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Keywords = nitrite oxidation rate

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13 pages, 1594 KiB  
Article
Unraveling Nitrogen Removal and Microbial Response of Integrated Sulfur-Driven Partial Denitrification and Anammox Process in Saline Wastewater Treatment
by Xiangchen Li, Jie Sun, Zonglun Cao, Junxi Lai, Haodi Feng and Minwen Guo
Water 2025, 17(15), 2284; https://doi.org/10.3390/w17152284 - 31 Jul 2025
Viewed by 255
Abstract
Increasing the discharge of saline wastewater from an industrial field poses a challenge for applicable Anammox-based technologies. This study established the integrated partial sulfur-driven denitrification and Anammox (SPDA) system to explore the effects of different salinity levels on nitrogen conversion features. The results [...] Read more.
Increasing the discharge of saline wastewater from an industrial field poses a challenge for applicable Anammox-based technologies. This study established the integrated partial sulfur-driven denitrification and Anammox (SPDA) system to explore the effects of different salinity levels on nitrogen conversion features. The results of batch tests suggested that sulfur-driven denitrification exhibited progressive suppression of nitrate reduction (97.7% → 12.3% efficiency at 0% → 4% salinity) and significant nitrite accumulation (56.4% accumulation rate at 2% salinity). Anammox showed higher salinity tolerance but still experienced drastic TN removal decline (97.6% → 17.3% at 0% → 4% salinity). Long-term operation demonstrated that the SPDA process could be rapidly established at 0% salinity and stabilize with TN removal efficiencies of 98.1% (1% salinity), 72.8% (2% salinity), and 70.2% (4% salinity). The robustness of the system was attributed to the appropriate strategy of gradual salinity elevation, the promoted secretion of protein-dominated EPS, the salinity-responsive enrichment of Sulfurimonas (replacing Thiobacillus and Ferritrophicum) as sulfur-oxidizing bacteria (SOB), and the sustained retention and activity of Brocadia as AnAOB. The findings in this study deepen the understanding of the inhibitory effects of salinity on the SPDA system, providing a feasible solution for saline wastewater treatment with low cost and high efficiency. Full article
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13 pages, 2474 KiB  
Article
Renal Effects and Nitric Oxide Response Induced by Bothrops atrox Snake Venom in an Isolated Perfused Kidney Model
by Terentia Batista Sa Norões, Antonio Rafael Coelho Jorge, Helena Serra Azul Monteiro, Ricardo Parente Garcia Vieira and Breno De Sá Barreto Macêdo
Toxins 2025, 17(8), 363; https://doi.org/10.3390/toxins17080363 - 24 Jul 2025
Viewed by 277
Abstract
The snakes from the genus Bothrops are responsible for most of the ophidic accidents in Brazil, and Bothrops atrox represents one of these species. Envenomation by these snakes results in systemic effects and is often associated with early mortality following snakebite incidents. The [...] Read more.
The snakes from the genus Bothrops are responsible for most of the ophidic accidents in Brazil, and Bothrops atrox represents one of these species. Envenomation by these snakes results in systemic effects and is often associated with early mortality following snakebite incidents. The present study investigates the pharmacological properties of Bothrops atrox venom (VBA), focusing specifically on its impact on renal blood flow. Following the renal perfusion procedure, kidney tissues were processed for histopathological examination. Statistical analysis of all evaluated parameters was conducted using ANOVA and Student’s t-test, with significance set at p < 0.005. Administration of VBA resulted in a marked reduction in both perfusion pressure and renal vascular resistance. In contrast, there was a significant elevation in urinary output and glomerular filtration rate. Histological changes observed in the perfused kidneys were mild. The involvement of nitric oxide in the pressor effects of Bothrops atrox venom was not investigated in renal perfusion systems or in in vivo models. Treatment with VBA led to elevated nitrite levels in the bloodstream of the experimental animals. This effect was completely inhibited following pharmacological blockade with L-NAME. Based on these findings, we conclude that VBA alters renal function and promotes increased nitric oxide production. Full article
(This article belongs to the Special Issue Clinical Evidence for Therapeutic Effects and Safety of Animal Venoms)
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19 pages, 1851 KiB  
Article
Industrial-Scale Wastewater Nano-Aeration and -Oxygenation and Dissolved Air Flotation: Electric Field Nanobubble and Machine Learning Approaches to Enhanced Nano-Aeration and Flotation
by Niall J. English
Environments 2025, 12(7), 228; https://doi.org/10.3390/environments12070228 - 5 Jul 2025
Viewed by 648
Abstract
Substantial boosts in the low-energy nano-oxygenation of incoming process water were achieved at a municipal wastewater treatment plant (WWTP) upstream of activated sludge (AS) aeration lanes on a single-pass basis by means of an electric field nanobubble (NB) generation method (with unit residence [...] Read more.
Substantial boosts in the low-energy nano-oxygenation of incoming process water were achieved at a municipal wastewater treatment plant (WWTP) upstream of activated sludge (AS) aeration lanes on a single-pass basis by means of an electric field nanobubble (NB) generation method (with unit residence times of the order of just 10–15 s). Both ambient air and O2 cylinders were used as gas sources. In both cases, it was found that the levels of dissolved oxygen (DO) were maintained far higher for much longer than those of conventionally aerated water in the AS lane—and at DO levels in the optimal operational WWTP oxygenation zone of about 2.5–3.5 mg/L. In the AS lanes themselves, there were also excellent conversions to nitrate from nitrite, owing to reactive oxygen species (ROS) and some improvements in BOD and E. coli profiles. Nanobubble-enhanced Dissolved Air Flotation (DAF) was found to be enhanced at shorter times for batch processes: settlement dynamics were slowed slightly initially upon contact with virgin NBs, although the overall time was not particularly affected, owing to faster settlement once the recruitment of micro-particulates took place around the NBs—actually making density-filtering ultimately more facile. The development of machine learning (ML) models predictive of NB populations was carried out in laboratory work with deionised water, in addition to WWTP influent water for a second class of field-oriented ML models based on a more narrow set of more easily and quickly measured data variables in the field, and correlations were found for a more facile prediction of important parameters, such as the NB generation rate and the particular dependent variable that is required to be correlated with the efficient and effective functioning of the nanobubble generator (NBG) for the task at hand—e.g., boosting dissolved oxygen (DO) or shifting Oxidative Reductive Potential (ORP). Full article
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18 pages, 8048 KiB  
Article
Silicon Nanoparticles Alter Soybean Physiology and Improve Nitrogen Fixation Potential Under Atmospheric Carbon Dioxide (CO2)
by Jingbo Tong
Plants 2025, 14(13), 2009; https://doi.org/10.3390/plants14132009 - 30 Jun 2025
Viewed by 408
Abstract
The interactive effects between nano-silicon dioxide (n-SiO2) and elevated CO2 (eCO2; 645 ppm) on soybean physiology, nitrogen fixation, and nutrient dynamics under climate stress remain underexplored. This study elucidates their combined effects under ambient (aCO2 [...] Read more.
The interactive effects between nano-silicon dioxide (n-SiO2) and elevated CO2 (eCO2; 645 ppm) on soybean physiology, nitrogen fixation, and nutrient dynamics under climate stress remain underexplored. This study elucidates their combined effects under ambient (aCO2; 410 ppm) and eCO2 conditions. eCO2 + n-SiO2 synergistically enhanced shoot length (30%), total chlorophyll (112.15%), and photosynthetic rate (103.23%), alongside improved stomatal conductance and intercellular CO2 (17.19%), optimizing carbon assimilation. Nodulation efficiency increased, with nodule number and biomass rising by 48.3% and 53.6%, respectively, under eCO2 + n-SiO2 versus aCO2. N-assimilation enzymes (nitrate reductase, nitrite reductase, glutamine synthetase, glutamate synthase) surged by 38.5–52.1%, enhancing nitrogen metabolism. Concurrently, phytohormones (16–21%) and antioxidant activities (15–22%) increased, reducing oxidative markers (18–22%), and bolstering stress resilience. Nutrient homeostasis improved, with P, K, Mg, Cu, Fe, Zn, and Mn elevating in roots (13–41%) and shoots (13–17%), except shoot Fe and Zn. These findings demonstrate that n-SiO2 potentiates eCO2-driven benefits, amplifying photosynthetic efficiency, nitrogen fixation, and stress adaptation through enhanced biochemical and nutrient regulation. This synergy underscores n-SiO2 role in optimizing crop performance under future CO2-rich climates, advocating nano-fertilizers as sustainable tools for climate-resilient agriculture. Full article
(This article belongs to the Special Issue Silicon and Its Physiological Role in Plant Growth and Development)
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15 pages, 2347 KiB  
Article
Soil Biogeochemical Feedback to Fire in the Tropics: Increased Nitrification and Denitrification Rates and N2O Emissions Linked to Labile Carbon and Nitrogen Fractions
by Mengru Kong, Ali Mohd Yatoo, Rui Zhang, Junjie Feng, Xiaomeng Sun, Yunxing Wan, Yuhong Wen, Yanzheng Wu, Qiuxiang He, Lei Meng, Jinbo Zhang and Ahmed S. Elrys
Forests 2025, 16(6), 983; https://doi.org/10.3390/f16060983 - 11 Jun 2025
Viewed by 428
Abstract
Although tropical ecosystems have become increasingly vulnerable to fire over the past century, the mechanisms by which fire disturbance influences N2O emissions in these regions remain poorly understood. This study investigated the effects of fire on nitrous oxide (N2O) [...] Read more.
Although tropical ecosystems have become increasingly vulnerable to fire over the past century, the mechanisms by which fire disturbance influences N2O emissions in these regions remain poorly understood. This study investigated the effects of fire on nitrous oxide (N2O) emissions, the gross nitrification rate (GN), denitrification genes, and carbon (C) and nitrogen (N) fractions in a tropical forest. The results showed that fire increased the GN by 41.5%. The abundance of the nirK and nirS genes encoding nitrite reductase increased by 16.3% and 27.5%, respectively, while the abundance of the nosZI gene encoding N2O reductase increased by 28%, suggesting a potentially enhanced denitrification capacity. This enhancement in nitrification and denitrification was mainly due to increased easily oxidizable organic C (EOC, +35%), light fraction organic C (LFOC, +32%), hydrolyzable ammonium N (HAN, +13%), and amino sugar N (ASN, +11%), which provided additional substrates for nitrification and denitrification. As a result, soil N2O emissions increased by 18% in response to fire. Soil N2O emissions showed a significant and positive linear correlation with GN, EOC, LFOC, HAN, nirK, nirS, and nosZI. Thus, the post-fire increase in N2O emissions is likely driven by enhanced nitrification and denitrification processes, facilitated by the elevated availability of labile C and N fractions. Our findings provide new evidence for the role of soil C and N fractions in controlling N2O emission and nitrification–denitrification under fire disturbances in tropical soils. Full article
(This article belongs to the Section Forest Soil)
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20 pages, 5767 KiB  
Article
Mainstream Wastewater Treatment Process Based on Multi-Nitrogen Removal Under New Anaerobic–Swing–Anoxic–Oxic Model
by Jiashun Cao, Jinyu Wang and Runze Xu
Water 2025, 17(10), 1548; https://doi.org/10.3390/w17101548 - 21 May 2025
Viewed by 777
Abstract
The Anaerobic–Swing Aerobic–Anoxic–Oxic (ASAO) process was developed to tackle problems such as temperature sensitivity during the Anaerobic–Oxic–Anoxic (AOA) process. By introducing a swing zone (S zone) with adjustable dissolved oxygen (DO), during the 112-day experimentation period, the ASAO system achieved removal rates of [...] Read more.
The Anaerobic–Swing Aerobic–Anoxic–Oxic (ASAO) process was developed to tackle problems such as temperature sensitivity during the Anaerobic–Oxic–Anoxic (AOA) process. By introducing a swing zone (S zone) with adjustable dissolved oxygen (DO), during the 112-day experimentation period, the ASAO system achieved removal rates of 88.18% for total inorganic nitrogen (TIN), 78.23% for total phosphorus (TP), and 99.78% for ammonia nitrogen. Intermittent aeration effectively suppressed nitrite-oxidizing bacteria (NOB), and the chemical oxygen demand (COD) removal rate exceeded 90%, with 60% being transformed into internal carbon sources like polyhydroxyalkanoates (PHAs) and glycogen (Gly). The key functional microorganisms encompassed Dechloromonas (denitrifying phosphorus-accumulating bacteria), Candidatus Competibacter, and Thauera, which facilitated simultaneous nitrification–denitrification (SND) and anaerobic ammonium oxidation (ANAMMOX). The enrichment of Candidatus Brocadia further enhanced the ANAMMOX activity. The flexibility of DO control in the swing zone optimized microbial activity and mitigated temperature dependence, thereby verifying the efficacy of the ASAO process in enhancing the removal rates of nutrients and COD in low-C/N wastewater. The intermittent aeration strategy and the continuous low-dissolved-oxygen (DO) operating conditions inhibited the activity of nitrite-oxidizing bacteria (NOB) and accomplished the elimination of NOB. Full article
(This article belongs to the Section Water Quality and Contamination)
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14 pages, 3022 KiB  
Article
Denitrification by Purple Phototrophic Bacteria: A Carbon-Neutral and Resource-Efficient Route for Nitrogen Removal
by Xiaoshuai Peng, Siwei Yu, Chuanzhou Liang, Yifeng Xu and Lai Peng
Sustainability 2025, 17(10), 4504; https://doi.org/10.3390/su17104504 - 15 May 2025
Viewed by 454
Abstract
Purple phototrophic bacteria (PPB) have great potential in treating nitrogen-contaminated wastewater. Unlike conventional heterotrophic denitrification, PPB-driven denitrification utilizes light-driven metabolism, concurrently improving nitrogen removal and carbon management efficiency. This work aimed to develop a PPB denitrification process for nitrogen removal, carbon emission mitigation, [...] Read more.
Purple phototrophic bacteria (PPB) have great potential in treating nitrogen-contaminated wastewater. Unlike conventional heterotrophic denitrification, PPB-driven denitrification utilizes light-driven metabolism, concurrently improving nitrogen removal and carbon management efficiency. This work aimed to develop a PPB denitrification process for nitrogen removal, carbon emission mitigation, and resource recovery. The PPB growth was first optimized and the most desirable light and carbon sources (i.e., incandescent light and sodium acetate) were pinpointed. PPB denitrification could reach a nitrate removal rate of 0.68 mg N/L/h, while no nitrite was detected during the process, regardless of the amount of external electron donors. This was attributed to the fact that the true reduction rate of nitrite (4.42 mg N/gVSS/h) was significantly higher than that of nitrate (1.51 mg N/gVSS/h). In the presence of a sufficient carbon source, PPB denitrification was found to be a low-carbon process, with only ~0.17% of converted nitrate being emitted as nitrous oxide. Meanwhile, PPB biomass for denitrification was rich in value-added products (e.g., protein and pigment), which potentially generated additional benefits over the biomass valued at USD 17 kg−1. These results provide a theoretical basis for implementing PPB denitrification for carbon-neutral and resource-efficient wastewater treatment. Full article
(This article belongs to the Special Issue Wastewater Treatment Technology and Environmental Sustainability)
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13 pages, 2397 KiB  
Communication
Impact of Tire-Derived Microplastics on Microbiological Activity of Aerobic Granular Sludge
by Weronika Irena Mądzielewska, Piotr Jachimowicz, Job Oliver Otieno and Agnieszka Cydzik-Kwiatkowska
Int. J. Mol. Sci. 2025, 26(9), 4136; https://doi.org/10.3390/ijms26094136 - 27 Apr 2025
Viewed by 605
Abstract
In recent years, there has been an increase in the emission of tire wear particle (TWP) microplastics from wastewater treatment plants into the environment. The aim of this study was to determine the effect of TWPs in wastewater flowing into a biological reactor [...] Read more.
In recent years, there has been an increase in the emission of tire wear particle (TWP) microplastics from wastewater treatment plants into the environment. The aim of this study was to determine the effect of TWPs in wastewater flowing into a biological reactor on the transcription of the 16S rRNA gene and the key genes responsible for nitrogen metabolism, amoA, nirK and nosZ, in aerobic granular sludge. The laboratory experiment was carried out in sequencing aerobic granular sludge reactors operated in an 8 h cycle into which TWP microplastics were introduced with municipal wastewater at a dose of 50–500 mg TWPs/L. The ammonia removal rate and the production of oxidized forms of nitrogen increased with the TWP dose. Gene transcript abundance analysis showed that the presence of rubber and substances leached from it promoted the activity of ammonium-oxidizing bacteria (160% increase), while the transcription of genes related to denitrification conversions was negatively affected. The activity of nitrite reductase gradually decreased with increasing TWP concentration in wastewater (decreased by 33% at 500 mg TWPs/L), while nitric oxide reductase activity was significantly inhibited even at the lowest TWP dose (decreased by 58% at 500 mg TWPs/L). The data obtained indicate that further studies are needed on the mechanisms of the effects of TWPs on the activities of the most important groups of microorganisms in wastewater treatment to minimize the negative effects of TWPs on biological wastewater treatment. Full article
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17 pages, 3800 KiB  
Article
Effects of High Salinity on Nitrogen Removal Efficiency and Microbial Community Structure in a Three-Stage AO System
by Shengyu Shi, Pengfei Cui, Shasha Wang, Jun Long and Xiaojun Yang
Water 2025, 17(8), 1112; https://doi.org/10.3390/w17081112 - 8 Apr 2025
Viewed by 815
Abstract
This study investigated the nitrogen removal performance of a three-stage AO reactor for refractory TN and the changes in microbial community structure within the activated sludge system under varying sodium chloride concentration conditions. Under an influent sodium chloride concentration of 0 g/L with [...] Read more.
This study investigated the nitrogen removal performance of a three-stage AO reactor for refractory TN and the changes in microbial community structure within the activated sludge system under varying sodium chloride concentration conditions. Under an influent sodium chloride concentration of 0 g/L with sufficient carbon source, the removal rates of Total Nitrogen (TN), Chemical Oxygen Demand (CODcr), and Ammonium (NH4+-N) remained stable at 98%, 99.7%, and 99.9%, respectively. When the sodium chloride concentration increased to 20 g/L, the activity of AOB was significantly inhibited, with removal efficiency rates dropping to 83%, 89%, and 70%, respectively, and the NAR increasing to 91.97%. Analytical results demonstrated that both ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) exhibited inhibited metabolic activities, with NOB experiencing earlier functional impairment. Under NaCl concentrations ≤ 10 g/L, conventional nitrogen removal via nitrification–denitrification (ND) remained dominant. When NaCl concentrations exceeded 10 g/L, due to the accumulation of NO2-N, the phyla Planctomycetota and Proteobacteria maintained dominance in the microbial community, while partial nitrification (PN) and denitrification pathways gradually replaced ND. Extracellular polymeric substance (EPS) secretion emerged as the primary microbial defense mechanism against salinity stress. Experimental findings informed proposed strategies including phased acclimatization for salt-tolerance enhancement, EPS production regulation, and targeted enrichment of functional consortia, which collectively improved the denitrification efficiency by 18.7–22.3% under salinity levels ≤ 20 g/L. This study provides theoretical foundations and technical references for process optimization in hypersaline industrial wastewater treatment systems. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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18 pages, 3581 KiB  
Article
Isolation and Characterization of Ammonia-Oxidizing Bacterium N.eA1: Insights into Nitrogen Conversion and N2O Emissions in Varied Environmental Conditions
by Yuhang Liu, Kai Li, Zhiyao Yan, Zhijun Ren, Xueying Li and Haobin Yang
Water 2025, 17(7), 1027; https://doi.org/10.3390/w17071027 - 31 Mar 2025
Cited by 1 | Viewed by 663
Abstract
While temperature, pH, DO, and ammonia nitrogen concentration are known to affect nitrous oxide (N2O) emissions from ammonia-oxidizing bacteria (AOB), the specific responses of individual AOB species to these environmental variables have yet to be fully elucidated. The present study reports [...] Read more.
While temperature, pH, DO, and ammonia nitrogen concentration are known to affect nitrous oxide (N2O) emissions from ammonia-oxidizing bacteria (AOB), the specific responses of individual AOB species to these environmental variables have yet to be fully elucidated. The present study reports the isolation and pure culture of a new AOB strain, designated as N.eA1, from a stable CANON bioreactor. The strain’s denitrification and N2O emission were systematically evaluated through a comprehensive analysis of growth kinetics, morphological characteristics, genetic composition, and nitrogen transformation under various environmental processes. Our results indicated that N.eA1 shares 95.33% sequence homology with Nitrosomonas europaea H1 AOB3, and exhibited higher nitrite (NO2-N) conversion efficiency. Morphological examination revealed white, semi-transparent spherical colonies. The bacterial growth kinetics included adaptation phase (0–12 h), exponential growth phase (12–36 h), stationary phase (36–72 h) and decline phase (after 72 h). Under optimal cultivation conditions (30 °C, DO concentration of 7.3 mg∙L−1, pH 8.0, and NH4+-N concentration of 260 mg∙L−1), the culture achieved a maximum growth rate of 0.0723 h−1, a maximum ammonia oxidation rate (AOR) of 10.74 mg∙(MLVSS∙h)−1, and a minimum doubling time of 9.59 h. The peak time of nitrogen conversion was earlier than that of N2O emission, with a maximum N2O-N conversion from NH4+-N of 1.039%. Full article
(This article belongs to the Special Issue ANAMMOX Based Technology for Nitrogen Removal from Wastewater)
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14 pages, 2278 KiB  
Review
Research Progress on Biological Denitrification Process in Wastewater Treatment
by Yuling Ye, Keyuan Zhang, Xiantao Peng, Qiang Zhou, Zhicheng Pan, Bo Xing and Xiaonan Liu
Water 2025, 17(4), 520; https://doi.org/10.3390/w17040520 - 12 Feb 2025
Cited by 2 | Viewed by 3248
Abstract
Nitrogen removal in the sewage treatment process is a significant challenge. The increase in nitrogen content in sewage leads to the eutrophication of water bodies and the deterioration of water quality in polluted environments. Therefore, converting nitrogen into non-polluting gases is a crucial [...] Read more.
Nitrogen removal in the sewage treatment process is a significant challenge. The increase in nitrogen content in sewage leads to the eutrophication of water bodies and the deterioration of water quality in polluted environments. Therefore, converting nitrogen into non-polluting gases is a crucial and essential part of the sewage treatment process. Compared to physical, chemical, and physicochemical methods, biological denitrification is not only simple to operate and economically effective but also has less secondary pollution and saves energy. This paper summarizes the latest research progress on mainstream biological denitrification technology in WWTPS (wastewater treatment plants) and discusses its research background, methodology, and challenges. It is noted that the traditional biological nitrogen removal method is stable and widely used, but it has drawbacks such as high costs and long reaction times, especially in high-nitrogen-load wastewater treatment where its effectiveness is limited. The short-cut nitrification–denitrification process suits high-nitrogen-loading and a low C/N ratio wastewater as it reduces carbon source consumption. However, the problems of water quality fluctuation and unstable dissolved oxygen still need to be solved. The anaerobic ammonia oxidation process efficiently converts ammonia and nitrite to nitrogen using anaerobic ammonia-oxidizing bacteria, consuming less energy but facing limitations due to slow bacterial growth rates and stringent environmental conditions. The heterotrophic nitrification–aerobic denitrification process merges the traits of heterotrophic nitrifying bacteria and aerobic denitrifying bacteria, effectively reducing the ecological footprint and enhancing treatment efficiency. This approach is a pivotal focus for future research endeavors. Full article
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22 pages, 754 KiB  
Systematic Review
Nitrate–Nitrite–Nitric Oxide Pathway, Oxidative Stress, and Fertility Outcomes in Morbidly Obese Women Following Bariatric Surgery: A Systematic Review
by Charalampos Voros, Despoina Mavrogianni, Aspasia Minaoglou, Alexios Karakasis, Anthi-Maria Papahliou, Vasileios Topalis, Antonia Varthaliti, Raphail Mantzioros, Panagiota Kondili, Menelaos Darlas, Regina Sotiropoulou, Diamantis Athanasiou, Dimitrios Loutradis and Georgios Daskalakis
Biomedicines 2025, 13(1), 64; https://doi.org/10.3390/biomedicines13010064 - 30 Dec 2024
Cited by 2 | Viewed by 1446
Abstract
Obesity reduces nitric oxide (NO) production due to endothelial nitric oxide synthase (eNOS) dysfunction, resulting in oxidative stress, mitochondrial dysfunction, and chronic inflammation. These factors have a negative impact on reproductive health, including oocyte quality, endometrial receptivity, and embryo implantation. When oxidative stress [...] Read more.
Obesity reduces nitric oxide (NO) production due to endothelial nitric oxide synthase (eNOS) dysfunction, resulting in oxidative stress, mitochondrial dysfunction, and chronic inflammation. These factors have a negative impact on reproductive health, including oocyte quality, endometrial receptivity, and embryo implantation. When oxidative stress affects eNOS function, the nitrate–nitrite–nitric oxide (NO3-NO2-NO) pathway provides an alternate route for NO production. Bariatric surgery has been found to restore NO production, reduce oxidative stress, and improve fertility in morbidly obese women. This review investigates the molecular mechanisms by which bariatric surgery affects eNOS activity, the NO3-NO2-NO pathway, and oxidative stress reduction, with an emphasis on intracellular activities including mitochondrial biogenesis and NO production. A systematic review employing PRISMA criteria included articles published between 2000 and 2024 from PubMed, Scopus, and Embase that investigated NO3-NO2 pathways, oxidative stress markers, hormonal alterations, and reproductive outcomes in morbidly obese women following bariatric surgery. After evaluating 1542 studies, 11 were selected for the final analysis. Results showed a 45% increase in NO3-NO2 levels (p < 0.001), a 35% reduction in oxidative stress indicators (p < 0.01), a 60% increase in pregnancy rates, and a 50% increase in spontaneous ovulation rates following surgery. These benefits were connected to improved mitochondrial function and endometrial receptivity as a result of reduced oxidative stress and inflammation. The NO3-NO2-NO route is critical in compensating for lower NO generation under oxidative stress and hypoxia, and bariatric surgery significantly improves this pathway to optimize blood flow, mitochondrial function, and reproductive results. Full article
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13 pages, 1598 KiB  
Article
Nitrite Cycling in Freshwater Ecosystems: A Case Study of an Artificial Reservoir in Eastern China Using Nitrite Dual Isotopes Combined with a Geochemical Model
by Xinwei Li, Xingzhou Zhang, Yuanyuan Yang, Yingying Li, Lujie Jia and Yangjun Chen
Sustainability 2024, 16(24), 11099; https://doi.org/10.3390/su162411099 - 18 Dec 2024
Viewed by 1098
Abstract
Reservoirs are hotspots for emissions of the greenhouse gas nitrous oxide; however, the nitrite cycling processes associated with nitrous oxide production therein remain poorly understood, limiting a better assessment of the potential for reservoirs to emit nitrous oxide. Accordingly, this study presents the [...] Read more.
Reservoirs are hotspots for emissions of the greenhouse gas nitrous oxide; however, the nitrite cycling processes associated with nitrous oxide production therein remain poorly understood, limiting a better assessment of the potential for reservoirs to emit nitrous oxide. Accordingly, this study presents the application of the natural abundance isotope technique combined with a geochemical model to elucidate the nitrite cycling in the freshwater aquaculture and non-aquaculture zones of a large artificial reservoir in eastern China. We employed nitrite dual isotopes to identify nitrite transformation processes. Additionally, a steady-state model was used to estimate the rates of these processes as well as the residence time of nitrite. Our findings indicate that nitrite production in this reservoir may be primarily driven by ammonia oxidation. However, the pathways of nitrite removal differ notably between the aquaculture and non-aquaculture zones, suggesting a significant impact of the aquaculture activities. The steady-state model calculations revealed that nitrification may be more pronounced in the aquaculture zones compared to the non-aquaculture zones, which may be related to the altered balance of competition for substrates between phytoplankton and microbes induced by aquaculture activities. Moreover, we observed a latitude-dependent increase in the significance of nitrite oxidation in natural environments, highlighting potential implications for regional and global nitrogen cycling. Our study highlights the complexity of the nitrite cycle and emphasizes the roles of both natural and anthropogenic factors in shaping nitrogen dynamics within freshwater reservoirs. This understanding contributes to a more accurate assessment of the greenhouse gas emission potential of reservoirs, offering valuable implications for the adoption of sustainable aquaculture practices to mitigate climate impacts and support global sustainable development goals. Full article
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38 pages, 2806 KiB  
Article
Removal of Organic Micropollutants and Microplastics via Ozonation Followed by Granular Activated Carbon Filtration
by Zoé Béalu, Johanna Walther, Attaallah Abusafia, Korinna Altmann, Maren Meurer, Oliver Gretzschel, Michael Schäfer and Heidrun Steinmetz
Environments 2024, 11(11), 241; https://doi.org/10.3390/environments11110241 - 31 Oct 2024
Cited by 3 | Viewed by 3397
Abstract
Discharge from Wastewater Treatment Plants (WWTPs) can result in the emission of organic micropollutants (OMPs) and microplastics (MPs) into the aquatic environment. To prevent this harmful release, a pilot plant consisting of an ozonation followed by a granular activated carbon (GAC) filter was [...] Read more.
Discharge from Wastewater Treatment Plants (WWTPs) can result in the emission of organic micropollutants (OMPs) and microplastics (MPs) into the aquatic environment. To prevent this harmful release, a pilot plant consisting of an ozonation followed by a granular activated carbon (GAC) filter was operated at a WWTP in Germany, and its side-effects on the concentrations of nitrogen (N) and phosphorous (P) compounds were measured. Over 80% of OMPs and transformation products were removed during the operating time (around 6000 bed volumes) no matter the ozone dose (from around 0.1 to 0.5 mgO3/mgDOC), except for Diatrizoic acid, whose breakthrough appeared at 3500 BV. Formation of the oxidation by-product, NDMA, increased with higher ozone doses, but the concentration remained below 100 ng/L. Bromate was formed at a higher ozone dose (>0.4 mgO3/mgDOC) but at a low concentration—below 10 µg/L. The MP particles detected in the inflow (PE, SBR, PP, and PS) were effectively eliminated to a high degree, with a removal rate of at least 92%. Carbon parameters (COD, DOC, and SAC254) were removed further by the pilot plant, but to different extents. As expected, nitrate was formed during ozonation, while nitrite’s concentration decreased. Further, nitrite decreased and nitrate increased within the GAC filter, while ammonium was eliminated by at least 90%. Total P concentration decreased after the pilot, but the concentration of PO4-P increased. Full article
(This article belongs to the Special Issue Advanced Technologies of Water and Wastewater Treatment (2nd Edition))
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9 pages, 4097 KiB  
Article
Microalgae Enhance the Resistance of Pond-Dwelling Ammonia-Oxidizing Bacteria to Light Irradiation
by Shimin Lu, Yayuan Li, Zehui Yuan, Xingguo Liu, Xuan Che, Guofeng Cheng, Zhaojun Gu and Fan Wu
Processes 2024, 12(10), 2261; https://doi.org/10.3390/pr12102261 - 16 Oct 2024
Viewed by 1228
Abstract
Pond aquaculture is an important aquacultural model worldwide in which ammonia-oxidizing bacteria (AOB) are crucial for the removal of ammonia from water. The influence of light irradiation on AOB in an aquaculture pond was studied using artificial simulation wastewater under dark/light cycles of [...] Read more.
Pond aquaculture is an important aquacultural model worldwide in which ammonia-oxidizing bacteria (AOB) are crucial for the removal of ammonia from water. The influence of light irradiation on AOB in an aquaculture pond was studied using artificial simulation wastewater under dark/light cycles of 24 h/0 h (L0), 12 h/12 h (L12), and 0 h/24 h (L24). The ammonia oxidation rates (AORs) in groups L0, L12, and L24 were 9.88 ± 0.19 mg h−1, 6.01 ± 0.32 mg h−1, and 1.85 ± 0.09 mg h−1, respectively. Long-term exposure to light had a serious impact on the AOR and decreased the abundance of Nitrosomonas spp. and their ammonia monooxygenase genes. To determine the protective effect of microalgae on AOB, different doses of freeze-dried Chlorella spp. powder were added to the nitrifying bacteria community. The photoinhibition rate of chlorophyll a (Chla) in the groups with 300 and 1300 µg L−1 of added Chlorella were 32.85% and 28.77%, respectively, while the Chla in the 2200 µg L−1 Chlorella-added group was only 0.01%, with no significant differences (p > 0.05) in AOR between the dark/light treatment subgroups. Fluorescence in situ hybridization showed that AOB, nitrite-oxidizing bacteria, and algae coexist and grow together without free AOB in the nitrifying bacterial community. It was suggested that microalgae enhance the resistance of AOB to light irradiation in a pond through the shading effect provided by algal chlorophyll and the close symbiotic relationship between microalgae and AOB. Full article
(This article belongs to the Section Sustainable Processes)
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