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Removal of iron(II) from groundwater by aeration and rapid sand filtration (RSF) with the accompanying production of drinking water sludge in the preparation of drinking water from groundwater, and chemical well clogging by accumulation of hydrous ferric oxide (HFO) precipitates and biomass after mixing of oxygen containing and of iron(II) containing groundwater, are identical processes. Iron(II) may precipitate from (ground)water by homogeneous, heterogeneous and/or biological oxidation, where the contribution of these processes, and thus the characteristics of the corresponding HFO precipitates, is a function of pH and process-conditions. Under current conditions in drinking water treatment, homogeneous oxidation dominates above pH ≈ 7.75, and heterogeneous and biological oxidation below this value. In chemical well clogging, this transition occurs at pH ≈ 7.0. This information is relevant for the optimization of removal of iron(II) from groundwater by aeration and RSF and the corresponding quality of the produced drinking water sludge, and for the operation of wells clogging by accumulation of HFO precipitates and biomass.

Abstract Semi-passive bioreactors based on iron and arsenic oxidation and coprecipitation are promising for the treatment of As-rich acid mine drainages. However, their performance in the field remains variable and unpredictable. Two bioreactors filled with distinct biomass carriers (plastic or a mix of wood and pozzolana) were monitored during 1 year. We characterized the dynamic of the bacterial communities in these bioreactors, and explored the influence of environmental and operational drivers on their diversity and activity. Bacterial diversity was analyzed by 16S rRNA gene metabarcoding. The aioA genes and transcripts were quantified by qPCR and RT-qPCR. Bacterial communities were dominated by several iron-oxidizing genera. Shifts in the communities were attributed to operational and physiochemical parameters including the nature of the biomass carrier, the water pH, temperature, arsenic, and iron concentrations. The bioreactor filled with wood and pozzolana showed a better resilience to disturbances, related to a higher bacterial alpha diversity. We evidenced for the first time aioA expression in a treatment system, associated with the presence of active Thiomonas spp. This confirmed the contribution of biological arsenite oxidation to arsenic removal. The resilience and the functional redundancy of the communities developed in the bioreactors conferred robustness and stability to the treatment systems. The resilience and functional redundancy of bacterial communities conferred robustness and stability to iron oxidizing bioreactors treating arsenic-rich acid mine drainages.

FOXP3+ Tregs rely on fatty acid β-oxidation-driven (FAO-driven) oxidative phosphorylation (OXPHOS) for differentiation and function. Recent data demonstrate a role for Tregs in the maintenance of tissue homeostasis, with tissue-resident Tregs possessing tissue-specific transcriptomes. However, specific signals that establish tissue-resident Treg programs remain largely unknown. Tregs metabolically rely on FAO, and considering the lipid-rich environments of tissues, we hypothesized that environmental lipids drive Treg homeostasis. First, using human adipose tissue to model tissue residency, we identified oleic acid as the most prevalent free fatty acid. Mechanistically, oleic acid amplified Treg FAO-driven OXPHOS metabolism, creating a positive feedback mechanism that increased the expression of FOXP3 and phosphorylation of STAT5, which enhanced Treg-suppressive function. Comparing the transcriptomic program induced by oleic acid with proinflammatory arachidonic acid, we found that Tregs sorted from peripheral blood and adipose tissue of healthy donors transcriptomically resembled the Tregs treated in vitro with oleic acid, whereas Tregs from patients with multiple sclerosis (MS) more closely resembled an arachidonic acid transcriptomic profile. Finally, we found that oleic acid concentrations were reduced in patients with MS and that exposure of MS Tregs to oleic acid restored defects in their suppressive function. These data demonstrate the importance of fatty acids in regulating tissue inflammatory signals.

In this paper, the abatement of adsorbable halogenated organic compounds (AOX) from an industrial wastewater containing relatively high chloride concentrations by a combined chemical and biological oxidation is assessed. For chemical oxidation, the O3/UV, H2O2/UV and photo-Fenton processes are evaluated on pilot scale. Biological oxidation is simulated in a 4 h respirometry experiment with periodic aeration. The results show that a selective degradation of AOX with respect to the matrix compounds (expressed as chemical oxygen demand) could be achieved. For O3/UV, lowering the ratio of O3 dosage to UV intensity leads to a better selectivity for AOX. During O3-based experiments, the AOX removal is generally less than during the H2O2-based experiments. However, after biological oxidation, the AOX levels are comparable. For H2O2/UV, optimal operating parameters for UV and H2O2 dosage are next determined in a second run with another wastewater sample.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the gradual loss of midbrain dopaminergic neurons in association with aggregation of α-synuclein. Oxidative damage has been widely implicated in this disease, though the mechanisms involved remain elusive. Here, we demonstrated that preferential accumulation of peroxidized phospholipids and loss of the antioxidant enzyme glutathione peroxidase 4 (GPX4) were responsible for vulnerability of midbrain dopaminergic neurons and progressive motor dysfunctions in a mouse model of PD. We also established a mechanism wherein iron-induced dopamine oxidation modified GPX4, thereby rendering it amenable to degradation via the ubiquitin-proteasome pathway. In conclusion, this study unraveled what we believe to be a novel pathway for dopaminergic neuron degeneration during PD pathogenesis, driven by dopamine-induced loss of antioxidant GPX4 activity.

Both the consumption of a diet rich in fatty acids and exercise training result in similar adaptations in several skeletal muscle proteins. These adaptations are involved in fatty acid uptake and activation within the myocyte, the mitochondrial import of fatty acids and further metabolism of fatty acids by β-oxidation. Fatty acid availability is repeatedly increased postprandially during the day, particularly during high dietary fat intake and also increases during, and after, aerobic exercise. As such, fatty acids are possible signalling candidates that regulate transcription of target genes encoding proteins involved in muscle lipid metabolism. The mechanism of signalling might be direct or indirect targeting of peroxisome proliferator-activated receptors by fatty acid ligands, by fatty acid-induced NAD+-stimulated activation of sirtuin 1 and/or fatty acid-mediated activation of AMP-activated protein kinase. Lactate might also have a role in lipid metabolic adaptations. Obesity is characterized by impairments in fatty acid oxidation capacity, and individuals with obesity show some rigidity in increasing fatty acid oxidation in response to high fat intake. However, individuals with obesity retain improvements in fatty acid oxidation capacity in response to exercise training, thereby highlighting exercise training as a potential method to improve lipid metabolic flexibility in obesity.This Review summarizes the adaptations to lipid metabolism that occur in skeletal muscle in response to either a high-fat diet or exercise training. In addition, obesity-associated impairments in fatty acid oxidation capacity and the importance of exercise for overcoming lipid metabolic inflexibility in obesity are discussed.

The vast majority of the research into cancer metabolism has been limited to a handful of metabolic pathways, with other pathways being sidelined. This Progress article brings to light the potential contribution of fatty acid oxidation to cancer cell function. Warburg suggested that the alterations in metabolism that he observed in cancer cells were due to the malfunction of mitochondria. In the past decade, we have revisited this idea and reached a better understanding of the 'metabolic switch' in cancer cells, including the intimate and causal relationship between cancer genes and metabolic alterations, and their potential to be targeted for cancer treatment. However, the vast majority of the research into cancer metabolism has been limited to a handful of metabolic pathways, while other pathways have remained in the dark. This Progress article brings to light the important contribution of fatty acid oxidation to cancer cell function.

In groundwater treatment, after aeration, iron(II) is precipitated in rapid sand filtration (RSF) by homogeneous, heterogeneous and biological oxidation. The contribution of homogeneous iron(II) oxidation may be calculated from equations and constants available in the literature. Heterogeneous iron(II) oxidation produces hydrous ferric oxides coated filter sand, resulting in a growing filter bed height, from which the contribution of heterogeneous iron(II) oxidation may be estimated. The complement is contributed by biological iron(II) oxidation. At present this contribution may also be estimated by Gallionella spp. counts by quantitative real-time polymerase chain reaction. Based on field data of drinking water treatment plants from the Netherlands and Belgium, it appears that at pH ≈ 7.5 biological iron(II) oxidation is the main iron(II) removal process. At higher pH homogeneous iron(II) oxidation becomes dominant, while at lower pH heterogeneous iron(II) oxidation delivers a relevant contribution. The distribution of these oxidation processes is influenced by RSF operation such as presence of supernatant water, wet or dry (trickle) filtration, oxygen concentration, filter velocity, etc. Experience shows that the distribution between these three iron(II) oxidation processes may change over time. These results are important for RSF operation, iron sludge production, and fields like chemical well clogging.

Two semi-passive treatment systems for iron (Fe) and arsenic (As) removal in AMD were installed and monitored in-situ for more than a year. These technologies were designed to treat the As-enriched AMD (≈ 1 g/L Fe(II) and 100 mg/L As(III)) of the ancient Carnoulès mine. The treatment was based on biological Fe and As oxidation by indigenous bacteria, and subsequent immobilization of As by ferric hydroxysulfates. Forced aeration and wood/pozzolana or plastic support were used for biofilm attachment. The system performance ranged from 86 to 98% for Fe oxidation, 30 to 60% for Fe removal, and 50 to 80% for As removal at a hydraulic retention time of 9 h. No significant difference were measured between the two biofilm supports. The wood/pozzolana support had a shorter delay for performance recovery after interruptions. Iron oxidation rates were similar to those obtained in the Carnoulès AMD stream and laboratory bioreactor, while As oxidation seemed to be enhanced. The sludge accumulated between 39 and 91 mg/g of As, mainly in the As(V) oxidation state; jarosite and amorphous ferric hydroxysulfate phases were the main Fe and As scavengers. Challenging environmental conditions during the long monitoring period confirm the robustness of the treatment units. The data will be useful in designing future full-scale treatment systems adapted to As-rich AMD.

Reactive oxygen species (ROS) are increasingly appreciated as down-stream effectors of cellular damage and dysfunction under natural and anthropogenic stress scenarios in aquatic systems. This comprehensive volume describes oxidative stress phenomena in different climatic zones and groups of organisms, taking into account specific habitat conditions and how they affect susceptibility to ROS damage. A comprehensive and detailed methods section is included which supplies complete protocols for analyzing ROS production, oxidative damage, and antioxidant systems. Methods are also evaluated with respect to applicability and constraints for different types of research. The authors are all internationally recognized experts in particular fields of oxidative stress research. This comprehensive reference volume is essential for students, researchers, and technicians in the field of ROS research, and also contains information useful for veterinarians, environmental health professionals, and decision makers.