scholarly journals Preparation of Co/Ti electrode by electro-deposition for aqueous nitrate reduction

2021 ◽  
Author(s):  
Bicun Jiang ◽  
Liqin Han ◽  
Juntian Wang ◽  
Chang Lu ◽  
Yang Pan ◽  
...  
Keyword(s):  
Nitrate Reduction ◽  
Nitrate Removal ◽  
Ammonium Nitrogen ◽  
Nitrite Reduction ◽  
Electrolysis Cell ◽  
Ammonium Oxidation ◽  
Nitrogen Gas ◽  
Electro Deposition ◽  
Improved Stability ◽  
Chlorine Ion

Abstract A Co/Ti electrode for nitrate reduction was prepared by electrode-deposition. In the single-compartment electrolysis cell, nitrate (100 mg/L) removal reached nearly 100% after 3 h electrolysis under the current density of 20 mA cm–2 by using the Co/Ti electrode as cathode, and the main reduction products were ammonium nitrogen (66.5%) and nitrogen gas (33.5%). This performance on nitrate removal was comparable to a Co3O4/Ti electrode, and the electroactivity of the Co/Ti electrode towards nitrite reduction was higher than that of a Co3O4/Ti electrode. The Co/Ti electrode exhibited an improved stability with 18.7% of mass loss and 25.5% of Co dissolution compared with the Co3O4/Ti electrode after ultrasonic interference. The presence of chlorine ion (1,000 mg/L) could promote the total nitrogen (TN) removal to approximately 100% after 3 h electrolysis because of the ammonium oxidation by the free chlorine produced from the anode. In the presence of calcium (50 mg/L) and phosphate (0.5 mg/L), the nitrate removal decreased from 85.4 ± 1.5 to 57.7 ± 3.5% after ten reuse cycles. This result suggests that Ca and P should be pre-removed before the electro-reduction of nitrate.

scholarly journals Biogenic Fe(II-III) Hydroxycarbonate Green Rust Enhances Nitrate Removal and Decreases Ammonium Selectivity during Heterotrophic Denitrification

Minerals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 818
Author(s):  
Georges Ona-Nguema ◽  
Delphine Guerbois ◽  
Céline Pallud ◽  
Jessica Brest ◽  
Mustapha Abdelmoula ◽  
...  
Keyword(s):  
Nitrate Reduction ◽  
Nitrate Removal ◽  
Green Rust ◽  
Nitrite Reduction ◽  
Nitrite Accumulation ◽  
Bacterial Reduction ◽  
Water Treatment Process ◽  
Nitrite Production ◽  
Ammonium Production ◽  
Biogenic Iron

Nitrification-denitrification is the most widely used nitrogen removal process in wastewater treatment. However, this process can lead to undesirable nitrite accumulation and subsequent ammonium production. Biogenic Fe(II-III) hydroxycarbonate green rust has recently emerged as a candidate to reduce nitrite without ammonium production under abiotic conditions. The present study investigated whether biogenic iron(II-III) hydroxycarbonate green rust could also reduce nitrite to gaseous nitrogen during bacterial nitrate reduction. Our results showed that biogenic iron(II-III) hydroxycarbonate green rust could efficiently decrease the selectivity of the reaction towards ammonium during heterotrophic nitrate reduction by native wastewater-denitrifying bacteria and by three different species of Shewanella: S. putrefaciens ATCC 12099, S. putrefaciens ATCC 8071 and S. oneidensis MR-1. Indeed, in the absence of biogenic hydroxycarbonate green rust, bacterial reduction of nitrate converted 11–42% of the initial nitrate into ammonium, but this value dropped to 1–28% in the presence of biogenic hydroxycarbonate green rust. Additionally, nitrite accumulation did not exceed the 2–13% in the presence of biogenic hydroxycarbonate green rust, versus 0–28% in its absence. Based on those results that enhance the extent of denitrification of about 60%, the study proposes a water treatment process that couples the bacterial nitrite production with the abiotic nitrite reduction by biogenic green rust.

scholarly journals Glycerol-driven Denitratation: Process Kinetics, Microbial Ecology, and Operational Controls

2021 ◽  
Author(s):  
Matthew P. Baideme ◽  
Chenghua Long ◽  
Luke T. Plante ◽  
Jeffrey A. Starke ◽  
Michael A. Butkus ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Microbial Ecology ◽  
Nitrate Reduction ◽  
Carbon Sources ◽  
Selective Reduction ◽  
Nitrite Reduction ◽  
Nitrite Accumulation ◽  
Ammonium Oxidation ◽  
Order Of Magnitude ◽  
Nitrate And Nitrite

ABSTRACTDenitratation, the selective reduction of nitrate to nitrite, is a novel process when coupled with anaerobic ammonium oxidation (anammox) could achieve resource-efficient biological nitrogen removal of ammonium- and nitrate-laden waste streams. Using a fundamentally-based, first principles approach, this study optimized a stoichiometrically-limited, glycerol-driven denitratation process and characterized mechanisms supporting nitrite accumulation with results that aligned with expectations. Glycerol supported selective nitrate reduction to nitrite and near-complete nitrate conversion, indicating its viability in a denitratation system. Glycerol-supported specific rates of nitrate reduction (135.3 mg-N/g-VSS/h) were at least one order of magnitude greater than specific rates of nitrite reduction (14.9 mg-N/g-VSS/h), potentially resulting in transient nitrite accumulation and indicating glycerol’s superiority over other organic carbon sources in denitratation systems. pH and ORP inflection points in nitrogen transformation assays corresponded to maximum nitrite accumulation, indicating operational setpoints to prevent further nitrite reduction. Denitratation conditions supported enrichment of Thauera sp. as the dominant genus. Stoichiometric limitation of influent organic carbon, coupled with differential nitrate and nitrite reduction kinetics, optimized operational controls, and a distinctively enriched microbial ecology, was identified as causal in glycerol-driven denitratation.

Enhanced removal of nitrate from water using nZVI@MWCNTs composite: synthesis, kinetics and mechanism of reduction

2015 ◽  
Vol 72 (11) ◽  
pp. 1988-1999 ◽  
Author(s):  
Ali Akbar Babaei ◽  
Ali Azari ◽  
Roshanak Rezaei Kalantary ◽  
Babak Kakavandi
Keyword(s):  
Nitrate Reduction ◽  
Nitrate Removal ◽  
Nitrogen Gas ◽  
Initial Concentration ◽  
Multi Wall Carbon Nanotubes ◽  
Batch System ◽  
Low Concentrations ◽  
End Products ◽  
Nano Zero Valent Iron ◽  
Influential Parameters

Herein, multi-wall carbon nanotubes (MWCNTs) were used as the carrier of nano-zero valent iron (nZVI) particles to fabricate a composite known as nZVI@MWCNTs. The composite was then characterized and applied in the nitrate removal process in a batch system under anoxic conditions. The influential parameters such as pH, various concentrations of nitrate and composite were investigated within 240 min of the reaction. The mechanism, kinetics and end-products of nitrate reduction were also evaluated. Results revealed that the removal nitrate percentage for nZVI@MWCNTs composite was higher than that of nZVI and MWCNTs alone. Experimental data from nitrate reduction were fitted to the Langmuir–Hinshelwood kinetic model. The values of observed rate constant (kobs) decreased with increasing the initial concentration of nitrate. Our experiments proved that the nitrate removal efficiency was favorable once both high amounts of nZVI@MWCNTs and low concentrations of nitrate were applied. The predominant end-products of the nitrate reduction were ammonium (84%) and nitrogen gas (15%). Our findings also revealed that ZVI@MWCNTs is potentially a good composite for removal/reduction of nitrate from aqueous solutions.

Structural Changes of Bimetallic PdX/Cu (1-X) Nanocatalysts Developed for Nitrate Reduction of Drinking Water

2005 ◽  
Vol 876 ◽  
Author(s):  
Huiping Xu ◽  
Ray Twesten ◽  
Kathryn Guy ◽  
John Shapley ◽  
Charles Werth ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Drinking Water ◽  
Catalytic Activity ◽  
Nitrate Reduction ◽  
Structural Changes ◽  
Nitrate Removal ◽  
High Resolution Electron Microscopy ◽  
Nitrite Reduction ◽  
Contrast Imaging ◽  
Promising Alternative

AbstractReductive removal by hydrogeneration using supported Pd/M (M= Cu, Pt, Ag, Co, Fe, Mo, Ni, Rh, Ir, Mn and Cr) bimetallic catalysts has emerged as a promising alternative for nitrate removal in drinking water [1]. Fundamental understanding how the atomic arrangement of Pd and a second element, such as Cu, affect the activity nitrite reduction and selectivity of dinitrogen will be accomplished by coordinated synthesis (Shapley), activity/selectivity/efficiency measurements (Werth) and nanostructure determination (Yang & Xu). In this paper, we report a systematic study of novel polyvinylpyrrolidone (PVP) stabilized nanoscale Pd-Cu colloids, with homogeneous and narrow size distribution, with Pd: Cu ratios varying from 50:50 to 90:10. Initial measurements on catalytic activity for nitrate reduction demonstrated a dependence on the relative composition. Electron microscopy studies, including Z-contrast imaging [2], energy-dispersive X-ray emission (EDX), electron diffraction and high-resolution electron microscopy (HREM), revealed a surprising change in structure at the 80:20 Pd-Cu composition, where, with less than 80% Pd,the nanoparticle forms a core-shell structure but for nanoparticles containing 80% or more Pd, it is homogeneous. We are at the pivotal point of directly correlating these nano-structures with the catalytic activity. Such an understanding is essential for the efficient development of catalysts for the purification of drinking water.

The Simultaneous Removal of Carbon and Nitrogen from the Anaerobically Pretreated Distillery Wastewater in an Anaerobic Expanded Granule Sludge Bed (EGSB) Reactor

2011 ◽  
Vol 90-93 ◽  
pp. 2939-2943 ◽  
Author(s):  
Jun Li ◽  
Zhi Yu Zhang ◽  
Qiang Liu ◽  
Qing Yuan Yang
Keyword(s):  
Nitrate Reduction ◽  
Nitrogen Loading ◽  
Nitrite Reduction ◽  
Simultaneous Removal ◽  
Nitrate Accumulation ◽  
Nitrogen Gas ◽  
Carbon And Nitrogen ◽  
Distillery Wastewater ◽  
Ammonia Addition ◽  
Kjeldahl Nitrogen

The simultaneous removal of carbon and nitrogen of the anaerobically pretreated distillery wastewater with nitrate, nitrite and ammonia addition was investigated in an expanded granule sludge bed (EGSB) reactor inoculated with methanogenic granule sludge. The experiment showed the COD removal efficiency decreased with the nitrogen loading increasing. Moreover, denitrifiers out-compete methanogens for the utilization of organics gradually, and COD removed by methanogenesis decreased to only 20% by measuring the amount of CH4 produced at low C/N ratios of 2, 3 and 4. Nitrate reduction to ammonium didn’t occur whatever the C/N ratio under anaerobic conditions. At high C/N ratios of 10 and 8, little total Kjeldahl nitrogen (TKN) was removed. However, 30%-50% of TKN entering the reactor was removed at lower C/N ratios of 2, 3 and 4 suggesting the removal of ammonium. At a lower C/N ratio of 2, the nitrite and the nitrate accumulation were observed and TKN removal decreased gradually due to their inhibition. The result suggested that the nitrate and ammonium simultaneous removal occurred through a coupling of nitrate reduction to nitrite by denitrification and then nitrite reduction to nitrogen gas by both denitrification and Anammox at a proper C/N ratio in an anaerobic EGSB reactor.

scholarly journals Oxygen and light determine the pathways of nitrate reduction in a highly saline lake

2020 ◽  
Author(s):  
Nicolás Valiente ◽  
Franz Jirsa ◽  
Thomas Hein ◽  
Wolfgang Wanek ◽  
Patricia Bonin ◽  
...  
Keyword(s):  
Nitrate Reduction ◽  
Environmental Gradients ◽  
Nitrate Removal ◽  
Hypersaline Lake ◽  
N2o Emissions ◽  
Ammonium Oxidation ◽  
Lake Ecosystems ◽  
N Removal ◽  
Mesocosm Experiments

Abstract. Nitrate (NO3−) removal from aquatic ecosystems involves several microbially mediated processes including denitrification, dissimilatory nitrate reduction to ammonium (DNRA), and anaerobic ammonium oxidation (anammox) regulated by slight changes in environmental gradients. Saline lakes are prone to the accumulation of anthropogenic contaminants, making them highly vulnerable environments to NO3− pollution. We investigated nitrate removal pathways in mesocosm experiments using lacustrine, undisturbed, organic-rich sediments from Pétrola Lake (Spain), a highly saline waterbody subject to anthropogenic NO3− pollution. We used the revised 15N-isotope pairing technique (15N-IPT) to determine NO3− sink processes. Our results demonstrate the coexistence of denitrification, DNRA, and anammox processes, and their contribution was determined by environmental conditions (oxygen and light). DNRA and N2O-denitrification were the dominant nitrogen (N) removal pathways when oxygen and/or light were present (up to 82 %). In contrast, anoxia and darkness promoted NO3− reduction by DNRA (52 %) and N loss by anammox (28 %). Our results highlight the role of coupled DNRA-anammox, as yet has never been investigated in hypersaline lake ecosystems. We conclude that anoxia and darkness favored DNRA and anammox processes over denitrification and therefore reduce N2O emissions to the atmosphere.

Optimal operations for groundwater denitrification of drinking water using heterotrophic biological denitrification process

2006 ◽  
Vol 6 (2) ◽  
pp. 125-130
Author(s):  
C.-H. Hung ◽  
K.-H. Tsai ◽  
Y.-K. Su ◽  
C.-M. Liang ◽  
M.-H. Su ◽  
...  
Keyword(s):  
Drinking Water ◽  
Removal Efficiency ◽  
Nitrate Removal ◽  
Drinking Water Treatment ◽  
Nitrate Content ◽  
Source Water ◽  
Nitrogen Gas ◽  
Negative Effect ◽  
Denitrification Process ◽  
Heterotrophic Denitrification

Due to the extensive application of artificial nitrogen-based fertilizers on land, groundwater from the central part of Taiwan faces problems of increasing concentrations of nitrate, which were measured to be well above 30 mg/L all year round. For meeting the 10 mg/L nitrate standard, optimal operations for a heterotrophic denitrification pilot plant designed for drinking water treatment was investigated. Ethanol and phosphate were added for bacteria growing on anthracite to convert nitrate to nitrogen gas. Results showed that presence of high dissolved oxygen (around 4 mg/L) in the source water did not have a significantly negative effect on nitrogen removal. When operated under a C/N ratio of 1.88, which was recommended in the literature, nitrate removal efficiency was measured to be around 70%, sometimes up to 90%. However, the reactor often underwent severe clogging problems. When operated under C/N ratio of 1.0, denitrification efficiency decreased significantly to 30%. Finally, when operated under C/N ratio of 1.5, the nitrate content of the influent was almost completely reduced at the first one-third part of the bioreactor with an overall removal efficiency of 89–91%. Another advantage for operating with a C/N ratio of 1.5 is that only one-third of the biosolids was produced compared to a C/N value of 1.88.

scholarly journals Effects of cobalt-histidine absorbent on aerobic denitrification by Paracoccus versutus LYM

AMB Express ◽  
2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Chaoyue Sun ◽  
Yu Zhang ◽  
Zhenping Qu ◽  
Jiti Zhou
Keyword(s):  
Nitrate Reduction ◽  
Nitrite Reduction ◽  
Aerobic Denitrification ◽  
Chemical Absorption ◽  
Binding Ability ◽  
Biological Reduction ◽  
Distinct Effect ◽  
The Future

AbstractTo overcome the problem that ferrous complexes are easily oxidized by O2 and then lose NO binding ability in the chemical absorption-biological reduction (CABR) process, cobalt(II)-histidine [Co(II)His] was proposed as an alternative. To evaluate the applicability of Co(II)His, the effects of CoHis absorbent on the aerobic denitrification by Paracoccus versutus LYM were investigated. Results indicated that His significantly promoted nitrite reduction. The inhibition effects of CoHis absorbent could be substantially alleviated by increasing the initial His/Co2+ to 4 or higher. CoHis with concentrations of 4, 8, 12, 16 and 20 mM presented no distinct effect on nitrite reduction, but slightly inhibited the reduction of nitrate, resulting in longer lag of nitrate reduction, and obviously promoted the growth of strain LYM. In the presence of 5, 10, 15 and 20 mM CoHis absorbent, the main denitrification product was N2 (not less than 95.0%). This study is of significance in verifying the applicability of Co(II)His in the CABR process, and provides a referable CoHis absorbent concentration as 20 mM with an initial His/Co2+ of 4 for the future experiments.

scholarly journals Vertical segregation among pathways mediating nitrogen loss (N<sub>2</sub> and N<sub>2</sub>O production) across the oxygen gradient in a coastal upwelling ecosystem

2017 ◽  
Vol 14 (20) ◽  
pp. 4795-4813 ◽  
Author(s):  
Alexander Galán ◽  
Bo Thamdrup ◽  
Gonzalo S. Saldías ◽  
Laura Farías
Keyword(s):  
Coastal Upwelling ◽  
Nitrite Reduction ◽  
15N Tracer ◽  
Ammonium Oxidation ◽  
N Loss ◽  
N2o Production ◽  
Coastal System ◽  
Central Chile ◽  
N Removal ◽  
Bottom Waters

Abstract. The upwelling system off central Chile (36.5° S) is seasonally subjected to oxygen (O2)-deficient waters, with a strong vertical gradient in O2 (from oxic to anoxic conditions) that spans a few metres (30–50 m interval) over the shelf. This condition inhibits and/or stimulates processes involved in nitrogen (N) removal (e.g. anammox, denitrification, and nitrification). During austral spring (September 2013) and summer (January 2014), the main pathways involved in N loss and its speciation, in the form of N2 and/or N2O, were studied using 15N-tracer incubations, inhibitor assays, and the natural abundance of nitrate isotopes along with hydrographic information. Incubations were developed using water retrieved from the oxycline (25 m depth) and bottom waters (85 m depth) over the continental shelf off Concepción, Chile. Results of 15N-labelled incubations revealed higher N removal activity during the austral summer, with denitrification as the dominant N2-producing pathway, which occurred together with anammox at all times. Interestingly, in both spring and summer maximum potential N removal rates were observed in the oxycline, where a greater availability of oxygen was observed (maximum O2 fluctuation between 270 and 40 µmol L−1) relative to the hypoxic bottom waters ( <  20 µmol O2 L−1). Different pathways were responsible for N2O produced in the oxycline and bottom waters, with ammonium oxidation and dissimilatory nitrite reduction, respectively, as the main source processes. Ammonium produced by dissimilatory nitrite reduction to ammonium (DNiRA) could sustain both anammox and nitrification rates, including the ammonium utilized for N2O production. The temporal and vertical variability of δ15N-NO3− confirms that multiple N-cycling processes are modulating the isotopic nitrate composition over the shelf off central Chile during spring and summer. N removal processes in this coastal system appear to be related to the availability and distribution of oxygen and particles, which are a source of organic matter and the fuel for the production of other electron donors (i.e. ammonium) and acceptors (i.e. nitrate and nitrite) after its remineralization. These results highlight the links between several pathways involved in N loss. They also establish that different mechanisms supported by alternative N substrates are responsible for substantial accumulation of N2O, which are frequently observed as hotspots in the oxycline and bottom waters. Considering the extreme variation in oxygen observed in several coastal upwelling systems, these findings could help to understand the ecological and biogeochemical implications due to global warming where intensification and/or expansion of the oceanic OMZs is projected.

scholarly journals A Study on the Mechanism and Kinetic of Nitrate Reduction by the nZVI-g-C3N4/TiO2  Composite Under the Simulated Sunlight

2021 ◽  
Author(s):  
Linyu Wei ◽  
Jing Tian ◽  
Qing Wang ◽  
Yuanyuan Liu ◽  
Yi Yu ◽  
...  
Keyword(s):  
Nitrate Reduction ◽  
Reduction Method ◽  
Nitrate Removal ◽  
Simulated Sunlight ◽  
Photoelectric Properties ◽  
Phase Reduction ◽  
Reduction Efficiency ◽  
Initial Ph ◽  
Lamp System

Abstract g-C3N4/TiO2 composite has excellent photoelectric properties and is considered as a good carrier of nanoparticles. A novel composite of nZVI-g-C3N4/TiO2 was successfully synthesized through in-situ growth nZVI on the surface of g-C3N4/TiO2 with liquid phase reduction method. The composite was characterized by TEM, XRD, EDS and evaluated its nitrate removal efficiency. The effects of composite dosage, solution initial pH and HCOOH concentration on nitrate reduction were investigated. The results showed that nitrate was rapidly reduced by nZVI-g-C3N4/TiO2 composite. The dosage of 4 g/L nZVI-g-C3N4/TiO2 composite and 3.0 mM of HCOOH concentration was more suitable for nitrate reduction. Solution initial pH had little impact on the nitrate reduction efficiency, but affected the proportion of the nitrate reduction products. The mechanism of nitrate reduction in the nZVI-gC3N4/TiO2/HCOOH-Xe-lamp system was proposed. The nZVI-gC3N4/TiO2 composite could be considered as a viable and promising technology for water pollution remediation.

Sign in / Sign up

Export Citation Format

Share Document