Evaluation of nitrate and perchlorate reduction using sulfur-based autotrophic and mixotrophic denitrifying processes

2015 ◽  
Vol 16 (1) ◽  
pp. 208-218 ◽  
Author(s):  
Deniz Uçar ◽  
Emine Ubay Çokgör ◽  
Erkan Şahinkaya
Keyword(s):  
Nitrate Reduction ◽  
Elemental Sulfur ◽  
Reduction Rate ◽  
Sulfate Concentration ◽  
Biological Reduction ◽  
Perchlorate Reduction ◽  
Guideline Value ◽  
Reduction Efficiency ◽  
Drinking Water Guideline ◽  
Denitrification Process

The biological reduction of nitrate and perchlorate was comparatively evaluated in autotrophic and mixotrophic bioreactors using elemental sulfur and/or methanol as the energy source. The mixotrophic reactor was supplemented with methanol at CH3OH/NO3−-N ratio of 1 or 1.4. The mixotrophic reactor completely reduced perchlorate in the feed up to 1,000 μg l−1. The autotrophic reactor also showed high perchlorate reduction performance and decreased perchlorate from 1,000 μg l−1 to around 33 μg l−1. Complete reduction of 25 mg NO3−-N l−1 was achieved in both reactors, corresponding to a maximum nitrate reduction rate of 300 mg NO3−-N l−1d−1 and 400 mg NO3−-N l−1d−1 in the autotrophic and mixotrophic processes, respectively. Autotrophic denitrification caused an increase of effluent sulfate concentration, which may exceed the drinking water guideline value of 250 mg l−1. In the mixotrophic denitrification process, the effluent sulfate concentration was controlled by adjusting the C/N ratio in the influent. Mixotrophic denitrification was stimulated by 25 mg l−1 methanol addition and 53% of influent nitrate was reduced by the heterotrophic process, which decreased the effluent sulfate concentration to half of the autotrophic counterpart. Therefore, the mixotrophic process may be preferred over the autotrophic process when effluent sulfate concentration is of concern and a higher perchlorate reduction efficiency is desired.

Inhibition of nitrate and the accumulated denitrification intermediate (nitrite) on perchlorate bioreduction

2014 ◽  
Vol 49 (4) ◽  
pp. 346-353 ◽  
Author(s):  
Rui Wang ◽  
Liang Chen ◽  
Fei Liu ◽  
Hong H. Chen ◽  
Jia W. Zhang ◽  
...  
Keyword(s):  
Reduction Rate ◽  
Environmentally Friendly ◽  
Critical Factor ◽  
Efficient Technology ◽  
Treatment Technology ◽  
Batch Type ◽  
Perchlorate Reduction ◽  
Negative Effect ◽  
Lag Period ◽  
Denitrification Process

Bioreduction of perchlorate and nitrate by perchlorate-reducing microorganisms (PRMs) is an environmentally friendly, economic, and efficient technology to treat mixed plumes composed of these substances. The influence of perchlorate, nitrate, and denitrification intermediates on PRM activity is a critical factor, which may affect the efficiency of treatment technology. This study investigated the inhibition of nitrate and the intermediate (nitrite) accumulated during the denitrification process on perchlorate bioreduction via a batch-type experiment. From the experiment, it was found that perchlorate had no effect on the denitrification process and that the reduction rate of perchlorate could be improved when NO3−-N/ClO4− ≤1.2. However, a negative effect of nitrate on perchlorate reduction was observed when NO3−-N/ClO4− >1.2 with an accumulation of 18.0 mg NO2−-N /L. This negative effect increased with the concentration of nitrate. Moreover, nitrite from the denitrification process had a similar negative effect on perchlorate reduction. Bioreduction of perchlorate was not started until nitrite was totally reduced, and a 2–13 day lag period was observed for perchlorate reduction after nitrite depletion.

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.

Microbial Perchlorate Reduction in Groundwater with Different Electron Donors

2013 ◽  
Vol 295-298 ◽  
pp. 1402-1407
Author(s):  
Rui Wang ◽  
Ming Chen ◽  
Jia Wen Zhang ◽  
Fei Liu ◽  
Hong Han Chen
Keyword(s):  
Removal Efficiency ◽  
Electron Donor ◽  
Electron Acceptor ◽  
Reduction Rate ◽  
Electron Donors ◽  
Monod Equation ◽  
Hydrogen Addition ◽  
Perchlorate Reduction ◽  
Perchlorate Removal

Effects of different electron donors (acetate and hydrogen), acetate and perchlorate concentrations on microbial perchlorate reduction in groundwater were studied. The results showed that acetate and hydrogen addition as an electron donor can significantly improve perchlorate removal efficiency while a longer period was observed for hydrogen (15 d) than for acetate (8 d). The optical ratio of electron donor (acetate)-to-electron acceptor (perchlorate) was approximately 1.65 mg COD mg perchlorate-1. The highest specific reduction rate of perchlorate was achieved at the acetate-to-perchlorate ratio of 3.80 mg COD mg perchlorate-1. The perchlorate reduction rates corresponded well to the theoretical values calculated by the Monod equation and the parameters of Ks and Vm were determined to be 15.6 mg L-1 and 0.26 d-1, respectively.

Assessing the Impacts of Future Climate Conditions on the Effectiveness of Winter Cover Crops in Reducing Nitrate Loads into the Chesapeake Bay Watersheds Using the SWAT Model

2017 ◽  
Vol 60 (6) ◽  
pp. 1939-1955 ◽  
Author(s):  
Sangchul Lee ◽  
Ali M. Sadeghi ◽  
In-Young Yeo ◽  
Gregory W. McCarty ◽  
W. Dean Hively
Keyword(s):  
Coastal Plain ◽  
Cover Crops ◽  
Nitrate Reduction ◽  
Future Climate ◽  
Baseline Scenario ◽  
Climate Conditions ◽  
Reduction Efficiency ◽  
Simulation Results ◽  
Winter Cover ◽  
Winter Cover Crops

Abstract. Winter cover crops (WCCs) have been widely implemented in the Coastal Plain of the Chesapeake Bay Watershed (CBW) due to their high effectiveness in reducing nitrate loads. However, future climate conditions (FCCs) are expected to exacerbate water quality degradation in the CBW by increasing nitrate loads from agriculture. Accordingly, the question remains whether WCCs are sufficient to mitigate increased nutrient loads caused by FCCs. In this study, we assessed the impacts of FCCs on WCC nitrate reduction efficiency in the Coastal Plain of the CBW using the Soil and Water Assessment Tool (SWAT). Three FCC scenarios (2085-2098) were prepared using general circulation models (GCMs), considering three Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) greenhouse gas emission scenarios. We also developed six representative WCC implementation scenarios based on the most commonly used planting dates and species of WCCs in this region. Simulation results showed that WCC biomass increased by ~58% under FCC scenarios due to climate conditions conducive to WCC growth. Prior to implementing WCCs, annual nitrate loads increased by ~43% under FCC scenarios compared to the baseline scenario (2001-2014). When WCCs were planted, annual nitrate loads were substantially reduced by ~48%, and WCC nitrate reduction efficiency was ~5% higher under FCC scenarios relative to the baseline scenario. The increase in WCC nitrate reduction efficiency varied with FCC scenario and WCC planting method. As CO2 concentrations were higher and winters were warmer under FCC scenarios, WCCs had greater biomass and thus demonstrated higher nitrate reduction efficiency. In response to FCC scenarios, the performance of less effective WCC practices (i.e., barley, wheat, and late planting) under the baseline scenario indicated a ~14% higher increase in nitrate reduction efficiency compared to WCC practices with greater effectiveness under the baseline scenario (i.e., rye and early planting) due to warmer temperatures. The SWAT simulation results indicated that WCCs were effective in mitigating nitrate loads accelerated by FCCs, suggesting the role of WCCs in mitigating nitrate loads will likely be even more important under FCCs. Keywords: Future climate conditions (FCCs), SWAT, Water quality, Winter cover crops (WCCs).

scholarly journals Electrochemical Removal of Chromium (VI) from Wastewater

2019 ◽  
Author(s):  
Hao Peng ◽  
Yumeng Leng ◽  
Jing Guo
Keyword(s):  
Reaction Temperature ◽  
Current Density ◽  
Reduction Rate ◽  
Reduction Process ◽  
Order Equation ◽  
First Order ◽  
Chromium Vi ◽  
Reduction Efficiency ◽  
Pseudo First Order ◽  
Electrochemical Removal

Removal of hexavalent chromium had attracted much more attention as it was a hazardous contaminant. Electrochemical reduction technology was applied to removal chromium (VI) from wastewater. The mechanism and parameters affect the reduction process were investigated. The results showed that the reduction efficiency was significantly affected by the concentration of H2SO4, current density and reaction temperature. And the reduction efficiency was up to 86.45% at concentration of H2SO4 of 100g/L, reaction temperature of 70 ℃, current density at 50 A/m2, reaction time at 180 min and stirring rate of 500 rpm. The reduction process of chromium (VI) was followed pseudo-first-order equation, and the reduction rate could be expressed as Kobs = k [H2SO4]1• [j] 4•exp-4170/RT.

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.

scholarly journals Groundwater cable bacteria conserve energy by sulfur disproportionation

2019 ◽  
Vol 14 (2) ◽  
pp. 623-634 ◽  
Author(s):  
Hubert Müller ◽  
Sviatlana Marozava ◽  
Alexander J. Probst ◽  
Rainer U. Meckenstock
Keyword(s):  
16S Rrna ◽  
Electron Donor ◽  
Nitrate Reduction ◽  
Elemental Sulfur ◽  
Single Cells ◽  
Sulfur Oxidation ◽  
Metabolic Reconstruction ◽  
Rrna Gene ◽  
Long Distance ◽  
Sulfur Disproportionation

AbstractCable bacteria of the family Desulfobulbaceae couple spatially separated sulfur oxidation and oxygen or nitrate reduction by long-distance electron transfer, which can constitute the dominant sulfur oxidation process in shallow sediments. However, it remains unknown how cells in the anoxic part of the centimeter-long filaments conserve energy. We found 16S rRNA gene sequences similar to groundwater cable bacteria in a 1-methylnaphthalene-degrading culture (1MN). Cultivation with elemental sulfur and thiosulfate with ferrihydrite or nitrate as electron acceptors resulted in a first cable bacteria enrichment culture dominated >90% by 16S rRNA sequences belonging to the Desulfobulbaceae. Desulfobulbaceae-specific fluorescence in situ hybridization (FISH) unveiled single cells and filaments of up to several hundred micrometers length to belong to the same species. The Desulfobulbaceae filaments also showed the distinctive cable bacteria morphology with their continuous ridge pattern as revealed by atomic force microscopy. The cable bacteria grew with nitrate as electron acceptor and elemental sulfur and thiosulfate as electron donor, but also by sulfur disproportionation when Fe(Cl)2 or Fe(OH)3 were present as sulfide scavengers. Metabolic reconstruction based on the first nearly complete genome of groundwater cable bacteria revealed the potential for sulfur disproportionation and a chemo-litho-autotrophic metabolism. The presence of different types of hydrogenases in the genome suggests that they can utilize hydrogen as alternative electron donor. Our results imply that cable bacteria not only use sulfide oxidation coupled to oxygen or nitrate reduction by LDET for energy conservation, but sulfur disproportionation might constitute the energy metabolism for cells in large parts of the cable bacterial filaments.

scholarly journals Tailoring Carbon Nanotubes to Enhance their Efficiency as Electron Shuttle on the Biological Removal of Acid Orange 10 Under Anaerobic Conditions

Nanomaterials ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2496
Author(s):  
Ana Rita Silva ◽  
O. Salomé G.P. Soares ◽  
M. Fernando R. Pereira ◽  
M. Madalena Alves ◽  
Luciana Pereira
Keyword(s):  
Carbon Nanotubes ◽  
Methane Production ◽  
Carbon Nanomaterials ◽  
Reduction Rate ◽  
Granular Sludge ◽  
Biological Reduction ◽  
Methanogenic Activity ◽  
Acid Orange ◽  
Biological Removal ◽  
Acid Orange 10

Anaerobic treatments have been described for the biodegradation of pollutants. However, the reactions proceed slowly due to the recalcitrant nature of these compounds. Carbon nanomaterials (CNM) intermediate in, and favor, the electron transfer, accelerating the anaerobic reduction of pollutants, which act as final electron acceptors. In the present work, different carbon nanotubes (CNT) with modified surface chemistry, namely CNT oxidized with HNO3 (CNT_HNO3) and CNT doped with nitrogen in a ball milling process (CNT_N_MB) were prepared using commercial CNT as a starting material. The new CNM were tested as redox mediators (RM), 0.1 g L−1, in the biological reduction of the azo dye, Acid Orange 10 (AO10), with an anaerobic granular sludge, over 48 h of reaction. Methane production was also assessed to verify the microorganism’s activity and the CNM’s effect on the methanogenic activity. An improvement in the biological removal of AO10 occurred with all CNM (above 90%), when compared with the control without CNM (only 32.4 ± 0.3%). The best results were obtained with CNT_N_MB, which achieved 98.2 ± 0.1% biological AO10 removal, and an 11-fold reduction rate increase. In order to confer magnetic properties to the CNM, tailored CNT were impregnated with 2% of iron-samples: CNT@2%Fe, CNT@2%Fe_N_MB, and CNT@2%Fe_HNO3. The better performance of the CNT doped with nitrogen was confirmed with CNT@2%Fe_N_MB, and the magnetic character facilitated its recovery after treatment, and did not affect its good catalytic properties. No dye removal was observed in the abiotic assays, so the removal was not due to adsorption on the CNM. Furthermore, the microorganism’s viability was maintained during the assay and methane production was not affected by the presence of the CNM. Despite the toxic character of the aromatic amines formed, detoxification was observed after the biological process with thermally treated CNT.

scholarly journals Simultaneous Biological and Chemical Removal of Sulfate and Fe(II)EDTA-NO in Anaerobic Conditions and Regulation of Sulfate Reduction Products

Minerals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 330 ◽  
Author(s):  
Yu Zhang ◽  
Lijian Sun ◽  
Jiti Zhou
Keyword(s):  
Sulfate Reduction ◽  
Flue Gas ◽  
Elemental Sulfur ◽  
Biofilm Reactor ◽  
Flue Gas Desulfurization ◽  
Moving Bed Biofilm Reactor ◽  
Anaerobic Conditions ◽  
Biological Reduction ◽  
Sulfate Reducing ◽  
Reducing Bacteria

In the simultaneous flue gas desulfurization and denitrification by biological combined with chelating absorption technology, SO2 and NO are converted into sulfate and Fe(II)EDTA-NO which need to be reduced in biological reactor. Increasing the removal loads of sulfate and Fe(II)EDTA-NO and converting sulfate to elemental sulfur will benefit the application of this process. A moving-bed biofilm reactor was adopted for sulfate and Fe(II)EDTA-NO biological reduction. The removal efficiencies of the sulfate and Fe(II)EDTA-NO were 96% and 92% with the influent loads of 2.88 kg SO42−·m−3·d−1 and 0.48 kg NO·m−3·d−1. The sulfide produced by sulfate reduction could be reduced by increasing the concentrations of Fe(II)EDTA-NO and Fe(III)EDTA. The main reduction products of sulfate and Fe(II)EDTA-NO were elemental sulfur and N2. It was found that the dominant strain of sulfate reducing bacteria in the system was Desulfomicrobium. Pseudomonas, Sulfurovum and Arcobacter were involved in the reduction of Fe(II)EDTA-NO.

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