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Nitrate (NO 3 –) is a widespread pollutant in high-salt wastewater and causes serious harm to human health. Although electrochemical removal of nitrate has been demonstrated to be a promising treatment method, the development of low-cost electro-catalysts is still challenging. In this work, a phosphate modified iron (P-Fe) cathode was prepared for electrochemical removal of nitrate in high-salt wastewater. The phosphate modification greatly improved the activity of iron, and the removal rate of nitrate on P-Fe was three times higher than that on Fe electrode. Further experiments and density functional theory (DFT) calculations demonstrated that the modification of phosphoric acid improved the stability and the activity of the zero-valent iron electrode effectively for NO 3 – removal. The nitrate was firstly electrochemically reduced to ammonium, and then reacted with the anodic generated hypochlorite to N 2. In this study, a strategy was developed to improve the activity and stability of metal electrode for NO 3 – removal, which opened up a new field for the efficient reduction of NO 3 – removal by metal electrode materials. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, the surface of duck feather was modified with (3-chloropropyl) trimethoxysilane and (1,4-diazabicyclo[2.2.2]octane), and it was used as a natural polymeric adsorbent to remove nitrate ion from a solution. The prepared modified duck feather was characterized using TGA, FT-IR, and FE-SEM analyses. The study examined the effect of various parameters such as pH, contact time, adsorbent dosage, and initial concentration of nitrate on adsorption efficiency. pH = 7, 40 min contact time, 30 mg of adsorbent, and 40 mg/L initial concentration of nitrate were found as the optimum conditions offering the maximum efficiency of 91.85% and maximum adsorption capacity of 30.62 mg/g. Also considered were various competing anions together with nitrate ions in the solution. The results revealed that maximum nitrate adsorption could be obtained in the presence of phosphate anion via ion exchange mechanism. It could also offer the best fit for the adsorption isotherm and kinetic model for Langmuir and pseudo-second-order models. The investigation of thermodynamic parameters at 25 °C revealed that the ΔG°, ΔH°, and ΔS° were obtained −5.44, −46.56, and −0.14 kJ mol−1 K−1, respectively. [ABSTRACT FROM AUTHOR]

The nitrate-based compounds are seriously poisonous to the environment, ecology, and human life. The environmental systems are contaminated with the propagation of nitrate-based compounds. To keep all the sources of water safe, there is a need to monitor the contaminated ions regularly as water pollution is a major concern globally. Therefore, the correct application of methods for the detection and quantification of nitrate from environmental samples is a crucially important task in analytical chemistry. On the other hand, with no less importance, the developing new routes for removal of this pollutant from the environmental system is a striking purpose for the scientists. This manuscript provides an overview of the importance of monitoring and detecting nitrate-based compounds in environmental samples, as well as removing them to ensure safety of water resources. Various modern analytical chemistry methods for detecting and quantifying nitrate, such as spectrophotometric method, infrared spectroscopy, atomic absorption spectroscopic method, nuclear magnetic resonance method, chromatography, biosensors, and Raman spectroscopy method are reviewed and discussed in depth. The review also highlights the significance of developing new removal routes for nitrate contaminants in the environment. This review covers the main characteristics, fundamental concepts, recent trends, and future perspectives of these modern detection and removal techniques. By including all these elements in this review, it can give readers a comprehensive understanding of the discussed issues and will serve as a valuable contribution to the scrutinised fields. [ABSTRACT FROM AUTHOR]

Nitrate (NO3 –) pollution of water sources are a global issue, and gets transformed into nitrite (NO2 –) when in contact with the saliva, resulting in a significant health implication. Groundwater from Tandari Budum, Maiduguri, Nigeria, was denitrified in this study by varying the black plum seed (BPS) adsorbent dosage, contact time, temperature and pH in the range of 0.1-1.0g, 20-140 min, 30-90℃ and 5-11, respectively. From the Draper-Lin small composite design (DSCD) 18 runs optimization studies on NO3 – concentration and adsorption capacity (qe) responses carried out, it was found that time and temperature have the most impact on the process. For NO3 – reduction to 45 mg/L maximum value, optimal factors were 60℃, 80-85 min, pH = 8 and 0.4g dose; whereas for qe (13.7 mg/g), it is pH = 8, dose = 0.4g, 20 min time and 39℃. There was an observed slight similarity (in the optimal outputs), differences (in the optimal factors) and discrepancies in results obtained from non-standardized experimental runs conducted initially when compared with the DSCD design of experiment (DOE). But then, the Statgraphic Centurion 19-X64 v. 19.6.04 software analysis gave a more reasonable findings, which fits a quadratic model at R² = 0.9295 (predicted NO3 – reduction) and 0.9068 (estimated qe). Since an alkaline pH, shorter time, moderate temperature and little resources are needed to attenuate NO3 – (initially at 123 mg/L) from Tandari Budum groundwater, BPS is a novel adsorbent discovered in this study, corresponding to 63.41% removal efficiency. [ABSTRACT FROM AUTHOR]

Water, a vital resource for ecosystems and human populations, is facing increasing nitrate contamination due to agricultural runoff, industrial discharge and improper waste disposal. The present study focuses on the efficacy of nitrate removal through adsorption using fuller's earth (FE) and modified fuller's earth (acid-treated) (MFE) as adsorbents. The impact of initial pH (2.0–7.0), contact time (5–240 min), adsorbent dosage (1–30 g/L), initial nitrate concentration (50–250 mg/L) and temperature (30–50°C) on nitrate removal using fuller's earth were studied. The maximum nitrate removal was observed at pH 2.0, and equilibrium was reached in 120 min at 30℃. The Freundlich isotherm best fit the equilibrium data. The maximum nitrate uptake of fuller's earth and modified fuller's earth were 84.75 mg/g and 85.47 mg/g, respectively. Nitrate removal by FE and MFE followed a second-order kinetic equation. Thermodynamic studies showed spontaneity and the exothermic nature of the nitrate adsorption process. ∆H° values were −44.96 and −42.63 kJmol−1 for FE and MFE and ΔS° was −85.11 and −74.52 Jk−1mol−1 for FE and MFE, respectively. FE, known for its exceptional adsorption capacity owing to its porous structure and high ion-exchange capacity, has demonstrated a remarkable affinity for nitrate ions in batch studies. [ABSTRACT FROM AUTHOR]

Nitrate (NO3–) pollution of water sources are a global issue, and gets transformed into nitrite (NO2–) when in contact with the saliva, resulting in a significant health implication. Groundwater from Tandari Budum, Maiduguri, Nigeria, was denitrified in this study by varying the black plum seed (BPS) adsorbent dosage, contact time, temperature and pH in the range of 0.1-1.0g, 20-140 min, 30-90℃ and 5-11, respectively. From the Draper-Lin small composite design (DSCD) 18 runs optimization studies on NO3– concentration and adsorption capacity () responses carried out, it was found that time and temperature have the most impact on the process. For NO3– reduction to 45 mg/L maximum value, optimal factors were 60℃, 80-85 min, pH = 8 and 0.4g dose; whereas for (13.7 mg/g), it is pH = 8, dose = 0.4g, 20 min time and 39℃. There was an observed slight similarity (in the optimal outputs), differences (in the optimal factors) and discrepancies in results obtained from non-standardized experimental runs conducted initially when compared with the DSCD design of experiment (DOE). But then, the Statgraphic Centurion 19-X64 v. 19.6.04 software analysis gave a more reasonable findings, which fits a quadratic model at R2 = 0.9295 (predicted NO3– reduction) and 0.9068 (estimated ). Since an alkaline pH, shorter time, moderate temperature and little resources are needed to attenuate NO3– (initially at 123 mg/L) from Tandari Budum groundwater, BPS is a novel adsorbent discovered in this study, corresponding to 63.41% removal efficiency.

Water, a vital resource for ecosystems and human populations, is facing increasing nitrate contamination due to agricultural runoff, industrial discharge and improper waste disposal. The present study focuses on the efficacy of nitrate removal through adsorption using fuller’s earth (FE) and modified fuller’s earth (acid-treated) (MFE) as adsorbents. The impact of initial pH (2.0–7.0), contact time (5–240 min), adsorbent dosage (1–30 g/L), initial nitrate concentration (50–250 mg/L) and temperature (30–50°C) on nitrate removal using fuller’s earth were studied. The maximum nitrate removal was observed at pH 2.0, and equilibrium was reached in 120 min at 30℃. The Freundlich isotherm best fit the equilibrium data. The maximum nitrate uptake of fuller’s earth and modified fuller’s earth were 84.75 mg/g and 85.47 mg/g, respectively. Nitrate removal by FE and MFE followed a second-order kinetic equation. Thermodynamic studies showed spontaneity and the exothermic nature of the nitrate adsorption process. ∆H° values were −44.96 and −42.63 kJmol−1 for FE and MFE and ΔS° was −85.11 and −74.52 Jk−1mol−1 for FE and MFE, respectively. FE, known for its exceptional adsorption capacity owing to its porous structure and high ion-exchange capacity, has demonstrated a remarkable affinity for nitrate ions in batch studies.

Abstract Nitrate pollution of surface and groundwater could be a worldwide issue resulting in the threat to the environment and public health. The removal of nitrate from water was carried out using gamma aluminum oxide (γ-Al2O3) nano powder. The nano powder was synthesized from aluminum oxide powder using the aqueous-based reflux method and applied for nitrate removal. The surface properties of the activated γ-Al2O3 were characterized using FTIR, XRD, and BET surface area analysis. Analysis of variance (ANOVA) was used to analyze nitrate removal to determine the appropriate regression model, which was found to be the quadratic model with a coefficient of determination (R2 = 0.99). The adsorption process was observed to be dependent on initial nitrate concentration, adsorbent dose, and time. The optimized nitrate removal efficiencies were 97.01% using a dose of 2.26 gL−1, an initial nitrate concentration of 10 mgL−1, and a contact time of 45 min. Additionally, the kinetics of nitrate ion adsorption was discussed based on pseudo-first order and pseudo-second order kinetic models. The experimental data fitted well with the pseudo-second order kinetic model, indicating that the adsorption mechanism is chemisorption. The equilibrium adsorption of nitrate experimental data followed the both Freundlich and Langmuir isotherm (R2 = 0.95), implying a homogeneous nature of the γ-Al2O3 surface sites. These results suggest further consideration of the practical application of γ-Al2O3 for nitrate treatment for domestic purposes.

The hydrogen-based membrane biofilm reactor (H2-MBfR) is an emerging biological nitrogen removal technology characterized by high efficiency, energy-saving capability, and environmental friendliness. The technology achieves denitrification and denitrogenation of microorganisms by passing hydrogen as an electron donor from inside to outside through the hollow fibre membrane module, and eventually the hydrogen reachs the biofilm attached to the surface of the fibre membrane. H2-MBfR has obtained favourable outcomes in the treatment of secondary biochemical effluent and low concentration nitrogen polluted water source. The experiment was optimized by s single-factor testing and response surface methodology-based optimization (RSM), and the optimal operational conditions were obtained as follows: an influent flow rate of 2 mL/min, hydrogen pressure of 0.04 MPa, and influent nitrate concentration of 24.29 mg/L. Under these conditions, a high nitrate removal rate of 98.25% was achieved. In addition, Proteobacteria and Bacteroidetes were the dominant bacteria in all stages, and the genus Hydrogenophaga was sufficiently enriched, occurring at 13.0%–49.0% throughout the reactor operation. Furthermore, the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway for nitrate reduction and inorganic carbon utilization by microorganisms in the H2-MBfR was explored through comparison with the KEGG database. The results provided a mechanistic explanation for the denitrification and carbon sequestration capacity of the H2-MBfR. [ABSTRACT FROM AUTHOR]

Addressing the global challenge of water contamination, this study introduces a novel nanocomposite adsorbent—poly(ionic liquid‐modified graphene oxide) (PIL‐MGO)—designed to remove nitrates efficiently from water and combat microbial threats. Leveraging modified graphene oxide and vinyl imidazolium‐based ionic liquid, this research synthesizes an adsorbent via a facile and cost‐effective approach. The performance of PIL‐MGO was rigorously analyzed through a series of characterizations, including Frontier transform infrared spectroscopy, field emitting scanning electron microscopy, energy dispersive X‐ray spectroscopy, and thermogravimetric analysis, revealing its robust structural composition and thermal stability. In our experimental exploration, the adsorbent showcased a remarkable nitrate removal efficiency of up to 97.53%, under optimal conditions of an initial pH of 5, room temperature, initial nitrate concentration of 30 mg/L, a contact time of 30 min, and an adsorbent dosage of 40 mg, with a significant selectivity for nitrate ions over competing anions. Moreover, regeneration of the adsorbent up to 7 cycles indicated only a marginal decline in adsorption efficiency. Furthermore, PIL‐MGO demonstrated considerable antimicrobial properties against bacteria and fungi, indicating its dual utility in water purification and microbial inhibition. These findings suggest that the synthesized nanocomposite holds great promise for addressing environmental and health‐related challenges posed by water pollutants. This study not only underscores the capabilities of PIL‐MGO but also paves the way for further advancements in adsorbent technologies. Highlights: A novel nanocomposite was synthesized based on vinyl imidazolium ionic liquid and modified graphene oxide.This newly developed nanocomposite was evaluated as an adsorbent for the removal of nitrate ions from water, demonstrating high removal efficiency.The adsorbent exhibited notable selectivity for nitrate ions, effectively distinguishing them from competing anions such as chloride, bicarbonate, sulfate, and phosphate.The adsorption kinetics of the nanocomposite were best described by the pseudo‐second‐order kinetic model, and the adsorption isotherm aligned well with the Langmuir model.Investigation of the nanocomposite antimicrobial activity displayed considerable inhibitory effects against both bacteria and fungi. [ABSTRACT FROM AUTHOR]

To provide the necessary nitrite for the Anaerobic Ammonium Oxidation (ANAMMOX) process, the effect of nitrite accumulation in the partial sulfide autotrophic denitrification (PSAD) process was investigated using an SBR reactor. The results revealed that the effectiveness of nitrate removal was unsatisfactory when the S/N ratio (mol/mol) fell below 0.6. The optimal conditions for nitrate removal and nitrite accumulation were achieved within the S/N ratio range of 0.7-0.8, resulting in an average Nitrate Removal Efficiency (NRE) of 95.84%±4.89% and a Nitrite Accumulation Rate (NAR) of 75.31%±6.61%, respectively. It was observed that the nitrate reduction rate was three times faster than that of nitrite reduction during a typical cycle test. Furthermore, batch tests were conducted to assess the influence of pH and temperature conditions. In the pH tests, it became evident that the PSAD process performed more effectively in alkaline environment. The highest levels of nitrate removal and nitrite accumulation were achieved at an initial pH of 8.5, resulting in a NRE of 98.30%±1.93% and a NAR of 85.83%±0.47%, respectively. In the temperature tests, the most favourable outcomes for nitrate removal and nitrite accumulation were observed at 22±1 ℃, with a NRE of 100.00% and a NAR of 81.03%±1.64%, respectively. Moreover, a comparative analysis of 16S rRNA sequencing results between the raw sludge and the sulfide-enriched culture sludge sample showed that Proteobacteria (49.51%) remained the dominant phylum, with Thiobacillus (24.72%), Prosthecobacter (2.55%), Brevundimonas (2.31%) and Ignavibacterium (2.04%) emerging as the dominant genera, assuming the good nitrogen performance of the system. [ABSTRACT FROM AUTHOR]

Inefficiently treated wastewater, which contains a high concentration of pollutants, is hazardous when it is mixed with the clean water of rivers and lakes. Nitrate in particular is a major global problem that leads to eutrophication and poses a threat to both aquatic ecosystems and human health. To address this issue, this work assessed the efficiency of polymeric cryogel (PC) and biopolymer (EPS)-blended composites (EPS@PC) in removing nitrates. Tests were also conducted to quantify the decrease in phosphate, chloride ions, and chemical oxygen demand (COD) in real water samples taken from the Ankara stream, which receives effluents from both urban (UWTP) and industrial (IWTP) wastewater treatment plants. Five different columns with varying adsorptive properties were prepared, some of which were combined with iron. The EPS-@PC-C5 column demonstrated the highest adsorption ratio for nitrate removal compared to the other tested columns. The EPS@PC-C5 achieved a high removal efficiency of 126.38 mg nitrate/g and showed COD reduction ranging from 60.2 to 94.1%. The removal ratio of chloride concentration varied between 56.0 and 75.7%, while the removal of phosphates ranged from 87 to 99%. Columns composed of EPS (EPS@PC) with both negatively and positively charged ligands are dependable and suitable options for water remediation. [ABSTRACT FROM AUTHOR]

A nitrate selective electrode was used for real-time in situ potentiometric monitoring of a batch nitrate removal process using activated carbon and ion exchange resin. A plasticized polymeric membrane consisting of polyvinyl chloride, 2-nitrophenyl octyl ether and tridodecyl methyl ammonium chloride was incorporated into an ion-selective electrode body. First, the dynamic potential response of the electrode to nitrate was investigated. Two commercial activated carbons with different physical properties were then tested. Nitrate removal with these carbons was monitored potentiometrically using several nitrate concentrations. The extreme turbidity of the solutions was not a drawback during potentiometric monitoring of the process, which is a clear advantage over other methods such as optical monitoring. The potential versus time recordings were converted into nitrate concentration versus time plots, which were evaluated with different adsorption kinetic models. A pseudo-second order kinetic model for nitrate adsorption on both activated carbons was found to fit the experimental data very well. The values of the kinetic parameters were very different between the two activated carbons. The proposed methodology was also satisfactorily applied to the study of nitrate removal by an ion exchange resin. In this case, the experimental results clearly follow a pseudo-first order kinetic model. Potential applications of the proposed methodology for monitoring nitrate removal in real water samples are discussed. [ABSTRACT FROM AUTHOR]

Nitrate pollution of surface and groundwater could be a worldwide issue resulting in the threat to the environment and public health. The removal of nitrate from water was carried out using gamma aluminum oxide (γ-Al2O3) nano powder. The nano powder was synthesized from aluminum oxide powder using the aqueous-based reflux method and applied for nitrate removal. The surface properties of the activated γ-Al2O3 were characterized using FTIR, XRD, and BET surface area analysis. Analysis of variance (ANOVA) was used to analyze nitrate removal to determine the appropriate regression model, which was found to be the quadratic model with a coefficient of determination (R2 = 0.99). The adsorption process was observed to be dependent on initial nitrate concentration, adsorbent dose, and time. The optimized nitrate removal efficiencies were 97.01% using a dose of 2.26 gL−1, an initial nitrate concentration of 10 mgL−1, and a contact time of 45 min. Additionally, the kinetics of nitrate ion adsorption was discussed based on pseudo-first order and pseudo-second order kinetic models. The experimental data fitted well with the pseudo-second order kinetic model, indicating that the adsorption mechanism is chemisorption. The equilibrium adsorption of nitrate experimental data followed the both Freundlich and Langmuir isotherm (R2 = 0.95), implying a homogeneous nature of the γ-Al2O3 surface sites. These results suggest further consideration of the practical application of γ-Al2O3 for nitrate treatment for domestic purposes. [ABSTRACT FROM AUTHOR]

Nitrate, a major groundwater pollutant from anthropogenic activities, poses serious health risks when present in drinking water. Denitrification using bio-electrochemical reactors (BER) offers an innovative technology, eco-friendly solution for nitrate removal from groundwater. BER use electroactive bacteria to reduce inorganic compounds like nitrate and bicarbonate by transferring electrons directly from the cathode. In our work, two batch BER were implemented at 1V and 2V, using anaerobic digestate from a full-scale wastewater treatment plant as inoculum. Nitrate, nitrite, sulfate, total ammoniacal nitrogen, and 16S rRNA analysis of bacterial community, were monitored during BER operation. The results showed effective nitrate removal in all BERs, with denitrification rate at 1V and 2V higher than the Control system, where endogenous respiration drove the process. At 1V, complete nitrate conversion to N2 occurred in 4 days, while at 2V, it took 14 days. The slower rate at 2V was likely due to O2 production from water electrolysis, which competed with nitrate as final electron acceptor. Bacterial community analysis confirmed the electroactive bacteria selection like the genus Desulfosporosinus and Leptolinea, confirming electrons transfer without an electroactive biofilm. Besides, Hydrogenophaga was enhanced at 2V likely due to electrolytically produced H2. Sulfate was not reduced, and total ammoniacal nitrogen remained constant indicating no dissimilatory nitrite reduction of ammonia. These results provide a significant contribution to the scaling up of electro-assisted autotrophic denitrification and its application in groundwater remediation, utilizing a simple reactor configuration-a single-chamber, membrane-free design- and a conventional power source instead of a potentiostat.

The nitrate contamination of water resources is a serious environmental problem, which may be solved by nitrate sorption onto magnetic nanoparticles. In this study, the effects of Fe3O4 magnetic nanoparticles on nitrate removal were investigated. Fe3O4 was synthesized by a co-precipitation method and used as an adsorbent for nitrate removal. pH, adsorbent dosage, and contact time were considered as the main variables. The effective ranges of these variables were chosen as pH = 4–10, adsorbent dose = 0.5–1.5 g/L, and contact time = 30–90 min. The optimization study was conducted using the Box–Behnken statistical design method. According to the analysis of variance table, it can be concluded that the model is ‘significant’ and the value of R2 was 0.99. The results of the study show that the maximum nitrate removal efficiency was about 91.02%. This was obtained at pH 7, using a dose of 1.3 g/Lof Fe3O4, and a contact time of 28 min. HIGHLIGHTS It is a nitrate removal study.; It is an optimization study.; It includes nanoparticles.;

Nitrate pollution of water emerging from various anthropogenic activities has become a major environmental concern because of its deleterious effects on natural water resources. The present work deals with the synthesis of the ternary nanocomposite based on chitosan, iron oxide (Fe3O4), and titanium dioxide (TiO2) and its application for the removal of nitrates from model-contaminated water. Fe3O4 derived through a coprecipitation method was incorporated into the chitosan matrix which was fabricated in the form of beads. The wet gel beads were then successfully coated with sol–gel-derived silver-doped titanium dioxide sol followed by drying under suitable conditions to get the functional nanocomposite beads. The synthesized functional materials were further characterized for their structural, morphological, and textural features using X-ray diffraction analysis, physical property measurement (PPMS), Fourier transform infrared (FTIR) analysis, UV visible spectroscopy analysis (UV–vis), BET surface area analysis (BET), field emission scanning electron microscopic (FESEM), and transmission electron microscopy (TEM) analysis. The ternary nanocomposites were further used for the removal of nitrates via adsorption cum photocatalytic reduction technique from the model contaminated water when subjected to an adsorption study under dark conditions and photocatalytic study under UV/visible/sunlight for a definite time. Fe3O4 in the nanocomposite provides enhanced adsorption features whereas the functional coating of titanium dioxide aids in the removal of nitrates through the photocatalytic reduction technique. The functional beads containing 3% Fe3O4 in the wet gel form (CTA-F3) have excellent nitrate removal efficiency of ~ 97% via adsorption cum solar photocatalysis towards the removal of nitrate ions from 50 ppm nitrate solution, whereas the dried nanocomposite beads have got a nitrate removal efficiency of ~ 68% in 1 h from 100 ppm nitrate solution. Continuous flow adsorption cum photocatalytic study was performed further using the oven-dried functional beads in which flow rate and bed height were varied while maintaining the concentration of feed solution as constant. A nitrate removal efficiency of 65% and an adsorption capacity of 4.1 mgg−1 were obtained for the CTA-F3 beads in the continuous flow adsorption cum photocatalysis experiment for up to 5 h when using an inlet concentration of 100 ppm, bed height 12 cm, and flow rate 5.0 ml min−1. A representative fixed-bed column adsorption experiment conducted using CTA-F3 beads for the treatment of a real groundwater sample shows reasonable results for nitrate removal (71.7% efficiency) along with a significant removal rate for the other anions as well. Thus, the novel adsorbent/photocatalyst developed is suitable for the removal of nitrates from water due to the synergistic effect between Fe3O4, chitosan, and titanium dioxide. [ABSTRACT FROM AUTHOR]

The removal of nitrogen from wastewater is one of the challenges faced by environmental engineers globally. Autotrophic denitrification is a promising method for treating nitrate (NO3−) -contaminated wastewater because of its relatively low requirement for carbon and lesser sludge yield. Therefore, this study was aimed at investigating the autotrophic denitrification efficiency of two different dual-chamber configurations of microbial fuel cells (MFCs) in order to provide a foundation for building scalable, efficient, and sustainable denitrification systems. Analysis revealed that the maximum current density and power density were 4,327 mA/m3 and 1,441 mW/m3, respectively, in a cube-shaped dual-chamber MFC (C-MFC), whereas these values were 1,452 mA/m3 and 370 mW/m3, respectively, in an H-shaped dual-chamber configuration (H-MFC). In addition, the C-MFC and H-MFC achieved relatively high NO3− reduction rates of up to 28 and 15.6 g/m3/day, respectively. The cathodic coulombic efficiency was observed to be 57% in the C-MFC and 30% in the H-MFC. The average chemical oxygen demand removal efficiency was about 98% for both MFC configurations. High-throughput sequencing analysis revealed significant changes in the microbial community structure under different reactor configurations. The relative abundance of Proteobacteria (34.67%) and Firmicutes (18.59%) at the phylum level were higher in the C-MFC than the H-MFC, signifying that higher current generation can enhance the proliferation and microbial activity of autotrophic denitrifiers. [ABSTRACT FROM AUTHOR]

This study synthesized a nanocomposite based on quaternary branched polyethyleneimine containing sodium alginate and graphene oxide and characterized by FE‐SEM, EDX‐MAP, XRD, FT‐IR, and TGA and used as an efficient sorbent for the removal of nitrate ions. The maximum ion exchange in optimized conditions was discovered to be 75%. The experimental studies showed that nitrate removal follows the pseudo‐first‐order model due to more consonance. Also, Weber–Morris and Boyd models suggested that the nitrate ions adsorption on the surface of nanocomposite is not controlled only by the intraparticle diffusion step. Moreover, Langmuir, Redlich–Peterson, and Hill models exhibited high regression coefficients of 0.991, 0.993, and 0.992, respectively. Thermodynamic studies confirmed the adsorption system was spontaneous and exothermic. Recovery assay showed that more than 98% of the nitrate ion exchanged by the nanocomposite was regenerated and nanocomposite could be reused seven cycles without efficacy reducing significantly. The nanocomposite showed excellent antibacterial activity against Staphylococcus aureus and Escherichia coli cells, with minimum inhibitory concentrations of 62.5 and 125 μg mL−1, and zone of growth inhibition of 17.5 ± 0.5 and 10.5 ± 0.5 mm, respectively. The results represented that the introduced nanocomposite is a useful material for the removal of nitrate ions from aqueous solution and has antibacterial properties. [ABSTRACT FROM AUTHOR]

Membrane biofilm reactors (MBfRs) have attracted more and more attention in the field of wastewater treatment due to their advantages of high mass transfer efficiency and low-carbon emissions. There are many factors affecting their nitrogen removal abilities, such as operation time, electron donor types, and operation modes. The operation time is directly related to the growth status of microorganisms, so it is very important to understand the effect of different operation times on microbial composition and community succession. In this study, two parallel H2-based MBfRs were operated, and differences in microbial composition, community succession, and NO3--N removal efficiency were investigated on the 30th day and the 60th day of operation. The nitrogen removal efficiency of MBfRs with an operation time of 60 days was higher than that of MBfRs with an operation time of 30 days. Proteobacteria was the dominant phylum in both MBfRs; however, the composition of the microbial community was quite different. At the class level, the community composition of Proteobacteria was similar between the two MBfRs. Alphaproteobacteria was the dominant class in MBfR, and Betaproteobacteria and Gammaproteobacteria were also in high proportion. Combined with the analysis of microbial relative abundance and concentration, the similarity of microbial distribution in the MBfRs was very low on day 30 and day 60, and the phylogenetic relationships of the top 50 dominant universal bacteria and Proteobacteria were different. Although the microbial concentration decreased with the extension of the operation time, the microbial abundance and diversity of specific functional microorganisms increased further. Therefore, the operation time had a significant effect on microbial composition and community succession.

In this study, biohydrogen was produced by R. johrii strain VT1 using an anaerobic photo-fermentation process on low-cost industrial wastewater and then used for nitrate reduction in the presence of a chemical catalyst. The effect of substrate, light intensity, and pH on biohydrogen production was investigated. For efficient nitrate reduction, a Pd–Cu/alumina bimetallic catalyst was prepared and analyzed by XRD, FTIR, FESEM, and ICP. Accumulative biohydrogen production was 284.67 ml/h (0.409 ± 0.005 mol/m3h), with molasses, a light intensity of 5300 lux, and a pH of 9. Nitrate removal efficiency was 81.70%, and nitrogen selectivity was 94.25%. The XRD results also showed the stability of the catalyst structure during the reduction. Our study shows that this combined method is effective for nitrate removal and has the potential for large-scale work because of the affordable and sustainable green hydrogen production from wastewater. This is the first report of using biological hydrogen for harmful nitrate removal from drinking water in the presence of a chemical catalyst. [Display omitted] • R,johrii, produced biohydrogen with industrial wastes, as available and affordable substrate, efficiently. • This is the first report of the use of biohydrogen for nitrate reduction through chemical catalysts. • Pd–Cu//γ-Al 2 O 3 , used as an efficient and selective catalyst for nitrate removal from waters. [ABSTRACT FROM AUTHOR]

In this study, a constructed wetland–Fe3O4/granular activated carbon anode microbial electrolysis cell (CW-FMEC) was constructed to enhance denitrification in low COD/N ratio wastewater. The introduction of Fe3O4 boosted the expression of functional genes involved in the denitrification pathway, and the abundance of narG, nirS, and nosZ increased by 99.29%, 70.54%, and 132.18%, respectively, compared to CW. In addition, the content of c-type cytochromes (c-Cyts) and EPS were also enhanced in the CW-FMEC. The microbial communities study displayed that Thauera, Dechloromonas, and Arenimonas became the main genera for denitrification. The denitrification performance at different COD/N ratios was investigated in depth. Under optimal working circumstances, the CW-FMEC had an excellent nitrate removal rate (88.9% ± 1.12%) while accumulating nearly no NO2−-N or NH4+-N in the effluent. This study provides a new direction for the development of CW-MEC and accelerates its implementation. [ABSTRACT FROM AUTHOR]

The primary objective of the present study is to enhance the denitrification process in constructed wetlands (CWs), employed as an ecological and natural technology for wastewater treatment. Eco-friendly approaches have been tested to improve the nitrate removal efficiency in pilot-scale subsurface flow CWs. Initially, the system's performance was enhanced by using a natural substrate, namely cork, as a filter medium. Another approach is bio-inoculation into the rhizosphere of a bacterial strain with the potential capacity for nitrate removal, thereby reinforcing the synergy between the plant and microorganisms. Finally, the approaches were combined, and nitrate removal was assessed. The main results showed that the most effective nitrate removal from wastewater was achieved with cork (80%) compared to gravel (60%). Bio-inoculation into the rhizosphere of denitrifying bacteria significantly improved nitrate removal. Indeed, the nitrate removal rate by the inoculated CW filled with gravel, was higher than the non-inoculated system, with rates of 78% and 60%, respectively. Moreover, the highest removal rate of 99.77% was obtained with the inoculated system filled with cork. [ABSTRACT FROM AUTHOR]

Wastewater treatment with microalgae and its reuse is an effective step toward reducing water consumption and preserving water resources. The possibility of growing spirulina microalga on cattle effluents and the possibility of purifying effluents using microalga were investigated. Different concentrations of standard culture medium (Zaruk)-wastewater were used to measure the optimal algal growth on wastewater and to determine the concentration of effluent-Zaruk for optimal algal growth. The treatments were T1 including 100% Zaruk and no wastewater, T2 including 75% Zaruk and 25% wastewater, T3 including 50% Zaruk and 50% wastewater, T4 including 25% Zaruk and 75% effluent and T5 including 100% effluent without Zaruk. Treatments that had more Zaruk, showed more optimal growth, and those that had a higher concentration of effluent often showed a relatively lower growth of algae biomass. The results showed the high growth of algae on the concentrated effluent. T1 with 0.35 and T2 with 0.3 g/liter of dry biomass had the highest biomass of microalgae. T1, T2, T4, T3, and T5 had the highest to the lowest amount of phycocyanin pigment production in microalgae, respectively. The highest removal of nitrate belonged to T5 and T4 with 82.57% and 78.21% removal respectively, and the lowest nitrate removal belonged to T1 and T2 with 57.17% and 70.94%, respectively. The highest removal of phosphate belonged to T1 and T2 with 94% and 92.11% removal, respectively. The lowest removal of phosphate belonged to T4 with 84% removal. Findings indicated the high potential of microalga for treating cattle wastewater. [ABSTRACT FROM AUTHOR]

The risk of nitrate contamination became a reality for Fairmont in Minnesota, when water rich in NO3-N exceeded the drinking water standard of 10 mg/L. This was unexpected because this city draws its municipal water from a chain of lakes that are fed primarily by shallow groundwater under row-crop land use. Spring soil thaw drives cold water into a subsurface pipe where almost no NO3-N reduction occurs. This paper focuses on NO3-N reduction before the water enters the lakes and no other nitrogen management practices in the watershed. A novel denitrifying bioreactor was constructed behind a sediment forebay, which then flowed into a chamber covered by a greenhouse before entering a woodchip bioreactor. In 2022 and 2023, water depth, dissolved oxygen, and temperature were measured at several locations in the bioreactor, and continuous NO3-N was measured at the entry and exit of the bioreactor. The results showed better performance at a low water depth with lower dissolved oxygen and higher water temperature. The greenhouse raised the inlet temperature in 2022 but did not in 2023. The forebay and the greenhouse may have impeded the denitrification process due to the high dissolved oxygen concentrations in the influent and the stratification of dissolved oxygen caused by algae in the bioreactor. [ABSTRACT FROM AUTHOR]

Owing to rapid industrial and agricultural development, nitrate (NO3−-N) in the aquatic environment has been increasing constantly, which poses a serious threat to human health. The NO3−-N can be reduced by aerobic denitrifying bacteria to gaseous nitrogen under aerobic conditions. In this study, three mixed aerobic denitrifying bacteria (NH, XF, and WU) were screened from various lake sediments. The NO3−-N removal efficiencies reached over 97% at 36 h incubation in the medium and 72.89%, 67.33%, and 80.22% at 55 h incubation in eutrophic lake water. Nitrogen balance results showed that aerobic denitrifying bacteria transformed 41.22%, 24.56%, and 47.99% of the total nitrogen into gaseous nitrogen, respectively. High-throughput sequencing results showed the dominant bacteria were Proteobacteria and Pseudomonas. The relative abundance of functional genes for denitrification was predicted utilizing PICRUSt2, which was consistent with the trend of the quantitative microbial element cycling results. This study will provide a novel approach for applying microbial remediation in aqueous environment. [ABSTRACT FROM AUTHOR]

Bioelectrochemical systems are sustainable and potential technology systems in wastewater treatment for nitrogen removal. The present study fabricated an air-cathode denitrifying microbial fuel cell (DNMFC) with a revisable modular design and investigated metabolic processes using nutrients together with the spatiotemporal distribution characteristics of dominated microorganisms. Based on the detection of organics and solvable nitrogen concentrations as well as electron generations in DNMFCs under different conditions, the distribution pattern of nutrients could be quantified. By calculation, it was found that heterotrophic denitrification performed in DNMFCs using 56.6% COD decreased the Coulombic efficiency from 38.0% to 16.5% at a COD/NO3−-N ratio of 7. Furthermore, biological denitrification removed 92.3% of the nitrate, while the residual was reduced via electrochemical denitrification in the cathode. Correspondingly, nitrate as the electron acceptor consumed 16.7% of all the generated electrons, and the residual electrons were accepted by oxygen. Microbial community analysis revealed that bifunctional bacteria of electroactive denitrifying bacteria distributed all over the reactor determined the DNMFC performance; meanwhile, electroactive bacteria were mainly distributed in the anode biofilm, anaerobic denitrifying bacteria adhered to the wall, and facultative anaerobic denitrifying bacteria were distributed in the wall and cathode. Characterizing the contribution of specific microorganisms in DNMFCs comprehensively revealed the significant role of electroactive denitrifying bacteria and their cooperative relationship with other functional bacteria.