Environmental fate of Bacteroidetes, with particular emphasis on Bacteroides fragilis group bacteria and their specific antibiotic resistance genes, in activated sludge wastewater treatment plants

Removal of organic pollutants from paper mill effluent using Taro (Colocasia esculenta L. Schott) in an electro-assisted horizontal subsurface flow constructed wetland: Experimental and kinetic studies

In this study, the phytoremediation potential of Taro (Colocasia esculenta L. Schott) plant was examined, utilizing horizontal subsurface flow constructed wetlands with and without an electric current supply for the purpose of removing pollutants from paper mill effluent. For this, different wetlands were set up with varying concentrations of effluent: CW (Control), CW1 (25%), CW2 (50%), CW3 (75%), CW4 (100%). After 45 days, the highest plant height (85.13 ± 4.24 cm), leaf area index( 250.83 ± 10.14), fresh biomass (565.30 ± 6 .10 g), root biomass (392.85 ± 4.34 g), root-to-shoot ratio (2.41 ± 2.10), relative growth rate (0.044 ± 0.002 gg-1d-1), and chlorophyll content (3.29 ± 0.07 mg/g fwt) was observed in CW2 with current supply, along with significant removal of pollutants (pH: 7.13 ± 0.15, EC: 2.33 ± 0.07 dS/m, TDS: 192.52 ± 6.12 mg/L, COD: 490.17 ± 5.01 mg/L, BOD: 206.74 ± 5.92 mg/L, potassium: 73.27 ± 4.11 mg/L, sodium: 46.62 ± 2.27 mg/L, phosphate phosphorus: 34.08 ± 1.43 mg/L, and nitrate nitrogen: 104.85 ± 5.94 mg/L) and highest first-order rate constant (k) values. Furthermore, the microbial community assessment of constructed wetlands using V3-V4 16S rRNA sequence data was prepared on the Illumina MiSeq framework. The major phyla identified were Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, Chloroflexi, Acidobacteria, Nitrospirae, Planctomycetes, and others. The findings offer innovative insights for sustainable wastewater treatment strategies through phytoremediation of paper mill effluent using Taro plants in modified constructed wetlands and highlight the role of diverse microbial communities capable of degrading various pollutants in wastewater.

Aquatic macrophytes mitigate the conflict between nitrogen removal and nitrous oxide emissions during tailwater treatments

Tailwater from wastewater treatment plants (WWTP) usually reduces the nitrogen (N) removal efficiency while simultaneously elevates nitrous oxide (N2O) emissions due to the low carbon-nitrogen (C/N) ratio. Conflicts between N removal and N2O emissions require mitigation by selecting appropriate aquatic plants for tailwater treatment. In this study, a simulated tailwater mesocosm was established using three aquatic plants including Eichhornia crassipes, Myriophyllum aquaticum and Pistia stratiotes. Results of the 15N isotope mass balance analysis revealed the considerable contributions from plant uptake and benthic retention to overall N removal. It was demonstrated that the N assimilation efficiency of aquatic plants depended more on the root-shoot ratio rather than on growth rate. Furthermore, aquatic plants indirectly influence microbial N removal and N2O emissions by altering the water quality parameters. Additionally, aquatic plants could regulate the N transformation through affecting the structure of bacterial community, including microbial abundance, diversity and association networks. Overall, the study underlined the enormous capacities of E. crassipes and P. stratiotes for N uptake and N2O mitigation in tailwater treatment. Utilizing these two aquatic plants for phytoremediation may help mitigate the conflict between tailwater purification and N2O production.

Does exposure timing of macrolide antibiotics affect the development of river periphyton? Insights into the structure and function

Discharged sewage is the dominant source of urban river pollution. Macrolide antibiotics have emerged as prominent contaminants, which are frequently detected in sewage and rivers and pose a threat to aquatic microbial community. As a typical primary producer, periphyton is crucial for maintaining the biodiversity and functions of aquatic ecosystem. However, effects of antibiotic exposure time as well as the recovery process of periphyton remain undetermined. In the present study, five exposure scenarios of two typical macrolides, erythromycin (ERY) and roxithromycin (ROX) were investigated at 50 µg/L, dose to evaluate their potential detrimental effects on the structure and function of periphyton and the subsequent recovery process in 14 days. Results revealed that the composition of periphytic community returned to normal over the recovery period, except for a few sensitive species. The antibiotics-caused significant photodamage to photosystem II, leading to continuous inhibition of the photosynthetic capacity of periphyton. Furthermore, no significant difference in carbon metabolism capacity was observed after direct antibiotic exposure, while the amine carbon utilization capacity of periphyton remarkably increased during the recovery process. These results indicated that periphyton community was capable of coping with the periodic exposure of antibiotic pollutants and recovering on its own. However, the ecological functions of periphyton can be permanently disturbed due to macrolide exposure. Overall, this study sheds light on the influence of macrolide exposure on the development, structure and function of the periphytic microbial community in rivers.

Effects of coagulation pre-treatment on chemical and microbial properties of water-soil-plant systems of constructed wetlands

Chemical coagulation has gained recognition as an effective technique to enhance the removal efficiency of pollutants in wastewater prior to their entry into a constructed wetland (CW) system. However, its potential impact on the chemical and microbial properties of soil and plant systems within CWs requires further research. This study investigated the impact of using ferric chloride (FeCl3) as a pre-treatment stage for dairy wastewater (DWW) on the chemical and microbial properties of water-soil-plant systems of replicated pilot-scale CWs, comparing them to CWs treating untreated DWW. CWs treating amended DWW had better performance than CWs treating raw DWW for all water quality parameters (COD, TSS, TP, and TN), ensuring compliance with the EU wastewater discharge directives. Soil properties remained mostly unaffected except for pH, calcium and phosphorus (P), which were lower in CWs treating amended DWW. As a result of lower nitrogen (N) and P loads, the plants in CWs receiving FeCl3-amended DWW had lower N and P contents than the plants of raw DWW CWs. However, the lower loads of P into amended DWW CWs did not limit the growth of Phragmites australis, which were able to accumulate trace elements higher than CWs receiving raw DWW. Alpha and Beta-diversity analysis revealed minor differences in community richness and composition between both treatments, with only 3.7% (34 genera) showed significant disparities. Overall, the application of chemical coagulation produced superior effluent quality without affecting the properties of soil and plant of CWs or altering the functioning of the microbial community.

On-Site Inactivation for Disinfection of Antibiotic-Resistant Bacteria in Hospital Effluent by UV and UV-LED

The problem of antimicrobial resistance (AMR) is not limited to the medical field but is also becoming prevalent on a global scale in the environmental field. Environmental water pollution caused by the discharge of wastewater into aquatic environments has caused concern in the context of the sustainable development of modern society. However, there have been few studies focused on the treatment of hospital wastewater, and the potential consequences of this remain unknown. This study evaluated the efficacy of the inactivation of antimicrobial-resistant bacteria (AMRB) and antimicrobial resistance genes (AMRGs) in model wastewater treatment plant (WWTP) wastewater and hospital effluent based on direct ultraviolet (UV) light irradiation provided by a conventional mercury lamp with a peak wavelength of 254 nm and an ultraviolet light-emitting diode (UV-LED) with a peak emission of 280 nm under test conditions in which the irradiance of both was adjusted to the same intensity. The overall results indicated that both UV- and UV-LED-mediated disinfection effectively inactivated the AMRB in both wastewater types (>99.9% after 1-3 min of UV and 3 min of UV-LED treatment). Additionally, AMRGs were also removed (0.2-1.4 log10 for UV 254 nm and 0.1-1.3 log10 for UV 280 nm), and notably, there was no statistically significant decrease (p < 0.05) in the AMRGs between the UV and UV-LED treatments. The results of this study highlight the importance of utilizing a local inactivation treatment directly for wastewater generated by a hospital prior to its flow into a WWTP as sewage. Although additional disinfection treatment at the WWTP is likely necessary to remove the entire quantity of AMRB and AMRGs, the present study contributes to a significant reduction in the loads of WWTP and urgent prevention of the spread of infectious diseases, thus alleviating the potential threat to the environment and human health risks associated with AMR problems.

Entry pathways determined the effects of MPs on sludge anaerobic digestion system: The views of methane production and antibiotic resistance genes fates

Sludge is one of the primary reservoirs of microplastics (MPs), and the effects of MPs on subsequent sludge treatment raised attention. Given the entry pathways, MPs would exhibit different properties, but the entry pathway-dependent effect of MPs on sludge treatment performance and the fates of antibiotic resistance genes (ARGs), another high-risk emerging contaminant, were seldom documented. Herein, MPs with two predominant entry pathways, including wastewater-derived (WW-derived) and anaerobic digestion-introduced (AD-introduced), were used to investigate the effects on AD performance and ARGs abundances. The results indicated that WW-derived MPs, namely the MPs accumulated in sludge during the wastewater treatment process, exhibited significant inhibition on methane production by 22.8%-71.6%, while the AD-introduced MPs, being introduced in the sludge AD process, slightly increased the methane yield by 4.7%-17.1%. Meanwhile, MPs were responsible for promoting transmission of target ARGs, and polyethylene terephthalate MPs (PET-MPs) showed a greater promotion effect (0.0154-0.0936) than polyamide MPs (PA-MPs) (0.0013-0.0724). Compared to size, entry pathways and types played more vital roles on MPs influences. Investigation on mechanisms based on microbial community structure revealed characteristics (aging degree and types) of MPs determined the differences of AD performance and ARGs fates. WW-derived MPs with longer aging period and higher aging degree would release toxics and decrease the activities of microorganisms, resulting in the negative impact on AD performance. However, AD-introduced MPs with short aging period exhibited marginal impacts on AD performance. Furthermore, the co-occurrent network analysis suggested that the variations of potential host bacteria induced by MPs with different types and aging degree attributed to the dissemination of ARGs. Distinctively from most previous studies, the MPs with different sizes did not show remarkable effects on AD performance and ARGs fates. Our findings benefited the understanding of realistic environmental behavior and effect of MPs with different sources.

Wastewater surveillance of antibiotic resistance and class 1 integron-integrase genes: Potential impact of wastewater characteristics on genes profile

Antibiotic resistance (AR) is a major global health concern, but current surveillance efforts primarily focus on healthcare settings, leaving a lack of understanding about AR across all sectors of the One Health approach. To bridge this gap, wastewater surveillance provides a cost-effective and efficient method for monitoring AR within a population. In this study, we implemented a surveillance program by monitoring the wastewater effluent from two large-scale municipal treatment plants situated in Isfahan, a central region of Iran. These treatment plants covered distinct catchment regions and served a combined population about two million of residents. Furthermore, the effect of physicochemical and microbial characteristics of wastewater effluent including biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), temperature, total coliforms and Escherichia coli concentration on the abundance of ARGs (blaCTX-M, tetW, sul1, cmlA, and ermB) and class 1 integron-integrase gene (intI1) were investigated. Sul1 and blaCTX-M were the most and least abundant ARGs in the two WWTPs, respectively. Principal Component Analysis showed that in both of the WWTPs all ARGs and intI1 gene abundance were positively correlated with effluent temperature, but all other effluent characteristics (BOD, COD, TSS, total coliforms and E. coli) showed no significant correlation with ARGs abundance. Temperature could affect the performance of conventional activated sludge process, which in turn could affect the abundance of ARGs. The results of this study suggest that other factors than BOD, COD and TSS may affect the ARGs abundance. The predicted AR could lead to development of effective interventions and policies to combat AR in the clinical settings. However, further research is needed to determine the relationship between the AR in wastewater and clinical settings as well as the effect of other influential factors on ARGs abundance.

Wastewater treatment bacteria show differential preference for colonizing natural biopolymers

Most reduced organic matter entering activated sludge systems is particulate (1-100-µm diameter) or colloidal (0.001-1-µm diameter), yet little is known about colonization of particulate organic matter by activated sludge bacteria. In this study, colonization of biopolymers (chitin, keratin, lignocellulose, lignin, and cellulose) by activated sludge bacteria was compared with colonization of glass beads in the presence and absence of regular nutrient amendment (acetate and ammonia). Scanning electron microscopy and quantitative PCR revealed chitin and cellulose were most readily colonized followed by lignin and lignocellulose, while keratin and glass beads were relatively resistant to colonization. Bacterial community profiles on particles compared to sludge confirmed that specific bacterial phylotypes preferentially colonize different biopolymers. Nitrifying bacteria proved adept at colonizing particles, achieving higher relative abundance on particles compared to bulk sludge. Denitrifying bacteria showed similar or lower relative abundance on particles compared to sludge. KEY POINTS: • Some activated sludge bacteria colonize natural biopolymers more readily than others. • Nitrifying bacteria are overrepresented in natural biopolymer biofilm communities. • Biopolymers in wastewater likely influence activated sludge community composition.

Removal of sulfamethoxazole and Cu, Cd compound pollution by arbuscular mycorrhizal fungi enhanced vertical flow constructed wetlands

The combined pollution of antibiotics and heavy metals (HMs) has a serious impact on the water ecological environment. Previous researches mainly focused on the removal of antibiotics or HMs as single pollutants, with limited investigation into the treatment efficiencies and underlying mechanisms associated with their co-occurring pollution. In this study, 16 micro vertical flow constructed wetlands (MVFCWs) were constructed to treat composite wastewater consisting of sulfamethoxazole (SMX), copper (Cu) and cadmium (Cd), involving two different inoculation treatments (arbuscular mycorrhizal fungi (AMF) inoculated and uninoculated) and eight kinds of pollutant exposure (Control Check (CK), SMX, Cu, Cd, SMX + Cu, SMX + Cd, Cu + Cd, SMX + Cu + Cd). The findings of this study demonstrated that the inoculation of AMF in MVFCWs resulted in removal efficiencies of SMX, Cu, and Cd ranging from 18.70% to 80.52%, 75.18% to 96.61%, and 40.50% to 89.23%, respectively. Cu and CuCd promoted the degradation of SMX in the early stage and inhibited the degradation of SMX in the later stage. Cd did not demonstrate a comparable promotive impact on SMX degradation, and its addition hindered Cu removal. However, comparatively, the presence of Cu exerted a more pronounced inhibitory effect on Cd removal. Furthermore, the addition of Cu augmented the abundances of Proteobacteria, Bacteroidetes (at the phylum level) and Rhodobacter, Lacunisphaera and Flavobacterium (at the genus level), and Cu exposure showed a substantially stronger influence on the microbial community than that of Cd and SMX. AMF might confer protection to plants against HMs and antibiotics by enriching Nakamurella and Lacunisphaera. These findings proved that AMF-C. indica MVFCW was a promising system, and the inoculation of AMF effectively enhanced the simultaneous removal of compound pollution.

Deciphering the Role of WWTPs in Cold Environments as Hotspots for the Dissemination of Antibiotic Resistance Genes

Cold environments are the most widespread extreme habitats in the world. However, the role of wastewater treatment plants (WWTPs) in the cryosphere as hotspots in antibiotic resistance dissemination has not been well established. Hence, a snapshot of the resistomes of WWTPs in cold environments, below 5 °C, was provided to elucidate their role in disseminating antibiotic resistance genes (ARGs) to the receiving waterbodies. The resistomes of two natural environments from the cold biosphere were also determined. Quantitative PCR analysis of the aadA, aadB, ampC, blaSHV, blaTEM, dfrA1, ermB, fosA, mecA, qnrS, and tetA(A) genes indicated strong prevalences of these genetic determinants in the selected environments, except for the mecA gene, which was not found in any of the samples. Notably, high abundances of the aadA, ermB, and tetA(A) genes were found in the influents and activated sludge, highlighting that WWTPs of the cryosphere are critical hotspots for disseminating ARGs, potentially worsening the resistance of bacteria to some of the most commonly prescribed antibiotics. Besides, the samples from non-disturbed cold environments had large quantities of ARGs, although their ARG profiles were highly dissimilar. Hence, the high prevalences of ARGs lend support to the fact that antibiotic resistance is a common issue worldwide, including environmentally fragile cold ecosystems.

Does quorum quenching matter to microbial community dynamics in long-term membrane bioreactor operation?

Quorum quenching (QQ) has effectively prevented biofouling in membrane bioreactors (MBRs) employing isolated QQ bacterial strains. However, the influence of QQ on the microbial population still needs to be fully understood. This research aims to analyze the microbial population in MBRs over an extended period (>250 days) under different conditions, such as varying aeration intensities and doses of QQ bacteria, QQ media, and types of feed. Results show that no significant changes occurred in the structure and diversity of the microbial community in the mixed liquor and biofilm due to QQ treatment. Canonical correspondence analysis did reveal that the microbial communities were strongly influenced by feed types and phases. The microbial community composition varied between bacterial habitats (i.e., mixed liquor and biofilm), showing the two dominant phyla Proteobacteria and Bacteroidota in the former and Proteobacteria and Chloroflexi in the latter. The co-occurrence network analysis indicated that the biofilm (with 163 edges) in the MBR fed with real wastewater exhibited a more intricate network than the biofilm (with 53 edges) in the MBR fed with synthetic wastewater. With QQ, the biofilm exhibited more positive edges than negative ones. The phylogenetic investigation of communities showed that QQ barely affects functional gene-related quorum sensing (e.g., bacterial chemotaxis, motility proteins, and secretion) in mixed liquor but in biofilms at relatively large QQ doses (> 75 mg/L BH4). This research sheds light on the bacterial QQ's role in reducing MBR biofouling and provides crucial insights into its underlying mechanisms.

Shotgun Metagenomic Analyses of Microbial Assemblages in the Aquatic Ecosystem of Winam Gulf of Lake Victoria, Kenya Reveals Multiclass Pollution

Lake Victoria, the second-largest freshwater lake in the world, provides an important source of food and income, particularly fish for both domestic consumption and for export market. In recent years, Lake Victoria has suffered massive pollution from both industrial and wastewater discharge. Microplastic biomes, pharmaceutical residues, drugs of abuse, heavy metals, agrochemicals, and personal care products are ubiquitous in the aquatic ecosystem of Winam Gulf. These pollutants are known to alter microbial assemblages in aquatic ecosystems with far-reaching ramification including a calamitous consequence to human health. Indeed, some of these pollutants have been associated with human cancers and antimicrobial resistance. There is a paucity of data on the microbial profiles of this important but heavily polluted aquatic ecosystem. The current study sought to investigate the metagenomic profiles of microbial assemblages in the Winam Gulf ecosystem. Water and sediment samples were collected from several locations within the study sites. Total genomic DNA pooled from all sampling sites was extracted and analyzed by whole-genome shotgun sequencing. Analyses revealed three major kingdoms: bacteria, archaea and eukaryotes belonging to 3 phyla, 13 classes, 14 families, 9 orders, 14 genera, and 10 species. Proteobacteria, Betaproteobacteria, Comamonadaceae, Burkholdariales, and Arcobacter were the dominated phyla, class, family, order, genera, and species, respectively. The Kyoto Encyclopedia of Genes and Genomes indicated the highest number of genes involved in metabolism. The presence of carbohydrate metabolism genes and enzymes was used to infer organic pollutions from sewage and agricultural runoffs. Similarly, the presence of xylene and nutrotoluene degradation genes and enzyme was used to infer industrial pollution into the lake. Drug metabolism genes lend credence to the possibility of pharmaceutical pollutants in water. Taken together, there is a clear indication of massive pollution. In addition, carbohydrate-active enzymes were the most abundant and included genes in glycoside hydrolases. Shotgun metagenomic analyses conveyed an understanding of the microbial communities of the massively polluted aquatic ecosystem of Winam Gulf, Lake Vicoria, Kenya. The current study documents the presence of multiclass pollutants in Lake Victoria and reveals information that might be useful for a potential bioremediation strategy using the native microbial communities.

Graphene nano zinc oxide reduces the expression and release of antibiotic resistance-related genes and virulence factors in animal manure

Animal manure contains many antibiotic resistance genes (ARGs) and virulence factors (VFs), posing significant health threats to humans. However, the effects of graphene nano zinc oxide (GZnONP), a zinc bioaugmentation substitute, on bacterial chemotaxis, ARGs, and VFs in animal manure remain scanty. Herein, the effect of GZnONP on the in vivo anaerobic expression of ARGs and VFs in cattle manure was assessed using high-throughput sequencing. Results showed that GZnONP inhibited bacterial chemotaxis by reducing the zinc pressure under anaerobic fermentation, altering the microbial community structure. The expression of ARGs was significantly lower in GZnONP than in zinc oxide and nano zinc oxide (ZnONP) groups. The expression of VFs was lower in the GZnONP than in the zinc oxide and ZnONP groups by 9.85 % and 13.46 %, respectively. Co-occurrence network analysis revealed that ARGs and VFs were expressed by the Spirochaetes phylum, Paraprevotella genus, and Treponema genus et al. The ARGs-VFs coexistence was related to the expression/abundance of ARGs and VFs genes. GZnONP reduces the abundance of certain bacterial species by disrupting chemotaxis, minimizing the transfer of ARGs and VFs. These findings suggest that GZnONP, a bacterial chemotaxis suppressor, effectively reduces the expression and release of ARGs and VFs in animal manure.

Microbial inoculants enhance the persistence of antibiotic resistance genes in aerobic compost of food waste mainly by altering interspecific relationships

The effects of microbial inoculants on ARG removal in composting are poorly understood. Here, a co-composting method for food waste and sawdust amended with different microbial agents (MAs) was designed. The results show that the compost without MA unexpectedly achieved the best ARG removal. The addition of MAs markedly increased the abundance of tet, sul and multidrug resistance genes (p < 0.05). Structural equation modeling demonstrated that MAs can enhance the contribution of the microbial community to ARG changes by reshaping community structure and altering the ecological niche, causing the proliferation of individual ARGs, an effect related to the MA component. Network analysis revealed that inoculants weakened the correlation between ARGs and community but increased the linkage between ARGs and core species, suggesting that inoculant-induced ARG proliferation may correspond with gene exchange occurring mainly between core species. The outcome provides new insights into MA application for ARG removal in waste treatment.

Potamogeton crispus restoration increased the epiphytic microbial diversity and improved water quality in a micro-polluted urban river

Special characterization and assembly of epiphytic microbial communities remain unclear in micro-polluted water column during submersed macrophytes restoration. In this study, an in-situ enclosure area sowing with turions of Potamogeton crispus (P. crispus) was conducted in a micro-polluted urban river to investigate the characterization of P. crispus and epiphytic microbial communities and their response to water environment under different water depths. Turions completely germinated in water column with <90 cm water depth and the germination speed decreased with increasing water depth within 18 days. There were obvious differences in morphological characteristics of P. crispus between deep and shallow water layers. P. crispus restoration decreased by 12-32%, 13-36%, 9-43% and 5-36% of COD, NH₄⁺-N, TN and TP concentration, respectively, in enclosed overlying water compared to the river (P < 0.05) during 5 months of experiment. Illumina sequencing was employed to explore the epiphytic bacterial and microeukayotic communities at water depth 25-35 cm (shallow area) and 80-90 cm (deep area). A total of 9 bacterial and 12 microeukayotic dominant phyla were obtained in eight samples. It should be noted that the algae abundances were higher in shallow area than deep area but a reverse trend was observed for methanotrophs. Null model analysis revealed that dispersal limitation and undominated process was the most important assembly process, whereas stochastic processes gained more importance in shallow area than deep one. According to cooccurrence analysis (|r| > 0.6, P < 0.05), there were more strongly correlated edges in shallow area (456 edges) than deep area (340 edges). These results highlight that submerged macrophytes restoration can increase microbial diversity and improve water quality, and provide a "summer disease cured in winter" way by using could-resistant P. crispus for water purification in micro-polluted rivers in low-temperature season.

Impact of different organic matters on the occurrence of antibiotic resistance genes in activated sludge

The occurrence of antibiotic resistance genes (ARGs) in various environments has drawn worldwide attention due to their potential risks. Previous studies have reported that a variety of substances can enhance the occurrence and dissemination of ARGs. However, few studies have compared the response of ARGs under the stress of different organic matters in biological wastewater treatment systems. In this study, seven organic pollutants were added into wastewater treatment bioreactors to investigate their impacts on the ARG occurrence in activated sludge. Based on high-throughput sequencing, it was found that the microbial communities and ARG patterns were significantly changed in the activated sludge exposed to these organic pollutants. Compared with the non-antibiotic refractory organic matters, antibiotics not only increased the abundance of ARGs but also significantly changed the ARG compositions. The increase of Gram-negative bacteria (e.g., Archangium, Prosthecobacter and Dokdonella) carrying ARGs could be the main cause of ARG proliferation. In addition, significant co-occurrence relationships between ARGs and mobile genetic elements were also observed in the sludge samples, which may also affect the ARG diversity and abundance during the organic matter treatment in the bioreactors. Overall, these findings provide new information for better understanding the ARG occurrence and dissemination caused by organic pollutants in wastewater treatment systems.

Biofilter-constructed wetland-trophic pond system: A new strategy for effective sewage treatment and agricultural irrigation in rural area

Artificial ecosystems with high biological complexity are generally considered to be efficient in metabolizing substances and resistant to temperature shock. In this study, a novel near-natural system (BCT system), which consisted of simple biofilter, constructed wetland and trophic biology pond, was conducted to treat rural sewage in situ for irrigation into farmland. Water quality related to carbon and nutrients and microbial community were analyzed along the system to reveal the effect of each unit. The annual average removals of BCT system for TN, NH₄⁺-N, TP and COD could reach 46.53%, 52.18%, 41.48%, and 53.21%, respectively. There was no significant decrease for removal efficiencies from high temperature period (HTP, ≥15 °C) to low temperature period (LTP, <15 °C). In LTP, the trophic pond (TRP) removed 34.85% of TN, 33.93% of NH₄⁺-N, 13.71% of TP and 18.77% of COD, while the removal efficiencies of constructed wetland fluctuated greatly. The TRP facilitated the BCT system to maintain the removal capability during low temperature period. The relative abundance of denitrification functional genes in TRP increased nearly tenfold from HTP to LTP. The effluent quality from the system can meet the agricultural irrigation standards, demonstrating the effect of BCT system on sewage treatment and agricultural irrigation in rural area.

Different microplastics distinctively enriched the antibiotic resistance genes in anaerobic sludge digestion through shifting specific hosts and promoting horizontal gene flow

Both microplastics (MPs) and antibiotic resistance genes (ARGs) are intensively detected in waste activated sludge (WAS). However, the distinctive impacts of different MPs on ARGs emergence, dissemination, and its potential mechanisms remain unclear. In this study, long-term semi-continuous digesters were performed to examine the profiles of ARGs and antibiotic-resistant bacteria (ARB) in response to two different typical MPs (polyethylene (PE) and polyvinyl chloride (PVC)) in anaerobic sludge digestion. Metagenomic results show that PE- and PVC-MPs increase ARGs abundance by 14.8% and 23.6% in digester, respectively. ARB are also enriched by PE- and PVC-MPs, Acinetobacter sp. and Salmonella sp. are the dominant ARB. Further exploration reveals that PVC-MPs stimulates the acquisition of ARGs by human pathogen bacteria (HPB) and functional microorganisms (FMs), but PE-MPs doesn't. Network analysis shows that more ARGs tend to co-occur with HBP and FMs after MPs exposure, and more importantly, new bacteria are observed to acquire ARGs possibly via horizontal gene flow (HGF) in MPs-stressed digester. The genes involved in the HGF process, including reactive oxygen species (ROS) production, cell membrane permeability, extracellular polymeric substances (EPS) secretion, and ATP synthesis, are also enhanced by MPs, thereby attributing to the promoted ARGs dissemination. These findings offer advanced insights into the distinctive contribution of MPs to fate, host, dissemination of ARGs in anaerobic sludge digestion.

Watershed urbanization enhances the enrichment of pathogenic bacteria and antibiotic resistance genes on microplastics in the water environment

Microplastics (MPs) serve as vectors for microorganisms and antibiotic resistance genes (ARGs) and contribute to the spread of pathogenic bacteria and ARGs across various environments. Patterns of microbial communities and ARGs in the biofilm on the surface of MPs, also termed as plastisphere, have become an issue of global concern. Although antibiotic resistome in the plastisphere has been detected, how watershed urbanization affects patterns of potential pathogens and ARGs in the microplastic biofilms is still unclear. Here, we compared the bacterial communities, the interaction between bacterial taxa, pathogenic bacteria, and ARGs between the plastisphere and their surrounding water, and revealed the extensive influence of urbanization on them. Our results showed that bacterial communities and interactions in the plastisphere differed from those in their surrounding water. Microplastics selectively enriched Bacteroidetes from water. In non-urbanized area, the abundance of Oxyphotobacteria was significantly (p < 0.05) higher in plastisphere than that in water, while α-Proteobacteria was significantly (p < 0.05) higher in plastisphere than those in water of urbanized area. Pathogenic bacteria, ARGs, and mobile genetic elements (MGEs) were significantly (p < 0.05) higher in the urbanized area than those in non-urbanized area. MPs selectively enriched ARG-carrying potential pathogens, i.e., Klebsiella pneumoniae and Enterobacter cloacae, and exhibited a distinct effect on the relative abundance of ARG and pathogens in water with different urbanization levels. We further found ARGs were significantly correlated to MGEs and pathogenic bacteria. These results suggested that MPs would promote the dissemination of ARGs among microbes including pathogenic bacteria, and urbanization would affect the impact of MPs on microbes, pathogens, and ARGs in water. A high level of urbanization could enhance the enrichment of pathogens and ARGs by MPs in aquatic systems and increase microbial risk in aquatic environments. Our findings highlighted the necessity of controlling the spread of ARGs among pathogens and the usage of plastic products in ecosystems of urban areas.

Performance of various fillers in ecological floating beds planted with Myriophyllum aquaticum treating municipal wastewater

The performance of different suspended fillers (zeolite, drinking water treatment residual, biochar, woodchip and stereo-elastic packing) and their combinations in treating municipal wastewater in ecological floating beds (Eco-FBs) planted with Myriophyllum aquaticum was assessed. Six sets of enhanced Eco-FBs were developed to assess the individual and synergistic effects of combinations of the various fillers and microorganisms on nutrient elimination. The results demonstrated mean TN, NH₄-N, TP and COD purification efficiencies of 99.2 ± 11.2 %, 99.82 ± 16.4 %, 98.3 ± 14.3 %, and 96.1 ± 12.3 %, respectively in the Eco-FBs strengthened with all five fillers. The corresponding purification rates were 0.89 ± 0.14, 0.75 ± 0.12, 0.08 ± 0.016, and 7.05 ± 1.09 g m^-2 d^-1, which were 2-3 times higher than those of the conventional Eco-FB system. High-throughput sequencing showed that some genera related to nutrient transformation, including Proteobacteria (24.13-51.95 %), followed by Chloroflexi (5.64-25.01 %), Planctomycetes (8.48-14.43 %) and Acidobacteria (2.29-11.65 %), were abundantly enriched in the strengthened Eco-FBs. Enhancement of the Eco-FBs with various fillers significantly increased microbial species richness and diversity as demonstrated by Chao1, Shannon and Simpson's indexes, particularly when all the five fillers were combined. Therefore, introducing suspended fillers into Eco-FBs is an appropriate approach for improving nutrient elimination from municipal wastewater.

Exposure to Veterinary Antibiotics via Food Chain Disrupts Gut Microbiota and Drives Increased Escherichia coli Virulence and Drug Resistance in Young Adults

Exposure to veterinary antibiotics (VAs) and preferred as veterinary antibiotics (PVAs) via the food chain is unavoidable for their extensive use not only for treating bacterial infections, but also for use as growth promoters in livestock and aquaculture. One of the consequences is the disturbance of gut microbiota. However, its impact on the virulence and drug resistance of opportunistic pathogens is still unclear. In this study, a total of 26 antibiotics were detected in the urine of 300 young undergraduates in Anhui Province. We found that excessive intake of milk was positively correlated to high levels of VAs and PVAs. It led to the dysbiosis of gut microbiota characterized by high abundance of Bacteroidetes and Proteobacteria. The increase in Proteobacteria was mainly due to a single operational taxonomic unit (OTU) of Escherichia coli (E. coli). We isolated several E. coli strains from participants and compared their drug resistance and virulence using PCR assay and virulence-related assays. We observed that exposure to high levels of VAs and PVAs induced more resistant genes and drove E. coli strain to become more virulent. At last, we conducted transcriptome analysis to investigate the molecular mechanism of virulent and drug-resistant regulators in the highly virulent E. coli strain. We noted that there were multiple pathways involved in the drug resistance and virulence of the highly virulent strain. Our results demonstrated that participants with high-level VAs and PVAs exposure have a disrupted gut microbiota following the appearance of highly drug-resistant and virulent E. coli and, therefore may be at elevated risk for long-term health complications.

Developing an Efficient Processing System Treatment for the High Concentration of Eucalyptus Chemical Mechanical Pulp Wastewater

The current wastewater treatment method shows low efficiency in treating wastewater with high concentrations of chemical mechanical pulp (CMP). Therefore, a chlorine dioxide Pretreatment Anaerobic Treatment (DPAT) was developed and applied to treat the CMP wastewater to obtain higher efficiency, obtaining the following results: The biodegradability of CMP wastewater improved after chlorine dioxide pretreatment. The COD of wastewater treated with chlorine dioxide was reduced from 5634 mg/L to 660 mg/L. The removal rate for chemical oxygen demand (COD) was 88.29%, 29.13% higher than the common anaerobic treatment. The reasons for the high efficiency of the DPAT treatment were that chlorine dioxide pretreatment removed the toxic substances in the original wastewater and thereby promoted the proliferation and growth of the anaerobe. The results show that pretreatment with chlorine dioxide can effectively enhance the biodegradability of high-concentration CMP wastewater. Therefore, DPAT treatment of high-concentration CMP wastewater is beneficial to environmental protection.

The Resistome of ESKAPEE Pathogens in Untreated and Treated Wastewater: A Polish Case Study

The aim of this study was to quantify ESKAPEE bacteria, genes encoding resistance to antibiotics targeting this group of pathogens, as well as integrase genes in municipal wastewater and river water. Environmental DNA was extracted from the collected samples and used in deep sequencing with the Illumina TruSeq kit. The abundance of bacterial genera and species belonging to the ESKAPEE group, 400 ARGs associated with this microbial group, and three classes of integrase genes were determined. A taxonomic analysis revealed that Acinetobacter was the dominant bacterial genus, whereas Acinetobacter baumannii and Escherichia coli were the dominant bacterial species. The analyzed samples were characterized by the highest concentrations of the following ARGs: bla_GES, bla_OXA-58, bla_TEM, qnrB, and qnrS. Acinetobacter baumannii, E. coli, and genes encoding resistance to β-lactams (bla_VEB-1, bla_IMP-1, bla_GES, bla_OXA-58, bla_CTX-M, and bla_TEM) and fluoroquinolones (qnrS) were detected in samples of river water collected downstream from the wastewater discharge point. The correlation analysis revealed a strong relationship between A. baumannii (bacterial species regarded as an emerging human pathogen) and genes encoding resistance to all tested groups of antimicrobials. The transmission of the studied bacteria (in particular A. baumannii) and ARGs to the aquatic environment poses a public health risk.

Current Concentrations of Zn, Cu, and As in Piggery Wastewater Compromise Nutrient Removals in Microalgae–Bacteria Photobioreactors Due to Altered Microbial Communities

Simple Summary

Photobioreactor systems based on consortia of microalgae and bacteria are a promising, efficient and sustainable alternative for treatment of wastewaters with high nitrogen content, such as piggery wastewater. In these biological systems, microorganisms play a key role in wastewater treatment by degradation of organic matter and accumulation of nutrients into the generated biomass. However, these wastewaters often contain high concentrations of zinc, copper and arsenic, which can severely affect the activity and growth of microorganisms, and so, the wastewater treatment performance. This article studies the effect of high concentrations of zinc, copper and arsenic on microbial communities, specifically microalgae and bacteria, in photobioreactors treating piggery wastewater, with the aim of elucidating their impact on wastewater treatment performance. For this purpose, the growth of microalgae and the composition and structure of bacterial communities exposed to these pollutants were studied. The performance of the reactors was also evaluated by determining the removal of nutrients, zinc, copper and arsenic. The results showed that high concentrations of zinc, copper and arsenic in piggery wastewater significantly affect the microbiome of the reactors without recovery after exposure to these contaminants, resulting in poorer performance of the reactors and compromising the environmental and health impact of treated effluents.

Abstract

The treatment of pig manure is a major environmental issue, and photobioreactors containing consortia of microalgae and bacteria have proven to be a promising and sustainable treatment alternative. This work studies the effect of Cu, Zn and As, three toxic elements frequently present in piggery wastewater, on the performance and microbiome of photobioreactors. After dopage with Zn (100 mg/L), Cu (100 mg/L), and As (500 µg/L), the high biomass uptake of Zn (69–81%) and Cu (81–83%) decreased the carbon removal in the photobioreactors, inhibited the growth of Chlorella sp., and affected heterotrophic bacterial populations. The biomass As uptake result was low (19%) and actually promoted microalgae growth. The presence of Cu and As decreased nitrogen removal, reducing the abundance of denitrifying bacterial populations. The results showed that metal(loid)s significantly affected 24 bacterial genera and that they did not recover after exposure. Therefore, this study makes an important contribution on the impact of the presence of metal(loid)s in piggery wastewater that compromises the overall performance of PBRs, and so, the environmental and health impact of treated effluents.

The prevalence and removal of antibiotic resistance genes in full-scale wastewater treatment plants: Bacterial host, influencing factors and correlation with nitrogen metabolic pathway

This study investigated the prevalence of antibiotic resistance genes (ARGs) in the influent, effluent, and waste activated sludge (WAS) of eight full-scale municipal wastewater treatment plants (WWTPs) in Shanghai, China. A comprehensive understanding of the correlation between various influencing factors (characteristics of wastewater and WAS, antibiotics, metals, mobile genetic elements) and ARGs was explored. Among the eight full-scale WWTPs, the Unitank process was inefficient in removing typical ARGs compared with continuous-flow anaerobic-anoxic-aerobic and oxidation ditch processes. Antibiotic was identified as the most influential factor affecting the occurrence of ARGs in wastewater, followed by flow rate and nutrients. Positive correlations were observed between antibiotics and their corresponding ARGs in the influent, while this correlation disappeared in the WAS. Class I integron, wastewater characteristics (nitrogen and flow rate), antibiotics (ofloxacin, sulfamethazine, and erythromycin), metals (Mg, Al, Fe, and Mn) were identified as crucial factors comprehensively affecting the distribution of ARGs in WAS. Dissimilatory nitrate reduction profoundly influenced the fate of ARGs during wastewater treatment processes, and K04561 (norB), K02567 (napA), K00262 (gdhA), K00284 (gltS) were identified as the most significant genes in the nitrogen metabolism pathway (ko00910). This study provides a new perspective for comprehensively understanding the occurrence and dissemination of ARGs in WWTPs.

Nanoselenium integrates soil-pepper plant homeostasis by recruiting rhizosphere-beneficial microbiomes and allocating signaling molecule levels under Cd stress

Most studies have focused on regulation in a metabolic pathway in response to exogenous selenium under cadmium stress, rather than the change of key factors in soil and pepper plants. In this study, the correlations in environmental variables, microorganisms, metabolic pathways, Se and Cd morphology under nano-Se intervention were examined using metabolomics and microbial diversity in rhizosphere soil and pepper plants. The principal forms of Se in the soils were Se (VI) and SeCys, while SeMet and MeSeCys were the main components in the root, stem, leaves, and fruits in the treatment of nano-Se (5 and 20 mg/L) relative to the control. Soil enzymes,metabolites (fluorescein diacetate, urease, brassinolide, and p-hydroxybenzonic acid), and plant metabolites (rutin, luteolin, brassinolide, and abscisic acid) were remarkably enhanced by nano-Se fortification. The bio-enhancement of nano-Se can boost the beneficial microorganisms of Gammaproteobacteria, Alphaproteobacteria, Bacteroidia, Gemmatimonadetes, Deltaproteobacteria, and Anaerolineae in rhizosphere soil. Changes in microbial community were found to be strongly linked to the environment index, enzymes, soil metabolites, Se forms, which reduced Cd bioavailability and Cd accumulation in pepper plants. In conclusion, the nano-Se application integrates soil-plant balance by improving soil qualities and assigning signaling molecule levels in rhizosphere soil and pepper plants.

Development of electrocoagulation process for wastewater treatment: optimization by response surface methodology

Electrocoagulation (EC) is a process used by supply of electric current with sacrificial electrodes for the removal of pollutant from wastewater. The study was experimentally investigated taking into account various factors such as pH (3–7.5), current (0.03–0.09 A), distance between the electrodes (1–2 cm), electrolytic concentration (1–3 g/L), and electrolysis time (20–60 min) which is impact on the % removal efficiency of color, chemical oxygen demand (COD), turbidity and determination of energy consumption used for aluminum (Al) electrode used. The surface response design process based on the central composite design (CCD) has been used to optimize different operational parameters for treatment of hospital wastewater using EC process. The % color, COD and turbidity removal, and energy consumption under different conditions were predicted with the aid of a quadratic model, as were the significance and their interaction with independent variables assessed by analysis of variance (ANOVA). The optimal conditions were obtained through mathematical and statistical methods to reach maximum % color, COD, and turbidity removal with minimum energy consumption. The results showed that the maximum removal of color (92.30%), COD (95.28%), and turbidity (83.33%) were achieved at pH–7.5, current–0.09A, electrolytic concentration–3g/L, distance between electrodes–2 cm and reaction time 60 min. This means that, the process of EC can remove pollutants from various types of wastewaters and industrial effluent under the various operating parameters.

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EC effective technology used to treat wastewater generated from hospital.

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Al was used as an electrode for hospital wastewater treatment using EC process.

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EC can eliminate pollutants from wastewater under various operating parameters.

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CCD used to optimize operational parameters for treatment of hospital wastewater.

Metagenomic Analysis of the Long-Term Synergistic Effects of Antibiotics on the Anaerobic Digestion of Cattle Manure

The conversion of cattle manure into biogas in anaerobic digestion (AD) processes has been gaining attention in recent years. However, antibiotic consumption continues to increase worldwide, which is why antimicrobial concentrations can be expected to rise in cattle manure and in digestate. This study examined the long-term synergistic effects of antimicrobials on the anaerobic digestion of cattle manure. The prevalence of antibiotic resistance genes (ARGs) and changes in microbial biodiversity under exposure to the tested drugs was investigated using a metagenomic approach. Methane production was analyzed in lab-scale anaerobic bioreactors. Bacteroidetes, Firmicutes, and Actinobacteria were the most abundant bacteria in the samples. The domain Archaea was represented mainly by methanogenic genera Methanothrix and Methanosarcina and the order Methanomassiliicoccales. Exposure to antibiotics inhibited the growth and development of methanogenic microorganisms in the substrate. Antibiotics also influenced the abundance and prevalence of ARGs in samples. Seventeen types of ARGs were identified and classified. Genes encoding resistance to tetracyclines, macrolide–lincosamide–streptogramin antibiotics, and aminoglycosides, as well as multi-drug resistance genes, were most abundant. Antibiotics affected homoacetogenic bacteria and methanogens, and decreased the production of CH4. However, the antibiotic-induced decrease in CH4 production was minimized in the presence of highly drug-resistant microorganisms in AD bioreactors.

Analysis of the Bacterial Biocenosis of Activated Sludge Treated with Leachate from Municipal Landfills

The influx of toxic pollutants into wastewater treatment plants can negatively affect the quality of the activated sludge (AS). One source is landfill leachate. The identification of microorganisms present in AS is very important, e.g., while improving wastewater treatment technology. Therefore, the aim of the study was to investigate the effect of raw leachate and after purification of Phragmites australis and Ceratophyllum demersum on the composition of the AS bacterial biocenosis. In addition, AS status was assessed by LIVE/DEAD BacLight ™ fluorescent staining. The obtained results showed that the leachate did not significantly affect the cell membranes of AS bacteria, and even a slight improvement was noted. The research carried out using the next-generation sequencing method shows that the origin of the samples (active and closed storage) and the method of processing do not significantly affect the composition of the AS bacterial biocenosis at higher taxonomic levels. However, at the species level, the appearance of bacteria not previously present in AS was observed, namely: Flavobacterium luticocti, Candidimonas nitroreducens and Nitrobacter hamburgensis. The obtained results suggest that the leachate may be a source of microorganisms positively influencing the condition of AS bacteria.

Diversity, Functions and Antibiotic Resistance of Sediment Microbial Communities From Lake Geneva Are Driven by the Spatial Distribution of Anthropogenic Contamination

Lake sediments are natural receptors for a wide range of anthropogenic contaminants including organic matter and toxicants such as trace metals, polycyclic aromatic hydrocarbons, polychlorinated biphenyls that accumulate over time. This contamination can impact benthic communities, including microorganisms which play a crucial role in biogeochemical cycling and food-webs. The present survey aimed at exploring whether anthropogenic contamination, at a large lake scale, can influence the diversity, structure and functions of microbial communities associated to surface sediment, as well as their genetic potential for resistance to metals and antibiotics. Changes in the characteristics of these communities were assessed in surface sediments collected in Lake Geneva from eight sampling sites in October 2017 and May 2018. These sampling sites were characterized by a large concentration range of metal and organic compound contamination. Variation between the two sampling periods were very limited for all sampling sites and measured microbial parameters. In contrast, spatial variations were observed, with two sites being distinct from each other, and from the other six sites. Benthic communities from the most contaminated sampling site (Vidy Bay, near the city of Lausanne) were characterized by the lowest bacterial and archaeal diversity, a distinct community composition, the highest abundance of antibiotic resistance genes and functional (respiration, denitrification, methanogenesis, phosphatase, and beta-glucosidase) activity levels. The second sampling site which is highly influenced by inputs from the Rhône River, exhibited low levels of diversity, a distinct community composition, high abundance of antibiotic resistance genes and the highest bacterial abundance. Overall, our results suggest that local anthropogenic contamination, including organic matter and toxicants, is a major driver of the diversity and functioning of sediment-microbial communities in Lake Geneva. This highlights the need to consider benthic microbial communities and a suite of complementary ecotoxicological endpoints for more effective environmental risk assessments of contaminants in lake sediments.

Shotgun metagenomic analysis reveals the prevalence of antibiotic resistance genes and mobile genetic elements in full scale hospital wastewater treatment plants

Wastewater treatment plants are considered as hotspots of emerging antimicrobial genes and mobile genetic elements. We used a shotgun metagenomic approach to examine the wide-spectrum profiles of ARGs (antibiotic resistance genes) and MGEs (mobile genetic elements) in activated sludge samples from two different hospital trains at the wastewater treatment plants (WWTPs) in Daegu, South Korea. The influent activated sludge and effluent of two trains (six samples in total) at WWTPs receiving domestic sewage wastewater (SWW) and hospital wastewater (HWW) samples collected at multiple periods were subjected to high throughput 16S rRNA metagenome sequencing for microbial community diversity. Cloacibacterium caeni and Lewinella nigricans were predominant in SWW effluents, while Bacillus subtilis and Staphylococcus epidermidis were predominant in HWW effluents based on the Miseq platform. Totally, 20,011 reads and 28,545 metagenomic sequence reads were assigned to 25 known ARG types in the SWW2 and HWW5 samples, respectively. The higher abundance of ARGs, including multidrug resistance (>53%, MDR), macrolide-lincosamide-streptogramin (>9%, MLS), beta-lactam (>3.3%), bacitracin (>4.4%), and tetracycline (>3.4%), confirmed the use of these antibiotics in human medicine. In total, 190 subtypes belonging to 23 antibiotic classes were detected in both SWW2 and HWW5 samples. RpoB2, MacB, and multidrug (MDR) ABC transporter shared the maximum matched genes in both activated sludge samples. The high abundance of MGEs, such as a gene transfer agent (GTA) (four times higher), transposable elements (1.6 times higher), plasmid related functions (3.8 times higher), and phages (two times higher) in HWW5 than in SWW2, revealed a risk of horizontal gene transfer in HWW. Domestic wastewater from hospital patients also influenced the abundance of ARGs and MGEs in the activated sludge process.

Bacterial Community Structure and Dynamic Changes in Different Functional Areas of a Piggery Wastewater Treatment System

Chemicals of emerging concern (CEC) in pig farm breeding wastewater, such as antibiotics, will soon pose a serious threat to public health. It is therefore essential to consider improving the treatment efficiency of piggery wastewater in terms of microorganisms. In order to optimize the overall piggery wastewater treatment system from the perspective of the bacterial community structure and its response to environmental factors, five samples were randomly taken from each area of a piggery’s wastewater treatment system using a random sampling method. The bacterial communities’ composition and their correlation with wastewater quality were then analyzed using Illumina MiSeq high-throughput sequencing. The results showed that the bacterial community composition of each treatment unit was similar. However, differences in abundance were significant, and the bacterial community structure gradually changed with the process. Proteobacteria showed more adaptability to an anaerobic environment than Firmicutes, and the abundance of Tissierella in anaerobic zones was low. The abundance of Clostridial (39.02%) and Bacteroides (20.6%) in the inlet was significantly higher than it was in the aerobic zone and the anoxic zone (p < 0.05). Rhodocyclaceae is a key functional microbial group in a wastewater treatment system, and it is a dominant microbial group in activated sludge. Redundancy analysis (RDA) showed that chemical oxygen demand (COD) had the greatest impact on bacterial community structure. Total phosphorus (TP), total nitrogen (TN), PH and COD contents were significantly negatively correlated with Sphingobacteriia, Betaproteobacteria and Gammaproteobacteria, and significantly positively correlated with Bacteroidia and Clostridia. These results offer basic data and theoretical support for optimizing livestock wastewater treatment systems using bacterial community structures.

Development of autotrophic and heterotrophic consortia via immobilized microbial beads for chemical wastewater treatment, using PTA wastewater as an approach

Studies on the symbiosis of microalgae-bacteria have been accelerating as a mean for wastewater remediation. However, there were few reports about the microalgae-bacteria consortia for chemical wastewater treatment. The aim of the present study is to develop an autotrophic and heterotrophic consortium for chemical wastewater treatment and probe whether and how bacteria could benefit from the microalgae during the treatment process, using PTA wastewater as an approach. A process-dependent strategy was applied. First of all, the results showed that the sludge beads with the sludge concentration of 30 g/L were the optimal one with the COD removal rate at 84.8% but the ceiling effect occurred (COD removal rate < 90%) even several common reinforcement methods were applied. Additionally, by adding the microalgae Chlorella vulgaris, a microalgae-activated sludge consortium was formed inside the immobilized beads, which provided better performance to shatter the ceiling effect. The COD remove rate was higher than 90%, regardless of the activated sludge was pre-culture or not. COD removal capacity could also be improved (COD removal rate > 92%) when LEDs light belt was offered as an advanced light condition. Biochemical assay and DNA analysis indicated that the microalgae could form an internal circulation of substances within the activated sludge and drove the microbial community to success and the corresponding gene functions, like metabolism and.

Metagenomic analysis of microbial communities in the sediments of a semi-intensive penaeid shrimp culture system

The present study reports metagenomic sequencing and microbial diversity analysis of the sediment samples of a semi-intensive penaeid shrimp culture system. 16S rRNA gene-based high-throughput sequencing revealed distinct and diverse microbial communities in the analyzed sample. Analysis of the results showed a high abundance of Proteobacteria followed by Verrucomicrobia, Bacteroidetes, Planctomycetes, Firmicutes, Cyanobacteria, and Actinobacteria in the metagenome retrieved from the sediment sample. Unclassified bacteria also contributed a significant portion of the metagenome. Two potential shrimp pathogens viz Vibrio harveyi and Acinetobacter lwoffii detected in the sediment sample show the risk associated with the pond. Microbes that play essential roles in nutrient cycling and mineralization of organic compounds such as Bacteroidetes, Planctomycetes, Gammaproteobacteria, Firmicutes, Cyanobacteria, and Actinobacteria could also be identified. The present study provides preliminary data with respect to the microbial community present in the sediments of a shrimp culture system and emphasizes the application of metagenomics in exploring the microbial diversity of aquaculture systems, which might help in the early detection of pathogens within the system and helps to develop pathogen control strategies in semi-intensive aquaculture systems.

Taxonomic and Functional Distribution of Bacterial Communities in Domestic and Hospital Wastewater System: Implications for Public and Environmental Health

The discharge of untreated hospital and domestic wastewater into receiving water bodies is still a prevalent practice in developing countries. Unfortunately, because of an ever-increasing population of people who are perennially under medication, these wastewaters contain residues of antibiotics and other antimicrobials as well as microbial shedding, the direct and indirect effects of which include the dissemination of antibiotic resistance genes and an increase in the evolution of antibiotic-resistant bacteria that pose a threat to public and environmental health. This study assessed the taxonomic and functional profiles of bacterial communities, as well as the antibiotic concentrations in untreated domestic wastewater (DWW) and hospital wastewater (HWW), using high-throughput sequencing analysis and solid-phase extraction coupled to Ultra-high-performance liquid chromatography Mass Spectrometry (UHPLC–MS/MS) analysis, respectively. The physicochemical qualities of both wastewater systems were also determined. The mean concentration of antibiotics and the concentrations of Cl⁻, F⁻ and PO₄³ were higher in HWW samples than in DWW samples. The phylum Firmicutes was dominant in DWW with a sequence coverage of 59.61% while Proteobacteria was dominant in HWW samples with a sequence coverage of 86.32%. At genus level, the genus Exiguobacterium (20.65%) and Roseomonas (67.41%) were predominant in DWW and HWW samples, respectively. Several pathogenic or opportunistic bacterial genera were detected in HWW (Enterococcus, Pseudomonas and Vibrio) and DWW (Clostridium, Klebsiella, Corynebacterium, Bordetella, Staphylocccus and Rhodococcus) samples. Functional prediction analysis indicated the presence of beta-lactam resistance, cationic antimicrobial peptide (CAMP) resistance and vancomycin resistance genes in HWW samples. The presence of these antibiotic resistance genes and cassettes were positively correlated with the presence of pathogens. These findings show the risk posed to public and environmental health by the discharge of untreated domestic and hospital wastewaters into environmental water bodies.

Pilot-scale two-stage constructed wetlands based on novel solid carbon for rural wastewater treatment in southern China: Enhanced nitrogen removal and mechanism

Constructed wetlands (CWs) have been proved to be an alternative to the treatment of various wastewater. However, there are few studies focused on the removal performance and mechanisms of pollutants in pilot-scale CWs packed with novel solid carbon. In this study, we investigated the effect of poly-3-hydroxybutyrate-co-3-hydroxyvalerate/polyacetic acid (PHBV/PLA) blends as carbon source on pollutant's transformation, microbial communities and functional genes in pilot-scale aeration-anoxic two-stage CWs for polishing rural runoff in southern China. Results showed a striking improvement of TN removal in CWs with PHBV/PLA blends (64.5%) compared to that in CWs with ceramsite (52.9%). NH₄⁺-N (61.3-64.6%), COD (40.4-53.8%) and TP (43.6-47.1%) were also removed effectively in both two CWs. In addition, the strains of Rhodocyclaceae and Bacteroidetes were the primary denitrifiers on the surface of PHBV/PLA blends. Further, the aerobic stage induced gathering of 16 S and amoA genes and the anoxic zone with PHBV/PLA blends increased the nirS genes, which fundamentally explained the better denitrification performance in CW based on PHBV/PLA blends. Consequently, this study will provide straightforward guidance for the operation of engineering CWs packed with polymers to govern the low-C/N rural wastewater.

The impact of antimicrobials on the efficiency of methane fermentation of sewage sludge, changes in microbial biodiversity and the spread of antibiotic resistance

The study was designed to simultaneously evaluate the influence of high doses (512-1024 µg/g) the most commonly prescribed antimicrobials on the efficiency of anaerobic digestion of sewage sludge, qualitative and quantitative changes in microbial consortia responsible for the fermentation process, the presence of methanogenic microorganisms, and the fate of antibiotic resistance genes (ARGs). The efficiency of antibiotic degradation during anaerobic treatment was also determined. Metronidazole, amoxicillin and ciprofloxacin exerted the greatest effect on methane fermentation by decreasing its efficiency. Metronidazole, amoxicillin, cefuroxime and sulfamethoxazole were degraded in 100%, whereas ciprofloxacin and nalidixic acid were least susceptible to degradation. The most extensive changes in the structure of digestate microbiota were observed in sewage sludge exposed to metronidazole, where a decrease in the percentage of bacteria of the phylum Bacteroidetes led to an increase in the proportions of bacteria of the phyla Firmicutes and Proteobacteria. The results of the analysis examining changes in the concentration of the functional methanogen gene (mcrA) did not reflect the actual efficiency of methane fermentation. In sewage sludge exposed to antimicrobials, a significant increase was noted in the concentrations of β-lactam, tetracycline and fluoroquinolone ARGs and integrase genes, but selective pressure was not specific to the corresponding ARGs.

Polystyrene microplastics alleviate the effects of sulfamethazine on soil microbial communities at different CO2 concentrations

Microplastics were reported to adsorb antibiotics and may modify their effects on soil systems. But there has been little research investigating how microplastics may affect the toxicities of antibiotics to microbes under future climate conditions. Here, we used a free-air CO₂ enrichment system to investigate the responses of soil microbes to sulfamethazine (SMZ, 1 mg kg^-1) in the presence of polystyrene microplastics (PS, 5 mg kg^-1) at different CO₂ concentrations (ambient at 380 ppm and elevated at 580 ppm). SMZ alone decreased bacterial diversity, negatively affected the bacterial structure and inter-relationships, and enriched the sulfonamide-resistance genes (sul1 and sul2) and class 1 integron (intl1). PS, at both CO₂ conditions, showed little effect on soil bacteria but markedly alleviated SMZ's adverse effects on bacterial diversity, composition and structure, and inhibited sul1 transmission by decreasing the intl1 abundance. Elevated CO₂ had limited modification in SMZ's disadvantages to microbial communities but markedly decreased the sul1 and sul2 abundance. Results indicated that increasing CO₂ concentration or the presence of PS affected the responses of soil microbes to SMZ, providing new insights into the risk prediction of antibiotics under future climate conditions.

Foam shares antibiotic resistomes and bacterial pathogens with activated sludge in wastewater treatment plants

Foaming is a common operational problem that occurs in activated sludge (AS) from many wastewater treatment plants (WWTPs), but the characteristic of antibiotic resistance genes (ARGs) and human pathogenic bacteria (HPB) in foams is generally lacking. Here, we used a metagenomic approach to characterize the profile of ARGs and HPB in foams and AS from full-scale WWTPs receiving pesticide wastewater. No significant difference in the microbial communities was noted between the AS and foam samples. The diversity and abundance of ARGs in the foams were similar to those in the pertinent AS samples. Procrustes analysis suggested that the bacterial community is the major driver of ARGs. Metagenomic assembly also indicated that most ARGs (e.g., multidrug, rifamycin, peptides, macrolide-lincosamide-streptogramin, tetracycline, fluoroquinolone, and beta-lactam resistance genes) were carried by chromosomes rather than mobile genetic elements. Moreover, the relative abundances of HPB, Pseudomonas putida and Mycobacterium smegmatis, were enriched in the foam samples. Nine HPB were identified as carriers of 21 ARG subtypes, of which Pseudomonas aeruginosa could carry 12 ARG subtypes. Overall, this study indicates the prevalence of ARGs, HPB, and ARG-carrying HPB in foams, which highlights the potential risk of foams in spreading ARGs and HPB into the surrounding environments.

Identification of new eligible indicator organisms for combined sewer overflow via 16S rRNA gene amplicon sequencing in Kanda River, Tokyo

Fecal indicator bacteria (FIB) are commonly used to evaluate the pollution impact of combined sewer overflows (CSOs) in urban rivers. Although water quality assessment with FIB has a long tradition, recent studies demonstrated that FIB have a low correlation with pathogens and therefore are not accurate enough for the assessment of potential human hazards in water. Consequently, new eligible and more specific indicators have to be identified, which was done in this study via sequencing of genetic markers from total community DNA. To identify potential microbiome-based indicators, microbial communities in samples from an urban river in Tokyo under different climatic conditions (dry and rainy) were compared with the influent and effluent of three domestic wastewater treatment plants (WWTPs) by analyzing 16 S rRNA gene amplicon libraries. In the first part of this study, physicochemical parameters and FIB quantification with selective culture techniques facilitated the identification of samples contaminated with CSO, sewage, or both. This allowed the grouping of samples into CSO-contaminated and non-contaminated samples, an essential step prior to the microbiome comparison between samples. Increased turbidity, ammonia concentrations, and E. coli [up to (9.37 ± 0.95) × 10² CFU/mL after 11.5 mm of rainfall] were observed in CSO-contaminated river samples. Comparison of dry weather (including WWTP samples) and rainy weather samples showed a reduction in microbial diversity in CSO-contaminated samples. Furthermore, the results of this study suggest Bacteroides spp. as a novel indicator of sewage pollution in surface waters.

Degradation of chlorine dioxide bleaching wastewater and response of bacterial community in the intimately coupled system of visible-light photocatalysis and biodegradation

Intimate coupling of visible-light photocatalysis and biodegradation (ICPB) offers potential for degrading chlorine dioxide bleaching wastewater. In this study, we reported a TiO₂-coated sponge biofilm carrier with significant adhesion of TiO₂ and the ability to accumulate biomass in its interior. Four mechanisms possibly acting in ICPB were tested separately: adsorption of chlorine dioxide bleaching wastewater to the carrier, photolysis, photocatalysis, and biodegradation by the biofilm inside the carrier. The carrier had an adsorption capacity of 17% and 16% for CODcr and AOX, respectively, in the wastewater. The photodegradation rate of wastewater was very low and could be ignored. Both biodegradation (AOX 30.1%, CODcr 33.8%, DOC 26.2%) and photocatalysis (AOX 65.1%, CODcr 71.2%, DOC 62.3%) possessed a certain degradation efficiency of wastewater. However, the removal rate of AOX, CODcr, and DOC in wastewater treatment by protocol ICPB reached 80.3%, 90.5%, and 86.7%. FT-IR and GC-MS analysis showed that the ICPB system had photocatalytic activity on the surface of the porous carrier in vitro, which could transform organic into small molecules for microbial utilization or complete mineralization. Moreover, the biofilm in the interior of the TiO₂-coated sponge carrier could mineralize the photocatalytic products, which enhanced the removal of AOX, CODcr, and DOC by more than 15.2%, 20.0%, and 24.0%, respectively. The biofilm in the carrier of the ICPB system evolved, enriched in Proteobacteria, Chloroflexi, Bacteroidetes, and Actinobacteria, microorganisms known to play active roles in the biodegradation of papermaking wastewater.

Stress-responses of microbial population and activity in activated sludge under long-term ciprofloxacin exposure

In this study, the effects of ciprofloxacin on activated sludge were evaluated based on the microbial community and metabolic characteristics. The results indicated that the metabolism of chemical oxygen demand (COD) and nitrogen were inhibited with ciprofloxacin at mg/L level compared to the control experiment, and the concentration of ciprofloxacin was slightly decreased. High-throughput sequencing (HTS) results showed that ciprofloxacin greatly shaped the microbial communities in activated sludge, especially for the Nitrospirae phylum and Nitrospira genus. High concentrations of ciprofloxacin stimulated the enrichment of Zoogloea, thus reducing the stability of the activated sludge. Moreover, quinolone resistance proteins in Aeromonas were enriched, which demonstrates their competitive advantage in these enrichment incubations. Finally, the functional profiles were predicted through Tax4Fun, which revealed the adaption to microbes in activated sludge to the ciprofloxacin selective pressure. This work demonstrates the influence of ciprofloxacin on the activated sludge process, and can provide a useful reference for the assessment of the ecological security of ciprofloxacin.

Total nitrogen removal in biochar amended non-aerated vertical flow constructed wetlands for secondary wastewater effluent with low C/N ratio: Microbial community structure and dissolved organic carbon release conditions

Biochar was utilized to intensify constructed wetland (CW) for further organic and nitrogen removal from secondary wastewater. Four sets of non-aerated biochar amended vertical flow CW (VFCW) were developed to investigate the synergistic effects of biochar and microbes on pollutant removal. Results showed that the average COD and nitrogen removal efficiencies of VFCW1 (with 1% w/w biochar with microbe and plants) achieved 89.1 ± 5.6% and 90.2 ± 3.1% respectively, and their corresponding removal rates of 10.2 ± 0.8 mg-COD/(m³.d) and 3.57 ± 0.3 mg-TN/(m³.d) which were 35 and 52.3% higher than control. The biochar's dissolved organic carbon release in VFCWs indicated that water and acidic media portray the optimum conditions for nitrogen removal. The 16S RNA gene sequencing analysis indicated that in the biochar-amended VFCWs, bacterial phylum Proteobacteria (24.13-51.95%) followed by Chloroflexi (5.64-25.01%), Planctomycetes (8.48-14.43%), Acidobacteria (2.29-11.65%) were abundantly enhanced. Conclusively, incorporating biochar in non-aerated VFCWs is an efficient technique for enhancing nitrogen removal from secondary effluent.

The Prevalence of Virulent and Multidrug-Resistant Enterococci in River Water and in Treated and Untreated Municipal and Hospital Wastewater

The aim of this study is to describe the drug resistance and virulence of enterococci in river water sampled downstream (DRW) and upstream (URW) from the wastewater discharge point, to determine the pool of virulent and drug-resistant enterococci in untreated wastewater (UWW) and the extent to which these bacteria are eliminated from hospital wastewater (HWW) and municipal wastewater treated (TWW) by biological and mechanical methods in a wastewater treatment plant (WWTP). A total of 283 strains were identified with the use of culture-dependent methods and PCR, including seven different species including E. faecalis and E. faecium which were predominant in all analyzed samples. Majority of the strains were classified as multidrug resistant (MDR), mostly on streptomycin and trimethoprim. Strains isolated from wastewater and DRW harbored van genes conditioning phenotypic resistance to vancomycin, the highest percentage of vancomycin-resistant strains (57.0%), mostly strains harboring vanC1 genes (27.6%), was noted in TWW. More than 65.0% of the isolated strains had different virulence genes, the highest number of isolates were positive for cell wall adhesin efaA and sex pheromones cob, cpd, and ccf which participate in the induction of virulence. Many of the strains isolated from TWW were resistant to a higher number of drugs and were more virulent than those isolated from UWW and HWW. The enterococci isolated from DRW and wastewater were characterized by similar multidrug resistance and virulence profiles, and significant correlations were observed between these groups of isolates. These findings suggest that pathogenic enterococci are released with TWW and can spread in the river, pose a serious epidemiological threat and a risk to public health.

Emerging wastewater treatment strategy for efficient nitrogen removal and compact footprint by coupling mainstream nitrogen separation with chemical coagulation and biological aerated filter

In this study, an ammonia nitrogen (NH₄⁺-N) ion exchange (IE) and regeneration (AIR) was constructed, and the chemical enhanced primary treatment (CEPT), AIR and biological aerated filter (BAF) were coupled in series to construct a novel CEPT-AIR-BAF process for efficient pollutants removal. At total hydraulic retention time of 4.6 h, the pilot-scale CEPT-AIR-BAF system obtained effluent with chemical oxygen demand of 17.9 ± 6.0 mg/L, NH₄⁺-N of 0.5 ± 0.3 mg/L, total nitrogen of 2.4 ± 1.0 mg/L and total phosphorus of 0.08 ± 0.05 mg/L. AIR module achieved outstanding NH₄⁺-N IE performance with NaClO-NaCl regeneration, and long-term regeneration increased surface area and mesopore of zeolites. Faster-growing heterotrophic bacteria, such as Pseudomonas and Comamonas, were enriched in BAF. The CEPT-AIR-BAF system saved at least 60% of land occupation and upfront investment, and the treatment cost ($ 0.155/m³) should be further reduced by investigations on the regeneration of loaded zeolite.