Ammonia Feed Research Articles

Oxidative denitrogenation of liquid fuel over W2N@carbon catalyst derived from a phosphotungstinic acid encapsulated metal–azolate framework

Tungsten nitride-incorporated carbon (W2N(x)@C) was firstly prepared via pyrolysis of a newly developed phosphotungstic acid-loaded metal-azolate framework-6, PTA(x)@MAF-6 s. The obtained (without ammonia feeding) W2N(x)@C materials, were utilized as catalysts for oxidative denitrogenation (ODN) of fuels. The W2N(x)@C materials, especially W2N(15)@C, under ultrasound (US) irradiation was found to be a very efficient catalyst for oxidative removal of various organo-nitrogen compounds (ONCs). Importantly, the W2N(15)@C showed around 80–147 times turnover frequency those of reported catalysts for stubborn carbazole oxidation. Electron density on the N-atom of the ONCs has a dominant role in the oxidation. The oxidation mechanism was suggested mainly based on the calculated electron density of the reactants and analysis of major intermediates/products. Moreover, the US-assisted ODN was progressed by both non-radical and radical paths, as supported by the electron spin resonance and radical scavenger experiments. The recyclability of the catalyst in the US irradiative ODN was also confirmed.

Genomic and Physiological Characteristics of a Novel Nitrite-Oxidizing Nitrospira Strain Isolated From a Drinking Water Treatment Plant.

Nitrite-oxidizing bacteria (NOB) catalyze the second step of nitrification, which is an important process of the biogeochemical nitrogen cycle and is exploited extensively as a biological nitrogen removal process. Members of the genus Nitrospira are often identified as the dominant NOB in a diverse range of natural and artificial environments. Additionally, a number of studies examining the distribution, abundance, and characterization of complete ammonia oxidation (comammox) Nitrospira support the ecological importance of the genus Nitrospira. However, niche differentiation between nitrite-oxidizing Nitrospira and comammox Nitrospira remains unknown due to a lack of pure cultures. In this study, we report the isolation, physiology, and genome of a novel nitrite-oxidizing Nitrospira strain isolated from a fixed-bed column at a drinking water treatment plant. Continuous feeding of ammonia led to the enrichment of Nitrospira-like cells, as well as members of ammonia-oxidizing genus Nitrosomonas. Subsequently, a microcolony sorting technique was used to isolate a novel nitrite-oxidizing Nitrospira strain. Sequences of strains showing the growth of microcolonies in microtiter plates were checked. Consequently, the most abundant operational taxonomic unit (OTU) exhibited high sequence similarity with Nitrospira japonica (98%) at the 16S rRNA gene level. The two other Nitrospira OTUs shared over 99% sequence similarities with N. japonica and Nitrospira sp. strain GC86. Only one strain identified as Nitrospira was successfully subcultivated and designated as Nitrospira sp. strain KM1 with high sequence similarity with N. japonica (98%). The half saturation constant for nitrite and the maximum nitrite oxidation rate of strain KM1 were orders of magnitude lower than the published data of other known Nitrospira strains; moreover, strain KM1 was more sensitive to free ammonia compared with previously isolated Nitrospira strains. Therefore, the new Nitrospira strain appears to be better adapted to oligotrophic environments compared with other known non-marine nitrite oxidizers. The complete genome of strain KM1 was 4,509,223 bp in length and contained 4,318 predicted coding sequences. Average nucleotide identities between strain KM1 and known cultured Nitrospira genome sequences are 76.7–78.4%, suggesting at least species-level novelty of the strain in the Nitrospira lineage II. These findings broaden knowledge of the ecophysiological diversity of nitrite-oxidizing Nitrospira.

Effective inhibition prevention strategy for the enrichment of anammox bacteria with low concentrations of substrates at 25 °C

This work aimed to enrich anaerobic ammonia oxidation (anammox) bacteria, which can be potentially used in mainstream wastewater treatment systems for enhancing economical autotrophic nitrogen removal. Anammox bacteria were enriched in a sequencing batch reactor (SBR) with continuous feeding of ammonia and nitrite at 25 ± 2 °C. The results indicated that the concentrations of ammonia and nitrite at each moment ranged from 0 mg/L to 30 mg/L and 0 mg/L to 10 mg/L respectively, by adjusting the feed stream supply rate based on the reaction rate. Furthermore, the free ammonia (FA) and free nitrous acid (FNA) concentrations were controlled systematically at desired low levels of 0–1.96 mg/L and 0–2.94 μg/L respectively, to prevent substrate inhibition on anammox bacteria. Candidatus Kuenenia-anammox bacteria were highly enriched for approximately 4 months, as demonstrated by the proportion increased from a negligible value to 17.60 %. This promising operational mode proposed an available choice to enrich various microorganisms of expected functions, to accelerate reactor start-up and enhance biological efficiency.

Vacuum membrane distillation multi-component numerical model for ammonia recovery from liquid streams

In this work, a modelling research on the separation of ammonia gas from liquid streams via vacuum membrane distillation (VMD) is conducted. An experimentally validated multi-component simulation model of a flat sheet VMD module is developed by implementing heat and mass balances through the feed, membrane and permeate channels. Continuous removal of the gases transferred through the membrane at a constant pressure in the permeate channel is assumed. The transport mechanisms through the pores under VMD conditions for both volatiles are discussed. Under studied VMD conditions and the typical concentration range in waste waters (i.e. 1-10 g TAN l-1), it is observed that none of the two volatile components (ammonia and water) is preferentially transported. The resulting VMD performance is simulated and evaluated in terms of total transmembrane flux, ammonia flux, ammonia selectivity and thermal energy consumption. The model was validated experimentally and showed good agreement, with an average relative error <10%. The experiments were performed with a solution of (NH4)2SO4 in a laboratory set up under controlled conditions. The simulation, as well as the experimental results, emphasize the existing trade-off between the flux (JNH3) and selectivity (SNH3) of ammonia. Increasing feed temperature and decreasing vacuum pressure results in higher JNH3 but lower SNH3. Moreover, those parameters that enhance the heat transfer through the membrane (i.e. feed temperature, pore size, porosity, vacuum pressure, etc.) promote the water flux over ammonia. While those parameters that enhance mixing and the ammonia mass transfer in the feed (i.e. feed velocity, spacer geometry, pH, ammonia feed concentration, etc.) promote the ammonia flux over water. The only operating parameter which enhances simultaneously the JNH3 and SNH3 is the feed velocity, indicating that the spacer geometry can play an important role in designing VMD modules for ammonia separation. VMD can extract and concentrate ammonia on the permeate side at a low specific thermal energy consumption. However, the JNH3 is greatly limited by the feed ammonia concentration which will ultimately determine the cost-effectiveness of the recovery. The trends described by the model are in agreement with other authors’ observations and give insight into the mechanisms dominating ammonia separation via VMD and its performance limits.

PENERAPAN TEKNOLOGI AMONIASI JERAMI SEBAGAI PAKAN ALTERNATIF SAPI POTONG DI KENAGARIAN SUNGAI KUNYIT, SOLOK SELATAN

The feed is an essential requirement in cattle farming. The need for cattle feed reaches 80% of the cost of raising livestock. To reduce the cost of this feed, we need an alternative feed at a low price. Ammonia straw is one way to process agricultural waste products into alternative feed used for beef cattle feed. This ammonia feed technology is an efficient method for improving the quality of straw as animal feed. The objectives of this activity are 1. to increase the knowledge and understanding of cattle breeders in the use of straw waste as an alternative feed for cattle for feed cost efficiency, 2. to increase the productivity of cattle through straw ammonia feed technology, and 3. to increase the welfare of breeders by utilizing rice straw waste as feed. Livestock. The method used in this activity is counseling, demonstration of straw ammonia, and evaluating the application of straw ammonia technology as an alternative feed source for breeders. The extension method is carried out by giving lectures on the use and processing of straw waste as animal feed. Meanwhile, a demonstration of processing straw waste as ammoniated feed. The targets of this activity are farmers and the community in Kenagarian Sungai Kunyit. The results obtained from this activity, activity participants can gain knowledge and understanding in processing ammonia feed as an alternative feed. The use of ammonia feed can overcome the shortage of animal feed in the dry season/famine, overcoming environmental pollution from agricultural waste/straw. Ammoniated straw feed can also increase the digestibility of livestock so that it can increase livestock productivity. Cattle farmers in Kenagarian Sungai Kunyit can make their straw ammonia feed. Ammoniated feed can reduce feed costs, and livestock is more profitable.

Synthesis of piperacillin with low impurity content using a new three-feed membrane dispersion microreactor

The synthesis of piperacillin is very sensitive to the mixing effect and the pH of the system. Because of poor micro-mixing and imprecise pH control in the ampicillin chloride method using the traditional reactor, the impurity content of piperacillin does not meet the production standard. Therefore, a novel three-feed membrane dispersion microreactor was proposed and used to synthesize piperacillin, in which ampicillin was first mixed with 4-ethyl-2,3-dioxo-1-piperazine carbonyl chloride (EDPC) and then mixed with ammonia water under rapid and intense mixing conditions. The process of ampicillin circulation and slow addition of the EDPC also contributed to stabilizing the pH value. The effects of the distance between the ammonia feed and the EDPC feed, pH, reaction temperature, EDPC ratio, and circulation flow rate on the content of piperacillin and impurities were investigated. The piperacillin content of the condensation solution reached ~94.90% within 10 min under the optimal conditions in the microreactor, but the content only reached 91.06% in 60 min in the traditional tank; more importantly, the content of the key impurities D and E decreased from 0.340% to 0.080%, and 0.176% to 0.035%, respectively. Subsequent processes were carried out to obtain the final piperacillin product, where the average yield was around 93.99%; the purity was generally above 99.7%; the content of impurity D was generally less than 0.1%, and the content of impurity E was less than 0.05%, meeting the guidelines of the pharmacopoeia and antibiotic impurity.

Usage of nutrient Medium Based on Dry Hydrolysate of Casein in Manufacturing Bivalent Chemical Cholera Vaccine

Objective of the study was to select the standardized substrate containing dry hydrolysate of casein for preparation of nutrient medium utilized for manufacturing bivalent chemical cholera vaccine under submerged cultivation of cholera vibrio strains in fermenters. Materials and methods . We used Vibrio cholerae O1 strains of classical biovar: strain 569B Inaba and strain M-41 Ogawa. Examined were two dry substrates of the medium: enzymatic hydrolysate of casein, Type I Himedia (India) and pancreatic hydrolysate of casein, produced by the State Scientific Center of Applied Microbiology and Biotechnology (Russian Federation). Produced under laboratory conditions at the premises of the RusRAPI “Microbe” medium was used as a control. Submerged cultivation was conducted in bioreactors during (9±1) h with aeration and automatic feeding of glucose and ammonia. Production of protective antigens was measured applying immunochemical and biological methods. Results and discussion . It is demonstrated that submerged cultivation of cholera vibrio production strains on nutrient media under study provides for synthesis of protective antigens the parameters of which comply with the requirements of normative documentation. More standardized and higher indicator values of the target product are ensured by cultivation of producer strains on nutrient medium with a substrate from dry enzymatic hydrolysate of casein, containing (1.5±0.1) g/l of amino nitrogen for the strain V. cholerae M-41 and (2±0.1) g/l – for V. cholerae 569 B. Transition to the use of standardized dry protein components of cultivation media does not lower the quality of the chemical cholera vaccine, but allows for the reduction of cost price and duration of technological process.

Investigation of the fate of nitrogen in chemical looping combustion of gaseous fuels using two different oxygen carriers

The influence of nitrogenous fuel impurities in a 120 kWth chemical looping combustion pilot unit was investigated. Two oxygen carriers were used. An in industrial scale produced perovskite type CaMn0·775Mg0·1Ti0·125O3-δ, called C28 and a copper based oxygen carrier (Cu15) prepared by impregnation were applied. Natural gas was used as fuel and ammonia (NH3) were added as a model NOX precursor up to a fuel-N content of 1.4 wt%, to investigate the path of nitrogen and emissions of nitrogen oxides. The exhaust gas streams of air and fuel reactor were analyzed against NH3 and NOX. The two oxygen carriers performed differently in the presence of NH3 in the fuel feed. While the general fuel conversion performance of both oxygen carriers were not affected, the NH3 conversion with C28 was only around 72% in the fuel reactor, full NH3 conversion was measured with Cu15. During the experiments with C28, NOX emissions in form of NO occurred in the fuel reactor, opposite to this no NOX have been detected while using Cu15. During all experiments no NOX was observed in the air reactor exhaust gas stream. A regeneration during CLC operation after switching off the ammonia feed was possible.

Ammonia as hydrogen carrier for realizing distributed on-site refueling stations implementing PEMFC technology

Ammonia is a particularly promising hydrogen carrier due to its relatively low cost, high energy density, its liquid storage and to its production from renewable sources. Thus, in recent years, great attention is devoted to this fuel for realizing next generation refueling stations according to a carbon-free energy economy. In this paper a distributed onsite refueling station (200 kg/day of hydrogen filling 700-bar HFCEVs (Hybrid Fuel Cell Electric Vehicles) with about 5 kg of hydrogen in 5 min), based on ammonia feeding, is studied from the energy and economic point of views. The station is designed with a modular configuration consisting of more sections: i) the hydrogen production section, ii) the electric energy supplier section, iii) the compression and storage section and the refrigeration/dispenser section. The core of the station is the hydrogen production section that is based on an ammonia cracking reactor and its auxiliaries; the electric energy demand necessary for the station operation (i.e. the hydrogen compression and refrigeration) is satisfied by a PEMFC (Proton-Exchange Membrane Fuel Cell) power module. Energy performance, according to the hydrogen daily demand, has been evaluated and the estimation of the levelized cost of hydrogen (LCOH) has been carried out in order to establish the cost of the hydrogen at the pump that can assure the feasibility of this novel refueling station.

Preparation of FePO4•2H2O from LiFePo4 mixed with LiNixCoyMn1-x-yO2 waste material

A method for preparing battery grade FePO4?2H2O from LiFePO4 and LiNixCoyMn1-x-yO2 mixed waste is proposed. The optimum leaching conditions included: temperature of 50?C, 3:1 liquid?solid mass ratio, 3.6 HCl/FePO4?2H2O mole ratio, 0.75 H2O2/FePO42H2O mole ratio, and 2 h reaction time. The solution obtained from the leaching waste material was diluted to a 1.0 M Fe concentration, then transferred to an 1 L beaker, where temperature, pH, complexing agent, ammonia addition rate and feeding mode were studied in order to determine their effects on the precipitation, particle size and morphology of FePO4?2H2O. High precipitation rate of Fe with low percentages of Al, Ni, Co, Mn in the FePO4?2H2O is achievable when precipitation is performed at a temperature of 85?C, pH of 2.0, and 20 g L-1 complexing agent. Furthermore, it was observed that a slow addition of ammonia and a flow feeding method contributed to the production of FePO4?2H2O, with small particle sizes and a flake morphology.

Analysis of rapid culture of high-efficiency nitrifying bacteria and immobilized filler application for the treatment of municipal wastewater.

Activated sludge from the A2/O process in a wastewater treatment plant (WWTP) was used as the seed sludge for enrichment to achieve faster growth of nitrifying bacteria and higher nitrification efficiency of the filler made by nitrifying bacteria. The bacterial community was enriched in a self-circulating bacteria culture tank by a continuous ammonia feeding mode. The study found that the nitrifying bacteria community was enriched in 38 days with the ammonia oxidation rate of approximately 275.58 mg (L h)−1. High-throughput sequencing demonstrated that Nitrosomonas belonging to ammonia-oxidizing bacteria (AOB) was predominant in the sludge after 38 days at a ratio extending from 0.43% to 61.91%. The enriched sludge was used as the bacterial source and the immobilization was carried out with polyvinyl alcohol (PVA). After the recovery culture, the ammonia oxidation rate of the filler was up to 44.61 mg (L h)−1 for the treatment of municipal wastewater, and the effluent ammonia was below 1 mg L−1, indicating that the immobilized filler is effective for municipal wastewater nitrification. Scanning electron microscope (SEM) observations showed that immobilized fillers were highly porous and bacteria adhered to the network structure, demonstrating that the filler provided a good growth microenvironment for microorganisms.

XAS investigation of silica aerogel supported cobalt rhenium catalysts for ammonia decomposition.

The implementation of ammonia as a hydrogen vector relies on the development of active catalysts to release hydrogen on-demand at low temperatures. As an alternative to ruthenium-based catalysts, herein we report the high activity of silica aerogel supported cobalt rhenium catalysts. XANES/EXAFS studies undertaken at reaction conditions in the presence of the ammonia feed reveal that the cobalt and rhenium components of the catalyst which had been pre-reduced are initially re-oxidised prior to their subsequent reduction to metallic and bimetallic species before catalytic activity is observed. A synergistic effect is apparent in which this re-reduction step occurs at considerably lower temperatures than for the corresponding monometallic counterpart materials. The rate of hydrogen production via ammonia decomposition was determined to be 0.007 molH2 gcat-1 h-1 at 450 °C. The current study indicates that reduced Co species are crucial for the development of catalytic activity.

Impact of sintering temperature and pH of feed solution on adsorptive removal of ammonia from wastewater using clinoptilolite based hollow fibre ceramic membrane

This work presented the adsorptive hollow fibre ceramic membrane (HFCM) derived from clinoptilolite for effective removal of ammonia from water. The effect of different sintering temperature of HFCM (900–1150 °C) and pH of ammonia feed solution (pH 2 – pH 11) were examined. The membranes were fully characterized by the scanning electron microscopy (SEM), mechanical strength, water permeability, X-ray diffraction (XRD), X-ray fluorescence (XRF) and zeta potential to get the better understand of its physicochemical properties and ammonia adsorption mechanism relationship. The best fabricated HFCM was produced when sintered at 1050 °C with 54.20 MPa and 228.25 L/m2·h of mechanical strength and water permeability, respectively. The adsorption kinetics behavior showed that the adsorption process was best fitted to pseudo-second order kinetic model with 12.468 mg/g adsorption capacity. The morphology and negatively charged surface of the HFCM have significantly contributed to the high adsorption of the ammonia (96.67 %) from the feed solution. The maximum adsorption activities were achieved at pH 7 with 0.4 g/L HFCM within 120 min of residence time. The results indicated that the adsorptive HFCM have significant potential to be developed as simple, economical and effective remover for the ammoniacal wastewater treatment.

Tungsten Nitride, Well-Dispersed on Porous Carbon: Remarkable Catalyst, Produced without Addition of Ammonia, for the Oxidative Desulfurization of Liquid Fuel.

Polyanilines (pANIs), loaded with phosphotungstic acid (PTA), are pyrolyzed to get WO3 or W2 N (≈6 and ≈7 nm, respectively), which is well-dispersed on pANI-derived porous carbons (pDCs). Depending on the pyrolysis temperature, WO3 /pDC, W2 N/pDC, or W2 N-W/pDCs could be obtained selectively. pANI acts as both the precursor of pDC and the nitrogen source for the nitridation of WO3 into W2 N during the pyrolysis. Importantly, W2 N could be obtained from the pyrolysis without ammonia feeding. The obtained W2 N/pDC is applied as a heterogeneous catalyst for the oxidative desulfurization (ODS) of liquid fuel for the first time, and the results are compared with WO3 /pDC and WO3 /ZrO2 . The W2 N/pDC is very efficient in ODS with remarkable performance compared with WO3 /pDC or WO3 /ZrO2 , which is applied as a representative ODS catalyst. For example, W2 N/pDC shows around 3.4 and 2.7 times of kinetic constant and turnover frequency (based on 5 min of reaction), respectively, compared to that of WO3 /ZrO2 . Moreover, the catalysts could be regenerated in a facile way. Therefore, W2 N/pDC could be produced facilely from pyrolysis (without ammonia feeding) of PTA/pANI, and W2 N, well-dispersed on pDC, can be suggested as a very efficient oxidation catalyst for the desulfurization of liquid fuel.

Thermal conductivity and acoustical investigation of SnO2 nanofluids using ultrasonic velocity measurements

In the current work, tin oxide (SnO2) nanoparticles (NPs) are being synthesized by sol–gel method by varying reaction parameter such as ammonia feed rate. The synthesized NPs have also characterized by X-ray powder diffraction (XRD), high resolution scanning electron microscopy (HRSEM) and UV–visible spectroscopy. SnO2 nanofluid is being prepared by using of synthesized nanoparticles with the base fluid as water along with the help of sonication. The ultrasonic velocity and density values are being measured in five different concentrations of SnO2 nanofluids at different temperatures ranging from 298.15 K to 323.15 K.The thermal conductivity values were evaluated from the experimental data. The intermolecular interactions responsible for the changes in thermal conductivity with respect to the concentration and the temperature have also been conferred and the thermal conductivities of nanofluids were also calculated through the ultrasonic methodology and the results have also been compared with the flash laser method, derived experimentally.

A viable membrane reactor option for sustainable hydrogen production from ammonia

Conventional hydrogen production from ammonia is both energy and process intensive, requiring high temperature and independent purification units. Here, we present a compact process of energy conversion from NH3 to electricity using a novel membrane reactor, comprised of a dense metallic Pd/Ta composite membrane and Ru/La-Al2O3 pellet catalysts, and a fuel cell unit. The fabricated Pd/Ta composite membrane, having ca. 5 times higher H2 permeability than conventional Pd-Ag membranes, can both lower NH3 dehydrogenation temperature and completely remove an additional hydrogen purification unit. Compared to a packed-bed reactor without membrane, ammonia conversion improves by 75 and 45%, respectively at 425 and 400 °C, and >99.5% of conversion is achieved at 450 °C under pressurized ammonia feed of 6.5 bar. Main barriers of practical application of Pd/Group V metals as a composite hydrogen permeable membrane, embrittlement and durability issues, are overcome owing to pertinent operating temperatures (400–450 °C) of ammonia dehydrogenation coupled with membrane separation. Finally, as-separated hydrogen with <1 ppm of NH3 is provided directly to a polymer electrolyte membrane fuel cell, showing no performance degradation for an extended time of operation. The combined results suggest a feasible and less energy/process intensive option for producing hydrogen or electricity from ammonia.

Gas-liquid reactive crystallization kinetics of 2,4,6-triamino-1,3,5-trinitrobenzene in the semi-batch procedure

2,4,6-Triamino-1,3,5-trinitrobenzene is the attractive insensitive high energetic material used extensively in the military and civil fields. Combined with the double-films theory, the global gas-liquid chemical reaction kinetics of 2,4,6-triamino-1,3,5-trinitrobenzene was developed by means of the infinitesimal material balance calculation. The raw material concentration and reactive temperature effects on the crystallization of 2,4,6-triamino-1,3,5-trinitrobenzene were investigated by the batch experiments. The reactive crystallization kinetics associated ammonia feeding rate of 2,4,6-triamino-1,3,5-trinitrobenzene, including nucleation as well as crystal growth, was systematically investigated in the heterogonous semi-batch procedure. The nucleation and crystal growth kinetic exponents were estimated by the linear least-squares method. The crystallization kinetic results indicated that nucleation rate strongly increased but liner growth rate decreased with the increasing of ammonia feeding rate. In terms of manufacturing coarse 2,4,6-triamino-1,3,5-trinitrobenzene, it was found that a slow ammonia feeding rate and a low raw material concentration were feasible under the present experimental conditions.

The impact of ammonia feed distribution on the performance of a fixed bed membrane reactor for ammonia decomposition to ultra-pure hydrogen

Abstract In this study, the influence of distribution of ammonia feed along the height of a fixed bed membrane reactor (FBMR) for ammonia decomposition to hydrogen is investigated to understand the leverage of this approach. A rigorous heterogeneous model with verified kinetics is implemented to simulate the reactor. The simulation results indicate that the application of a distributed ammonia feed with equal distribution of injection points resulted in a 17.45% improvement in hydrogen production rate at a low temperature of 800.0 K over a FBMR without feed distribution. In the parameter space of this study, it has been shown that the ammonia conversion is sensitive to the number of distribution points and has an optimal value. It is found that the implication of the optimum number of injection points can substantially reduce the length of the reactor by 75.0% to achieve 100.0% ammonia conversion. The hydrogen reversal permeation phenomenon is observed at a low pressure and the upper part of the reactor. A novel configuration of a FBR and a FBMR with feed distribution is proposed for efficient production of ultra-pure hydrogen at a relatively low pressure. The critical reactor length ratio has been provided for this configuration.

Effect of free ammonia inhibition on NOB activity in high nitrifying performance of sludge.

The inhibition of free ammonia (FA) on nitrite-oxidizing bacteria (NOB) was investigated using an enriched NOB community with high nitrifying performance. A continuous-flow reactor was operated for the enrichment of the bacterial community. High-throughput sequencing analysis showed that Nitrospira (NOB) using in batch experiments was extended from 4.78% to 12.08% during the under continuous-flow operation for 27 days. For each batch experiments, an ammonia injection at the start-up resulted in the desired initial FA concentration (at pH = 8.1–8.2, T = 25 °C), and a continuous ammonia feeding stream allowed for a relatively stabilized FA levels as much as the initial one. Results indicated that FA inhibition on NOB was not instantaneous but occurred gradually at a certain reaction time. Low concentrations of FA (18.08–24.95 mg L−1) had a limited inhibition on NOB with increasingly high nitrate production rates, whereas high FA levels (36.06–50.66 mg L−1) exerted a significant negative impact on the NOB. Also, strong adaptation happened in these high levels of FA inhibition on NOB, which resulted in an overall low NOB activity during the whole aerobic operation.

Grain boundary dominated electrical conductivity in ultrananocrystalline diamond

N-type electrically conductive ultrananocrystalline diamond (UNCD) films were deposited using the hot filament chemical vapor deposition technique with a gas mixture of H2, CH4 and NH3. Depending on the deposition temperature and ammonia feed gas concentration, which serves as a nitrogen source, room temperature electrical conductivities in the order of 10−2 to 5 × 101 S/cm and activation energies in the meV range were achieved. In order to understand the origin of the enhanced electrical conductivity and clarify the role of ammonia addition to the process gas, a set of UNCD films was grown by systematically varying the ammonia gas phase concentration. These samples were analyzed with respect to their morphology and electrical properties as well as their carbon and nitrogen bonding environments. Temperature dependent electrical conductivity measurements (300–1200 K) show that the electrical conductivity of the samples increases with temperature. The near edge x-ray absorption fine structure measurements reveal that the electrical conductivity of the UNCD films does not correlate directly with ammonia addition, but depends on the total amount of sp2 bonded carbon in the deposited films.