Initial Ammonia Concentration Research Articles

Photodegradation of Ammonia by TiO<sub>2</sub> Nanoparticles Produced by Flame CVD Process

Photodegradation of ammonia by mixed-phase TiO2 nanoparticles, synthesized by the oxidation of TiCl4 in turbulent propane/air flame chemical vapor deposition (CVD) process, has been investigated experimentally by using a tubular photoreactor with thin TiO2 films coated on the reactor wall by sedimentation. Effects of ammonia initial concentration from 2-40mg/m3, relative humidity from 30-75%, rutile mass fraction from 20-50% of TiO2 nanoparticles on degradation degree are examined under the conditions of 38g/cm2 catalyst loading, 24mW/cm2 UV irradiation of 254nm, and 5.7sec residence time in the reactor. Results show that photocatalytic activity is higher when rutile mass fraction is from 0.2 to 0.4, corresponding higher PL intensity, and 60% conversion is achieved at initial ammonia concentration of around 5mg/m3 and 70% relative humidity. Based on experimental results, separation of photoinduced electron (e-) and hole (h+) pairs by rutile phase is discussed.

Nitritation performance in membrane-aerated biofilm reactors differs from conventional biofilm systems

Nitrogen removal via nitrite has gained increasing attention in recent years due to its potential cost savings. Membrane-aerated biofilm reactors (MABRs) are one potential technology suitable to achieve nitritation. In this study we compared lab scale MABRs with conventional biofilm reactors to evaluate the influence of environmental conditions and operational parameters on nitritation performance. The oxygen mass transfer rate is postulated as a crucial parameter to control nitritation in the MABR: Clean water measurements showed significant underestimation of the total oxygen mass transfer, however, accurate determination of the oxygen mass transfer coefficient ( k m) of the system could be achieved by adjusting the liquid-phase mass transfer resistance in the constructed model. Batch experiments at different initial ammonium concentrations revealed that the conventional biofilm geometry was superior for nitritation compared to MABRs. These differences were reflected well in estimates of the oxygen affinity constants of the key microbial players, AOB and NOB ( K O,AOB < K O,NOB (in both systems) and K O,NOB values smaller in the MABR vs. the conventional biofilm system). It also appeared that – in addition to oxygen limitation – the absolute and relative substrate concentrations in the biofilm (esp. of oxygen) are very important for successful nitritation. Initial biomass composition, furthermore, impacted reactor performance in the MABR systems indicating the need for appropriate inoculum choice.

Influence of Thiourea Dimers in the Chemical Bath Deposition Process of Metal Sulfides

The chemical bath deposition of metal sulfide, especially CdS, is the most common way of growing buffer layers in the chalcopyrite photovoltaic solar cells. From the kinetic point of view, the reactions should always be reproducible with the same initial reactant concentration of thiourea, ammonia, and cadmium salt, the same temperature, and the same deposition time. But different reaction kinetics of CdS molecule formation and deposition is observed. Different thiourea lots with nominally the same purity show different kinetics of the reaction and resulting CdS layer thicknesses after the reaction.

Adsorption of Ammonia from Aqueous Solution Using Zeolite-Attapulgite Nano-Pore Structure Ceramisite

Zeolite-attapulgite nano-pore structure ceramisite was prepared using natural zeolite and attapulgite through compounding, granulation and calcination.After elementary characterization of this ceramisite by mercury porosimeter, batch tests were carried out to examine its removal mechanism of ammonia. The influences of pH, contact time, initial ammonia concentration and temperature on the ammonia removal were investigated. The optimum pH for adsorption of ammonia was found to be less than 7. The adsorption process followed pseudo-second order rate model. Adsorption isotherm studies showed that Freundlich model fitted the experimental data. The sorption of ammonia increased with the rise of temperature because adsorption process was endothermic. The zeolite-attapulgite composite nano- pore structure ceramisite shows very good promise for practical applicability of ammonia removal from aqueous solution.

Performance of a Multipurpose Filter for Simultaneous Removal of Ammonium and Suspended Solids as a Polishing Stage for a Domestic Wastewater Plant Effluent

A multipurpose filter column was studied as a polishing stage for the simultaneous removal of ammonium and suspended solids from a secondary domestic wastewater effluent. The multipurpose filter consisted of sand as the regular filter material, primarily for the purpose of suspended solids removal, and an ammonium selective natural zeolite, clinoptilolite, for the removal of ammonium. A Turkish clinoptilolite from the Bigadic region was used in the experiments. The capacity of the clinoptilolite was determined by isotherm analysis to be 10.4 mg/g for 20 mg/lt initial wastewater ammonium concentration at pH 7.3 with 0.5-1 mm diameter. In the continuous runs, the multipurpose filter unit was operated down flow with 50% of the unit consisting of clinoptilolite in the upper layer, and 50% sand in the lower both with a grain size range of 0.5-1 mm. The results have revealed that simultaneous removal of 100% of the ammonium and 75% of the suspended solids removal be achieved in the multipurpose filter unit for a working period of 38 hours. The success of this proposal could lend an alternative both for the upgrading of existing treatment plants and for polishing for ammonium and suspended solids rate by using one compact unit.

Watershed-Scale Impacts of Nitrogen from On-Site Wastewater Systems: Parameter Sensitivity and Model Calibration

A numerical watershed model was used to evaluate the potential influence of various point and nonpoint sources including on-site wastewater systems (OWS) on stream nitrate concentration in Turkey Creek Watershed, Colorado. A watershed analysis risk management framework model was used for this study, and was calibrated to observed stream nitrate concentrations using an automatic calibration tool. Parameter sensitivity analysis was done to select critical parameters for calibration and to reduce uncertainty in the simulated results. Sensitivity analysis of nitrate transport and transformation parameters showed that stream nitrate concentration is highly sensitive to cation exchange capacity, nitrification rate, base saturation of ammonium, initial concentration of ammonium in the soil, and some of the crop growth related parameters. The calibrated model was used to evaluate scenarios related to OWS including the impacts of population growth and new development and impacts of conversion of OWS to conventional sewers. The results showed that there would be a significant increase in stream nitrate concentration with increasing population. Conversion of OWS to sewers increased stream nitrate concentration but decreased nitrate concentration in the bottom soil layer indicating that OWS are beneficial with respect to stream nitrate concentration but may increase nitrate concentrations in groundwater.

AMMONIUM IONS REMOVAL FROM AQUEOUS SOLUTIONS USING MESOPOROUS (Al)Si-MCM-41

The batch removal of ammonium ions from aqueous solutions under different experimental conditions using (Al)Si-MCM-41 mesoporous molecular sieve in comparison with LTA microporous zeolite was investigated in this study. The ammonium uptake was dependent on the initial ammonium concentration. The equilibrium sorption data were fitted using Freundlich and Langmuir isotherm models. The Langmuir model (monolayer sorption) gave the best fit (R 2 = 0.9965 for (Al)Si-MCM-41 and R 2 = 0.9995 for LTA). The saturation capacity (monolayer coverage) was found of 33.33 mg NH4 + /g (Al)Si-MCM-41 and 55.55 mg NH4 + /g LTA. Equilibrium sorption was reached at about 25 min on (Al)Si-MCM-41 and at about 60-90 min in the case of LTA molecular sieves. The kinetic data showed that the sorption rate could be better described by pseudo-second order model.

Unbalanced N:P ratios and nutrient stress controlling growth and toxin production of the harmful dinoflagellate Prorocentrum lima (Ehrenberg) Dodge

The responses of the benthic marine dinoflagellate Prorocentrum lima to nutrient stress induced by unbalanced N:P ratios were the subject of this study. Batch cultures of P. lima cells were grown under NP sufficient (N as nitrate and ammonium) and deficient conditions, and the cell growth and toxicity were followed for eight weeks. P. lima grew slowly in all nutrient conditions and net growth rates ranged from 0.11 to 0.22 divisions day −1. Phosphorus (P) was taken up with high uptake rates in all treatments until the end of exponential phase and reached limitation in the P deficient cultures. Nitrogen (N) did not reach limitation in any treatment. In the cultures with nitrate as exclusive N source, uptake rates of nitrate remained high after the exponential phase, suggesting that P. lima cells continued to accumulate N under surplus N availability. Nitrate was slowly consumed and therefore maintained cell growth, as documented by a prolonged exponential phase and an algal biomass increasing at low rates still after seven weeks of incubation. In the cultures with ammonium as exclusive N source, ammonium was taken up with the highest N uptake rates until the end of exponential phase. However, high initial concentrations of ammonium proved to be toxic to P. lima cells, demonstrating growth inhibition with the lowest algal biomass and okadaic acid (OA) production among treatments. The OA production increased after the exponential phase in all nutrient conditions when cell growth slowed down, suggesting that OA production was regulated by growth limitation. The highest OA cellular content (11.27 ± 3.30 pg OA cell −1) was found in the P deficient cultures, where P decreased to limitation after the exponential phase (P < 0.1 μM). We argue that the severely low P concentrations slowed down the growth rate so as to allow for a higher accumulation of OA in the P. lima cells that continued to produce OA at the same rate.

Principles of interaction of ammonium ion with natural Jordanian deposits: Analysis of uptake studies

Ammonium ion removal from aqueous solution by Petra clay minerals has been established. To study the efficiency of the Petra clay as sorbent, the effect of relevant parameters, such as temperature, contact time, pH and initial ammonium (NH4+) concentration were examined. Kinetics experiments were also done at different parameters. The pseudo first-order, pseudo second-order kinetic models and intra-particle diffusion model were used to describe the kinetic data. The pseudo second-order kinetic model provided excellent data fitting (R2>0.99), and the rate constant for sorption was predicted. Activation energy of sorption has also evaluated as 22.60kJ/mol based on the pseudo second-order rate constants, the findings of this investigation suggest that physical sorption plays a role in controlling the sorption rate. Ammonium uptake rate was controlled by particle diffusion at different variables.

Effect of initial ammonium concentration on taxoid production and biosynthesis genes expression profile in suspension cultures of Taxus chinensis cells

AbstractThe effect of initial ammonium concentration in medium on production of taxuyunnanine C (Tc) in suspension cultures of Taxus chinensis was investigated. The results showed that the cell growth was reduced at an initial ammonium concentration of 2 mM when compared to the control (20 mM of initial ammonium in medium), but interestingly the Tc content was enhanced by two fold to 8.07 mg/g DW. The transcription of a couple of key genes in taxoid biosynthetic pathway was investigated by quantitative real‐time PCR to understand why Tc biosynthesis was improved at the low initial medium ammonium (2 mM). It was found that the transcription level of genes of geranylgeranyl diphosphate synthase, taxadiene synthase, taxadiene 5α‐hydroxylase, taxadiene 5α‐ol O‐acetyltransferase, taxane 10β‐hydroxylase and taxadiene 13α‐hydroxylase were all induced in the early stage of cultivation at 2 mM of initial ammonium compared to the control (20 mM of initial ammonium). The stimulation of secondary metabolite synthesis by a lower ammonium concentration may be resulted from the ammonium deficiency‐induced transcription of Tc biosynthetic genes.

Application of natural zeolite for phosphorus and ammonium removal from aqueous solutions

Removal of both nutrients ammonium and phosphorus by natural zeolite has been studied in lab scale by using a mechanically stirred batch system (1000 ml). Zeolite, a mean particle size of 13 μm, was used as an adsorbent for the removal of ammonium and then as a seed material for the precipitation of calcium phosphate. A relationship was established between the uptake of ammonium by zeolite and the ratio of initial ammonium concentration to zeolite dosage. Ammonium uptake of zeolite was almost completed within initial 5 min of adsorption period. There is no pronounced effect of zeolite and ammonium, neither positive nor negative on the amount of calcium phosphate precipitation. The extent of the precipitation of phosphate increased with rising pH. It was also observed that when the system was allowed to relax at constant pH (i.e. under relatively low super saturations), a certain lag time was noted to elapse at the onset of the precipitation. At the pH 7.2, the amount of initial fast precipitation within 5 min and total precipitation within 120 min were around 34% and 93%, respectively. Precipitation of calcium phosphate on to ammonium-loaded zeolite was achieved at low super saturations (<pH 7.5) through secondary nucleation and crystal growth, leading to an increase in particle size.

Investigation on natural and pretreated Bulgarian clinoptilolite for ammonium ions removal from aqueous solutions

The possibilities for ammonium ions removal from aqueous solutions by natural and NaCl pretreated Bulgarian clinoptilolite from Beli plast deposit were studied. Experiments were carried out using batch method. The adsorption of NH 4 + was investigated as a function of the solution pH, dosage of adsorbent, initial ammonium concentration and temperature. The results clearly showed that the treatment with NaCl improved both the adsorption capacity and the removal efficiency of natural clinoptilolite. The equilibrium experimental data for adsorbed NH 4 + ions on clinoptilolite samples were correlated better by the Langmuir isotherm model. The maximum adsorption capacities for ammonium ions shown by natural and pretreated clinoptilolites (CL_Na and CL_Na(t)) were 7.85, 12.29 and 18.40 mg/g, respectively. The results indicated a significant potential of the natural and conditioned clinoptilolites as adsorbents for ammonium removal.

Nitrogen excretion by the sheep abomasal parasite Teladorsagia circumcincta

Excretion of nitrogenous substances by Teladorsagia circumcincta was investigated during incubation of L3 in phosphate buffer for up to 30 h and adult worms for 4–6 h. Ammonia was the main excretory product, with about 20% urea. For the first 4–6 h, ammonia excretion by L3 was temperature dependent, directly proportional to the number of larvae, but independent of the pH or strength of the phosphate buffer. Later, ammonia excretion slowed markedly in L3 and adults and reversed to net uptake in L3 by 30 h. An initial external ammonia concentration of 600 μM did not alter the pattern or magnitude of excretion. Re-uptake of ammonia did not occur at extremes of pH or low buffer strength and was slightly reduced at the highest external concentrations. Ammonium transporters and enzymes of glutamate metabolism, including glutamate dehydrogenase, glutamine synthetase and possibly glutamate synthase, are worthy of further investigation as anthelmintic targets.

Enhancement of bubble absorption process using a CNTs-ammonia binary nanofluid

The main objective of the paper is to investigate the enhancement of the heat and mass transfer characteristics for a NH 3/H 2O bubble absorption process using the CNTs-ammonia binary nanofluid as a working medium. Using the surface modification of CNTs, the CNTs-ammonia binary nanofluid is successfully prepared without the addition of any dispersants. The effects of the mass fraction of CNTs, the initial concentration of ammonia in the binary nanofluid and the flow rate of ammonia vapor on NH 3/H 2O bubble absorption are studied experimentally. The mechanism of the binary nanofluid enhancing bubble absorption is discussed accordingly. The results show that the mass fraction of CNTs has an optimum value to the effective absorption ratio of the binary nanofluid, and the effective absorption ratio increases with the initial concentration of ammonia increasing.

Validation and Applications of a Chemical Equilibrium Model for Struvite Precipitation

Removal of nutrients like nitrogen and phosphorus from wastewater can be accomplished by precipitating these as the mineral struvite (NH4MgPO4. 6H2O). Predicting struvite precipitation potential, yield, and purity is important for designers and operators of reactors for struvite precipitation. In this paper, a mathematical model of this precipitation process is developed using physicochemical equilibrium expressions, mass balance equations for nitrogen, phosphorous and magnesium, and charge balance. The model was simulated to explicitly solve for equilibrium concentrations of eighteen species that included dissolved (three), ionic (ten), and solid (five) species for a given set of initial concentrations of ammonium–nitrogen, magnesium and phosphate–phosphorus, and pH. The model simulations were validated against literature experimental data, which used synthetic as well as actual wastewater, and data from our experiments. The model satisfactorily predicted most data. Struvite fraction in the precipitate ranged from 27% to 100%. The purity of struvite in the precipitate and the pH that maximizes struvite fraction was dependent on the initial concentrations of ammonium, magnesium, and phosphate. Optimum pH and struvite fraction was, respectively, 8.5 and 29.3% for an equimolar mixture of ammonia, magnesium, and phosphate and 9.8 and 98.3% for 10:1.7:3.4 mM ratio. Struvite fraction in the precipitate increased as magnesium became limiting or as ammonia to phosphate ratio increased and magnesium to phosphate ratio decreased. Since the struvite component is only a fraction of the total solids, it is erroneous to report the total precipitate produced as being struvite as is conventionally done.

Effect of Packing Materials and Other Parameters on the Air Stripping Process for the Removal of Ammonia from the Wastewater of Natural Gas Fertilizer Factory

Air-stripping method was used to remove ammonia from the wastewater collected from natural gas fertilizer factory. Different materials were used as packing materials for the air stripping system. The effect of pH over 10.5, air-water flow ratio, nature of packing materials, height of materials and initial influent concentration of ammonia on air stripping unit were investigated. An attempt has been made to find out the stripping con-stant. Stripping constant was found to be .001, 0014, .001 and .0009 for coal, plastic ring, stone chips and wood chips, respectively. Best result was found for plastic ring for its higher surface area. Wood chips did not give good result, because the chips amalgamate with each other and hence reduces the surface area.

Ability of Various Plant Species to Prevent Leakage of N, P, and Metals from Sewage Sludge

The preventive effect of vegetation on nutrient and metal leakage from sewage sludge (SS) used in treatment of mine waste was investigated. In a 10-week greenhouse study, the release of ammonium, nitrate, phosphate, Cd, Cu, and Zn from SS was analyzed in the absence (control) and presence of basket willow, fireweed, reed Canary grass (RCG), and Scots pine. Plants significantly decreased the leakage by reducing the amount of leachate, and lowered the concentrations of phosphate (to 0.1 mg L−1), Cu (0.8 mg L−1), and Zn (2.2 mg L−1); and plants increased the pH in the leachate towards the end of the experiment. The most efficient plant was RCG that significantly decreased the total leakage of all pollutants. However, plants could not counteract high initial concentrations of ammonium and nitrate (< 400 mg L−1 of both) and drop in pH (to 4.5), or increasing Cd release (< 9.7 μg L−1). RCG and fireweed used both ammonium and nitrate as nitrogen source and were more efficient in preventing nitrate leakage, compared with willow and pine that mainly used ammonium. This study indicates that introduction of RCG is a promising method for phytostabilization of SS, but that alkaline additives are needed to prevent an initial decrease in pH.

Activity of Cu-activated carbon fiber catalyst in wet oxidation of ammonia solution

Aqueous solutions of 200–1000 mg/L of ammonia were oxidized in a trickle-bed reactor using Cu-activated carbon fiber (ACF) catalysts, which were prepared by incipient wet impregnation with aqueous solutions of copper nitrate that was deposited on ACF substrates. The results reveal that the conversion of ammonia by wet oxidation in the presence of Cu-ACF catalysts was a function of the metal loading weight ratio of the catalyst. The total conversion efficiency of ammonia was 95% during wet oxidation over the catalyst at 463 K at an oxygen partial pressure of 3.0 MPa. Moreover, the effect of the initial concentration of ammonia and the reaction temperature on the removal of ammonia from the effluent streams was also studied at a liquid space velocity of less than 3.0 h −1.

A unified model of ammonium oxidation rate at various initial ammonium strength and active ammonium oxidizer concentrations

This paper attempts to provide insight into the biological ammonium oxidation process applied to high-strength ammonium wastewater treatment. The ammonium oxidation process has been investigated at various ammonium and biomass concentrations. Using the oxygen uptake rate (OUR) method, a proportion of both active ammonium oxidizers (AAO) and nitrite oxidizers to the total suspended solids were separately estimated, and then tested to normalize the ammonium oxidation rate at various ammonium strengths and AAO concentrations. High-ammonium strength showed no significant inhibition to ammonium oxidation due to high-AAO concentration. It was demonstrated that the key factor deciding the specific ammonium oxidation rate was the ratio of ammonium concentration to the active nitrifiers (AN) concentration, but not the sole-variable such as initial ammonium concentration and AN concentration. Contois model was screened to suitably fit the ammonium oxidation kinetics under the high-ammonium loading condition, resulting in a half-saturation constant of 0.028 mg N mg −1 AAO and a maximum specific ammonium oxidation rate of 3.56 g N g −1 AAO d −1.

ROLE OF GLUTAMATE DEHYDROGENASE AND GLUTAMINE SYNTHETASE IN CHLORELLA VULGARIS DURING ASSIMILATION OF AMMONIUM WHEN JOINTLY IMMOBILIZED WITH THE MICROALGAE-GROWTH-PROMOTING BACTERIUM AZOSPIRILLUM BRASILENSE(1).

Enzymatic activities of glutamate dehydrogenase (GDH) and glutamine synthetase (GS) participating in the nitrogen metabolism and related ammonium absorption were assayed after the microalga Chlorella vulgaris Beij. was jointly immobilized with the microalgae-growth-promoting bacterium Azospirillum brasilense. At initial concentrations of 3, 6, and 10 mg · L(-1) NH4 (+) , joint immobilization enhances growth of C.vulgaris but does not affect ammonium absorption capacity of the microalga. However, at 8 mg · L(-1) NH4 (+) , joint immobilization enhanced ammonium absorption by the microalga without affecting the growth of the microalgal population. Correlations between absorption of ammonium per cell and per culture showed direct (negative and positive) linear correlations between these parameters and microalga populations at 3, 6, and 10 mg · L(-1) NH4 (+) , but not at 8 mg · L(-1) NH4 (+) , where the highest absorption of ammonium occurred. In all cultures, immobilized and jointly immobilized, having the four initial ammonium concentrations, enzymatic activities of Chlorella are affected by A.brasilense. Regardless of the initial concentration of ammonium, GS activity in C.vulgaris was always higher when jointly immobilized and determined on a per-cell basis. When jointly immobilized, only at an initial concentration of 8 mg · L(-1) NH4 (+) was GDH activity per cell higher.