Bacterial community structure in geographically distributed biological wastewater treatment reactors

The effects of headspace volume reactor on the microbial community structure during fermentation processes for volatile fatty acid production

The transition from traditional wastewater treatment plants to biorefineries represents an environmentally and economically sustainable approach to extracting valuable compounds from waste. Sewage sludge produced from wastewater treatment is incinerated or disposed of in specific landfills. Repurposing this waste material to recover valuable resources could help lower disposal costs and reduce environmental impact by producing other beneficial polymers. Microorganisms present in the sewage sludge can ferment organic pollutants, producing volatile fatty acids (VFA), precursors for biopolymers that could be used as an alternative to petroleum-derived plastics. To boost VFA production during sewage sludge fermentation, it is necessary to understand the operating microbial community and its metabolic capacities in anaerobic conditions. This study presents the influence of the headspace volume on the microbial community and the VFA production to define the best operational parameters in a 225 L pilot plant fermenter. The wasted sewage sludge was withdrawn from an oxic-settling-anaerobic plant that collected wastewater from the canteen and dormitory of the UNIPA Campus (Palermo University, Italy) and incubated using a 40% and a 60% headspace volume. The microbial community was analysed before and after the fermentation process through metataxonomic analysis, and VFA yields were determined by gas chromatography analysis. Our results showed that the 40% headspace volume induced a tenfold higher VFA production than the 60% headspace volume, modulating the microbial community's efforts to establish a VFA-producing factory. Notably, at 40% headspace, the relative abundance of bacteria, like Proteobacteria, Firmicutes, Actinobacteria, and Chloroflexi, significantly increased, as well as the relative abundance of Bacteroidetes and Verrucomicrobia decreased during the fermentation process. This result is consistent with the selection of efficient VFA-producing bacteria that lead to increased VFA yields that are not obtained at 60% headspace. Thus, reducing headspace is a promising strategy that can be implemented, even in full-scale plants, to optimise the wastewater reuse process and maximise VFA production to produce bioplastics, like polyhydroxyalkanoate, for the transition from linear wastewater treatment plants to circular biorefineries.

Microbiological toxicity tests using standardized ISO/OECD methods-current state and outlook

Microbial toxicity tests play an important role in various scientific and technical fields including the risk assessment of chemical compounds in the environment. There is a large battery of normalized tests available that have been standardized by ISO (International Organization for Standardization) and OECD (Organization for Economic Co-operation and Development) and which are worldwide accepted and applied. The focus of this review is to provide information on microbial toxicity tests, which are used to elucidate effects in other laboratory tests such as biodegradation tests, and for the prediction of effects in natural and technical aqueous compartments in the environment. The various standardized tests as well as not normalized methods are described and their advantages and disadvantages are discussed. In addition, the sensitivity and usefulness of such tests including a short comparison with other ecotoxicological tests is presented. Moreover, the far-reaching influence of microbial toxicity tests on biodegradation tests is also demonstrated. A new concept of the physiological potential of an inoculum (PPI) consisting of microbial toxicity tests whose results are expressed as a chemical resistance potential (CRP) and the biodegradation adaptation potential (BAP) of an inoculum is described that may be helpful to characterize inocula used for biodegradation tests. KEY POINTS: • Microbial toxicity tests standardized by ISO and OECD have large differences in sensitivity and applicability. • Standardized microbial toxicity tests in combination with biodegradability tests open a new way to characterize inocula for biodegradation tests. • Standardized microbial toxicity tests together with ecotoxicity tests can form a very effective toolbox for the characterization of toxic effects of chemicals.

Impact of long-term temperature shifts on activated sludge microbiome dynamics and micropollutant removal

Micropollutants removal efficiency strongly vary across different aerobic wastewater treatment plants, resulting in their frequent detection in surface and ground waters. Seasonal temperature variation is a major factor influencing plant performance, but it is still unclear how prolonged periods of temperature change impact microbiome and micropollutant biotransformation. This work investigates the effect of long-term temperature variation on the microbial dynamics in an activated sludge system, and the impact on micropollutant biotransformation. Sequencing batch reactors were used as model system and 4-40 °C temperature range was studied. 16S rRNA amplicon sequencing showed that temperature drives microbial structure (gDNA) and activity (RNA), rather than time, and this was stronger below 15 °C and above 25 °C. The microbial community was richest and more diverse at 20 °C, while rarer and more specific taxa became predominant over time, at more extreme temperatures. This suggested that less abundant taxa might be responsible for maintaining the biotransformation capability in the activated sludge at extreme temperatures. Micropollutant biotransformation rates mostly deviated from the classic Arrhenius model below 15 °C and above 25 °C, indicating that prolonged exposure to temperature changes leads to temperature-induced taxonomic shifts, resulting in the emerging of different sets of biotransformation pathways over different temperature ranges.

Competitive enrichment of comammox Nitrospira in floccular sludge

The discovery of complete ammonium oxidation (comammox) has subverted the traditional perception of two-step nitrification, which plays a key role in achieving biological nitrogen removal from wastewater. Floccular sludge-based treatment technologies are being applied at the majority of wastewater treatment plants in service where detection of various abundances and activities of comammox bacteria have been reported. However, limited efforts have been made to enrich and subsequently characterize comammox bacteria in floccular sludge. To this end, a lab-scale sequencing batch reactor (SBR) in the step-feeding mode was applied in this work to enrich comammox bacteria through controlling appropriate operational conditions (dissolved oxygen of 0.5 ± 0.1 g-O2/m3, influent ammonium of 40 g-N/m3 and uncontrolled longer sludge retention time). After 215-d operation, comammox bacteria gradually gained competitive advantages over counterparts in the SBR with a stable nitrification efficiency of 92.2 ± 2.2 %: the relative abundance of Nitrospira reached 42.9 ± 1.3 %, which was 13 times higher than that of Nitrosomonas, and the amoA gene level of comammox bacteria increased to 7.7 ± 2.1 × 106 copies/g-biomass, nearly 50 times higher than that of conventional ammonium-oxidizing bacteria. The enrichment of comammox bacteria, especially Clade A Candidatus Nitrospira nitrosa, in the floccular sludge led to (i) apparent affinity constants for ammonium and oxygen of 3.296 ± 0.989 g-N/m3 and 0.110 ± 0.004 g-O2/m3, respectively, and (ii) significantly low N2O and NO production, with emission factors being 0.136 ± 0.026 % and 0.023 ± 0.013 %, respectively.

Optimization of nitrogen removal and microbial mechanism of a hydrogen-based membrane biofilm reactor

The hydrogen-based membrane biofilm reactor (H2-MBfR) is an emerging biological nitrogen removal technology characterized by high efficiency, energy-saving capability, and environmental friendliness. The technology achieves denitrification and denitrogenation of microorganisms by passing hydrogen as an electron donor from inside to outside through the hollow fibre membrane module, and eventually the hydrogen reachs the biofilm attached to the surface of the fibre membrane. H2-MBfR has obtained favourable outcomes in the treatment of secondary biochemical effluent and low concentration nitrogen polluted water source. The experiment was optimized by s single-factor testing and response surface methodology-based optimization (RSM), and the optimal operational conditions were obtained as follows: an influent flow rate of 2 mL/min, hydrogen pressure of 0.04 MPa, and influent nitrate concentration of 24.29 mg/L. Under these conditions, a high nitrate removal rate of 98.25% was achieved. In addition, Proteobacteria and Bacteroidetes were the dominant bacteria in all stages, and the genus Hydrogenophaga was sufficiently enriched, occurring at 13.0%-49.0% throughout the reactor operation. Furthermore, the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway for nitrate reduction and inorganic carbon utilization by microorganisms in the H2-MBfR was explored through comparison with the KEGG database. The results provided a mechanistic explanation for the denitrification and carbon sequestration capacity of the H2-MBfR.

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.

Sulfur autotrophic denitrification as an efficient nitrogen removals method for wastewater treatment towards lower organic requirement: A review

The sulfur autotrophic denitrification (SADN) process is an organic-free denitrification process that utilizes reduced inorganic sulfur compounds (RISCs) as the electron donor for nitrate reduction. It has been proven to be a cost-effective and environment-friendly approach to achieving carbon neutrality in wastewater treatment plants. However, there is no consensus on whether SADN can become a dominant denitrification process to treat domestic wastewater or industrial wastewater if organic carbon is desired to be saved. Through a comprehensive summary of the SADN process and extensive discussion of state-of-the-art SADN-based technologies, this review provides a systematic overview of the potential of the SADN process as a sustainable alternative for the heterotrophic denitrification (HD) process (organic carbons as electron donor). First, we introduce the mechanism of the SADN process that is different from the HD process, including its transformation pathways based on different RISCs as well as functional bacteria and key enzymes. The SADN process has unique theoretical advantages (e.g., economy and carbon-free, less greenhouse gas emissions, and a great potential for coupling with novel autotrophic processes), even if there are still some potential issues (e.g., S intermediates undesired production, and relatively slow growth rate of sulfur-oxidizing bacteria [SOB]) for wastewater treatment. Then we present the current representative SADN-based technologies, and propose the outlooks for future research in regards to SADN process, including implement of coupling of SADN with other nitrogen removal processes (e.g., HD, and sulfate-dependent anaerobic ammonium oxidation), and formation of SOB-enriched biofilm. This review will provide guidance for the future applications of the SADN process to ensure a robust-performance and chemical-saving denitrification for wastewater treatment.

Analysis of Microbial Communities in Membrane Biofilm Reactors Using a High-Density Microarray

Membrane biofilm reactors (MBfRs) have attracted more and more attention in the field of wastewater treatment due to their advantages of high mass transfer efficiency and low-carbon emissions. There are many factors affecting their nitrogen removal abilities, such as operation time, electron donor types, and operation modes. The operation time is directly related to the growth status of microorganisms, so it is very important to understand the effect of different operation times on microbial composition and community succession. In this study, two parallel H₂-based MBfRs were operated, and differences in microbial composition, community succession, and NO₃^--N removal efficiency were investigated on the 30th day and the 60th day of operation. The nitrogen removal efficiency of MBfRs with an operation time of 60 days was higher than that of MBfRs with an operation time of 30 days. Proteobacteria was the dominant phylum in both MBfRs; however, the composition of the microbial community was quite different. At the class level, the community composition of Proteobacteria was similar between the two MBfRs. Alphaproteobacteria was the dominant class in MBfR, and Betaproteobacteria and Gammaproteobacteria were also in high proportion. Combined with the analysis of microbial relative abundance and concentration, the similarity of microbial distribution in the MBfRs was very low on day 30 and day 60, and the phylogenetic relationships of the top 50 dominant universal bacteria and Proteobacteria were different. Although the microbial concentration decreased with the extension of the operation time, the microbial abundance and diversity of specific functional microorganisms increased further. Therefore, the operation time had a significant effect on microbial composition and community succession.

High-Density Microarray Analysis of Microbial Community Structures in Membrane Bioreactor at Short Sludge Retention Time

Membrane bioreactors (MBR) have become prevalent in wastewater treatment because of their high effluent quality and low sludge generation. Sludge retention time (SRT) is an important parameter in the operation of MBR, and it has a direct effect on the microbial community. In this study, microarrays were used to analyze the microbial communities of three different MBRs at short SRTs. The results showed that MBR at SRT 5 days (CS5) has the highest operational taxonomic units (OTUs) richness, but the lowest diversity and uniformity compared to SRT 3 days at continuous CS3 and the sequencing batch (SS3). Proteobacteria were the dominant phylum of three reactors. Bacteroidetes were the second dominant phylum in MBRs at the continuous model, instead of Actinobacteria at the sequencing model. At the class level, the dominant group of Proteobacteria exhibited a remarkable difference between the three MBRs. γ-Proteobacteria was the dominant group in CS5 and CS3, while α-Proteobacteria was the main group in SS3. The samples from the three MBRs had similar compositions of α-, β- and δ-Proteobacteria. However, γ-Proteobacteria showed different community compositions at the order level between the three MBRs. Enterobacteriales were the dominant group in CS5 and CS3, while Pseudomonadales were the dominant group in SS3. The bacterial community concentration of SRT 5 days was generally higher than that of the other two MBRs. The community composition of CS5 was significantly different from that of CS3 and SS3, and the phylogenetic relationships of the three MBRs were relatively different.

Effect of aeration modes on nitrogen removal and N2O emission in the partial nitrification and denitrification process for landfill leachate treatment

The anoxic/multi-aerobic process is widely applied for treating landfill leachate with low carbon to nitrogen ratio. In this study, the effect of two aeration modes in the aerobic phase, i.e. decreasing dissolved oxygen (DO) and increasing DO, on nitrogen removal and N₂O emission in the process were systematically compared. The results demonstrate that the aerobic phase with increasing DO mode has a positive effect on improved total nitrogen removal (78 %) under the COD/N ratio as low as 3.45 and minimized N₂O emission. DO concentration higher than 1.5 mg/L in the aerobic phase reduced nitrogen removal and led to a significant high N₂O emission in the process. Complete nitrite denitrification in the anoxic phase correlated with minimized N₂O emission. Under efficient nitrogen removal stage, N₂O emission factor was 2.4 ± 1.0 % of the total incoming nitrogen. Microbial analysis revealed that increasing DO mode increased the abundance of ammonia oxidizing bacteria and denitrifiers.

Guided by the principles of microbiome engineering: Accomplishments and perspectives for environmental use

Although the accomplishments of microbiome engineering highlight its significance for the targeted manipulation of microbial communities, knowledge and technical gaps still limit the applications of microbiome engineering in biotechnology, especially for environmental use. Addressing the environmental challenges of refractory pollutants and fluctuating environmental conditions requires an adequate understanding of the theoretical achievements and practical applications of microbiome engineering. Here, we review recent cutting-edge studies on microbiome engineering strategies and their classical applications in bioremediation. Moreover, a framework is summarized for combining both top-down and bottom-up approaches in microbiome engineering toward improved applications. A strategy to engineer microbiomes for environmental use, which avoids the build-up of toxic intermediates that pose a risk to human health, is suggested. We anticipate that the highlighted framework and strategy will be beneficial for engineering microbiomes to address difficult environmental challenges such as degrading multiple refractory pollutants and sustain the performance of engineered microbiomes in situ with indigenous microorganisms under fluctuating conditions.

Phage-host interactions: The neglected part of biological wastewater treatment

In wastewater treatment plants (WWTPs), the stable operation of biological wastewater treatment is strongly dependent on the stability of associated microbiota. Bacteriophages (phages), viruses that specifically infect bacteria and archaea, are highly abundant and diverse in WWTPs. Although phages do not have known metabolic functions for themselves, they can shape functional microbiota via various phage-host interactions to impact biological wastewater treatment. However, the developments of phage-host interaction in WWTPs and their impact on biological wastewater treatment are overlooked. Here, we review the current knowledge regarding the phage-host interactions in biological wastewater treatment, mainly focusing on the characteristics of different phage populations, the phage-driven changes in functional microbiota, and the potential driving factors of phage-host interactions. We also discuss the efforts required further to understand and manipulate the phage-host interactions in biological wastewater treatment. Overall, this review advocates more attention to the phage dynamics in WWTPs.

Efficient degradation of naproxen in a three dimensional biofilm electrode magnetism reactor (3DBEMR): Removal performance and microbial community

A three-dimensional biofilm electrode magnetism reactor (3DBEMR) was constructed to removal naproxen (NPX). This study evaluated 3DBEMR performance in removal of refractory NPX, while also discussing the effect of the electro-magnetic superposition on microbial community by high throughput sequencing. Results indicated that 3DBEMR's average removal rate for NPX stood at 88.36%, representing an increase by 75.24%, 65.03% and 12.36%, respectively, compared to 3DBR (Three-Dimensional Biofilm Reactor), 3DBMR (Three-Dimensional Biofilm Magnetism Reactor) and 3DBER (Three-Dimensional Biofilm Electrode Reactor). This was attributed to the influence of electro-magnetic adsorption, electro-oxidaton/catalysis, and electro-magnetic biodegradation. Another major contributing factor to NPX removal was the presence in 3DBEMR of high-abundance genera such as Rhodobacter, Porphyrobacter, Methyloversatilis, Sphingopyxis,Bosea, Singulisphaera, Sphingomonas. Therefore, the 3DBEMR was successfully demonstrated to be a flexible and effective technique in NPX degradation, which would help to better understand the effect of superposition of electric and magnetic fields on microbial community.

Microbial community structure analysis in a hybrid membrane bioreactor via high-throughput sequencing

Compared to the suspended culture (sludge) of a conventional bioreactor, hybrid membrane bioreactors (HMBRs) are more effective at removing pollutants owing to the addition of fillers addition of fillers that facilitate biofilm formation. However, the microbial community structure and composition in an HMBR remain unclear. We ran three laboratory-scale HMBRs at room temperature under different sludge retention times (SRTs; 10 d, 20 d, and 30 d) to compare the microbial diversity and community structure among the membrane surface, suspended filler surface, and mixed liquor using high-throughput sequencing. The results showed that SRT can markedly affect microbial community structure in the HMBR, and different trends appeared in the three functional units. The largest number of mutual operational taxonomic units was found in the activated sludge mixture and suspended carrier with an SRT of 20 d and 30 d. Species belonging to Proteobacteria in the 10 d SRT group had the greatest contribution to between-group differences. A longer SRT could mitigate membrane fouling by decreasing the relative abundance of Thauera and Sphaerotilus attached on the membrane surface. Comamonadaceae, a family of denitrifying bacteria, offer high denitrification potential for bioreactors operating under a long SRT.

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.

Core activated sludge communities are influenced little by immigration: Case study of a membrane bioreactor plant

Microbial immigrants arriving with influent wastewater may influence activated sludge (AS) ecosystems. However, the extent to which immigration impacts AS communities is still debated. To explore the intensity of immigration impact, we used sequencing technology to track the raw wastewater and AS communities from a membrane bioreactor plant over a 12-month period. We first distinguished core populations from peripheral ones in both raw wastewater and AS based on their occurrence frequency and abundance. The results showed that core OTUs (≥ 80% occurrence frequency) made up a large fraction (> 90%) of total sequences, while peripheral OTUs composed the majority of all detected OTUs but merely occupied a few sequences. A significant difference in core communities between the influent and AS was found, as well as between the compositions of core and peripheral populations. Additionally, the persistent functional bacteria of AS, although not numerically dominant, accounted for 96.24% of the total sequences related to nutrient turnover, suggesting the presence of a small number of longstanding and core functional bacteria in the AS ecosystem. Importantly, 64% of the 5188 OTUs in AS, which accounted for 91.51% of the sequences, exhibited positive growth rates, which suggested that their apparent abundances were due to growth within the plant, not from immigration. Taken together, these results demonstrated that the impact of influent populations on core AS communities was limited. Overall, this work provides quantitative insights into the impact of immigration, which is expected to advance our understanding of the AS community assembly.

A value-added step towards promoting the serviceability of fluidized bed bioreactor in treating wastewater with low carbon to nitrogen ratio

Reusing microplastics and zeolite waste as free ammonia (FA)-mitigating carrier particle was proven a value-added step towards promoting the serviceability of fluidized bed bioreactor (FBBR) in treating wastewater with a low carbon to nitrogen ratio (i.e. C/N <3.0) in this study. Ammonia (NH₄⁺) adsorption property capacitates zeolite as an FA mitigator. The microplastics and reused zeolite were processed into reused-zeolite/microplastic composite particle (RZ), whose merit of FA mitigation was fully developed via an optimally thermal modification to process modified-zeolite/microplastic particle (MZ). The 171-day biological nutrient removal (BNR) performance in a single integrated fluidized bed bioreactor (SIFBBR) shows that the bioreactor with MZ particle (SIFBBR-MZ) achieved nitrogen removal efficiency 10.0% higher than the bioreactor with RZ particle (SIFBBR-RZ) over the enhanced short-cut nitrification and denitrification. Analysis of microbial community structure unveils that the long-term lower FA inhibition favored more significant ammonia-oxidizing bacteria (AOB) enrichment and acclimated specific MZ biofilm predominant by nitrite (NO₂^-) denitrifier, contributing to the outperformance in nitrogen removal. Apart from fluidization energy conservation, the techno-economic analysis confirms that using MZ as an FA-mitigating carrier could be of great benefit for FBBR system: realizing waste utilization, reducing carbon addition and alleviating sludge treatment.

Simultaneous nitrate and dissolved organic matter removal from wastewater treatment plant effluent in a solid-phase denitrification biofilm reactor

In the present study, an up-flow solid-phase denitrification biofilm reactor (US-DBR) was established for simultaneous nitrate and dissolved organic matter (DOM) removal from wastewater treatment plant effluent. After 100 days operation, the nitrate and COD removal efficiencies were high of 97% and 80%, respectively. According to EEM-FRI analysis, aromatic and tryptophan protein-like, humic-like and fulvic acid-like substances were identified in DOM. Additionally, protein-like substances in DOM components were much easier transformed as carbon source for denitrification. Moreover, protein secondary structure of DOM changed significantly due to the biodegradation and microorganisms metabolic process. High-throughput sequencing analysis implied that Simplicispira, Diaphorobacter, Hydrogenophaga, Pseudoxanthmonas and Stenotrophomonas were the dominate genera in the whole of US-DBR, that were responsible for the removal of nitrate, organics and degradation of solid carbon source, respectively. This study provided a further biological basis about practical application of solid-phase denitrification for simultaneously remove nitrate and organic matter.

Disentangling Community Structure of Ecological System in Activated Sludge: Core Communities, Functionality, and Functional Redundancy

The microbial ecosystems of the sludge were characterized in terms of the core community structure, functional pathways, and functional redundancy through Illumina MiSeq sequencing and PICRUSt analysis on the activated sludge (AS) samples from an extended activated aeration process. Based on the identified OTU distribution, we identified 125 core community genera, including 3 abundant core genera and 21 intermittent abundant core genera. Putative genera Nitrosomonas, Nitrotoga, Zoogloea, Novosphingobium, Thermomonas, Amaricoccus, Tetrasphaera, Candidatus Microthrix, and Haliscomenobacter, which are associated with functions of nitrifying, denitrifying, phosphorus accumulating, and bulking and foaming, were found to present as the core community organisms in the AS sampled from the conventional extended aeration AS processes. The high-abundant nitrogen metabolic pathways were associated with nitrate reduction to ammonium (DNRA and ANRA), denitrification, and nitrogen fixation, while the ammonia oxidation-related genes (amo) were rarely annotated in the AS samples. Strict functional redundancy was not found with the AS ecosystem as it showed a high correlation between the community composition similarity and function similarity. In addition, the classified dominant core genera community was found to be sufficient to characterize the functionality of AS, which could invigorate applications of 16S rDNA MiSeq sequencing and PICRUSt for the prediction of functions of AS ecosystems.

Bacterial community and environmental factors associated to rivers runoff and their possible impacts on coral reef conservation

Rivers potentially conduct important components as result of anthropogenic stressors for coral reefs. Molecular techniques are increasingly being used for monitoring biological and chemical monitoring of rivers and reefs. Here, we use PhyloChips™ to process surface water samples collected along two rivers and associated reefs in an environmental protection area in northeastern Brazil. Our results indicate that a significant part of Operational Taxonomic Units (OTUs) identified were able to survive the transition from freshwater to seawater, several of them belonging to genera implicated in human pathogenesis. The BBC:A ratio and functional prediction suggests that both study rivers are subject to fecal contamination and xenobiotics input and that the bacterial communities were more homogeneous in these environments. We suggest that protection actions adopted for reefs should be broadly extended to the surrounding environment, and that other bacterial group (besides cultivable coliforms) should be included in routine water quality monitoring.

Nitrifying and Denitrifying Microbial Communities in Centralized and Decentralized Biological Nitrogen Removing Wastewater Treatment Systems

Biological nitrogen removal (BNR) in centralized and decentralized wastewater treatment systems is assumed to be driven by the same microbial processes and to have communities with a similar composition and structure. There is, however, little information to support these assumptions, which may impact the effectiveness of decentralized systems. We used high-throughput sequencing to compare the structure and composition of the nitrifying and denitrifying bacterial communities of nine onsite wastewater treatment systems (OWTS) and one wastewater treatment plant (WTP) by targeting the genes coding for ammonia monooxygenase (amoA) and nitrous oxide reductase (nosZ). The amoA diversity was similar between the WTP and OWTS, but nosZ diversity was generally higher for the WTP. Beta diversity analyses showed the WTP and OWTS promoted distinct amoA and nosZ communities, although there is a core group of N-transforming bacteria common across scales of BNR treatment. Our results suggest that advanced N-removal OWTS have microbial communities that are sufficiently distinct from those of WTP with BNR, which may warrant different management approaches.

Characterization of antibiotic resistance genes and bacterial community in selected municipal and industrial sewage treatment plants beside Poyang Lake

Sewage treatment plants (STPs) are significant reservoirs of antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB). Municipal STPs (MSTPs) and industrial STPs (ISTPs) are the two most important STP types in cities. In this study, the ARGs, mobile genetic elements (MGEs), and bacterial communities of selected STPs, including two MSTPs and one ISTP, in the vicinity of Poyang Lake were comprehensively investigated through high-throughput qPCR and high-throughput Illumina sequencing. The results showed that the profiles of ARGs, MGEs and bacteria differed between the ISTP and the two MSTPs, most likely due to differences in influent water quality, such as the Pb that characterized in the ISTP's influent. The longer hydraulic retention times (HRTs) of the two MSTPs than of the ISTP may also have accounted for the different profiles. Thus, a prolonged HRT in the CASS process seems to allow a more extensive removal of ARGs and bacteria in ISTPs with similar treatment process. By providing comprehensive insights into the characteristics of ARGs, MGEs and the bacterial communities of the selected MSTPs and ISTP, our study provides a scientific basis for controlling the propagation and diffusion of ARGs and ARB in different types of STPs.

Improved membrane sequencing batch reactor: effect of carbon and nitrogen volumetric loading rate on dephosphatation

A lab-scale anaerobic-anoxic-aerobic membrane bioreactor (A₂NO-MBR) fed with synthetic wastewater was operated to investigate the impact of influent carbon and nitrogen volumetric loading rate (VLR) on dephosphatation, and the corresponding influent concentration was 100-300 mg L^-1 (COD), 24-50 mg L^-1 (NH₄⁺-N) and 4.8-6.0 mg L^-1 (TP), respectively. The results demonstrated that carbon VLR had a negligible effect on the COD removal with effluent below 50 mg L^-1, and high and stable removal capacity for phosphorus were also obtained, regardless of carbon VLR change. Whereas TN removal efficiency was positively correlated with carbon VLR reduction, and lower carbon VLR produced a negative effect on TN removal. In addition, since nitrate served as an electron acceptor for denitrifying phosphorus removal (DPR), a significant effect on nitrogen and phosphorus removal was observed with different nitrogen VLR. The TN and TP removal efficiency was 68.30 ± 1.36%, 70.70 ± 1.23%, 45.19 ± 1.72% and 41.63 ± 3.09%, 98.14 ± 0.53%, 53.34 ± 2.68% with influent nitrogen VLR of 0.024 ± 0.001, 0.034 ± 0.001 and 0.045 ± 0.001 kg-N/(m³ d), respectively. Moreover, bacterial community structure of sludge samples in Run I and V from anaerobic-anoxic-aerobic-SBR (named A₂OSBR_1 and A₂OSBR_2) and membrane bioreactor (named N-MBR_1 and N-MBR_2) revealed that Candidatus_Accumulibacter was the most dominant genus in A₂OSBR_1 (21.50%) and A₂OSBR_2 (18.98%). The relative lower carbon VLR favoured the enrichment of Saprospiraceae, which was related with DPR, with the proportion of 9.31% and 14.61% in A₂OSBR_1 and A₂OSBR_2. Besides, Nitrospira and Nitrosomonas with proportions of 11.14%, 5.38% in N-MBR_1 and 10.72%, 6.77% in N-MBR_2 were observed, which were likely responsible for the nearly complete nitrification.

Advanced treatment of coal chemical reverse osmosis concentrate with three-stage MABR

The issue of reverse osmosis concentrate (ROC) has attracted significant attention due to its complex and toxic constituents under high salinity conditions. In this work, a three-stage membrane-aerated biofilm reactor (MABR) system was constructed to treat such wastewater without an external carbon source. The effects of operating conditions including aeration pressure, reflux ratio, temperature and hydraulic retention time on the removal performance of the integrated system were evaluated and optimized. Under the optimal operating parameters, the removal efficiencies of COD, NH4 +-N, NO3 --N, and TN reached 69.36%, 80.95%, 54.55%, and 54.36%, respectively. Three-dimensional fluorescence analysis indicated that humic acid was mostly removed from raw water. Moreover, microbial diversity analysis indicated that the microbial community structure of each reactor could be individually modulated to exert different functions and enhance the system performance. The integrated MABR system exhibits great feasibility and potential for the advanced treatment of coal chemical ROC.

Tuning up microbiome analysis to monitor WWTPs' biological reactors functioning

Wastewater treatment plants (WWTPs) are necessary to protect ecosystems quality and human health. Their function relies on the degradation of organic matter and nutrients from a water influent, prior to the effluent release into the environment. In this work we studied the bacterial community dynamics of a municipal WWTP with a membrane bioreactor through 16S rRNA gene sequencing. The main phyla identified in the wastewater were Proteobacteria, Bacteroidetes, Chloroflexi, Planctomycetes and Actinobacteria. The WWTP is located in Spain and, like other studied WWTP in temperate climate zones, the temperature played a major role in community assembly. Seasonal community succession is observed along the two years sampling period, in addition to a continual annual drift in the microbial populations. The core community of the WWTP bioreactor was also studied, where a small fraction of sequence variants constituted a large fraction of the total abundance. This core microbiome stability along the sampling period and the likewise dissimilarity patterns along the temperature gradient makes this feature a good candidate for a new process control in WWTPs.

Efficient municipal wastewater treatment by oxidation ditch process at low temperature: Bacterial community structure in activated sludge

Temperature is a key element affecting the activity of microorganisms in activated sludge. Low water temperature generally leads to decreasing wastewater treatment efficiency and destroying sludge settleability. In this study, activated sludge samples from a municipal wastewater treatment plant (WWTP) implementing oxidation ditch process was used to investigate the bacterial community characteristics of a system that operates well in a cold region (Xinjiang, China) by high-throughput 16S rRNA gene sequencing. The results showed that the influent temperature was 7-12 °C in winter and 13-17 °C in summer, while the sludge volume index (SVI) of samples was between 51 and 74 mL/g. The average removal efficiencies for chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), suspended solid (SS), ammonia nitrogen (NH₄⁺-N), total nitrogen (TN), and total phosphorus (TP) were 94%, 95%, 95%, 91%, 73% and 89%, respectively. The bacteria were distributed in 32 phyla and 559 genera. The dominant phyla were Proteobacteria (28.85-48.45%), Bacteroidetes (20.00-31.22%), Chloroflexi (3.59-12.23%), Actinobacteria (1.58-15.54%) and Firmicutes (1.38-10.49%). The dominant genera were Saprospiraceae_norank (4.41-12.23%), Comamonadaceae_unclassified (3.82-8.83%), Anaerolineaceae_norank (1.39-9.35%), Dokdonella (1.13-11.26%), Candidatus_Microthrix (0.26-7.50%), Flavobacterium (0.32-8.14%), Ferribacterium (0.36-5.19%) and Nitrospira (0.084-5.37%), which were different from those found in warm-region WWTPs. Contrary to previous studies, the relative abundance of ammonia-oxidizing bacteria (AOB; Nitrosomonas and Nitrosomonadaceae) and nitrite-oxidizing bacteria (NOB; Nitrospira) increased when the temperature decreased. The successful operation of this WWTP suggests that cold-region WWTPs can achieve good pollutants removal efficiency by simultaneously maintaining an ultra-low sludge load and high dissolved oxygen concentration in the oxidation ditch. The findings of this study provide fundamental knowledge required for an efficient and stable operation of WWTPs in cold regions.

Correlations of nitrogen removal and core functional genera in full-scale wastewater treatment plants: Influences of different treatment processes and influent characteristics

The denitrification process is crucial for biological nitrogen removal in wastewater treatment plants (WWTPs). In this study, the nitrogen removal efficiency in full-scale WWTPs with different treatment processes and influent characteristics was investigated. The results indicated that the average total nitrogen removal rate (NRR) and denitrification rate in the A/O or A2/O systems were 67.5% and 2.08 mg N h^-1 gMLVSS^-1, respectively. However, cyclic activated sludge systems (CASSs) showed more efficient nitrogen removal with an average NRR and denitrification rate of 79.6% and 9.89 mg N h^-1 gMLVSS^-1, respectively. The microbial communities in WWTPs with similar influent compositions were similar and mainly shaped by BOD₅. Candidatus Competibacter, Caldilineaceae and Anaerolineaceae were the functional genera closely associated with nitrogen removal based on high-throughput sequencing and correlation analysis. This study provides new insights into the regulation and amelioration of full-scale WWTPs to meet the increasingly stringent nitrogen discharge standard.

Characterizing community dynamics and exploring bacterial assemblages in two activated sludge systems

Bacterial communities in the activated sludge (AS) determine the wastewater treatment performance in the municipal wastewater treatment plants (WWTPs). Aiming at identifying the affecting factors and the variation patterns of the bacterial assemblages in AS, a 2-year time-series AS samples were collected from two separated WWTPs and metagenomic sequencing was conducted. Obvious seasonal shift and succession of the bacterial community were observed in both WWTPs on the genus and species levels, especially for the persistent taxa, implying that temperature was a decisive factor for maintaining bacterial assemblage patterns in long-term period. Taxa abundance distribution (TAD) concerning occurrence frequency and average abundance were found fitting for exponential formulations, and the approximately equal total abundance of persistent taxa suggested that stable and high abundance (~ 90%) of core functional bacterial groups would help to maintain wastewater treatment performance. Drastic changes of environmental factors were found causing temporally significant bacterial structure variation, while the innate correlations between bacterial species could recover the community gradually and maintain relative stability of the AS system. Delayed correlations between environmental factors and abundant (persistent or intermittent) bacterial species were observed widely, while synchronous biotic interactions were identified more frequently. Besides, bacterial species with similar functions were prone to cluster together and shared the same seasonal variation pattern, implicating that the cooperation of functional correlated taxa played the most dominant role in shaping the bacterial assemblages. Furthermore, rare bacterial groups were to be explored for removing emerging pollutants with lower concentrations. The results of this study would assist dealing with operational defect and optimize the treatment system in WWTPs.

Insights into the key components of bacterial assemblages in typical process units of oily wastewater treatment plants

To compare the structure of microbial community in the oily wastewater treatment plants (OWWTPs) located in China, and to discern the impacts of environment variables on the variance of microbial community, activated sludge samples from six typical OWWTPs were taken and the structure of microbial community of these six samples were analyzed via Illumina high-throughput sequencing. 18 core genera including Comamonas, Bacillus, Pseudomonas, Thauera, Paenibacillus, etc. were shared by all OWWTPs. Canonical correspondence analysis (CCA) suggested that temperature, oil concentration, DO and pH exhibited significant impacts in shaping the structure of microbial community. Variance partitioning analyses (VPA) illuminated that the most variation in microbial community was contributed to geographic location, explaining 36.4% of the total variations obtained, followed by wastewater characteristics (18.7%) and operational parameters (8.6%). This work offered insights into the structure of microbial community in OWWTPs at different geographic locations and illustrated the correlations between environment variables and microbial community in OWWTPs.

Rapid BOD assessment with a microbial array coupled to a neural machine learning system

The domestic usage of water generates approximately 310 km³ of wastewater worldwide (2015, AQUASTAT, Food and Agriculture Organization of United Nations). This sewage contains an important organic load due to the use of this water; this organic load is characterized using a standard method, namely, the biological oxygen demand measurement (BOD₅). The BOD₅ provides information about the biodegradable organic load (standard ISO 5815). However, this measurement protocol is very time-consuming (5 days) and may produce variability in approximately 20% of results mainly due to variation in the environmental inocula. To remedy these limitations, this work proposes an innovative concept relying on the implementation of a set of rigorously selected bacterial strains. This publication depicts the different steps used in this study, from bio-indicator selection to validation with real wastewater samples. The results obtained in the final step show a strong correlation between the developed approach and the reference method (ISO 5815) with a correlation rate of approximately 0.9. In addition, the optimization of the experimental conditions and the use of controlled strains (8 selected strains) allow significant reduction in the duration of the BOD₅ analysis, with only 3 h required for the proposed method versus 5 days for the reference method. This technological breakthrough should simplify the monitoring of wastewater treatment plants and provide quicker, easier and more coherent control in terms of the treatment time.

Structure and function of microbial community involved in a novel full-scale prefix oxic coking wastewater treatment O/H/O system

A novel full-scale prefix oxic coking wastewater (CWW) biological treatment O/H/O system had been operated steadily six years with the effluent quality meeting national discharge standard. Comparing to the traditional CWW biological treatment process, which usually have an anaerobic unit at the start of the process, here the O/H/O system has obvious advantages in COD removal, total nitrogen removal and reduced energy consumption. It is very necessary to illustrate the structure and function of the microbial community involved in different bioreactors of the O/H/O system. High-throughput MiSeq sequencing was used to examine the 16S rRNA genes in this system. Results revealed a contrasting microbial composition among the activated sludge samples of three sequential bioreactors: the β-Proteobacteria related sequences dominated in the O₁ activated sludge with the relative abundance of 56.44% while 7.53% of the sequences were assigned to Thiobacillus; Rhodoplanes related sequences dominated in the bioreactor H and O₂ activated sludge with relative abundance of 8.86% and 8.92%, respectively. The physico-chemical characteristics of CWW were analyzed by standard methods and the operational parameters were routinely monitored to examine their effects on the microbial communities. The bioinformatics software package of phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) was used to predict the microbial community functional profiling and found three dominant genera of Rhodoplanes, Lysobacter and Leucobacter enriched the xenobiotics biodegradation and metabolism pathway. The diverse and distinct microbial community involved in biological treatment processes of CWW treatment indicating that water characteristics and operational parameters determined the microbial community composition. These results significantly expanded our knowledge of the biodiversity and population dynamics of microorganisms and discerned the relationships between bacterial communities and environmental variables in the biological treatment processes. Moreover, in this study, we proposed a comprehensive biodegradation model of CWW treatment and defined as O/H/O system.

The capacity of wastewater treatment plants drives bacterial community structure and its assembly

Bacterial communities in wastewater treatment plants (WWTPs) affect plant functionality through their role in the removal of pollutants from wastewater. Bacterial communities vary extensively based on plant operating conditions and influent characteristics. The capacity of WWTPs can also affect the bacterial community via variations in the organic or nutrient composition of the influent. Despite the importance considering capacity, the characteristics that control bacterial community assembly are largely unknown. In this study, we discovered that bacterial communities in WWTPs in Korea and Vietnam, which differ remarkably in capacity, exhibit unique structures and interactions that are governed mainly by the capacity of WWTPs. Bacterial communities were analysed using 16S rRNA gene sequencing and exhibited clear differences between the two regions, with these differences being most pronounced in activated sludge. We found that capacity contributed the most to bacterial interactions and community structure, whereas other factors had less impact. Co-occurrence network analysis showed that microorganisms from high-capacity WWTPs are more interrelated than those from low-capacity WWTPs, which corresponds to the tighter clustering of bacterial communities in Korea. These results will contribute to the understanding of bacterial community assembly in activated sludge processing.

A full-scale survey of sludge landfill: sludge properties, leachate characteristics and microbial community structure

In this study, a full-scale survey was conducted of a sludge landfill that had been sealed for 10 years to investigate sludge properties, leachate characteristics and microbial community structure. Vertical distribution of sludge and leachate pollutants in the landfill site showed that the sludge and soluble pollutants in the leachate were both distributed almost evenly even after long-term anaerobic digestion, and higher concentrations of soluble pollutants and richness of microbial community were observed at the middle layer. Compared to dewatered excess sludge generated from the activated sludge process before landfill, landfill sludge had a much lower organic content (28.1%), smaller particle size and worse dewaterability. Compared to municipal waste landfill, sludge landfill generated leachate with a lower concentration of organic substances, and comparable concentrations of nitrogenous and phosphorus pollutants. Bacterial community analysis by Illumina MiSeq sequencing showed that Proteobacteria, Firmicutes, Chloroflexi, Actinobacteria and Bacteroidetes were the major phyla, and some new genera (Methylocystaceae, Mariniphaga and Aminicenantes) were enriched in the sludge landfill. Archaeal community analysis showed that aceticlastic methanogenesis by Methanosaeta and Methanosarcina was the main pathway for methane production in the sludge landfill, in contrast to waste landfill with hydrogenotrophic methanogenesis as the main pathway.

Abundance of antibiotic resistance genes and their association with bacterial communities in activated sludge of wastewater treatment plants: Geographical distribution and network analysis

Wastewater treatment plants (WWTPs) are deemed reservoirs of antibiotic resistance genes (ARGs). Bacterial phylogeny can shape the resistome in activated sludge. However, the co-occurrence and interaction of ARGs abundance and bacterial communities in different WWTPs located at continental scales are still not comprehensively understood. Here, we applied quantitative PCR and Miseq sequence approaches to unveil the changing profiles of ARGs (sul1, sul2, tetW, tetQ, tetX), intI1 gene, and bacterial communities in 18 geographically distributed WWTPs. The results showed that the average relative abundance of sul1and sul2 genes were 2.08 × 10^-1 and 1.32 × 10^-1 copies/16S rRNA copies, respectively. The abundance of tetW gene was positively correlated with the Shannon diversity index (H'), while both studied sul genes had significant positive relationship with the intI1gene. The highest average relative abundances of sul1, sul2, tetX, and intI1 genes were found in south region and oxidation ditch system. Network analysis found that 16 bacterial genera co-occurred with tetW gene. Co-occurrence patterns were revealed distinct community interactions between aerobic/anoxic/aerobic and oxidation ditch systems. The redundancy analysis model plot of the bacterial community composition clearly demonstrated that the sludge samples were significant differences among those from the different geographical areas, and the shifts in bacterial community composition were correlated with ARGs. Together, these findings from the present study will highlight the potential risks of ARGs and bacterial populations carrying these ARGs, and enable the development of suitable technique to control the dissemination of ARGs from WWTPs into aquatic environments.

Bacterial community structure in rotating biological contactor treating coke wastewater in relation to medium composition

Biological wastewater treatment using biofilm systems is an effective way to treat difficult wastewater, such as coke wastewater. The information about the structure and the dynamics of this microbial community in biofilm, which are responsible for wastewater treatment, is relevant in the context of treatment efficacy and the biochemical potential to remove various pollutants. However, physico-chemical factors can influence the biofilm community significantly, causing performance disturbances. Therefore, we decided to examine the structure of microbial community in rotating biological contactor (RBC) biofilm during coke wastewater treatment and to investigate the possible shift in the community structure caused by the feeding medium change from synthetic to real coke wastewater. The experiment performed with high-throughput next-generation sequencing (NGS) revealed that bacteria commonly present in wastewater treatment plant (WWTP) systems, responsible for nitrite oxidizing, such as Nitrospira or Nitrobacter, were absent or below detection threshold, while Nitrosomonas, responsible for ammonia oxidizing, was detected in a relatively small number especially after shift to real coke wastewater. This research indicates that medium change could cause the change from autotrophic into heterotrophic nitrification led by Acinetobacter. Moreover, biofilm systems can be also a potential source of bacteria possessing high biochemical potential for pollutants removal but less known in WWTP systems, as well as potentially pathogenic microorganisms.

Global diversity and biogeography of bacterial communities in wastewater treatment plants

Microorganisms in wastewater treatment plants (WWTPs) are essential for water purification to protect public and environmental health. However, the diversity of microorganisms and the factors that control it are poorly understood. Using a systematic global-sampling effort, we analysed the 16S ribosomal RNA gene sequences from ~1,200 activated sludge samples taken from 269 WWTPs in 23 countries on 6 continents. Our analyses revealed that the global activated sludge bacterial communities contain ~1 billion bacterial phylotypes with a Poisson lognormal diversity distribution. Despite this high diversity, activated sludge has a small, global core bacterial community (n = 28 operational taxonomic units) that is strongly linked to activated sludge performance. Meta-analyses with global datasets associate the activated sludge microbiomes most closely to freshwater populations. In contrast to macroorganism diversity, activated sludge bacterial communities show no latitudinal gradient. Furthermore, their spatial turnover is scale-dependent and appears to be largely driven by stochastic processes (dispersal and drift), although deterministic factors (temperature and organic input) are also important. Our findings enhance our mechanistic understanding of the global diversity and biogeography of activated sludge bacterial communities within a theoretical ecology framework and have important implications for microbial ecology and wastewater treatment processes.

Deciphering the Assembly Processes of the Key Ecological Assemblages of Microbial Communities in Thirteen Full-Scale Wastewater Treatment Plants

Limited information is currently available on the assembly processes (deterministic vs. stochastic) shaping the compositions of key microbial communities in activated sludge (AS). The relative importance of deterministic and stochastic processes for key bacterial and archaeal assemblages (i.e., core-satellite and habitat generalist-specialist) in AS from 13 wastewater treatment plants in China was investigated using 16S rDNA amplicon sequencing. The results obtained indicated 1,388 and 369 core operational taxonomic units (OTUs), 1,038 and 1,683 satellite OTUs, 255 and 48 habitat generalist OTUs, and 192 and 111 habitat specialist OTUs for Bacteria and Archaea, respectively. The proportions of shared OTUs between core and habitat specialist communities were similar to or higher than those between core and habitat generalist communities, suggesting a stronger inter-linkage between the former two groups. Deterministic processes, indicated by abundance-based β-null models, were responsible for shaping core communities, in which NH₄-N, OrgC/OrgN, Cr, and Ni were the main controlling factors. In contrast, satellite communities were predominantly influenced by stochastic processes. Moreover, we found that deterministic and stochastic processes were mainly responsible for shaping the assembly of habitat specialists and generalists, respectively. However, the influence of deterministic factors on habitat specialists remains unclear. The present study provides novel insights into the assembly mechanisms of AS microbial communities.

Shifts in the Microbial Community of Activated Sludge with Different COD/N Ratios or Dissolved Oxygen Levels in Tibet, China

In this study, we examined the influence of the organic carbon-to-nitrogen ratio (chemical oxygen demand (COD/N)) and dissolved oxygen (DO) levels on the removal efficiency of pollutants and on the change in total microflora in the cyclic activated sludge system (CASS) in the Nyingchi prefecture in Tibet. The results demonstrated that the treatment performance was the best when the COD/N ratio was 7:1 or the DO levels were 2–2.5 mg/L in comparison with four different tested COD/N ratios (4:1, 5:1, 7:1, and 10:1) and DO concentrations (0.5–1, 1–2, 2–2.5, and 2.5–3.5 mg/L). The treatment performance can be explained by the relative operational taxonomic unit richness and evenness of the microbial communities in activated sludge. Evident microbial variance was observed, especially different COD/N ratios and DO concentrations, which were conducive to the disposal of urban sewage in plateaus. The results help to understand sewage treatment under different COD/N ratios or DO concentrations on plateaus. This work provides practical guidance for the operation of any wastewater treatment plant on a plateau.

Long-term dynamics of the bacterial community in a Swedish full-scale wastewater treatment plant

The operational efficiency of activated sludge wastewater treatment plants depends to a large extent on the microbial community structure of the activated sludge. The aims of this paper are to describe the composition of the bacterial community in a Swedish full-scale activated sludge wastewater treatment plant, to describe the dynamics of the community and to elucidate possible causes for bacterial community composition changes. The bacterial community composition in the activated sludge was described using 16S rRNA gene libraries and monitored for 15 months by a terminal restriction fragment (T-RF) length polymorphism (T-RFLP) analysis of the 16S rRNA gene. Despite variable environmental conditions, a large fraction of the observed T-RFs were present at all times, making up at least 50% in all samples, possibly representing a relatively stable core fraction of the bacterial community. However, the proportions of the different T-RFs in this fraction as well as the T-RFs in the more variable fraction showed a significant variation over time and temperature. The difference in community composition between summer and winter coincided with observed differences in floc structure. These observations suggest a relationship between floc properties and bacterial community composition, although additional experiments are required to determine causality.

Nitrogen removal and responses of bacterial communities in activated sludge under different operational manipulations

Operational conditions are often manipulated to improve the nitrogen removal performance of wastewater treatment, yet the impacts of operational conditions on microbial communities were still not well understood. There is a pressing need to understand the microbial mechanisms that link operation manipulation and nitrogen removal performance. In this study, high-throughput analysis of 16S rDNA and quantitative polymerase chain reaction of functional genes were used to identify the microbial response to operational manipulations. The results showed that alteration of operational parameters could change the bacterial communities at the genera level and denitrification guild gradually dominated in the activated sludge bacterial communities. Heterotrophic Hyphomicrobium and Chromatiaceae drove the kinetic of dominant genera and denitrification guild. Carbon source supplement was the most efficient strategy for improving nitrogen removal, and greatly increased the abundance of denitrifiers and denitrification genes. However, carbon source supplement inhibited expression activities of denitrification genes, as well as the proliferation of autotrophic denitrifiers, and it was supposed to be unfavorable in terms of cost over the long term. The result should bring new inspiration for improving the effect of WWTP performance through the manipulation of operational parameters.

Effect of temperature on nitrogen removal and biological mechanism in an up-flow microaerobic sludge reactor treating wastewater rich in ammonium and lack in carbon source

Previous study has demonstrated that microaerobic process is effective in nitrogen removal from the wastewater with high ammonium and low carbon to nitrogen ratio. In the microaerobic system, synergistic action of anammox, ammonia oxidizing bacteria (AOB), nitrite oxidizing bacteria (NOB) and denitrifiers was the key issues to remove nitrogen from the wastewater rich in ammonium. Temperature has a significant effect on specific growth rate and activity of various nitrogen removal functional bacteria. In this study, the effect of temperature (35 °C-15 °C) on nitrogen removal were investigated in an up-flow microaerobic sludge reactor (UMSR) at the HRT of 8 h and reflux ratio of 45. Above 71.2% of total nitrogen (TN) and 80.7% of NH₄⁺ removal efficiencies were observed at the temperature no less than 17 °C. With the temperature further decreasing to 15 °C, denitrifiers still dominant the UMSR, but AOB, NOB and Candidatus Brocadia as the predominant anammox bacteria were inhibited revealed by high throughput sequencing, resulting in the decrease of TN and NH₄⁺ removal to 39.7% and 61.8%, respectively. Fortunately, when the temperature rebounded to 20 °C, a higher TN and NH₄⁺ removal of 81.2% and 97.3% were obtained again in the UMSR.

Effects of different wastewater characteristics and treatment techniques on the bacterial community structure in three pharmaceutical wastewater treatment systems

Pharmaceutical wastewater is a typical type of wastewater with high concentrations of organic pollutants, but research on this subject is limited. The aeration tanks of three different pharmaceutical wastewater treatment systems were seeded with the same inocula and stably operated for 40 days. Then, aerobic sludge samples from the three aeration tanks were collected to provide insight into the bacterial community composition of the activated sludges. Additionally, we investigated the effects of wastewater characteristics and the type and operation of the technological system on the microbial communities. High-throughput sequencing analysis demonstrated that the communities enriched in the three reactors had differing. The dominant phyla detected were Proteobacteria, Chloroflexi, Bacteroidetes and candidate division TM7, while the dominant clones were uncultured Candidatus Saccharibacteria bacterium, uncultured Saprospiraceae bacterium, PHOS-HE51(AF314433.1), uncultured Anaerolineaceae bacterium and Blastocatella, suggesting their importance in pharmaceutical wastewater treatment plants. According to the wastewater parameters and canonical correspondence analyses, we can conclude that uncultured Candidatus Saccharibacteria bacterium, uncultured Anaerolineaceae bacterium and Blastocatella contribute to ammonium nitrogen ( ) removal; uncultured Saprospiraceae bacterium plays an important role in treating nitrogen; and chemical oxygen demand and PHOS-HE51 contribute to total phosphorus removal.

Day/night temperature differences (DNTD) trigger changes in nutrient removal and functional bacteria in membrane bioreactors

Temperature is a well-known environmental stress that influences both microbial metabolism and community structure in the biological wastewater treatment systems. In this study, responses of biological performance and sludge microbiota to the long-term day/night temperature differences (DNTD) were investigated in membrane bioreactors (MBRs). The results showed that the functional bacteria could sustained their ecological functions at low DNTD (20/30 °C), resulting in relatively stable performance with respect to nutrient removal. However, when the activated sludge was subjected to a high DNTD (17/33 °C), the effluent concentrations of COD, TN and TP were significantly higher in MBR-B than that in MBR-A. In addition, more severe membrane fouling occurred under the perturbation of high DNTD as revealed by the transmembrane pressure (TMP) profile, which was mainly attributed to the accumulation of extracellular polymeric substances (EPS). The results of 16S rRNA gene sequencing showed that DNTD showed negligible effect on the bacterial community structures. Nonetheless, the functional bacteria responded differently to DNTD, which were in accordance with the bioreactor performances. Specifically, Nitrospina (NOB) and Tetrasphaera (PAOs) appeared to be sensitive to both low and high DNTD. In contrast, a low DNTD showed marginal effects on the denitrifiers, while a high DNTD significantly decreased their abundances. More strikingly, filamentous bulking bacteria were found to be well-adapted to DNTD, indicating their tolerance to the daily temperature fluctuation. This study will advance our knowledge regarding the response of microbial ecology of activated sludge to daily temperature variations in full-scale MBRs.

Nitrifying and Denitrifying Bacterial Communities in Advanced Nitrogen-Removal Onsite Wastewater Treatment Systems

Advanced N-removal onsite wastewater treatment systems (OWTS) rely on nitrification and denitrification to remove N from wastewater. Despite their use to reduce N contamination, we know little about microbial communities controlling N removal in these systems. We used quantitative polymerase chain reaction and high-throughput sequencing targeting nitrous oxide reductase () and bacterial ammonia monooxygenase () to determine the size, structure, and composition of communities containing these genes. We analyzed water samples from three advanced N-removal technologies in 38 systems in five towns in Rhode Island in August 2016, and in nine systems from one town in June, August, and October 2016. Abundance of ranged from 9.1 × 10 to 9 × 10 copies L and differed among technologies and over time, whereas bacterial abundance ranged from 0 to 1.9 × 10 copies L and was not different among technologies or over time. Richness and diversity of -but not -differed over time, with median Shannon diversity indices ranging from 2.61 in October to 4.53 in August. We observed weak community similarity patterns driven by geography and technology in The most abundant and containing bacteria were associated with water distribution and municipal wastewater treatment plants, such as and species. Our results show that communities in N-removal OWTS technologies differ slightly in terms of size and diversity as a function of time, but not geography, whereas communities are similar across time, technology, and geography. Furthermore, community composition appears to be stable across technologies, geography, and time for .

Gas chromatography coupled with mass spectrometry-based metabolomics for the classification of tempe from different regions and production processes in Indonesia

Tempe, a fermented soybean originally from Indonesia, is an excellent protein source with high nutritional quality. Differences in the production process and unique fermentation condition in different regions result in varieties of tempe. Despite its high cultural and economic values, there are very few studies on the characterization of tempe based on the differences of production process and geographical origin. Metabolomics is a powerful tool assessing food quality, food safety, and determination of origin and varietal differences. In this study, metabolomics is applied for the study of Indonesian tempe obtained from various regions and different production processes. Seventeen samples were collected from 6 different cities in Java Island, which were produced by local tempe crafters (traditional), semi-modern industry and modern industry. Untargeted metabolomics by gas chromatography coupled with mass spectrometry (GC/MS) was implemented to discriminate various kinds of tempe and identify metabolites that are associated with these differences. Results showed that tempe produced in different places clustered together according to the cities and their production category. Sugars and amino acids groups were found to be primary compounds that contributed to this result. This is the first report that address the metabolic differences between different varieties of tempe from different regions and production processes. The knowledge from this study is important for future development of tempe production.

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

The microbial community structures of drinking water treatment sludge (DWTS) generated for raw water (RW) from different locations and with different source types - including river water, lake water and reservoir water -were investigated using high-throughput sequencing. Because the unit operations in the six DWTPs were similar, community composition in fresh sludge may be determined by microbial community in the corresponding RW. Although Proteobacteria, Cyanobacteria, Bacteroidetes, Firmicutes, Verrucomicrobia, and Planctomycetes were the dominant phyla among the six DWTS samples, no single phylum exhibited similar abundance across all the samples, owing to differences in total phosphorus, chemical oxygen demand, Al, Fe, and chloride in RW. Three genera of potentially toxic cyanobacteria (Planktothrix, Microcystis and Cylindrospermopsis), and four potential pathogens (Escherichia coli, Bacteroides ovatus, Prevotella copri and Rickettsia) were found in sludge samples. Because proliferation of potentially toxic cyanobacteria and Rickettsia in RW was mainly affected by nutrients, while growth of Escherichia coli, Bacteroides ovatus and Prevotella copri in RW may be influenced by Fe, control of nutrients and Fe in RW is essential to decrease toxic cyanobacteria and pathogens in DWTS.

Exploring abundance, diversity and variation of a widespread antibiotic resistance gene in wastewater treatment plants

An updated sul1 gene sequence database was constructed and new degenerate primers were designed to better investigate the abundance, diversity, and variation of a ubiquitous antibiotic resistance gene, sul1, with PCR-based methods in activated sludge from wastewater treatment plants (WWTPs). The newly designed degenerate primers showed high specificity and higher coverage in both in-silico evaluations and activated sludge samples compared to previous sul1 primers. Using the new primers, the abundance and diversity of sul1 gene, together with 16S rRNA gene, in activated sludge from five WWTPs in summer and winter were determined by quantitative PCR and MiSeq sequencing. The sul1 gene was found to be prevalent and displayed a comparable abundance (0.081 copies per bacterial cell in average) to the total bacteria across all samples. However, compared to the significant seasonal and geographical divergences in the quantity and diversity of bacterial communities in WWTPs, there were no significant seasonal or geographical variations of representative clusters of sul1 gene in most cases. Additionally, the representative sul1 clusters showed fairly close phylogeny and there was no obvious correlation between sul1 gene and the dominant bacterial genera, as well as the int1 gene, suggesting that bacterial hosts of sul1 gene is not stable, the sul1 gene may be carried by mobile genetic elements, sometimes integrated with class 1 integrons and sometimes not. Thus mobile genetic elements likely play a greater role than specific microbial taxa in determining the composition of sul1 gene in WWTPs.

The divergence between fungal and bacterial communities in seasonal and spatial variations of wastewater treatment plants

In this study, quantitative PCR (qPCR) and high-throughput sequencing were used to simultaneously examine both bacteria and fungi across temporal and spatial scales in activated sludge from wastewater treatment plants (WWTPs). The ratio of fungi to bacteria was 0.43% on average after accounting for the multicopies in 16S rRNA gene (54.63%), indicating the number of fungi was far lower than bacteria in active sludge. The Miseq sequencing results revealed obvious seasonal and spatial variations in bacterial and fungal distribution patterns in WWTPs. Compared to bacteria, fungi showed a lower divergence in alpha and beta diversity, and exhibited less taxonomic diversity in both abundant and rare subcommunities at the class level, suggesting that the fungal community was less variable in this artificial ecosystem. Such variation of microbial communities was significantly correlated with geographical distance, DO, temperature, HRT, SRT, COD, TN and TP. In activated sludge, the main function of bacteria was chemoheterotrophy, fermentation, and nitrogen cycling processes, while the dominant functional guilds of fungi were saprotroph, animal pathogen, and animal endosymbiont. Moreover, both bacteria and fungi could play important roles in the degradation of toxicants, like hydrocarbon and aromatic compounds.