Response of anammox consortia to inhibition from high ferroferric oxide nanoparticles concentration and potential recovery mechanism.

The substantial discharge of ferroferric oxide nanoparticles (Fe3O4 NPs) into sewage threatens the survival of functional microorganisms in wastewater treatment. This study elucidated responses of anaerobic ammonium oxidation (anammox) consortia to inhibition from high Fe3O4 NPs concentration and recovery mechanisms. The nitrogen removal efficiency decreased by 20.3 % and recovered after 55 days under 1000 mg/L Fe3O4 NPs concentration. Toxicity was attributed to reactive oxygen species (ROS) production. The excessive ROS damaged membrane integrity, nitrogen metabolism, and DNA synthesis, resulting in the inhibition of anammox bacteria activity. However, recovery mechanisms of anammox consortia activity were activated in response to 1000 mg/L Fe3O4 NPs. The increase of heme oxygenase-1, thioredoxin, and nicotinamide adenine dinucleotide-quinone oxidoreductase genes alleviated oxidative stress. Furthermore, the activation of metabolic processes associated with membrane and DNA repair promoted recovery of anammox bacteria activity. This study provided new insights into NPs contamination and control strategies during anammox process.

Achieving high nitrogen and antibiotics removal efficiency by nZVI-C in partial nitritation/anammox system with a single-stage membrane-aerated biofilm reactor.

This study innovated constructed an activated carbon-loaded nano-zero-valent iron (nZVI-C) enhanced membrane aerated biofilm reactor (MABR) coupled partial nitritation/anammox (PN/A) system for optimizing nitrogen and antibiotics removal. Results showed that nitrogen and antibiotic removal efficiencies of 88.45 ± 0.14% and 89.90 ± 3.07% were obtained by nZVI-C, respectively. nZVI-C hastened Nitrosomonas enrichment (relative abundance raised from 2.85% to 12.28%) by increasing tryptophan content in EPS. Furthermore, nZVI-C proliferated amo gene by 3.92 times and directly generated electrons, stimulating Ammonia monooxygenase (AMO) co-metabolism activity. Concurrently, via antibiotic resistance genes (ARGs) horizontal transfer, Nitrosomonas synergized with Arenimonas and Comamonadaceae for efficient antibiotic removal. Moreover, nZVI-C mitigated antibiotics inhibition of electron transfer by proliferating genes for PN and anammox electron production (hao, hdh) and utilization (amo, hzs, nir). That facilitated electron transfer and synergistic substrate conversion between ammonia oxidizing bacteria (AOB) and anaerobic ammonia oxidizing bacteria (AnAOB). Finally, the high nitrogen removal efficiency of the MABR-PN/A system was achieved.

Synergistic Integration of Anammox and Endogenous Denitrification Processes for the Simultaneous Carbon, Nitrogen, and Phosphorus Removal.

The feasibility of a synergistic endogenous partial denitrification-phosphorus removal coupled anammox (SEPD-PR/A) system was investigated in a modified anaerobic baffled reactor (mABR) for synchronous carbon, nitrogen, and phosphorus removal. The mABR comprising four identical compartments (i.e., C1-C4) was inoculated with precultured denitrifying glycogen-accumulating organisms (DGAOs), denitrifying polyphosphate-accumulating organisms, and anammox bacteria. After 136 days of operation, the chemical oxygen demand (COD), total nitrogen, and phosphorus removal efficiencies reached 88.6 ± 1.0, 97.2 ± 1.5, and 89.1 ± 4.2%, respectively. Network-based analysis revealed that the biofilmed community demonstrated stable nutrient removal performance under oligotrophic conditions in C4. The metagenome-assembled genomes (MAGs) such as MAG106, MAG127, MAG52, and MAG37 annotated as denitrifying phosphorus-accumulating organisms (DPAOs) and MAG146 as a DGAO were dominated in C1 and C2 and contributed to 89.2% of COD consumption. MAG54 and MAG16 annotated as Candidatus_Brocadia (total relative abundance of 16.5% in C3 and 4.3% in C4) were responsible for 74.4% of the total nitrogen removal through the anammox-mediated pathway. Functional gene analysis based on metagenomic sequencing confirmed that different compartments of the mABR were capable of performing distinct functions with specific advantageous microbial groups, facilitating targeted nutrient removal. Additionally, under oligotrophic conditions, the activity of the anammox bacteria-related genes of hzs was higher compared to that of hdh. Thus, an innovative method for the treatment of low-strength municipal and nitrate-containing wastewaters without aeration was presented, mediated by an anammox process with less land area and excellent quality effluent.

Journey of the swift nitrogen transformation: Unveiling comammox from discovery to deep understanding.

COMplete AMMonia OXidizer (comammox) refers to microorganisms that have the function of oxidizing NH4+ to NO3- alone. The discovery of comammox overturned the two-step theory of nitrification in the past century and triggered many important scientific questions about the nitrogen cycle in nature. This comprehensive review delves into the origin and discovery of comammox, providing a detailed account of its detection primers, clades metabolic variations, and environmental factors. An in-depth analysis of the ecological niche differentiation among ammonia oxidizers was also discussed. The intricate role of comammox in anammox systems and the relationship between comammox and nitrogen compound emissions are also discussed. Finally, the relationship between comammox and anammox is displayed, and the future research direction of comammox is prospected. This review reveals the metabolic characteristics and distribution patterns of comammox in ecosystems, providing new perspectives for understanding nitrogen cycling and microbial ecology. Additionally, it offers insights into the potential application value and prospects of comammox.

Leveraging Bayesian network to reveal the importance of water level in a shallow lake ecosystem: A study based on Paleo-diatom and fish community.

Lake ecological processes and nutrient patterns are increasingly affected by water level variation around the world. Still, the long-term effects of water level change on lake ecosystems and their implications for suitable lake level management have rarely been studied. Here, we studied the ecosystem dynamics of a mesotrophic lake located in the cold and arid region of northern China based on long-term paleo-diatom and fishery records. Utilizing a novel Copula-Bayesian Network model, possible hydrological-driven ecosystem evolution was discussed. Results show that increased nutrient concentration caused by the first water level drop in the early 1980s incurred a transition of sedimental diatoms towards pollution-resistant species, and the following water level rise in the mid-1980s brought about considerable external loading, which attributed to eutrophication and caused the miniaturization of fishery structure. In the 21st century, a continuous water level plummet further reduced the sediment diatom biomass and the fish biomass by altering nutrient concentration. However, with the implementation of the water diversion project in 2011, oligotrophic species increased, and the ecosystem developed for the better. From the perspective of water quality protection requirements and the ecological well-being of Lake Hulun, the appropriate water level should be around 542.42-544.15 m. In summary, our study highlights the coupling effect of water level and water quality on Lake Hulun ecosystem and gives shed to lake water level operation and management under future climate change and human activities.

Seasonal and distance-decay patterns of surface sediments microbial nitrogen and sulfur cycling linkage in the eastern coast of China.

The surface sediments as a repository of pelagic environment changes and microbial community structural succession tend to have a profound effect on global and local nitrogen and sulfur cycling. In this study, analysis of sediment samples collected from the Bohai Sea, Yellow Sea, and north of the East China Seas (BYnECS) revealed longitude, latitude, depth, and chlorophyll had the strongest influence on microbial community structure (p-values < 0.005). A clear distance-decay pattern was exhibited in BYnECS. The result of co-occurrence network modularization implied that the more active pathway in winter was thiosulfate reduction and nitrate reduction, while in summer it was nitrification. The potential functional genes were predicted in microbial communities, and the most dominant genes were assigned to assimilatory sulfur reduction, denitrification, and dissimilatory nitrate reduction. This study innovatively explored the potential relationships between nitrogen and sulfur cycling genes of these three sea regions in the China Sea.

Review on sterilization techniques, and the application potential of phage lyase and lyase immobilization in fighting drug-resistant bacteria.

Many human health problems and property losses caused by pathogenic contamination cannot be underestimated. Bactericidal techniques have been extensively studied to address this issue of public health and economy. Bacterial resistance develops as a result of the extensive use of single or multiple but persistent usage of sterilizing drugs, and the emergence of super-resistant bacteria brings new challenges. Therefore, it is crucial to control pathogen contamination by applying innovative and effective sterilization techniques. As organisms that exist in nature and can specifically kill bacteria, phages have become the focus as an alternative to antibacterial agents. Furthermore, phage-encoded lyases are proteins that play important roles in phage sterilization. The in vitro sterilization of phage lyase has been developed as a novel biosterilization technique to reduce bacterial resistance and is more environmentally friendly than conventional sterilization treatments. For the shortcomings of enzyme applications, this review discusses the enzyme immobilization methods and the application potential of immobilized lyases for sterilization. Although some techniques provide effective solutions, immobilized lyase sterilization technology has been proven to be a more effective innovation for efficient pathogen killing and reducing bacterial resistance. We hope that this review can provide new insights for the development of sterilization techniques.

Efficient photocatalytic reduction of nitrate byproducts during anammox process by novel extracellular polymeric substances-embedded NH2-MIL-101(Fe) photocatalysts.

Anaerobic ammonium oxidation (anammox) is an efficient nitrogen removal process; however, nitrate byproducts hampered its development. In this study, extracellular polymeric substances (EPS) were embedded into NH2-MIL-101(Fe), creating NH2-MIL-101(Fe)@EPS to reduce nitrate. Results revealed that chemical nitrate reduction efficiency of NH2-MIL-101(Fe)@EPS surpassed that of NH2-MIL-101(Fe) by 17.3 %. After adding 0.5 g/L NH2-MIL-101(Fe)@EPS within the anammox process, nitrate removal efficiency reached63.9 %, consequently elevating the total nitrogen removal efficiency to 92.4 %. 16S rRNA sequencing results elucidated the predominant role of Candidatus Brocadia within NH2-MIL-101(Fe)@EPS-anammox system. Concurrently, sufficient photogenerated electrons were transferred to microorganisms, promoting the growth of Desnitratisoma and OLB17. Additionally, photogenerated electrons activated flavin and Complex III, thereby up-regulating crucial genes involved in intra/extracellular electron transfer. Subsequently, denitrification and dissimilatory nitrate reduction to ammonium were activated to reduce nitrate. In summary, this study achieved a notable rate of photocatalytic nitrate reduction within anammox process through the NH2-MIL-101(Fe)@EPS photocatalysts.

Accumulation of Ag(0) Single Atoms at Water/Mineral Interfaces during Sunlight-Induced Reduction of Ionic Ag by Phenolic DOM.

Silver (Ag) undergoes a complex and dynamic Ag+/Ag0 cycle under environmental conditions. The Ag+ → Ag nanoparticles (AgNPs) transformation due to the combined actions of sunlight, O2, and dissolved organic matter has been a well-known environmental phenomenon. In this study, we indicate that this process may be accompanied by a pronounced accumulation of Ag(0) single atoms (Ag-SAs) on the minerals' surfaces. According to spherical aberration-corrected scanning transmission electron microscopy and high-energy-resolution X-ray adsorption fine structure analyses, humic acid (HA) and phenol (PhOH) can induce Ag-SAs accumulation, whereas oxalic acid causes only AgNPs deposition. Ag-SAs account for more than 20 wt % of total Ag(0) on the γ-Al2O3 surfaces during HA- and PhOH-mediated photolysis processes. HA also causes Ag-SAs to accumulate on two other prevalent soil minerals, SiO2 and Fe2O3, and the fractions of Ag-SAs are about 15 wt %. Our mechanism studies suggest that a phenolic molecule acts as a reducing agent of Ag+ and a stabilizer of Ag-SAs, protecting Ag-SAs against autocatalytic nucleation.

Multi-omics analysis revealed the selective enrichment of partial denitrifying bacteria for the stable coupling of partial-denitrification and anammox process under the influence of low strength magnetic field.

The microbial consortium involving anaerobic ammonium oxidation (anammox) and partial denitrification (PD), known as PD-anammox, is an emerging energy-efficient and lower carbon nitrogen removal process from wastewater. However, maintaining a stable PD process by locking nitrate reduction until nitrite was challenging. This study established the first stable connection of anammox with constant nitrite generation by PD bacteria under a low-strength (1.3 mT) magnetic field (MF). When the nitrogen loading rate was 1.81 kg-N/m3/d, the nitrogen removal efficiency of the control reactor (R1) was 75%, lower than that of the experimental reactor (R2), which was 85%. The expression of Thauera and Zoogloea, potential PD bacteria was substantially lower in R1 (5.75% and 1.21%, respectively) than in R2 (10.25 and 6.61%, respectively), according to a meta-transcriptomic analysis. At the same time, the mRNA expression of anammox genera Candidatus Brocadia and Candidatus Kuenenia was 33.53% and 3.83% in R1 and 22.86% and 1.87% in R2. Moreover, carbon and nitrogen metabolism pathways were more abundant under the influence of low-strength MF. The selective enrichment of PD bacteria can be attributed to the increased expression of carbon metabolic pathways like the citrate cycle, glycolysis/gluconeogenesis, and pyruvate metabolism. Interestingly, the control reactor was dominated by a hydroxylamine-dependent anammox process while a low-strength MF-enhanced nitric-oxide-dependent anammox process. For successful anammox-centered nitrogen removal from wastewater, this study demonstrated that low-strength MF is a convenient and applicable technique to lock the nitrate reduction until nitrite.

Combination of partial nitrification and microbial fuel cell for simultaneous ammonia reduction, organic removal, and energy recovery.

The chemical oxygen demand (COD) in municipal wastewater has become an obstacle for anammox in mainstream applications. In this study, the single chamber microbial fuel cell (MFC) was installed as an influent device for a partial nitrification-sequencing batch reactor (PN-SBR) to realize integrating COD removal and partial nitrification. After 80 days of operation, the nitrite accumulation rate reached 93%, while the COD removal efficiency was 56%. The output voltage and the power density of MFC were 66.62 mV and 2.40 W/m3, respectively. The content of EPS, especially polysaccharides in the stable phase, has increased compared with the seed sludge. The most dominant genus in MFC anode biofilm and SBR granular sludge was Thauera, which has organic compounds degradation capacity and could degrade nitrate. This study revealed the microbial interaction between MFC and partial nitrification and provided a new strategy for stable ammonia and nitrite supply for mainstream anammox plants.

A Bioinspired Atomically Thin Nanodot Supported Single-Atom Nanozyme for Antibacterial Textile Coating.

Surface antibacterial coatings with outstanding antibacterial efficiency have attracted increasing attention in medical protective clothing and cotton surgical clothing. Although nanozymes, as a new generation of antibiotics, are used to combat bacteria, their catalytic performance remains far from satisfactory as alternatives to natural enzymes. Single-atom nanodots provide a solution to the low catalytic activity bottleneck of nanozymes. Here, atomically thin C3 N4 nanodots supported single Cu atom nanozymes (Cu-CNNDs) are developed by a self-tailoring approach, which exhibits catalytic efficiency of 8.09 × 105 M-1 s-1 , similar to that of natural enzyme. Experimental and theoretical calculations show that excellent peroxidase-like activity stems from the size effect of carrier optimizing the coordination structure, leading to full exposure of Cu-N3 active site, which improves the ability of H2 O2 to generate hydroxyl radicals (•OH). Notably, Cu-CNNDs exhibit over 99% superior antibacterial efficacy and are successfully grafted onto cotton fabrics. Thus, Cu-CNNDs blaze an avenue for exquisite biomimetic nanozyme design and have great potential applications in antibacterial textiles.

Synergistic action of phages and lytic proteins with antibiotics: a combination strategy to target bacteria and biofilms.

BACKGROUND: Multidrug-resistant bacteria continue to emerge owing to the abuse of antibiotics and have a considerable negative impact on people and the environment. Bacteria can easily form biofilms to improve their survival, which reduces the efficacy of antibacterial drugs. Proteins such as endolysins and holins have been shown to have good antibacterial activity and effectively removal bacterial biofilms and reduce the production of drug-resistant bacteria. Recently, phages and their encoded lytic proteins have attracted attention as potential alternative antimicrobial agents. The aim of the present study was to investigate the sterilising efficacy of phages (SSE1, SGF2, and SGF3) and their encoded lytic proteins (lysozyme and holin), and to further explore their potential in combination with antibiotics. To the ultimate aim is to reduce or replace the use of antibiotics and provide more materials and options for sterilisation. RESULTS: Phages and their encoded lytic proteins were confirmed to have great advantages in sterilisation, and all exhibited significant potential for reducing bacterial resistance. Previous studies on the host spectrum demonstrated the bactericidal efficacy of three Shigella phages (SSE1, SGF2, and SGF3) and two lytic proteins (LysSSE1 and HolSSE1). In this study, we investigated the bactericidal effects on planktonic bacteria and bacterial biofilms. A combined sterilisation application of antibiotics, phages, and lytic proteins was performed. The results showed that phages and lytic proteins had better sterilisation effects than antibiotics with 1/2 minimum inhibitory concentrations (MIC) and their effect was further improved when used together with antibiotics. The best synergy was shown when combined with ß- lactam antibiotics, which might be related to their mechanism of sterilising action. This approach ensures a bactericidal effect at low antibiotic concentrations. CONCLUSIONS: This study strengthens the idea that phages and lytic proteins can significantly sterilise bacteria in vitro and achieve synergistic sterilisation effects with specific antibiotics. Therefore, a suitable combination strategy may decrease the risk of drug resistance.

Energy-efficient and carbon neutral anammox-based nitrogen removal by coupling with nitrate reduction pathways: A review.

Sustainable development goal 6 emphasizes the efficient management of water resources, wastewater treatment, and reuse of treated wastewater. Removing nitrogen from wastewater was an economically expensive and energy-consuming wastewater treatment process. The discovery of anammox changes the paradigm of wastewater treatment. Nevertheless, coupling anammox with partial nitrification (PN-anammox) has been an immensely rewarding and scientifically supported side-stream wastewater treatment process. However, the PN-anammox process is inherited with severe issues of higher effluent nitrate and lower nitrogen removal efficiency at a lower temperature. Thus, it is evident that PN-anammox cannot meet the desired target without the involvement of others nitrogen cycle bacteria. The nitrate reduction pathways such as denitrifying anaerobic methane-oxidizing (DAMO) microbes, partial denitrification (PD), and dissimilatory nitrate reduction to ammonium (DNRA) seem the best alternative to reduce nitrate into nitrite or ammonium for anammox supplement. From the perspective of the environment, the coupling of anammox with PD, DAMO, and DNRA alleviates the use of organic matter, decreases greenhouse gas release, and reduces energy consumption. This review comprehensively discussed the importance and application perspective of anammox with diverse nitrate-reducing bacteria. Furthermore, research is still needed about DAMO-anammox and DNRA-anammox to achieve higher nitrogen removal efficiency. Future research should incorporate emerging pollutants removal in the anammox coupling process. This review will provide deep insight into the design of energy-efficient and carbon-neutral nitrogen removal from wastewater.

Abrading-Induced Breakdown of Ag Nanoparticles into Atomically Dispersed Ag for Enhancing Antimicrobial Performance.

Silver is among the most essential antimicrobial agents. Increasing the efficacy of silver-based antimicrobial materials will reduce operating costs. Herein, we show that mechanical abrading causes atomization of Ag nanoparticles (AgNPs) into atomically dispersed Ag (AgSAs) on the surfaces of an oxide-mineral support, which eventually boosts the antibacterial efficacy considerably. This approach is straightforward, scalable, and applicable to a wide range of oxide-mineral supports; additionally, it does not require any chemical additives and operates under ambient conditions. The obtained AgSAs-loaded γ-Al2O3 inactivated Escherichia coli (E. coli) five times as fast as the original AgNPs-loaded γ-Al2O3. It can be utilized over 10 runs with minimal efficiency loss. The structural characterizations indicate that AgSAs exhibit a nominal charge of 0 and are anchored at the doubly bridging OH on the γ-Al2O3 surfaces. Mechanism studies demonstrate that AgSAs, like AgNPs, damage bacterial cell wall integrity, but they release Ag+ and superoxide substantially faster. This work not only provides a simple method for manufacturing AgSAs-based materials but also shows that AgSAs have better antibacterial properties than the AgNPs counterpart.

Integrative effects of microbial inoculation and amendments on improved crop safety in industrial soils co-contaminated with organic and inorganic pollutants.

Soils co-contaminated by organic and inorganic pollutants usually pose major ecological risks to soil ecosystems including plants. Thus, effective strategies are needed to alleviate the phytotoxicity caused by such co-contamination. In this study, microbial agents (a mixture of Bacillus subtilis, Sphingobacterium multivorum, and a commercial microbial product named OBT) and soil amendments (ß-cyclodextrin, rice husk, biochar, calcium magnesium phosphate fertilizer, and organic fertilizer) were evaluated to determine their applicability in alleviating toxicity to crops (maize and soybean) posed by polycyclic aromatic hydrocarbon (PAHs) and potentially toxic metals co-contaminated soils. The results showed that peroxidase, catalase, and superoxide dismutase activity levels in maize or soybean grown in severely or mildly contaminated soils were significantly enhanced by the integrative effects of amendments and microbial agents, compared with those in single plant treatments. The removal rates of Zn, Pb, and Cd in severely contaminated soils were 49 %, 47 %, and 51 % and 46 %, 45 %, and 48 %, for soybean and maize, respectively. The total contents of Cd, Pb, Zn, and PAHs in soil decreased by day 90. Soil organic matter content, levels of nutrient elements, and enzyme activity (catalase, urease, and dehydrogenase) increased after the amendments and application of microbial agents. Moreover, the amendments and microbial agents also increased the diversity and distribution of bacterial species in the soil. These results suggest that the amendments and microbial agents were beneficial for pollutant purification, improving the soil environment and enhancing both plant resistance to pollutants and immune systems of plants.

Extensive data analysis and kinetic modelling of dosage and temperature dependent role of graphene oxides on anammox.

Anaerobic ammonium oxidation (anammox) is carbon friendly biological nitrogen removal process, and recently more focus is given to improving the anammox activity. Because of its high adsorption and modifiability, graphene and its derivative in wastewater treatment have received much attention. However, the specific effects and mechanisms of graphene oxide (GO) and reduced graphene oxide (RGO) on anammox are still controversial. Extensive data analysis was performed to explore the effects of GO and RGO on anammox. Statistical analysis revealed that 100 mg/L GO significantly promoted the anammox process, while 200 mg/L of GO inhibited the anammox process. The promotion of anammox performance under the influence of RGO was dependent on the temperature. The Logistic model was utilized for depicting the variation of nitrogen removal efficiency under promoting dosage of graphene oxides. A neural network model-based analysis was performed to reach anammox's potential mechanisms under the influence of two graphene oxides. Spearman correlation analysis showed that GO and RGO had significant positive correlations with nitrogen removal efficiency and specific anammox activity (p < 0.01), especially for RGO. In addition, the abundance of Planctomycetes and Nitrospirae was positively correlated with the addition of graphene oxides. This work comprehensively unraveled the role of graphene oxide materials on the anammox process and provided practical directions for the enhancement of anammox.

Insight into impact of sewage discharge on microbial dynamics and pathogenicity in river ecosystem.

Direct sewage discharge could cause copious numbers of serious and irreversible harm to the environment. This study investigated the impacts of treated and raw sewage on the river ecosystem. Through our analysis, sewage carried various nutrients into the river, leading to changes in the microbial community in the river and reducing the diversity and richness of bacteria. The relative abundances of Hydrogenophaga, Thauera, Planctomyces, Zoogloea, and Pseudomonas boosted from 0.25, 0.01, 0.00, 0.05, and 0.08% to 3.33, 3.43, 0.02, 6.28, and 2.69%, before and after raw sewage discharge, respectively. The gene abundance of pathogenic bacteria significantly increased after raw sewage discharge. For instance, the gene abundance of Vibrio, Helicobacter, Tuberculosis, and Staphylococcus augmented from 4055, 3797, 13,545, 33 reads at Site-1 to 23,556, 13,163, 19,887, 734 reads at Site-2, respectively. In addition, according to the redundancy analysis (RDA), the infectious pathogens were positively related to the environmental parameters, in which COD showed the highest positive correlation with Mycobacterium tuberculosis. Additionally, river self-purification may contribute to improving water quality and reducing pathogenicity. The outcomes of this study showed that direct discharge brought pathogens and changed microbial community structure of the river.

Comparison of Different Carriers to Maintain a Stable Partial Nitrification Process for Low-Strength Wastewater Treatment.

Practical application of the partial nitritation-anaerobic ammonium oxidation (anammox) process has attracted increasing attention because of its low operational costs. However, the nitritation process, as a promising way to supply nitrite for anammox, is sensitive to the variations in substrate concentration and dissolved oxygen (DO) concentration. Therefore, a stable supply of nitrite becomes a real bottleneck in partial nitritation-anammox process, limiting their potential for application in mainstream wastewater treatment. In this study, five 18-L sequencing batch reactors were operated in parallel at room temperature (22°C ± 4°C) to explore the nitritation performance with different carrier materials, including sepiolite-nonwoven carrier (R1), zeolite-nonwoven carrier (R2), brucite-nonwoven carrier (R3), polyurethane carrier (R4), and nonwoven carrier (R5). The ammonia oxidation rate (AOR) in R1 reached the highest level of 0.174 g-N L-1 d-1 in phase II, which was 1.4-fold higher than the control reactor (R4). To guarantee a stable supply of nitrite for anammox process, the nitrite accumulation efficiency (NAE) was always higher than 77%, even though the free ammonia (FA) decreases to 0.08 mg-N/L, and the pH decreases to 6.8 ± 0.3. In phase V, the AOR in R1 reached 0.206 g-N L-1 d-1 after the DO content increase from 0.7 ± 0.3 mg/L to 1.7 ± 0.3 mg/L. The NAE in R1 was consistently higher than 68.6%, which was much higher than the other reactor systems (R2: 43.8%, R3: 46.6%, R4: 23.7%, R5: 22.7%). Analysis of 16S rRNA gene sequencing revealed that the relative abundance of Nitrobacter and Nitrospira in R1 was significantly lower than other reactors, indicating that the sepiolite carrier plays an important role in the inhibition of nitrite-oxidizing bacteria. These results indicate that the sepiolite nonwoven composite carrier can effectively improve the nitritation process, which is highly beneficial for the application of partial nitritation-anammox for mainstream wastewater treatment.

Partition of Anammox and Nitrifiers Through Bio-Carriers for Full-Scale Sidestream Partial Nitrification-Anammox Plant.

This study assessed the activity and community structure in different types of sludge to reveal the partition mechanism of anammox and nitrifiers in a full-scale partial nitrification-anammox plant. Batch experiments confirmed that suspended sludge had higher partial nitrification capacity, and biofilm sludge had higher anammox activity, 16.9 times higher than suspended sludge. qPCR analysis confirmed that the amoA gene was mainly present in suspended sludge, and the highest abundance of the Amx gene was observed in biofilm sludge, reaching 1.01 × 107 copies/ng DNA. High-throughput results revealed that Nitrosomonas was the main ammonia-oxidizing bacteria with high activity in suspended sludge, and Candidatus Brocadia had the highest abundance of 13.4% in biofilm sludge. This is the exploration of the microbial community of three different sludge types in the full-scale sidestream PN/A system for the first time, which can guide the construction and replication of full-scale PN/A plants.