Outdoor Artificial Light at Night and Reproductive Endocrine and Glucose Homeostasis and Polycystic Ovary Syndrome in Women of Reproductive Age.

BACKGROUND: Artificial light at night, a well-recognized circadian clock disrupter, causes disturbances in endocrine homeostasis. However, the association of artificial light at night with polycystic ovary syndrome (PCOS) is still unknown. This study examines the effects of outdoor artificial light at night on sex hormones, glucose homeostasis markers, and PCOS prevalence in Anhui Province, China. METHODS: We recruited 20,633 women of reproductive age from Anhui Medical University Reproductive Medicine Center. PCOS was diagnosed according to Rotterdam criteria. We estimated long-term (previous year) and short-term (previous month) artificial light at night values for residential addresses using 500 m resolution satellite imagery. We fitted multivariable models, using both linear and logistic regression, to estimate the association of artificial light at night with sex hormones, glucose homeostasis markers, and PCOS prevalence. RESULTS: Both long-term and short-term exposure to outdoor artificial light at night were negatively associated with follicle-stimulating hormone and luteinizing hormone levels, while positively associated with testosterone, fasting insulin, homeostasis model assessment-insulin resistance, and homeostasis model assessment-insulin resistance-ß levels. The second-highest quintile of artificial light at night was associated with increased PCOS prevalence (odds ratio [OR long-term ] = 1.4; 95% confidence interval [CI] = 1.2, 1.6 and OR short-term = 1.3; 95% CI = 1.1, 1.5) compared with the lowest quintile. In addition, prevalence of PCOS was linearly associated with long-term exposure to artificial light at night, but nonlinearly associated with short-term exposure. This association was more evident in younger, obese or overweight, moderately educated, rural women, and for the summer and fall seasons. CONCLUSION: Outdoor artificial light at night may be a novel risk factor for PCOS.

Combined Phototrophic Simultaneous Nitrification-Endogenous Denitrification with Phosphorus Removal (P-SNDPR) System Treating Low Carbon to Nitrogen Ratio Wastewater for Potential Carbon Neutrality.

Conventional biological nutrient removal processes rely on external aeration and produce significant carbon dioxide (CO2) emissions. This study constructed a phototrophic simultaneous nitrification-denitrification phosphorus removal (P-SNDPR) system to treat low carbon to nitrogen (C/N) ratios wastewater and investigated the impact of sludge retention time (SRT) on nutrient removal performance, nitrogen conversion pathway, and microbial structure. Results showed that the P-SNDPR system at SRT of 15 days had the highest nutrient removal capacity, achieving over 85% and 98% removal of nitrogen and phosphorus, respectively, meanwhile maintaining minimal CO2 emissions. Nitrogen removal was mainly through assimilation at SRTs of 5 and 10 days, and nitrification-denitrification at SRTs of 15 and 20 days. Stable partial nitrification was facilitated by photoinhibition and low DO levels. Flow cytometry sorting technique results revealed SRT drove community structural changes in translational activity (BONCAT+) microbes, where BONCAT+ microbes were mainly simultaneous nitrogen and phosphorus removal bacteria (Candidatus Accumulibacter), denitrifying bacteria (Candidatus Competibacter and Plasticicumulans), ammonia-oxidizing bacteria (Nitrosomonas), and microalgae (Chlorella and Dictyosphaerium). The P-SNDPR system represents a novel, carbon-neutral process for efficient nutrient removal from low C/N ratio wastewater without aeration and external carbon source additions.

Synchronous Achievement of Advanced Nitrogen Removal and N2O Reduction in the Anoxic Zone in the AOA Process for Low C/N Municipal Wastewater.

Continuous flow processes for the in situ determination of N2O emissions during low C/N municipal wastewater treatment have rarely been reported. The anaerobic/aerobic/anoxic (AOA) process has recently shown promising potential in energy savings and advanced nitrogen removal, but it still needs to be comprehensively explored in relation to N2O emissions for its carbon reduction advantages. In this study, a novel gas-collecting continuous flow reactor was designed to comprehensively evaluate the emissions of N2O from the gas and liquid phases of the AOA process. Additionally, the measures of enhancing endogenous denitrification (ED) and self-enriching anaerobic ammonium oxidation (Anammox) were employed to optimize nitrogen removal and achieve N2O reduction in the anoxic zone. The results showed that enhanced ED coupled with Anammox led to an increase in the nitrogen removal efficiency (NRE) from 67.65 to 81.96%, an enhancement of the NO3- removal rate from 1.76 mgN/(L h) to 3.99 mgN/(L h), and the N2O emission factor in the anoxic zone decreased from 0.28 to 0.06%. Impressively, ED eliminated 91.46 ± 2.47% of the dissolved N2O from the upstream aerobic zone, and the dissolved N2O in the effluent was reduced to less than 0.01 mg/L. This study provides valuable strategies for fully evaluating N2O emissions and N2O reduction from the AOA process.

Effects of environmental temperature extremes exposure on sperm quality - evidence from a prospective cohort study in Anhui Province, China.

Extreme weather is becoming more frequent due to drastic changes in the climate. Despite this, the body of research focused on the association between temperature extreme events and sperm quality remains sparse. In this study, we elucidate the impact of exposure to environmental temperature extremes on sperm quality. Data for this investigation were derived from the Anhui Prospective Assisted Reproduction Cohort, encompassing the period from 2015 to 2020. Parameters such as sperm concentration, total sperm count, total motility, progressive motility, total motile sperm count, and progressive motile sperm count were quantified from semen samples. We assessed the exposure of participants to temperature extremes during the 0-90 days prior to sampling. This investigation encompassed 15,112 participants, yielding 28,267 semen samples. Our research findings indicate that exposure to low temperature extreme for three consecutive days (at the first percentile threshold) has a detrimental correlation with sperm count parameters and concentration. Similar trends were observed with the second percentile threshold, where significant adverse effects typically manifested after a four-day exposure sequence. Analysis of high temperature extreme showed that exposure at the 98th percentile had adverse effects on all six sperm quality parameters, and the sperm count parameter was particularly sensitive to high temperature, showing significant results immediately after three days of exposure. When considering even more temperature extreme (99th percentile), the negative consequences were more pronounced on the sperm count parameter. Additionally, progressive motility showed a stronger negative response. In summary, parameters associated with sperm count are particularly vulnerable to temperature extremes exposure. Exposure to high temperature extremes environments may also be associated with a decrease in sperm concentration and vitality. The findings of this study suggest that male population should pay attention to avoid exposure to temperature extreme environment, which has important significance for improving the quality of human fertility.

The impact of short-term exposure to meteorological factors on the risk of death from hypertension and its major complications: a time series analysis based on Hefei, China.

OBJECTIVES: This study aimed to reveal the short-term impact of meteorological factors on the mortality risk in hypertensive patients, providing a scientific foundation for formulating pertinent prevention and control policies. METHODS: In this research, meteorological factor data and daily death data of hypertensive patients in Hefei City from 2015 to 2018 were integrated. Time series analysis was performed using distributed lag nonlinear model (DLNM) and generalized additive model (GAM). Furthermore, we conducted stratified analysis based on gender and age. Relative risk (RR) combined with 95% confidence interval (95% CI) was used to represent the mortality risk of single day and cumulative day in hypertensive patients. RESULTS: Single-day lag results indicated that high daily mean temperature (T mean) (75th percentile, 24.9 °C) and low diurnal temperature range (DTR) (25th percentile, 4.20 °C) levels were identified as risk factors for death in hypertensive patients (maximum effective RR values were 1.144 and 1.122, respectively). Extremely high levels of relative humidity (RH) (95th percentile, 94.29%) reduced the risk of death (RR value was 0.893). The stratified results showed that the elderly and female populations are more susceptible to low DTR levels, whereas extremely high levels of RH have a more significant protective effect on both populations. CONCLUSION: Overall, we found that exposure to low DTR and high T mean environments increases the risk of death for hypertensive patients, while exposure to extremely high RH environments significantly reduces the risk of death for hypertensive patients. These findings contribute valuable insights for shaping targeted prevention and control strategies.

Sponge iron strengthens the activity of anammox biofilm under low nitrogen conditions in a two-stage fixed-bed biofilm reactor.

Strengthening the activity competitiveness of anaerobic ammonium oxidation (anammox) bacteria (AnAOB) under low nitrogen conditions is indispensable for mainstream anammox application. This study demonstrates that sponge iron addition (42.8 g/L) effectively increased apparent AnAOB activity and extracellular polymeric substance (EPS) production of low load anammox biofilms cultivated under low (influent of 60 mg N/L) and even ultra-low (influent of 10 mg N/L) nitrogen conditions. In-situ batch tests showed that after sponge iron addition the specific AnAOB activity in the low and ultra-low nitrogen systems further increased to 1.18 and 0.47 mmol/g VSS/h, respectively, with an apparent growth rate for AnAOB of 0.011 ± 0.001 d-1 and 0.004 ± 0.001 d-1, respectively. The averaged EPS concentration of anammox biofilm in both low (from 35.84 to 71.05 mg/g VSS) and ultra-low (from 44.14 to 57.59 mg/g VSS) nitrogen systems increased significantly, while a higher EPS protein/polysaccharide ratio, which was positively correlated with AnAOB activity, was observed in the low nitrogen system (3.54 ± 0.34) than that in the ultra-low nitrogen system (1.82 ± 0.10). In addition, Candidatus Brocadia was detected as dominant AnAOB in the anammox biofilm under the low (12.2 %) and ultra-low (24.7 %) nitrogen condition. Notably, the genus Streptomyces (26.3 %), capable for funge-like codenitrification, increased unexpectedly in the low nitrogen system, but not affecting the nitrogen removal performance. Therefore, using sponge iron to strengthen AnAOB activity under low nitrogen conditions is feasible, providing support for mainstream anammox applications.

Optimizing sludge retention time for sustainable photo-enhanced biological phosphorus removal systems: Insights into nutrient fate, microbial community, and bacterial phototolerance.

Photo-enhanced Biological Phosphorus Removal (PEBPR) systems, promising wastewater treatment technology, offer efficient phosphorus removal without external oxygen. However, comprehending the impact of sludge retention time (SRT) on the system is crucial for successful implementation. This study investigated the SRT effect on nutrient fate, microbial community, and bacterial phototolerance in PEBPR systems. PEBPR systems exhibited good bacterial phototolerance at SRT of 10, 15, and 20 d, with optimal phosphorus-accumulation metabolism observed at SRT of 10 and 15d. However, at SRT of 5d, increased light sensitivity and glycogen-accumulating organisms (GAOs) growth resulted in poor P removal (71.9%). Accumulibacter-IIC were the dominant P accumulating organisms (PAOs) at SRT of 10, 15, and 20 d. Accumulibacter-I, IIC and IIF were the major PAOs at SRT of 5 d. The decrease in SRT promoted the microalgal population diversity, and Dictyosphaerium and Chlorella were the major microalgal species in this study. Flow cytometry results revealed high light intensity triggered intracellular Fe2+ efflux, limiting translation activity and metabolism. Moreover, PAOs had lower phototolerance than GAOs due to Poly-P bound intracellular Mg2+ affecting enzyme activity. This study provides an in-depth understanding of PEBPR systems operation strategy toward environmentally sustainable wastewater treatment.

Treatment of low-C/N nitrate wastewater using a partial denitrification-anammox granule system: Granule reconstruction, stability, and microbial structure analyses.

Industrial wastewater discharged into sewer systems is often characterized by high nitrate contents and low C/N ratios, resulting in high treatment costs when using conventional activated sludge methods. This study introduces a partial denitrification-anammox (PD/A) granular process to address this challenge. The PD/A granular process achieved an effluent TN level of 3.7 mg/L at a low C/N ratio of 2.3. Analysis of a typical cycle showed that the partial denitrification peaked within 15 min and achieved a nitrate-to-nitrite transformation ratio of 86.9%. Anammox, which was activated from 15 to 120 min, contributed 86.2% of the TN removal. The system exhibited rapid recovery from post-organic shock, which was attributed to significant increases in protein content within TB-EPS. Microbial dispersion and reassembly were observed after coexistence of the granules, with Thauera (39.12%) and Candidatus Brocadia (1.25%) identified as key functional microorganisms. This study underscores the efficacy of PD/A granular sludge technology for treating low-C/N nitrate wastewater.

Multipathway of Nitrogen Metabolism Revealed by Genome-Centered Metatranscriptomics from Pyrite-Guided Mixotrophic Partial Denitrification/Anammox Installations.

Further reducing the organic requirements is essential for the sustainable development of partial denitrification/anammox technology. Here, an innovative mixotrophic partial denitrification/anammox (MPD/A) installation fed with pyrite and few organics was realized, and the average nitrogen and phosphorus removal rates were as high as 96.24 ± 0.11% and 79.23 ± 2.06%, respectively, with a C/N ratio of 0.5. To understand the nature by which MPD/A achieves efficient nitrogen removal and organic conservation, the electron transfer-dependent nitrogen escape and energy metabolism were first elucidated using multiomics analysis. Apart from heterotrophic denitrification and anammox, the results revealed some unexpected metabolic couplings of MPD/A systems, in particular, putative nitrate-dependent organic and pyrite oxidation among nominally heterotrophic Denitratisoma (PRO3) strains, which accelerated nitrate gasification with a low-carbon supply. Additionally, Candidatus Brocadia (AMX) employed extracellular solid-state electron acceptors as terminal electron sinks for high-rate ammonium removal. AMX transported ammonium electrons to extracellular γFeO(OH) (generated from pyrite oxidation) through the transient storage of menaquinoline pools, cytoplasmic migration via multiheme cytochrome(s), and OmpA protein/nanowires-mediated electron hopping on cell surfaces. Further investigation observed that extracellular electron flux resulted in the transfer of more energy from the increased oxidation of the electron donor to the ATP, supporting nitrite-independent ammonium removal.

Spatiotemporal Assembly and Immigration of Heterotrophic and Anammox Bacteria Allow a Robust Synergy for High-Rate Nitrogen Removal.

The novel partial denitrification-driven anammox (PD/A) is an energy-efficient method for nitrogen removal from wastewater. However, its stability and efficiency are impeded by the competition between heterotrophic denitrifying bacteria and relatively slow-growing anammox bacteria. In this study, a PD/A granular sludge system was developed, which achieved a nitrogen removal efficiency of 94% with 98% anammox contribution, even as the temperature dropped to 9.6 °C. Analysis of bacterial activity in aggregates of different sizes revealed that the largest granules (>2.0 mm) exhibited the highest anammox activity, 2.8 times that of flocs (<0.2 mm), while the flocs showed significantly higher nitrite production rates of PD, more than six times that of the largest granules. Interestingly, fluorescent in situ hybridization (FISH) combined with confocal laser scanning microscopy (CLSM) revealed a nest-shaped structure of PD/A granules. The Thauera genus, a key contributor to PD, was highly enriched at the outer edge, providing substrate nitrite for anammox bacteria inside the granules. As temperature decreased, the flocs transformed into small granules to efficiently retain anammox bacteria. This study provides multidimensional insights into the spatiotemporal assembly and immigration of heterotrophic and autotrophic bacteria for stable and high-rate nitrogen removal.

Anammox Coupled with Photocatalyst for Enhanced Nitrogen Removal and the Activated Aerobic Respiration of Anammox Bacteria Based on cbb3-Type Cytochrome c Oxidase.

This study introduced photogenerated electrons into the anammox system by coupling them to a g-C3N4 nanoparticle photocatalyst. A high nitrogen removal efficiency (94.25%) was achieved, exceeding the biochemical limit of 89% imposed by anammox stoichiometry. Photogenerated electrons boosted anammox metabolic activity by empowering key enzymes (NIR, HZS, and WLP-related proteins) and triggered rapid algal enrichment by enhancing the algal Calvin cycle, thus developing multiple anammox-algae synergistic nitrogen removal processes. Remarkably, the homologous expression of cbb3-type cytochrome c oxidase (CcO) in anammox bacteria was discovered and reported in this study for the first time. This conferred aerobic respiration capability to anammox bacteria and rendered them the principal oxygen consumer under 7.9-19.8 mg/L dissolved oxygen, originating from algal photosynthesis. Additionally, photogenerated electrons selectively targeted the cb1 complex and cbb3-type CcO as activation sites while mobilizing the RegA/B regulatory system to activate the expression of cbb3-type CcO. Furthermore, cbb3-type CcO blocked oxidative stress in anammox by depleting intracellular oxygen, a substrate for reactive oxygen species synthesis. This optimized the environmental sensitivity of anammox bacteria and maintained their high metabolic activity. This study expands our understanding of the physiological aptitudes of anammox bacteria and provides valuable insights into applying solar energy for enhanced wastewater treatment.

Highly Enriched Anammox Bacteria with a Novel Granulation Model Regulated by Epistylis spp. in Domestic Wastewater Treatment.

Anammox granulation is an efficient solution proffered to enrich slow-growing anammox bacteria (AnAOB), but the lack of effective granulation strategies for low-strength domestic wastewater impedes its application. In this study, a novel granulation model regulated by Epistylis spp. for highly enriched AnAOB was revealed for the first time. Notably, anammox granulation was achieved within 65 d of domestic wastewater treatment. The stalks of Epistylis spp. were found to act as the skeleton of granules and provide attachment points for bacterial colonization, and the expanded biomass layer in turn provided more area for the unstalked free-swimming zooids. Additionally, Epistylis spp. exerted much less predation stress on AnAOB than on nitrifying bacteria, and AnAOB tended to grow in aggregates in the interior of granules, thus favoring the growth and retention of AnAOB. Ultimately, the relative abundance of AnAOB reached up to a maximum of 8.2% in granules (doubling time of 9.9 d) compared to 1.1% in flocs (doubling time of 23.1 d), representing the most substantial disparity between granules and flocs. Overall, our findings advance the current understanding of interactions involved in granulation between protozoa and microbial communities and offer new insight into the specific enrichment of AnAOB under the novel granulation model.

How to Provide Nitrite Robustly for Anaerobic Ammonium Oxidation in Mainstream Nitrogen Removal.

Innovation in decarbonizing wastewater treatment is urgent in response to global climate change. The practical implementation of anaerobic ammonium oxidation (anammox) treating domestic wastewater is the key to reconciling carbon-neutral management of wastewater treatment with sustainable development. Nitrite availability is the prerequisite of the anammox reaction, but how to achieve robust nitrite supply and accumulation for mainstream systems remains elusive. This work presents a state-of-the-art review on the recent advances in nitrite supply for mainstream anammox, paying special attention to available pathways (forward-going (from ammonium to nitrite) and backward-going (from nitrate to nitrite)), key controlling strategies, and physiological and ecological characteristics of functional microorganisms involved in nitrite supply. First, we comprehensively assessed the mainstream nitrite-oxidizing bacteria control methods, outlining that these technologies are transitioning to technologies possessing multiple selective pressures (such as intermittent aeration and membrane-aerated biological reactor), integrating side stream treatment (such as free ammonia/free nitrous acid suppression in recirculated sludge treatment), and maintaining high activity of ammonia-oxidizing bacteria and anammox bacteria for competing oxygen and nitrite with nitrite-oxidizing bacteria. We then highlight emerging strategies of nitrite supply, including the nitrite production driven by novel ammonia-oxidizing microbes (ammonia-oxidizing archaea and complete ammonia oxidation bacteria) and nitrate reduction pathways (partial denitrification and nitrate-dependent anaerobic methane oxidation). The resources requirement of different mainstream nitrite supply pathways is analyzed, and a hybrid nitrite supply pathway by combining partial nitrification and nitrate reduction is encouraged. Moreover, data-driven modeling of a mainstream nitrite supply process as well as proactive microbiome management is proposed in the hope of achieving mainstream nitrite supply in practical application. Finally, the existing challenges and further perspectives are highlighted, i.e., investigation of nitrite-supplying bacteria, the scaling-up of hybrid nitrite supply technologies from laboratory to practical implementation under real conditions, and the data-driven management for the stable performance of mainstream nitrite supply. The fundamental insights in this review aim to inspire and advance our understanding about how to provide nitrite robustly for mainstream anammox and shed light on important obstacles warranting further settlement.

Carbon-Restricted Anoxic Zone as an Overlooked Anammox Hotspot in Municipal Wastewater Treatment Plants.

The anoxic zone serves as the core functional unit in municipal wastewater treatment plants (MWWTPs). Unfortunately, in most cases, the downstream range of the anoxic zone is severely lacking in available organic carbon and thus contributes little to the removal of nutrients. This undesirable range is termed the "carbon-restricted anoxic zone", representing an insurmountable drawback for traditional MWWTPs. This study uncovers a previously overlooked role for the carbon-restricted anoxic zone: a hotspot for anaerobic ammonium oxidation (anammox). In a continuous-flow pilot-scale plant treating municipal wastewater (55 m3/d), virgin biocarriers were introduced into the carbon-restricted anoxic zone (downstream 25% of the anoxic zone with BOD5 of 5.9 ± 2.3 mg/L). During the 517-day monitoring, anammox bacteria highly self-enriched within the biofilms, with absolute and relative abundance reaching up to (9.4 ± 0.1) × 109 copies/g-VSS and 6.17% (Candidatus Brocadia), respectively. 15N isotopic tracing confirmed that anammox overwhelmingly dominated nitrogen metabolism, responsible for 92.5% of nitrogen removal. Following this upgrade, the contribution ratio of the carbon-restricted anoxic zone to total nitrogen removal increased from 9.2 ± 4.1% to 19.2 ± 4.2% (P < 0.001), while its N2O emission flux decreased by 84.5% (P < 0.001). These findings challenge stereotypes about the carbon-restricted anoxic zone and highlight the multiple environmental implications of this newfound anammox hotspot.

Combination of sulfide-driven partial denitrification with anammox enhanced by zeolite powder for autotrophic nitrogen and sulfide removal from wastewater.

Sulfide-driven partial denitrification and anaerobic ammonia oxidizing (anammox) (SPDA) is a high-efficiency technology to achieve simultaneous nitrogen and sulfide removal. Nitrite accumulation from sulfide-driven partial denitrification is the key to achieve SPDA. Zeolite powder was added to strengthen the competition of anammox bacteria against nitrite. The nitrogen removal rate (NRR) and partial denitrification efficiency in reactor was 5.18 kg-N m-3d-1 and 92.3% during 180 days of operation, higher than those without zeolite powder, indicating an improving contribution of zeolite powder. Metabolomics analysis revealed zeolite powder addition enhanced the metabolisms of amino acids, nicotinate and porphyrin through increasing glutamate content, and improved EPS secretion, heme c content and particle size. Besides, high ammonia enriched by zeolite powder was conducive to improve anammox activity and NRR. This study provides the metabolic insights into the mechanism of zeolite powder enhancing SPDA, which is meaningful towards overcoming the limitations in practical application of SDPA.

Simultaneous nitrogen and sulfur removal through synergy of sulfammox, anammox and sulfur-driven autotrophic denitrification in a modified bioreactor enhanced by activated carbon.

Anaerobic ammonium (NH4+ - N) oxidation coupled with sulfate (SO42-) reduction (sulfammox) is a new pathway for the autotrophic removal of nitrogen and sulfur from wastewater. Sulfammox was achieved in a modified up-flow anaerobic bioreactor filled with granular activated carbon. After 70 days of operation, the NH4+ - N removal efficiency almost reached 70%, with activated carbon adsorption and biological reaction accounting for 26% and 74%, respectively. Ammonium hydrosulfide (NH4SH) was found in sulfammox by X-ray diffraction analysis for the first time, which confirmed that hydrogen sulfide (H2S) was one of the sulfammox products. Microbial results indicated that NH4+ - N oxidation and SO42- reduction in sulfammox were carried out by Crenothrix and Desulfobacterota, respectively, in which activated carbon may operate as electron shuttle. In the 15NH4+ labeled experiment, 30N2 were produced at a rate of 34.14 µmol/(g sludge·h) and no 30N2 was detected in the chemical control group, proving that sulfammox was present and could only be induced by microorganisms. The 15NO3- labeled group produced 30N2 at a rate of 88.77 µmol/(g sludge·h), demonstrating the presence of sulfur-driven autotrophic denitrification. In the adding 14NH4+ and 15NO3- group, it was confirmed that NH4+ - N was removed by the synergy of sulfammox, anammox and sulfur-driven autotrophic denitrification, where the main product of sulfammox was nitrite (NO2-) and anammox was the main cause of nitrogen loss. The findings showed that SO42- as a non-polluting species to environment may substitute NO2- to create a new "anammox" process.

Nitrite accumulation in activated sludge through cyclic anaerobic exposure with acetate.

Achieving nitrite accumulation still remains challenging for efficient short-cut biological nitrogen removal in municipal wastewater treatment. To tackle the problem of insufficient carbon in incoming wastewater for biological nutrient removal, a return activated sludge (RAS) fermentation method has been proposed and demonstrated to enable producing supplemental volatile fatty acids (VFAs) and enhance biological phosphorus removal via sludge cycling between mainstream and a sidestream anaerobic reactor. However, the impacts of long anaerobic exposure with acetate on nitrifying bacteria, known as the aerobic chemoautotrophic microorganisms, remains unexplored. In this study, the activated sludge underwent a cyclic anaerobic treatment with the addition of acetate (Ac), the effects on nitrification rate, abundance and microdiversity of nitrifying communities were comprehensively assessed. Firstly, batch activity tests proved the direct addition of high acetate (above 1000 mg/L) could cause inhibition on the nitrification rate, moreover, the inhibitory effect was stronger on nitrite-oxidizing bacteria (NOB) activity than that of ammonia-oxidizing bacteria (AOB). Then, a sequencing batch reactor (SBR) was applied to test the nitrogen conversion performance for low-strength ammonium wastewater. Nitrite accumulation could be achieved via the cyclic anaerobic exposure with 1000-5000 mg Ac/L. The maximum effluent concentration of nitrite was 40.8 ± 3.5 mg N/L with nitrite accumulation ratio (NAR) of 67.6 ± 3.5%. The decrease in NOB activity (72.7%) was greater than AOB of 42.4%, promoting nitrite accumulation via nitritation process. Furthermore, the cyclic anaerobic exposure with acetate can largely reshape the nitrifying communities. As the dominant AOB and NOB, the abundance of Nitrosomonas and Nitrospira were both decreased with species-level microdiversity in the nitrifying communities. However, the heterotrophic microorganism, Thauera, were found to be highly enriched (from 0 to 17.3%), which may act as the potential nitrite producer as proved by the increased nitrate reduction gene abundance. This study can provide new insights into achieving mainstream nitrite accumulation by involving sidestream RAS fermentation towards efficient wastewater treatment management.

Linking morphological features to anammox communities in a partial nitritation and anammox (PN/A) biofilm reactor.

Partial nitritation/anammox (PN/A) has been recognized as a cost-efficient process for wastewater nitrogen removal. The addition of carriers could help achieve biomass retention and enhance the treatment efficiency by forming the dense biofilm. However, accurately determining the abundance of anammox bacteria (AnAOB) to evaluate the biofilm development still remains challenging in practice without access to specialized facilities and experimental skills. In this study, we explored the feasibility of utilizing the morphological features of anammox biofilm as an indication of the biofilm development progression, and its correlation with microbial communities was also revealed. The time-series biofilms from an integrated fixed-film activated sludge (IFAS) system with stable PN/A performance were sampled representing the different biofilm development stages. The biofilm morphological features including color and texture were respectively quantified by red (R) coordinate and Local binary pattern (LBP) descriptor via image processing. Hierarchy clustering analysis proved that the extracted morphological descriptors could well distinguish the different stages (colonization, succession, and maturation) of biofilm development. The microbial community dynamics of time-series anammox biofilms were investigated using the amplicon sequence variant (ASV) analysis. Candidatus Brocadia, as the typical AnAOB, dominated in the whole communities of 16.3%-20.0%, moreover, the biofilm development was found to be driven by distinct Brocadia species. Linear regression evidenced that the Brocadia abundance could be directly correlated to the value of R and LBP, and the total variation of microbial communities could be significantly explained by the morphological features via redundancy analysis. This study demonstrates a new way to monitor the biofilm development by extracting the visible features of anammox aggregates, which can help facilitate the automated control of anammox-based bioprocess.

Robust and high-efficient nitrogen removal from real sewage and waste activated sludge (WAS) reduction in zero-external carbon PN/A combined with in-situ fermentation-denitrification process under decreased temperatures.

Despite the advantages of the combined anammox and fermentation-driven denitrification process in nitrogen removal and energy consumption, stable performance at decreased temperatures remains a challenge. In this study, a robust and high-efficient nitrogen removal efficiency (95.0-93.1 âˆ¼ 86.8-93.4%) with desirable effluent quality (3.0-4.1 âˆ¼ 7.9-4.9 mg/L) under long-term decreased temperatures (30 °C→25 °C→20 °C) was achieved in a zero-external carbon Partial Nitritation/Anammox combined with in-situ sludge Fermentation-Denitrification process treating sewage. Excellent sludge reduction averaged at 14.9% assuming no microbial growth. Increased hzsB mRNA (2.2-fold) and reduced Ea (80.9 kJ/mol) proved resilient anammox to lower temperature. RT-qPCR tests revealed increased NarG/NirK (5.1) and NarG/NirS (4.9) mRNA at 20 °C, suggesting higher NO3-→NO2- over NO2-→N2 pathway. Metagenomics unraveled dominant anammox bacteria (Candidatus_Brocadia, 2.27%), increased denitritation bacteria containing more NarG (Hyphomicrobium, 0.8%), fatty acid biosynthesis and CAZymes genes. Enhanced denitritation with recovered organics from sludge reserved nitrite for anammox and facilitated higher anammox contribution to N removal at 20 °C (42.4%) than 30 °C (39.5%). This study proposed an innovative low-temperature strategy for in-situ sludge fermentation, and demonstrated stability of advanced municipal wastewater treatment and sludge disposal through energy savings and carbon recovery under decreased temperatures.

Anammox granule destruction and reconstruction in a partial nitrification/anammox system under hydroxylamine stress.

Nitrite oxidizing bacteria (NOB) outcompeting anammox bacteria (AnAOB) poses a challenge to the practical implementation of the partial nitrification/anammox (PN/A) process for municipal wastewater. A granules-based PN/A bioreactor was operated for 260 d with hydroxylamine (NH2OH) added halfway through. qPCR results detected the different amounts of NOB among granules and flocs and the dynamic succession during operation. CLSM images revealed a unique layered structure of granules that NOB located inside led to the inhibition effect of NH2OH delayed. Besides, the physical and morphological characteristics revealed that anammox granules experienced destruction. AnAOB took the broken granules as an initial biofilm aggregate to reconstruct new granules. RT-qPCR and high throughput sequencing results suggested that functional gene expression and community structure were regulated for the AnAOB metabolism process. Correspondingly, the rapid proliferation (0.52 â†’ 1.99%) of AnAOB was realized, and the nitrogen removal rate achieved a nearly quadruple improvement (0.21 â†’ 0.83 kg-N/m3·d). This study revealed that anammox granules can self-reconstruct in the PN/A system when granules are disintegrated under NH2OH stress, broadening the feasibility of applying PN/A process.