Nitrogen Elimination Research Articles

The first examples of cycloadditions of 2-diazo-1,3-dicarbonyl compounds to aromatic thioketones

Acyclic 2-diazo-1,3-dicarbonyl compounds react at 20–50°С with aromatic thioketones and through a cascade process, involving the cycloaddition of a diazo group dipole with the CS bond, elimination of nitrogen from the arising thiadiazoline, and subsequent [1,5]-electrocyclization of the intermediate СS-ylide, the relevant oxathioles being formed in yields of up to 70%. Carbocyclic 2-diazo-1,3-diketones at room temperature react with thiones much more slowly, but with increasing temperature they partly decompose to produce, via Wolff rearrangement, 2-oxoketenes, which yield [4+2]-cycloaddition products, that is oxathiinones and/or oxoketene dimers.

Simultaneous removal of TOC and TSS in swine wastewater using the partial nitritation process

AbstractBACKGROUND: Considering biological nitrogen removal, the partial nitritation connected with the anaerobic ammonium oxidation (anammox) process is a promising alternative for nitrogen elimination at high loading rates. The objective of the present study was to evaluate the establishment and operation of a partial nitritation process in an airlift reactor with simultaneous removal of total organic carbon and suspended solids using swine wastewater.RESULTS: The partial nitritation reactor was inoculated with a nitrifying sludge at 2.1 gTSS L−1 and fed with an UASB reactor effluent. High organic carbon loading rates, above 2 kgTOC m−3 d−1 have been shown to be potential inhibitors of the partial nitritation process due to competition between autotrophic and heterotrophic bacteria. In this study, the partial nitritation process was established using undiluted swine wastewater, with HRT of 24 h, 1.84 mgO2 L−1 (SD = 0.41) DO, loading rate of 1.14 gTOC L−1 d−1 and 0.91 gN‐NH3 L−1 d−1 for more than 100 consecutive days. At the same time, the system proved to be an effective tool in TOC and TSS removal, reaching 84.9% (SD = 9.3) and 83.1% (SD = 0.1), respectively.CONCLUSION: This result enhances partial nitritation application as a technology for high load nitrogen converting, and allows the possibility of connection with anammox reactors. Copyright © 2012 Society of Chemical Industry

Wave Packet Dynamics at an Extended Seam of Conical Intersection: Mechanism of the Light-Induced Wolff Rearrangement.

Quantum dynamics calculations on a model surface based on CASPT2//CASSCF calculations are carried out to probe the traversal of a wave packet through an extended seam of conical intersection during the light-induced Wolff rearrangement of diazonaphtoquinone. The reaction is applied in the fabrication of integrated circuits. It consists of nitrogen elimination and ring rearrangement to yield a ketene. After excitation, the wave packet relaxes and reaches the extended seam. A fraction of the wave packet decays to the ground state at a region of the seam connected to a carbene intermediate, while the remaining part decays at a region leading to the ketene. The passage of the wave packet through the extended seam explains the competition between concerted ketene formation and a stepwise mechanism involving a carbene. The two primary photoproducts are formed in the first 100 fs of the simulation, in agreement with recent ultrafast spectroscopy measurements.

Fate of Hazardous Air Pollutants in Oxygen-Fired Coal Combustion with Different Flue Gas Recycling

Experiments were performed to characterize transformation and speciation of hazardous air pollutants (HAPs), including SO(2)/SO(3), NO(x), HCl, particulate matter, mercury, and other trace elements in oxygen-firing bituminous coal with recirculation flue gas (RFG) from 1) an electrostatic precipitator outlet or 2) a wet scrubber outlet. The experimental results showed that oxycombustion with RFG generated a flue gas with less volume and containing HAPs at higher levels, while the actual emissions of HAPs per unit of energy produced were much less than that of air-blown combustion. NO(x) reduction was achieved in oxycombustion because of the elimination of nitrogen and the destruction of NO in the RFG. The elevated SO(2)/SO(3) in flue gas improved sulfur self-retention. SO(3) vapor could reach its dew point in the flue gas with high moisture, which limits the amount of SO(3) vapor in flue gas and possibly induces material corrosion. Most nonvolatile trace elements were less enriched in fly ash in oxycombustion than air-firing because of lower oxycombustion temperatures occurring in the present study. Meanwhile, Hg and Se were found to be enriched on submicrometer fly ash at higher levels in oxy-firing than in air-blown combustion.

Simultaneous nitrogen and carbon removal from swine digester liquor by the Canon process and denitrification

A laboratory-scale completely autotrophic nitrogen removal over nitrite (Canon) biofilm reactor was applied to remove nitrogen and organic carbon from swine digester liquor for 150d. A stable nitrogen removal rate was reached after a three-week adaptation period. The nitrogen loading rate of influent were 0.20±0.04, 0.26±0.04, 0.26±0.07kgNm−3d−1 in period I, II and III, respectively. Nitrogen removal rates reached 0.096, 0.133 and 0.104kgNm−3d−1 when the C/N ratios of liquor were maintained at 0.81, 0.65, and 1.24, respectively. The Canon process was better than the denitrification process for nitrogen elimination when the C/N ratio of the influent was controlled below 0.8. PCR-DGGE analysis showed a decrease in microbial diversity of Planctomycetes during long-term operation. In contrast, the aerobic ammonium-oxidizing bacteria species were resistant to the changes due to replacement of synthetic wastewater with swine digester liquor.

Generation of benzofuroxans by photolysis of crystalline o-nitrophenylazides. A green chemistry reaction

Several benzofuroxans were obtained by photolysis of crystalline o-nitrophenylazides at ambient temperature. In this particular case, the solid matrix favored the elimination of nitrogen and exclusive formation of heterocyclic benzofuroxan. However, this reaction gives quantitative yields only with crystalline o-nitrophenylazides with a high melting point (above 50°C).

Full-scale experience with the deammonification process to treat high strength sludge water – a case study

More stringent effluent criteria with regard to nitrogen calls for improved nutrient removal techniques in wastewater treatment plants (WWTPs). Besides optimisation of the liquid treatment train of the plants, attention has increasingly centred on the problem of return flows from sludge treatment. One of the most recent developments aimed at the reduction of this nitrogen load is deammonification which has been used at one of Ruhrverband's plants since 2002 by applying a moving bed system. To gain additional experience in operating this process, another full scale plant was modified in 2007 by integration of deammonification, using a SBR system with suspended biomass based on the DEMON(®) control scheme. By using seeding sludge from Strass WWTP in Austria, start-up has been achieved within only 1 day. After stable operation for several months, increasing nitrate concentrations were observed in the effluent of the system indicating growing activity of nitrite oxidising bacteria (NOB). Following severe process deterioration, it was decided to re-start the system again but the same behaviour, i.e. increasing levels of nitrate, was observed once again. Several approaches were used to suppress NOB organisms in full-scale without success, e.g. low oxygen levels and high free ammonia concentrations. Finally, the reduction of the aerobic cycle length during intermittent aeration down to 8 min, followed by an anoxic mixing period of only 18 min was successful in inhibiting the activity of NOB organisms, most probably due to their elevated lag-phase compared with ammonium oxidising bacteria. Today, nitrogen elimination that has been stabilised at more than 80% at a daily volumetric loading rate of 0.5 kg N/(m³ d). The total costs amount to €2.3/kg N(eli).

1,3-Dipolar addition of diazocyclopropane to eudesmane-type methylidene lactones and thermolysis of the resulting spiro-fused pyrazolines

Reactions of alanto-, isoalanto-, and alloalantolactones, which are unsaturated eudesmane-type lactones, with diazocyclopropane generated in situ from N-cyclopropyl-N-nitrosourea under the action of sodium methoxide proceed alike, are highly regio- and stereoselective, and always give spiro-fused pyrazolines via cycloaddition to the exocyclic double bond of the methylidene group of the lactone ring. Their thermolysis at 195–210 °C results in elimination of molecular nitrogen, mainly yielding spiropentane-containing lactones. Minor thermolysis products (10–12%) are isomeric 13-cyclopropyl lactones.

Air embolism and blunt chest trauma

To the Editor, I read with interest the case reported in the Journal describing the events surrounding the death of a child from unilateral blunt chest trauma due to coronary and cerebral arterial gas embolism (AGE). The authors used high frequency oscillatory ventilation (HFOV) for oxygenation with a mean airway pressure of 18 cmH2O because the child’s hemoptysis raised concerns regarding airway-vascular connections. Any form of positive pressure ventilation, including HFOV, may contribute to air embolism when pulmonary vessels are damaged. The authors mentioned methods to ensure ‘‘separation of the lungs and the air from the blood’’, and this could have been achieved using a double-lumen endotracheal tube or bronchial blocker (DLT/BB). This and other reported cases suggest strongly that isolation of a lung or lobe is essential if positive pressure ventilation is used in such circumstances. Prompt hyperbaric oxygen treatment (HBOT) is indicated for AGE and may be undertaken with a DLT/BB, but HFOV would be difficult and potentially dangerous in a hyperbaric chamber. At six atmospheres absolute (ATA) pressure, bubble volume decreases immediately to 17% (Boyles Law) with potential for rapid clinical improvement. Despite HFOV with 100% oxygen, sufficient nitrogen likely remained in the patient’s lungs to constitute a substantial portion of the embolizing gas. Oxygen solubility, hemoglobin-binding, and metabolism would result in diffusion out of bubbles, but insoluble inert nitrogen gas may persist for days. Hyperbaric oxygen treatment (using U.S. Navy Decompression Table 6A, perhaps with 50:50 oxyhelium while at six atmospheres absolute [ATA]) to reduce cerebral (seizures) and pulmonary oxygen toxicity while eliminating nitrogen from the inspired gas increases the diffusion gradient for enhanced nitrogen elimination and may help to deliver oxygen to ischemic tissues. Additional benefits may result from HBOT effects on the response to endothelial and systemic inflammatory reactions to the gastissue interface. At three ATA oxygen (three ATA on100% oxygen or six ATA on 50% oxygen), arterial pO2 may exceed 2,000 mmHg with normal lungs. Therefore, even with a 50% shunt and one-lung ventilation, oxygenation inside the chamber is most unlikely to be inadequate. Low pressure continuous positive airway pressure (5 cmH20) to the unventilated lung could be implemented easily if oxygenation were inadequate; even so, it could have a small risk. However, unless vascular entry of inert gas is stopped using DLT/BB, treatment cannot succeed. This profoundly difficult tragic case suggests low airway pressure HFOV is contraindicated when air is entering the pulmonary vessels, and future optimal management for such cases is DLT/BB and prompt HBOT.

Long-term behaviour of a two-stage CW system regarding nitrogen removal

In the first two years of operation a nitrogen removal efficiency of 53% and a high average elimination rate of 1,000 g N m(-2) yr(-1) could be observed for a two-stage vertical flow (VF) constructed wetland (CW) system. The two-stage system consists of two VF beds with intermittent loading operated in series, each stage having a surface area of 10 m2. The first stage uses sand with a grain size of 2-3.2 mm for the 50 cm main layer and has a drainage layer that is impounded; the second stage sand with a grain size of 0.06-4 mm and a conventional drainage layer (with free drainage). The two-stage VF system was designed for and operated with an organic load of 40 g COD m(-2) d(-1) (i.e. 2 m2 per person equivalent). Data from the following years of operation showed that from the third year nitrogen elimination increased and stabilized. The median values of the nitrogen elimination rate in the first five years of operation have been 3.51, 2.76, 4.20, 3.84 and 4.07 g N m(-2) d(-1), the median value of the last three years being 3.8 g N m(-2) d(-1) and 1,380 g N m(-2) yr(-1), respectively, and the nitrogen removal > 60%. It can be assumed that the vegetation as well as the biofilm development in the two-stage VF CW system plays the major role for the enhancement of the nitrogen elimination rate.

Comparison of nitrogen elimination rates of different constructed wetland designs

In this paper the nitrogen elimination rates of different constructed wetland (CW) designs reported in literature are compared with those obtained for outdoor and indoor 2-stage vertical flow (VF) systems. The outdoor system is located about 150 km west of Vienna. Both stages are planted with Phragmites australis and the system has been operated for 4 years continuously. During this period the average value of the nitrogen elimination rate was 3.30 g N m(-2) d(-1). The indoor system comprises three parallel operated 2-stage VF systems and is located in the technical lab hall at BOKU University. The design of the indoor system resembles the outdoor system. However, there are a few differences: (1) the indoor systems are not planted, and (2) different filter media have been used for the main layer of the first stages. With the indoor system the highest nitrogen elimination rate achieved was 2.24 g N m(-2) d(-1) for the system with zeolite and impounded drainage layer. Similar results have been found in France for treating raw wastewater with VF and horizontal flow (HF) beds in series with nitrogen elimination rates of 1.89 and 2.82 g N m(-2) d(-1) for differently designed HF beds. The highest nitrogen elimination rates of 15.9 g N m(-2) d(-1) reported were for pilot-scale VF CWs treating high-strength synthetic wastewater (total nitrogen of 305 mg L(-1) in the influent) in Thailand. It has been shown that the outdoor two-stage VF CW system has one of the highest nitrogen elimination rates of CWs treating domestic wastewater.

Reactions of 4-phenyl-1,2,4-triazoline-3,5-dione with 2-pyrazolines

4-Phenyl-1,2,4-triazoline-3,5-dione (PTAD) acts as an efficient Michael acceptor in reactions with 1-unsubstituted 2-pyrazolines, giving substituted (3,5-dioxo-4-phenyl-1,2,4-triazol-idin-1-yl)-1-pyrazolines in quantitative yields. Through elimination of molecular nitrogen, the latter are easily transformed into the corresponding cyclopropanes. A reaction of methyl 5-methyl-2-pyrazoline-5-carboxylate with a twofold excess of PTAD leads to an intermediate bisadduct, which undergoes dediazotization to form a 1,3,5-triazabicyclo[3.3.0]octane-2,4-dione derivative. 1-Substituted 2-pyrazolines also add to PTAD with the exception that the 2-pyrazoline structure is retained in the product because of the migration of the C(3)H proton to PTAD.

Nitrogen Washout During a Fatty Meal While Breathing Nitrogen-Free Gas at Sea Level

The reasons for wide variability in the incidence of decompression sickness (DCS) are not well known, but diet may play a role. The hypothesis of the present study was that raising plasma triglycerides via a high-fat meal would increase the rate of nitrogen washout and, therefore, might be a useful adjunct when denitrogenation is used to reduce the likelihood of DCS in diving and exposure to altitude. Nitrogen elimination was measured for 125 min in 10 subjects by gas chromatography while they breathed a normoxic argon-oxygen mixture at sea level. Measurements were performed on separate days after high-fat and control, low-fat meals. The high-fat meal increased blood triglycerides by 236 +/- 86% while there was no significant change after the control meal. Despite causing a significant increase in cardiac output (21.6 +/- 13.8%), there was no difference in nitrogen elimination after high-fat (817.4 +/- 233.1 ml) vs. control (828.3 +/- 180.5 ml). These data suggest that raising blood triglycerides via a high-fat meal does not affect the rate of whole-body nitrogen elimination. The lack of effect of the increase in cardiac output may be due to an increased blood flow to the gastrointestinal tract being negated by decreased blood flow in other vascular beds.

Regime Shift and Microbial Dynamics in a Sequencing Batch Reactor for Nitrification and Anammox Treatment of Urine

The microbial population and physicochemical process parameters of a sequencing batch reactor for nitrogen removal from urine were monitored over a 1.5-year period. Microbial community fingerprinting (automated ribosomal intergenic spacer analysis), 16S rRNA gene sequencing, and quantitative PCR on nitrogen cycle functional groups were used to characterize the microbial population. The reactor combined nitrification (ammonium oxidation)/anammox with organoheterotrophic denitrification. The nitrogen elimination rate initially increased by 400%, followed by an extended period of performance degradation. This phase was characterized by accumulation of nitrite and nitrous oxide, reduced anammox activity, and a different but stable microbial community. Outwashing of anammox bacteria or their inhibition by oxygen or nitrite was insufficient to explain reactor behavior. Multiple lines of evidence, e.g., regime-shift analysis of chemical and physical parameters and cluster and ordination analysis of the microbial community, indicated that the system had experienced a rapid transition to a new stable state that led to the observed inferior process rates. The events in the reactor can thus be interpreted to be an ecological regime shift. Constrained ordination indicated that the pH set point controlling cycle duration, temperature, airflow rate, and the release of nitric and nitrous oxides controlled the primarily heterotrophic microbial community. We show that by combining chemical and physical measurements, microbial community analysis and ecological theory allowed extraction of useful information about the causes and dynamics of the observed process instability.

Quantitative Analysis of NOx Reduction in Oxy-Coal Combustion

The conversion ratios of fuel-N to NO were investigated during combustion of two Chinese bituminous coals in four different atmospheres (O2/N2, O2/Ar, O2/CO2, and O2/RFG) in an electrically heated drop-tube furnace at elevated temperatures (1273−1673 K). The oxygen concentration in the inlet gas was changed from 8% to 40%. The recycling ratio of flue gas ranged from 0.4 to 0.8. Through comparing the conversion ratios of fuel-N to NO among the four different atmospheres, the contributions of elimination of atmospheric nitrogen, high CO2 concentration in the furnace, and reduction of recycled-NOx to the reduction of total NOx in oxy-coal combustion were investigated. Results show that the contribution of recycled-NO reduction was dominant. It contributed 45−70% of the total reduction of NOx. It decreased with oxygen concentration in the inlet gas and increased with flue gas recycling ratio. The contribution of elimination of atmospheric nitrogen accounted for 12−25% and had a trend opposite that observed for the recycled-NO reduction. The contribution of the high CO2 concentration in the furnace accounted for 18−33%. It initially increased with oxygen concentration, and then decreased as the oxygen concentration reached and exceeded 21%. The influence of temperature on the contributions of elimination of atmospheric nitrogen, high CO2 concentration in the furnace, and reduction of recycled-NOx to the reduction of total NOx was complex. It depended on combustion conditions and the type of employed coals.

Nitrite effect on ammonium and nitrite oxidizing processes in a nitrifying sludge

Nitrite accumulation can be undesirable in nitrifying reactors used for the biological elimination of nitrogen from wastewaters because the ammonium oxidation process was seen to be inhibited. There is a need to better understand the effects of nitrite on both ammonium and nitrite oxidizing processes. In this paper, the effect of nitrite on the nitrifying activity of a sludge produced in steady-state nitrification was evaluated in batch cultures. At 25 mg N/l of added nitrite, nitrification was successfully carried out. Addition of higher nitrite concentrations to nitrifying cultures (100 and 200 mg N/l) provoked inhibitory effects on the nitrification respiratory process. Nitrite at 100 and 200 mg N/l induced a significant decrease in the values for nitrate yield (−20% and −34%, respectively) and specific rate of nitrate formation (−26% and −67%, respectively), while the ammonium consumption efficiency kept high and the specific rate of ammonium oxidation did not significantly change. This showed that the nitrite oxidizing process was more sensitive to the presence of nitrite than the ammonium oxidizing process. These results showed that as a consequence of nitrite accumulation in nitrification systems, the activity of the nitrite oxidizing bacteria could be more inhibited than that of the ammonium oxidizing bacteria, provoking a higher accumulation of nitrite in the medium.

A selective synthesis of enamines versus aziridines

Abstract The reaction of 10‐azidoacetyl‐10H‐phenothiazine with olefinic dipolarophiles depends on the reaction temperature. In refluxing toluene, a mixture of enamine and aziridine is formed in 3:1 ratio. The reaction mechanism appears to involve a Michael‐type addition of the nucleophilic N1 azide atom to the olefinic double bond. In chloroform, a cycloaddition reaction takes place with the formation of a 4,5‐dihydro‐1,2,3‐triazole. The heating of dihydrotriazoles in toluene is accompanied by nitrogen elimination leading to a mixture of enamine and aziridine in 1:3 ratio. J. Heterocyclic Chem., 2011.

ChemInform Abstract: Synthesis of a Pyrimidine by Elimination of Nitrogen from a Triazolo-( 4,5-d)pyrimidine.

Abstract Treatment of 3-phenyl-1,2,3-triazolo[4,5- d ]pyrimidine-5,7-dithione with butyl lithium and an alkylating agent afforded a bis-alkylated pyrimidine, incorporating one butyl side chain.

ChemInform Abstract: A General, One-Pot Method for the Synthesis of 2-Substituted Oxazoles.

Abstract The reaction of 2-trimethylsilyl-1,2,3-triazole with acid chlorides readily forms triazole amides. The triazole amides, when heated to 150°C in sulfolane, rearrange with the elimination of nitrogen to give 2-substituted oxazoles in high yields. The oxazole synthesis is general, and can be carried out in one-pot.

ChemInform Abstract: Azomethine Imines in Four- and Five-Membered Rings: Stable Cyclic Valence Isomers of an α-(Phenyldiazenyl)ketocarbene.

The expected Wolff rearrangement of the ketocarbene intermediate 2, formed upon rhodium(II)-catalyzed elimination of nitrogen from diazoketone 1, does not occur. Instead, by incorporation of the neighboring diazene group the surprisingly stable, crystalline azomethine imines 3 and 4 are formed as cyclic valence isomers of 2. Compound 4, which contains a five-membered ring, is the first representative of a carba-sydnone and can also be obtained by acid-catalyzed isomerization of 3 at 50-70°C.