Nitrogen Elimination Research Articles

Collision-Induced Dissociation of Diazirine-Labeled Peptide Ions. Evidence for Brønsted-Acid Assisted Elimination of Nitrogen

Gas-phase dissociations were investigated for several peptide ions containing the Gly-Leu* N-terminal motif where Leu* was a modified norleucine residue containing the photolabile diazirine ring. Collisional activation of gas-phase peptide cations resulted in facile N₂ elimination that competed with backbone dissociations. A free lysine ammonium group can act as a Brønsted acid to facilitate N₂ elimination. This dissociation was accompanied by insertion of a lysine proton in the side chain of the photoleucine residue, as established by deuterium labeling and gas-phase sequencing of the products. Electron structure calculations were used to provide structures and energies of reactants, intermediates, and transition states for Gly-Leu*-Gly-Gly-Lys amide ions that were combined with RRKM calculations of unimolecular rate constants. The calculations indicated that Brønsted acid-catalyzed eliminations were kinetically preferred over direct loss of N₂ from the diazirine ring. Mechanisms are proposed to explain the proton-initiated reactions and discuss the reaction products. The non-catalyzed diazirine ring cleavage and N₂ loss is proposed as a thermometer dissociation for peptide ion dissociations.

Altered Nitrogen Balance and Decreased Urea Excretion in Male Rats Fed Cafeteria Diet Are Related to Arginine Availability

Hyperlipidic diets limit glucose oxidation and favor amino acid preservation, hampering the elimination of excess dietary nitrogen and the catabolic utilization of amino acids. We analyzed whether reduced urea excretion was a consequence of higher NOx; (nitrite, nitrate, and other derivatives) availability caused by increased nitric oxide production in metabolic syndrome. Rats fed a cafeteria diet for 30 days had a higher intake and accumulation of amino acid nitrogen and lower urea excretion. There were no differences in plasma nitrate or nitrite. NOx and creatinine excretion accounted for only a small part of total nitrogen excretion. Rats fed a cafeteria diet had higher plasma levels of glutamine, serine, threonine, glycine, and ornithine when compared with controls, whereas arginine was lower. Liver carbamoyl-phosphate synthetase I activity was higher in cafeteria diet-fed rats, but arginase I was lower. The high carbamoyl-phosphate synthetase activity and ornithine levels suggest activation of the urea cycle in cafeteria diet-fed rats, but low arginine levels point to a block in the urea cycle between ornithine and arginine, thereby preventing the elimination of excess nitrogen as urea. The ultimate consequence of this paradoxical block in the urea cycle seems to be the limitation of arginine production and/or availability.

Unsaturated Flow Drying Bed (UFDB): An Alternative for Treatment of Septic Tanks Sludge

Unsaturated Flow Drying Bed (UFDB) principles are based on the ones of wastewater treatment by infiltration-percolation on the one hand and septic tanks sludge solar-drying beds on the other hand. With UFDB, sludge charges are split with low heights, leading to the drying of suspended solids in 2 days, and the infiltration of the flow of liquid in unsaturated middle. For average charges reaching 12.5 cm/d, the treatment efficiency of total oxygen demand and Total Kjeldahl Nitrogen, respectively 95 and 96%, correspond to a treatment capacity of 0.5 kg of O2/d/m2 of drying area. Bacteria reductions of 4 Ulog are obtained from filtrates outlet, with average fecal coliforms charges less than 103 CFU/100 ml. Monitoring the hydrodynamic behavior through rates, moisture, organic matter and respiratory activity demonstrates that the clogging of the massifs is linked to a biofilm growth within them. A four week resting period allows biofilm resorption. Thus, the drying of the infiltration surface in two days, the elimination of carbon, nitrogen and bacterial pollutions, as well as the reversibility of clogging show that UFDB is a credible alternative for the treatment of septic tank sludge in the socio-economic context and climate of tropical Africa.

Prednisolone but Not Infliximab Aggravates the Upregulated Hepatic Nitrogen Elimination in Patients with Active Inflammatory Bowel Disease

Catabolism and weight loss are serious problems in patients with active inflammatory bowel disease (IBD). The body nitrogen (N) depletion is partly related to increased hepatic capacity for the elimination of N through urea synthesis. This is probably caused by the inflammation per se, and the treatment with prednisolone may aggravate the problem, whereas the effect of biological therapy is unknown. Therefore, we examined the effects of prednisolone or infliximab on the regulation of urea synthesis in patients with active IBD. Urea synthesis was quantified by the functional hepatic nitrogen clearance (FHNC), i.e., the slope of the linear relationship between the urea nitrogen synthesis rate and the blood α-amino nitrogen concentration during alanine infusion. Thirty-seven patients with active IBD treated with either prednisolone or infliximab were examined before and after 7 days of treatment. At baseline, the FHNC was similar in the 2 treatment groups (36 L/h). After 7 days, prednisolone increased the FHNC by 40% (55 L/h) (P = 0.03), whereas infliximab tended to reduce the FHNC by 15% (30 L/h) (P = 0.09). The changes in the FHNC differed significantly between the 2 treatment groups (P < 0.01). Prednisolone treatment further upregulated urea synthesis, which increases the hepatic loss of nitrogen and promotes body catabolism. In contrast, infliximab treatment caused no such aggravation and likely reduced the N loss. These results may argue in favor of infliximab therapy for IBD and add to the pathophysiological understanding of the interplay between inflammation, catabolism, and anti-inflammatory treatment.

New urban wastewater treatment with autotrophic membrane bioreactor at low chemical oxygen demand/N substrate ratio

The potential for total nitrogen removal from municipal wastewater has been evaluated in an autotrophic membrane bioreactor running with a low chemical oxygen demand (COD)/N ratio to simulate its combination with an upstream physicochemical process that retains a large proportion of organic matter. The tests were conducted in a laboratory scale submerged membrane bioreactor loaded with a synthetic influent. Nitrogen loading rate was 0.16 kgN-NH4+.m(-3).d(-1) and sodium acetate was added as a carbon source. Results have shown that nitrogen elimination can reach 85% for a COD/N ratio of 5, with COD removal exceeding 97%. However, a COD/N ratio of 3.5 was found to be the limiting factor for successfully reaching the overall target value of 10 mgN.L(-1) in the effluent. Nevertheless, low COD/N ratios make it possible to work with low total suspended solid concentrations in the bioreactor, which greatly facilitates membrane fouling control by a simple aeration and backwashing strategy.

Successful application of nitritation/anammox to wastewater with elevated organic carbon to ammonia ratios

The nitritation/anammox process has been mainly applied to high-strength nitrogenous wastewaters with very low biodegradable organic carbon content (<0.5 g COD∙g N−1). However, several wastewaters have biodegradable organic carbon to nitrogen (COD/N) ratios between 0.5 and 1.7 g COD∙g N−1 and thus, contain elevated amounts of organic carbon but not enough for heterotrophic denitrification. In this study, the influence of elevated COD/N ratios was studied on a nitritation/anammox process with suspended sludge. In a step-wise manner, the influent COD/N ratio was increased to 1.4 g COD∙g N−1 by supplementing digester supernatant with acetate. The increasing availability of COD led to an increase of the nitrogen removal efficiency from around 85% with pure digester supernatant to >95% with added acetate while the nitrogen elimination rate stayed constant (275 ± 40 mg N∙L−1∙d−1). Anammox activity and abundance of anammox bacteria (AMX) were strongly correlated, and with increasing influent COD/N ratio both decreased steadily. At the same time, heterotrophic denitrification with nitrite and the activity of ammonia oxidising bacteria (AOB) gradually increased. Simultaneously, the sludge retention time (SRT) decreased significantly with increasing COD loading to about 15 d and reached critical values for the slowly growing AMX. When the SRT was increased by reducing biomass loss with the effluent, AMX activity and abundance started to rise again, while the AOB activity remained unaltered. Fluorescent in-situ hybridisation (FISH) showed that the initial AMX community shifted within only 40 d from a mixed AMX community to “Candidatus Brocadia fulgida” as the dominant AMX type with an influent COD/N ratio of 0.8 g COD∙g N−1 and higher. “Ca. Brocadia fulgida” is known to oxidise acetate, and its ability to outcompete other types of AMX indicates that AMX participated in acetate oxidation. In a later phase, glucose was added to the influent instead of acetate. The new substrate composition did not significantly influence the nitrogen removal nor the AMX activity, and “Ca. Brocadia fulgida” remained the dominant type of AMX. Overall, this study showed that AMX can coexist with heterotrophic bacteria at elevated influent COD/N ratios if a sufficiently high SRT is maintained.

Nitrogen and organic load removal from sanitary landfill leachates by anodic oxidation at Ti/Pt/PbO2, Ti/Pt/SnO2-Sb2O4 and Si/BDD

Ti/Pt/PbO2, Ti/Pt/SnO2-Sb2O4 and boron-doped diamond (BDD) anodes were used to study the influence of the anode material on nitrogen and organic load removal from a biologically pretreated leachate from an intermunicipal sanitary landfill: chemical oxygen demand (COD) – 6.2gL−1 and ammonium nitrogen (AN) – 0.48gL−1. The experimental results showed that for the three anode materials under study, the COD removals were similar despite the BDD anode more easily promoting the complete combustion of the organic matter. Regarding nitrogen removal, metal oxide anodes were effective in the removal of AN, whereas BDD was more efficient in the removal of organic nitrogen. For similar experimental conditions, Ti/Pt/PbO2 demonstrated the highest AN removal (90%), followed by Ti/Pt/SnO2-Sb2O4 (64%) and BDD (56%). Simulated samples with analogous nitrogen content but without organic matter were also electrolyzed to better understand the elimination of the different forms of nitrogen present in the samples. At BDD anodes, ammonium is oxidized to nitrate, maintaining the nitrogen content higher than in the samples treated with the metal oxides, whereas these latter materials are more effective in the complete elimination of nitrogen, due to partial oxidation to nitrogen gas, showing that BDD is more predisposed to promote complete combustion. The anodes of metallic oxides demonstrated lower energy consumption than BDD; the energetic behavior of Ti/Pt/PbO2 and Ti/Pt/SnO2-Sb2O4 was very similar.

Gold-Mediated Expulsion of Dinitrogen from Organic Azides

Organoazides and their nitrogen expulsion chemistry have attracted the attention of many scientists because they serve as a useful source of nitrene fragments and interesting nitrene rearrangement products. Gold-mediated reactions are also of significant current interest. This manuscript describes several important discoveries based at the intersection of these fields. In particular, we report the first isolable gold organoazides ([(SIPr)AuN(1-Ad)NN][SbF6], [(SIPr)AuN(2-Ad)NN][SbF6] and [(SIPr)AuN(Cy)NN][SbF6]; SIPr = a N-heterocyclic carbene; 1-AdNNN = 1-azidoadamantane; 2-AdNNN = 2-azidoadamantane; CyNNN = azidocyclohexane), and their gold-mediated nitrogen expulsion chemistry, and the isolation of formal nitrene rearrangement products of "1-AdN", "2-AdN" and "CyN" (including the elusive 4-azahomoadamant-3-ene) as their gold complexes. We have also performed a computational study to understand and explain the observed structure of gold-coordinated 1-AdNNN and 2-AdNNN and their nitrogen elimination pathways, which implies that the conversion of the organoazide complex to the imine is a concerted process without a nitrene/nitrenoid intermediate. Kinetic studies of [(SIPr)AuN(2-Ad)NN][SbF6] from 30 to 50 °C indicate that nitrogen elimination is a first-order process. The experimentally determined activation parameters are in good agreement with the calculated values.

Elimination of nitrogen present in swine manure using a high-efficiency biotrickling filter

Experiments were performed to remove nitrogen as ammonium in biotrickling filters (BTFs) treating synthetic swine manure. Two BTFs packed with polypropylene spheres and ceramic beads were used. BTFs were continuously fed, and leachate obtained was recirculated at different flow rates in the range from 0 to 1.5 L min−1. When increasing the recirculation flow rate, the carbon dioxide (CO2) production rate increased from 16.5 to 25.6 g CO2 m−3 h−1 and nitrogen elimination decreased from 99% to 86% for the polypropylene spheres, whereas for the ceramic beads the CO2 production rate decreased from 20.3 to 15.0 g CO2 m−3 h−1 and nitrogen removal from 99% to 90%. The increase of recirculation flow rates also promoted the production of nitrite () in the leachate. For both packing types, when increasing nitrogen loads from 60 to 240 g N m−3 day−1 without recirculation of leachate, the BTFs achieved nitrogen removals of more than 99%. For the same nitrogen loads, nitrogen removal increased from 90% to 99% for the BTF packed with ceramic beads at a recirculation flow rate of 0.6 L min−1. Operating the BTFs with continuous purge was optimal for biomass production with a maximum level of 71.3 g m−3 day−1.

Reaction of barbituric acid with organic azides and phosphonium ylides

Abstract Amination by organic azides has been carried out to provide aminobarbiturates by fusion of a triazole ring to the 5,6-positions of barbituric acid followed by cleavage and thermal elimination of nitrogen, whereas aza-Wittig reaction gave phosphoranylidene barbituric acid salts.

Nitrogen balance estimation in a subsurface flow constructed wetland planted with Heliconia psittacorum for domestic wastewater treatment

The influence of vegetation (Heliconia psittacorum) and the main nitrogen elimination mechanism were studied via the mass balance method in a subsurface flow constructed wetland (HFSS). Six HFSS lab-scale units (microcosms) were built and filled out vertically with gravel and coarse sand. Three of the lab-scale units were planted with Heliconia sp., and the remaining three were left unplanted and run as control units. All of the experimental units were operated with an organic surface load of 5.68 g N m-2 d-1, and a theoretical hydraulic retention time (HRT) of 1.0 day. Results showed a higher N load removal efficiency in the planted units (29.6%) compared to the unplanted ones (24.3%). The nitrogen balance showed that coupled nitrification/denitrification was the main N removal mechanism, since its contribution to the overall removal was 66.7 and 69.7% in planted and unplanted units, respectively. Meanwhile, N accumulation in the support media removed 21.4 and 22.0 % in planted and unplanted units, respectively. N assimilation via physiological activity of Heliconia sp. was responsible for only 0.6 % of the total removal. Despite this low removal rate, it was evident that plants contributed indirectly to N removal in the planted units via atmospheric oxygen translocation and the assemblage of a more diverse microbial community in the rizospheric habitat.

The Experimental Study on Landfill Leachate Treatment by Coagulation-Sedimentation + Electro-Oxidation Joint Reactor

The technology used the coagulation-sedimentation + electro-oxidation joint reactor has been studied to treat landfill leachate. First adding FeCl30.4g/L into all leachate for coagulation and sedimentation, its CODcr elimination rate can achieve 35%, but does have no effect on ammonia nitrogen. Then using electro-oxidation reactor to deal with effluent water, the reaction order of electro-oxidation reactor is first-level, as the reaction conditions are 20mA/cm2 of electric current density, 140min of reaction time, the leachate CODcr elimination rate can reach to above 90%, the ammonia nitrogen elimination rate meets to 98% around. Using coagulation-sedimentation + electro coagulation joint reactor to treat landfill leachate can get stable effluent water quality with good treatment effect, has very high elimination efficiency of CODcr and ammonia nitrogen. It is a suitable treatment technology for landfill leachate.

Synthesis of Glycoconjugate Benzothiazoles via Cleavage of Benzotriazole Ring

A concise and efficacious benzotriazole-mediated novel two-step protocol has been developed for easy access to glycoconjugate benzothiazoles from protected carbohydrates. The benzotriazolemethanethione 3, prepared by the reaction of free alcohol with bis(1H-benzo[1,2,3]triazol-1-yl)methanethione, on treatment with silanes or stannane under heating or microwave irradiation undergoes free radical β-scission of N-N bond and affords diverse range of 2-O-substituted benzothiazoles 4 via cyclative elimination of molecular nitrogen. The structures of all of the compounds have been elucidated using IR, NMR, MS, and elemental analysis, and five of them have been characterized by single-crystal X-ray analysis.

メラミン樹脂からのBCN材料の調製とその高電気二重層容量の要因

Melamine resin containing boron was synthesized from boric acid, melamine, and formaldehyde. B/C/N materials were prepared by carbonization in an inert gas atmosphere at 800-1200 °C. The boron/carbon atomic ratio (B/C) increased from 0.02 to 0.42 as a result of the formation of more B-N bonds with increasing heat treatment temperature, and it is the formation of these bonds that fixes the nitrogen in the structure. XPS measurements indicate that nitrogen atoms are involved in the following bonding states: B-N, pyridine-type N, quaternary-N and B-N-C. It is clear that B-N-C and B-N bonds are formed during carbonization at temperatures >800 °C, where the elimination of nitrogen is usually observed, and these are responsible for the N retention. As a result, a high N/C atomic ratio of 0.09-0.42 was observed for a carbonization temperature greater than 800 °C. The EDLC capacitance of a material heat treated at 1000 °C with N/C of 0.24 had a high value of 500 F·g-1 in spite of having a smaller specific surface area compared to that of activated carbon widely used in EDLC.

A systematic insight into a single-stage deammonification process operated in granular sludge reactor with high-loaded reject-water: characterization and quantification of microbiological community

Reject-water from sludge dewatering was treated in a single-stage deammonification reactor. The aims were to characterize the microbiological community within deammonification granules. In situ mapping of the intact granular sludge were made with fluorescent in situ hybridization (FISH). The Planctomycetes community in the destroyed granular sludge was characterized by FISH, polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), cloning and sequence analysis. AOB within Betaproteobacteria were concentrated within the first 50-100 μm of the granule, and Planctomycetes in the first 100-200 μm were responsible for nitrogen elimination. PCR-DGGE verified the higher diversity of Planctomycetes in the deammonification reactor than the anaerobic cultivation. The sequence analysis after PCR-DGGE and cloning identified the dominant Planctomycetes species for anammox reaction as Ca. Brocadia fulgida (accession no. EU478693). FISH detection using the universal probe AMX368 specific for all anammox bacteria including Ca. Brocadia fulgida failed; however, the probe BFU613 specific for Ca. Brocadia fulgida gave clear positive FISH signals. The three-dimensional structure of the ribosome may hinder binding of the universal probe to the corresponding 16S rRNA region. A combination of multiple methods for the analysis of the microbiological community was necessary. Oligonucleotide probes should be carefully selected, and a negative FISH analysis has to be verified by other molecular biological techniques.

Nitrate removal in a restored riparian groundwater system: functioning and importance of individual riparian zones

Abstract. For the design and the assessment of river restoration projects, it is important to know to what extent the elimination of reactive nitrogen (N) can be improved in the riparian groundwater. We investigated the effectiveness of different riparian zones, characterized by a riparian vegetation succession, for nitrate (NO3−) removal from infiltrating river water in a restored and a still channelized section of the river Thur, Switzerland. Functional genes of denitrification (nirS and nosZ) were relatively abundant in groundwater from willow bush and mixed forest dominated zones, where oxygen concentrations remained low compared to the main channel and other riparian zones. After flood events, a substantial decline in NO3− concentration (&gt; 50%) was observed in the willow bush zone but not in the other riparian zones closer to the river. In addition, the characteristic enrichment of 15N and 18O in the residual NO3− pool (by up to 22‰ for δ15N and up to 12‰ for δ18O) provides qualitative evidence that the willow bush and forest zones were sites of active denitrification and, to a lesser extent, NO3− removal by plant uptake. Particularly in the willow bush zone during a period of water table elevation after a flooding event, substantial input of organic carbon into the groundwater occurred, thereby fostering post-flood denitrification activity that reduced NO3− concentration with a rate of ~21 μmol N l−1 d−1. Nitrogen removal in the forest zone was not sensitive to flood pulses, and overall NO3− removal rates were lower (~6 μmol l−1 d−1). Hence, discharge-modulated vegetation–soil–groundwater coupling was found to be a key driver for riparian NO3− removal. We estimated that, despite higher rates in the fairly constrained willow bush hot spot, total NO3− removal from the groundwater is lower than in the extended forest area. Overall, the aquifer in the restored section was more effective and removed ~20% more NO3− than the channelized section.

Gas Phase Pyrolysis Reaction of 1-pyrazoline: A Theoretical Kinetic Study

We report kinetic and mechanistic studies of nitrogen elimination from 1-pyrazoline and its deuterated derivatives. This study was carried out for the gas phase employing 6-311 + G(d,p) basis sets with B3LYP, MPW1PW91 and PBEPBE methods. This reaction may proceed through two different mechanisms, molecular and radical. The molecular mechanism advances via two different paths and corresponding intermediates. There are either a four-centred cyclic or a six-centred cyclic intermediate as transition states in the molecular mechanism. The calculated kinetic parameters and isotope effects for the molecular mechanism are consistent with experimental results for cyclopropane formation. However, from the kinetic isotope effects point of view, the fit is better for the radical mechanism for propene formation. Considering activation energies, theoretical calculations suggest that the radical mechanism is the less suitable. The B3LYP method results are in a better agreement with the experimental results when considering only computational data.

Impacts of shrimp farm effluent on water quality, benthic metabolism and N-dynamics in a mangrove forest (New Caledonia)

Water quality parameters, sediment oxygen demand (SOD), dissolved organic and inorganic nutrient fluxes, and N-cycle processes (nitrification; denitrification; dissimilatory nitrate reduction to ammonium (DNRA)) were determined in a New Caledonian mangrove receiving shrimp farm effluent and a natural mangrove. Effluent was enriched in nutrients and organic matter, and significantly stimulated SOD and nutrient regeneration rates in the receiving sediments. All N-cycling processes were stimulated between ∼2 and 12-fold in the sediments receiving effluents compared to the natural mangrove. However, due to the preferential enhancement of DNRA compared to denitrification, there was no significant increase in net nitrogen elimination compared to the significant increase in sediment nutrient regeneration rates. These results indicate that the mangroves are only a partial filter for the shrimp farm effluent, as confirmed by the elevated nutrient concentrations measured in an external, marine creek of the effluent receiving mangrove.

Electrodegradation of tetracycline on BDD anode

The anodic oxidation of tetracycline was performed in an up-flow reactor, operating in batch mode with recirculation, using as anode a boron-doped diamond electrode. The influence on the degradation rate of tetracycline initial concentration and recirculation flow rate were investigated. Assays were performed at constant current density, 300Am−2, using as electrolyte a sodium sulfate aqueous solution, 5gL−1. At the experimental conditions tested, HPLC results have shown an almost complete removal of tetracycline after 2h assay. The removals of the organic load, measured as chemical oxygen demand (COD) and total organic carbon (TOC), increased with tetracycline initial concentration and recirculation flow rate. At the highest recirculation flow rate tested, 100Lh−1, with an initial tetracycline concentration of 150mgL−1, after 4h assay, the removals of COD, TOC and absorbance (measured at 276.5 and 360.0nm) were 93%, 87%, 99% and 100%, respectively. Regarding the total Kjeldahl nitrogen elimination, it takes place mainly via transformation of organic nitrogen into ammonium, nitrate and nitrite. The total nitrogen removal increased with initial tetracycline concentration and showed also a tendency to increase with recirculation flow rate.

Nitrogen removal from wastewater and bacterial diversity in activated sludge at different COD/N ratios and dissolved oxygen concentrations

The impact of the organic carbon to nitrogen ratio (chemical oxygen demand (COD)/N) in wastewater and dissolved oxygen (DO) concentration on carbon and nitrogen removal efficiency, and total bacteria and ammonia-oxidizing bacteria (AOB) communities in activated sludge in constantly aerated sequencing batch reactors (SBRs) was determined. At DO of 0.5 and 1.5 mg O2/L during the aeration phase, the efficiency of ammonia oxidation exceeded 90%, with nitrates as the main product. Nitrification and denitrification achieved under the same operating conditions suggested the simultaneous course of these processes. The most effective nitrogen elimination (above 50%) was obtained at the COD/N ratio of 6.8 and DO of 0.5 mg O2/L. Total bacterial diversity was similar in all experimental series, however, for both COD/N ratios of 6.8 and 0.7, higher values were observed at DO of 0.5 mg O2/L. The diversity and abundance of AOB were higher in the reactors with the COD/N ratio of 0.7 in comparison with the reactors with the COD/N of 6.8. For both COD/N ratios applied, the AOB population was not affected by oxygen concentration. Amplicons with sequences indicating membership of the genus Nitrosospira were the determinants of variable technological conditions.