Population Dynamics of Bulking and Foaming Bacteria in a Full-scale Wastewater Treatment Plant over Five Years

Activated sludge microbial community assembly: the role of influent microbial community immigration

Wastewater treatment plants (WWTPs) are host to diverse microbial communities and receive a constant influx of microbes from influent wastewater. However, the impact of immigrants on the structure and activities of the activated sludge (AS) microbial community remains unclear. To gain insight on this phenomenon known as perpetual community coalescence, the current study utilized controlled manipulative experiments that decoupled the influent wastewater composition from the microbial populations to reveal the fundamental mechanisms involved in immigration between sewers and AS-WWTP. The immigration dynamics of heterotrophs were analyzed by harvesting wastewater biomass solids from three different sewer systems and adding to synthetic wastewater. Immigrating influent populations were observed to contribute up to 14% of the sequencing reads in the AS. By modeling the net growth rate of taxa, it was revealed that immigrants primarily exhibited low or negative net growth rates. By developing a protocol to reproducibly grow AS-WWTP communities in the lab, we have laid down the foundational principles for the testing of operational factors creating community variations with low noise and appropriate replication. Understanding the processes that drive microbial community diversity and assembly is a key question in microbial ecology. In the future, this knowledge can be used to manipulate the structure of microbial communities and improve system performance in WWTPs.IMPORTANCEIn biological wastewater treatment processes, the microbial community composition is essential in the performance and stability of the system. This study developed a reproducible protocol to investigate the impact of influent immigration (or perpetual coalescence of the sewer and activated sludge communities) with appropriate reproducibility and controls, allowing intrinsic definitions of core and immigrant populations to be established. The method developed herein will allow sequential manipulative experiments to be performed to test specific hypothesis and optimize wastewater treatment processes to meet new treatment goals.

Effects of operational parameters on bacterial communities in Hong Kong and global wastewater treatment plants

Wastewater treatment plants (WWTPs) are indispensable biotechnology facilities for modern cities and play an essential role in modern urban infrastructure by employing microorganisms to remove pollutants in wastewater, thus protecting public health and the environment. This study conducted a 13-month bacterial community survey of six full-scale WWTPs in Hong Kong with samples of influent, activated sludge (AS), and effluent to explore their synchronism and asynchronism of bacterial community. Besides, we compared AS results of six Hong Kong WWTPs with data from 1,186 AS amplicon data in 269 global WWTPs and a 9-year metagenomic sequencing survey of a Hong Kong WWTP. Our results showed the compositions of bacterial communities varied and the bacterial community structure of AS had obvious differences across Hong Kong WWTPs. The co-occurrence analysis identified 40 pairs of relationships that existed among Hong Kong WWTPs to show solid associations between two species and stochastic processes took large proportions for the bacterial community assembly of six WWTPs. The abundance and distribution of the functional bacteria in worldwide and Hong Kong WWTPs were examined and compared, and we found that ammonia-oxidizing bacteria had more diversity than nitrite-oxidizing bacteria. Besides, Hong Kong WWTPs could make great contributions to the genome mining of microbial dark matter in the global "wanted list." Operational parameters had important effects on OTUs' abundance, such as the temperature to the genera of Tetrasphaera, Gordonia and Nitrospira. All these results obtained from this study can deepen our understanding of the microbial ecology in WWTPs and provide foundations for further studies.

IMPORTANCE

Wastewater treatment plants (WWTPs) are an indispensable component of modern cities, as they can remove pollutants in wastewater to prevent anthropogenic activities. Activated sludge (AS) is a fundamental wastewater treatment process and it harbors a highly complex microbial community that forms the main components and contains functional groups. Unveiling "who is there" is a long-term goal of the research on AS microbiology. High-throughput sequencing provides insights into the inventory diversity of microbial communities to an unprecedented level of detail. At present, the analysis of communities in WWTPs usually comes from a specific WWTP and lacks comparisons and verification among different WWTPs. The wide-scale and long-term sampling project and research in this study could help us evaluate the AS community more accurately to find the similarities and different results for different WWTPs in Hong Kong and other regions of the world.

Temporal metagenomic characterization of microbial community structure and nitrogen modification genes within an activated sludge bioreactor system

IMPORTANCE

Wastewater treatment plays an essential role in minimizing negative impacts on downstream aquatic environments. Microbial communities are known to play a vital role in the wastewater treatment process, particularly in the removal of nitrogen and phosphorus, which can be especially damaging to aquatic ecosystems. There is limited understanding of how these microbial communities may change in response to fluctuating temperatures or how seasonality may impact their ability to participate in the treatment process. The findings of this study indicate that the microbial communities of wastewater are relatively stable both compositionally and functionally across fluctuating temperatures.

Landfill leachate treatment with a full-scale membrane bioreactor: impact of leachate characteristics on filamentous bacteria

Bulking and foaming are extreme filamentous bacterial growths that present serious challenges for the biological leachate treatment process. The current study evaluates the performance of long-term full-scale membrane bioreactor (MBR) treating landfill leachate, specifically focusing on filamentous bacteria overgrowth in the bioreactors. The influence of the variation in leachate structure and operational conditions on floc morphology and filamentous bacteria overgrowth were analyzed for 11 months of operation of the full-scale MBR system. The average chemical oxygen demand (COD) and NH4-N removal efficiencies of the system were 87.8 ± 4% and 99.5 ± 0.7%. However, incomplete denitrification was observed when the F/M ratio was low. The high C/N ratio was observed to enhance the frequency of small flocs. Furthermore, a poor to medium diversity of the microbial community was observed. Haliscomenobacter hydrossis, Microthrix parvicella, and Type 021N were found as the most numerous filamentous organisms. Paramecium spp., Euplotes spp., and Aspidisca spp. were found in small quantities. The limited concentration of PO4-P in the leachate compared to high COD and NH4-N concentrations most probably caused phosphate deprivation and increased abundance of identified filamentous microorganisms. This work is the first study in Türkiye that investigates the bulking and foaming problem in full-scale MBR that treats landfill leachate. Hence, it may provide some pioneering perspectives into landfill leachate remediation by monitoring the hybrid biological system.

An inexpensive, reproducible method to quantify activated sludge foaming potential: Validation through lab-scale studies and year-long full-scale sampling campaign

Activated sludge is a conventional treatment process for biochemical oxygen demand (BOD) and total suspended solids (TSS) removal at water resource recovery facilities (WRRFs). Foaming events are a common operational issue in activated sludge and can lead to decreased treatment efficiency, maintenance issues, and potential environmental health risks. Stable foaming events are caused by biological and chemical drivers (i.e., microbes and surfactants) during the aeration process. However, foaming events are difficult to predict and quantify. We present an inexpensive and easy-to-use method that can be applied at WRRFs to quantify foaming potential. Subsequently, the method was applied over a year-long full-scale study while data on microbial community composition and functional parameters associated with foaming potential were collected from activated sludge samples at South Shore Water Reclamation Facility (WRF) (Oak Creek, WI). Results from the development of the foaming potential method using linear alkylbenzene sulfonate (LAS) showed that the method was reproducible (relative standard deviation <20%) and able to capture changes in foam-inducing constituents. Using full-scale activated sludge samples, higher relative abundance values for the following genera were associated with foaming events: Zoogloea, Flavobacterium, Variovorax, and Bdellovibrio. This is the first report that Variovorx and Bdellovibrio relative abundance was correlated with foaming events in activated sludge. Furthermore, the foaming potential positively correlated (ρ = 0.24) with soluble total nitrogen. Characterizing foaming events through frequent sampling and monitoring of specific genera and functional parameters may allow for predictions and preemptive mitigation efforts to avoid negative consequences in the future. PRACTITIONER POINTS: A reproducible method to measure foaming potential in activated sludge is available. Genera Zoogloea, Flavobacterium, Variovorax, and Bdellovibrio correlated with foaming events. A year-long sampling campaign of activated sludge measuring foaming potential and microbial community composition was conducted at South Shore Water Reclamation Facility in Oak Creek, WI. More research at other facilities with this method is needed to understand links between microbes and foaming.

Seasonal microbial community dynamics complicates the evaluation of filamentous bulking mitigation strategies in full-scale WRRFs

The activated sludge wastewater treatment process has been thoroughly researched in more than 100 years, yet there are still operational challenges that have not been fully resolved. Such a challenge is the control of filamentous bulking caused by the overgrowth of certain filamentous bacteria. In this study, we tested different mitigation strategies to reduce filamentous bulking, caused by two common filamentous genera found in full-scale water resource recovery facilities (WRRF), Candidatus Microthrix and Candidatus Amarolinea. PAX dosing, ozone addition, hydrocyclone implementation, and the addition of nano-coagulants were tested as mitigation strategies in four parallel treatment lines in a full-scale WRRF over three consecutive years. Unexpectedly, the activated sludge settleability was not affected by any of the mitigation strategies. Some of the strategies appeared to have a strong mitigating effect on the two filamentous species. However, detailed analyses of the microbial communities revealed strong recurrent seasonal variations in all four lines, including the control line which masked the real effect. After removing the effect of the seasonal variation by using a time-series decomposition approach, it was clear that the filamentous bacteria were mostly unaffected by the mitigation strategies. Only PAX dosing had some effect on Ca. Microthrix, but only on one species, Ca. Microthrix subdominans, and not on the most common Ca. Microthrix parvicella. Overall, our study shows the importance of long-term monitoring of microbial communities at species level to understand the normal seasonal pattern to effectively plan and execute full-scale experiments. Moreover, the results highlight the importance of using parallel reference treatment lines when evaluating the effect of mitigation strategies in full-scale treatment plants.

Rapid absolute quantification of pathogens and ARGs by nanopore sequencing

Compositional nature of relative abundance data in the current standard microbiome studies limits microbial dynamics interpretations and cross-sample comparisons. Here, we demonstrate the first rapid (1-h sequencing) method coupling Nanopore metagenomic sequencing with cellular spike-in to facilitate the absolute quantification and removal assessment of pathogens and antibiotic resistance genes (ARGs) in wastewater treatment plants (WWTPs). Nanopore sequencing-based quantification results for both simple mock community and complex real environmental samples showed a high consistency with those from the widely-used Illumina and culture-based approaches. Implementing such method, we quantified 46 predominant putative pathogenic species, and 361 ARGs in three WWTP sample sets. Though high log removals of dominant pathogens (2.23 logs) and ARGs (1.98 logs) were achieved, complete removal of all pathogens and ARGs were not achieved. Noticeably, Mycobacterium spp., Clostridium_P perfringens, and Borrelia hermsii exhibited low removal, and 13 ARGs even increased in absolute abundance after the treatment. Our proposed approach manifested its profound ability in providing absolute quantitation information guiding wastewater-based epidemiological surveillance and quantitative risk assessment facilitating microbial hazards management.

Recent advances in understanding the ecology of the filamentous bacteria responsible for activated sludge bulking

Activated sludge bulking caused by filamentous bacteria is still a problem in wastewater treatment plants around the world. Bulking is a microbiological problem, and so its solution on species-specific basis is likely to be reached only after their ecology, physiology and metabolism is better understood. Culture-independent molecular methods have provided much useful information about this group of organisms, and in this review, the methods employed and the information they provide are critically assessed. Their application to understanding bulking caused by the most frequently seen filament in Japan, 'Ca. Kouleothrix', is used here as an example of how these techniques might be used to develop control strategies. Whole genome sequences are now available for some of filamentous bacteria responsible for bulking, and so it is possible to understand why these filaments might thrive in activated sludge plants, and provide clues as to how eventually they might be controlled specifically.

Candidatus Kaistella beijingensis sp. nov., Isolated from a Municipal Wastewater Treatment Plant, Is Involved in Sludge Foaming

Biological foaming (or biofoaming) is a frequently occurring problem in wastewater treatment plants (WWTPs) and is attributed to the overwhelming growth of filamentous bulking and foaming bacteria (BFB). Biological foaming has been intensively investigated, with BFB like Microthrix and Skermania having been identified from WWTPs and implicated in foaming. Nevertheless, studies are still needed to improve our understanding of the microbial diversity of WWTP biofoams and how microbial activities contribute to foaming. In this study, sludge foaming at the Qinghe WWTP of China was monitored, and sludge foams were investigated using culture-dependent and culture-independent microbiological methods. The foam microbiomes exhibited high abundances of Skermania, Mycobacterium, Flavobacteriales, and Kaistella. A previously unknown bacterium, Candidatus Kaistella beijingensis, was cultivated from foams, its genome was sequenced, and it was phenotypically characterized. Ca. K. beijingensis exhibits hydrophobic cell surfaces, produces extracellular polymeric substances (EPS), and metabolizes lipids. Ca. K. beijingensis abundances were proportional to EPS levels in foams. Several proteins encoded by the Ca. K. beijingensis genome were identified from EPS that was extracted from sludge foams. Ca. K. beijingensis populations accounted for 4 to 6% of the total bacterial populations in sludge foam samples within the Qinghe WWTP, although their abundances were higher in spring than in other seasons. Cooccurrence analysis indicated that Ca. K. beijingensis was not a core node among the WWTP community network, but its abundances were negatively correlated with those of the well-studied BFB Skermania piniformis among cross-season Qinghe WWTP communities. IMPORTANCE Biological foaming, also known as scumming, is a sludge separation problem that has become the subject of major concern for long-term stable activated sludge operation in decades. Biological foaming was considered induced by foaming bacteria. However, the occurrence and deterioration of foaming in many WWTPs are still not completely understood. Cultivation and characterization of the enriched bacteria in foaming are critical to understand their genetic, physiological, phylogenetic, and ecological traits, as well as to improve the understanding of their relationships with foaming and performance of WWTPs.

Prokaryotic viruses impact functional microorganisms in nutrient removal and carbon cycle in wastewater treatment plants

As one of the largest biotechnological applications, activated sludge (AS) systems in wastewater treatment plants (WWTPs) harbor enormous viruses, with 10-1,000-fold higher concentrations than in natural environments. However, the compositional variation and host-connections of AS viruses remain poorly explored. Here, we report a catalogue of ~50,000 prokaryotic viruses from six WWTPs, increasing the number of described viral species of AS by 23-fold, and showing the very high viral diversity which is largely unknown (98.4-99.6% of total viral contigs). Most viral genera are represented in more than one AS system with 53 identified across all. Viral infection widely spans 8 archaeal and 58 bacterial phyla, linking viruses with aerobic/anaerobic heterotrophs, and other functional microorganisms controlling nitrogen/phosphorous removal. Notably, Mycobacterium, notorious for causing AS foaming, is associated with 402 viral genera. Our findings expand the current AS virus catalogue and provide reference for the phage treatment to control undesired microorganisms in WWTPs.

Impact of light on anoxic/oxic reactors: performance, quorum sensing, and metagenomic characteristics

The effect of light has raised attention on wastewater treatment. However, little research has concentrated on the influences of light on activated sludge. In this study, the influences of light on the performance, quorum sensing (QS) and metagenomic characteristics of anoxic/oxic reactors were investigated. The reactor without light (AO1) showed higher total nitrogen (TN) removal (79.15 ± 1.69%) than the reactor with light (AO2) (74.54 ± 1.30%), and significant differences were observed. It was observed that light facilitated the production of protein-like and tryptophan-like substances by employing parallel factor analysis for extracellular polymeric substance (EPS), resulting in more EPS production in AO2, indicating light was beneficial to EPS production. The concentrations of N-acyl-homoserine lactones (AHLs) were various in the two reactors, so the AHLs-mediated QS behaviors in both reactors were also different. These results revealed that light significantly influenced nitrogen removal, EPS, and QS. Metagenomic analysis based on Tax4Fun demonstrated that light reduced the denitrification, stimulated the polysaccharide and protein biosynthesis pathways and down-regulated the AHLs synthesis pathway, resulting in lower TN removal, more EPS production, and lower AHLs concentrations. Based on the above, the likely mechanism was proposed for the influences of light on the reactor.

Insights into the microbial diversity and structure in a full-scale municipal wastewater treatment plant with particular regard to Archaea

Due to limited description of the role and diversity of archaea in WWTPs, the aim of the study was to analyze microbial community structures and diversities with particular regard to Archaea in the samples taken from different stages of the full-scale municipal wastewater treatment plant and effluent receiving water (upstream and downstream discharge point). Our study was focused on showing how the treatment processes influenced the Eubacteria and Archaea composition. Alpha and Beta diversity were used to evaluate the microbial diversity changes in the collected samples. Proteobacteria was the largest fraction ranging from 28% to 67% with 56% relative abundance across all samples. Archaea were present in all stages of WWTP ranged from 1 to 8%. Among the Archaea, two groups of methanogens, acetoclastic (Methanosarcina, Methanosaeta) and hydrogenotrophic methanogens (Methanospirillium, Methanoculleus, Methanobrevibacter) were dominant in the technological stages. The obtained results indicate that the treated wastewater did not significantly affect eubacterial and archaeal composition in receiving water. However, differences in richness, diversity and microbial composition of Eubacteria and Archaea between the wastewater samples taken from the primary and secondary treatment were observed.

Distribution and diversity of filamentous bacteria in wastewater treatment plants exhibiting foaming of Taihu Lake Basin, China

Foaming caused by filamentous bacteria in activated sludge (AS) is a common phenomenon in municipal wastewater treatment plants (WWTPs) in Taihu Lake Basin of South China. In this study, total bacterial and filamentous bacterial communities were comprehensively characterized in AS and foams from eight municipal WWTPs by high-throughput sequencing technology. Results showed that alpha diversities of total bacterial communities in foams were obviously lower than those in AS samples. The bacterial community structures were significantly different between WWTPs rather than sample types (AS vs. foam). For most WWTPs, the Actinobacteria phylum was highly enriched in foams and the most abundant genera in foams were common mycolata. Sixteen filamentous bacteria were identified against the improved bulking and foaming bacteria (BFB) database. Abundance and composition of BFB in different WWTPs and different sample types were significantly different. 'Nostocoida limicola' I Trichococcus and Microthrix were generally dominant in AS samples. The dominant BFB in foams were associated with Microthrix, Skermania, Gordonia, and Mycobacterium. A new Defluviicoccus spp. in cluster III was identified in severe and continuous foams. Moreover, dominant BFB in stable and continuous foams with light level in one typical WWTP were diverse, even, and dynamic. Bacterial co-occurrence network analysis implied that the bacterial community of AS was more sensitive to disturbance than that of foam.

Seasonal Dynamics of the Activated Sludge Microbiome in Sequencing Batch Reactors, Assessed Using 16S rRNA Transcript Amplicon Sequencing

Activated sludge is comprised of diverse microorganisms which remediate wastewater. Previous research has characterized activated sludge using 16S rRNA gene amplicon sequencing, which can help to address questions on the relative abundance of microorganisms. In this study, we used 16S rRNA transcript sequencing in order to characterize "active" populations (via protein synthesis potential) and gain a deeper understanding of microbial activity patterns within activated sludge. Seasonal abundances of individual populations in activated sludge change over time, yet a persistent group of core microorganisms remains throughout the year which are traditionally classified on presence or absence without monitoring of their activity or growth. The goal of this study was to further our understanding of how the activated sludge microbiome changes between seasons with respect to population abundance, activity, and growth. Triplicate sequencing batch reactors were sampled at 10-min intervals throughout reaction cycles during all four seasons. We quantified the gene and transcript copy numbers of 16S rRNA amplicons using real-time PCR and sequenced the products to reveal community abundance and activity changes. We identified 108 operational taxonomic units (OTUs) with stable abundance, activity, and growth throughout the year. Nonproliferating OTUs were commonly human health related, while OTUs that showed seasonal abundance changes have previously been identified as being associated with floc formation and bulking. We observed significant differences in 16S rRNA transcript copy numbers, particularly at lower temperatures in winter and spring. The study provides an analysis of the seasonal dynamics of microbial activity variations in activated sludge based on quantifying and sequencing 16S rRNA transcripts.IMPORTANCE Sequencing batch reactors are a common design for wastewater treatment plants, particularly in smaller municipalities, due to their low footprint and ease of operations. However, like for most treatment plants in temperate/continental climates, the microbial community involved in water treatment is highly seasonal and its biological processes can be sensitive to cold temperatures. The seasonality of these microbial communities has been explored primarily in conventional treatment plants and not in sequencing batch reactors. Furthermore, most studies often only address which organisms are present. However, the activated sludge microbial community is very diverse, and it is often hard to discern which organisms are active and which organisms are simply present. In this study, we applied additional sequencing techniques to also address the issues of which organisms are active and which organisms are growing. By addressing these issues, we gained new insights into seasonal microbial populations dynamics and activity patterns affecting wastewater treatment.

Candidatus Amarolinea and Candidatus Microthrix Are Mainly Responsible for Filamentous Bulking in Danish Municipal Wastewater Treatment Plants

Filamentous bulking is a common serious operational problem leading to deteriorated sludge settling that has long been observed in activated sludge biological wastewater treatment systems. A number of bacterial genera found therein possess filamentous morphology, where some have been shown to be implicated in bulking episodes (e.g., Ca. Microthrix), the impact of many others is still not clear. In this study we performed a survey of 17 Danish municipal wastewater treatment plants (WWTPs) with nutrient removal using 16S rRNA amplicon sequencing over a period of 13 years, where all known filamentous bacteria from 30 genera were analyzed. The filamentous community constituted on average 13 ± 6%, and up to 43% of total read abundance with the same genera common to all plants. Ca. Microthrix and several genera belonging to phylum Chloroflexi were among the most abundant filamentous bacteria. The effect of filamentous bacteria on sludge settling properties was analyzed using measurements of the diluted sludge volume index (DSVI). Strong positive correlations with DSVI were observed only for Ca. Microthrix and Ca. Amarolinea, the latter being a novel, recently characterized genus belonging to the phylum Chloroflexi. The bulking potential of other filamentous bacteria was not significant despite their presence in many plants. Low phylogenetic diversity was observed for both Ca. Microthrix and Ca. Amarolinea, making physiological characterization of individual species and potential development of control strategies more feasible. In this study we show that, despite the high diversity of filamentous phylotypes in Danish WWTPs, only few of them were responsible for severe bulking episodes.

The microbial community in filamentous bulking sludge with the ultra-low sludge loading and long sludge retention time in oxidation ditch

Sludge bulking is a major problem that restricts the development of the activated sludge process. The microbial community responsible for sludge bulking varies depending on water quality and operational conditions. This study analysed the microbial community of bulking sludge in oxidation ditch with ultra-low sludge loading and long sludge retention time using high-throughput sequencing. The study found that the relative abundance of bacterial genus Saprospiraceae_norank was the highest in bulking sludge, reaching 13.39-28.83%, followed by Comamonadaceae_unclassified, Ardenticatenia_norank and Tetrasphaera, with the relative abundance of 4.59-11.08%, 0.52-16.60% and 0.17-8.92% respectively. In contrast, the relative abundance of bacteria that easily caused sludge bulking including Microthrix (0.54-2.47%), Trichococcus (0.32-1.71%), Gordonia (0.14-1.28%), and Thiothrix (0.01-0.06%) were relatively low. Saprospiraceae_norank was predominant and induced sludge bulking in oxidation ditch. The relative abundance of fungal genus Trichosporon was the highest in bulking sludge, reaching 16.95-24.98%, while other fungal genera were Saccharomycetales_unclassified (5.59-14.55%), Ascomycota_norank (1.45-13.51%), Galactomyces (5.23-11.23%), and Debaryomyces (7.69-9.42%), whereas Trichosporon was the dominant fungal genus in bulking sludge. This study reported that excessive Saprospiraceae_norank can induce sludge bulking for the first time, which provides important knowledge to control sludge bulking.

How Urban Storm- and Wastewater Management Prepares for Emerging Opportunities and Threats: Digital Transformation, Ubiquitous Sensing, New Data Sources, and Beyond - A Horizon Scan

Ubiquitous sensing will create many opportunities and threats for urban water management, which are only poorly understood today. To identify the most relevant trends, we conducted a horizon scan regarding how ubiquitous sensing will shape the future of urban drainage and wastewater management. Our survey of the international urban water community received an active response from both the academics and the professionals from the water industry. The analysis of the responses demonstrates that emerging topics for urban water will often involve experts from different communities, including aquatic ecologists, urban water system engineers and managers, as well as information and communications technology professionals and computer scientists. Activities in topics that are identified as novel will either require (i) cross-disciplinary training, such as importing new developments from the IT sector, or (ii) research in new areas for urban water specialists, for example, to help solve open questions in aquatic ecology. These results are, therefore, a call for interdisciplinary research beyond our own discipline. They also demonstrate that the water management community is not yet prepared for the digital transformation, where we will experience a data demand, i.e. a "pull" of urban water data into external services. The results suggest that a lot remains to be done to harvest the upcoming opportunities. Horizon scanning should be repeated on a routine basis, under the umbrella of an experienced polling organization.

Comprehensive insights into the key components of bacterial assemblages in pharmaceutical wastewater treatment plants

Due to complexity and variety of pharmaceutical wastewater composition, little is known as for functionally important microflora of pharmaceutical wastewater treatment plants (pWWTPs). We compared bacterial composition and diversity of pWWTPs (27 sludge samples collected from 12 full-scale pWWTPs) with those of other industrial (iWWTPs) (27 samples) and municipal wastewater treatment plants (mWWTPs) (27 samples) through meta-analysis based on 16S rRNA gene amplicon sequencing, and identified putatively important organisms and their ecological correlations. Non-metric multidimensional scaling indicated that the pWWTPs, iWWTPs and mWWTPs showed distinctive differences in bacterial community composition (P < 1e-04), and the pWWTPs had significantly lower bacterial diversity than the mWWTPs (P < 1e-06). Thermotogae and Synergistetes phyla only strictly dominated in the pWWTPs, and 26, 30 and 6 specific genera were identified in the pWWTPs, mWWTPs and iWWTPs, respectively. Totally, 15 and 1300 OTUs were identified as core and occasional groups, representing 23.2% and 66.2% of the total read abundance of the pWWTPs, respectively. Permutational multivariate analysis of variance revealed that the bacterial components were clearly clustered corresponding to the types of pharmaceutical wastewater, and a total of 129 local specific OTUs were identified in the pWWTPs, among which anticancer antibiotics pWWTPs had the highest number of specific OTUs (40 ones). Co-occurrence network revealed that the species dominating in the same type of pWWTPs tended to co-occur much more frequently than theoretical random expectation. The results may extend our knowledge regarding the ecological status and correlation of the key microflora in pWWTPs.

Activated sludge bacterial communities of typical wastewater treatment plants: distinct genera identification and metabolic potential differential analysis

To investigate the differences in activated sludge microbial communities of different wastewater treatment plants (WWTPs) and understand their metabolic potentials, we sampled sludge from every biological treatment unit of 5 full-scale waste water treatment systems in 3 typical Chinese municipal WWTPs. The microbial communities and overall metabolic patterns were not only affected by influent characteristics but also varied between different biological treatment units. Distinct genera in different wastewater treatment systems were identified. The important microorganisms in domestic sewage treatment systems were unclassified SHA-20, Caldilinea, Dechloromonas, and unclassified genera from Rhodospirilaceae and Caldilineaceae. The important microorganisms in dyeing wastewater treatment systems were Nitrospira, Sphingobacteriales, Thiobacillus, Sinobacteraceae and Comamonadaceae. Compared with the obvious differences in microbial community composition, the metabolic potential showed no significant differences.

High-Resolution Temporal and Spatial Patterns of Virome in Wastewater Treatment Systems

Wastewater treatment plants (WWTPs) are considered reservoirs of viruses, but the diversity and dynamic changes of viruses are not well understood. In this study, we recovered 8478 metagenomic viral contigs (mVCs; >5 kb) from two WWTPs (Shatin, 2806; Shek Wu Hui, 5672) in Hong Kong. Approximately 60% of the mVCs were poorly covered (<35% of genes in identified mVCs) by the current NCBI and IMG/VR viral databases. The temporal profile of the newly identified mVCs among 98 Shatin AS samples collected monthly (for approximately 9 years) revealed the presence of periodic dynamics at an interval of approximately one year (341 days). The spatial distribution pattern of the virome in the wastewater treatment systems showed that shared viral clusters (viral populations categorized based on shared gene content and network analysis) can be globally found among similar samples of wastewater treatment systems, indicating the presence of core viral communities among geographically isolated wastewater treatment systems. These results not only supplemented the current virome database of engineered systems but also, to some extent, expanded the understanding of long-term cyclical development and spatial distributions of viral communities in wastewater treatment systems.

Diversity-Function Relationships in Natural, Applied, and Engineered Microbial Ecosystems

The connection between ecosystem function and taxonomic diversity has been of interest and relevance to macroecologists for decades. After many years of lagging behind due to the difficulty of assigning both taxonomy and function to poorly distinguishable microscopic cells, microbial ecology now has access to a suite of powerful molecular tools which allow its practitioners to generate data relating to diversity and function of a microbial community on an unprecedented scale. Instead, the problem facing today's microbial ecologists is coupling the ease of generation of these datasets with the formulation and testing of workable hypotheses relating the diversity and function of environmental, host-associated, and engineered microbial communities. Here, we review the current state of knowledge regarding the links between taxonomic alpha- and beta-diversity and ecosystem function, comparing our knowledge in this area to that obtained by macroecologists who use more traditional techniques. We consider the methodologies that can be applied to study these properties and how successful they are at linking function to diversity, using examples from the study of model microbial ecosystems, methanogenic bioreactors (anaerobic digesters), and host-associated microbiota. Finally, we assess ways in which our newly acquired understanding might be used to manipulate diversity in ecosystems of interest in order to improve function for the benefit of us or the environment in general through the provision of ecosystem services.