High-throughput sequencing reveals microbial communities in drinking water treatment sludge from six geographically distributed plants, including potentially toxic cyanobacteria and pathogens

Unveiling the characteristics of free-living and particle-associated antibiotic resistance genes associated with bacterial communities along different processes in a full-scale drinking water treatment plant

Antibiotic resistance genes (ARGs) as emerging contaminants, often co-occur with mobile genetic elements (MGEs) and are prevalent in drinking water treatment plants (DWTPs). In this study, the characteristics of free-living (FL) and particle-associated (PA) ARGs associated with bacterial communities were investigated along two processes within a full-scale DWTP. A total of 13 ARGs and two MGEs were detected. FL-ARGs with diverse subtypes and PA-ARGs with high abundances displayed significantly different structures. PA-MGEs showed a strong positive correlation with PA-ARGs. Chlorine dioxide disinfection achieved 1.47-log reduction of FL-MGEs in process A and 0.24-log reduction of PA-MGEs in process B. Notably, PA-fraction virtually disappeared after treatment, while blaTEM, sul2, mexE, mexF and IntI1 of FL-fraction remained in the finished water. Moreover, Acinetobacter lwoffii (0.04 % ∼ 45.58 %) and Acinetobacter schindleri (0.00 % ∼ 18.54 %) dominated the 16 pathogens, which were more abundant in FL than PA bacterial communities. PA bacteria exhibited a more complex structure with more keystone species than FL bacteria. MGEs contributed 20.23 % and 19.31 % to the changes of FL-ARGs and PA-ARGs respectively, and water quality was a key driver (21.73 %) for PA-ARGs variation. This study provides novel insights into microbial risk control associated with size-fractionated ARGs in drinking water.

Advances and challenges in the technologies for cyanobacterial cells removal in drinking water treatment

Harmful cyanobacteria in reservoirs pose a serious threat to drinking water safety due to the intracellular metabolites, such as toxins and unpleasant tastes & odours. Effective removal of harmful cyanobacteria with little to no cell damage is very important to ensure the safety of drinking water. This review first introduced development history of cyanobacterial removal technologies in drinking water treatment. Then, impacts of oxidation, coagulation and pre-oxidation enhanced coagulation processes on cyanobacterial removal and integrity of the cells were comprehensively evaluated and discussed. Oxidation can remove cyanobacteria, but high doses of oxidants can result in significant cell lysis and release of intracellular metabolites, especially when using chlorine or ozone. Although there is practically no cell damage during coagulation, the removal efficiency is low in many cases. Pre-oxidation may improve cyanobacterial removal by the subsequent solid-liquid separation processes, and moderate pre-oxidation with little to no cell lysis is very important. Mechanisms of interface interaction between pre-oxidants and cyanobacteria should be defined in future to ensure moderate pre-oxidation of algal cells. Fate of cyanobacterial cells in sludge is also reviewed because more and more waterworks return sludge supernatant to the inlet of plant. Damage to cyanobacterial cells in sludge depends mainly upon coagulant type and dosage, algal species, and cyanobacteria-containing sludge should be treated before cell lysis. Efficient techniques for harmless disposal of cyanobacteria-containing sludge should be developed in future. This paper will help to better understand the cyanobacterial removal processes and provide improved perspectives for future research in this field.

Effects of running time on biological activated carbon filters: water purification performance and microbial community evolution

Ozone-biologically activated carbon (BAC) filtration is an advanced treatment process that can be applied to remove recalcitrant organic micro-pollutants in drinking water treatment plants (DWTPs). In this study, we continuously monitored a new and an old BAC filter in a DWTP for 1 year to compare their water purification performance and microbial community evolution. The results revealed that, compared with the new filter, the use of the old BAC filter facilitated a slightly lower rate of dissolved organic carbon (DOC) removal. In the case of the new BAC filter, we recorded general increases in the biomass and microbial diversity of the biofilm with a prolongation of operating time, with the biomass stabilizing after 7 months. For both new and old BAC filters, Proteobacteria and Acidobacteria were the dominant bacterial phyla. At the genus level, the microbial community gradually shifted over the course of operation from a predominance of Herminiimonas and Hydrogenophaga to one predominated by Bradyrhizbium, Bryobacter, Hyphomicrobium, and Pedomicrobium, with Bradyrhizobium being established as the most abundant genus in the old BAC filter. Regarding spatial distribution, we detected reductions in the biomass and number of operational taxonomic units with increasing biofilm depth, whereas there was a corresponding increase in microbial diversity. However, compared with the effects of time, the influence of depth on the composition of the biofilm microbial community was considerably smaller. Furthermore, co-occurrence network analysis revealed that the microbial community network of the new filter after 11 months of operation was the most tightly connected, although its modular coefficient was the lowest of those assessed. We speculate that the positive and negative interactions within the network may be attributable to symbiotic or competitive relationships among species. Moreover, there may have been a significant negative interaction between SWB02 and Acidovorax, plausibly associated with a competition for substrates.

Microbial genome (Illumina MiSeq) sequencing of drinking water treatment residuals to evaluate compatibility with environmental applications

The clarification of drinking water leads to the production of large quantities of water treatment residuals (WTRs). DNA was extracted from six WTR samples collected from water treatment plants within the UK to compare their bacterial communities and examine whether factors such as coagulant usage (aluminium versus iron salt), the type of water source (reservoir or river), or leachable chemical composition influence these communities. Bacterial 16S variable region 4 (V4) was amplified and sequenced using Illumina MiSeq sequencing. The most abundant phyla in WTR samples were Proteobacteria, Actinobacteria, Bacteroidetes, Acidobacteria, and Firmicutes, collectively representing 92.77-97.8% of the total bacterial sequences. Statistical analysis of microbial profiles indicated that water source played a significant role in microbial community structure, diversity, and richness, however coagulant type did not. PERMANOVA analysis showed that no single chemical variable (pH, organic matter, or extractable element concentration) influenced microbial composition significantly; however, canonical correspondence analysis of WTR microbiomes yielded a model using all these variables that could be used to explain variations in microbial community structures of WTRs (p < 0.05). No common, potentially toxic cyanobacteria, or related pathogens of concern were found. Analysis with PICRUSt showed that WTRs all had similar predicted microbial functional profiles. Overall, the results indicate that WTRs analysed in this study are unlikely to pose any threat to soil microbial community structure when applied to land as a soil conditioner or enhancer and may help to enhance the soil microbial community.

Shotgun Metagenomic Sequencing to Assess Cyanobacterial Community Composition following Coagulation of Cyanobacterial Blooms

The excessive proliferation of cyanobacteria in surface waters is a widespread problem worldwide, leading to the contamination of drinking water sources. Short- and long-term solutions for managing cyanobacterial blooms are needed for drinking water supplies. The goal of this research was to investigate the cyanobacteria community composition using shotgun metagenomics in a short term, in situ mesocosm experiment of two lakes following their coagulation with ferric sulfate (Fe₂(SO₄)₃) as an option for source water treatment. Among the nutrient paramenters, dissolved nitrogen was related to Microcystis in both Missisquoi Bay and Petit Lac St. François, while the presence of Synechococcus was related to total nitrogen, dissolved nitrogen, dissolved organic carbon, and dissolved phosphorus. Results from the shotgun metagenomic sequencing showed that Dolichospermum and Microcystis were the dominant genera in all of the mesocosms in the beginning of the sampling period in Missisquoi Bay and Petit Lac St. François, respectively. Potentially toxigenic genera such as Microcystis were correlated with intracellular microcystin concentrations. A principal component analysis showed that there was a change of the cyanobacterial composition at the genus level in the mesocosms after two days, which varied across the studied sites and sampling time. The cyanobacterial community richness and diversity did not change significantly after its coagulation by Fe₂(SO₄)₃ in all of the mesocosms at either site. The use of Fe₂(SO₄)₃ for an onsite source water treatment should consider its impact on cyanobacterial community structure and the reduction of toxin concentrations.

A comprehensive review on the coagulant recovery and reuse from drinking water treatment sludge

The main treatment unit in conventional systems for surface water is coagulation-flocculation (CF) process, which consumes huge quantities of coagulant, and produces large volume of sludge. The produced sludge is known as one of the components of water treatment sludge (WTS), which is considered as a global issue and hot topic require careful attention from the plant operators and sludge managers to be managed sustainably with applying an ecofriendly method. Among the suggested technologies, recovery and reuse of coagulants from WTS show the potential to decrease the waste disposal and chemicals usage for drinking water treatment significantly. So, this comprehensive review provides a useful insight into environmental and health problems of WTS, reports the sources, physicochemical properties of sludge, describes different sludge management methods by more focus on coagulant recovery (CR), which significantly point out the different aspects of WTS recovery and reuse, and eventually, economic evaluation of the CR process was also discussed. The results of this review confirm that coagulants can be recovered from WTS by different methods and also will be reused for multiple times in the removal of pollutants from water and wastewater. Moreover, the recovered coagulants can be used as building and construction materials, constructed wetlands substrate and other aims.

Metagenomics analysis of probable transmission of determinants of antibiotic resistance from wastewater to the environment - A case study

During mechanical-biological treatment, wastewater droplets reach the air with bioaerosols and pose a health threat to wastewater treatment plant (WWTP) employees and nearby residents. Microbiological pollutants and antimicrobial resistance determinants are discharged to water bodies with treated wastewater (TWW), which poses a potential global epidemiological risk. In the present study, the taxonomic composition of microorganisms was analyzed, and the resistome profile and mobility of genes were determined by metagenomic next-generation sequencing in samples of untreated wastewater (UWW), wastewater collected from an activated sludge (AS) bioreactor, TWW, river water collected upstream and downstream from the wastewater discharge point, and in upper respiratory tract swabs collected from WWTP employees. Wastewater and the emitted bioaerosols near WWTP's facilities presumably contributed to the transmission of microorganisms, in particular bacteria of the phylum Actinobacteria and the associated antibiotic resistance genes (ARGs) (including ermB, ant(2″)-I, tetM, penA and cfxA2) to the upper respiratory tract of WWTP employees. The discharged wastewater increased the taxonomic diversity of microorganisms and the concentrations of various ARGs (including bacA, emrE, sul1, sul2 and tetQ) in river water. This study fills in the knowledge gap on the health risks faced by WWTP employees. The study has shown that microbiological pollutants and antimicrobial resistance determinants are also in huge quantities discharged to rivers with TWW, posing a potential global epidemiological threat.

A systematic review of the water treatment sludge toxicity to terrestrial and aquatic biota: state of the art and management challenges

Safe drinking water' supply is an essential service and depends directly on the water treatment that produces water treatment sludge (WTS) as a product, whose final destination varies and remains a challenge. The ecotoxicity assessment of the WTS address the ecological implications of the WTS disposal but these information is still scarce in the literature. In this sense, we did a systematic review of the ecotoxicological studies on WTS using databases from six platforms. From the 785 papers recovered; 16 studies were eligible and showed the ecotoxicity assays' applicability to evaluate the WTS. We discussed WTS ecotoxicity considering sample characterization; terrestrial and aquatic toxicity assays; and WTS challenges. WTS proved to be a highly heterogeneous matrix composed mainly of coagulant precipitates, including Al and Fe. Studies lack consensus concerning the most representative/sensitive species for evaluating WTS' toxicity. Crustaceans were the most studied aquatic group, although algae species were more sensitive. Besides, soil ecotoxicity assessed only plant growth, and a single study used the earthworm. Even papers used bioassays to indicate the recycling WTS' feasibility, there is a lack of specific legislation regarding the WTS reuse. Furthermore, are necessary a regulation for WTS management that involves an ecological risk assessment.

Distributed treatment of rural environmental wastewater by artificial ecological geographic information system

County rural sewage geographic information system, is the use of geographic information technology and computer graphics, digital storage and management of sewage treatment facilities, the sewage treatment plant equipment management, water purification and sewage network and its surrounding corresponding facilities location information and physical attributes of the two combined, according to the needs of users, the sewage treatment process required data in the form of graphics and text to show to According to the user's needs, the data required in the process of sewage treatment is displayed to the user in a graphic way, so as to meet the needs of government departments for comprehensive control of the operation and maintenance management of sewage treatment facilities. Solve the problem of slow update of basic data in sewage treatment projects and ambiguous presentation of water quality monitoring data caused by paper records. The system uses Web-GIS technology, combined with NET development platform, using MVC model design and implementation. The front-end Bootstrap framework for interface optimization display, the back-end ORM framework to provide persistence classes and database tables between the mapping relationship, convenient to complete the migration of the database. The system function design uses the visualization and analysis function of GIS to manage the wastewater treatment facilities and the wastewater purification process for real-time operation and maintenance supervision, and uses the three-dimensional engine to visualize and display the study of the wastewater pipe network on the Web side. Mainly divided into the following modules: water quality parameters supervision module, mainly real-time monitoring of the sewage treatment process, the parameters are in line with the sewage purification indicators, to play a monitoring and early warning role; equipment operation and maintenance module, mainly for the sewage treatment facilities for fault detection and maintenance of property information; statistical analysis module, the water quality information of different sewage treatment plants for horizontal and vertical comparison and analysis, to improve the sewage treatment The statistical analysis module, which provides data for improving the sewage treatment process; and the 3D pipe network visualization module, which uses virtual reality technology to visualize the sewage pipe network on the Web side to make up for the lack of information on the pipe network in the third dimension.

Temporal Patterns of Bacterial and Viral Communities during Algae Blooms of a Reservoir in Macau

Compositions of microbial communities associated with blooms of algae in a storage reservoir in Macau, China were investigated between 2013 and 2016. Algae were enumerated by visible light microscopy. Profiles of organisms in water were examined by 16S rRNA sequences and viral metagenomics, based on next generation sequencing. Results of 16S rRNA sequencing indicated that majority of the identified organisms were bacteria closely related to Proteobacteria, Cyanobacteria, Verrucomicrobia, Bacteroidetes, and Actinobacteria. Metagenomics sequences demonstrated that the dominant virus was Phycodnavirus, accounting for 70% of the total population. Patterns of relative numbers of bacteria in the microbial community and their temporal changes were determined through alpha diversity indices, principal coordinates analysis (PCoA), relative abundance, and visualized by Venn diagrams. Ways in which the bacterial and viral communities are influenced by various water-related variables were elucidated based on redundancy analysis (RDA). Relationships of the relative numbers of bacteria with trophic status in a reservoir used for drinking water in Macau, provided insight into associations of Phycodnavirus and Proteobacteria with changes in blooms of algae.

Cyanobacterial blooms in China: diversity, distribution, and cyanotoxins

Cyanobacterial blooms, which refer to the massive growth of harmful cyanobacteria, have altered the global freshwater ecosystems during the past decades. China has the largest population in the world, and it is suffering from the harmful effect of water eutrophication and cyanobacterial blooms along with rapid development of the economy and society. Research on cyanobacterial blooms and cyanotoxins in China have been overwhelmingly enhanced and emphasized during the past decades. In the present review, the research on cyanobacterial blooms in China is generally introduced, including the history of cyanobacterial bloom studies, the diversity of the bloom-forming cyanobacteria species (BFCS), and cyanotoxin studies in China. Most studies have focused on Microcystis, its blooms, and microcystins. Newly emerging blooms with the dominance of non-Microcystis BFCS have been gradually expanding to wide regions in China. Understanding the basic features of these non-Microcystis BFCS and their blooms, including their diversity, occurrence, physio-ecology, and harmful metabolites, will provide direction on future studies of cyanobacterial blooms in China.

Washing and Heat Treatment of Aluminum-Based Drinking Water Treatment Residuals to Optimize Phosphorus Sorption and Nitrogen Leaching: Considerations for Lake Restoration

Drinking water treatment residuals (DWTRs) generated during drinking water treatment have been proposed for use in lake restoration as a solid-phase sorbent to inactivate phosphorus (P) in lake sediment. However, treatments that minimize leaching of nitrogen (N) and optimize P sorption capacity may be necessary prior to use. This study assessed seven different treatment methods, including washing and heat treatments at different temperatures and with and without oxygen limitation, among two DWTRs from Thailand. Results showed that oxygen-limited heat treatment at 600 °C substantially reduced N leaching (<0.2 mg/kg TKN) while also improving P sorption capacity (increase of 18–32% compared to untreated DWTR) to a maximum of 45.7 mg P/kg. Washing with deionized water reduced N leaching if a sufficient volume was used but did not improve P sorption. Heating at 200 °C with or without the presence of oxygen did not improve N leaching or P sorption. Regression of P sorption parameters from a two-surface Langmuir isotherm against physio-chemical properties indicated that oxalate-extractable (i.e., amorphous) aluminum and iron were significantly associated with total P sorption capacity (R2 = 0.94), but micropores and oxalate-extractable P modulated the P sorption from high-affinity to low-affinity mechanisms. In conclusion, this study confirmed the importance of amorphous aluminum in DWTRs for inactivating P, and the results suggest that high-temperature treatment under oxygen-limited conditions may be the most reliable way to optimize DWTRs for environmental remediation applications.

Carcass decay deteriorates water quality and modifies the nirS denitrifying communities in different degradation stages

Corpse degradation may release amounts of hazardous materials (e.g., cadaverine, putrescine and ammonia) into surrounding areas, which deteriorate environments and result in nitrogen contamination. Nitrate or nitrite can be reduced to nitrogen gas by denitrifying bacteria, thus alleviating nitrogen contamination and purifying aquatic environments. However, the reaction of nirS-encoding denitrifiers to carcass degradation is less studied. Therefore, water physiochemical analysis and high-throughput sequencing were applied to explore the successional pattern of nirS denitrifying communities in the Yellow River water and tap water during three stages of animal cadaver decay (submerged fresh, advanced floating decay as well as sunken remains) and relevant control group. Nitrate nitrogen (NO₃-N) and ammonia nitrogen (NH₄⁺-N) concentration in corpse groups were highly elevated compared with control groups. The dominant phylum for nirS denitrifying communities was Proteobacteria. Abundant denitrifying genera Paracoccus, Alicycliphilus and Diaphorobacter were detected, and these genera have been reported to participate in the degradation of organic pollutants. Particularly, nirS-type community structures were remarkably influenced by corpse decay and became similar with succession. Water total dissolved solids (TDS), salinity, conductivity (CON) and phosphate were primary impacting factors driving the community structures, but the effect of water type was almost negligible. Notably, denitrifying community assembly was dominated by deterministic processes rather than stochastic processes, and the relative importance of deterministic processes among most corpse groups was higher than that in control groups, indicating that environmental filtering regulates the denitrifying communities. Our results provide new insight into environmental purification for hazardous materials produced by corpse degradation, thereby providing valuable advice to environmental administration.

Bacterial community compositions and nitrogen metabolism function in a cattle farm wastewater treatment plant revealed by Illumina high-throughput sequencing

Bacteria play an important role in pollutant transformation in activated sludge-based wastewater treatment plants (WWTPs). Exploring the microbial community structure and diversity is essential to improving the performance of wastewater treatment processes. This study employed Illumina MiSeq high-throughput sequencing to investigate the microbial community composition and diversity in a cattle farm wastewater treatment plant (Cf-WWTP). The results showed that the dominant phyla in the whole process were Proteobacteria, Bacteroidetes, and Firmicutes. The principal coordinate analysis (PCoA) indicated that the different stages had a significant impact on the microbial community structure; Bacteroidetes was the dominant phylum in the anearobic stage and Proteobacteria was the dominant phylum in the anoxic-oxic stage. Redundancy analysis (RDA) revealed that total phosphorus (TP) was the most significant factor that regulated the microbial community composition, followed by chemical oxygen demand (COD), total nitrogen (TN), and pH. Proteobacteria, Patescibacteria, and Chloroflexi were simultaneously negatively correlated with TN, COD, and TP. Nitrogen metabolic pathway and transformation mechanism was elucidated by a complete denitrification function predicted with phylogenetic investigation of communities with reconstruction of unobserved states (PICRUSt), as well as detection of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB). These results provide new insights into our understanding of microbial community and metabolic functions of Cf-WWTP.

Assessing the Impacts of Land Spreading Water-Treatment Residuals on the Anecic Earthworm Lumbricus terrestris, Soil Microbial Activity, and Porewater Chemistry

Water-treatment residuals (WTRs), by-products of drinking water clarification, are increasingly recycled to land to promote circular economy and reduce disposal costs, yet there is a lack of published literature on their effects on soil ecology. In the present study, the effects of WTRs on earthworm growth, soil respiration, and soil porewater chemistry were investigated throughout a 7-wk outdoor mesocosm trial. We derived WTRs from both aluminum and iron coagulants and applied them to a loam soil at 0 to 20% (w/w). In addition, soil from a field that had received long-term WTR applications and that of an adjacent nontreated reference field were included in the study. Earthworm mass increase was significantly higher in all but one laboratory-treated soil when compared to the control. Furthermore, a linear regression model was used to predict increases in weekly soil respiration based on the application rates of both Al and Fe WTRs. In addition, a significant increase in soil respiration was observed from the treated farm soils during the first 4 wk of the trial. Measured sodium, magnesium, potassium, and iron porewater concentrations were higher in the treated farm soils than the reference site soil in a majority of samples, although these differences may be related to land management. Laboratory-treated soils had elevated porewater arsenic concentrations (e.g., ~17 µg L^-1 in controls vs ~62 µg L^-1 in the 20% w/w Al WTR treatment in week 1), whereas porewater nickel concentrations were, respectively, elevated and lowered in Al WTR- and Fe WTR-amended samples. Overall, observed disturbances to soil ecology were determined to be minimal. Environ Toxicol Chem 2021;40:1964-1972. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Next generation sequencing approaches to evaluate water and wastewater quality

The emergence of next generation sequencing (NGS) is revolutionizing the potential to address complex microbiological challenges in the water industry. NGS technologies can provide holistic insight into microbial communities and their functional capacities in water and wastewater systems, thus eliminating the need to develop a new assay for each target organism or gene. However, several barriers have hampered wide-scale adoption of NGS by the water industry, including cost, need for specialized expertise and equipment, challenges with data analysis and interpretation, lack of standardized methods, and the rapid pace of development of new technologies. In this critical review, we provide an overview of the current state of the science of NGS technologies as they apply to water, wastewater, and recycled water. In addition, a systematic literature review was conducted in which we identified over 600 peer-reviewed journal articles on this topic and summarized their contributions to six key areas relevant to the water and wastewater fields: taxonomic classification and pathogen detection, functional and catabolic gene characterization, antimicrobial resistance (AMR) profiling, bacterial toxicity characterization, Cyanobacteria and harmful algal bloom identification, and virus characterization. For each application, we have presented key trends, noteworthy advancements, and proposed future directions. Finally, key needs to advance NGS technologies for broader application in water and wastewater fields are assessed.

Four decades of progress in cylindrospermopsin research: The ins and outs of a potent cyanotoxin

The cyanotoxin cylindrospermopsin (CYN), a toxic metabolite from cyanobacteria, is of particular concern due to its cosmopolitan occurrence, aquatic bioaccumulation, and multi-organ toxicity. CYN is the second most often recorded cyanotoxin worldwide, and cases of human morbidity and animal mortality are associated with ingestion of CYN contaminated water. The toxin poses a great challenge for drinking water treatment plants and public health authorities. CYN, with the major toxicity manifested in the liver, is cytotoxic, genotoxic, immunotoxic, neurotoxic and may be carcinogenic. Adverse effects are also reported for endocrine and developmental processes. We present a comprehensive review of CYN over the past four decades since its first reported poisoning event, highlighting its global occurrence, biosynthesis, toxicology, removal, and monitoring. In addition, current data gaps are identified, and future directions for CYN research are outlined. This review is beneficial for understanding the ins and outs of this environmental pollutant, and for robustly assessing health hazards posed by CYN exposure to humans and other organisms.

Temporal succession of water microbiomes and resistomes during carcass decomposition in a fish model

Carcass decomposition in water may cause serious environmental pollution, which poses a great threat to water quality and public health. However, water microbial community succession and antibiotic resistance genes (ARGs) during carcass decomposition process are less explored. Using high-throughput sequencing and high-throughput quantitative PCR techniques, the temporal succession of water bacterial communities and ARGs profiles in experimental groups (fish carcasses) and control groups (no carcasses) containing two different types of water (the Yellow River water and tap water) in different successional stages were studied. Our results showed that NH₃-N concentration in the corpse groups has greatly risen and exceeded more than 28 times on average over the safety thresholds of water quality. Some potential pathogenic genera Comamonas, Bacteroides and Pseudomonas significantly increased during carcass decomposition process. The bacterial communities of the Yellow River water and tap water in the experimental groups exhibited similar succession patterns, and community dissimilarities between the two groups decreased and smaller over time, indicating that bacterial community convergence. NH₃-N, NO₃-N and time were three most important factors in determining bacteria community structures. The influence of water type on corpse bacterial community structures was significant but weak. The gene copy number of seven detected ARGs (cmlA1-01, floR, sul1, sul2, tetG-01, tetM-01 and tetQ) in the experimental groups was more abundant than that in the control groups. The ARGs concentrations in the corpse groups were even enriched 19-fold (minimum) to 148-fold (maximum) compared to the gene tetQ of the Yellow River water in the control groups on the initial stage. Redundancy analysis (RDA) indicated that Bacteroidetes and Firmicutes were significantly correlated with all detected ARGs. This study emphasizes that cadaver degradation leads to the deterioration of nitrogen pollution, the abundance increase of potential pathogens, and the transfer of ARGs from dead animals to water environment, thereby uncovering the harmful effects of related water pollution for human health.

Long-term agricultural contamination shaped diversity response of sediment microbiome

The pollution caused by agricultural production poses a threat to the ecological integrity of river ecosystems, altering the structure and function of river ecosystems. Differences in microbial community structure provide useful information about the impact of agricultural pollution on the biological integrity of ecosystems, but generally convey little information regarding ecosystem functions. In this study, using Illumina MiSeq sequencing technology based on the 16S rRNA gene, river sediment samples associated with four different types of agricultural pollution were comprehensively analyzed. The results show that the total organic carbon (TOC) content was highest at the YZS site (animal husbandry sewage) among the assayed sites, but the species richness and uniformity were lowest at this site, which may have been caused by the high nutrient source of the sewage. Furthermore, in the three YZS samples affected by the long-term discharge of aquaculture tail-water, the unique genus Dechloromonas and the genus Candidatus-Competitor were observed, which are strongly correlated with phosphorus conversion. The formation of network modules may correspond to the coexistence of functional bacteria accustomed to multiple niche combinations under different agricultural pollution conditions in river sediments. According to the PICRUSt functional prediction, the bacterial community in the agricultural polluted river sediment primarily harbored 46 subfunctions, exhibiting richness of functions. Overall, our results provide a more comprehensive understanding of the structure and ecological processes associated with the aggregation of bacterial communities, which is beneficial for the management of river environments.

The sequential dewatering and drying treatment enhanced the potential favorable effect of microbial communities in drinking water treatment residue for environmental recycling

The beneficial recycling of drinking water treatment residue (DWTR) for environmental remediation has received increasingly interests; whereas, the reported potential effect of microbial communities in different DWTR was ambiguous, which was unfavorable for the beneficial recycling. This study hypothesized that the varied treatment to DWTR in different waterworks induced the ambiguous effect; accordingly, responses of microbial communities in DWTR to the sequential dewatering and drying treatment were determined based on samples from three waterworks, in combination with 180-d incubation tests. The results showed that the microbial communities varied remarkably in different DWTR before being dewatered (DWTS). However, after dewatering, the increased microbial diversities were observed, and the microbial communities exhibited higher similarities among the dewatered DWTR from different waterworks; furthermore, the dewatered DWTR with subsequent drying treatment enriched more bacteria genus with potential environmental functions after incubation tests. The variations of microbial communities were closely related to DWTR properties, such as pH, organic matter, metals, P, and water extractable nutrients. Further analysis indicated that with maintaining high adsorption capability of DWTR, the dewatering treatment tended to retain specific microbial communities that may be induced by the applied similar techniques in different waterworks; the accumulated nutriments due to drying treatment and the stable DWTR pH enhanced the potential functional bacteria enrichment. Overall, the dewatering and drying treatment led to microbial communities with generality in different DWTR and increased the potential favorable microbial effect, promoting DWTR recycling in environmental remediation.

Can Cyanobacterial Diversity in the Source Predict the Diversity in Sludge and the Risk of Toxin Release in a Drinking Water Treatment Plant?

Conventional processes (coagulation, flocculation, sedimentation, and filtration) are widely used in drinking water treatment plants and are considered a good treatment strategy to eliminate cyanobacterial cells and cell-bound cyanotoxins. The diversity of cyanobacteria was investigated using taxonomic cell counts and shotgun metagenomics over two seasons in a drinking water treatment plant before, during, and after the bloom. Changes in the community structure over time at the phylum, genus, and species levels were monitored in samples retrieved from raw water (RW), sludge in the holding tank (ST), and sludge supernatant (SST). Aphanothece clathrata brevis, Microcystis aeruginosa, Dolichospermum spiroides , and Chroococcus minimus were predominant species detected in RW by taxonomic cell counts. Shotgun metagenomics revealed that Proteobacteria was the predominant phylum in RW before and after the cyanobacterial bloom. Taxonomic cell counts and shotgun metagenomic showed that the Dolichospermum bloom occurred inside the plant. Cyanobacteria and Bacteroidetes were the major bacterial phyla during the bloom. Shotgun metagenomics also showed that Synechococcus, Microcystis , and Dolichospermum were the predominant detected cyanobacterial genera in the samples. Conventional treatment removed more than 92% of cyanobacterial cells but led to cell accumulation in the sludge up to 31 times more than in the RW influx. Coagulation/sedimentation selectively removed more than 96% of Microcystis and Dolichospermum. Cyanobacterial community in the sludge varied from raw water to sludge during sludge storage (1-13 days). This variation was due to the selective removal of coagulation/sedimentation as well as the accumulation of captured cells over the period of storage time. However, the prediction of the cyanobacterial community composition in the SST remained a challenge. Among nutrient parameters, orthophosphate availability was related to community profile in RW samples, whereas communities in ST were influenced by total nitrogen, Kjeldahl nitrogen (N- Kjeldahl), total and particulate phosphorous, and total organic carbon (TOC). No trend was observed on the impact of nutrients on SST communities. This study profiled new health-related, environmental, and technical challenges for the production of drinking water due to the complex fate of cyanobacteria in cyanobacteria-laden sludge and supernatant.

Diversity Assessment of Toxic Cyanobacterial Blooms during Oxidation

Fresh-water sources of drinking water are experiencing toxic cyanobacterial blooms more frequently. Chemical oxidation is a common approach to treat cyanobacteria and their toxins. This study systematically investigates the bacterial/cyanobacterial community following chemical oxidation (Cl₂, KMnO₄, O₃, H₂O₂) using high throughput sequencing. Raw water results from high throughput sequencing show that Proteobacteria, Actinobacteria, Cyanobacteria and Bacteroidetes were the most abundant phyla. Dolichospermum, Synechococcus, Microcystis and Nostoc were the most dominant genera. In terms of species, Dolichospermum sp.90 and Microcystis aeruginosa were the most abundant species at the beginning and end of the sampling, respectively. A comparison between the results of high throughput sequencing and taxonomic cell counts highlighted the robustness of high throughput sequencing to thoroughly reveal a wide diversity of bacterial and cyanobacterial communities. Principal component analysis of the oxidation samples results showed a progressive shift in the composition of bacterial/cyanobacterial communities following soft-chlorination with increasing common exposure units (CTs) (0–3.8 mg·min/L). Close cyanobacterial community composition (Dolichospermum dominant genus) was observed following low chlorine and mid-KMnO₄ (287.7 mg·min/L) exposure. Our results showed that some toxin producing species may persist after oxidation whether they were dominant species or not. Relative persistence of Dolichospermum sp.90 was observed following soft-chlorination (0.2–0.6 mg/L) and permanganate (5 mg/L) oxidation with increasing oxidant exposure. Pre-oxidation using H₂O₂ (10 mg/L and one day contact time) caused a clear decrease in the relative abundance of all the taxa and some species including the toxin producing taxa. These observations suggest selectivity of H₂O₂ to provide an efficient barrier against toxin producing cyanobacteria entering a water treatment plant.

Hydrogen Sulfide Signaling Protects Chlamydomonas reinhardtii Against Allelopathic Damage From Cyanobacterial Toxin Microcystin-LR

Cyanobacterial blooms have become more frequent and serious in recent years. Not only do massive blooms cause environmental pollution and nutrient eutrophication, but they also produce microcystins (MCs), a group of toxic cycloheptapeptides, which threaten aquatic ecosystem and human health. As such, clarifying the allelopathic interactions between cyanobacteria and other algae is critical to better understand the driving factors of blooms. To date, however, such studies remain largely insufficient. Here, we treated model alga Chlamydomonas reinhardtii with microcystin-LR (MC-LR) to determine its allelopathic effects. Results showed that MC-LR markedly suppressed C. reinhardtii cell viability. Comparative proteomic and physiological analyses revealed that MC-LR significantly up-regulated protein abundance of antioxidants ascorbate peroxidase (APX) and catalase (CAT) at the beginning stage of exposure. This was accompanied by an over-accumulation of hydrogen peroxide (H₂O₂), suggesting that MC-LR suppresses cell viability via oxidative damage. Furthermore, we found that MCs induced desulfhydrase (DES) activity for hydrogen sulfide (H₂S) generation at the beginning stage. Additional H₂S donors reactivated antioxidant enzyme activity, which reduced H₂O₂ accumulation and ultimately enhanced C. reinhardtii tolerance to MC-LR damage. This effect could be reserved by inhibiting H₂S biosynthesis. Simultaneously, we found that H₂S also suppressed MC-LR-induced cell autophagy, and thus attenuated the toxic effects of MC-LR. Our findings suggest that oxidative bursts may be the main reason for the allelopathic effects of MC-LR on C. reinhardtii viability and that H₂S signaling may enhance C. reinhardtii tolerance to MC-LR through the activation of antioxidant enzyme activity and suppression of cell autophagy.

Removal of Tetracycline from Water Using Activated Carbon Derived from the Mixture of Phragmites australis and Waterworks Sludge

Sludge-based activated carbon with doped Phragmites australis was prepared using an environment-friendly method to treat waterworks sludge (WS) and obtain an economical adsorbing material for tetracycline (TC) elimination. For the WS, P. australis was used as an additive to optimize the preparation of activated carbon. Optimum preparation conditions were as follows: activation temperature, 600 °C; ZnCl₂ concentration, 3 mol/L; activation time, 50 min; impregnation ratio (weight of mix sample: weight of ZnCl₂) of 1:2.5; and the mixed ratio of P. australis with WS, 40%. The obtained activated carbon owned well-developed Brunauer-Emmett-Teller surface area (949.90 m²/g). The acidic and basic functional groups were improved to 0.762 and 0.016 mmol/g, respectively. The pseudo-second-order kinetic and Freundlich isotherm equations were more suitable models to simulate adsorption with the maximum adsorption capacity of 153.4 mg/g. According to the thermodynamic parameters, the adsorption process was spontaneous and endothermic. Electrostatic interaction, hydrogen bonding formation, and ion complexation adsorption mechanisms were the mechanisms underlying the adsorption of TC.

Metagenomic profiling of antibiotic resistance genes and their associations with bacterial community during multiple disinfection regimes in a full-scale drinking water treatment plant

For comprehensive insights into the effects of multiple disinfection regimes on antibiotic resistome in drinking water, this study utilized metagenomic approaches to reveal the changing patterns of antibiotic resistance genes (ARGs) and bacterial community as well as their associations. A total of 297 ARGs within 17 types were detected in the drinking water, and their total relative abundance ranged from 195.49 ± 24.85 to 626.31 ± 38.61 copies of ARGs per cell. The total ARG abundance was significantly increased after the antimicrobial resin and ultraviolet (AR/UV) disinfection while significantly decreased after the ozone and chlorine (O₃/Cl₂) disinfection and remained stable after AR/Cl₂ disinfection. Overall, 18 ARGs including bacA, mexT, and bla_OXA-12, mainly affiliated to bacitracin, multidrug, and beta-lactam, were persistent and discriminative during all the disinfection strategies in drinking water, and they were considered as key ARGs that represent the antibiotic resistome during drinking water disinfection. Additionally, possible hosts of 50% key ARGs were revealed based on co-occurrence network. During multiple disinfection processes, the change of Fusobacteriales and Aeromonadaceae in abundance mainly contributed to the abundance shift of bacA, and Pseudomonas mainly increased the abundance of mexT. These findings indicated that bacterial community shift may be the key factor driving the change of antibiotic resistome during disinfection. The strong association between antibiotic resistome alteration and bacterial community shift proposed in this study may enhance our understanding of the underlying mechanism of the disinfection effects on antibiotic resistance and benefit effective measures to improve safety of drinking water.

Changes in the process performance and microbial community by addition of the metabolic uncoupler 3,3',4',5-tetrachlorosalicylanilide in sequencing batch reactors

A complete study about the effects of 3,3',4',5-tetrachlorosalicylanilide (TCS) on organic matter elimination performance, sludge production and on the microbial community of a biological wastewater treatment process has been performed. For this purpose two sequencing batch reactors (SBR) worked in parallel for 43 days with 0.8 mg·L^-1 of TCS (SBR-1) and without this metabolic uncoupler (SBR-2). Results indicated that 63.3% of sludge reduction was achieved in SBR-1. However, COD removal efficiency was maintained in similar values in both reactors (89.1% and 92.1% in SBR-1 and SBR-2, respectively). The exhaustive mixed liquor characterization led to know deeply the action mechanism of TCS. In this way, a 69% of adenosine triphosphate (ATP) reduction was observed in SBR-1 in comparison with values measured in SBR-2. On the contrary, an increase in soluble microbial products (SMP) and DNA concentrations occurred as a consequence of TCS addition. Thus, it could be concluded that sludge reduction due to TCS addition was due to both uncoupling effect and cellular lysis. Also, increase in all microbial hydrolytic enzymatic activities measured was observed, which explained the stable performance achieved in SBR-1 despite to the results explained above. It should be highlighted that this uncoupler should not be used in biological treatments that require nitrogen elimination because nitrifying bacteria were affected by its addition (Nitrosomonas and Nitrospira). Finally, the 16S rRNA gene amplicon sequencing informed that an important reduction of bacterial diversity resulted in SBR-1 due to TCS addition.

Composition of bacterial communities in municipal wastewater treatment plant

Efforts to understand the environmental and biological factors that influence the dynamics of microbial communities have received substantial attention in microbial ecology. In this study, Illumina MiSeq high-throughput sequencing technology was used to examine the microbial community structure of activated sludge in municipal wastewater treatment systems (Chuzhou city, China). Overall, Proteobacteria, Chloroflexi, Actinobacteria, Acidobacteria, Actinobacteria, Bacteroidetes, and Firmicutes were the most dominant phyla in the five activated sludge samples. However, the community structure of nitrifying bacteria was relatively simple, and diversity was low; only AOB (Nitrosomonas) and NOB (Nitrospira) were detected. The dominant bacteria in the anaerobic sludge, anoxic sludge and oxic sludge were the same, and each bacterial species was relatively uniform, with differences only in proportions. Redundancy analysis indicated that pH, TP and COD were strong environmental factors influencing the bacterial community distribution. PICRUSt was used to describe the metabolic and functional abilities of the activated sludge bacterial communities. The results emphasized the vast genetic diversity of these organisms, which are involved in various essential processes such as amino acid transport and metabolism, energy production and conversion, cell wall/membrane/envelope/biogenesis, signal transduction mechanisms, and carbohydrate transport and metabolism. Activated sludge of municipal wastewater treatment systems can be ranked in the following order based on the 16S rRNA gene copy numbers of the detected phylotypes: S1 > S2 > S4 > S5 > S3. This study provides basic data and a theoretical analysis of the optimal design and operation in wastewater treatment plants.

Formation of odorant haloanisoles and variation of microorganisms during microbial O-methylation in annular reactors equipped with different coupon materials

Taste and odor (T & O) issues in drinking water have become serious problems which cannot be ignored by customers. Several studies have confirmed that microbes in water can biotransform halophenols (HPs) to haloanisoles (HAs) with earthy and musty flavors via microbial O-methylation. In this paper, the formation of 2-chloroanisole (2-CA), 2,4-dichloroanisole (2,4-DCA), 2,4,6-trichloroanisole (2,4,6-TCA), 2,3,6-trichloroanisole (2,3,6-TCA) and 2,4,6-tribromoanisole (2,4,6-TBA), and the microbial variation during the microbial O-methylation were investigated in annular reactors (ARs) with three coupon materials. For precursors, 42.5% of 2-CP and 68.9% of 2,4-DCP decayed during the reaction. Among the five HAs, the formation rate constant followed an order of 2,4,6-TCA > 2-CA > 2,4,6-TBA > 2,4-DCA ~ 2,3,6-TCA, while [HA]_max followed a totally opposite one. The simulated flow velocity had no significant effect (p > 0.05) on HA formation. Ductile iron (DI) AR could produce more HAs than stainless steel (SS) and polyvinyl chloride (PVC) ARs. The final HA molar concentration followed an order of 2,3,6-TCA > 2,4-DCA > 2,4,6-TBA ~ 2,4,6-TCA > 2-CA, which might be explained by multiple factors including HP's dissociation degree, halogen atom's steric hindrance and specificity of HP O-methyltransferases. During the reaction, the microbial biomass dramatically increased 6.8-9.0 times in bulk water but dropped significantly on coupon biofilms. The effect of HPs significantly changed the bacterial communities on coupon in terms of composition and diversity, and declined the relative abundance of HA-producing bacteria, while fungi and their HA-producing genus showed better resistance ability towards HPs. By using Pearson correlation analysis, a significant correlation (p = 0.0003) was found between [HA]_max and initial coupon biofilm biomass. Finally, a linear relationship was established between initial total biomass and HA formation potential.

The Nile River Microbiome Reveals a Remarkably Stable Community Between Wet and Dry Seasons, and Sampling Sites, in a Large Urban Metropolis (Cairo, Egypt)

World freshwater supplies are in need of microbiome diversity analyses as a first step to future ecological studies, and to monitor water safety and quality. The Nile is a major north-flowing river in Africa that displays both spatial and temporal variations in its water quality. Here, we present the first microbiome analysis of the Nile River water in two seasons: (1) summer representing the wet season, and (2) winter representing the dry season, as sampled around Cairo, the capital of Egypt. Surface river water samples were collected from selected locations along the path of river, and the microbial composition was analyzed by next-generation sequencing of the 16S rRNA gene. We found a striking stability in the Nile microbiome community structure along the examined geographical urban sites and between the wet and dry seasons as evidenced by the high proportion of shared operational taxonomic unit values among all samples. The community was dominated by the Cyanobacteria (mainly Synechococcus), Actinobacteria candidate family (ACK-M1), and Proteobacteria (mainly family Comamonadaceae). Among these dominant taxa, Synechococcus exhibited seasonal driven variation in relative abundance. Other taxa were predominantly rare across all seasons and locations, including genera members of which have been implicated as pathogens such as Acinetobacter, Aeromonas, and Legionella. In addition, comparisons with data on freshwater microbiome in other world regions suggest that surface water communities in large rivers exhibit limited variation. Our results offer the first insights on microbial composition in one of the most notable rivers near a large metropolis.