Denitrification Characteristics Research Articles

Denitrification characteristics and reaction mechanism of Ce-doped Fe-based catalysts from modified metallurgical dust containing iron

Denitrification characteristics and reaction mechanism of Ce-doped Fe-based catalysts from modified metallurgical dust containing iron

Denitrification characteristics and potential application of a novel aerobic denitrifying bacterium, Pseudomonas plecoglossicida, isolated from the Exopalaemon carinicauda pond

Denitrification characteristics and potential application of a novel aerobic denitrifying bacterium, Pseudomonas plecoglossicida, isolated from the Exopalaemon carinicauda pond

The denitrification characteristics of Na2S2O8 solution in a falling film reactor

ABSTRACT Wet scrubbing technology is an effective emission control technology for marine diesel engines. Nitric oxide (NO) is one of the main component of ship emissions, the sodium persulfate (Na2S2O8) can facilitate the NO mass transfer process to a rapid reaction. Falling film reactors are widely used in rapid gas–liquid reactions, however, the reaction characteristics of denitrification using Na2S2O8 solution in a falling film reactor are not clear, which were investigated in this paper. The factors of NO mass transfer flux were tested with the liquid–gas ratio of 15 L/m3. The effects of solution properties and temperatures on the reaction driving force were studied by calculating the chemical reaction equilibrium constants and Gibbs free energy changes. The results showed that the NO mass transfer flux increased with the increase of temperature, Na2S2O8 concentration, O2 concentration and NO concentration. NO mass transfer flux increased by 41.00% and then decreased by 2.12% as the pH value increased from 7 to 10 and then rising to 12. The Gibbs free energy changes of alkaline solutions were 114.22%−130.99% lower than those of acidic solution at 303–343 K, and the chemical reaction equilibrium constants were higher. Na2S2O8/seawater system has great application potential in marine exhaust gas purification.

Study on Screening and Denitrification Characteristics of Highly Efficient Aerobic Denitrifying Bacteria from Lake Sediments

Study on Screening and Denitrification Characteristics of Highly Efficient Aerobic Denitrifying Bacteria from Lake Sediments

Denitrification Characteristics of the Low-Temperature Tolerant Denitrification Strain Achromobacter spiritinus HS2 and Its Application.

The low-temperature environment significantly inhibits the growth and metabolism of denitrifying bacteria, leading to an excessive concentration of ammonia nitrogen and total nitrogen in sewage treatment plants during the cold season. In this study, an efficient denitrifying strain of heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria named HS2 was isolated and screened from industrial sewage of a chemical factory in Inner Mongolia at 8 °C. The strain was confirmed to be Achromobacter spiritinus, a colorless rod-shaped bacterium. When cultured with sodium succinate as the carbon source, a carbon-to-nitrogen ratio of 20-30, a shaking rate of 150-180 r/min, and an initial pH of 6-10, the strain HS2 exhibited excellent nitrogen removal at 8 °C. Through the results of whole-genome sequencing, gene amplification, and gas product detection, the strain HS2 was determined to possess key enzyme genes in both nitrification and denitrification pathways, suggesting a HN-AD pathway of NH4+-N → NH2OH → NO2-N → NO → N2O → N2. At 8 °C, the strain HS2 could completely remove ammonia nitrogen from industrial sewage with an initial concentration of 127.23 mg/L. Microbial species diversity analysis of the final sewage confirmed Achromobacter sp. as the dominant genus, which indicated that the low-temperature denitrifying strain HS2 plays an important role in nitrogen removal in actual low-temperature sewage.

Genome-Resolved Metagenomics and Denitrifying Strain Isolation Reveal New Insights into Microbial Denitrification in the Deep Vadose Zone.

The heavy use of nitrogen fertilizer in intensive agricultural areas often leads to nitrate accumulation in subsurface soil and nitrate contamination in groundwater, which poses a serious risk to public health. Denitrifying microorganisms in the subsoil convert nitrate to gaseous forms of nitrogen, thereby mitigating the leaching of nitrate into groundwater. Here, we investigated denitrifying microorganisms in the deep vadose zone of a typical intensive agricultural area in China through microcosm enrichment, genome-resolved metagenomic analysis, and denitrifying bacteria isolation. A total of 1000 metagenome-assembled genomes (MAGs) were reconstructed, resulting in 98 high-quality, dereplicated MAGs that contained denitrification genes. Among them, 32 MAGs could not be taxonomically classified at the genus or species level, indicating that a broader spectrum of taxonomic groups is involved in subsoil denitrification than previously recognized. A denitrifier isolate library was constructed by using a strategy combining high-throughput and conventional cultivation techniques. Assessment of the denitrification characteristics of both the MAGs and isolates demonstrated the dominance of truncated denitrification. Functional screening revealed the highest denitrification activity in two complete denitrifiers belonging to the genus Pseudomonas. These findings greatly expand the current knowledge of the composition and function of denitrifying microorganisms in subsoils. The constructed isolate library provided the first pool of subsoil-denitrifying microorganisms that could facilitate the development of microbe-based technologies for nitrate attenuation in groundwater.

Mechanism of additional carrier with seasonal temperature changes enhanced ecological floating beds for non-point source pollution water treatment

The continuous performance and denitrification characteristics of carriers were investigated in two modified enhanced ecological floating beds (EFBs), one with only ceramsite and the other with ceramsite and extra additional stereo-elastic packing. Over a period of more than 414 days, the extra carrier was found to improve nitrogen removal while enhancing the system's resistance to seasonal temperature variations. The denitrification of all carriers in EFBs was inhibited in practice by seasonal temperature change, especially temperature rose from below 20 °C to above 20 °C and the inhibition rate of nitrous nitrogen (NO2−-N) reduction was consistently above 91%, which was higher than that of nitrate nitrogen (NO3−-N). However, the denitrification process including the rate and the resistance to temperature changes of ceramsite in the same EFBs with stereo-elastic packing at different temperatures, was consistently improved. The removal rate of NO3−-N and NO2−-N increased by up to 23.5% and 19.5%, respectively. The potential denitrification rates of all carriers increased with time which was also evidenced by in PICRUSt results, which showed that the abundances of predicted functional genes encoding NO3−-N and NO2−-N reductase increased over time. The dominant denitrifier also differed over time due to seasonal temperature changes.

Microbial denitrification characteristics of typical decentralized wastewater treatment processes based on 16S rRNA sequencing.

Despite the widespread application of decentralized wastewater treatment (WWT) facilities in China, relatively few research has used the multi-media biological filter (MMBF) facilities to investigate the microorganism characteristics. This study utilizes 16S rRNA high-throughput sequencing (HTS) technology to examine the microbial biodiversity of a representative wastewater treatment (WWT) system in an expressway service area. The pathways of nitrogen removal along the treatment route were analyzed in conjunction with water quality monitoring. The distribution and composition of microbial flora in the samples were examined, and the dominant flora were identified using LEfSe analysis. The FAPROTAX methodology was employed to investigate the relative abundance of genes associated with the nitrogen cycle and to discern the presence of functional genes involved in nitrogen metabolism. On average, the method has a high level of efficiency in removing COD, TN, NH3-N, and TP from the effluent. The analysis of the microbial community identified a total of 40 phyla, 111 classes, 143 orders, 263 families, and 419 genera. The phyla that were predominantly observed include Proteobacteria, Acidobacteria, Chloroflexi, Actinobacteria, Nitrospirae, Bacteroidetes. The results show that the system has achieved high performance in nitrogen removal, the abundance of nitrification genes is significantly higher than that of other nitrogen cycle genes such as denitrification, and there are six nitrogen metabolism pathways, primarily nitrification, among which Nitrospirae and Nitrospira are the core differentiated flora that can adapt to low temperature conditions and participate in nitrification, and are the dominant nitrogen removal flora in cold regions. This work aims to comprehensively investigate the diversity and functional properties of the bacterial community in decentralized WWT processes.

The reusing of waste bio-oil as additive on enhanced urea-based selective non-catalytic reduction denitrification

Pyrolysis polygeneration has been proven to be effective in solid waste recycling, while cleaner production is hindered by nitrogen oxide emissions and waste oil utilization. In this study, waste bio-oil was proposed as additive for promoting urea-based selective non-catalytic reduction (SNCR) denitrification efficiency to establish bio-oil reusing process and the influence of waste bio-oil on promoting SNCR denitrification were investigated. Then the effects of temperature, bio-oil components and fly ash on SNCR denitrification characteristics were explored. The results illustrated that 5 wt% bio-oil additives would widen the optimum denitrification temperature window by 24.8 % (from 210.25 to 262.43 °C), reduce the reduction temperature by 62.11 °C (from 944.04 to 881.93 °C), and increase the denitrification efficiency by 21 %. Among the main components in waste bio-oil, acetic acid was more effective than phenol and furfural in promoting SNCR denitrification under 900 °C, a large amount of OH was produced to promote the reduction of NH3 and HNCO. In addition, the existence of fly ash could promote urea oxidation and reduce denitrification efficiency because of the catalytic effect of CaO and Fe2O3 on urea oxidation.

Biological denitrification potential of cellulase-producing Cupriavidus sp. ZY7 and denitrifying Aquabacterium sp. XL4 at low carbon-to-nitrogen ratio: Performance and synergistic properties

This study emphasizes on the cellulase production characteristics of strain ZY7 and its collaboration with nitrate-dependent ferrous oxidizing (NFO) strain XL4 to achieve efficient denitrification at low carbon-to-nitrogen (C/N) ratio. Results indicated that the denitrification efficiency increased from 65.47 to 97.99% at 24 h after co-culture at C/N of 1.0. Three-dimensional fluorescence excitation-emission matrix (3D-EEM) showed significant changes in the intensity of soluble microbial products (SMP), fulvic-like materials, and aromatic proteins after co-culture. Bio-precipitates were characterized by Scanning electron microscope (SEM), Fourier transform infrared spectrometer (FTIR), and X–ray diffraction (XRD), which showed that cellulose structure was disrupted and the metabolites were potential carbon source for denitrification. In addition, cellulase activity suggested that the hydrolysis of β-1,4-glycosidic bonds and oligosaccharides may be the rate-limiting steps in cellulose degradation. This work promoted the understanding of denitrification characteristics of co-culture and expanded the application of cellulose degrading bacteria in sewage treatment.

Nitrogen removal by two strains of aerobic denitrification actinomycetes: Denitrification capacity, carbon source metabolic ability, and raw water treatment

The denitrification characteristics of actinomyetes in aquatic ecosystem under aerobic conditions are not well known. Here, two actinomyetes strains M5 and M6 were separated and annotated as Streptomyces sp. Strains M5 and M6 could reduce 95.02% and 96.84 % of total nitrogen, 98.14 % and 97.02 % of total organic carbon under aerobic condition. Nitrogen balance analysis indicated that 78.60 % and 83.01 % of nitrogen was translated into gaseous, with 13.48 % and 10.77 % of nitrogen was assimilated into biomass for strains M5 and M6. The highest removal efficiency of nitrate of strains M5 and M6 in micro-polluted water bodies were 88.61 % and 82.53 %, respectively. Moreover, strains M5 and M6 exhibited remarkable carbon metabolic capacity, especially for esters. Altogether, this study provides a new perspective for understanding the performance of actinomyetes in aerobic denitrification and micro-polluted water reparation.

Cultivation of aerobic granular sludge coupled with built-in biochemical cycle galvanic-cells driven by dual selective pressure and its denitrification characteristics

Dual selective pressure was applied as the driving condition to cultivate an enhanced aerobic granular sludge (AGS) with Fe(0)-based biochemical cycle galvanic-cells (BCGC) as the core. The BCGC-AGS coupled micro-electrolysis with synergistic autotrophic-heterotrophic denitrification to enhance nitrogen removal. COD and total nitrogen removal of 91.8% and 95.9% were achieved, respectively. The formation of circulation channel between Fe3+ and Fe2+ provided a solid foundation for the biochemical cycle of galvanic-cells with low consumption. The existence of micro-electrolysis selective pressure in BCGC-AGS was also confirmed. Facultative aerobic bacteria Methylocystis and Azospirillum were the most abundant genera. Facultative iron redox bacteria and autotrophic denitrifying bacteria Geobacter, Thiobacillus, Aquabacterium, Thauera and Azospirillum showed high abundance, affirming the success culture of EAGS system. Load shock test verified BCGC-AGS possessed excellent load shock resistance. Obtaining the advantages of fast-cultivation, high-efficiency and low galvanic-cells consumption, BCGC-AGS showed significant potential for practical application.

Cross-basin differences in the nutrient assimilation characteristics of induced phytoplankton blooms in the subtropical Pacific waters

Abstract. To better understand the nutrient assimilation characteristics of subtropical phytoplankton, deep-water addition incubation experiments were carried out on surface waters collected at seven stations across the subtropical North and South Pacific Ocean. These deep-water additions induced phytoplankton blooms with nutrient drawdown at all stations. The drawdown ratios of dissolved inorganic nitrogen (DIN) to phosphate (PO4) varied from 14.1 to 30.7 at the PO4-replete stations in the central North Pacific (CNP) and eastern South Pacific (ESP). These ratios were similar to the range represented by the canonical Redfield ratio (16) through to typical particulate N:P ratios in the surface subtropical ocean (28). In contrast, lower DIN:PO4 drawdown ratios (7.7–13.3) were observed in induced blooms at the PO4-depleted stations in the western North Pacific (WNP). The DIN:PO4 drawdown ratios in the PO4-replete ESP were associated with eukaryote-dominated blooms, while those in the PO4-depleted WNP were associated with eukaryotic and cyanobacterial blooms. The surplus PO4 assimilation, relative to DIN, by phytoplankton in the WNP was not expected based on their typical cellular N:P ratio and was likely due to the high PO4 uptake capability as induced by low-PO4-adapted phytoplankton. The low- and high-P* (=PO4- DIN/16) regimes geographically corresponded to the low and high DIN:PO4 drawdown ratios in the WNP and the CNP or ESP, respectively. The basin-wide P* distribution in the oligotrophic Pacific surface waters showed a clear regional trend from low in the WNP (<50 nM) to high in the ESP (>100 nM). These results suggest that the subtropical phytoplankton blooms as observed in our experiments could be an important factor controlling P* as well as the commonly recognized dinitrogen fixation and denitrification characteristics.

Nitrate reduction by the aerobic denitrifying actinomycete Streptomyces sp. XD-11-6-2: Performance, metabolic activity, and micro-polluted water treatment

Aerobic denitrifying bacteria were widely reported in different nitrogen polluted aquatic ecosystem. However, the aerobic denitrification characteristics of actinomycete were not well understood. Here, the actinomycete strain XD-11-6-2 was isolated from reservoir and identified as Streptomyces sp. XD-11-6-2 by DNA sequencing. Strain XD-11-6-2 removed 90.34% of total organic carbon and 93.66% of total nitrogen under aerobic condition. A total of 77.87% of nitrogen was removed as a gaseous product, and 15.67% of nitrogen was converted into biomass. Biolog combined with network model indicated that strain XD-11-6-2 could use six types of carbon sources, and exhibit outstanding capacity to metabolize diverse carbon sources. Moreover, the highest nitrate and total nitrogen removal efficiencies of raw water were 72.29% and 74.86%, respectively. In general, these results provide new insights to understand the potential of actinomycetes in treating micro-polluted water.

Effect of current on biofilm-electrode reactor coupled with sulfur autotrophic denitrification process (BER-SAD) for nitrate removal from wastewater

The biofilm-electrode reactor coupled with sulfur autotrophic denitrification process (BER-SAD) was used to remove nitrate in groundwater, and the effect of current intensity on the denitrification characteristics of the coupled process was explored. Current intensity had a great influence on the denitrification effect of the coupled process, the maximum nitrate removal efficiency of 99.9% and lowest nitrite production were gained under the optimum current density of 100 mA. Moreover, the accumulation concentration of SO42- increased gradually with the increase of current intensity. With the increase of current intensity, the proportion of hydrogen autotrophic denitrification decreased, while the proportion of sulfur autotrophic denitrification increased.

Heterotrophic nitrification-aerobic denitrification characteristics and antibiotic resistance of two bacterial consortia from Marinomonas and Halomonas with effective nitrogen removal in mariculture wastewater

Heterotrophic nitrification-aerobic denitrification (HNAD) characteristics and antibiotic resistance of two bacterial consortia, Marinomonas communis &Halomonas titanicae (MCH) and Marinomonas aquimarina &Halomonas titanicae (MAH), and their single isolates (MC, MA, and H) were determinated in this study. When cultured in sole and mixed N-source media (NH4+-N and/or NO2−-N of 10 mg/L), MCH and MAH exhibited greater efficiency and stability of inorganic-N removal than single isolates, and these strains preferred to remove NH4+-N by simultaneous HNAD in mixed N-source media. Meanwhile, 45%–70% of NH4+-N and/or NO2−-N was mainly converted to organic nitrogen (15%–25%) and gaseous nitrogen (30%–40%) by these strains, and more inorganic-N was transformed to intracellular-N by MCH and MAH via assimilation instead of gaseous-N production by denitrification. Both isolates and their consortia had the maximal NH4+-N or NO2−-N removal efficiency above 95% under the optimum conditions including temperature of 20–30 °C, C/N ratios of 15–20, and sucrose as carbon source. Interestingly, bacterial consortia performed greater nitrogen removal than single isolates under the low temperature of 10 °C or C/N ratios of 2–5. In real mariculture wastewater, MCH and MAH also showed higher NH4+-N removal efficiency (65%–68%) and more stable cell quantity (4.2–5.2 × 108 CFU/mL) than single strains, due to the interspecific coexistence detected by bacterial quantitation with indirect immunoassay. Additionally, these isolates and consortia had stronger resistances to polypeptides, tetracyclines, sulfonamides, furanes, and macrolides than other antibiotics. These findings will be conducive to the applications of HNAD bacteria of Marinomonas and Halomonas on reducing nitrogen pollution in mariculture or other saline environments.

Contrasting subsurface denitrification characteristics under temperate pasture lands and its implications for nutrient management in agricultural catchments

Subsurface denitrification plays a key role in the reduction or ‘attenuation’ of nitrate contamination of groundwater and surface waters. We investigated subsurface denitrification characteristics in the vadose zone and shallow groundwater at four sites under pastoral farming in the Manawatū River catchment, located in the lower part of North Island, New Zealand. The denitrification potential of the vadose zone was determined by the laboratory incubation assays measuring the denitrifying enzyme activity (DEA) in soil samples collected from different soil horizons (up to 2.1 m below ground surface), whereas denitrification rates in shallow groundwaters were measured in situ by single-well, push-pull tests conducted in piezometers installed at multiple depths at the study sites. Soils and underlying geology, defining hydrogeologic settings, appear to influence the spatial variability of subsurface denitrification characteristics at the study sites. Where the vadose zone is thin and composed of coarse-textured soils, percolation of nitrate was evident in observed high nitrate-nitrogen concentrations (>5 mg L−1) in oxic and young shallow groundwaters, but low nitrate-nitrogen concentrations (<0.05 mg L−1) were observed in the reduced shallow groundwater found underneath the fine textured soils and/or a thick vadose zone. This was confirmed by the push-pull tests measuring denitrification rates from 0.08 to 1.07 mg N L−1 h−1 in the reduced shallow groundwaters (dissolved oxygen or DO < 0.5 mg L−1), while negligible in the oxic groundwaters (DO > 5 mg L−1) found at the study sites. These contrasting subsurface denitrification characteristics determine the ultimate delivery of nitrate losses from agricultural soils to receiving waters, where the fine textured thick vadose zone and reducing groundwater conditions offer nitrate reduction in the subsurface environment.

The mixotrophic denitrification characteristics of Zoogloea sp. L2 accelerated by the redox mediator of 2-hydroxy-1,4-naphthoquinone

Denitrification in mixed culture system has been extensively researched to date, but few studies have focused on accelerating the process using redox mediators to promote electron transfer. Strain L2, an iron-reducing bacteria, can remove 75.44% of nitrate under temperature of 30.60 °C, pH of 6.75 and Fe2+ concentration of 27.86 mg·L−1. Additionally, the removal rate of nitrate reached 1.516 mg·L−1·h−1 in 8 h with the addition of 0.030 mmol·L−1 2-hydroxy-1,4-naphthoquinone (HNQ), which increased by 1.38 times than control group. Furthermore, analysis by fluorescence spectroscopy, flow cytometer and gas chromatography demonstrated that HNQ positively stimulated denitrification. This study provides a reference for enhancing denitrification in mixed culture and lays the foundation for the practical application of redox mediators in groundwater treatment.

Effect of hydraulic retention time, ZVI concentration, and Fe2+ concentration on autotrophic denitrification efficiency with iron cycle bacterium strain CC76

ABSTRACT The immobilized reactor of iron-reducing bacteria and zero-valent iron (ZVI) integrated system was established. This study has shown that the effects of hydraulic retention times (9, 11, 13 h), ZVI concentrations (2, 4, 6, 8 mg/L), and Fe2+ concentrations (5, 10, 15 mg/L) on the denitrification characteristics of iron cycle bacterium strain CC76. The results show that the longer the HRT is, the stronger ability of bacteria to remove nitrate. When ZVI concentration was 4 mg/L and the Fe2+ concentration is 15 mg/L, the removal efficiency of nitrate was the highest, reaching the maximum value of 93.02% (1.07 mg/L/h). Since increasing ZVI concentration in a certain range can not only promote chemical reduction but also make use of strain CC76 as an electron donor. Also, the abundance of strain CC76 decreased with the increase of ZVI concentration, which indicated that adding a low concentration of ZVI could reduce the inhibitory effect on bacteria. Hypothesis analysis of principal components showed that a low concentration of ZVI is beneficial to increase nitrate removal rate. Community structure analysis indicated that strain CC76 and related bacteria were the most abundant bacteria in the reactor.

Denitrification characteristics and pathways of a facultative anaerobic denitrifying strain, Pseudomonas denitrificans G1

Excessive nitrate in aquaculture systems has attracted wide attention. To isolate novel aerobic denitrifying strain and characterize its nitrogen removal processes, a facultative anaerobic denitrification bacterium, identified as Pseudomonas denitrificans G1, was isolated from marine sediments. Strain G1 could grow and remove 90-98% of nitrate and 97-99% of nitrite under an aerobic or anaerobic condition in 24h, with the total nitrogen removal rate of 33-38% (87-100mg/L). The highest denitrification rate could reach 15.1 mg/(L·h). The suitable condition for the denitrification of G1 is C/N ratio 5-22, dissolved oxygen 0-4.68mg/L, salinity 0-30g NaCl/L, pH 7-9.5. Under the aerobic condition, G1 grew fast; however, the mass spectrographic analysis showed that the gas product was N2O. Under the anaerobic conditions, G1 grow relatively slowly, but could also achieve effective denitrification and the final product was N2. In denitrification of aquaculture wastewater, strain G1 can remove 60.57% of nitrate and 36.36% of total nitrogen; meanwhile, there was a slight accumulation of ammonia nitrogen. P.denitrificans strain G1 has potential in denitrification processes for the treatment of aquaculture wastewater. However, the regulation of reaction conditions and gas products needs to be further studied.