Inhibition of the nitrification process in activated sludge by trivalent and hexavalent chromium, and partitioning of hexavalent chromium between sludge compartments

Novotnik, Breda; Zuliani, Tea; Ščančar, Janez; Milačić, Radmila

doi:10.1016/j.chemosphere.2013.12.096

Cited by 28 publications

(17 citation statements)

References 43 publications

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“…And initial concentrations of Cr(VI) were 0.00, 4.32, 8.72 and 25.78 mg g −1 , respectively. Adsorbed, intracellular and intercellular total Cr concentrations and Cr(VI) concentrations in the activated sludge were determined by the methods in SI 2, 14 .…”

Section: Methodsmentioning

confidence: 99%

“…Improper discharge of wastewater from these industries causes Cr contamination 1 . The essentiality and toxicity of Cr depend on its chemical forms 2 . Cr is most frequently observed in trivalent (Cr(III)) and hexavalent (Cr(VI)) forms in natural water 3 .…”

Section: Introductionmentioning

confidence: 99%

“…Cr is most frequently observed in trivalent (Cr(III)) and hexavalent (Cr(VI)) forms in natural water 3 . Cr(VI) (mainly CrO 4 2− at neutral pH or alkaline conditions) has high solubility and bioavailability, and is considered to be mutagenic and carcinogenic, and approximately 100 times more toxic than Cr(III) 2, 4 . Accordingly, almost every regulatory agency worldwide has listed Cr(VI) as a priority toxic chemical 1, 5 .…”

Section: Introductionmentioning

confidence: 99%

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Characterization of Product and Potential Mechanism of Cr(VI) Reduction by Anaerobic Activated Sludge in a Sequencing Batch Reactor

Jin

Liu

et al. 2017

Sci Rep

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Bioremediation of Cr(VI) and nitrate is considered as a promising and cost-effective alternative to chemical and physical methods. However, organo-Cr(III) complexes in effluent generally causes environmental concerns due to second-pollution. Here, Cr(VI) reduction and immobilization efficiencies of anaerobic activated sludge were investigated. Anaerobic activated sludge showed strong reduction ability of Cr(VI) and possessed a great potential of Cr(III) immobilization. Almost 100.0 mg l−1 Cr(VI) could be completely reduced and immobilized by anaerobic activated sludge in a sequencing batch reactor in 24 h. And most generated Cr(III) was accumulated outside of sludge cells. Extracellular polymeric substances (EPS) could bind to Cr(VI) and form EPS-Cr(VI) interaction to reduce the toxic effect of Cr(VI) and promote the Cr(VI) reduction. Protein-like and humic-like substances were responsible for binding with Cr(VI), meanwhile the process was a thermodynamically favorable binding reaction. Then Cr(VI) was reduced to Cr(III) by membrane-associated chromate reductase of sludge. Eventually, the generated Cr(III) might exist as poly-nuclear Cr(III) complexes adhered to sludge surfaces.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Characterization of Product and Potential Mechanism of Cr(VI) Reduction by Anaerobic Activated Sludge in a Sequencing Batch Reactor

Jin

Liu

et al. 2017

Sci Rep

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“…The speciation procedure used in this work is highly selective and sensitive and has successfully been applied for the determination of Cr(VI) in a variety of environmental and biological samples [22,27,37,38]. The limits of detection (LOD) and of quantification (LOQ) for the determination of Cr(VI) at m/z 52 were calculated as the concentration that provides a signal (peak area) equal to 3s and 10s of the blank sample in the chromatogram, respectively.…”

Section: Speciation Of Crmentioning

confidence: 99%

Content of trace elements and chromium speciation in Neem powder and tea infusions

Novotnik

Zuliani

Ščančar

et al. 2015

Journal of Trace Elements in Medicine and Biology

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“…Although a number of studies have revealed effects of Cr(VI) on substrate removal, respiration activity and bacterial growth in activated sludge systems (Cheng et al, 2011;Vaiopoulou and Gikas, 2012;Novotnik et al, 2014), their effects on activated sludge vary in severity and are dependent on a number of confounding factors which frequently hinder clear conclusions. In addition to these unclear results, many questions remain unanswered.…”

Section: Introductionmentioning

confidence: 99%

Nitrification inhibition by hexavalent chromium Cr(VI) – Microbial ecology, gene expression and off-gas emissions

2016

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The goal of this study was to investigate the responses in the physiology, microbial ecology and gene expression of nitrifying bacteria to imposition of and recovery from Cr(VI) loading in a lab-scale nitrification bioreactor. Exposure to Cr(VI) in the reactor strongly inhibited nitrification performance resulting in a parallel decrease in nitrate production and ammonia consumption. Cr(VI) exposure also led to an overall decrease in total bacterial concentrations in the reactor. However, the fraction of ammonia oxidizing bacteria (AOB) decreased to a greater extent than the fraction of nitrite oxidizing bacteria (NOB). In terms of functional gene expression, a rapid decrease in the transcript concentrations of amoA gene coding for ammonia oxidation in AOB was observed in response to the Cr(VI) shock. In contrast, transcript concentrations of the nxrA gene coding for nitrite oxidation in NOB were relatively unchanged compared to Cr(VI) pre-exposure levels. Therefore, Cr(VI) exposure selectively and directly inhibited activity of AOB, which indirectly resulted in substrate (nitrite) limitation to NOB. Significantly, trends in amoA expression preceded performance trends both during imposition of and recovery from inhibition. During recovery from the Cr(VI) shock, the high ammonia concentrations in the bioreactor resulted in an irreversible shift towards AOB populations, which are expected to be more competitive in high ammonia environments. An inadvertent impact during recovery was increased emission of nitrous oxide (N2O) and nitric oxide (NO), consistent with recent findings linking AOB activity and the production of these gases. Therefore, Cr(VI) exposure elicited multiple responses on the microbial ecology, gene expression and both aqueous and gaseous nitrogenous conversion in a nitrification process. A complementary interrogation of these multiple responses facilitated an understanding of both direct and indirect inhibitory impacts on nitrification.

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Inhibition of the nitrification process in activated sludge by trivalent and hexavalent chromium, and partitioning of hexavalent chromium between sludge compartments

Cited by 28 publications

References 43 publications

Characterization of Product and Potential Mechanism of Cr(VI) Reduction by Anaerobic Activated Sludge in a Sequencing Batch Reactor

Characterization of Product and Potential Mechanism of Cr(VI) Reduction by Anaerobic Activated Sludge in a Sequencing Batch Reactor

Content of trace elements and chromium speciation in Neem powder and tea infusions

Nitrification inhibition by hexavalent chromium Cr(VI) – Microbial ecology, gene expression and off-gas emissions

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