Mixotrophic aerobic denitrification facilitated by denitrifying bacterial-fungal communities assisted with iron in micro-polluted water: Performance, metabolic activity, functional genes abundance, and community co-occurrence.

Low-dosage nitrate pollutants can contribute to eutrophication in surface water bodies, such as lakes and reservoirs. This study employed assembled denitrifying bacterial-fungal communities as bio-denitrifiers, in combination with zero-valent iron (ZVI), to treat micro-polluted water. Immobilized bacterial-fungal mixed communities (IBFMC) reactors demonstrated their ability to reduce nitrate and organic carbon by over 43.2 % and 53.7 %, respectively. Compared to IBFMC reactors, IBFMC combined with ZVI (IBFMC@ZVI) reactors exhibited enhanced removal efficiencies for nitrate and organic carbon, reaching the highest of 31.55 % and 17.66 %, respectively. The presence of ZVI in the IBFMC@ZVI reactors stimulated various aspects of microbial activity, including the metabolic processes, electron transfer system activities, abundance of functional genes and enzymes, and diversity and richness of microbial communities. The contents of adenosine triphosphate and electron transfer system activities enhanced more than 5.6 and 1.43 folds in the IBFMC@ZVI reactors compared with IBFMC reactors. Furthermore, significant improvement of crucial genes and enzyme denitrification chains was observed in the IBFMC@ZVI reactors. Iron played a central role in enhancing microbial diversity and activity, and promoting the supply, and transfer of inorganic electron donors. This study presents an innovative approach for applying denitrifying bacterial-fungal communities combined with iron enhancing efficient denitrification in micro-polluted water.

Comparing Mn-based oxides filters started by KMnO4 versus K2FeO4 for ammonium and manganese removal: Formation mechanism of active species.

A pilot-scale filtration system was adopted to prepare filter media with catalytic activity to remove manganese (Mn2+) and ammonium (NH4+-N). Three different combinations of oxidants (KMnO4 and K2FeO4) and reductants (MnSO4 and FeCl2) were used during the start-up period. Filter R3 started up by KMnO4 and FeCl2 (Mn7+→MnOx) exhibited excellent catalytic property, and the NH4+-N and Mn2+ removal efficiency reached over 80% on the 10th and 35th days, respectively. Filter R1 started up by K2FeO4 and MnSO4 (MnOx←Mn2+) exhibited the worst catalytic property. Filter R2 started up by KMnO4 and MnSO4 (Mn7+→MnOx←Mn2+) were in between. According to Zeta potential results, the Mn-based oxides (MnOx) formed by Mn7+→MnOx performed the highest pHIEP and pHPZC. The higher the pHIEP and pHPZC, the more unfavorable the cation adsorption. However, it was inconsistent with its excellent Mn2+ and NH4+-N removal abilities, implying that catalytic oxidation played a key role. Combined with XRD and XPS analysis, the results showed that the MnOx produced by the reduction of KMnO4 showed early formation of buserite crystals, high degree of amorphous, high content of Mn3+ and lattice oxygen with the higher activity to form defects. The above results showed that MnOx produced by the reduction of KMnO4 was more conducive to the formation of active species for catalytic oxidation of NH4+-N and Mn2+ removal. This study provides new insights on the formation mechanisms of the active MnOx that could catalytic oxidation of NH4+-N and Mn2+.

Molecular-level insight into the behavior of metal cations and organic matter during the aggregation of polystyrene nanoplastics.

In this study, the behavior of metal cations and organic matter during polystyrene nanoplastics (PSNP) aggregation was explored combing experimental measurements and molecular dynamics simulation. The results indicated that coexisting organic matter, including organic pollutants and humic acid (HA), play a complex role in determining PSNP aggregation. The representative organic pollutant, bisphenol A, exhibited competitive behavior with HA during heteroaggregation, and the heteroaggregation between HA and PSNP was impaired by bisphenol A. The bridging effect of metal ions in aggregation is related to their interaction strength with functional groups, binding affinity with water molecules, and concentration. In particular, Mg2+ interacts more strongly with oxygen-containing functional groups on PSNP than Ca2+. However, Mg2+ is more favorable for binding with water and is therefore not as effective as Ca2+ for destabilizing PSNP. Compared with Ca2+ and Mg2+, Na+ showed a weaker association with PSNP; however, it still showed a significant effect in determining the aggregation behavior of PSNP owing to its high concentration in seawater. Overall, we provided a molecular-level understanding of PSNP aggregation and deepened our understanding of the fate of nanoplastics.

Stratified control of chemical crystallization in a pellet fluidized bed for pH-Adjusted fluoride and phosphate reduction: An experimental study.

Chemical crystallization granulation in a fluidized bed offers an environmentally friendly technology with significant promise for fluoride removal. This study investigates the impact of stratified pH control in a crystallization granulation fluidized bed for the removal of fluoride and phosphate on a pilot scale. The results indicate that using dolomite as a seed crystal, employing sodium dihydrogen phosphate (SDP) and calcium chloride as crystallizing agents, and controlling the molar ratio n(F):n(P):n(Ca) = 1:5:10 with an upflow velocity of 7.52 m/h, effectively removes fluoride and phosphate. Stratified pH control-maintaining weakly acidic conditions (pH = 6-7) at the bottom and weakly alkaline conditions (pH = 7-8) at the top-facilitates the induction of fluoroapatite (FAP) and calcium phosphate crystallization. This approach reduces groundwater fluoride levels from 9.5 mg/L to 0.2-0.6 mg/L and phosphate levels to 0.1-0.2 mg/L. Particle size analysis, scanning electron microscopy-energy-dispersive X-ray spectroscopy, and X-ray diffraction physical characterizations reveal significant differences in crystal morphology between the top and bottom layers, with the lower layer primarily generating high-purity FAP crystals. Further analysis shows that dolomite-induced FAP crystallization offers distinct advantages. SDP not only dissolves on the dolomite surface to provide active sites for crystallization but also, under weakly acidic conditions, renders both dolomite and FAP surfaces negatively charged. This allows for the effective adsorption of PO43-, HPO42-, and F- anions onto the crystal surfaces. This study provides supporting data for the removal of fluoride from groundwater through induced FAP crystallization in a chemical crystallization pellet fluidized bed.

Simultaneous removal of ammonia nitrogen, phosphate, zinc, and phenol by degradation of cellulose in composite mycelial pellet bioreactor: Enhanced performance and community co-assembly mechanism.

In this experiment, the prepared tea biochar-cellulose@LDH material (TB-CL@LDH) was combined with mycelium pellets to form the composite mycelial pellets (CMP), then assembled and immobilized with strains Pseudomonas sp. Y1 and Cupriavidus sp. ZY7 to construct a bioreactor. At the best operating parameters, the initial concentrations of phosphate (PO43--P), ammonia nitrogen (NH4+-N), chemical oxygen demand (COD), zinc (Zn2+), and phenol were 22.3, 25.0, 763.8, 1.0, and 1.0 mg L-1, the corresponding removal efficiencies were 80.4, 87.0, 83.4, 91.8, and 96.6%, respectively. Various characterization analyses demonstrated that the strain Y1 used the additional carbon source produced by the strain ZY7 degradation of cellulose to enhance the removal of composite pollutants and clarified the principle of Zn2+ and PO43--P removal by adsorption, co-precipitation and biomineralization. Pseudomonas and Cupriavidus were the dominant genera according to the high-throughput sequencing. As shown by KEGG results, nitrification and denitrification genes were affected by phenol. The study offers prospects for the simultaneous removal of complex pollutants consisting of NH4+-N, PO43--P, Zn2+, and phenol.

Algicidal activity synchronized with nitrogen removal by actinomycetes: Algicidal mechanism, stress response of algal cells, denitrification performance, and indigenous bacterial community co-occurrence.

The harmful algal blooms (HABs) can damage the ecological equilibrium of aquatic ecosystems and threaten human health. The bio-degradation of algal by algicidal bacteria is an environmentally friendly and economical approach to control HABs. This study applied an aerobic denitrification synchronization algicidal strain Streptomyces sp. LJH-12-1 (L1) to control HABs. The cell-free filtrate of the strain L1 showed a great algolytic effect on bloom-forming cyanobacterium, Microcystis aeruginosa (M. aeruginosa). The optimal algicidal property of strain L1 was indirect light-dependent algicidal with an algicidal rate of 85.0%. The functional metabolism, light-trapping, light-transfer efficiency, the content of pigments, and inhibition of photosynthesis of M. aeruginosa decreased after the addition of the supernatant of the strain L1 due to oxidative stress. Moreover, 96.05% nitrate removal rate synchronized with algicidal activity was achieved with the strain L1. The relative abundance of N cycling functional genes significantly increased during the strain L1 effect on M. aeruginosa. The algicidal efficiency of the strain L1 in the raw water was 76.70% with nitrate removal efficiency of 81.4%. Overall, this study provides a novel route to apply bacterial strain with the property of denitrification coupled with algicidal activity in treating micro-polluted water bodies.

Identifying the Stripping of Oxide Debris from Graphene Oxide: Evidence from Experimental Analysis and Molecular Simulation.

In this study, characteristics of oxidation debris (OD) and its stripping mechanism from graphene oxide (GO) were explored. The results demonstrated that OD contains three components, namely, protein-, fulvic acid-, and humic acid-like substances; among these, protein-like substances with lower molecular weight and higher hydrophilicity were most liable to be stripped from GO and were the primary components stripped from GO at pH < 10, whereas humic acid- and fulvic acid-like substances were stripped from GO at pH > 10. During the stripping of OD, hydrogen bonds from carboxyl and carbonyl were the first to break, followed by hydrogen bonds from epoxy. Subsequently, π-π interactions were broken, and hydrogen bond interactions induced by hydroxyl groups were the hardest to break. After the stripping of OD, the recombination of OD on GO was observed, and regions containing relatively fewer oxygen-containing functional groups were favorable binding sites for the readsorbed OD. The stripping and recombination of OD on GO resulted in an uneven GO surface, which should be considered during the development of GO-based environmental materials and the evaluation of their environmental behavior.

Changes of characteristics and disinfection by-products formation potential of intracellular organic matter with different molecular weight in metalimnetic oxygen minimum.

Metalimnetic oxygen minimum (MOM) occurs in reservoirs or lakes due to stratification and algal blooms, which has low dissolved oxygen (DO) levels and leads to the deterioration of water quality. The transformation mechanism and the impact on the water quality of intracellular organic matter (IOM) derived from algae are poorly understood under MOM conditions. In this study, IOM extracted by Microcystis aeruginosa was divided into five components according to molecular weight (MW), and the changes of characteristics and correlated disinfection by-products formation potential (DBPFP) were analyzed and compared under MOM conditions. The removal efficiency of dissolved organic carbon (DOC) in the <5 kDa fraction (66.6%) was higher than that in the >100 kDa fraction (41.8%) after a 14-day incubation under MOM conditions. The same tendency also occurred in Fmax and DBPFP. The decrease in Fmax was mainly due to the decline in tryptophan-like and tyrosine-like for all IOM fractions. The diversity of microorganisms degrading the MW > 100 kDa fraction was lower than others. Besides low MW fractions, these findings indicated that more attention should be paid to high MW fractions which were resistant to biodegradation under MOM conditions during water treatment.

Aggregation of graphene oxide upon the stripping of oxidized debris: An experimental and molecular dynamics simulation study.

The most recent structural study of graphene oxide (GO) indicates that the oxidized debris (ODs) adhered to as-prepared GO will strip in certain aquatic settings. The impact of ODs stripping on the characteristics of GO has been widely reported, but its effects on GO aggregation have received less attention. Here, the influence of OD stripping on the GO aggregation property was identified, and the aggregation of as-prepared GO and GO upon OD stripping was compared. Upon ODs stripping, the pKa values of GO shifted from 3.91, 6.25, and 9.84 to 4.54, 6.65, and 10.21, respectively. Further analysis indicated the removal of ODs reduced the net negative charge and improved the hydrophobicity of GO, hence promoting the aggregation of GO. The acceleration of GO-Ca2+-OD aggregate formation was facilitated by the collective effects of ODs stripping, functional group deprotonation, double layer compression, OD bridging, and charge neutralization. The metal ions and stripped ODs attach to GO edges and link GO, which perform like bridges and contribute to further aggregation. In general, the existence of ODs adds complexity to the constructions and characteristics of GO, and it is important to take this into account while evaluating the aggregation characteristic of GO-based materials.

Does Negative Sampling Matter? a Review With Insights Into its Theory and Applications.

Negative sampling has swiftly risen to prominence as a focal point of research, with wide-ranging applications spanning machine learning, computer vision, natural language processing, data mining, and recommender systems. This surge in interest prompts us to question the fundamental impact of negative sampling: Does negative sampling really matter? Is there a general framework that can incorporate all negative sampling methods? In what fields is it applied? Addressing these questions, we propose a general framework that using negative sampling. Delving into the history of negative sampling, we chart its evolution across five distinct trajectories. We dissect and categorize the strategies used to select negative sample candidates, detailing global, local, mini-batch, hop, and memory-based approaches. Our comprehensive review extends to an analysis of current negative sampling methodologies, systematically grouping them into five classifications: static, hard, GAN-based, Auxiliary-based, and In-batch. Beyond detailed categorization, we explore the practical application of negative sampling across various fields. Finally, we briefly discuss open problems and future directions for negative sampling.

Different seasonal dynamics, ecological drivers, and assembly mechanisms of algae in southern and northern drinking water reservoirs.

The role of environmental factors on the community structure of algae has been intensively studied, but there are few analyses on the assembly mechanism of the algal community structure. Here, changes in the community structure of algae in different seasons, the effects of environmental variables on the algal community structure, and the assembly mechanism of the algal community structure in northern and southern reservoirs were investigated in this study. The study revealed that Bacillariophyta, Cyanophyta, and Chlorophyta were the predominant algal species in the reservoirs, with Bacillariophyta and Cyanophyta exhibiting seasonal outbreaks. Compared to the northern reservoirs, the algal diversity in the southern reservoirs was greater. The diversity and algal community structure could be significantly impacted by variations in water temperature and nitrogen level. According to the ecological model, the interaction among algal communities in reservoirs was primarily cooperation. The key taxa in the northern reservoirs was Aphanizomenon sp., while the outbreak in the southern reservoirs was Coelosphaerium sp. The community formation pattern of reservoirs was stochastic, with a higher degree of explanation observed in the southern reservoirs compared to the northern reservoirs. This study preliminarily explored the assembly mechanism of the algal community, providing a theoretical basis for the control of eutrophication in drinking water reservoirs.

The aggregation characteristics of Aspergillus spores under various conditions and the impact on LPUV inactivation: Comparisons with chlorine-based disinfection.

Aggregation is the primary step prior to fungal biofilm development. Understanding the attributes of aggregation is of great significance to better control the emergence of waterborne fungi. In this study, the aggregation of Aspergills spores (A. flavus and A. fumigatus) under various salt, culture medium, and humic acid (HA) conditions was investigated for the first time, and the inactivation via low-pressure ultraviolet (LPUV) upon aggregated Aspergillus spores was also presented. The aggregation efficiency and size of aggregates increased over time and at low salt (NaCl and CaCl2) concentration (10 mM) while decreasing with the continuous increase of salt concentration (100 and 200 mM). Increasing the concentration of culture medium and HA promoted the aggregation of fungal spores. Spores became hydrated, swelled, and secreted more viscous substances during the growth period, which accelerated the aggregation process. Results also suggested that fungal spores aggregated more easily in actual water, posing a high risk of biohazard in real-life scenarios. Inactivation efficiency by LPUV decreased with higher aggregation degrees due to the protection from the damaged spores on the outer layer and the shielding of pigments in the cell wall. Compared to chlorine-based disinfection, the aggregation resulted in the extension of shoulder length yet neglectable change of inactivation rate constant under LPUV treatment. Further investigation of cell membrane integrity and intracellular reactive oxygen species was conducted to elucidate the difference in mechanisms between various techniques. This study provides insight into the understanding and controlling of the aggregation of fungal spores.

Ecological evolution of algae in connected reservoirs under the influence of water transfer: Algal density, community structure, and assembly processes.

Reservoir connectivity provides a solution for regional water shortages. Understanding the water quality of reservoirs and the response of algal communities to water transfer could provide the basis for a long-term evolutionary model of reservoirs. In this study, a water-algal community model was established to study the effects of water transfer on water quality and algal communities in reservoirs. The results showed that water transfer significantly decreased total nitrogen and nitrate concentrations. However, the water transfer resulted in an increase in the CODMn concentration and conductivity in the receiving reservoir. Additionally, the algal density and chlorophyll-a (chl-a) concentration showed an increase with water transfer. Bacillariophyta, Cyanophyta, and Chlorophyta were the dominant algal phyllum in all three reservoirs. Water transfer induced the evolution of the algal community by driving changes in the chemical parameters of the receiving reservoir and led to more complex relationships within the algal community. The effects of stochastic processes on algal communities were also enhanced in the receiving reservoirs. These results provide specific information for water quality safety management and eutrophication prevention in connected reservoirs.

The improved resistance of germinated spores to ultraviolet irradiation: Comparison with chlorine.

Fungi outbreaks in water will include a series of processes, including spore aggregation, germination, biofilm, and finally present in a mixed state in the aquatic environment. More attention is paid to the control of dispersed fungal spores, however, there was little knowledge of the control of germinated spores. This study investigated the inactivation kinetics and mechanism of ultraviolet (UV) treatment for fungal spores with different germination percentages compared with dormant spores. The results indicated that the inactivation rate constants (k) of spores with 5%-45% germination were 0.0278-0.0299 cm2/mJ for Aspergillus niger and 0.0588-0.0647 cm2/mJ for Penicillium polonicum, which were lower than those of dormant spores. It suggested that germinated spores were more tolerant to UV irradiation than dormant spores, and it may be due to the defensive barrier (upregulated pigments) and some reductive substance (upregulated enoyl reductase) by absorbing UV or reacting with reactive oxygen species according to transcriptome analysis. Compared to dormant spores, the k-UV of germinated spores decreased by 18.17%-26.56% for Aspergillus niger, which was less than k-chlorine (62.33%-69.74%). A slighter decrease in k-UV showed UV irradiation can efficiently control fungi contamination, especially when dormant spores and germinated spores coexisted in actual water systems. This study indicates that more attention should be paid to germinated spores.

Induced crystallization for the simultaneous removal of hardness-iron-manganese in groundwater: An experimental study.

Hardness, iron, and manganese are common groundwater pollutants, that frequently surpass the established discharge standard concentrations. They can be effectively removed, however, through induced crystallization. This study has investigated the effectiveness of the simultaneous removal of hardness-iron-manganese and the crystallization kinetics of calcium carbonate during co-crystallization using an automatic potentiometric titrator. The impacts pH, dissolved oxygen (DO), and ion concentration on the removal efficiency of iron and manganese and their influence on calcium carbonate induced crystallization were assessed. The results suggest that pH exerts the most significant influence during the removal of hardness, iron, and manganese, followed by DO, and then the concentration of iron and manganese ions. The rate of calcium carbonate crystallization increased with pH, stabilizing at a maximum of 10-10 m/s. Iron and manganese can be reduced from an initial level of 4 mg/L to <0.3 mg/L and 0.1 mg/L, respectively. The removal rate of iron, however, was notably higher than that of manganese. The DO concentration correlates positively with the removal of iron and manganese but has minimal impact on the calcium carbonate crystallization process. During the removal of iron and manganese, competitive interactions occur with the substrate, as increases in the concentration of one ion will inhibit the removal rate of the other. Characterization of post-reaction particles and mechanistic analysis reveals that calcium is removed through the crystallization of CaCO3, while most iron is removed through precipitation as Fe2O3 and FeOOH. Manganese is removed via two mechanisms, crystallization of manganese oxide (MnO2/Mn2O3) and precipitation. Overall, this research studies the removal efficiency of coexisting ions, the crystallization rate of calcium carbonate, and the mechanism of simultaneous removal, and provides valuable data to aid in the development of new removal techniques for coexisting ions.

Aerobic Denitrification Promoting by Actinomycetes Coculture: Investigating Performance, Carbon Source Metabolic Characteristic, and Raw Water Restoration.

The coculture theory that promotes denitrification relies on effectively utilizing the resources of low-efficiency denitrification microbes. Here, the strains Streptomyces sp. PYX97 and Streptomyces sp. TSJ96 were isolated and showed lower denitrification capacity when cultured individually. However, the coculture of strains PYX97 and TSJ96 enhanced nitrogen removal (removed 96.40% of total nitrogen) and organic carbon reduction (removed 92.13% of dissolved organic carbon) under aerobic conditions. Nitrogen balance analysis indicated that coculturing enhanced the efficiency of nitrate converted into gaseous nitrogen reaching 70.42%. Meanwhile, the coculturing promoted the cell metabolism capacity and carbon source metabolic activity. The coculture strains PYX97 and TSJ96 thrived in conditions of C/N = 10, alkalescence, and 150 rpm shaking speed. The coculturing reduced total nitrogen and CODMn in the raw water treatment by 83.32 and 84.21%, respectively. During this treatment, the cell metabolic activity and cell density increased in the coculture strains PYX97 and TSJ96 reactor. Moreover, the coculture strains could utilize aromatic protein and soluble microbial products during aerobic denitrification processes in raw water treatment. This study suggests that coculturing inefficient actinomycete strains could be a promising approach for treating polluted water bodies.

Spatio-temporal dynamics of phytoplankton in a diversion reservoir and the major influencing factors: taxonomic versus functional groups classification.

Identifying factors affecting phytoplankton dynamics is crucial to the management of aquatic ecosystems. A lot of scholars have conducted intensive studies on phytoplankton in lake or reservoirs, but not many studies have been conducted on diversion reservoirs. To explore the seasonal and spatial variation of phytoplankton communities and their relationship with environmental factors in the context of water diversion, a case study was carried out at XiKeng (XK) reservoir in South China. In this study, month-by-month water samples and phytoplankton were collected from this reservoir from December, 2021, to July, 2022. The results showed that the phytoplankton community was characterized by significant spatial and temporal variations. There were significant differences in phytoplankton abundance and structure in the reservoirs in terms of time. The abundance of phytoplankton cells and the proportion of Cyanobacteria in the reservoir showed a trend of increasing from autumn to spring and then decreasing from spring to summer, while the functional group evolved from S1 in autumn to SN in spring and summer. The abundance of phytoplankton was influenced by the dynamic water division and the characteristics of the reservoir itself, resulting in a spatial distribution characteristic of AIII > AII > AI. Water temperature (WT) and nutrients were the key factors driving the changes in phytoplankton abundance and community structure in the reservoir. These findings will deepen our understanding of the spatial and temporal dynamics of phytoplankton community structure in diversion reservoirs and provide a basis for freshwater water ecological management strategies.

Effect of microplastics on the adherence of coexisting background organic contaminants to natural organic matter in water.

Microplastics (MPs) may interact with background organic substances (including natural organic matter and organic pollutants) after entering the aquatic environment and affect their original binding. Thus, the interaction of MPs with background organic substances (i.e., humic acid (HA), polychlorinated biphenyls (PCBs), and hydroxy PCBs) were elucidated. According to the results, PCB and hydroxy PCB displayed a strong propensity to adhere to HAs in the absence of MPs. However, the PCBs and hydroxy PCBs that were initially bound to HAs shifted from HAs to MPs in the presence of MPs. Further analysis demonstrated that this transfer was dominated by van der Waals interactions, with hydrogen bond interactions as an additional driving force. Upon the interaction, large MPs-HA-PCB/ hydroxy PCB aggregates with MPs as the core and HAs as the outermost layer were formed. Significant changes in the properties of background organic matter, including the distribution of PCB/hydroxy PCB around HA, diffusion coefficient, and hydrogen bond networks in the HA-PCB/ hydroxy PCB domains, occurred during the MP-HA-PCB/hydroxy PCB interaction. These results provide molecular-level evidence that the intrusion of MPs changes the binding preference of background organic pollutants and can lead to a redistribution of background organic pollutants.

Activation of indigenous denitrifying bacteria and enhanced nitrogen removal via artificial mixing in a drinking water reservoir: Insights into gene abundance, community structure, and co-existence model.

Nitrogen pollution poses a severe threat to aquatic ecosystems and human health. This study investigated the use of water lifting aerators for in situ nitrogen reduction in a drinking water reservoir. The reservoir was thoroughly mixed and oxygenated after using water-lifting aerators for 42 days. The average total nitrogen concentration, nitrate nitrogen, and ammonium nitrogen-in all water layers-decreased significantly (P < 0.01), with a reduction efficiency of 35 ± 3%, 34 ± 2%, and 70 ± 6%, respectively. Other pollutants, including organic matter, phosphorus, iron, and manganese, were also effectively removed. Quantitative polymerase chain reactions indicated that bacterial nirS gene abundance was enhanced 26.34-fold. High-throughput sequencing, phylogenetic tree, and network analysis suggested that core indigenous nirS-type denitrifying bacteria, such as Dechloromonas, Simplicispira, Thauera, and Azospira, played vital roles in nitrogen and other pollutant removal processes. Furthermore, structural equation modeling revealed that nitrogen removal responded positively to WT, DO, and nirS gene abundance. Our findings provide a promising strategy for nitrogen removal in oligotrophic drinking water reservoirs with carbon deficiencies.

Enhanced nitrogen removal of micropolluted source waterbodies using an iron activated carbon system with siliceous materials: Insights into metabolic activity, biodiversity, interactions of core genus and co-existence.

Aerobic denitrification technology can effectively abate the nitrogen pollution of water source reservoirs. In this study, 40% siliceous material was used as the carrier to replace the activated carbon in Fe/C material to enhance denitrification and purify water. The removal efficiency of new material for target pollutants were nitrate nitrogen (95.68%), total phosphorus (68.23%) and chemical oxygen demand (46.20%). Aerobic denitrification of water samples and anaerobic denitrification of sediments in three systems jointly assisted nitrogen removal. In a reactor with new material, diversity and richness of denitrifying bacterial communities were enhanced, and the symbiotic structure of aerobic denitrifying bacteria was more complex (Bacillus and Mycobacteria as the dominant bacteria); the microbial distribution better matched the Zif and Mandelbrot models. This system significantly increased the abundance of key enzymes in water samples. The new material effectively removed pollutants and represents a promising and innovative in-situ remediation method for reservoirs.