Inorganic bioelectric system for nitrate removal with low NO production at cold temperatures of 4 and 10 °C.

Groundwater, essential for ecological stability and freshwater supply, faces escalating nitrate contamination. Traditional biological methods struggle with organic carbon scarcity and low temperatures, leading to an urgent need to explore efficient approaches for groundwater remediation. In this work, we proposed an inorganic bioelectric system designed to confront these challenges.

Formation and Fate of Reactive Nitrogen during Biological Nitrogen Removal from Water: Important Yet Often Ignored Chemical Aspects of the Nitrogen Cycle.

Hydroxylamine, nitrous acid, and nitric oxide are obligate intermediates or side metabolites in different nitrogen-converting microorganisms. These compounds are unstable and susceptible to the formation of highly reactive nitrogen species, including nitrogen dioxide, dinitrogen trioxide, nitroxyl, and peroxynitrite. Due to the high reactivity and cytotoxicity, the buildup of reactive nitrogen can affect the interplay of microorganisms/microbial processes, stimulate the reactions with organic compounds like organic micropollutants (OMP) and act as the precursors of nitrous oxide (NO).

Corrigendum: Effect of oxic and anoxic conditions on intracellular storage of polyhydroxyalkanoate and polyphosphate in strain AMB-1.

[This corrects the article DOI: 10.3389/fmicb.2023.

Effect of oxic and anoxic conditions on intracellular storage of polyhydroxyalkanoate and polyphosphate in strain AMB-1.

Magnetotactic bacteria (MTB) are microorganisms widely inhabiting the oxic-anoxic interface of aquatic environments. Beside biomineralizing magnetic nanocrystals, MTBs are able to sequester various chemical elements (e.g.

Electrochemical disinfection may increase the spread of antibiotic resistance genes by promoting conjugal plasmid transfer.

Current in the milliampere range can be used for electrochemical inactivation of bacteria. Yet, bacteria-including antibiotic resistant bacteria (ARB) may be subjected to sublethal conditions due to imperfect mixing or energy savings measures during electrochemical disinfection. It is not known whether such sublethal current intensities have the potential to stimulate plasmid transfer from ARB.

Microbial bioremediation of produced water under different redox conditions in marine sediments.

The discharge of produced water from offshore oil platforms is an emerging concern due to its potential adverse effects on marine ecosystems. In this study, we investigated the feasibility and capability of using marine sediments for the bioremediation of produced water. We utilized a combination of porewater and solid phase analysis in a series of sediment batch incubations amended with produced water and synthetic produced water to determine the biodegradation of hydrocarbons under different redox conditions.

Role of Ammonia Oxidation in Organic Micropollutant Transformation during Wastewater Treatment: Insights from Molecular, Cellular, and Community Level Observations.

Organic micropollutants (OMPs) are a threat to aquatic environments, and wastewater treatment plants may act as a source or a barrier of OMPs entering the environment. Understanding the fate of OMPs in wastewater treatment processes is needed to establish efficient OMP removal strategies. Enhanced OMP biotransformation has been documented during biological nitrogen removal and has been attributed to the cometabolic activity of ammonia-oxidizing bacteria (AOB) and, specifically, to the ammonia monooxygenase (AMO) enzyme.

Time to act-assessing variations in qPCR analyses in biological nitrogen removal with examples from partial nitritation/anammox systems.

Quantitative PCR (qPCR) is broadly used as the gold standard to quantify microbial community fractions in environmental microbiology and biotechnology. Benchmarking efforts to ensure the comparability of qPCR data for environmental bioprocesses are still scarce. Also, for partial nitritation/anammox (PN/A) systems systematic investigations are still missing, rendering meta-analysis of reported trends and generic insights potentially precarious.

The effect of pH on NO production in intermittently-fed nitritation reactors.

The effect of pH on nitrous oxide (NO) production rates was quantified in an intermittently-fed lab-scale sequencing batch reactor performing high-rate nitritation. NO and other nitrogen (N) species (e.g.

Abiotic Nitrous Oxide (NO) Production Is Strongly pH Dependent, but Contributes Little to Overall NO Emissions in Biological Nitrogen Removal Systems.

Hydroxylamine (NHOH) and nitrite (NO), intermediates during the nitritation process, can engage in chemical (abiotic) reactions that lead to nitrous oxide (NO) generation. Here, we quantify the kinetics and stoichiometry of the relevant abiotic reactions in a series of batch tests under different and relevant conditions, including pH, absence/presence of oxygen, and reactant concentrations. The highest NO production rates were measured from NHOH reaction with HNO, followed by HNO reduction by Fe, NHOH oxidation by Fe, and finally NHOH disproportionation plus oxidation by O.

Reactor staging influences microbial community composition and diversity of denitrifying MBBRs- Implications on pharmaceutical removal.

The subdivision of biofilm reactor in two or more stages (i.e., reactor staging) represents an option for process optimisation of biological treatment.

The pH dependency of N-converting enzymatic processes, pathways and microbes: effect on net N O production.

Nitrous oxide (N O) is emitted during microbiological nitrogen (N) conversion processes, when N O production exceeds N O consumption. The magnitude of N O production vs. consumption varies with pH and controlling net N O production might be feasible by choice of system pH.

Low nitrous oxide production through nitrifier-denitrification in intermittent-feed high-rate nitritation reactors.

Nitrous oxide (NO) production from autotrophic nitrogen conversion processes, especially nitritation systems, can be significant, requires understanding and calls for mitigation. In this study, the rates and pathways of NO production were quantified in two lab-scale sequencing batch reactors operated with intermittent feeding and demonstrating long-term and high-rate nitritation. The resulting reactor biomass was highly enriched in ammonia-oxidizing bacteria, and converted ∼93 ± 14% of the oxidized ammonium to nitrite.

Pathways and Controls of NO Production in Nitritation-Anammox Biomass.

Nitrous oxide (NO) is an unwanted byproduct during biological nitrogen removal processes in wastewater. To establish strategies for NO mitigation, a better understanding of production mechanisms and their controls is required. A novel stable isotope labeling approach using N and O was applied to investigate pathways and controls of NO production by biomass taken from a full-scale nitritation-anammox reactor.

Heterotrophs are key contributors to nitrous oxide production in activated sludge under low C-to-N ratios during nitrification-Batch experiments and modeling.

Nitrous oxide (N O), a by-product of biological nitrogen removal during wastewater treatment, is produced by ammonia-oxidizing bacteria (AOB) and heterotrophic denitrifying bacteria (HB). Mathematical models are used to predict N O emissions, often including AOB as the main N O producer. Several model structures have been proposed without consensus calibration procedures.

Aerobic Microbial Respiration In Oceanic Oxygen Minimum Zones.

Oxygen minimum zones are major sites of fixed nitrogen loss in the ocean. Recent studies have highlighted the importance of anaerobic ammonium oxidation, anammox, in pelagic nitrogen removal. Sources of ammonium for the anammox reaction, however, remain controversial, as heterotrophic denitrification and alternative anaerobic pathways of organic matter remineralization cannot account for the ammonium requirements of reported anammox rates.

Aeration strategies to mitigate nitrous oxide emissions from single-stage nitritation/anammox reactors.

Autotrophic nitrogen removal is regarded as a resource efficient process to manage nitrogen-rich residual streams. However, nitrous oxide emissions of these processes are poorly documented and strategies to mitigate emissions unknown. In this study, two sequencing batch reactors performing single-stage nitritation/anammox were operated under different aeration strategies, gradually adjusted over six months.

Oxygen sensitivity of anammox and coupled N-cycle processes in oxygen minimum zones.

Nutrient measurements indicate that 30-50% of the total nitrogen (N) loss in the ocean occurs in oxygen minimum zones (OMZs). This pelagic N-removal takes place within only ~0.1% of the ocean volume, hence moderate variations in the extent of OMZs due to global warming may have a large impact on the global N-cycle.

Nitrite oxidation in the Namibian oxygen minimum zone.

Nitrite oxidation is the second step of nitrification. It is the primary source of oceanic nitrate, the predominant form of bioavailable nitrogen in the ocean. Despite its obvious importance, nitrite oxidation has rarely been investigated in marine settings.

Intensive nitrogen loss over the Omani Shelf due to anammox coupled with dissimilatory nitrite reduction to ammonium.

A combination of stable isotopes ((15)N) and molecular ecological approaches was used to investigate the vertical distribution and mechanisms of biological N(2) production along a transect from the Omani coast to the central-northeastern (NE) Arabian Sea. The Arabian Sea harbors the thickest oxygen minimum zone (OMZ) in the world's oceans, and is considered to be a major site of oceanic nitrogen (N) loss. Short (<48 h) anoxic incubations with (15)N-labeled substrates and functional gene expression analyses showed that the anammox process was highly active, whereas denitrification was hardly detectable in the OMZ over the Omani shelf at least at the time of our sampling.

15N-labeling experiments to dissect the contributions of heterotrophic denitrification and anammox to nitrogen removal in the OMZ waters of the ocean.

In recent years, (15)N-labeling experiments have become a powerful tool investigating rates and regulations of microbially mediated nitrogen loss processes in the ocean. This chapter introduces the theoretical and practical aspects of (15)N-labeling experiments to dissect the contribution of denitrification and anammox to nitrogen removal in oxygen minimum zones (OMZs). We provide a detailed description of the preparation and realization of the experiments on board.

Aerobic denitrification in permeable Wadden Sea sediments.

Permeable or sandy sediments cover the majority of the seafloor on continental shelves worldwide, but little is known about their role in the coastal nitrogen cycle. We investigated the rates and controls of nitrogen loss at a sand flat (Janssand) in the central German Wadden Sea using multiple experimental approaches, including the nitrogen isotope pairing technique in intact core incubations, slurry incubations, a flow-through stirred retention reactor and microsensor measurements. Results indicate that permeable Janssand sediments are characterized by some of the highest potential denitrification rates (> or =0.

Revising the nitrogen cycle in the Peruvian oxygen minimum zone.

The oxygen minimum zone (OMZ) of the Eastern Tropical South Pacific (ETSP) is 1 of the 3 major regions in the world where oceanic nitrogen is lost in the pelagic realm. The recent identification of anammox, instead of denitrification, as the likely prevalent pathway for nitrogen loss in this OMZ raises strong questions about our understanding of nitrogen cycling and organic matter remineralization in these waters. Without detectable denitrification, it is unclear how NH(4)(+) is remineralized from organic matter and sustains anammox or how secondary NO(2)(-) maxima arise within the OMZ.

Linking crenarchaeal and bacterial nitrification to anammox in the Black Sea.

Active expression of putative ammonia monooxygenase gene subunit A (amoA) of marine group I Crenarchaeota has been detected in the Black Sea water column. It reached its maximum, as quantified by reverse-transcription quantitative PCR, exactly at the nitrate maximum or the nitrification zone modeled in the lower oxic zone. Crenarchaeal amoA expression could explain 74.