated as a promising technology for water reclamation, also in the light of its economic and ecological sustainability, and the use of specific bacterial inocula for microbial assisted phytodepuration has been proposed as a further advance for its implementation. Here we provided an overview on the selection and use of plant growth promoting bacteria in Constructed Wetland (CW) systems, showing their advantages in terms of plant growth support and pollutant degradation abilities. Moreover, CWs are also proposed for the removal of emerging organic pollutants like antibiotics from urban wastewaters. We focused on this issue, still debated in the literature, revealing the necessity to deepen the knowledge on the antibiotic resistance spread into the environment in relation to treated wastewater release and reuse. In addition, given the presence in the plant system of microhabitats (e.g. rhizosphere) that are hot spot for Horizontal Gene Transfer, we highlighted the importance of gene exchange to understand if these events can promote the diffusion of antibiotic resistance genes and antibiotic resistant bacteria, possibly entering in the food production chain when treated wastewater is used for irrigation. Ideally, this new knowledge will lead to improve the design of phytodepuration systems to maximize the quality and safety of the treated effluents in compliance with the 'One Health' concept.

Rapid removal of tetracycline by Myriophyllum aquaticum: Evaluation of the role and mechanisms of adsorption

As a floating plant, Myriophyllum aquaticum provides a large surface area under water, and thus has high potential for the removal of pollutants through adsorption. The aim of this study was to evaluate the potential adsorption of tetracycline (TC) by M. aquaticum, and examine the underlying mechanisms. M. aquaticum exhibited a high potential for TC removal from water. Adsorption was the main mechanism for rapid TC removal by live M. aquaticum plants, due to its large contact area and ion exchange, accounting for about 99% and 54% of the total amount of TC removed within 2 h and 5 d, respectively. Further, the roots of M. aquaticum exhibited a higher adsorption capacity than the stems or leaves, as the roots had the largest specific surface area. Fourier transform infrared spectroscopy analysis and identification of functional groups showed that -OH, -COOH, and -NH₂ groups are involved in the adsorption process. The use of M. aquaticum may be a promising approach for TC removal from aquatic environments, especially in terms of shortening reaction times.

Effect of copper on the removal of tetracycline from water by Myriophyllum aquaticum: Performance and mechanisms

Pollution with antibiotics and heavy metals necessitates efficient approaches for their removal. This study was conducted to investigate the role of Cu in the tetracycline (TC) removal potential of the floating plant Myriophyllum aquaticum and determine the underlying mechanisms. Myriophyllum aquaticum exhibited high TC removal potential from water (60% at 50 mg·L^-1 TC and 10 g·L^-1M. aquaticum). Adsorption was the main mechanism of TC removal within 2 h, accounting for over 75% and 90% of total TC removal with and without Cu(II), respectively. Fourier-transform infrared spectroscopy and functional group identification showed that OH, COOH, and NH₂ were involved in TC adsorption through ion exchange. Cu(II) may act as a bridge during TC adsorption with M. aquaticum, but competitive adsorption of Cu(II) and TC on M. aquaticum occurs in case of excessive Cu(II). Myriophyllum aquaticum can serve as an important bioresource for effectively removing TC and Cu(II) from aquatic environments.

Wetlands for wastewater treatment

This article presents an update on the research and practical demonstration of wetland treatment technologies for wastewater treatment. Applications of wetlands in wastewater treatment (as an advanced treatment unit or a decentralized system) and stormwater management or treatment for nutrient and pollutant removal (metals, industrial and emerging pollutants including pharmaceutical compounds and pathogens) are highlighted. A summary of studies involving the effects of vegetation, wetland design and operation, and configurations for efficient treatment of various municipal and industrial wastewaters is also included. PRACTITIONER POINTS: Provides an update on current research and development of wetland technologies for wastewater treatment. Effects of vegetation, pathogens removal, heavy metals and emerging pollutants removal are included. Wetland design and operation is a key factor to improve water quality of wetland effluent.

Electrochemical removal of amoxicillin using a Cu doped PbO2 electrode: Electrode characterization, operational parameters optimization and degradation mechanism

This work investigated the electrochemical degradation of amoxicillin (AMX) in aqueous solution with Cu-PbO2 electrode. The main influence factors on the degradation of AMX, such as Na2SO4 concentration, initial AMX concentration, current density and initial pH value, were analyzed in detail. Under the optimal conditions, the removal rates of AMX and chemical oxygen demand (COD) reached 99.4% and 46.3% after 150 min treatment. The results indicated that the electrochemical degradation of AMX fitted pseudo-first-order reaction kinetics. Compared with undoped PbO2 electrode, Cu-PbO2 electrode had a smaller crystal size, more proportion of hydroxyl oxygen species, greater AMX and chemical oxygen demand (COD) removal efficiency, higher average current efficiency (ACE) and lower electrical efficiency per log order (EE/O). Electrochemical oxidation using Cu-PbO2 electrodes was an effective way to eliminate amoxicillin in aqueous solution. Moreover, a possible degradation pathway including ring open and mineralization was proposed by intermediate products determined by GC-MS method. This paper could provide basic data and technique reference for the amoxicillin wastewater pollution control.

Occurrence and removal of antibiotics and antibiotic resistance genes in natural and constructed riverine wetlands in Beijing, China

Simultaneous elimination of antibiotics and antibiotic resistance genes (ARGs) is rarely investigated in full-scale riverine wetlands. Here, we compared the occurrence, abundance, and removal of 60 antibiotics and 27 ARGs in natural (Yeya Lake (YL)) and constructed (Bai River (BR)) riverine wetlands in Beijing, China. The concentrations of antibiotics in YL wetland were ND-51.9 ng/L in water and ND-37.9 ng/g in sediments. Significantly higher concentrations were found in BR wetland (ND-546 ng/L in water and ND-118 ng/g in sediments), which locates at the downstream of a reclaimed water treatment plant. The abundances of ARGs in YL and BR wetlands were up to 5.33 × 10⁵ and 8.41 × 10⁵ copies/mL in water, and 1.60 × 10⁷ and 4.67 × 10⁸ copies/g in sediments, respectively. These results suggest that wastewater greatly contributes to the elevated abundance of antibiotics and ARGs in both water and sediments. Compared to summer, higher levels of antibiotics in water were found in winter due to the higher usage, slower attenuation and the limited dilution. But higher abundances of ARGs were found in summer than in winter, in accordance with the favored microbial growth at higher temperature as denoted by copies of 16S rRNA. Compared to BR wetland, YL wetland achieved better removal of antibiotics and ΣARGs, with average removal efficiencies of 70.0% and 87.5%. Antibiotics, ARGs and environmental factors showed strong correlations in water samples from YL wetland. However, in BR wetland that receives urban wastewater effluents, no correlation between antibiotics and ARGs was found although the distribution of antibiotics was affected by aquatic environmental factors. These results indicate that subinhibitory concentrations of antibiotics may stimulate the prevalence of ARGs in natural wetlands.

Effects of pharmaceuticals on microbial communities and activity of soil enzymes in mesocosm-scale constructed wetlands

Cyperus alternifolius based mesocosm-scale constructed wetland was employed to remove pharmaceuticals. We investigated the microbial community composition using phosphor lipid fatty acids (PFLAs) analysis and substrate enzyme activity during long-term exposure to pharmaceuticals in mesocosm-scale constructed wetlands. The results showed that there was no visible inhibition effect of pharmaceuticals on CW substrate enzymes activities in the experimental range (0-500 μg/L). Microbial communities, as revealed by PFLAs, were enhanced by the presence of plants, while the PFLAs content was highest when the pharmaceutical concentration was 10 μg/L or 30 μg/L at CWs. Except for anaerobic bacteria and Saturated fatty acids, the maximum PLFAs levels were reached when the pharmaceuticals were 10 μg/L or 30 μg/L, while Bacteria, G (-), fungal bacteria, Aerobic bacteria and Monounsaturated fatty acids were remarkably affected by high pharmaceuticals (100-500 μg/L). However, the main microbial florae were not changed among the treatments. In this study, the removal efficiencies of the studied pharmaceuticals in Planted (30) was greatest, which could be attributed to the higher microbial biomass. These results indicate that C. alternifolius can phytoremediate pharmaceutical-contaminated waters in CWs. Individual fatty acid cannot be used to represent specific species; therefore, more approaches to species identification such as rRNA-based methods must be included in future studies to better understand the metabolic mechanisms of microorganisms involved in the removal of studied pharmaceuticals and improve the performance of CWs.