Initial Ammonia Concentration Research Articles

Separation of ammonia from radioactive wastewater by hydrophobic membrane contactor

The radioactive wastewater produced in the manufacturing process of UO2 kernel for high temperature gas-cooled reactor (HTR) contains high concentration of ammonia. The ammonia has to be removed effectively for further treatment of the wastewater. In this study, the hydrophobic membrane contactor (HMC) was adopted to remove and recover the ammonia from radioactive wastewater at room temperature. The operating parameters such as feed velocity and initial ammonia concentration were determined. In addition, the effect of wastewater composition on ammonia separation was studied. The experiment results showed that ammonia removal efficiency could reach above 90% after 120 min operation when pH was not adjusted. While the initial pH of wastewater was adjusted to 12.0, ammonia removal efficiency could reach above 95%. The ammonia mass transfer coefficient increased with increase of feed velocity and tended to an asymptotic value when the feed velocity reached 0.049 m/s. When the initial ammonia concentration was 2211.6 mg/L, 5864.6 mg/L and 23,898.7 mg/L, the ammonia removal efficiency was 95.0%, 94.2% and 94.1%, respectively after 120 min operation, i.e. the initial concentration of ammonia in wastewater had almost no effect on ammonia separation. In addition, the coexisting substances, such as urea and tetrahydrofurfuryl alcohol (THFA), also had no effect on ammonia separation. The HMC is a promising way to separate ammonia from radioactive wastewater.

Heterotrophic nitrification and aerobic denitrification by Pseudomonas tolaasii Y-11 without nitrite accumulation during nitrogen conversion

A hypothermia aerobic nitrite-denitrifying bacterium, Pseudomonas tolaasii strain Y-11, was found to display high removal capabilities for heterotrophic nitrification with ammonium and for aerobic denitrification with nitrate or nitrite nitrogen. When strain Y-11 was cultivated for 4days at 15°C with the initial ammonium, nitrate and nitrite nitrogen concentrations of 209.62, 204.61 and 204.33mg/L (pH 7.2), the ammonium, nitrate and nitrite removal efficiencies were 93.6%, 93.5% and 81.9% without nitrite accumulation, and the corresponding removal rates reached as high as 2.04, 1.99 and 1.74mg/L/h, respectively. Additionally, ammonium was removed mainly during the simultaneous nitrification and denitrification process. All results demonstrate that P. tolaasii strain Y-11 has the particularity to remove ammonium, nitrate and nitrite nitrogen at low temperatures, which guarantees it for future application in winter wastewater treatment.

Nitrogen removal from raw landfill leachate by an algae-bacteria consortium.

A remediation system for the removal of nitrogen from landfill leachate by a mixed algae-bacteria culture was investigated. This system was designed to treat leachate with minimal inputs and maintenance requirements, and was operated as an open semi-batch reactor in an urban greenhouse. The results of this study showed a maximum nitrogen removal rate of 9.18 mg N/(L·day) and maximum biomass density of 480 mg biomass/L. The ammonia removal rates of this culture increased with increasing initial ammonia concentration; maximum nitrogen removal occurred at an ammonia concentration of 80 mg N-NH3/L. At starting ammonia concentrations above 80 mg N-NH3/L a reduction in nitrogen removal was seen; this inhibition is hypothesized to be caused by ammonia toxicity. This inhibiting concentration is considerably higher than that of many other published studies.

An experimentally validated nitrate–ammonium–phytoplankton model including effects of starvation length and ammonium inhibition on nitrate uptake

Nitrate and ammonium are the two most important ionic forms of inorganic nitrogen driving biomass production in marine and freshwater aquatic systems. The performance of plants and algae often changes when reared with either of these two forms of nitrogen individually, as well as when they are both present, or when cells have experienced previous periods of nitrogen starvation. Current functional responses quantifying how ambient nitrogen drives changes in population density are unable to capture interacting and transient effects of nitrate and ammonium. Hence, in this paper we formulate, calibrate, and test a new nitrate–ammonium quota model that accounts for nitrate and ammonium uptake, as well as the effects of nitrogen starvation length and ammonium-induced nitrate uptake inhibition. We fit the model with several time-series from the green alga Chlorella sp. reared in laboratory batch cultures under multiple initial conditions. We show that a single set of calibrated model parameters can capture time-series collected from experiments inoculated at 12 different initial concentrations of nitrate, ammonium, and biomass. The model also performed well when validated against time-series from two novel initial conditions withheld from model calibration. Our model therefore provides a framework for evaluating the potential broader ecological and environmental consequences of ambient nitrate and ammonium regimes for phytoplankton communities in nature and aquaculture.

Removal of ammonia by high-frequency ultrasound wave (1.7 MHz) combined with TiO2 photocatalyst under UV radiation

This study aims to use high-frequency ultrasound wave combined with ultraviolet radiation and titanium dioxide as a photocatalyst for ammonia removal. The performances of several treatment methods including aeration, ultraviolet, ultrasound, ultrasound–aeration, ultrasound–ultraviolet, ultraviolet–titanium dioxide–aeration, and finally ultrasound–ultraviolet–titanium dioxide were compared. The results clearly indicated the superiority of ultrasound–ultraviolet–titanium dioxide (US/UV/TiO2) system over other treatment processes. The effect of various variables including initial ammonia concentration, pH, TiO2 dosage, liquid height, UV intensity, and ultrasound frequency were investigated in the US/UV/TiO2 system. The results show that the removal efficiency of ammonia reduced as the initial ammonia concentration and liquid height increased. However, increase in TiO2 dosage caused an increase in removal efficiency. In addition, the optimum removal efficiency of US/UV/TiO2 system for ammonia was obtained at pH 11. After 120-min sonication by high-frequency ultrasonic wave and UV radiation in conjunction with TiO2, almost 100% ammonia removal was achieved. In addition, the results demonstrated that the UV intensity has significant influence on the removal efficiency of ammonia in the US/UV/TiO2 system. The presented results show that high-frequency ultrasound plays the main role in the US/UV/TiO2 system owing to its ability to generate atomization and acoustic streaming.

Characteristics of heterotrophic nitrifying bacterium strain SFA13 isolated from the Songhua River

Strain SFA13, with the ability to perform simultaneous heterotrophic nitrification and aerobic denitrification, was isolated from the Songhua River. Investigation of the phenotypic and genotypic characteristics of strain SFA13 revealed that its 16S rRNA gene sequence shares high similarity with that of Microbacterium esteraromaticum DSM 8609T (99.78 %). gyrB and recA gene sequences showed 92.40 % and 92.57 % similarity to those of M. esteraromaticum DSM 8609T, respectively, showing that strain SFA13 is a member of M. esteraromaticum. However, strain SFA13 showed distinctly different phenotypic characteristics from the type strain DSM 8609T. Strain SFA13 was negative for H2S production, β-fucosidase, hydrolysis of starch and Tween, utilization of salicin, l-alanine, d-fructose, d-galactose, d-glucose and d-trehalose; and positive for alkaline phosphatase, cystine arylamidase, acid phosphatase, naphthol-AS-BI-phosphohydrolase and β-galactosidase. The ammonium removal rate of strain SFA13 was affected by temperature, decreasing obviously as the temperature dropped from 30 °C to 10 °C. Even so, strain SFA13 exhibited a high ammonium removal efficiency at 5 °C. The highest ammonium removal rate was 4.41 mg NH4 + L−1 h−1 when the initial ammonium concentration was 61.63 mg L−1 at 5 °C. Excessive ammonium (more than 62 mg L−1) restricted the ammonium removal rate of strain SFA13. This strain could be used effectively to remove low concentrations of ammonium ion at low temperature.

Ammonium removal at low temperature by a newly isolated heterotrophic nitrifying and aerobic denitrifying bacterium Pseudomonas fluorescens wsw-1001

A heterotrophic nitrifier wsw-1001 was isolated from Songhua River and identified as Pseudomonas fluorescens. Ammonium removal by the strain at low temperature was investigated. The effect of initial ammonium concentration (from 5 to 1000 mg/L) and culture temperature (from 4°C to 30°C) on ammonium removal efficiency was studied. Biodegradation product, , , N2, N2O and intercellular N were monitored. The results indicated that the strain had potential for water and wastewater treatment. Ammonium could be removed by the strain at low temperature. Ammonium removal efficiency increased with temperature from 4°C to 20°C and decreased with ammonium concentration from 5 to 1000 mg/L. The strain exhibited a capability of heterotrophic nitrification and aerobic denitrification using as the sole nitrogen source at 8°C. and were reduced by the strain. Nitrogen balance analysis in the presence of 39.7 mg/L indicated that 71.2% was removed by converting to N2 (46.3%) and assimilating as biomass (42.5%). Substances such as , and N2O were detected at very low concentrations. Ammonium mono-oxygenase, hydroxylamine oxidase, nitrite reductase and nitrate reductase activity were measured. The ammonium removal pathway of the strain was speculated to be .

Statistical analysis and optimization of ammonia removal from aqueous solution by zeolite using factorial design and response surface methodology

The ability of zeolite as a low-cost adsorbent for ammonia removal from aqueous solution was studied through batch adsorption experiments. The results showed that zeolite was effective in eliminating ammonia from aqueous solution. Factorial design and response surface methodology were applied to evaluate and optimize the effects of pH, adsorbent dose, contact time, temperature and initial ammonia concentration. Low pH condition was preferred with the optimum pH found to be 6. High adsorbent dose generated high removal rate and low adsorption capacity. Results of factorial design and response surface methodology showed that temperature was not a significant parameter. The model prediction was in good agreement with observed data (R2=0.969). The optimum Qe was 22.90mg/g achieved at pH 7 and initial TAN concentration of 3000mg/L. The adsorption kinetics followed the Pseudo-second order kinetic model (R2= 0.998). Equilibrium data were fitted to Langmuir and Freundlich isotherm models with Freundlich model (Kf=2.24L/mg, 1/n=0.28) providing a slightly better predication (R2=0.992). The 1/n value of less than 1 indicated that the removal process was favorable.

Influence of pH and pH adjustment conditions on photocatalytic oxidation of aqueous ammonia under airflow over Pt-loaded TiO2

The influence of pH and pH adjustment conditions on the photocatalytic oxidation of aqueous ammonia in the presence of Pt-TiO2 under airflow was investigated as a possible treatment for ammonia-containing wastewater. Ammonia oxidation proceeded only under alkaline conditions, and the maximum initial oxidation rate was obtained at pH∼10. The pH of the reaction suspension decreased with the formation of nitrite and nitrate species, stopping completely when the pH fell below 7 for reactions in which the initial pH (pHi) was adjusted within the range 8.7–11.3 using NaOH(aq). The rate of ammonia oxidation was higher when NaOH(aq) was used to adjust the pHi than that achieved using Na2CO3–NaHCO3 buffer solution at the same pH. The maximum ammonia adsorption on Pt-TiO2 (measured under dark conditions) was obtained at pH 10 and the amount of ammonia adsorbed when the pHi was adjusted with NaOH(aq) was higher than that achieved using the Na2CO3–NaHCO3 buffer solution at the same pH; thus, the amount of adsorbed ammonia strongly affected the oxidation rate. Although the selectivity for the sum of the undesired products, nitrite and nitrate was high when the ammonia concentration was low (e.g., 5mM), the selectivity decreased as the initial ammonia concentration increased for each pH and pH adjustment condition. Suppression of the selectivity was evident when the pHi was adjusted to 10 with NaOH(aq). The selectivity was affected by the changes in the density of N-containing species on the photocatalyst surface as the pH and pH adjustment conditions were varied.

Ammonia recovery from high concentration wastewater of soda ash industry with membrane distillation process

Vacuum membrane distillation was applied in the treatment of high ammonia content wastewater for the recovery of ammonia. Hydrophobic poly(vinylidene fluoride) hollow fiber membranes were used as the separation media. The initial ammonia concentration and pH value of the feed solution were destined owing to the composition of the wastewater. The effects of feed temperature, velocity, and operation time on the ammonia removal efficiency, separation factor, and water content in produced ammonia vapor were studied. The results showed that feed temperature was the most important factor affecting ammonia removal efficiency, which was improved from 78 to 99% as the temperature enhanced from 30 to 60°C. The feed velocity and operation time also affected the ammonia removal efficiency and separation factor obviously. A pilot-scale experiment was carried out using a membrane module of 20 m2 membrane area. Preliminary results showed that proper ammonia removal efficiency and product property were obtained.

Isolation and Characterization of Benzene-Degrading Heterotrophic Nitrifying Strain

An aerobic benzene-degrading heterotrophic nitrifying strain Pseudomonas sp.BN5 was isolated from the well domesticated microbes. Growth and nitrification characteristics were investigated with the benzene as the sole carbon and energy source and the NH+4-N as nitrogen source under aerobic condition. It was demonstrated that the favorite C/N ratio, temperature and speed of Pseudomonas sp.BN5 was 10, 30°C and 180rpm, respectively. About 70.86% of ammonium and 100% of benzene was removed after 72 h of incubation at initial benzene and ammonium concentration of 52.37mg/L and 16.13mg/L, respectively. Only trace accumulation of nitrate was observed during the process.

Submersible microbial desalination cell for simultaneous ammonia recovery and electricity production from anaerobic reactors containing high levels of ammonia

High ammonia concentration in anaerobic reactors can seriously inhibit the anaerobic digestion process. In this study, a submersible microbial desalination cell (SMDC) was developed as an innovative method to lower the ammonia level in a continuous stirred tank reactor (CSTR) by in situ ammonia recovery and electricity production. In batch experiment, the ammonia concentration in the CSTR decreased from 6 to 0.7g-N/L during 30days, resulting in an average recovery rate of 80g-N/m2/d. Meanwhile, a maximum power density of 0.71±0.5W/m2 was generated at 2.85A/m2. Both current driven NH4+ migration and free NH3 diffusion were identified as the mechanisms responsible for the ammonia transportation. With an increase in initial ammonia concentration and a decrease in external resistance, the SMDC performance was enhanced. In addition, the coexistence of other cations in CSTR or cathode had no negative effect on the ammonia transportation.

Ammonium removal by liquid–liquid membrane contactors in water purification process for hydrogen production

In this work, a liquid–liquid membrane contactor (LLMC) was evaluated to remove ammonia traces from water used for hydrogen production by electrolysis. Three operational parameters were evaluated: the feed flow rate, the initial ammonia concentration in the water stream, and the pH of solution. Synthetic aqueous solutions with ammonium concentration of 5–25 mg L−1 and a sulfuric acid solution (pH 2) were supplied to the LLMC in countercurrent and open-loop configuration with flow rates between 2.72 × 10−6 and 22.6 × 10−6 m3 s−1 and the pH values of the solution with ammonium between 8 and 11. A 2D numerical model was developed considering advection–diffusion equation inside a single fiber of the lumen with fully developed laminar flow and liquid–gas equilibrium in the membrane–solution interface. Predictions of the model were then validated against experimental data, which were found to be in good agreement. According to both, experimental data and numerical predictions, the hollow-fiber membrane contactor technology is a suitable alternative to remove ammonium from water and to feed the membrane distillation unit in order to fulfill water quality requirements for electrolysis-based hydrogen production.

Application of Plackett-Burman Design in Screening the Significant Factors Effecting Denitrification of Salinity Wastewater by Biofortification SBR

A Plackett–Burman design was employed to investigate the effect of various parameters on the denitrification effect of high salinity wastewater treated by biofortification SBR.The purposes of this study were to investigate the significance of pH, DO, C/N, the initial ammonia concentration, salinity, the amount of bacteria and sludge concentration (MLSS).Factors which have significant influence on the denitrification effect of biofortification SBR treatment are quickly screened and used to establish a mathematical model.The results of quick screening provide critical factors for the optimization of operating parameters.

Evaluation of the Removal of Ammonium by Kaolin, Synthesized Zeolite Produced from Kaolin and Magnetic Zeolit from Aqueous Solutions

Background: Ammonium has introduced to environment by various resources such as industrial, domestic and agricultural effluents. Ammonium is toxic which can lead to oxygen depletion in the water and threating aquatic. On the current method for ammonium removal from water and wastewater is ion exchange and adsorption of the ion by zeolite. The objective of this study was removing of ammonium by Kaolin, zeolite synthesized from Kaolin and magnetic zeolite from aqueous solutions. Methods: In this study, various concentrations of Kaolin and synthesized zeolite (0.5, 1, 1.5, 2, 2.5 g/l) within aqueous solution containing ammonium ions (1- 20 mg/l) with different contact time (10-240 min) and pH values (3, 5, 7, 9, and 11) were probed. Using SEM, XRD and FTIR analysis, chemical characterization of synthesis Zeolite were studied.n Results: The maximum ammonium adsorption occurred at pH=7 and in 240 minutes contact time. By increasing initial concentration of ammonium, its sorption capacity was increased. However, by increasing the adsorbent dose, the removal efficiency was decreased. Optimum dosage of kaolin and zeolite was 2 g/L and 1.5 g/L, respectively. The isotherm data of ammonium were correlated reasonably well by Freundlich isotherm model. It was found that the adsorption of ammonium ion on kaolin, synthesis zeolite and magnetic zeolite followed pseudo-second order kinetic model. Conclusion: This research confirmed that the adsorption of ammonium by Kaolin, synthesized Zeolite and magnetic Zeolite is a low-cost and high-efficient method.

Enhanced Electrolytic Removal of Ammonia from the Aqueous Phase with a Zeolite-Packed Electrolysis Reactor under a Continuous Mode

This research investigated the mechanism and effect of influencing factors for aqueous ammonia removal by electrolysis in continuous mode with a zeolite-packed electrolysis reactor. Under the conditions of 30-min hydraulic retention time (HRT), 1.8-A current, and 300-mg/L chloride ion concentration, the ammonia concentration decreased from 25 to 0.3 mg N/L within 1.5 h electrolysis time. A total of 4.4 mg N/L nitrate, 0.03 mg N/L nitrite, and 0.3–0.8 mg N/L chloramines were detected in effluent, which accounted for 76% removal of total nitrogen from the aqueous phase. Moreover, the ammonia-presaturated zeolite was almost completely regenerated during the same time period. HRT, current, and chloride ion concentration were found to have a significant effect on ammonia removal as well as zeolite regeneration. Whereas other conditions were fixed, a minimum of 10-min HRT, 1.0-A current, and 210-mg/L chloride ion concentration were required to keep the effluent ammonia concentration below 1 mg N/L. For the treatment of municipal wastewater, minimum HRTs of 7.5, 11, and 21 min were suggested for initial ammonia concentrations of 13.5, 30.2, and 53.5 mg N/L under the conditions of 300-mg/L chloride and 1.8-A current.

Ammonium-oxidizing bacteria facilitate aerobic degradation of sulfanilic acid in activated sludge.

Sulfanilic acid (SA) is a toxic sulfonated aromatic amine commonly found in anaerobically treated azo dye contaminated effluents. Aerobic acclimatization of SA-degrading mixed microbial culture could lead to co-enrichment of ammonium-oxidizing bacteria (AOB) because of the concomitant release of ammonium from SA oxidation. To what extent the co-enriched AOB would affect SA oxidation at various ammonium concentrations was unclear. Here, a series of batch kinetic experiments were conducted to evaluate the effect of AOB on aerobic SA degradation in an acclimatized activated sludge culture capable of oxidizing SA and ammonium simultaneously. To account for the effect of AOB on SA degradation, allylthiourea was used to inhibit AOB activity in the culture. The results indicated that specific SA degradation rate of the mixed culture was negatively correlated with the initial ammonium concentration (0-93 mM, R²= 0.99). The presence of AOB accelerated SA degradation by reducing the inhibitory effect of ammonium (≥ 10 mM). The Haldane substrate inhibition model was used to correlate substrate concentration (SA and ammonium) and oxygen uptake rate. This study revealed, for the first time, that AOB could facilitate SA degradation at high concentration of ammonium (≥ 10 mM) in an enriched activated sludge culture.

Leaching of Calcareous Bornite Ore in Ammoniacal Solution Containing Ammonium Persulfate

The leaching process of copper from calcareous bornite ore using ammonium persulfate as an oxidant in ammoniacal solution was investigated. The effects of stirring speed, temperature, initial concentration of ammonia and ammonium persulfate, and liquid-to-solid (L/S) ratio on the extraction percentage of copper from bornite ore were studied. The results show that the optimum leaching conditions for bornite ore with a maximum extraction of copper 88.9 pct are temperature 313.15 K (40 °C), reaction time 4 hours, stirring speed 600 r/min, L/S ratio 7/1 cm3/g, initial concentration of ammonia 2.0 mol/dm3, and ammonium persulfate 3.0 mol/dm3.

Application of a compound containing silica for removing ammonium in aqueous media

In the present investigation, removal of ammonium from aqueous solutions by a compound containing silica was considered. The compound was a waste of ferrosilicon compound produced during Ferro‐alloy manufacturing. The results showed that an increase in the pH of solution up to 7 caused a rapid increase in the adsorbed ammonium to 36.21 mg/g. But adsorbed ammonium was decreased to 26.51 mg/g as the initial pH reached to 10. The amount of adsorbed ammonium was increased with contact time and initial ammonium concentration. A contact time of 180 min was selected because there was no significant increment in adsorbed ammonium as contact time was further increased. The results exhibited suitability of the pseudo‐second order kinetic model (R2 = 0.9867). Increasing initial ammonium concentration from 10 to 180 mg/L resulted in an increment in adsorbed ammonium from 6.69 to 59.13 mg/g, respectively. The obtained data were fitted to Langmuir, Freundlich, and Dubinin–Radushkevich (D‐R) isotherm models in which the obtained correlation coefficient showed the relatively better fitness of the data to Langmuir model (R2 = 0.9969) with a maximum adsorption capacity of 78.74 mg/g. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 105–111, 2015

Non-linear dynamics of nitrogen isotopic signature based on biological kinetic model of uptake and assimilation of ammonium, nitrate and urea by a marine diatom

Non-linear dynamics of nitrogen isotopic signature during uptake and assimilation of ammonium, nitrate and urea by culture of Thalassiosira pseudonana was described mathematically. Experimental data of the laboratory batch reactors were taken from Waser et al. (1998a,b). The measured dynamics of nitrogen isotopic signature was the consequence of biological kinetic model based on the modified Monod function, which additionally took into account that during substrate uptake isotopic fractionation terminates when the N-substrate concentration decreases below a certain threshold level. Contrasting to traditional description, in our approach, kinetic isotopic fractionation factor α means a constant ratio between specific maximum substrate uptake rates of light and heavy isotopes. In this case, the factor ɛ commonly used to describe isotopic enrichment is not supposed to be constant and its values depend on threshold concentrations of N-substrate. The lower was the threshold concentration, the higher was the maximum value of ɛ when N-substrate became exhausted. The model described complex substrate kinetics in N-sufficient and N-deficient conditions reasonably well using the kinetic coefficients preliminary obtained for the individual ammonium, nitrate and urea. In N-sufficient conditions, uptake of urea and nitrate started after depletion of ammonium because high ammonium concentration strongly inhibited nitrite and urea uptake and assimilation. In N-deficient conditions, inhibition of urea and nitrate uptake by ammonium was significantly less pronounced. In accordance with the model, at low initial ammonium concentration a decrease of nitrogen isotopic fractionation occurs.