Low Ammonium Concentrations Research Articles

Rapid nitrification using nitrifying biomass acclimated to sulfamethoxazole (SMX)

Antibiotics often are input to biological-treatment systems for domestic sewage, and they can inhibit nitrifying bacteria and impair nitrification performance. In this work, activated sludge was acclimated to either a high or a low ammonium concentration in the continuous presence of 10 mg/L the antibiotic sulfamethoxazole (SMX). The high ammonium concentration led to nitrifying activated sludge (NAS), while the low ammonium concentration led to conventional activated sludge (CAS). After acclimation, the NH4+-removal rate for NAS was 8-fold greater than the rate for CAS when 10 mg/L SMX also was present in the medium. NAS also biotransformed SMX faster than did CAS. The removal kinetics for NH4+ and SMX were well represented by the Aiba self-inhibition model: The NAS biomass had a much faster maximum removal rate for NH4+, and it had better affinity for NH4+ and less inhibition from SMX. The NAS biomass also had faster biotransformation kinetics for SMX, with the main impact being a much faster maximum specific biotransformation rate (rmax). Analysis of microbiological community documented that the NAS biomass was enriched in nitrifying bacteria and also had more heterotrophic bacteria likely to be able to biotransform SMX.

Highly sensitive graphene-based ammonia sensor enhanced by electrophoretic deposition of MXene

Herein, we reported a gas sensor based on MXene/Graphene composite sensitive film for low-concentration ammonia detection. Specifically, we use the electrophoretic deposition method to uniformly deposit MXene on the graphene film surface of the graphene sensor, thereby constructing the MXene/Graphene composite sensitive film. The ammonia sensitivity test results show that the MXene/Graphene composite film sensor exhibits fast response, high sensitivity and excellent selectivity to ammonia at room temperature and high humidity. At the same test concentration (100 ppm), the sensitivity of the MXene/Graphene sensor is 3 times higher than that of the graphene sensor, 2 times higher than that of the MXene film sensor, reaching 25%, and its theoretical limit of detection is 56 ppb. The response time is only 26 s and the recovery time is 148 s, while the response time of the graphene sensor is 228 s. The MXene/Graphene sensitive film takes full advantage of the hydrophilicity and abundant surface functional groups of MXene, and the excellent electrical conductivity of graphene, which solves the problems of low sensitivity, slow response speed, and inability to completely desorb ammonia gas of pure MXene or graphene. Potential applications in designing next-generation portable gas sensors for human breath detection analysis.

Potential of montmorillonite modified by an organosulfur surfactant for reducing aflatoxin B1 toxicity and ruminal methanogenesis in vitro

BackgroundMontmorillonite clay modified by organosulfur surfactants possesses high cation exchange capacity (CEC) and adsorption capacity than their unmodified form (UM), therefore they may elevate the adverse impact of aflatoxin B1 (AFB1) on ruminal fermentation and methanogenesis. Chemical and mechanical modifications were used to innovate the organically modified nano montmorillonite (MNM). The UM was modified using sodium dodecyl sulfate (SDS) and grounded to obtain the nanoscale particle size form. The dose-response effects of the MNM supplementation to a basal diet contaminated or not with AFB1 (20 ppb) were evaluated in vitro using the gas production (GP) system. The following treatments were tested: control (basal diet without supplementations), UM diet [UM supplemented at 5000 mg /kg dry matter (DM)], and MNM diets at low (500 mg/ kg DM) and high doses (1000 mg/ kg DM).ResultsResults of the Fourier Transform Infra-Red Spectroscopy analysis showed shifts of bands of the OH-group occurred from lower frequencies to higher frequencies in MNM, also an extra band at the lower frequency range only appeared in MNM compared to UM. Increasing the dose of the MNM resulted in linear and quadratic decreasing effects (P < 0.05) on GP and pH values. Diets supplemented with the low dose of MNM either with or without AFB1 supplementation resulted in lower (P = 0.015) methane (CH4) production, ruminal pH (P = 0.002), and ammonia concentration (P = 0.002) compared to the control with AFB1. Neither the treatments nor the AFB1 addition affected the organic matter or natural detergent fiber degradability. Contamination of AFB1 reduced (P = 0.032) CH4 production, while increased (P < 0.05) the ruminal pH and ammonia concentrations. Quadratic increases (P = 0.012) in total short-chain fatty acids and propionate by MNM supplementations were observed.ConclusionThese results highlighted the positive effects of MNM on reducing the adverse effects of AFB1 contaminated diets with a recommended dose of 500 mg/ kg DM under the conditions of this study.

A randomized dietary intervention to increase colonic and peripheral blood SCFAs modulates the blood B- and T-cell compartments in healthy humans

SCFAs have immune-modulating effects in animal models of disease. However, there is limited evidence that this may occur in humans. This study aimed to determine the effects of increased exposure to SCFAs via dietary manipulation on colonic fermentation and adaptive immune cells. Twenty healthy young adults (18-45 y of age) underwent a blinded randomized crossover dietary intervention, consuming a high-SCFA diet and a matched low-SCFA diet for 21-d with a 21-d washout in between. SCFAs were provided through resistant starch, inulin, and apple cider vinegar. Blood and 3-d total fecal output were collected at baseline and at the end of each diet. GC was used to measure fecal and plasma SCFA. Flow cytometry was used for peripheral blood immunophenotyping. According to a paired samples Wilcoxon test, the high-SCFA diet was associated with significantly higher fecal SCFA concentrations [median (IQR); 86.6 (59.0) compared with 75.4 (56.2) µmol/g, P = 0.02] and lower fecal ammonia concentrations [26.2 (14.7) compared with 33.4 (18.5) µmol/g, P = 0.04] than the low-SCFA diet. Plasma propionate [9.87 (12.3) compared with 4.72 (7.6) µmol/L, P = 0.049] and butyrate [2.85 (1.35) compared with 2.02 (1.29) µmol/L, P = 0.03] were significantly higher after the high-SCFA diet than after the low-SCFA diet. Blood total B cells [184 (112) compared with 199 (143) cells/µL, P = 0.04], naive B cells [83 (66) compared with 95 (89) cells/µL, P = 0.02], Th1 cells [22 (19) compared with 29 (16) cells/µL, P = 0.03], and mucosal-associated invariant T cells [62 (83) compared with 69 (114) cells/µL, P = 0.02] were significantly lower after the high-SCFA diet than the low-SCFA diet. Increasing colonic and peripheral blood SCFA has discrete effects on circulating immune cells in healthy humans following 3-wk intervention. Further studies (e.g., in patients with inflammatory disease) are necessary to determine whether 1) these changes have immunomodulatory effects, 2) they are therapeutically beneficial, and 3) prolonged intake might be required. This trial is registered at the Australian New Zealand Clinical Trials Registry as ACTRN12618001054202.

Hybrid materials based on pyrene-substituted metallo phthalocyanines as sensing layers for ammonia detection: Effect of the number of pyrene substituents

In this work, the effect of the number of pyrene substituents in zinc(II) phthalocyanine molecules on the sensor properties of their hybrid materials with single-walled carbon nanotubes (SWCNT) is studied. For this purpose, hybrid materials of SWCNTs modified with five different trioxyethylenethio substituted zinc(II) phthalocyanines containing 0, 1, 2, and 4 methoxypyrene substituents in the phthalocyanine ring were prepared and characterized by Raman spectroscopy, scanning electron microscopy and inductively coupled plasma atomic emission spectrometry. The chemiresistive sensor response of the prepared hybrids toward low concentrations of ammonia (1–100 ppm) was studied to reveal the effect of the number of pyrene substituents in the phthalocyanine ring on the sensor performance of the hybrid materials. It was demonstrated that the hybrids with zinc(II) phthalocyanine bearing four methoxypyrene substituents exhibited the maximal sensor response to ammonia with the limit of detection of 0.4 ppm. The sensitivity of the hybrid materials to ammonia was shown to be much higher than to CO2, H2, H2S, CH4, ethanol, acetone, and dichloromethane vapors, however, an oxidizing gas such as NO2 was an interfering compound in the determination of ammonia. 1 ppm NO2 show the same absolute value of the response than 10 ppm NH3. The quantum-chemical calculations were performed to explain this effect as well as the dependence of the binding energy of substituted zinc(II) phthalocyanines with carbon nanotubes on the number of pyrene substituents.

An enriched ammonia-oxidizing microbiota enables high removal efficiency of ammonia in antibiotic production wastewater

High ammonia concentration hinders the efficient treatment of antibiotic production wastewater (APW). Developing effective ammonia oxidation wastewater treatment strategies is an ideal approach for facilitating APW treatment. Compared with traditional nitrification strategies, the partial nitrification process is more eco-friendly, less energy-intensive, and less excess sludge. The primary limiting factor of the partial nitrification process is increasing ammonia-oxidizing bacteria (AOB) while decreasing nitrite-oxidizing bacteria (NOB). In this study, an efficient AOB microbiota (named AF2) was obtained via enrichment of an aerobic activated sludge (AS0) collected from a pharmaceutical wastewater treatment plant. After a 52-day enrichment of AS0 in 250 mL flasks, the microbiota AE1 with 69.18% Nitrosomonas microorganisms was obtained. Subsequent scaled-up cultivation in a 10 L fermenter led to the AF2 microbiota with 59.22% Nitrosomonas. Low concentration of free ammonia (FA, < 42.01 mg L−1) had a negligible effect on the activity of AF2, and the nitrite-nitrogen accumulation rate (NAR) of AF2 was 98% when FA concentration was 42.01 mg L−1. The specific ammonia oxidation rates (SAORs) at 30 °C and 15 °C were 3.64 kg NH4+-N·kg MLVSS−1·d−1 and 1.43 kg NH4+-N·kg MLVSS−1·d−1 (MLVSS: mixed liquor volatile suspended solids). The SAOR was 0.52 kg NH4+-N·kg MLVSS−1·d−1 when the NaCl concentration was increased from 0 to 20 g L−1, showing that AF2 functioning was stable in a high-level salt environment. The ammonia oxidation performance of AF2 was verified by treating abamectin and lincomycin production wastewater. The NARs of AF2 used for abamectin and lincomycin production wastewater treatment were >90% and the SAORs were 2.39 kg NH4+-N·kg MLVSS−1·d−1 and 0.54 kg NH4+-N·kg MLVSS−1·d−1, respectively, which was higher than the traditional biological denitrification process. In summary, AF2 was effective for APW treatment via enhanced ammonia removal efficiency, demonstrating great potential for future industrial wastewater treatment.

Biogeochemical behaviour of geogenic As in a confined aquifer of the Sologne region, France.

Arsenic (As) is one of the main toxic elements of geogenic origin that impact groundwater quality and human health worldwide. In some groundwater wells of the Sologne region (Val de Loire, France), drilled in a confined aquifer, As concentrations exceed the European drinking water standard (10μgL-1). The monitoring of one of these drinking water wells showed As concentrations in the range 20-25μgL-1. The presence of dissolved iron (Fe), low oxygen concentration and traces of ammonium indicated reducing conditions. The δ34SSO4 was anticorrelated with sulphate concentration. Drilling allowed to collect detrital material corresponding to a Miocene floodplain and crevasse splay with preserved plant debris. The level that contained the highest total As concentration was a silty-sandy clay containing 26.9mgkg-1 As. The influence of alternating redox conditions on the behaviour of As was studied by incubating this material with site groundwater, in biotic or inhibited bacterial activities conditions, without synthetic organic nutrient supply, in presence of H2 during the reducing periods. The development of both AsV-reducing and AsIII-oxidising microorganisms in biotic conditions was evidenced. At the end of the reducing periods, total As concentration strongly increased in biotic conditions. The microflora influenced As speciation, released Fe and consumed nitrate and sulphate in the water phase. Microbial communities observed in groundwater samples strongly differed from those obtained at the end of the incubation experiment, this result being potentially related to influence of the sediment compartment and to different physico-chemical conditions. However, both included major Operating Taxonomic Units (OTU) potentially involved in Fe and S biogeocycles. Methanogens emerged in the incubated sediment presenting the highest solubilised As and Fe. Results support the hypothesis of in-situ As mobilisation and speciation mediated by active biogeochemical processes.

Rates and physicochemical drivers of microbial anabolic activity in deep-sea sediments and implications for deep time.

Sediment microorganisms influence global climate and redox by altering rates of organic carbon burial. However, the activity and ecology of benthic microorganisms are poorly characterized, especially in the deep sea. Here, we conducted nearly 300 stable isotope tracer experiments in sediments from the Pacific and Atlantic oceans (100-4500 m water depth) to determine the rates, spatial distribution, and physicochemical controls on microbial total anabolic activity, nitrogen fixation, and inorganic/organic carbon uptake. Using correlative and manipulative approaches, we find that total activity is limited primarily by organic carbon and/or energy. Activity correlates significantly with distance from shore, sediment depth, C:N ratios, and overlying chlorophyll concentrations and is stimulated by carbon but not nitrogen additions. Consistent with this, nitrogen fixation was undetected despite relatively low concentrations of porewater ammonium and the previous detection of nifH genes. Inorganic carbon uptake accounted for 7%-55% of carbon assimilation per sample (median 21%), suggesting chemoautotrophy is an important and unappreciated source of labile carbon in deep-sea sediments. Community 16S rRNA was dominated by Bacteria (<2% Archaea), primarily Desulfobacterales of the Deltaproteobacteria. Leveraging our findings, we modelled global benthic microbial activity through geologic time and find the potential for significant shifts in total activity with supercontinental cycles.

Benthic nitrogen cycling in the deep ocean of the Kuroshio Extension region

Benthic nitrogen cycling, including nitrification, N-loss, and other nitrogen transformations, plays a crucial role in the marine nitrogen budget. However, studies on benthic nitrogen cycling mainly focus on marginal seas, while attention to the deep ocean, which occupies the largest area of the seafloor, is severely lacking. In this study, we investigate the benthic nitrogen cycling in the Kuroshio Extension region (KE) of the northwest Pacific Ocean at water depths greater than 5,000 m through 15N enrichment slurry incubation and pore-water dissolved oxygen and inorganic nitrogen profiles. The slurry incubation indicates nitrification is the predominant process in benthic nitrogen cycling. The potential nitrification rates are nearly an order of magnitude higher than dissimilatory nitrate reduction. Nitrification and total N-loss flux estimated from pore-water nitrate and ammonium profiles are 6–42 and 5–30 μmol N m−2 d−1, respectively. Generally, anammox is the predominant N-loss process in KE sediment. The temperature gradient experiment indicates that the optimum temperature for anammox and denitrification is 13 and 41°C, respectively, partially explaining anammox as the dominant process for deep-ocean benthic N-loss. Both the low concentration of ammonium in pore-water and the discrepant results between anoxic incubation amended with 15NO3− and 15NH4++14NO3− suggest that ammonium is another limiting factor for benthic anammox. N-loss activity gradually declines with the distance from the Oyashio–Kuroshio transition zone. However, nitrification has the opposite trend roughly. This reveals that the sediment in KE transfers from nitrate sink to source from north to south. This trend is mainly caused by the variation of primary production and the supplement of active organic matter, which is the energy source for microbes and the potential source for ammonium through remineralization. Overall, our results highlight temperature and ammonium as two limiting factors for deep-ocean benthic N-loss and also exhibit a tight coupling relationship between pelagic primary production and the benthic nitrogen cycle in KE.

Efficient and fast removal of total and fecal coliform, BOD, COD and ammonia from raw water by microwave heating technique

Water born pathogen and diseases represent a major concern with respect to water quality. In recent years, high interests have been focused on controlling water born pathogen especially fecal, and total coliform in water resources. The disadvantage of water treatment by chlorine is related to the disinfection by-products (DBPs). Therefore, the study presented here is devoted to explore and testify the suitability and validity of microwave heating system as a promising disinfection and treatment process to remove total and fecal coliform as well as BOD, COD and ammonia from raw drinking water. Raw water samples were collected from two different inlet locations, Khandak El Sharqi Damanhour canal and, Mahmoudia Fisha canal, El-Beheira Governorate, Egypt and subjected to treatment by microwave heating for a period from 10 to 150 s. The collected results confirmed that total coliform and fecal coliform were efficiently removed (100%) upon microwave heating for 150 s. Similarly, the BOD values in raw water samples were 92–94% removed. Inhibition of COD parameter (48–49%) of the initial COD values in raw water samples were confirmed by the influence of also 150 s microwave heating. Finally, the effectiveness of microwave heating for ammonia from water was also established on the basis of excellent percentage removal (100%) of low concentration ammonia levels and (98%) of high concentration levels of ammonia nitrogen at adjusted raw water samples to pH 10–11. The proposed water treatment method may be regarded as a promising approach for removal of these pollutants from various water sources.

Low-concentration ammonia gas sensing using polyaniline nanofiber thin film grown by rapid polymerization technique

Low-concentration ammonia gas sensing using polyaniline nanofiber thin film grown by rapid polymerization technique

Integrative chemical and omics analysis of the ammonia nitrogen removal characteristics and mechanism of a novel oligotrophic heterotrophic nitrification-aerobic denitrification bacterium

A novel oligotrophic heterotrophic nitrification-aerobic denitrification bacterium designated as Pseudomonas sp. N31942, was isolated from a eutrophic lake. Strain N31942 exhibits high ammonia nitrogen removal ability in oligotrophic environment as ammonia nitrogen can be efficiently (86.97 %) removed within 10 h with no accumulation of nitrite. In the nitrification process, strain N31942 can convert ammonia into nitrate in the absence of hydroxylamine oxidase and nitrite oxidoreductase. As for the denitrification process, nitrate or nitrite were reduced to ammonia and further converted into glutamate by dissimilatory nitrate reduction pathway. Transcriptomic analysis detected 2080 differentially expressed genes. Among them, the expression of the related genes in dissimilatory nitrate reduction process was all up-regulated at low ammonia concentrations, which indicates that the strain has excellent nitrogen removal efficiency for further nitrogen removal. Integrative omics analyses revealed that strain N31942 may have two possible pathways for the NH4+-N removal as direct GDH/GS-GOGAT pathway (NH4+-N → Glutamate) and indirect GDH/GS-GOGAT pathway (NH4+-N → NH2OH → NO2−-N → NO3−-N → NO2−-N → NH4+-N → Glutamate). Moreover, strain N31942 also has excellent nitrogen removal ability for real sewage and 77.21 % total nitrogen could be removed within 48 h. The results presented here provide new insights into ammonia nitrogen removal characteristics and mechanism of heterotrophic nitrification-aerobic denitrification bacterium under oligotrophic conditions.

Soluble fibre concentration effects during in vitro fermentation: Higher concentration leads to increased butyrate proportion

Dietary fibre (DF) fermentation outcomes are often thought to be based on their chemical structure and molecular weight, but less is known about concentration effects. In this study, two oligosaccharides: raffinose (Raff), fructo-oligosaccharides (FOS); and two polysaccharides: β-glucan from oats (BGlu) and pectin from apple (Pect), at different concentrations (0.1, 0.2, 0.3 and 0.4 g/43 mL bottle), were subjected to in vitro batch fermentation using a pooled human faecal inoculum. The DF type and concentration effects on the fermentation properties of these DF were investigated. Results showed that DF types had no obvious effects on the total gas volume, maximum rate of gas production, total short chain fatty acid (SCFA) or ammonia concentration, although polysaccharides took longer to reach maximum gas production. Higher DF concentration led to higher total gas volume, total SCFA concentration, maximum rate of gas production and time to reach maximum rate, but lower ammonia concentration. The most interesting observation was that for all DF, while the total SCFA concentrations increased linearly with DF concentration, the proportion of butyrate increased significantly as the DF concentration increased. It was hypothesised that increased butyrate was because of acetate to butyrate conversion, via butyryl-CoA:acetate-CoA transferase, but a further in vitro fermentation experiment using different concentrations of FOS and Pect, (0.2 and 0.4 g/bottle) with the addition of sodium acetate did not show enhanced butyrate production. It is concluded that concentration is a critical functional property of DF as it is closely related to fermentation kinetics and outcomes, particularly butyrate proportion. • DF concentration and chemistry both affected fermentation outcomes. • Higher DF concentration led to lower proportion of acetate concentration. • Higher DF concentration led to higher proportion of butyrate concentration. • Butyrate proportion was not increased by addition of acetate to medium.

Selective Enrichment of Comammox Nitrospira in a Moving Bed Biofilm Reactor with Sufficient Oxygen Supply.

The recent discovery of comammox (complete ammonia oxidation) Nitrospira has upended the long-held nitrification paradigm. Although comammox Nitrospira have been identified in wastewater treatment systems, the conditions for their dominance over canonical ammonia oxidizers remain unclear. Here, we report the dominance of comammox Nitrospira in a moving bed biofilm reactor (MBBR) fed with synthetic mainstream wastewater. Integrated 16S rRNA gene amplicon sequencing, fluorescence in situ hybridization (FISH), and metagenomic sequencing methods demonstrated the selective enrichment of comammox bacteria when the MBBR was operated at a dissolved oxygen (DO) concentration above 6 mg O2/L. The dominance of comammox Nitrospira over canonical ammonia oxidizers (i.e., Nitrosomonas) was attributed to the low residual ammonium concentration (0.02-0.52 mg N/L) formed in the high-DO MBBR. Two clade A comammox Nitrospira were identified, which are phylogenetically close to Candidatus Nitrospira nitrosa. Interestingly, cryosectioning-FISH showed these two comammox species spatially distributed on the surface of the biofilm. Moreover, the ammonia-oxidizing activity of comammox Nitrospira-dominated biofilms was susceptible to the oxygen supply, which dropped by half with the DO concentration decrease from 6 to 2 mg O2/L. These features collectively suggest a low apparent oxygen affinity for the comammox Nitrospira-dominated biofilms in the high-DO nitrifying MBBR.

Effects of dietary xylooligosaccharides supplementation on the intestinal morphology, nitrogen metabolism, faecal ammonia release, antioxidant capacity, and immune organ indices of broilers

This aim of the present study was to evaluate the effects of dietary xylooligosaccharides (XOS) on the intestinal morphology, nitrogen metabolism, faecal ammonia release, antioxidant capacity, and immune organ indices of broilers fed corn-soybean meal diet. A total of 240 healthy 1-day-old Arbour Acres (AA) broilers were randomly divided into four treatment groups receiving XOS supplementation of 0 (Control), 150, 300, and 450 mg/kg to basal diet for 6 weeks. Six replicates with 10 birds each were prepared for each treatment. Results showed that the villus height of duodenum, jejunum, and ileum and the villus height to crypt depth ratio of jejunum were increased significantly in the broilers receiving 150 mg/kg XOS compared with those in the Control (p < 0.05). Nitrogen utilisation from day 19 to 21 was higher in the 150 mg/kg XOS group than in the Control (p < 0.05). Moreover, the addition of 150 mg/kg XOS reduced the nitrogen excretion from day 40 to 42 (p < 0.05), and all XOS treatments increased the nitrogen utilisation from day 40 to 42 (p < 0.05). All dietary XOS supplementations decreased the faecal ammonia concentration on day 21 (p < 0.05), and the addition of 150 and 450 mg/kg XOS induced a lower faecal ammonia concentration compared with that of the Control on day 42 (p < 0.05). Dietary supplementation of 300 and 450 mg/kg XOS enhanced the activity of serum total antioxidant capacity compared with that in the Control and 150 mg/kg XOS groups at the age of 42 days (p < 0.05). Supplementation with 450 mg/kg XOS significantly increased the index of thymus (p < 0.05) and the content of total protein compared with those of the Control at the age of 21 days (p < 0.05). Therefore, dietary supplementation with 150 mg/kg XOS have a beneficial effect on broilers. Highlights Dietary supplementation with XOS increased the villus height of duodenum, jejunum and ileum, and the VH/CD ratio of jejunum. Dietary supplementation with XOS enhanced nitrogen metabolism and reduced faecal ammonia release.

Optimized titania nanotubes photoanode mediated photoelectrochemical oxidation of ammonia in highly chlorinated wastewater via Cl-based radicals

Efficient removal of low-concentration ammonia from chlorinated wastewater is a challenge for decentralized wastewater treatment due to its notorious environmental effect and lethal influence on aquaculture. Photoelectrocatalytic (PEC) oxidation process is considered as an efficient and environment–friendly approach, whereas a low-cost and stable photoanode is crucial. In this study, TiO2 nanotubes (TNTs) photoanode (Ar–TNT–500 °C) with excellent physicochemical and photoelectrochemical properties was prepared by optimizing the parameters of anodization, including the voltage/times of anodization and the atmosphere/temperature of heat treatment. During the synthesis, the electrochemical and heat treatment processes promoted the formation of oxygen vacancies (OV) on the TNTs surface and enhanced its electrocatalytic activity. The optimized Ar–TNT–500 °C photoanode could selectively convert ammonia to N2 (86%) and a small amount of nitrate (14%). Radical quenching and probe experiments confirmed that the ClO produced by rapid quenching of OH and Cl by free chlorine dominated the selective degradation of ammonia in the synergistic process of photocatalysis and electrocatalysis. The cycle of chlorine-based radicals (ClO and Cl) and Cl− provided a continuous and efficient ammonia oxidation system, because chlorine-based radicals could efficiently and selectively oxidize ammonia and reduce the production of toxic (per) chlorate.

Regulating the Pore Microenvironment of Microporous Metal–Organic Frameworks for Efficient Adsorption of Low-Concentration Ammonia

Regulating the Pore Microenvironment of Microporous Metal–Organic Frameworks for Efficient Adsorption of Low-Concentration Ammonia

From Photocatalysis to Photo-Electrocatalysis: An Innovative Water Remediation System for Sustainable Fish Farming

In this study, the effects of photo-electrocatalysis (PEC) were evaluated as an innovative application of conventional photocatalysis (PC) to remediate water in a recirculating system for rainbow trout (Oncorhynchus mykiss) culture, in relation to fish welfare and health, with a multidisciplinary approach. Three tanks were employed, equipped with conventional biological filters as a control system, and three tanks equipped with the PEC purification system. The concentrations of ammonia, nitrite and nitrate ions in water were monitored, and the fish’s oxidative damage and stress response were evaluated in parallel. The water of the PEC-treated experimental group showed lower ammonia (TAN) and nitrite concentrations and higher nitrate concentration, possibly deriving from TAN oxidation through PEC, also leading to gaseous N2. Histological analysis did not reveal any pathological alteration in the gills and liver of both groups. The superoxide dismutase (sod1), glutathione reductase (GR), glutathione peroxidase (GPx1), and Tumor necrosis factor (TNFα) gene expressions were significantly higher in the control group than in the PEC-treated group, while the Heat shock protein 70 (Hsp70) expression did not show any difference in the two groups. These results indicate that the use of PEC filters has a positive effect on water quality, compared to the use of conventional biological filters, inducing a high level of welfare in O. mykiss.

Exaggerated trans-membrane charge of ammonium transporters in nutrient-poor marine environments.

Transporter proteins are a vital interface between cells and their environment. In nutrient-limited environments, microbes with transporters that are effective at bringing substrates into their cells will gain a competitive advantage over variants with reduced transport function. Microbial ammonium transporters (Amt) bring ammonium into the cytoplasm from the surrounding periplasm space, but diagnosing Amt adaptations to low nutrient environments solely from sequence data has been elusive. Here, we report altered Amt sequence amino acid distribution from deep marine samples compared to variants sampled from shallow water in two important microbial lineages of the marine water column community-Marine Group I Archaea (Thermoproteota) and the uncultivated gammaproteobacterial lineage SAR86. This pattern indicates an evolutionary pressure towards an increasing dipole in Amt for these clades in deep ocean environments and is predicted to generate stronger electric fields facilitating ammonium acquisition. This pattern of increasing dipole charge with depth was not observed in lineages capable of accessing alternative nitrogen sources, including the abundant alphaproteobacterial clade SAR11. We speculate that competition for ammonium in the deep ocean drives transporter sequence evolution. The low concentration of ammonium in the deep ocean is therefore likely due to rapid uptake by Amts concurrent with decreasing nutrient flux.

Heterostructures Based on Cobalt Phthalocyanine Films Decorated with Gold Nanoparticles for the Detection of Low Concentrations of Ammonia and Nitric Oxide.

This work is aimed at the development of new heterostructures based on cobalt phthalocyanines (CoPc) and gold nanoparticles (AuNPs), and the evaluation of the prospects of their use to determine low concentrations of ammonia and nitric oxide. For this purpose, CoPc films were decorated with AuNPs by gas-phase methods (MOCVD and PVD) and drop-casting (DC), and their chemiresistive sensor response to low concentrations of NO (10–50 ppb) and NH3 (1–10 ppm) was investigated. A comparative analysis of the characteristics of heterostructures depending on the preparation methods was carried out. The composition, structure, and morphology of the resulting hybrid films were studied by X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma atomic emission (ICP-AES) spectroscopy, as well as electron microscopy methods to discuss the effect of these parameters on the sensor response of hybrid films to ammonia and nitric oxide. It was shown that regardless of the fabrication method, the response of Au/CoPc heterostructures to NH3 and NO gases increased with an increase in the concentration of gold. The sensor response of Au/CoPc heterostructures to NH3 increased 2–3.3 times compared to CoPc film, whereas in the case of NO it increased up to 16 times. The detection limits of the Au/CoPc heterostructure with a gold content of ca. 2.1 µg/cm2 for NH3 and NO were 0.1 ppm and 4 ppb, respectively. It was shown that Au/CoPc heterostructures can be used for the detection of NH3 in a gas mixture simulating exhaled air (N2—74%, O2—16%, H2O—6%, CO2—4%).