Simultaneous Removal Of Nitrate Research Articles

Simultaneous removal of nitrate, manganese, zinc, and bisphenol a by manganese redox cycling system: Performance and mechanism

The manganese(Mn) redox cycling system in this work was created by combining Mn(IV)-reducing bacteria MFG10 with Mn(II)-oxidizing bacteria HY129. The biomanganese oxides (BMO) generated by strain HY129 were transformed by strain MFG10 to Mn(II), finishing the Mn redox cycling, in which nitrate (NO3–-N) was converted to nitrite, which was further reduced to nitrogen gas. The system could achieve 85.7 % and 98.8 % elimination efficiencies of Mn(ⅠⅠ) and NO3–-N, respectively, at Mn(ⅠⅠ) = 20.0 mg/L, C/N = 2.0, pH = 6.5, and NO3–-N = 16.0 mg/L. The removal of bisphenol A (BPA) and zinc (Zn(II)) at 36 h reached 91.7 % and 89.7 % under the optimal condition, respectively. Furthermore, the Mn redox cycling system can reinforce the metabolic activity and electron transfer activity of microorganisms. The findings showed that the adsorption by bioprecipitation throughout the Mn cycling was responsible for the elimination of Zn(II) and BPA.

Application of Hydrogen-Based Denitrification: Simultaneous Removal of Nitrate and Reactive Black 5 Dye from Textile Wastewater Containing Organic Matter

In this study, a hydrogen-based denitrification (HD) reactor was used to investigate the simultaneous treatment of nitrogen and decolorization in textile wastewater contaminated with organic matter. The reactor operated in two phases: without and with organic matter. Despite the short hydraulic retention time, the HD system successfully removed all pollutants, including nitrate, nitrite, reactive black-5 dye and chemical oxygen demand. The unhindered treatment efficiency for nitrogen and decolorization in the presence of organic pollutants was observed. With the addition of organic matter, the nitrogen removal efficiency increased slightly from 85% to 90–100%, and the decolorization rate doubled from 25% to 50–60%. Organic matter played a crucial role in stimulating heterotrophic bacteria during biological denitrification and acted as a carbon source facilitating biological denitrification and azo bond cleavage during dye degradation. Despite the generation of toxic byproducts and changes in the dominant microbial community, the treatment efficiency remained stable and improved. This approach offers a promising solution for enhancing treatment efficiency in textile wastewater, providing a cost-effective and environmentally friendly option for developing countries to treat wastewater before discharge.

Simultaneous Removal of Nitrate and Phosphate in a Pyrrhotite and Sulfur-Circulating Packed Bed Reactor

A pyrrhotite and sulfur-circulating packed bed reactor (PS-CPBR) was constructed to study the removal process and mechanism of NO3−-N and PO43−-P with different electron donors. The results showed that the NO3−-N and PO43−-P removal performance of mixed electron donors (pyrrhotite and sulfur) was superior to the single electron donor (pyrrhotite). The optimum conditions of NO3−-N and PO43−-P removal in the PS-CPBR were a hydraulic retention time (HRT) of 12 h and a C/N of 0, and the average removal efficiency was 100% and 86.39%. The sulfur in mixed electron donors was able to promote the dissolution of pyrrhotite and the formation of polysulfide to increase the effectiveness of electron donors, promoting the removal of NO3−-N, while the PO43−-P was removed in the form of FePO4 precipitation. Microbial and functional gene analyses demonstrated that different electron donors were able to influence the abundance of microbial communities and denitrification functional genes. Meanwhile, mixed electron donors were able to increase the protein content of biofilms and reduce the resistance of electron transfer between microorganisms and electrons.

Simultaneous removal of nitrate and pesticides from contaminated groundwater using aerobic granular biomass technology

Aerobic Granular Biomass (AGB) technology is widely used for urban and industrial wastewater treatment, however, its application in groundwater remediation, is practically unknown. A mixture of carbendazim, simazine, and diuron were amended to the nitrate-polluted synthetic groundwater at increasing concentrations to validate the ability of technology to remove both kind of pollutants, pesticides and nitrate which are commonly found in the water resources. The nitrate removal was a success with values below 0.010 g·L-1. The increased concentration of pesticides in the influent did not distort the pattern observed for pesticide removal. Carbendazim was almost completely eliminated, followed by simazine elimination, while diuron showed adsorption-desorption patterns during experimentation. The addition of pesticides had a drastic effect on the basal community conducted by proliferation of Hyphomicrobium and Dokdonella. The pesticide compounds had a negative effect on number of copies for fungal population, while archaeal population was unharmed, according to qPCR results. Denitrifying bacteria need 70 days as acclimatization period for achieving activity values as initial inoculum. The results obtained have shown for the first time the capacity of AGB system to treat groundwater polluted with nitrate and pesticide using low carbon load. Therefore, the results suggested the potential application of AGB technology for the purification of groundwater polluted with both nitrates and pesticides.

Simultaneous removal of nitrate, lead, and tetracycline by a fixed−biofilm reactor assembled with kapok fiber and sponge iron: Comparative analysis of operating conditions and biotic community

In recent years, under the condition of lack of carbon source, the presence of composite micro−pollutants make the removal of nitrate seriously damaged, and to find a suitable way to solve this problem is imminent. A fixed−biofilm carrier modified by mixing sponge iron (SI) and kapok fiber (KF) combined with strain Zoogloea sp. FY6 was constructed in this study to get a fixed−biofilm reactor with merit denitrification performance. By adjusting the operation parameters, it can be concluded that when the carbon to nitrogen (C/N) ratio was 1.5, the hydraulic retention time (HRT) was 6.0 h, and the pH was 6.0, the nitrate removal efficiency (NRE) of the fixed−biofilm reactor was up to 95.4% (2.95 mg L−1 h−1). In addition, the fixed−biofilm reactor constructed in this study can remove lead (Pb2+) and tetracycline (TC) excellently in the presence of SI and Zoogloea sp. FY6, and the denitrification performance can still maintain a high level under the influence of different concentrations of Pb2+ and TC. Furthermore, the addition of SI not only removes the compound pollutants, but also protects the toxicity of the pollutant inflow in the bioreactor, and the metabolic process of microorganisms in the bioreactor also removes some of the compound pollutants. The high−throughput data showed the abundance of strain Zoogloea sp. FY6 was still the highest value under the influence of various pollutants, and the metagenomic prediction showed that the fixed−biofilm reactor had perfect denitrification process and iron redox cycle benefits. This study provides a valuable reference for sustainable utilization of natural biological resources and reduction of material costs in wastewater treatment plants (WWTPs).

The application of post-denitrification fixed biofilm reactor for polishing secondary effluent: Nitrate removal, soluble microbial products and micropollutants biotransformation

This study was conducted to comprehensively evaluate the role of hydraulic retention time (HRT) on simultaneous removal of nitrate and micropollutants (MPs) in secondary effluent from wastewater treatment plants in post-denitrification fixed biofilm reactor (PDFBR). Results showed that PDFBR was favorable for nitrate removal (above 94%). Prolonged HRT promoted the bio-utilization of nonaromatic soluble microbial products with low molecular weight and reduced biomass production. MPs was partially removed in PDFBRs (below 48%). Microbial diversity increased along the extending of HRT and thus partially enhanced MPs removal. Batch experiments showed that changing HRT had no direct impact on the biodegradation rates of the selected MPs. Correlation analysis revealed that Dechloromonas, Terrimonas, and Phreatobacter were reasonable for simultaneous removal of MPs and nitrate. The abundance of nosZ gene had a rapid decrease under extreme HRT. This study provides insights into polishing nitrate and MPs from secondary effluent in a denitrifying biofilm system.

Cyclohexanecarboxylic acid degradation with simultaneous nitrate removal by Marinobacter sp. SJ18.

Naphthenic acid (NA) is a toxic pollutant with potential threat to human health. However, NA transformations in marine environments are still unclear. In this study, the characteristics and pathways of cyclohexanecarboxylic acid (CHCA) biodegradation were explored in the presence of nitrate. The results showed that CHCA was completely degraded with pseudo-first-order kinetic reaction under aerobic and anaerobic conditions, accompanied by nitrate removal rates exceeding 70%, which was positively correlated with CHCA degradation (P < 0.05). In the proposed CHCA degradation pathways, cyclohexane is dehydrogenated to form cyclohexene, followed by ring-opening by dioxygenase to generate fatty acid under aerobic conditions or cleavage of cyclohexene through β-oxidation under anaerobic conditions. Whole genome analysis indicated that nitrate was removed via assimilation and dissimilation pathways under aerobic conditions and via denitrification pathway under anaerobic conditions. These results provide a basis for alleviating combined pollution of NA and nitrate in marine environments with frequent anthropogenic activities.

Simultaneous removal of nitrate and ammonium by hydrogen-based partial denitrification coupled with anammox in a membrane biofilm reactor

Hydrogen-based membrane biofilm reactors (MBfRs) are effective for nitrogen removal. However, the safety of hydrogen limited the application of MBfR. Here, a hydrogen-based partial denitrification system coupled with anammox (H2-PDA) was constructed in an MBfR for reducing hydrogen demand significantly. The metabolomics and structures of microbial communities were analyzed to determine the phenotypic differences and drivers underlying denitrification, anammox, and H2-PDA. These findings indicated that total nitrogen (TN) removal increased from 57.1% in S1 to 93.7% in S2. During the H2-PDA process, partial denitrification and anammox contributed to TN removal by 93.7% and 6.3%, respectively. Community analysis indicated that the H2-PDA system was dominated by the genus Meiothermus, which is involved in partial denitrification. Collectively, these findings confirmed the feasibility of incorporating the H2-PDA process in a MBfR and form a foundation for the establishment of novel and practical methods for efficient nitrogen removal.

Simultaneous removal of nitrate, nitrobenzene and aniline from groundwater in a vertical baffled biofilm reactor

The challenge of simultaneous removal of nitrobenzene (NB), aniline (AN) and nitrate from groundwater in a single bioreactor is mainly attributed to the persistence of AN to degradation with anoxic denitrification conditions. In this work, simultaneous removal of NB (100 μM), AN (100 μM) and nitrate (1 mM) was achieved within 8 h with a COD/N ratio of 8 in a vertical baffled biofilm reactor (VBBR). By setting DO concentration at 0.4–0.5 mg L−1 to create a micro-aerobic condition, NB removal rate was accelerated without accumulation of AN, and AN could serve as electron donors for denitrification after ring cleavage. High-throughput sequencing showed that biofilm was predominated by denitrifiers (Luteimonas, Planctomyces, Thiobacillus, Thauera and so on) and NB-degrading bacteria (Pseudomonas), and biodiversity varied vertically along the height of the reactor. A dominantly anaerobic pathway for reducing NB to AN was identified by PICRUSt analysis, as the predicted genes involved in aerobic transformation of NB were several magnitudes lower than those in the anaerobic pathway. This study provided a new insight to the role of oxygen in robust bioremediation groundwater contaminated with NB, AN and nitrate.

Synchronous N and P Removal in Carbon-Coated Nanoscale Zerovalent Iron Autotrophic Denitrification─The Synergy of the Carbon Shell and P Removal.

Fe0 is a promising electron donor for autotrophic denitrification in the simultaneous removal of nitrate and phosphorus in low C/N wastewater. However, P removal may inevitably inhibit bio-denitrification. It has not been well recognized and led to an overdose of iron materials. This study employed carbon-coated zerovalent iron (Fe0@C) to support autotrophic denitrification to mitigate the inhibition effects of P removal and enhance both N and P removal. The critical role of the carbon shell in Fe0@C was to block the direct contact between Fe0 and P and NO3--N, to maintain the Fe0 activity. Besides, P inhibited the chemical reduction of NO3--N by competing for Fe0 active sites. This indirectly boosted H2 generation and promoted bio-denitrification. P removal displayed negligible effects on microbial species but indirectly enhanced the nitrogen metabolic activities because of promoted H2 in Fe0@C-based autotrophic denitrification. Bio-denitrification, in turn, strengthened Fe-P co-precipitation by promoting the formation of ferric hydroxide as a secondary adsorbent for P removal. This study demonstrated an efficient method for simultaneous N and P removal in autotrophic denitrification and revealed the synergistic interactions among N and P removal processes.

High-Performance Electrochemical Nitrate Reduction to Ammonia under Ambient Conditions Using a FeOOH Nanorod Catalyst.

Electrocatalytic nitrate reduction is promising as an environmentally friendly process to produce high value-added ammonia with simultaneous removal of nitrate, a widespread nitrogen pollutant, for water treatment; however, efficient electrocatalysts with high selectivity are required for ammonia formation. In this work, FeOOH nanorod with intrinsic oxygen vacancy supported on carbon paper (FeOOH/CP) is proposed as a high-performance electrocatalyst for converting nitrate to ammonia at room temperature. When operated in a 0.1 M phosphate-buffered saline (PBS) solution with 0.1 M NaNO3, FeOOH/CP is able to obtain a large NH3 yield of 2419 μg h-1 cm-2 and a surprisingly high Faradic efficiency of 92% with excellent stability. Density functional theory calculation demonstrates that the potential-determining step for nitrate reduction over FeOOH (200) is *NO2H + H+ + e- → *NO + H2O.

The role of nitrate in simultaneous removal of nitrate and trichloroethylene by sulfidated zero-valent Iron

Sulfidated zero-valent iron (S-ZVI) is commonly used to degrade trichloroethylene (TCE). The reactivity of S-ZVI is related to not only the properties of S-ZVI but also the geochemical conditions in groundwater, such as coexisted NO3−. Therefore, the effect of NO3− on TCE degradation by S-ZVI and its mechanism were systematically studied. 95.17% of TCE was degraded to acetylene, dichloroethene, ethene, ethane and multi‑carbon products via β-elimination by fresh S-ZVI that contained 85.31% Fe0 and 14.69% FeS in the presence of NO3−, demonstrating that NO3− did not affect the degradation pathway of TCE. While high concentration of NO3− (> 10 mg/L) competed for electrons at the Fe/FeOx interface with degradation products, leading to a continuous rising of acetylene. Moreover, the rapid reduction of NO3− to NH4+ (89.79%) at the Fe0 interface contributed to the release of 5.08 mM Fe2+ from S-ZVI, which promoted the formation of Fe3O4 with excellent electron conduction properties on the surface of S-ZVI. Accordingly, NO3− improved the degradation and electron selectivity of TCE by 51.07% and 2.79 fold, respectively. This study demonstrated that S-ZVI could remediate the contamination of NO3− and TCE simultaneously and the presence of NO3− could effectively enhance the degradation of TCE in groundwater.

Simultaneous removal of aromatic pollutants and nitrate at high concentrations by hypersaline denitrification:Long-term continuous experiments investigation

If we can use toxic aromatic compounds as supplementary carbon source, the simultaneous removal of nitrate (NO3−) and aromatic compounds may be achieved at much lower chemical costs. This study uses the expanded granular sludge bed (EGSB) reactors to investigate the hypersaline (> 3%) denitrification performance, the removal of aromatic compounds, i.e., aniline, phenol, and their mixture, and the mechanisms involved in. The four reactors exhibit high removal efficiency of NO3− (> 92.8%) and aromatic compounds (> 73.9%) at 0–1200 mg/L of aromatic compounds. The formation of toxic intermediates such as catechol and azo dyes is revealed by gas chromatography mass spectrometry (GC–MS) with and without N,O-Bis(trimethylsilyl) trifluoroacetamide (BSTFA) derivation, and their toxic effects lead to the lower cell survival ratios after exposing to phenol (64.2% ∼ 68.9%) than to aniline and mixture (72.7% ∼ 78.0%). The stable performance is associated with the more secretion of extracellular polymeric substances (EPS) and the adsorption of pollutants on EPS, and this was indicated from the higher fluorescence intensity in three-dimensional excitation-emission matrix (3D-EEM). Moreover, the Halomonas and Azoarcus show high abundance and play important roles in the removal of both NO3− and aromatic compounds. Besides, quantitative real time PCR (RT-qPCR) results demonstrate the key role of highly abundant nosZ and nirS genes in denitrification. The toxic organics in industrial wastewaters are potentially feasible carbon sources for denitrification even under high-salinity stress.

Simultaneous electrocatalytic removal of inorganic nitrogen compounds in groundwater: Modeling and mechanistic studies

The use of biological and chemical methods for the simultaneous removal of inorganic nitrogen compounds containing nitrate, ammonia, and nitrite in groundwater typically cannot achieve synchronous oxidation and reduction in an undivided reactor. In the present study, with the strict regulation of the oxidation reaction in the anode zone and reduction reaction in the cathode zone, simultaneous removal of nitrate, ammonia, and nitrite was achieved in an undivided electrochemical system. Our results indicated that ammonia and nitrite had been completely removed, and the concentration of nitrate was reduced to 8.58 mg N/L with initial nitrate, ammonia, and nitrite concentrations of 50.00, 10.00 and 5.00 mg N/L, respectively. Cyclic voltammetry (CV) and potentiostatic electrolysis revealed that the electrode surface reaction process, that is, nitrate, ammonia, and nitrite in the system, could be converted into nitrogen via ClO− generated from Cl− produced from the electrochlorination process during multiple cycle attenuation. Moreover, both CV and Density functional theory (DFT) calculations revealed the inhibitory effect of coexisting ammonia and nitrite on the electrochemical reduction of nitrate on the Cu cathode. This strategy opens a paradigm for the simultaneous efficient electrocatalytic removal of nitrate, nitrite, and ammonia in an undivided single reactor.

Simultaneous removal of nitrate, manganese, and tetracycline by Zoogloea sp. MFQ7: Adsorption mechanism of tetracycline by biological precipitation

A Mn(II) oxidizing-denitrifying and tetracycline (TC) removal bacterium Zoogloea sp. MFQ7 was isolated in this study. Nitrogen removal was 83.49% by nitrogen balance experiment. The maximum removal efficiencies of nitrate, Mn(II), and TC by strain MFQ7 within 96 h was 100.00, 74.56, and 63.59% at C/N of 2.0, pH of 7.0, Mn(II) of 20 mg L−1, temperature of 30.0 °C, and TC of 0.2 mg L−1. SEM illustrated that biogenic manganese oxides (BMO) was petal-like, XRD and XPS analyses confirmed that MnO2 was the main component of BMO. Besides, the maximum adsorption capacity of BMO for TC was 52.21 mg g−1. FTIR detected the changes in TC adsorption by BMO. Pseudo-second-order model (R2 = 0.994) explained the adsorption kinetics of TC on BMO and Langmuir isotherm model (R2 = 0.983) suggested that it was homogeneous adsorption, thermodynamics data (ΔG < 0, ΔH = 18.31 kJ mol−1, ΔS = 72.8 J (mol*K)−1) confirmed that adsorption was endothermic and spontaneous.

Simultaneous removal of nitrate and phosphate in groundwater using Ca-citrate complex.

Eutrophication can be caused by excessive input of nutrients, such as nitrate and phosphate, to surface water. Nutrients in groundwater can enter surface water by means of base flow, requiring treatment before they reach surface water bodies. While some studies have attempted to remove nitrate and phosphate, methods for simultaneous removal in groundwater have rarely been reported. In this study, we propose an innovative treatment method to simultaneously remove nitrate and phosphate in groundwater based on an injection of Ca-citrate complex. A total of five batch experiments with different conditions were conducted to identify the removal mechanisms of nitrate and phosphate and to evaluate the use of alternative organic materials, such as lactate. The results showed that Ca-citrate complex can remove nitrate and phosphate simultaneously. Nitrate was removed through denitrification by denitrifying bacteria which used citrate as a carbon source. The removal mechanisms for phosphate were precipitation of phosphate minerals (e.g., hydroxyapatite) and adsorption. The results also showed that reactive materials based on Ca-lactate complex were able to remove nitrate and phosphate. This study suggests that nitrate and phosphate in groundwater can simultaneously be removed using organic-based calcium complexes, proposing a promising remedial method to alleviate potential eutrophication in surface water as well as groundwater contamination.

The Role of Nitrate in Simultaneous Removal of Nitrate and Trichloroethylene by Sulfidated Zero-Valent Iron

The Role of Nitrate in Simultaneous Removal of Nitrate and Trichloroethylene by Sulfidated Zero-Valent Iron

Simultaneous removal of nitrate and hexavalent chromium in groundwater using indigenous microorganisms enhanced by emulsified vegetable oil: Interactions and remediation threshold values

Combined pollution in groundwater has become increasingly serious. Adding emulsified vegetable oil to an aquifer is an effective method to remediate multiple pollutants. However, the efficiency and threshold values for the remediation of groundwater contaminated by both nitrate and hexavalent chromium (Cr(VI)) stimulated by emulsified vegetable oil remain unclear. In this study, emulsified vegetable oil was used for the first time to simultaneously remediate nitrate and Cr(VI) in groundwater. The results suggested that the addition of emulsified vegetable oil could effectively remediate nitrate and Cr(VI), and there were interplay effects between nitrate and Cr(VI). Nitrate promoted Cr(VI) removal, while Cr(VI) inhibited nitrate reduction. The remediation thresholds for nitrate and Cr(VI) alone were 1600 mg/L and 10 mg/L, respectively (emulsified vegetable oil = 7 g/L). For combined pollution, the remediation threshold values were 868.10 mg/L for nitrate and 12.43 mg/L for Cr(VI) (emulsified vegetable oil = 7 g/L). The dose of emulsified vegetable oil played an important role in the threshold value. When the concentration of emulsified vegetable oil was 10.8 g/L, the maximum threshold values were 1379.79 mg/L for nitrate and 12.67 mg/L for Cr(VI). When the pollutant concentration was below the threshold value, the contaminant could be completely removed.

Simultaneous removal of nitrate and sulfate using an up-flow three-dimensional biofilm electrode reactor: Performance and microbial response

Nitrate removal from low carbon water is a problem in the water treatment, especially in the presence of high sulfate. In this work, an up-flow three-dimensional biofilm electrode reactor (3D-BER) was established to remove nitrate and sulfate from low organic carbon water. Results indicated that sulfate negatively affected nitrate removal. Moreover, high electric current and short hydraulic retention time deteriorated the performance of nitrate and sulfate removal. When the influent of SO42− was 150 mg/L, the removal efficiency of NO3−-N and SO42− was 88.49 ± 4.5% and 29.35 ± 5.5%, respectively. The high-throughput sequencing revealed that denitrifying bacteria dominated in the lower part of the reactor while sulfate reducing bacteria dominated in the upper part of the reactor. It was speculated that oxidation products of sulfide could serve as supplementary electron donors to enhance nitrate removal in the 3D-BER.

Simultaneous removal of nitrate and heavy metals in a continuous flow nitrate-dependent ferrous iron oxidation (NDFO) bioreactor

Nitrogen and heavy metals can co-occur in various industrial wastewaters such as coke-oven wastewater. Removal of these contaminants is important, but cost-efficient removal technology is limited. In this study, we examined the usefulness of nitrate-dependent ferrous iron oxidation (NDFO) for the simultaneous removal of nitrate and heavy metals (iron and zinc), by using an NDFO strain Pseudogulbenkiania sp. NH8B. Based on the batch culture assays, nitrate, Fe, and Zn were successfully removed from a basal medium as well as coke-oven wastewater containing 5 mM nitrate, 10 mM Fe(II), and 10 mg/L Zn. Zinc in the water was most likely co-precipitated with Fe(III) oxides produced during the NDFO reaction. Simultaneous removal of nitrate, Fe, and Zn was also achieved in a continuous-flow reactor fed with a basal medium containing 10 mM nitrate, 5 mM Fe(II), 4 mM acetate, and 10 mg/L Zn. However, when the reactor is fed with coke-oven wastewater supplemented with 10 mM nitrate, 5 mM Fe(II), 4 mM acetate, and 10 mg/L ZnCl2, the reactor performance significantly decreased, most likely due to the inhibition of bacterial growth by thiocyanate or organic contaminants present in the coke-oven wastewater. Use of mixed culture of NDFO bacteria and thiocyanate/organic-degrading denitrifiers should help improve the reactor performance.