Successful mainstream nitritation through NOB inactivation

The development of new wastewater treatment processes can assist in reducing the impact of wastewater treatment on the environment. The recently developed partial nitritation anammox (PNA) process, for example, consumes less energy for aeration and reduces nitrate in the effluent without requiring additional organic carbon. However, achieving stable nitritation (ammonium oxidation; NH₄⁺ → NO₂^-) at mainstream conditions (T = 10-25 °C, C:N > 10, influent ammonium < 50 mgNH₄-N/L and effluent < 1 mgNH₄-N/L) remains challenging. This study explores the potential and mechanism of nitrite-oxidizing bacteria (NOB) suppression in a bottom-fed sequencing batch reactor (SBR). Two bench-scale (11 L) reactors and a pilot-scale reactor (8 m³) were operated for over a year and were fed with organic substrate depleted municipal wastewater. Initially, nitratation (nitrite oxidation; NO₂^- → NO₃^-) occurred occasionally until an anaerobic phase was integrated into the operating cycle. The introduction of the anaerobic phase effectively suppressed the regrowth of NOB while nitritation was stable over 300 days, down to 8 °C and at ammonium influent concentrations < 25 mgNH₄-N/L. Batch experiments and process data revealed that parameters typically affecting NOB growth (e.g., dissolved oxygen, alkalinity, trace elements, lag-phase after anoxia, free nitrous acid (FNA), free ammonia (FA), pH, sulfide, or solids retention time (SRT)) could not fully explain the suppression of nitratation. Experiments in which fresh nitrifying microbial biomass was added to the nitritation system indicated that NOB inactivation explained NOB suppression better than NOB washout at high SRT. This study concludes that bottom-fed SBRs with anaerobic phases allow for stable nitritation over a broad range of operational parameters. Coupling this type of SBR to an anammox reactor can enable efficient mainstream anammox-based wastewater treatment.

Carotid intima media thickness measurements coupled with stroke severity strongly predict short-term outcome in patients with acute ischemic stroke: a machine learning study

Acute ischemic stroke (IS) is one of the leading causes of morbidity, functional disability and mortality worldwide. The objective was to evaluate IS risk factors and imaging variables as predictors of short-term disability and mortality in IS. Consecutive 106 IS patients were enrolled. We examined the accuracy of IS severity using the National Institutes of Health Stroke Scale (NIHSS), carotid intima-media thickness (cIMT) and carotid stenosis (both assessed using ultrasonography with doppler) predicting IS outcome assessed with the modified Rankin scale (mRS) three months after hospital admission. Poor prognosis (mRS ≥ 3) at three months was predicted by carotid stenosis (≥ 50%), type 2 diabetes mellitus and NIHSS with an accuracy of 85.2% (sensitivity: 90.2%; specificity: 81.8%). The mRS score at three months was strongly predicted by NIHSS (β = 0.709, p < 0.001). Short-term mortality was strongly predicted using a neural network model with cIMT (≥ 1.0 mm versus < 1.0 mm), NIHSS and age, yielding an area under the receiving operator characteristic curve of 0.977 and an accuracy of 94.7% (sensitivity: 100.0%; specificity: 90.9%). High NIHSS (≥ 15) and cIMT (≥ 1.0 mm) increased the probability of dying with hazard ratios of 7.62 and 3.23, respectively. Baseline NIHSS was significantly predicted by the combined effects of age, large artery atherosclerosis stroke, sex, cIMT, body mass index, and smoking. In conclusion, high values of cIMT and NIHSS at admission strongly predict short-term functional impairment as well as mortality three months after IS, underscoring the importance of those measurements to predict clinical IS outcome.

Delayed nitrate dispersion within a coastal aquifer provides constraints on land-use evolution and nitrate contamination in the past

Identifying sources of anthropogenic pollution, and assessing the fate and residence time of pollutants in aquifers is important for the management of groundwater resources, and the ecological health of groundwater dependent ecosystems. This study investigates anthropogenic contamination in the shallow alluvial aquifer of the Marana-Casinca, hydraulically connected to the Biguglia lagoon (Corsica, France). A multi-tracer approach, combining geochemical and environmental isotopic data (δ¹⁸O-H₂O, δ²H-H₂O, ³H, δ¹⁵N-NO₃^-, δ¹⁸O-NO₃^-, δ¹¹B), and groundwater residence-time tracers (³H and CFCs) was carried out in 2016, and integrated with a study of land use evolution in the catchment during the last century. Groundwater NO₃^- concentrations, ranged between 2 mg/L and up to 30 mg/L, displaying the degradation of groundwater quality induced by anthropogenic activities (agricultural activities). Comparatively high δ¹⁵N-NO₃^- values (up to 19.7‰) in combination with δ¹¹B values that were significantly lower (between 23‰ and 26‰) than the seawater background are indicative of sewage contamination. The ongoing deterioration of groundwater quality can be attributed to the uncontrolled urbanization development all over the alluvial plain, with numerous sewage leakages from the sanitation network and private sewage systems. Integration of contaminant and water-residence time data revealed a progressive accumulation of pollutants with time in the groundwater, particularly in areas with major anthropogenic pressure and slow dynamic groundwater flow. Our approach provides time-dependent insight into nitrogen pollution in the studied aquifer over the past decades, revealing a systematic change in the dominant NO₃^- source, from agricultural to sewage contamination. Yet, today's low groundwater quality is to large parts due to legacy pollution from land-use practices several decades ago, underlining the poor self-remediating capacity of this hydrosystem. Our results can be taken as warning that groundwater pollution that happened in the recent past, or today, may have dire impacts on the quality of groundwater-dependent ecosystems in the future.

Vitamin D deficiency is associated with acute ischemic stroke, C-reactive protein, and short-term outcome

The aim of this study was to investigate whether vitamin D deficiency (VDD) is associated with acute ischemic stroke, inflammatory markers, and short-term outcome. 168 acute ischemic stroke patients and 118 controls were included. The modified Rankin Scale (mRS) was applied up to 8 h of admission (baseline) and after three-months follow-up, and blood samples were obtained up to 24 h of admission to evaluate serum levels of 25-hydroxivitamin D [25(OH)D] and inflammatory markers. Vitamin D levels classified the individuals in sufficient (VDS ≥ 30.0 ng/mL), insufficient (VDI 20.0-29.9 ng/mL), and deficient (VDD < 20.0 ng/mL) status. Patients had lower levels of 25(OH)D, higher frequency of VDD (43.45% vs. 5.08%, OR: 16.64, 95% CI: 5.66-42.92, p < 0.001), and higher inflammatory markers than controls (p < 0.05). Patients with VDD showed increased high sensitivity C-reactive protein (hsCRP) levels than those with VDS status (p = 0.043); those with poor outcome presented with lower 25(OH)D levels than those with good outcome (p = 0.008); moreover, 25(OH)D levels were negatively correlated with mRS after three-months follow-up (r = -0.239, p = 0.005). The associations between VDD and higher hsCRP levels and between 25(OH)D levels and poor outcome at short-term in acute ischemic stroke patients suggest the important role of vitamin D in the inflammatory response and pathophysiology of this ischemic event.

Isotopic constraints on water source mixing, network leakage and contamination in an urban groundwater system

Water supply in developing countries is prone to large water losses due to leaky distribution networks and defective sewers, which may affect groundwater quality and quantity in urban areas and result in complex subsurface mixing dynamics. In this study, a multi-stable isotope approach was used to investigate spatiotemporal fluctuations of surface and sub-surface water source partitioning and mixing, and to assess nitrogen (N) contamination in the urban water cycle of As-Salt, Jordan. Water import from the King Abdullah Canal (KAC), mains waters from the network, and wastewater are characterized by distinct isotopic signatures, which allowed us to quantify city effluents into the groundwater. Temporal variations in isotopic signatures of polluted groundwater are explained by seasonally fluctuating inflow, and dilution by water that originates from Lake Tiberias and enters the urban water cycle via the KAC. Isotopic analysis (N and O) and comparison between groundwater nitrate and nitrate from mains water, water imports and wastewater confirmed that septic waste from leaky sewers is the main contributor of nitrate contamination. The nitrate of strongly contaminated groundwater was characterized by highest δ¹⁵N_NO3 values (13.3±1.8‰), whereas lowest δ¹⁵N_NO3 values were measured in unpolluted groundwater (6.9‰). Analogously, nitrate concentration and isotopic ratios were used for source partitioning and qualitatively confirmed δD_H2O and δ¹⁸O_H2O-based estimates. Dual water isotope endmember mixing calculations suggest that city effluents from leaky networks and sewers contribute 30-64% to the heavily polluted groundwater. Ternary mixing calculations including also chloride revealed that 5-18% of the polluted groundwater is wastewater. Up to two thirds of the groundwater originates from mains, indicating excessive water loss from the network, and calling for improved water supply management.

Pulsatile tinnitus: a symptom of chronic subclavian artery occlusion

We report the unusual case of pulsatile tinnitus caused by muscular branches of the occipital artery, which developed to supply the distal vertebral artery after subclavian artery occlusion. Anatomical findings and options of endovascular treatment are discussed. To our knowledge, subclavian artery occlusion causing an objective tinnitus has not been reported.

A method for the extraction of ammonium from freshwaters for nitrogen isotope analysis

The measurement of delta15N values of inorganic nitrogen species is an important analytical tool to trace nitrogen species in order to understand nitrogen cycling in aquatic systems. Nitrogen isotope analysis of freshwater ammonium has, however, been hindered by the lack of a simple and reliable technique to measure delta15N values at natural abundance levels. We present a simple and rapid method to concentrate ammonium from freshwater samples for on-line N-isotope ratio determination. Ammonium is collected by adsorption on N-free cation exchange resins. The dried N-loaded exchange resin is then directly combusted to produce N2 gas for subsequent delta15N analysis. The method was evaluated with simulated freshwater solutions containing varying amounts of standard NH4+-N (delta15N = 2.1 per thousand) and potentially interfering inorganic and organic compounds. In general, the cation exchange resin method gives accurate and reproducible delta15N values (sigma1 < 0.3 per thousand; n = 10). Because of adsorption interference, high concentrations of cations in solution may cause ammonium loss but do not result in measurable isotope fractionation. Replicate extractions of the ammonium standard added to water collected from four Swiss lakes demonstrate the good performance of this method when applied to low ionic strength natural water samples with modest concentrations of dissolved organic nitrogen.