Responses of microbial structures, functions, metabolic pathways and community interactions to different C/N ratios in aerobic nitrification

Deciphering linkages between DON and the microbial community for nitrogen removal using two green sorption media in a surface water filtration system

The presence of dissolved organic nitrogen (DON) in stormwater treatment processes is a continuous challenge because of the intertwined nature of its decomposition, bioavailability, and biodegradability and its unclear molecular characteristics. In this paper, 21 T Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) in combination with quantitative polymerase chain reaction was applied to elucidate the molecular change of DON and microbial population dynamics in a field-scale water filtration system filled with two specialty adsorbents for comparison in South Florida where the dry and wet seasons are distinctive annually. The adsorbents included CPS (clay-perlite and sand sorption media) and ZIPGEM (zero-valent iron and perlite-based green environmental media). Our study revealed that seasonal effects can significantly influence the dynamic characteristics and biodegradability of DON. The microbial population density in the filter beds indicated that three microbial species in the nitrogen cycle were particularly thrived for denitrification, dissimilatory nitrate reduction to ammonium, and anaerobic ammonium oxidation via competition and commensalism relationships during the wet season. Also, there was a decrease in the compositional complexity and molecular weight of the DON groups (CnHmOpN1, CnHmOpN2, CnHmOpN3, and CnHmOpN4), revealed by the 21 T FT-ICR MS bioassay, driven by a microbial population quantified by polymerase chain reaction from the dry to the wet season. These findings indirectly corroborate the assumption that the metabolism of microorganisms is much more vigorous in the wet season. The results affirm that the sustainable materials (CPS and ZIPGEM) can sustain nitrogen removal intermittently by providing a suitable living environment in which the metabolism of microbial species can be cultivated and enhanced to facilitate physico-chemical nitrogen removal across the two types of green sorption media.

Strong suppression of silver nanoparticles on antibiotic resistome in anammox process

This study comprehensively deciphered the effect of silver nanoparticles (AgNPs) on anammox flocculent sludge, including nitrogen removal performance, microbial community structure, functional enzyme abundance, antibiotic resistance gene (ARGs) dissemination, and horizontal gene transfer (HGT) mechanisms. After long-term exposure to 0-2.5 mg/L AgNPs for 200 cycles, anammox performance significantly decreased (P < 0.05), while the relative abundances of dominant Ca. Kuenenia and anammox-related enzymes (hzsA, nirK) increased compared to the control (P < 0.05). For antibiotic resistome, ARG abundance hardly changed with 0-0.5 mg/L AgNPs but decreased by approximately 90% with 1.5-2.5 mg/L AgNPs. More importantly, AgNPs effectively inhibited MGE-mediated HGT of ARGs. Additionally, structural equation model (SEM) disclosed the underlying relationship between AgNPs, the antibiotic resistome, and the microbial community. Overall, AgNPs suppressed the anammox-driven nitrogen cycle, regulated the microbial community, and prevented the spread of ARGs in anammox flocs. This study provides a theoretical baseline for an advanced understanding of the ecological roles of nanoparticles and resistance elements in engineered ecosystems.

Enhanced in-situ sludge reduction of the side-stream process via employing micro-aerobic approach in both mainstream and side-stream

Side-stream reactor (SSR), as an in-situ sludge reduction process with high sludge reduction efficiency (SRE) and less negative impact on effluent, has been widely researched. In order to reduce cost and promote large-scale application, the anaerobic/anoxic/micro-aerobic/oxic bioreactor coupled with micro-aerobic SSR (AAMOM) was used to investigate nutrient removal and SRE under short hydraulic retention time (HRT) of SSR. When HRT of SSR was 4 h, AAMOM system achieved 30.41% SRE, while maintaining carbon and nitrogen removal efficiency. Micro-aerobic in mainstream accelerated the hydrolysis of particulate organic matter (POM) and promoted denitrification. Micro-aerobic in side-stream increased cell lysis and ATP dissipation, thus increasing SRE. Microbial community structure indicated that the cooperative interactions among hydrolytic, slow growing, predatory and fermentation bacteria played key roles in improving SRE. This study confirmed that SSR coupled micro-aerobic was a promising and practical process, which could benefit nitrogen removal and sludge reduction in municipal wastewater treatment plants.

Effects of ultraviolet radiation on microorganism and nitrogen metabolism in sewage under plateau background

The experiments were conducted in the Tibetan plateau environment, and the sewage treatment conditions were designed with ultraviolet (UV) irradiation for 5 min, 10 min, 30 min, and 180 min. The Illumina MiSeq high-throughput sequencing technology was used to analyze the microbiological and metabolomic patterns of the plateau sewage treatment at the experimental scale, and then the response mechanisms of microbial and nitrogen metabolism in sewage treatment were explored. The abundance of metabolism at the first level and global and overview maps at the second level were higher in the plateau environment than in other regions. The KEGG pathway shows the effect of UV on nitrogen metabolism and its aptitude to improving or inhibit it. The two main nitrogen removal processes are nitrification and dissimilatory nitrate reduction. This study reveals the response of activated sludge to UV radiation in a plateau environment from microbiological and metabolomic perspectives, providing ideas and perspectives for the study of water treatment system methods, as well as laying a valuable theoretical foundation for the enhancement of plateau sewage treatment capacity.

Unravelling ciprofloxacin removal in a nitrifying moving bed biofilm reactor: Biodegradation mechanisms and pathways

Although moving bed biofilm reactors (MBBRs) have shown excellent antibiotic removal potentials, the information on underlying mechanisms is yet limited. This work assessed the removal of ciprofloxacin in an enriched nitrifying MBBR by clarifying the contribution of adsorption and microbial-induced biodegradation. Results demonstrated the considerable biomass adsorption (55%) in first 30 min. Limiting nitrite oxidizing bacteria growth or inhibiting nitrification would lead to lower adsorption capacities. The highest ciprofloxacin biodegradation rate constant was 0.082 L g SS^-1 h^-1 in the presence of ammonium, owing to ammonia oxidizing bacteria (AOB)-induced cometabolism, while heterotrophs played an insignificant role (∼9%) in ciprofloxacin biodegradation. The developed model also suggested the importance of AOB-induced cometabolism and metabolism over heterotrophs-induced biodegradation by analyzing the respective biodegradation coefficients. Cometabolic biodegradation pathways of ciprofloxacin mainly involved the piperazine ring cleavage, probably alleviating antimicrobial activities. It implies the feasibility of nitrifying biofilm systems towards efficient antibiotic removal from wastewater.

Effect of free nitrous acid on nitritation process: Microbial community, inhibitory kinetics, and functional biomarker

This work comprehensively deciphered the effect of free nitrous acid (FNA) on the microbial community, inhibitory kinetics, and nitrifiers in nitritation process. Nitritation was first successfully achieved through selective inhibition of free ammonia (FA) on nitrite oxidizers (NOB). Then, batch tests clearly showed that FNA significantly inhibits the ammonia oxidation rate (r_su) and the growth rate (μ) of ammonia oxidizers (AOB), which was well described by the Hellinga model (K_I = 0.222 mg·L^-1). The structural equation model indicated that FNA was significantly and negatively associated with r_su, μ, Nitrosomonas, Commamons, Nitrospira, and Nitrotoga and positively correlated with Paracoccus. Furthermore, Nitrosomonas significantly drove the ammonia utilization and growth of AOB and was identified as the most important functional biomarker indicating the nitritation in response to FNA levels using random forest model. This study provides helpful information on the kinetics of the mechanism underlying the FNA inhibition on nitrification.

Deciphering the antibiotic resistome and microbial community in municipal wastewater treatment plants at different elevations in eastern and western China

Antibiotic resistance genes (ARGs) as emerging environmental contaminants pose severe global risks to public health and ecosystems. Municipal wastewater treatment plants (WWTPs) are crucial transmitters for the dissemination and propagation of ARGs into receiving water bodies via mobile genetic elements (MGEs). However, the comprehensive and deep deciphering of the diversity, abundance, and potential hosts of ARGs in two distinct altitudinal WWTPs is scarce. In this work, we revealed the elevational distribution characteristics of the resistance genes and microbial community of six WWTPs from two distinct geographical zones: a low-elevation (LE) region (Shandong, 10-22 m above sea level) and a high-elevation (HE) region (Gansu, 1,520-1,708 m above sea level). Significant elevational variations in the diversity and relative abundance of resistance genes were observed. Wastewater treatment could significantly reduce the concentrations of ARGs and MGEs by about 1-2 and 2-3 orders of magnitude, respectively. However, above 69.95% of resistance genes were enriched in effluent. In particular, 24 ARG subtype, 3 MGE subtypes, and 59 bacterial genera were persistent in all samples. More potential hosts for ARGs in LE region and more abundant human gut microbiota in HE region were identified. This work provides helpful information for controlling the spread of ARGs for their management and assessment, thereby mitigating the risks of ARGs in WWTPs.

Characterization of a novel micro-pressure double-cycle reactor for low temperature municipal wastewater treatment

To solve the deterioration of effluent caused by low temperature in urban sewage treatment plant in cold areas, a new type of reactor was proposed, the biochemical environmental and low-temperature operating characteristics of the reactor were studied. Through analysis of flow simulation and dissolved oxygen (DO) distribution when the aeration rate was 0.6 m³/h, it showed that there were many different DO environments in the reactor at the same time, which provided favourable conditions for various biochemical reactions. The operation test showed that the average effluent removal rate of COD, TN, NH₄⁺-N and TP was 92.53%, 74.57%, 89.61% and 96.04%, respectively. And there were a variety of functional bacteria related to nitrogen and phosphorus removal in the system, most of them with strong adaptability at low temperatures. Among the dominant microorganisms, Flavobacterium and Rhodobacter were related to denitrification, Aeromonas and Thiothrix were related to phosphorous removal. Denitrifying phosphorus removal was the main way of phosphorus removal. Picrust2 results showed that the reactor operated well at low temperature, and the regional difference distribution of nitrification genes further confirmed the existence of functional zones in the reactor. The results showed that the Micro-pressure Double-cycle reactor worked well at low temperature, which provided a new idea and way for the upgrading of urban sewage treatment plants in cold areas.

Characterization of non-taste & odor produced aerobic denitrification actinomycetes strains Streptomyces spp. isolated from reservoir ecosystem: Denitrification performance and carbon source metabolism

The aerobic denitrification performance of actinomycetes was investigated. Two strains of actinomycetes were isolated and identified as Streptomyces sp. LJH-12-1 and Streptomyces diastatochromogenes LJH-12-2. Strain LJH-12-1 could remove 94% of organic carbon and 91% of total nitrogen. Meanwhile, strain LJH-12-2 could reduce 96% of organic carbon and 93% of total nitrogen. Two strains of actinomycetes revealed excellent carbon source metabolism activity. Moreover, the total nitrogen removal efficiencies were 69%, and 54%, respectively for strains LJH-12-1, and LJH-12-2 during the micro-polluted landscape raw water treatment. Futhermore, strains LJH-12-1 and LJH-12-2 could utilize aromatic proteins, soluble microbial products, and humic acid to drive aerobic denitrification processes in the landscape water bodies. These results will provide a new insight into applying aerobic denitrification actinomycetes to treat micro-polluted water bodies.

Deciphering the microbial community structures and functions of wastewater treatment at high-altitude area

Introduction: The proper operation of wastewater treatment plants is a key factor in maintaining a stable river and lake environment. Low purification efficiency in winter is a common problem in high-altitude wastewater treatment plants (WWTPs), and analysis of the microbial community involved in the sewage treatment process at high-altitude can provide valuable references for improving this problem. Methods: In this study, the bacterial communities of high- and low-altitude WWTPs were investigated using Illumina high-throughput sequencing (HTS). The interaction between microbial community and environmental variables were explored by co-occurrence correlation network. Results: At genus level, Thauera (5.2%), unclassified_Rhodocyclaceae (3.0%), Dokdonella (2.5%), and Ferribacterium (2.5%) were the dominant genera in high-altitude group. The abundance of nitrogen and phosphorus removal bacteria were higher in high-altitude group (10.2% and 1.3%, respectively) than in low-altitude group (5.4% and 0.6%, respectively). Redundancy analysis (RDA) and co-occurrence network analysis showed that altitude, ultraviolet index (UVI), pH, dissolved oxygen (DO) and total nitrogen (TN) were the dominated environmental factors (p < 0.05) affecting microbial community assembly, and these five variables explained 21.4%, 20.3%, 16.9%, 11.5%, and 8.2% of the bacterial assembly of AS communities. Discussion: The community diversity of high-altitude group was lower than that of low-altitude group, and WWTPs of high-altitude aeras had a unique microbial community structure. Low temperature and strong UVI are pivotal factors contributing to the reduced diversity of activated sludge microbial communities at high-altitudes.

Ecological restoration performance enhanced by nano zero valent iron treatment in constructed wetlands under perfluorooctanoic acid stress

Perfluorooctanoic acid (PFOA) of widespread use can enter constructed wetlands (CWs) via migration, and inevitably causes negative impacts on removal efficiencies of conventional pollutants due to its ecotoxicity. However, little attention has been paid to strengthen performance of CWs under PFOA stress. In this study, influences of nano zero valent iron (nZVI), which has been demonstrated to improve nutrients removal, were explored after exemplifying threats of PFOA to operation performance in CWs. The results revealed that 1 mg/L PFOA suppressed the nitrification capacity and phosphorus removal, and nZVI distinctly improved the removal efficiency of ammonia and total phosphorus in CWs compared to PFOA exposure group without nZVI, with the maximum increases of 3.65 % and 16.76 %. Furthermore, nZVI significantly stimulated dehydrogenase (390.64 % and 884.54 %) and urease (118.15 % and 246.92 %) activities during 0-30 d and 30-60 d in comparison to PFOA group. On the other hand, nitrifying enzymes were also promoted, in which ammonia monooxygenase increased by 30.90 % during 0-30 d, and nitrite oxidoreductase was raised by 117.91 % and 232.10 % in two stages. Besides, the content of extracellular polymeric substances (EPS) under nZVI treatment was 72.98 % higher than PFOA group. Analyses of Illumina Miseq sequencing further certified that nZVI effectively improved the community richness and caused the enrichment of microorganisms related to nitrogen and phosphorus removal and EPS secreting. These results could provide valuable information for ecological restoration and decontamination performance enhancement of CWs exposed to PFOA.

Study on the mechanisms of enhanced biological nitrogen and phosphorus removal by denitrifying phosphorus removal in a Micro-pressure swirl reactor

To reveal the mechanisms of enhanced biological nitrogen and phosphorus removal by denitrifying phosphorus removal in a Micro-pressure swirl reactor (MPSR), this study used a MPSR to treat municipal wastewater and enriched denitrifying phosphate accumulating organisms (DPAOs) by using its alternating anaerobic-anoxic-aerobic environment. The coupling of denitrification phosphorus removal (DPR) and simultaneous nitrification endogenous denitrification phosphorus removal (SNEDPR) was achieved in MPSR, and the average removal rates of COD, NH4+-N, TN and TP were 91.57%, 98.51%, 85.88%, 96.08% respectively. The results of the batch experiments showed that DPAOs activity in the low dissolved oxygen (DO) and high DO zones were 70.5% and 74.3%. The results of intracellular carbon source conversion patterns, microbial assays and functional gene prediction indicated that Flavobacterium and Dechloromonas dominated the DPR process in the low DO zone. Based on these findings, nutrient removal pathways within the MPSR were integrated.

Effect of carbon source conditions on response of nitrifying sludge to 3,5-dichlorophenol

Nutritional conditions of activated sludge had a significant influence on nitrification inhibition response. This study comprehensively investigated the inhibition of 3,5-dichlorophenol (3,5-DCP) on nitrification of activated sludge with different C/N ratios and carbon source types. The corresponding extracellular polymeric substances (EPS), microbial communities and functional genes were analysed. The results indicated that the addition of carbon source would reduce the nitrification activity and nitrification sensitivity to 3,5-DCP, and the order of the EC₅₀ was sequenced as sodium acetate > methanol > glucose. The response mechanisms of activated sludge under diverse carbon source conditions to 3,5-DCP were summarised as follows. When the 3,5-DCP content was increased from 0.4 mg/L to 0.8 mg/L, the protein content increased from 73.2 ± 2.6 mg/g SS ∼122.4 ± 4 mg/g SS to 92.2 ± 11.2 mg/g SS ∼130.8 ± 9.6 mg/g SS in the tightly bound EPS (TB-EPS). The increase of protein content was attributed to cellular self-protection mechanisms. Furthermore, fluorescence characteristic analysis revealed that tyrosine and tryptophan in loosely bound EPS (LB-EPS) might account for higher EC₅₀ in activated sludge fed with methanol and sodium acetate. In addition, the redundancy analyses (RDA) showed activated sludge with organics enriched the resistant species, such as Proteobacteria and Patescibacteria, while activated sludge without organics enriched the sensitive species, such as Ferruginibacter. Finally, the nitrification genes were found to be consistent with nitrification activity. Thus, the findings provide new insights into nitrification inhibition mechanism under different carbon source conditions.

Succession of function, assembly, and interaction of microbial community in sequencing biofilm batch reactors under selenite stress

The mechanism of interaction between selenite, a toxic substance, and the microbial community in wastewater is still not well understood. Herein, nine sequencing biofilm batch reactors were used to systematically investigate the response of the microbial community to the continuous selenite stress. The results showed that selenite affected the reactor performance and reduced the biofilm mass. Also, it increased the proportion of the living cells, and changed the protein and polysaccharide composition of the biofilm as well as cellular secretions. Selenite facilitated the removal of NO₃-N, according to water-quality and bioinformatics analyses. As such, the selenite was converted into selenium nanoparticles. α-diversity analysis further revealed that 20 μM selenite enhanced the microbial community resilience, while 200 μM selenite had the reverse effect. Community composition analysis showed that Variovorax, Rhizobium, and Simkania had positive correlations with selenite (P < 0.05). Functional prediction suggested that selenite changed the C, N, and S cycle functions. Furthermore, determinism dominated the community assembly process, and the deterministic proportion increased with the increase of selenite concentration. Network analysis showed that selenite improved the stability and positive correlation ratio of the overall microbial network, and accelerated the communication between microorganisms. However, when compared with the 20 μM selenite, the 200 μM selenite boosted the competition and parasitism/predation among microorganisms. Low-abundance genera played a key role in the network of selenite-reducing microbial community. In addition, under selenite stress, biofilm network exhibited better stability and faster information exchange than suspended network, and the positive association between biofilm and suspended microorganisms increased. All in all, this research sheds light on the interaction between selenite and microbial community, as well as provides crucial information on selenium-containing wastewater.

Correlation of microbial dynamics to odor production and emission in full-scale sewage sludge composting

Odor is inevitably produced during sewage sludge composting, and the subsequent pollution hinders the further development of composting technologies. Third-generation high-throughput sequencing was used to analyze microbial community succession, and the correlations between odor and microbial communities were evaluated. Hydrogen sulfide (47.5-87.9 %) and ammonia (9.4-49.9 %) contributed majorly to odor emissions, accounting for 93.7-98.5 % of the emissions. Volatile sulfur compounds were mainly produced in the mesophilic and pre-thermophilic phases (43.0-83.4 %), whereas ammonia was mainly produced in the thermophilic phase (52.1-59.4 %). Microorganisms dominant in the mesophilic and thermophilic phases correlated positively with odor production in the following order: Rhodocyclaceae > Clostridiaceae_1 > Hyphomicrobiaceae > Acidimicrobiales > Family_XI, whereas those dominant in the cooling phase showed negative correlations with odor production in the following order: Bacillus > Sphingobacteriaceae > Pseudomonadaceae > DSSF69 > Chitinophagaceae. The back mixing of mature compost is expected to serve as an economical measure for controlling odor during sewage sludge composting.

Microbial composition and nitrogen removal pathways in a novel sequencing batch reactor integrated with semi-fixed biofilm carrier: evidence from a pilot study for low- and high-strength sewage treatment

The sequencing batch reactor (SBR) activated sludge process is a well-established technology for sewage treatment. One of the drawbacks of SBRs, however, total nitrogen (TN) removals is insufficient. By means of introducing four improvements, including semi-fixed biofilm carrier, sludge elevation mixing and change for the mode of influent and effluent, compliant standard for TN discharge was obtained in this novel SBR configuration during low- and high-strength sewage load. To illustrate the microbial compositions and functions of the attached biofilm on semi-fixed carrier and the suspended aggregates, as well as the nitrogen removal pathway, high throughput 16S rRNA gene amplicon sequencing, PICRUSt2 algorithm, and KEGG database were applied. The results revealed that (i) the microbial communities from suspended aggregates and biofilm samples were significantly different from each other; (ii) during low-strength sewage loads, TN removal was mainly by nitrification-denitrification. The suspended aggregates was responsible for denitrification, while the biofilm was focused on ammonium oxidation; (iii) during high-strength sewage loads, function of nitrate reductase from suspended aggregates was faded, and anammox and N assimilation by biofilm became dominant. Meanwhile, TN removal referring to the formation of L-glutamine via assimilation was the main pathway.

Influence of biofilm thickness on the removal of thirteen different organic micropollutants via a Membrane Aerated Biofilm Reactor (MABR)

The presence of organic micropollutants (OMPs) in natural water bodies has become an emerging concern due to their fast dissemination into natural water sources, high persistence, ubiquitous nature, and detrimental impact on the environment and human health. This study evaluated the Membrane Aerated Biofilm Reactor (MABR) efficiency in the removal of 13 OMPs commonly reported in water. Results demonstrated that OMPs removal is dependent on biofilm thickness and bacterial cell density, microbial community composition and physicochemical properties of OMPs. Effective removals of ammonium and organic carbon (COD, >50%), acetaminophen (70%) and triclosan (99%) were obtained even at early stages of biofilm development (thickness < 0.33 mm, 2.9 ×10⁵ cell mL^-1). An increase in biofilm thickness and cell density (1.02 mm, 2.2 ×10⁶ cell mL^-1) enhanced the system performance. MABR achieved over 90% removal of nonpolar, hydrophobic and hydrophilic OMPs and 22-69% removal of negatively charged and acidic OMPs. Relative abundances of Zoogloea, Aquabacterium, Leucobacter, Runella, and Paludilbaculum bacteria correlated with the removal of certain OMPs. In addition, MABR achieved up to 96% nitrification and 80% overall COD removal by the end of the experiment. The findings from this study demonstrated MABRs to be a feasible option to treat municipal wastewater polluted by OMPs.

Ammonium-assimilating microbiome: A halophilic biosystem rationally optimized by carbon to nitrogen ratios with stable nitrogen conversion and microbial structure

The contradiction between theoretical metabolism of ammonium assimilation and experiential understanding of conventional biosystems makes the rational optimization of the ammonium-assimilating microbiome through carbon to nitrogen (C/N) ratios perplexing. The effect of different C/N ratios on ammonium-assimilating biosystems was investigated in saline wastewater treatment. C/N ratios significantly hindered the nutrient removal efficiency, but ammonium-assimilating biosystems maintained functional stability in nitrogen conversions and microbial communities. With sufficient biomass, higher than 86% ammonium and 73% phosphorus were removed when C/N ratios were higher than 25. Ammonium assimilation dominated the nitrogen metabolism in all biosystems even under relatively low C/N ratios, evidenced by the extremely low abundances of nitrification functional genes. Different C/N ratios did not significantly change the bacterial community structure of ammonium-assimilating biosystems. It is anticipated that the ammonium-assimilating biosystem with advantages of clear metabolic pathway and easy optimization can be applied to nutrient removal and recovery in saline environments.

The effects of electric field assisted composting on ammonia and nitrous oxide emissions varied with different electrolytes

Enhancing electron transfer through directly elevating electric potential has been verified to reduce gaseous emissions from composting. Reducing electric resistance of composting biomass might be a choice to further strengthening electron transfer. Here, the effects of chemical electrolytes addition on gaseous Nitrogen emission in electric field assistant composting were investigated. Results suggest that adding acidic electrolyte (ferric chloride) significantly reduced ammonia (NH3) emission by 72.1% but increased nitrous oxide (N2O) emission (by 24-fold) (P < 0.05), because of a dual effect on nitrifier activity: i) an elevated abundance and proportion of ammonia oxidizing bacteria Nitrosomonadaceae, and ii) delayed growth of nitrite oxidizing bacteria. Neutral and alkaline electrolytes had no negative or positive effect on N2O or NH3 emission. Hence, there is a potential trade-off between NH3 and N2O mitigation if using ferric chloride as acidic electrolyte, and electrolyte addition should aim to enhance electron production promote N2O mitigation.

Efficient removal of organic compounds from shale gas wastewater by coupled ozonation and moving-bed-biofilm submerged membrane bioreactor

Shale gas wastewater (SGW) with complex composition and high salinity needs an economical and efficient method of treatment with the main goal to remove organics. In this study, a coupled system consisting of ozonation and moving-bed-biofilm submerged membrane bioreactor (MBBF-SMBR) was comprehensively evaluated for SGW treatment and compared with a similar train comprising ozonation and submerged membrane bioreactor (SMBR) without addition of carriers attaching biofilm. The average removal rates of MBBF-SMBR were 77.8% for dissolved organic carbon (DOC) and 37.0% for total nitrogen (TN), higher than those observed in SMBR, namely, 73.9% for DOC and 18.6% for TN. The final total membrane resistance in SMBR was 40.1% higher than that in MBBF-SMBR. Some genera that specifically contribute to organic removal were identified. Enhanced gene allocation for membrane transport and nitrogen metabolism was found in MBBF-SMBR biofilm, implying that this system has significant industrial application potential for organics removal from SGW.

Nitrifier denitrification dominates nitrous oxide production in composting and can be inhibited by a bioelectrochemical nitrification inhibitor

Targeted options to reduce nitrous oxide (N₂O) emission from composting is scarce due to challenges in disentangling the complex N₂O production pathways. Here, combined approaches of nitrogen form analysis, isotopocule mapping, quantitative PCR, and Illumina MiSeq sequencing were used to differentiate N₂O production pathways and decipher the underlying biochemical mechanisms. Results suggested that most N₂O was produced at the latter stage through nitrifier denitrification. The bioelectrochemical assistance through applying an electric potential reduced N₂O emissions by 28.5-75.5%, and the underlying mitigation mechanism was ammonia oxidation repression, as evidenced by the observed reduction in the proportion of the amoA containing family Nitrosomonadaceae from 99% to 83% at the lower voltage and to a negligible level at the higher voltage assessed, which was attributed to their depressed competitiveness for oxygen with heterotrophs. The findings provide evidence that the bioelectrochemical assistance could function as a nitrification inhibitor to minimize compost derived N₂O emissions.

Per-, poly-fluoroalkyl substances (PFASs) pollution in benthic riverine ecosystem: Integrating microbial community coalescence and biogeochemistry with sediment distribution

Per-, Poly-fluoroalkyl substances (PFASs) accumulation in benthic environments is mainly determined by material mixing and represents a significant challenge to river remediation. However, less attention has been paid to the effects of sediment distribution on PFASs accumulation, and how PFASs influence microbial community coalescence and biogeochemical processes. In order to identify correlations between PFASs distribution and benthic microbial community functions, we conducted a field study and quantified the ecological constrains of material transportation on benthic microorganisms. Perfluorohexanoic acid (PFHxA) contributed most to the taxonomic heterogeneity of both archaeal (12.199%) and bacterial (13.675%) communities. Genera Methanoregula (R² = 0.292) and Bacillus (R² = 0.791) were identified as indicators that respond to PFASs. Phylogenetic null modeling indicated that deterministic processes (50.0-82.2%) dominated in spatial assembly of archaea, while stochasticity (94.4-97.8%) dominated in bacteria. Furthermore, spatial mixing of PFASs influenced broadly in nitrogen cycling of archaeal genomes, and phosphorus mineralization of bacterial genomes (p < 0.05). Overall, we quantified the effect of PFASs on community assembly and highlighted the constrains of PFASs influence on benthic geochemical potentials, which may provide new insights into riverine remediation.

Planktonic microbial responses to perfluorinated compound (PFC) pollution: Integrating PFC distributions with community coalescence and metabolism

The presence of perfluorinated compound (PFC) contamination in riverine ecosystems represents a novel challenge for environmental remediation. However, little attention has been paid to how PFCs affect planktonic microbial community coalescence. Here, the spatial profiles of fourteen PFCs and their contributions to community assembly were determined using field sampling in a natural river confluence. Overall, PFPeA (perfluorovaleric acid), PFBS (perfluorobutylsulfonate), PFHpA (perfluoroheptanoic acid) and PFHxA (perfluorohexanoic acid) were identified as important indicators of PFC pollution, accounting for the majority of the spatial heterogeneity in PFC pollution. PFPeA (perfluorovaleric acid) (9.39%) and PFTrDA (perfluorotridecanoate acid) (8.61%) contributed more to microbial taxonomic spatial heterogeneity than did other factors, such as pH, dissolved oxygen and velocity. PFOA (pentadecafluorooctanoic acid) (R² = 0.353) and PFBS (R² = 0.297) drove turnover in archaeal communities within river sections (transversely), while PFHpA (R² = 0.251) and PFOS (perfluorooctane sulphonate) (R² = 0.105) drove turnover in bacterial communities transversely and longitudinally, respectively. Phylogenetic null modeling suggested that archaeal (68.89-83.33%) community assembly was dominated by stochastic processes, and was balanced by PFHxA (R² = 0.349) and PFOA (R² = 0.290). Furthermore, PFOS inhibited the biosynthesis of several key amino acids in archaea, and PFBA enhanced the potential for bacterial infections in humans (p < 0.05), threatening water quality. In sum, this study provides new insights into riverine ecological risk management.

Response of wastewater treatment performance, microbial composition and functional genes to different C/N ratios and carrier types in MBBR inoculated with heterotrophic nitrification-aerobic denitrification bacteria

To operate the moving bed biofilm reactor inoculated with HN-AD bacteria (B-MBBR) instead of activated sludge for livestock and poultry breeding wastewater (LPBW) disposal in most efficient manner, nitrogen removal (NR) efficiency and microbial composition of two MBBRs with different carrier types under various C/N ratios were explored. Results indicated that the performance on NR greatly various in different carrier types under various C/N ratios. Attributing to the bacterial protection provided by the porous structure of polyvinyl alcohol (PVA) gel, MBBR using PVA gel as the carrier exhibited a more stable NR performance (range from 78.05% to 83.76%) versus that using Kaldnes (K1) as the carrier (range from 78.05% to 83.76%). Besides, microbial analysis indicated that MBBR with PVA gel as the carrier is conducive to the growth of oligotrophic and HN-AD bacteria (Paracoccus and Acinetobacter), and the highest relative abundance was 16.37% at C/N ratio of 6.

Genome- and community-level interaction insights into the ecological role of archaea in rare earth element mine drainage in South China

Microbial communities play crucial roles in mine drainage generation and remediation. Despite the wide distribution of archaea in the mine ecosystem, their diversity and ecological roles remain less understood than bacteria. Here, we retrieved 56 archaeal metagenome-assembled genomes from a river impacted by rare earth element (REE) mining activities in South China. Genomic analysis showed that archaea represented four distinct lineages, including phyla of Thaumarchaeota, Micrarchaeota, Nanoarchaeota and Thermoplasmata. These archaea represented a considerable fraction (up to 40%) of the total prokaryote community, which might contribute to nitrogen and sulfur cycling in the REE mine drainage. Reconstructed metabolic potential among diverse archaea taxa revealed that archaea were involved in the network of ammonia oxidation, denitrification, sulfate redox reaction, and required substrates supplied by other community members. As the dominant driver of ammonia oxidation, Thaumarchaeota might provide substrates to support the survival of two nano-sized archaea belonging to Micrarchaeota and Nanoarchaeota. Despite the absence of biosynthesis pathways for amino acids and nucleotides, the potential capacity for nitrite reduction (nirD) was observed in Micrarchaeota, indicating that these nano-sized archaea encompassed diverse metabolisms. Moreover, Thermoplasmata, as keystone taxa in community, might be the main genetic donor for the other three archaeal phyla, transferring many environmental resistance related genes (e.g., V/A-type ATPase and Vitamin B12-transporting ATPase). The genetic interactions within archaeal community through horizontal gene transfer might be the key to the formation of archaeal resistance and functional partitioning. This study provides putative metabolic and genetic insights into the diverse archaea taxa from community-level perspectives, and highlights the ecological roles of archaea in REE contaminated aquatic environment.

The fate and long-term toxic effects of NiO nanoparticles at environmental concentration in constructed wetland: Enzyme activity, microbial property, metabolic pathway and functional genes

Although the potential threats of metallic oxide nanoparticles (MNPs) to constructed wetland (CW) have been broadly reported, limited information is available regarding the long-term impact of nickel oxide nanoparticles (NiO NPs) on CWs at the environmentally relevant concentrations. Here, we comprehensively elucidated the responses in the treatment performance, enzyme activities, microbial properties, metabolic pathways and functional genes of CWs to chronic exposure of NiO NPs (0.1 and 1 mg/L) for 120 days, with a quantitative analysis on the fate and migration of NiO NPs within CWs. Nitrogen removal evidently declined under the long-term exposure to NiO NPs. Besides, NiO NPs induced a deterioration in phosphorus removal, but gradually restored over time. The activities of dehydrogenase (DHA), phosphatase (PST), urease (URE), ammonia oxygenase (AMO) and nitrate reductase (NAR) were inhibited to some extent under NiO NPs stress. Furthermore, NiO NPs exposure reduced bacterial diversity, shifted microbial composition and obviously inhibited the transcription of the ammonia oxidizing and denitrifying functional genes. The results of nickel mass balance indicated that the major removal mechanism of NiO NPs in CWs was through substrate adsorption and plants uptake. Thus, the ecological impacts of prolonged NiO NPs exposure at environmental concentrations should not be neglected.

Microbial diversity characteristics and the influence of environmental factors in a large drinking-water source

Although the influence of environmental factors on the microbial community in water sources is crucial, it is seldom evaluated. The seasonal relationship between microbial diversity of bacteria and fungi and environmental factors was investigated in a large drinking-water reservoir using Illumina MiSeq sequencing. Forty-one bacterial phyla and nine fungal phyla were analyzed in the Qingcaosha Reservoir, Shanghai, China. The predominant bacterial phyla were Actinobacteria, Proteobacteria, Bacteroidetes, and Cyanobacteria, with the maximum relative abundance of 46%, 36.6%, 16.1%, and 14.9%, respectively. Actinobacteria were observed to be the predominant bacterial phylum during spring and summer. The maximum relative abundance of unclassified fungi appeared in summer (98.8%), which was higher than that of Ascomycota and Basidiomycota (11.7% and 8.2%, respectively). Principal coordinate analysis (PCoA) results showed that the structural similarity in the bacterial community was greater during summer and winter; however, the fungal community exhibited a greater similarity during spring and summer. 2-Methylisoborneol (2-MIB), an olfactory compound produced by microorganisms, was detected at a concentration of 8.97 ng/L during summer, which was slightly lower than the olfactory threshold (10 ng/L). The positive correlation between Actinobacteria and unclassified fungi and 2-MIB (p < 0.05) confirmed that Actinobacteria and unclassified fungi produced 2-MIB. The chemical oxygen demand (COD) was 1.48-1.94 mg/L, and the maximum concentrations of total nitrogen (TN) and total phosphorus (TP) were 2.1 mg/L and 0.5 mg/L, respectively. Chloroflexi were negatively correlated with COD (p < 0.05) but positively correlated with TP (p < 0.01). Nitrospirae were negatively correlated with COD (p < 0.05), but positively correlated with TN (p < 0.05). Among the classified fungi, Rozellomycota, Basidiomycota (p < 0.05), and Chytridiomycota (p < 0.01) were positively correlated with TP. Therefore, the relative abundance of predominant bacteria was affected by various environmental factors; however, fungi were mainly influenced by TP.