Mitigating nitrite inhibition in Klebsiella strain denitrification: Stimulating endogenous driving force with microscale zero-valent iron
[Display omitted] •Higher mZVI dosages shifted nitrogen distribution from NO2–-N to gaseous forms.•Achieved 76.5% total nitrogen removal with the addition of mZVI.•NO2–-N was more readily transformed than NO3–-N with mZVI.•Addition of mZVI reduced the activation energy for NO2–-N transformation by 7...
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Veröffentlicht in: | Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2024-10, Vol.498, p.155501, Article 155501 |
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Sprache: | eng |
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•Higher mZVI dosages shifted nitrogen distribution from NO2–-N to gaseous forms.•Achieved 76.5% total nitrogen removal with the addition of mZVI.•NO2–-N was more readily transformed than NO3–-N with mZVI.•Addition of mZVI reduced the activation energy for NO2–-N transformation by 72%.•Nir activity was twice as high with mZVI (0.31 μg NO2–-N min−1 mg−1 protein).
This study investigates the denitrification characteristics facilitated by microscale zero-valent iron (mZVI) in conjunction with Klebsiella oxytoca. While Klebsiella oxytoca effectively degrades both nitrate (NO3–-N) and nitrite (NO2–-N) on its own, the presence of mZVI significantly enhances NO2–-N elimination, highlighting mZVI’s facilitative role in denitrification. Optimal performance is observed at an mZVI concentration of 1.0 g/L, enabling complete biotic reduction of both NO3–-N and NO2–-N, particularly at an initial NO3–-N concentration of 50 mg/L and a C/N ratio of 16. mZVI promotes the conversion of NO2–-N to gaseous nitrogen, with this effect becoming more pronounced at higher mZVI doses. Inhibitory kinetics experiments demonstrate mZVI’s ability to mitigate NO2–-N inhibition on microorganisms. Thermodynamic and electrochemical analyses reveal that mZVI enhances NO2–-N reduction through mechanisms involving Fe(II)/Fe(III) electron pair generation, as well as the secretion of extracellular polymeric substances and flavins. Genetic abundance and enzyme activity analyses further confirm mZVI’s pivotal role in enhancing denitrification efficiency and elucidating its underlying mechanisms. |
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ISSN: | 1385-8947 |
DOI: | 10.1016/j.cej.2024.155501 |