Removal Of Nitrate In Water Research Articles

Biocomposites based on chitosan and orange peel as a green material alternative for the removal of nitrate in water

Biocomposites based on chitosan and orange peel as a green material alternative for the removal of nitrate in water

Sulfur autotrophic electrodialysis ion exchange membrane bioreactor (SEDIMB) for nitrate removal in water: Synergism and adaptability of electrodialysis and sulfur autotrophy

In this study, the novel sulfur autotrophic electrodialysis ion-exchange membrane bioreactor (SEDIMB) with high denitrification performance was developed without the addition of carbon source. Sulfur autotrophic denitrification occurs at the same time of nitrate enrichment by electric field to achieve harmless nitrate transformation in water. The final nitrate concentration in water chamber was 2.16 mg-N/L (removal efficiency of 94.49 %) at an initial nitrate concentration of 40 mg-N/L, with the maximum nitrate concentration in biological chamber of 4.09 mg-N/L. Nitrate removal in water chamber of the SEDIMB conformed to the first-order kinetic model (R2 = 0.98) and reaction rate constant K1 = 0.0030 (1/min). The effect of environmental variables (i.e., voltage, initial nitrate concentration and water body) on the SEDIMB denitrification performance was investigated. Increasing voltage could promote nitrate migration in water chamber, and when the voltage was 7 V, initial nitrate concentrations of 20 ∼ 60 mg-N/L was effectively removed (all > 93.54 %). Moreover, the change of water body (i.e., tap water, lake water and deionized water) did not affect denitrification performance of SEDIMB. Microbial community structure analysis indicated that Betaproteobacteria were dominant in the SEDIMB. Membrane characterizations (ATR-IR, SEM and CLSM) confirmed that the bacteria in biological chamber tended to accumulate and grow on one side of the anion exchange membrane (AEM), while could not affect the selective permeability of AEM.

Effective removal of nitrate in water by continuous-flow electro-dialysis ion exchange membrane bioreactor (CF-EDIMB): Performance optimization and microbial analysis

The use of nitrogen fertilizer has been causing nitrate pollution in groundwater, and there is an urgent need for efficient approach to remove nitrate from groundwater. In our job, a novel continuous-flow electrodialysis ion exchange membrane bioreactor system (CF-EDIMB) was set up to remove nitrate (NO3−) from water for the first time. Nitrate removal was positively dependent on water chamber HRT and voltage; voltage had significant effect on the water chamber effluent pH; acetate utilization efficiency was closely correlated with acetate dosage. The optimal conditions forecasted through response surface method (RSM) were given as follows: water chamber HRT was 20 h, biological chamber HRT was 24 h, voltage was 6.65 V and acetate dosage was 454.99 mg/L, dedicating to nitrate removal of 81.90% (83.70% in prediction), water chamber effluent pH of 7.10 (7.00 in prediction) and acetate utilization efficiency of 92.87% (96.51% in prediction). Meanwhile, microorganisms are crucial for nitrate removal, and the microbial community was not sensitive to the variation of acetate dosage. The microbial analysis results indicated that when CF-EDIMB system was operated for 20 d, the sulfate-reducing bacteria Sediminibacterium appeared in the biological chamber, and the effluent sulfate concentration of biological chamber was decreased. During the whole operation, Thauera was the dominant genus. Denitrifying functional genes nirS presented a better expression than the gene narG, and there was no accumulation of nitrite.

Nitrate (NO3-) removal from wastewater by adsorption using modified kaolin

This study aims to determine the effect of the initial concentration and pH conditions of the nitrate solution on the removal of nitrate in water, which was carried out in batch. The raw material used is kaolin, which is firstly mashed and sieved with a size of 120 mesh, then activated by immersing it in a 0.5 M HCl solution for 24 hours, followed by modification of the surfactant by immersion in a 0.5 M cetyltrimethyllammonium bromide (CTABr) solution for 120 minutes, and accompanied by stirring using a magnetic stirrer at a speed of 150 rpm. Before being used as an adsorbent, kaolin CTABr-modified was analyzed using a scanning electron microscope (SEM) to determine the surface morphology of the material. Batch adsorption test was carried out by adding 1 gram of kaolin CTABr-modified to 100 mL of a solution containing nitrate with various concentrations of 10; 20; 30 mg/L and the pH of the solution is 5; 7; 8. The experiment was carried out for 180 minutes, where every 30 minutes the solution was sampled and analyzed for nitrate content using a spectrophotometer UV-Vis. The conclusion of this study is that kaolin CTABr-modified can be used as an adsorbent, where the SEM test results show that the surface morphology of kaolin CTABr-modified is denser and more compact than the prepared kaolin and kaolin HCl-activated. Based on the experimental results according to the Langmuir isotherm equation, the constant value was 0.78. The mechanism of nitrate removal includes ion exchange, hydrogen bonding, and intermolecular interactions. The maximum adsorption capacity was 0.72 mg/g, found under acidic conditions (pH 5) and with a contact time of 180 minutes.

Synthesis of cation exchange resin-supported iron and magnesium oxides/hydroxides composite for nitrate removal in water

In this study, we reported on the concept and practical use of cation exchange resin (CER) for removing anions in water via pretreating the CER with metal salts. The cation exchange resin-supported iron and magnesium oxides/hydroxides composite (Fe-Mg/CER) was synthesized and introduced as a new and potential adsorbent for selective removal of nitrate ion in the water environment. Characteristics of Fe-Mg/CER were determined by techniques such as Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction. The results showed that Fe-Mg/CER material had a high nitrate adsorption capacity of 200 mg NO3−·g−1 with a fast equilibrium adsorption time of 30 min at pH 5. In addition, it had good durability of at least 10 times of regeneration, which could be applied to practical water and wastewater treatment.

Time-delayed photocatalysis enhanced microbial nitrate reduction via solar energy storage in carbon nitrides

The increase in nitrogen, especially nitrate, in the water environment poses a great threat to human health and makes the need to develop ways to efficiently remove nitrate from water. Here, we established a novel time-delayed denitrification system for the first time using dark photocatalyst, the cyanamide-functionalized heptazine-based polymer (NCN-CNx). Interestingly, the dark photocatalysis system can store electrons when being irradiated, and release them as needed when being coupled with a conductive co-catalyst in dark environment. The changes in concentration of nitrate, nitrite and ammonia were measured to state the improved denitrification performance, and the enzyme activities and electrochemical behaviors were investigated to explore the mechanism of the denitrification system. The results showed that NCN-CNx had a positive effect on the microbial nitrate removal process because of the release of stored photogenerated electrons. Electrons released by a co-catalyst (graphene) on demand could promote microbial denitrification with a 77% nitrate removal efficiency, which was almost 4.8 times and 3.1 times higher than that of the photocatalytic group and the microbial group. Correlation analysis indicated that the activities of nitrate reductase, nitrite reductase, and catalase as well as electron transport system were the most important relative factors affected by NCN-CNx during the denitrification process. Furthermore, bacterial community analysis revealed that NCN-CNx increased the relative abundance of denitrifiers, including Sphingomonadaceae, Xanthomonadaceae and Cyclobacteriaceae, in the treated communities compared with the original community in river sludge. These findings provided some new insights into the mechanism by which dark photocatalyst can enhance the denitrification process and the establishment of day/night photocatalytic systems for sustainable removal of nitrate in water.

Denitrification Kinetics of Nitrate by a Heterotrophic Culture in Batch and Fixed-Biofilm Reactors

Herein, the progress of nitrate removal by a heterotrophic culture in a batch reactor and continuous-flow fixed-biofilm reactor was examined. Two batch experiments for nitrate reduction with acetate degradation using 250 mL batch reactors with acclimated denitrifying biomass were conducted. The experimental results indicated that the nitrate was completely reduced; however, the acetate remained at a concentration of 280 mg/L from initial nitrate concentration of 100 mg/L. However, the acetate was fully biodegraded by the denitrifying biomass at an initial nitrate concentration of 300 mg/L. To evaluate the biokinetic parameters, the concentration data of nitrate, nitrite, acetate, and denitrifying biomass from the batch kinetic experiments were compared with those of the batch kinetic model system. A continuous-flow fixed-biofilm reactor was used to verify the kinetic biofilm model. The removal efficiency of nitrate in the fixed-biofilm reactor at the steady state was 98.4% accompanied with 90.5% acetate consumption. The experimental results agreed satisfactorily with the model predictions. The modeling and experimental approaches used in this study could be applied in the design of a pilot-scale, or full-scale, fixed-biofilm reactor for nitrate removal in water and wastewater treatment plants.

Application of glycerol as carbon source for continuous drinking water denitrification using microorganism from natural biomass

The contamination of water resources by nitrate is a global problem. Indeed, traditional treatment technologies are not able to remove this ion from water. Alternatively, biological denitrification is a useful technique for natural water nitrate removal. This study aimed to evaluate the use of glycerol as a carbon source for drinking water nitrate removal via denitrification in a reactor using microorganisms from natural biomass. The experiment was carried out in a continuous fixed bed reactor using immobilised microorganisms from the vegetal Phyllostachys aurea. The tests were started in batch mode to provide cells growth and further immobilisation on the support. Then, the treatment experiments were accomplished in an up-flow continuous reactor. Ethanol was used as the primary carbon source, and it was gradually replaced by glycerol. The C:N (carbon to nitrogen) ratio and the hydraulic residence time (HRT) were evaluated. It was possible to remove 98.14% of nitrate using a C:N ratio and HRT of 3:1 and 1.51 days, respectively. The results have demonstrated that glycerol is a potential carbon source for denitrification in a continuous reactor using immobilised cells from natural biomass.

A Study on the Nitrate Removal in Water by Chelating Bond of Calcium Alginate

A Study on the Nitrate Removal in Water by Chelating Bond of Calcium Alginate

Effects of Nitrate in Water on the Growth of Iris pseudacorus L. and Its Adsorption Capacity of Nitrogen in a Simulated Experiment

In order to provide references for the application of emergent plants in the remediation and restoration of aquatic ecosystems, a hydroponic experiment was conducted for Iris pseudacorus L. with different nitrate mass concentrations (i. e., 10.68, 23.88, 42.22, 63.33, 82.92, 97.13 mg·L-1). The effects of nitrate mass concentration in water on the growth and nitrogen absorption capacity of I. pseudacorus were evaluated by the aboveground biomass, belowground biomass, root-shoot ratio, chlorophyll content, nitrogen uptake, and nitrate removal efficiency of the plants. The following results were obtained from the experiment. 1 The effects of nitrate mass concentration on the aboveground (stems and leaves) growth of the I. pseudacorus were greater than that on the belowground (roots) growth. Compared with the values before the experiment, the root-shoot ratio of the I. pseudacorus increased in the treatment with 10.68 mg·L-1 of nitrate mass concentration; while the root-shoot ratio decreased in the treatments with 42.22-97.13 mg·L-1 of nitrate mass concentration. 2 The I. pseudacorus grew better with nitrate mass concentration ranging from 23.88 mg·L-1 to 63.33 mg·L-1; and the chlorophyll biosynthesis of the plants was inhibited in the treatments with 10.68, 82.92, and 97.13 mg·L-1 of nitrate mass concentration. 3 The total nitrogen accumulation of the I. pseudacorus was in range of 10.56-75.43 mg in the experiment, which increased with the increase of nitrate mass concentration; and the accumulation of nitrogen in the belowground parts was 7.2, 2.3, 2.5, 2.1, 1.6, and 1.5 times of that in the aboveground parts, respectively. 4 The nitrogen utilization efficiency of the aboveground parts was higher than that of the belowground parts. 5 The removal rates of nitrate by I. pseudacorus were 94.9%-99.3%, which increased with increasing nitrate mass concentration. The nitrate mass concentration in water decreased with time in exponential function. In conclusion, I. pseudacorus has promising performance in the removal of nitrate in water, but its growth, nitrogen adsorption, and nitrate removal rate were significantly affected by the nitrate mass concentration. Moreover, the response of growth and nitrogen adsorption in aboveground of I. pseudacorus to nitrate mass concentration was more sensitive than that in belowground.

Characteristics of a Combined Heterotrophic and Sulfur Autotrophic Denitrification Technology for Removal of High Nitrate in Water

A combined heterotrophic and sulfur autotrophic denitrification technology for NO3--N wastewater treatment was started up by adding elemental sulfur in the heterotrophic denitrifying reactor, and the characteristics of pH constant and sludge reduction were studied. The results showed that the sulfur autotrophic denitrification bacteria in heterotrophic denitrifying reactor could achieve rapid growth. After running for 65d, TOC/N was controlled between 0.65 and 0.75, and the combined denitrification process did not require external alkalinity supplementation as the alkalinity need of autotrophic denitrifiers was supplemented by the heterotrophic denitrifiers. After running for 116d, the total nitrogen removal rate reached above 85%, and the denitrification efficiency was kept steady at 2.5 kg·(m3·d)-1. Compared to heterotrophic denitrification, the sludge production was greatly reduced, which was only 60% of that produced in combined heterotrophic and sulfur autotrophic denitrification reactor. NO2--N accumulated by using collaborative denitrification treatment of high concentration of NO3--N wastewater, the concentration reached 20 mg·L-1 even at the eventual plateau stage, which would require deep processing.

Green synthesis of polypyrrole-supported metal catalysts: application to nitrate removal in water

Pt and Pt/Sn catalysts supported on polypyrrole (PPy) have been prepared using Ar plasma to reduce the metal precursors dispersed on the polymer.

Activated carbon supported metal catalysts for reduction of nitrate in water with high selectivity towards N2

The catalytic removal of nitrate in water with hydrogen was investigated by using different activated carbon-supported metal catalysts. A commercial activated carbon (CAC) and one prepared by chemical activation of grape seeds with phosphoric acid (GS) were evaluated for the preparation of bimetallic catalysts (Pd–Cu, Pd–Sn and Pd–In). The support plays an important role in the catalytic performances for nitrate removal, affecting both activity and selectivity. Pd–Cu catalyst supported on GS showed the highest nitrate removal activity and nitrite was not found as by-product. The acidity of the reaction medium is associated with this behavior, attributing this effect to the chemical composition of the catalyst support. Control of pH through CO2 addition to the reaction medium was beneficial in the case of the Pd–Cu catalyst prepared with CAC. However, no significant influence was observed in the case of the GS-supported catalyst. The concentration of promoting metal affects more strongly the catalyst performance than that of Pd. Low Cu contents (0.5 and 1.5wt.%) within the range tested (0.5–5wt.%) led to the highest selectivity towards the undesired ammonium ion. The catalysts supported on GS with 2.5% Cu and 5% Pd allowed achieving the European Standards for drinking water when a 100mg/L nitrate starting solution was treated, in terms of nitrate, nitrite and ammonium concentrations. The Pd–based bimetallic catalysts containing Sn and In as promoting metal showed a lower catalytic activity and significantly higher selectivity towards ammonium.

The use of a cation exchange resin for palladium–tin and palladium–indium catalysts for nitrate removal in water

A sulfonated poly(styrene–divinylbenzene) (Sty–DVB) was used for preparing bimetallic palladium–tin or palladium–indium catalysts by successive impregnation and catalytic reduction. The use of this acidic support allows increasing the selectivity to molecular nitrogen without external control of the pH, as compared to a classical alumina catalyst. The preparation by successive impregnation led to the most active and selective catalysts while the indium-based catalysts were more active for nitrate reduction and less selective to nitrogen than the tin-based ones. The best performances were obtained with the 5%Pd2.6%Sn/Sty–DVB prepared by successive impregnation. This finding was related to the role of the support in decreasing the final pH, as well as to the buffering properties of the support near the active metal sites.

Study of a combined heterotrophic and sulfur autotrophic denitrification technology for removal of nitrate in water

A combined two-step process of heterotrophic denitrification in a fluidized reactor and sulfur autotrophic denitrification processes (CHSAD) was developed for the removal of nitrate in drinking water. In this process, the advantage of high efficiency of heterotrophic denitrification with non-excessive methanol and the advantage of non-pollution of sulfur autotriphic denitrification were integrated in this CHSAD process. And, this CHSAD process had the capacity of pH balance and could control the concentration of SO 4 2− in effluent by adjusting the operation condition. When the influent nitrate was 30 mg NO 3 −–N/L, the reactor could be operated efficiently at the hydraulic retention time (HRT) ranging from 20 to 40 min with C:N ratio (mg CH 3OH:mg NO 3 −–N) of 2.0 (methanol as carbon source). The nitrate removal was nearly 100% and there was no accumulated nitrite or residual methanol in the effluent. The effluent pH was about 7.5 and the sulfate concentration was lower than 130 mg/L. The maximum volume-loading rate of the reactor was 2.16 kg NO 3 −–N/(m 3 d). The biomass and scanning electron microscopy graphs of biofilm were also analyzed.

A Two-stage Catalytic Process with Cu–Pd Cluster/Active Carbon and Pd/β-Zeolite for Removal of Nitrate in Water

Abstract To purify water contaminated with nitrate, a two-stage process was employed, involving nitrate hydrogenation to nitrite in the first stage (pH = 10.5) using 0.87 wt% Cu–Pd (2:1) cluster/AC, and nitrite hydrogenation in the second stage (pH = 6.5) with 1.0 wt% Pd/β-zeolite. The nitrate (100 ppm) was hydrogenated rapidly, suppressing ammonia levels to within concentrations acceptable for drinking water.

Effect of the support on tin distribution in Pd–Sn/Al2O3 and Pd–Sn/SiO2 catalysts for application in water denitration

The reduction of nitrate to nitrogen is a key process for nitrate removal in water. Among others bimetallic, palladium tin catalysts are well suited for this purpose. In the present study Pd–Sn catalysts are used and characterized in the mentioned process. Alumina and silica supported catalysts were prepared by deposition of tin onto palladium particles by using controlled surface reaction. The accessibility of palladium and the amount of reducible tin are tested by O2/H2/O2 titration. The structural characterization is based on 119Sn Mössbauer spectroscopy, TEM, XRD, and catalytic performances are tested in nitrate and nitrite reductions at room temperature. Remarkably, the properties of Pd–Sn/Al2O3 and Pd–Sn/SiO2 are different, although they were prepared according to the same procedure. Namely, the silica supported catalyst is more stable and selective, but is less active than the alumina supported one. This could be explained by the difference of (i) the interaction between the two metals and (ii) the affinity of tin with the support depending on the support used. The characterization results are interpreted with respect to the catalytic behavior of the materials.

Rapid removal of nitrate in water by hydrogenation to ammonia with Zr-modified porous Ni catalysts

Hydrogenation of nitrate in water was carried out in the presence of Ni-based solid catalysts. When the hydrogenation was performed on 200ppm (mgdm−3) of nitrate, our results showed that, among various base metals, porous Ni was most active forming predominantly NH3, while Ni rapidly deactivated during the reaction. Remarkably, subsequent studies revealed that addition of a small amount of Zr greatly enhanced the stationary activity of porous Ni. To the best of our knowledge, this is the first example of a noble metal-free catalyst exhibiting high catalytic activities for the hydrogenation of nitrate in water. It was found that the loading amount of Zr greatly influenced the activity, in which the addition of 0.5% Zr (w/w) exhibiting the maximum activity. XPS measurements revealed that Zr played an important role in suppressing the oxidation of the Ni0 atoms, thus maintaining the active Ni surface. Furthermore, the addition of Zr prevented the blockage of pores of Ni, thus preserving the mesopore structures. These effects of Zr serve to increase the stationary activity of porous Ni. Since it was confirmed that Ni does not dissolve during the reaction, the novel catalytic system can be applicable to the treatment of industrial wastewater, combining the recycle system of NH3.

Removal of Nitrate in Water by Hydrogenation with a Noble Metal‐Free Ni‐Base Catalyst.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Removal of Nitrate in Water by Hydrogenation with a Noble Metal-Free Ni-Base Catalyst

Abstract Porous Ni catalyst modified with a small amount of Zr was found to be highly active for hydrogenation of nitrate (200 ppm) in water at 333 K. This is the first example of noble metal-free catalyst effective for this reaction.