Functional stability correlates with dynamic microbial networks in anammox process.

Understanding the relationship between dynamic microbial networks and functional stability is critical for the stable operation of anammox systems. Here, by operating an anammox reactor under constant condition over 250 days, it was found that the relative abundance of Planctomycetota gradually decreased while Chloroflexi and Proteobacteria increased, with stochasticity predominating the bacterial assembly as the reactor operation. Network analysis revealed a successional dynamic pattern of microbial interaction despite stable performance. The variation of subnetworks indicated Chloroflexi and Proteobacteria alternately played important role in anammox microbial network, and the negative relationship between anammox bacteria and heterotrophs could achieve a balance to keep functional stability under long-term operation. Furthermore, the identified keystone species mainly belonged to heterotrophs that were critical in maintaining network structure and system function. The results of this study revealed clear changing patterns of microbial community and network succession, which could provide valuable reference for other stably operated bioreactors.

Metagenomic insights into the symbiotic relationship in anammox consortia at reduced temperature.

Anammox as a promising biological nitrogen removal technology has attracted much attention. However, cold temperature would limit its wide application and little is known about the microbial interactions between anammox bacteria (AnAOB) and heterotrophic bacteria at cold temperature. Here, we observed reduced temperature (25-15 °C) promoted the secretion of EPS and thus stimulated bigger size of granular sludge in a laboratory-scale anammox reactor. We further combined co-occurrence network analysis and genome-centered metagenomics to explore the potential interactions between AnAOB and heterotrophic bacteria. Network analysis suggested 22 out of 25 positively related species were reported as definite heterotrophic bacteria in subnetwork of AnAOB. Genome-centered metagenomics analysis yielded 23 metagenomic assembly genomes (MAGs), and we found that Acidobacteriota-affiliated bacteria could biosynthesize most polysaccharides (PS) precursors and contain the most glycosyltransferases and transporters to facilitate exopolysaccharides biosynthesis, together with partial PS precursors produced by AnAOB. AMX1 as the only anammox genome could synthesize most amino acids and cross feed with some heterotrophs to affect the extracellular protein function. Additionally, Bacteroidota, Planctomycetota, Chloroflexota, and Proteobacteria could contribute folate and molybdopterin cofactor for AMX1 to benefit their activity and growth. Superphylum Patescibacteria could survive by cross-feeding with AnAOB and heterotrophic organisms about organic compounds (Glyceraldehyde-3P and lactate). These cross-feedings maintained the stability of anammox reactor performance and emphasize the importance of heterotrophs in anammox system at reduced temperature.

Successional Dynamics of Molecular Ecological Network of Anammox Microbial Communities under Elevated Salinity.

Response of microbial interactions to environmental perturbations has been a central issue in wastewater treatment system. However, the interactions among anammox microbial community under salt perturbation is still unclear. Here, we used random matrix theory (RMT)-based network analysis to investigate the dynamics of networks under elevated salinity in an anammox system. Results showed that high salinity (20 and 30 g/L NaCl) inhibited anammox performance. Salinity led to closer and more complex networks for the overall network and subnetwork of Planctomycetes and Proteobacteria, especially under low salinity (5 g/L NaCl), which could serve as a strategy to survive under salt perturbation. Planctomycetes, most dominant phylum and playing crucial roles in anammox, possessed higher proportion of competitive relationships (64.3%) under 30 g/L NaCl. OTU 109 (closely related to Ignavibacterium), the only network hub detected in the anammox system, also had larger amount of competitive relationships (27.3%) than the control (0%) under 30 g/L NaCl. Similar result was found for the most abundant keystone bacteria Candidatus Kuenenia. These increasing competitions at different taxa level could be responsible for the deterioration of nitrogen removal. Besides, all the network topological features tended to reach the values of the original network, which showed the network of microbial community could gradually adapt to the elevated salinity. Microbial network analysis adds a different dimension for our understanding of the response in microbial community to elevated salinity.

Disentangling the contributions of urban and production sources in short- and medium-chain chlorinated paraffin concentrations in a complex source region.

Short-chain chlorinated paraffins (SCCPs) and medium-chain chlorinated paraffins (MCCPs) were measured in tree bark samples. These samples were collected around a chemical industrial park containing several chlorinated paraffin (CP) production plants, in a nearby city (Zhengzhou), and along a transect between the industrial park and city. Theoretical air concentrations were back-calculated from concentrations in bark using a predictive equation for estimating equilibrium bark-air partition coefficients. We developed this equation from a series of previously published Kbark-air measurements. Comparison of the normalized concentration profiles along south to north transects showed that wind played only a minor role in CP concentrations and profiles in the region. Three distinct source profiles were found in the complex source region. A fingerprint analysis technique was used to quantify the contribution of each source to the CP burden at various locations along the transect. We found that CP profiles at sites up to 6 km from the industrial park were strongly influenced by CP plant emissions, whereas the sites located in the rural zone and rural-urban interface were influenced by a mixture of CP plant emissions and the neighboring city.

All-MXene-Based Integrated Membrane Electrode Constructed using Ti3C2Tx as an Intercalating Agent for High-Performance Desalination.

2D-Ti3C2Tx MXene flake restacking and the small interlayer spacing of these MXenes limit their application in capacitive deionization. Here, we designed an all-MXene-based (L-S-Ti3C2Tx) flexible film electrode, enabled by large-size Ti3C2Tx (lateral dimensions of ⩾1 µm) MXene (L-Ti3C2Tx) nanosheets, which provided conductive pathways and were active substances, and by small-size Ti3C2Tx (500 nm) MXene (S-Ti3C2Tx) nanosheets, which were used as intercalation materials and active substances, for high-performance desalination in capacitive deionization applications. The as-synthesized L-S-Ti3C2Tx electrode achieved an excellent capacitance (169 F/g at 5 mV/s) and long-term cycling stability (maintained 91.7% of the initial capacitance after 5000 cycles). Additionally, these electrodes exhibited a high electroadsorption capacity (72 mg NaCl/g L-S-Ti3C2Tx, 10 mM NaCl solution). The improved electrochemical and desalination performance and outstanding long-term cycling stability can be attributed to the small Ti3C2Tx sheets that were introduced, which could be beneficial in exposing more active sites, facilitating electron transport, and shortening the diffusion path of Na ions. Our work opens up a new design space for the development of high-performance anode materials.

Spatial distribution and profile of atmospheric short-chain chlorinated paraffins in the Yangtze River Delta.

Research on the atmospheric occurrence of short chain chlorinated paraffins (SCCPs) in industrialized areas is scarce. In this study, we investigated the concentrations, profile, and spatial distribution of SCCPs in the highly industrialized and developed areas of the Yangtze River Delta (YRD) in China using polyurethane foam passive air samplers. Sampling was performed during two separate periods in 2011. The concentrations of atmospheric SCCPs ranged from 6.1 to 63 ng m-3 in summer and 6.2-42 ng m-3 in winter. The C10 and C11 groups were the predominant carbon groups in all the samples. Different congener patterns between summer and winter were found, indicating that congeners in the air in winter may be influenced by local and external sources. The highest level of SCCPs was found in Suzhou, which is a highly industrialized area with many manufactories including electronic industries and plastic factories. Higher levels of SCCPs were found in the air than polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and polybrominated diphenyl ether (PBDEs), suggesting that the production and use of SCCPs were much higher than prohibited or restricted persistent organic pollutants (e.g., PCBs, OCPs, and PBDEs). Future studies should investigate the different sources of atmospheric SCCPs by conducting a comprehensive assessment of SCCP exposure.

Acute effects of hexavalent chromium on the performance and microbial community of activated sludge in aerobiotic reactors.

This study investigated the acute effects of hexavalent chromium (Cr(VI)) shock load at 2.5, 6 and 25 mg/L on the performance and bacterial community structures in aerobiotic activated sludge reactors. The results showed that eight-day Cr(VI) toxicity made the removal rates of COD and NH3-N to obviously decrease in all reactors. Furthermore, the higher the Cr(VI) concentration was, the more severe the influence on the whole system would be. The effect of Cr(VI) on NH3-N removal was more serious than that on COD and the function of nitrification was harder to recover. The specific oxygen uptake rate (SOUR) values dropped by 73%, 68% and 31% at 2.5, 6 and 25 mg Cr(VI)/L, respectively. The data of SOUR showed that though the concentration of Cr(VI) was low, the whole respiratory activity of bacteria was much affected. The relative abundance change of genus between the initial stage and the last showed that the bacterial community structure changed significantly. Comparing with the initial stage, the phyla of Proteobacteria, Acidobacteria and Planctomycetes were markedly reduced at the end stage. The genera of Ferruginibacter, Coxiella and Rhodanobacter were also markedly reduced. Although the performance of activated sludge can be restored at the end, the whole respiratory activity of bacteria was still at a low level according to the data of SOUR.

[Effect of Fluoroquinolones on Performance and Microbial Community of a Vertical Flow Constructed Wetland].

In order to investigate the effect of multiple fluoroquinolones on the performance and microbial community of a constructed wetland, ofloxacin, norfloxacin, and ciprofloxacin were added to the influent of the vertical flow constructed wetland for two months. Results indicated that COD removal rate gradually decreased after adding antibiotics, with the minimum removal rate of 70.94%, followed by gradual recovery. TP removal rate also decreased, with some fluctuations, while ammonia removal remained stable. Fluoroquinolones thus have an important effect on COD and TP removal from the constructed wetland, but there is no evident effect on ammonia removal. Based on results of the Shannon index and Shannoneven index, there were no significant changes in the microbial community, while the Chao1 index increasing significantly. Comparing community composition before and after antibiotic addition, the relative abundance of Proteobacteria decreased from 44.90% to 34.12%, still maintaining its predominance, while Firmicutes increased from 2.55% to 10.55%. At the class level, ß-Proteobacteria declined from 17.03% to 8.36%, while the relative abundance of Clostridia, Bacilli, and Bacteroidia increased from 0.50%, 1.85%, and 0.10% to 4.21%, 4.64%, and 2.56%, respectively. The genera Dechloromonas and Pseudarthrobacter decreased from 8.56% and 5.10% to 3.16% and 1.53%, respectively, while Trichococcus, Tessaracoccus, and Desulfovibrio increased from 0.66%, 0.03%, and 0.02% to 3.84%, 3.83%, and 2.06%, respectively. The microbial community of the constructed wetland thus changed under the pressure of multiple fluoroquinolones.

Bacterial community and molecular ecological network in response to Cr2O3 nanoparticles in activated sludge system.

The potential environmental risks of chromium oxide nanoparticles (Cr2O3 NPs) have caused great concerns. However, their possible impacts on activated sludge process are very limited. In this study, we carried out long-term exposure experiments to evaluate the influence of Cr2O3 NPs on wastewater nutrient removal, bacterial community and molecular ecological network (MEN) in the sequencing batch reactor (SBR). It was found that 1 mg/L Cr2O3 NPs increased the effluent concentrations of NO3--N and TP from 6.5 to 15.4 mg/L, and 0.6-2.7 mg/L, indicating the serious deterioration of denitrification and phosphorus removal. Cr2O3 NPs significantly decreased the bacterial richness in terms of the number of different OTUs (626 OTUs in Cr2O3 samples and 728 OTUs in controls). Detrended correspondence analysis (DCA) showed that the overall taxonomic structure of bacterial community was altered at Cr2O3 NPs in activated sludge systems. Further analysis revealed that three genera related to denitrification (Desulfovibrio, Pseudomonas and Hyphomicrobium) and two genera related to phosphorus removal (Accumulibacter and Rhodobacter) decreased significantly, which was consistent with the observed influences of Cr2O3 NPs on denitrification and phosphorus removal. MEN analysis showed that the overall architecture of the network under Cr2O3 NPs was substantially alerted. ß-Proteobacteria, playing an important role in nutrients removal, had less complex interactions in the presence of Cr2O3 NPs, which may be associated with the deterioration of denitrification and phosphorus removal. This study provides insights into our understanding of shifts in the bacteria community and their MEN under Cr2O3 NPs in activated sludge systems.

Responses of Bacterial Communities to CuO Nanoparticles in Activated Sludge System.

The main objectives of this study were to investigate the influence of copper oxide nanoparticles (CuO NPs) on wastewater nutrient removal, bacterial community and molecular ecological network in activated sludge. The results showed that long-term exposure to 1 mg/L CuO NPs induced an increase of effluent concentrations of ammonia and total phosphorus, which was consistent with the inhibition of enzyme activities of ammonia monooxygenase, nitrite oxidoreductase, exopolyphosphatase, and polyphosphate in the presence of CuO NPs. MiSeq sequencing data indicated that CuO NPs significantly decreased the bacterial diversity and altered the overall bacterial community structure in activated sludge. Some genera involved in nitrogen and phosphorus removal, such as Nitrosomonas, Acinetobacter, and Pseudomonas decreased significantly. Molecular ecological network analysis showed that network interactions among different phylogenetic populations were markedly changed by CuO NPs. For example, ß-Proteobacteria, playing an important role in nutrients removal, had less complex interactions in the presence of CuO NPs. These shifts of the abundance of related genera, together with the network interactions may be associated with the deterioration of ammonia and phosphorus removal. This study provides insights into our understanding of shifts in the bacteria community and their molecular ecological network under CuO NPs in activated sludge systems.

Temporal and spatial distribution, sources, and potential health risks of ambient polycyclic aromatic hydrocarbons in the Yangtze River Delta (YRD) of eastern China.

In this study, from July 2011 to June 2012, 31 sampling sites were identified in order to investigate the concentrations and sources of polycyclic aromatic hydrocarbons (PAHs), as well as to evaluate their potential health risks in the cities of Suzhou, Wuxi, and Nantong, which are located in the Yangtze River Delta (YRD). The samples were collected by means of passive air sampling (PAS), and the contents of 15 PAHs were detected by gas chromatography-mass spectrometry. The ∑15PAHs concentrations were found to range from 6.48 to 154 ng m-3, with an average value of 56.8 ± 14.8 ng m-3. The pollution levels in Suzhou and Nantong were higher than those in Wuxi. Furthermore, the concentrations of the PAHs in the urban sites were determined to be higher than those in the suburban sites for ambient air. The seasonal average contents were found to be at a maximum in autumn, with concentrations reaching 74.1 ng m-3. Vehicle emissions and coal/biomass combustion were the dominant sources of the PAHs in the ambient air, with the contributions of 48% and 46%, respectively. The BaP TEQ (0.88 ng m-3) was found to have surpassed the Chinese and Japanese dioxin emission limit, and in doing so, may have caused a certain degree of risk to human health.

Concentrations and distribution of polybrominated diphenyl ethers (PBDEs) in soils and plants from a deca-BDE manufacturing factory in China.

Residues of polybrominated diphenyl ethers (PBDEs), including eight PBDE congeners, were investigated in soils and plants from a deca-BDE manufacturing factory located in the Shandong province of China to evaluate and discuss their pollution level and distribution. Total concentrations in topsoil ranged from 17.0 to 146 µg g(-1) dry weight (dw) with a mean value of 58.7 µg g(-1) dw. BDE-209 was the dominant congener in soils, accounting for 55.63-99.27 % of the total PBDEs. Concentrations and congener patterns in soils varied among different soil depths. Concentration levels in topsoil are high and the heavy accumulation in deep soil also can be observed, even for some sites, the concentrations in 50-100 cm depth are higher than in topsoil. In plant samples, total PBDE concentrations and the proportion of BDE-209 were high (69.92-99.10 %). The extent of pollution by PBDEs in the deca-BDE production factory was higher than in other regions, and the environmental risk caused by the production of deca-BDE is of concern. This is the first study to report pollution of PBDEs in soils and plants from the vicinity of a deca-BDE manufacturing factory.

Impacts of multiwalled carbon nanotubes on nutrient removal from wastewater and bacterial community structure in activated sludge.

BACKGROUND: The increasing use of multiwalled carbon nanotubes (MWCNTs) will inevitably lead to the exposure of wastewater treatment facilities. However, knowledge of the impacts of MWCNTs on wastewater nutrient removal and bacterial community structure in the activated sludge process is sparse. AIMS: To investigate the effects of MWCNTs on wastewater nutrient removal, and bacterial community structure in activated sludge. METHODS: Three triplicate sequencing batch reactors (SBR) were exposed to wastewater which contained 0, 1, and 20 mg/L MWCNTs. MiSeq sequencing was used to investigate the bacterial community structures in activated sludge samples which were exposed to different concentrations of MWCNTs. RESULTS: Exposure to 1 and 20 mg/L MWCNTs had no acute (1 day) impact on nutrient removal from wastewater. After long-term (180 days) exposure to 1 mg/L MWCNTs, the average total nitrogen (TN) removal efficiency was not significantly affected. TN removal efficiency decreased from 84.0% to 71.9% after long-term effects of 20 mg/L MWCNTs. After long-term exposure to 1 and 20 mg/L MWCNTs, the total phosphorus removal efficiencies decreased from 96.8% to 52.3% and from 98.2% to 34.0% respectively. Further study revealed that long-term exposure to 20 mg/L MWCNTs inhibited activities of ammonia monooxygenase and nitrite oxidoreductase. Long-term exposure to 1 and 20 mg/L MWCNTs both inhibited activities of exopolyphosphatase and polyphosphate kinase. MiSeq sequencing data indicated that 20 mg/L MWCNTs significantly decreased the diversity of bacterial community in activated sludge. Long-term exposure to 1 and 20 mg/L MWCNTs differentially decreased the abundance of nitrifying bacteria, especially ammonia-oxidizing bacteria. The abundance of PAOs was decreased after long-term exposure to 20 mg/L MWCNTs. The abundance of glycogen accumulating organisms (GAOs) was increased after long-term exposure to 1 mg/L MWCNTs. CONCLUSION: MWCNTs have adverse effects on biological wastewater nutrient removal, and altered the diversity and structure of bacterial community in activated sludge.

Bacterial community dynamics and taxa-time relationships within two activated sludge bioreactors.

BACKGROUND: Biological activated sludge process must be functionally stable to continuously remove contaminants while relying upon the activity of complex microbial communities. However the dynamics of these communities are as yet poorly understood. A macroecology metric used to quantify community dynamic is the taxa-time relationship (TTR). Although the TTR of animal and plant species has been well documented, knowledge is still lacking in regard to TTR of microbial communities in activated sludge bioreactors. AIMS: 1) To characterize the temporal dynamics of bacterial taxa in activated sludge from two bioreactors of different scale and investigate factors affecting such dynamics; 2) to evaluate the TTRs of activated sludge microbial communities in two bioreactors of different scale. METHODS: Temporal variation of bacterial taxa in activated sludge collected from a full- and lab-scale activated sludge bioreactor was monitored over a one-year period using pyrosequencing of 16S rRNA genes. TTR was employed to quantify the bacterial taxa shifts based on the power law equation S = cTw. RESULTS: The power law exponent w for the full-scale bioreactor was 0.43 (R2 = 0.970), which is lower than that of the lab-scale bioreactor (w = 0.55, R2 = 0.971). The exponents for the dominant phyla were generally higher than that of the rare phyla. Canonical correspondence analysis (CCA) result showed that the bacterial community variance was significantly associated with water temperature, influent (biochemical oxygen demand) BOD, bioreactor scale and dissolved oxygen (DO). Variance partitioning analyses suggested that wastewater characteristics had the greatest contribution to the bacterial community variance, explaining 20.3% of the variance of bacterial communities independently, followed by operational parameters (19.9%) and bioreactor scale (3.6%). CONCLUSIONS: Results of this study suggest bacterial community dynamics were likely driven partly by wastewater and operational parameters and provide evidence that the TTR may be a fundamental ecological pattern in macro- and microbial systems.

Activated carbon fiber filler in aerated bioreactor for industrial wastewater treatment.

The aerated bioreactor is a promising technology for wastewater treatment. Activated carbon fiber (ACF) used as a biomembrane carrier in wastewater disposal has attracted much more concern recently. The high modulus polyacrylonitrile (PAN)-based ACF was successfully used as a biomembrane carrier for hard-to-biodegrade industrial organic wastewater disposal in a lab-scale aerated biomembrane reactor at room temperature. The biocompatibility test shows that the biomembrane grows quickly on the ACF filler (ACFF) surface; bacteria and microzoon can breed on the ACFF surface at high chemical oxygen demand (COD) concentration. The COD removal rate tests show that the ACFF bioreactor has high capability to remove COD.

[Phosphorus forms and its distribution characteristics in sediments and soils of water-level-fluctuating zone of the backwater reach from input river of Three Gorges Reservoir].

The contents of different phosphorus forms in surface sediments and the soils of water-level-fluctuating zone of the backwater reach from input river of Three Gorges Reservoirwere measured, using thestandard measurement and test (SMT) procedure of phosphorus forms in freshwater sediments. Correlation coefficients between phosphorus forms and sample geochemical characteristics, such as organic matter and major components were analyzed. The results indicated that the TP content in surface sediments varied from 483.4-848.4 mg/kg, and the average content was 569.0 mg/kg. The TP content in surface sediments placed in the mid-lower level, comparing with the TP content in surface sediment from the shallow lakes in the middle and lower reaches of Yangtze River. The TP content in soils of water-level-fluctuating zone varied from 488.9-1487.7 mg/kg, and the average content was 813.3 mg/kg. The average content of TP in soils of water-level-fluctuating zone whole exceeded the surface sediment, indicating of the influence of human's activity on phosphorus contents in soils of water-level-fluctuating zone. Distribution characteristics of phosphorus forms were different between the sediment and soils of water-level-fluctuating zone: (1) The ratio of IP/TP in the surface sediments (average value 55.7%) was higher than that in soils of water-level-fluctuating zone (average value 49.4%); (2) The domination phosphorus forms of IP in surface sediments was Ca-P (average ratio 83.5%), and the ratio of (Fe/Al-P)/IP was only 15%. The average ratio of Ca-P/IP in the soils of water-level-fluctuating zone was 73.9%, whereas the ratio of Fe/Al-P in IP raised to 22%; (3) The average content of active phosphorus (OP + Fe/Al-P) in surface sediment was 261.8 mg/kg, the average ratio of active phosphorus in TP was 49%, whereas the average content of active phosphorus (OP + Fe/Al-P) in soils of water-level-fluctuating zone was 405.7 mg/kg, the average ratio was 54%. The active phosphorus in soils of water-level-fluctuating zone would become potential pollution sources of water under correct environmental conditions,therefore, the potential impact of phosphorus on water eutrophication in soils of water-level-fluctuating zone couldn't be neglected.

Application of computational fluid dynamic to model the hydraulic performance of subsurface flow wetlands.

A subsurface flow wetland (SSFW) was simulated using a commercial computational fluid dynamic (CFD) code. The constructed media was simulated using porous media and the liquid resident time distribution (RTD) in the SSFW was obtained using the particle trajectory model. The effect of wetland configuration and operating conditions on the hydraulic performance of the SSFW were investigated. The results indicated that the hydraulic performance of the SSFW was predominantly affected by the wetland configuration. The hydraulic efficiency of the SSFW with an inlet at the middle edge of the upper media was 0.584 and the best among the SSFWs with an inlet at the top, the middle, and the bottom edge of the upper media. The constructed media affected the hydraulic performance by the ratio (K) of the upper and lower media resistance. The selection of appropriate media resistance in the protection layer can improve the hydraulic efficiency. When the viscous resistance coefficient of the media in the protection layer changed from 2.315 x 10(5) to 1.200 x 10(8), the hydraulic efficiency of the SSFW increased from 0.301 to 0.751. However, the effect of operating conditions on the hydraulic efficiency of the SSFW was slight.

[Application of two stage subsurface constructed wetland technology in cold area of northeast China].

Base on the two stage subsurface constructed wetland system running at the suburb of Siping city in Jilin province, the applicability and characteristics of the two stage system which had especial active media and measurements of isolation for temperature protection were studied and the advantages of the two stage system in the pollution removal were analyzed. The results showed that, the choice of especial active media and the measurements of isolation for temperature protection of the system made the two stage subsurface constructed wetland run efficiently in cold area and the system had very stable effects of the COD, BOD5, SS, NH4(+) -N and TP removal. In the whole process, the concentration of COD, BOD5 and SS in the outflow was about 16.01, 4.27 and 4.01 mg/L respectively and the concentration of NH4(+) -N and TP in the outflow was below 9.72 and 0.45 mg/L respectively. The subsurface wetland with two stages can overcome the disadvantage of the single system and improve the pollution removal efficiency.