Degradation Of Nitrate Research Articles

Simultaneous Removal of Trivalent Arsenic and Nitrate Using Microbial Fuel Cells

A rectangular double chamber with trivalent arsenic as the electron donor of the biological anode was constructed by microbial fuel cells (MFC), and the feasibility of the MFC simultaneous degradation of trivalent arsenic and nitrate was studied. Experimental results show that the co-matrix-coupled MFC reactor oxidizes trivalent arsenic in an anode chamber and degrades nitrate in the cathode chamber. The removal rate of trivalent arsenic is about 63.35%, and the degradation rate of nitrate is about 55.95% during the complete and stable operation period. MFC can continuously output electric energy, and the maximum output voltage is 388 mV. We compared and analyzed the main functional microflora of biofilm microorganisms in an anode chamber. In the long-term arsenic-polluted environment, the activity of Acinetobacter, Pseudomonas bacteria with arsenic resistance, was improved. It is inferred that a fraction of trivalent arsenic was oxidized to pentavalent arsenic by electrode-attached microorganisms. While remaining trivalent, arsenic was taken up by the suspended bacterial biomass and converted into stable arsenide. The results of this study have theoretical reference value for the expansion of the MFC application scope.

Water disinfection by ozonation has advantages over UV irradiation in a brackish water recirculation aquaculture system for Pacific white shrimp (Litopenaeus vannamei).

By keeping tropical shrimp, like Litopenaeus vannamei, in recirculating aquaculture systems (RAS), valuable food for human consumption can be produced sustainable. L.vannamei tolerates low salinities, and therefore, the systems can operate under brackish water conditions. The stabilization of the microbial community in RAS might be difficult under high organic loads, and therefore, water treatment measures like UV irradiation or ozone application are commonly used for bacterial reduction. To investigate the impact of these measures, the effects of UV irradiation and ozone application were studied in small-scale brackish water RAS with a salinity of 15‰ stocked with L.vannamei. UV reactors with 7 and 9W were used, and by ozonizers with a power of 5-50mg/hr, the redox potential in the water was adjusted to 350mV. Ozone had a stabilizing effect on the microbial composition in the water and on biofilms of tank surfaces and shrimp carapaces, prevented an increase of nitrite and accelerated the degradation of nitrate in the water. UV irradiation led to changes in the microbial composition and was less effective in optimizing the chemical water quality. Thus, the use of ozone could be recommended for water treatment in brackish water RAS for shrimp.

The Importance of Incorporating Denitrification in the Assessment of Groundwater Vulnerability

Human activities are deeply connected with groundwater reservoirs, so protecting them from pollution has become a priority in many regions of the world. Nitrate is considered the main groundwater pollutant since it is directly linked to many human activities. Agricultural activities and domestic wastewater have been identified as the main sources of nitrate in groundwater. Nevertheless, there are some natural processes that can mitigate nitrate pollution. Together with dilution processes, the degradation of nitrate through denitrification has been acknowledge as a process that can potentially reduce nitrogen loads, in both deep and shallow aquifers. Usually these processes were not properly quantified in vulnerability assessment methods, until the introduction of LOS indices. In this study, the application of the LOS indices on 4 agricultural areas is discussed, highlighting how the LOS indices can identify portions of the landscape with higher potential denitrification and how they directly enhance the groundwater vulnerability assessment. Previous studies have shown that LOS indices are a valuable tool for proper vulnerability assessment to nitrate, however they need to be coupled with other parameters that also describe nitrate behavior in groundwater. The SINTACS-SVN and DRASTIC-PA methods that include the LOS indices, were applied for the first time in the Epanomi coastal area to evaluate the reliably of the assessment and, despite the different classes range and the weights applied, similar groundwater vulnerability assessment maps were obtained. The nitrate vulnerability maps were comparable with the observed nitrate concentrations and were found to be highly comparable with original LOS maps. Nevertheless, it should be kept in mind that vulnerability methods are only screening tools and groundwater quality observations are pivotal information for environmental management.

A novel industrial-scale strategy to prevent degradation and caking of ammonium nitrate

Several research studies have been performed to minimise the hygroscopicity of ammonium nitrate for increasing its commercial value and decreasing the nitrogen content. In this study, the hygroscopicity of ammonium nitrate was reduced using silicic acid, calcium lignosulfonate, and sodium silicate in the two-stage vacuum ammonium nitrate production process. Degradation of ammonium nitrate was observed after two years of storage, which is considered a standard by the European Fertilizer Manufacturers Association.

Degradation of Nitrate, Ammonium and Phosphate in Domestic Wastewater by Aquatic Plants, Actinoscirpus grossus in Floating Treatment Wetland System (FTWs)

Ecological technologies such as wetlands constructed for wastewater treatment are innovative solutions for environmental protection and restoration. This study examines a Floating Treatment Wetlands System (FTWs), which is a new treating concept using macrophytes rooted in modified growing aquatic plants with floating systems. An aquatic plant, Actinoscirpus grossus obtained from rice fields in Banda Aceh. FCWs filled with five plants per shoot with five compartments were fed with domestic wastewater with a flow rate of 7 L/hour. Plant height was varied by 90cm - 150cm in Pond 1 and 50cm - 90cm in Pond 2, and Pond 3 was prepared as a control (without plants). Water quality in influent and effluent was analyzed every two weeks with a duration of 18 weeks and nine times sampling. Results showed a decrease in the concentration of nitrate, ammonium, and phosphate in the effluent flow with degradation efficiency (% DE) on average, NO3-N: 76.34%; NH4-N: 97.75%; and PO4 3-: 89.45%; respectively. The degradation of domestic wastewater showed very significant results. The periodic harvest management process becomes an important part of aquatic plants, Actinoscirpus grossus to achieve optimum results in treating waste, i.e., for 112 days with a maximum plant growth height of 165cm and 173cm for both variations of experimental ponds.

Simultaneous degradation of anodic nitrate and cathodic sulphate in a bioelectrochemical reactor: evaluation of degradation efficiency and characterization of microbial communities

Simultaneous degradation of anodic nitrate and cathodic sulphate in a bioelectrochemical reactor: evaluation of degradation efficiency and characterization of microbial communities

Enhancement of anaerobic degradation of petroleum hydrocarbons by electron intermediate: Performance and mechanism

A quinone-respiring strain capable of degrading multitudinous petroleum hydrocarbons was isolated by selective medium and identified as Bacillus sp. (named as C8). Maximum 76.7% of total petroleum hydrocarbons (TPH) were degraded by the biosurfactant-mediated C8 with the aid of nitrate and electron intermediate (anthraquinone-2,6-disulphonate, AQDS). The quantitative real-time PCR results of several intracellular key functional genes suggested that AQDS could participate in the transformation of intermediates and accelerate the electron transfer in the degradation of TPH and nitrate, thereby eliminating the accumulation of nitrite and increasing the degradation efficiency of TPH. A strengthening mechanism, which promoted electron transport in the anaerobic denitrification degradation of petroleum hydrocarbons by quinone-respiring strain with the aid of electron intermediate, was proposed. The influencing factors were evaluated by using response surface methodology, and the TPH removal was positively related to temperature but negatively to pH.

Temperature-dependent redox zonation, nitrate removal and attenuation of organic micropollutants during bank filtration

River bank filtration (RBF) is considered to efficiently remove nitrate and trace organic micropollutants (OMP) from polluted surface waters. This is essential for maintaining good groundwater quality and providing high quality drinking water. Predicting the fate of OMP during RBF is difficult as the biogeochemical factors controlling the removal efficiency are not fully understood. To determine in-situ removal efficiency and degradation rates of nitrate and OMP indicator substances we conducted a field study in a RBF system during a period of one and a half years incorporating temporally and spatially varying redox conditions and temperature changes typically occurring in temperate climates. RBF was analyzed by means of mixing ratios between infiltrated river water and groundwater as well as average residence times of surface water towards the individual groundwater observation wells. These results were used to calculate temperature dependent first order degradation rates of redox sensitive species and several OMP. Five out of ten investigated OMP were completely removed along RBF pathways. We demonstrate that degradation rates of several OMP during bank filtration were controlled by redox conditions and temperature whereby temperature itself also had a significant influence on the extent of the most reactive oxic zone. The seasonal variations in temperature alone could explain a considerable percentage of the variance in dissolved oxygen (34%), nitrate (81%) as well as the OMPs diclofenac (44%) and sulfamethoxazole (76%). Estimated in-situ degradation rates roughly varied within one order of magnitude for temperature changes between 5 °C and 20 °C. This study highlights that temporal variability in temperature and redox zonation is a significant factor for migration and degradation of nitrate and several OMPs.

Polymer Based Palladium Nanocatalyst for the Degradation of Nitrate and Congo Red

In this study, the Pd catalyst based on chitosan-tannin (CT) framework as support was prepared and characterized. The CT support and Pd catalyst were characterized by attenuated total reflection (ATR) spectroscopy and Raman spectroscopy, Scanning electron microscopy-energy dispersive X-ray analyzer (SEM–EDX) and transmission electron microscopy (TEM) and X-ray diffractometry (XRD). Attenuated total reflection (ATR) spectra revealed the coordination of Pd via hydroxyl and amino functional groups. Raman spectral analysis was carried out to give information about the structural defect of the catalyst compared to CT support. The SEM–EDX results revealed regular surface morphology and presence of Pd in the catalyst as compared to CT support. TEM analysis revealed that the deposition of Pd on organic support with a spherical shape possessing size in the range of 6.01 nm–20.7 nm (average particle size = 12.65 ± 3.14 nm). The XRD results revealed the amorphous nature of the catalyst compared to CT support. TGA analysis revealed that the catalyst is highly thermally-stable compared to CT support. The catalytic activity of Pd catalyst was investigated for the reduction of nitrate and Congo red in the presence and absence of H2. The catalytic activities exhibited 71.11% and 23% removal of nitrate and Congo red in 20 and 60 min, respectively. Thus, results suggested that Pd catalyst has a potential of catalytic activity toward reduction of nitrate and Congo red in presence H2.

High-throughput sequence analysis of bacterial communities in commercial biofertiliser products marketed in South Africa: an independent snapshot quality assessment.

The genetic and predicted functional diversity of bacterial communities in 12 commercial biofertiliser products were evaluated using high-throughput sequencing of the 16S rRNA gene. Proteobacteria, Firmicutes and Bacteroides dominated the bacterial communities, with the genera Pseudomonas, Lactobacillus, Bacillus, Bradyrhizobium and Rhizobium being prevalent. The manufacturer-specified species were detected in relatively high abundance in two of the products while a few or none of the specified species were detected in some products. A number of unspecified microbes were detected, including potential human and crop pathogens such as Alcaligenes, Clostridium, Escherichia-Shigella and Proteus. The functional prediction unravelled high prevalence of enzyme-coding genes such as nitrogenase, NifT, alkaline phosphatase and reductases of nitric oxide, nitrate and nitrite which contribute to nitrogen-fixation, phosphorus solubilisation and degradation of nitrates and nitrites. In addition, toxins such as leukocidin/hemolysin and colicin V protein that cause product quality damage were highly predicted in over 67% of the products. Overall, high-throughput sequence analysis of bacterial communities in biofertiliser products revealed that majority of the products were of poor quality. This result justifies the need for regular quality assessment and improvement in quality control systems during biofertiliser formulation.

Microbial Degradation of Nitrate: Put Microbes to Work

Microbial Degradation of Nitrate: Put Microbes to Work

Effects of Coadsorbed Water on the Heterogeneous Photochemistry of Nitrates Adsorbed on TiO2.

Nitric acid, a well-known sink of NO x gases in the atmosphere, has been found to be photoactive while adsorbed on tropospheric particles. When adsorbed onto semiconductive metal oxides, nitrate's photochemical degradation can be interpreted as a photocatalytic process. Yet, the photolysis of nitrate ions on the surface of aerosols can also be initiated by changes in the symmetry of the ion upon adsorption. In this study, we use quantum chemistry to model the vibrational spectra of adsorbed nitrate on TiO2, a semiconductor component of atmospheric aerosols, and determine the kinetics of the heterogeneous photochemical degradation of nitrate under simulated solar light. Frequencies and geometry calculations suggest that the symmetry of chemisorbed nitrate ion depends strongly on coadsorbed water, with water changing the reactive surface of TiO2. Upon irradiation, surface nitrate undergoes photolysis to yield nitrogen-containing gaseous products including NO2, NO, HONO, and N2O, in proportions that depend on relative humidity (RH). In addition, the heterogeneous photochemistry rate constant decreases an order of magnitude, from (5.7 ± 0.1) × 10-4 s-1 on a dry surface to (7.1 ± 0.8) × 10-5 s-1 when nitrate is coadsorbed with water above monolayer coverage. Little is known about the roles of coadsorbed water on the heterogeneous photochemistry of nitrates on TiO2, along with its impact on the chemical balance of the atmosphere. This work discusses the roles of water in the photolysis of surface nitrates on TiO2 and the concomitant renoxification of the atmosphere.

Study of structural transformation and hysteresis behavior of Mg-Sr substituted X-type hexaferrites

Effect of Mg-Sr substitution on thermal, structural, spectral, dielectric and magnetic properties were explored in the X-type hexagonal ferrites having composition of Ba2-xMgxCo2-ySry Fe28O46 (x = y = 0, 0.1, 0.2, 0.3, 0.4, 0.5) synthesized via a sol-gel auto-combustion process. The sintered material was characterized by differential scanning calorimetry (DSC), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), dielectric measurement and vibrating sample magnetometer (VSM) techniques. The sintering temperature necessary for the entire degradation of nitrates and the hexagonal phase development was found 1250 °C which was determined from thermo-gravimetric analysis. The formation of the single phase hexagonal was confirmed from XRD patterns. The lattice constants and cell volume were found to be decreased. This decreased was attributed to the lower ionic size of the substituted metal ions. The porosity of the synthesized material was found to be decreased from 0.463 to 0.417 with the increase in the substitution. FTIR spectroscopy of Mg-Sr doped material revealed the characteristics absorption bands of hexa-ferrites and it was investigated in the frequency range of 400–1000 cm−1. The dielectric measurement has been explored as the function of frequency and composition. Ac conductivity was found to be increased from 1.46 to 2.029 Ω cm−1. The Cole-Cole graphs of prepared materials revealed the promising role of grain boundaries in the conduction mechanism. The improvement in the coercivity was observed with the increase in the Mg-Sr cations, while the saturation magnetization was decreased with the increase in the substitution. The higher value of the coercivity of these synthesized material proposed their use in longitudinal recording media.

Degradation of nitrate and secondary pollution in drinking water by S-NZVI prepared from steel pickling waste liquor

In this study, degradation of nitrate in drinking water by nanoscale zero-valent iron prepared from steel pickling waste liquor(S-NZVI) was investigated. Transmission Electron Microscope (TEM), Scanning Electron Microscope (SEM) and Specific Surface Area Analyzer (BET) were used to characterize the properties of the synthesized nanoparticles. Effects of different parameters, such as S-NZVI dosage, initial nitrate concentration, and pH, on the denigration were conducted. The results showed that S-NZVI had the similar characteristic of the NZVI prepared by chemical agents. The experiments indicated that the slightly acid medium with the S-NZVI dosage of 2.8 g/L had a better removal effect of nitrate, and the high removal efficiency of 96% was observed after the reaction time of 2 h, which demonstrated it was feasible and effective to remove nitrate by S-NZVI. The kinetic studies indicated that the degradation rate of nitrate by S-NZVI followed the pseudo-first order kinetics. By analyzing the end-products of nitrate reduction, 94% of nitrate was converted into ammonia ions by S-NZVI and the others translated into a little amount of nitrite and nitrogen. It is a relatively easy and cost-effective method for nitrate removal, so S-NZVI has a great potential application in nitrate removal of drinking water. The ammoniac nitrogen pollution, the main product and second pollution from the denitrification by S-NZVI can be completely degraded by cation exchange resin. So the nitrogen pollution has been completely removed from drinking water polluted by nitrate.

Insights into the degradation of (CF3)2CHOCH3 and its oxidative product (CF3)2CHOCHO & the formation and catalytic degradation of organic nitrates

In this work, a systematic investigation of the atmospheric oxidation mechanism of (CF3)2CXOCH3 and their oxidative products (CF3)2CXOCHO (X = H, F) initiated by OH radical or Cl atom is performed by density functional theory. This study reveals that the introduction of NO and O2 promotes the formation of organic nitrates, which are hygroscopic and are inclined to form secondary organic aerosols (SOA) and can affect the air quality. The rate constants of the individual reactions are found to be in agreement with the experimental results. One of the intriguing findings of this work is that the peroxynitrite of (CF3)2CHOCH2OONO formed from the subsequent reactions of (CF3)2CHOCH3 is more favorable to isomerize to organic nitrate (CF3)2CHOCH2ONO2 than to dissociate into alkoxy radical (CF3)2CHOCH2O and NO2 because of the lower energy barrier of isomerization. The second significant observation is that the organic nitrate can be degraded more favorably with the presence of NH3, CH3NH2, and CH3NHCH3 than its naked decomposition reaction (CF3)2CHOCH2ONO2→(CF3)2CHOCHO + HONO. The ammonium salt, a vital part of haze, is harmful to human health and can be formed in the existence of the NH3, CH3NH2, and CH3NHCH3. In addition, the toxic substance of peroxyalkyl nitrate (CF3)2CHOC(O)ONO2 which can reduce the visibility of the atmosphere is produced as the primary subsequent oxidation product of (CF3)2CHOCHO in a NO-rich environment. The main species detected experimentally are confirmed by this study. The computational results are crucial to risk assessment and pollution prevention of the volatile organic compounds (VOCs).

Dynamics of Nitrite Content in Fresh Spinach Leaves: Evidence for Nitrite Formation Caused by Microbial Nitrate Reductase Activity

Nitrite (NO2-) contained in dietary foods has long been recognized for its toxicity as the causative agent of methemoglobinemia and also as a source of mutagenic nitrosamines. Because of these potential toxicities, nitrite as well as nitrate contained in foods and drinks are strictly limited by regulations in many countries. Recent studies have offered us to update our recognition of nitrite; nitrite is an important precursor for Nitric Oxide (NO) that is required for fundamental physiological activities including vasorelaxation. Although it is well established that green vegetables contain high amounts of nitrate, there has been controversy regarding the source of nitrite accumulation in fresh green vegetables. In this study, we investigated the dynamics of nitrite and nitrate contents in spinach leaf extracts to verify the mechanisms of nitrite formation. The time course of nitrite production in leaf extracts showed a reciprocal relationship with nitrate degradation, suggesting a conversion from nitrate to nitrite. The reaction strongly depended on temperature and it was suppressed at a low temperature. Sodium tungstate, a nitrate reductase enzyme inhibitor, was effective to suppress the conversion. Pre-sterilization by autoclaving or filter sterilization completely prevented the formation of nitrite as well as degradation of nitrate. We suggest that previous reports of nitrite accumulation can be attributed to microbial nitrate reductase activities that occur during the degradation spinach leaves.

New Solid-Base Cu-MgO for CO2 Capture at 473 K and Removal of Nitrosamine.

To fabricate a new solid base with high efficiency in the adsorption of CO2 at 473 K and catalytic activity in the degradation of nitrosamines, magnesium oxalate and copper nitrate are mixed with the assistance of microwave irradiation followed by calcination to immobilize CuO among MgO particles. The binary solid base CuO-MgO is thus moderately reduced to form the Cu-inserted MgO composite with highly exposed strong basic sites, and it can capture 34.6 mg g-1 of CO2 in the harsh instantaneous adsorption at 473 K and keep a high strong basicity while trapping the CO2 mixed with SO2 and NO. Besides this, the new solid base exhibits high activity in the removal of volatile nitrosamine N-nitrosopyrrolidine (NPYR), for the first time expanding the application of solid bases to environmental catalysis.

Facile Synthesis of High-Surface-Area Mesoporous MgO with Excellent High-Temperature CO2 Adsorption Potential

Mesoporous magnesium oxide of high surface area (>350 m2/g) has been synthesized by a simple ammonia precipitation method from an aqueous magnesium nitrate solution. This material has been evaluated for CO2 adsorption in the temperature and pressure regimes relevant to precombustion capture in an integrated gasification combined cycle scheme. CO2 adsorption capacities were also compared with those of magnesium oxides obtained by other synthetic routes such as hydrothermal urea hydrolysis and direct thermal degradation of magnesium nitrate. Mesoporous magnesium oxide shows a CO2 capacity at high temperatures that is comparable or even exceeds the capacity values for this class of high-temperature CO2 adsorbents reported in the literature so far. The materials studied have been characterized by various characterization techniques like powder X-ray diffraction, surface area, pore-size distribution analysis, scanning electron microscopy, and Fourier transform infrared. A cyclic adsorption/desorption study was...

Synthesis, structural and thermal behavior study of four Ca-containing silicate gel-glasses

Calcium silicate amorphous materials of general formula xCaO·(1–x)SiO2, being 0.3 ≤ x ≤ 0.6, and pure silica (SiO2) have been prepared by the sol–gel method and characterized by X-ray diffraction. Freshly prepared glassy samples of these materials were reduced to fine powders by gentle grinding in an agate mortar. Subsequently, a simultaneous thermogravimetry (TG) and differential thermal analysis equipment was used to study their thermal behavior under a stream of argon in the temperature range from room temperature to 1200 °C. All samples undergo dehydration up to 250 °C followed by a second process with a slight mass loss in the range 350–500 °C due to the thermal degradation of the residual nitrate, followed by a third endothermic process ascribed to dehydroxylation, due to evolution of water by condensation of the OH– surface groups, took place between 500 and 600 °C. At high temperatures, around 900 °C, all gel-glasses undergo an exothermic process without mass changes ascribed to crystallization. A reliable isoconversional procedure was applied to investigate the conversion dependency of activation energy for the thermally activated release of water molecules physically or chemically bound to the structure of the materials as well as that to dehydroxylation. The results obtained were discussed in terms of the different water absorption capabilities related to their different molar ratio Ca/Si and, depending on the amount of Ca, to the formation of one or more calcium silicate phases that crystallize at high temperature.

Effects of anions on bio-chemical degradation of nitrate in groundwater

Combining denitrifying bacteria with sodium oleate-nanoscale zero-valent iron (SONZVI) has been proven to be effective for aqueous phase nitrate remediation. However, the effects of coexistent ions on nitrate reduction in a groundwater environment, which is at low temperature and under anoxic, light-excluded conditions, remain elusive. In this study, nitrate reduction by microbial-NZVI was evaluated via batch tests in the presence of common anions (SO4 2−, PO4 3− and Cl−) in two different environments: groundwater environment and room environment. The results showed that nitrate was largely reduced within 10 days in an SONZVI + cell reactor in the groundwater environment, while only 79 % of the nitrate was reduced over 10 days in the room environment. In the groundwater environment, the removal efficiency could be accelerated by chloride or phosphate, but inhibited by sulfate. There were mainly two reaction stages, which were chemical reduction degradation and denitrifying degradation. Pseudo-first-order kinetics was used to describe the two reaction stages. In the first stage, the existence of the anions inhibited nitrate degradation. The synergistic effects of these anions on nitrate removal followed the order of Cl−, SO4 2−, and PO4 3−. The results implied that using microbial-NZVI is a potential approach for in situ remediation of groundwater with nitrate contamination.