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Use of in-vitro experimental results to model in-situ experiments: bio-denitrification under geological disposal conditions.

Masuda K, Murakami H, Kurimoto Y, Kato O, Kato K, Honda A - Springerplus (2013)

Bottom Line: Among them, reduction by metal compounds and microorganisms seems to be important in the underground repository.Nitrates were reduced almost to N2 gas in the existence of super plasticizer.In the case of humic acids, although nitrates were reduced, the rate was much lower and, in this case, dead organism was used as an electron donor instead of humic acids.

View Article: PubMed Central - PubMed

Affiliation: Kobelco Research Institute Inc, 1-5-5, Takatsuka-dai, Nishi-ku, Kobe, Hyogo, Japan.

ABSTRACT
Some of the low level radioactive wastes from reprocessing of spent nuclear fuels contain nitrates. Nitrates can be present in the form of soluble salts and can be reduced by various reactions. Among them, reduction by metal compounds and microorganisms seems to be important in the underground repository. Reduction by microorganism is more important in near field area than inside the repository because high pH and extremely high salt concentration would prevent microorganism activities. In the near field, pH is more moderate (pH is around 8) and salt concentration is lower. However, the electron donor may be limited there and it might be the control factor for microorganism's denitrification activities. In this study, in-vitro experiments of the nitrate reduction reaction were conducted using model organic materials purported to exist in underground conditions relevant to geological disposal. Two kinds of organic materials were selected. A super plasticizer was selected as being representative of the geological disposal system and humic acid was selected as being representative of pre-existing organic materials in the bedrock. Nitrates were reduced almost to N2 gas in the existence of super plasticizer. In the case of humic acids, although nitrates were reduced, the rate was much lower and, in this case, dead organism was used as an electron donor instead of humic acids. A reaction model was developed based on the in-vitro experiments and verified by running simulations against data obtained from in-situ experiments using actual groundwaters and microorganisms. The simulation showed a good correlation with the experimental data and contributes to the understanding of microbially mediated denitrification in geological disposal systems.

No MeSH data available.


Related in: MedlinePlus

Comparison of humic acid and super plasticizer as an electron donor from the viewpoint of nitrate utilization with activated sludge as microorganism. Run 2 (shown as black circles and solid line) was carried out with super plasticizer and Run 3–7 (shown as dotted lines) were carried out with humic acids under the conditions shown in the Table 1. Lines are shown to help identify the general trends shown by the data.
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Fig4: Comparison of humic acid and super plasticizer as an electron donor from the viewpoint of nitrate utilization with activated sludge as microorganism. Run 2 (shown as black circles and solid line) was carried out with super plasticizer and Run 3–7 (shown as dotted lines) were carried out with humic acids under the conditions shown in the Table 1. Lines are shown to help identify the general trends shown by the data.

Mentions: In series B (Runs 3–7), humic acids were used as electron donors with activated sludge as the microorganism. Ampule tests were carried out in Run 3 and Run 4 with changes in the initial NO3– concentration, while vial tests were carried out in Run 5–7 to investigate temporal changes. The nitrogen balance in Run 3 and 4 (Figure 3) shows that the main reaction is the reduction of NO3– to N2 in the case of the humic acids; as was found for the super plasticizers (Figure 2). Comparison of the NO3– reduction rate in the presence of humic acid with super plasticizers (Figure 4) demonstrates that the amount of NO3– reduced in any of Runs 5–7 was much lower than that of Run 2. Furthermore, there was no dependence of NO3– reduction rate on the initial NO3– concentration (Figure 4).Figure 3


Use of in-vitro experimental results to model in-situ experiments: bio-denitrification under geological disposal conditions.

Masuda K, Murakami H, Kurimoto Y, Kato O, Kato K, Honda A - Springerplus (2013)

Comparison of humic acid and super plasticizer as an electron donor from the viewpoint of nitrate utilization with activated sludge as microorganism. Run 2 (shown as black circles and solid line) was carried out with super plasticizer and Run 3–7 (shown as dotted lines) were carried out with humic acids under the conditions shown in the Table 1. Lines are shown to help identify the general trends shown by the data.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3755790&req=5

Fig4: Comparison of humic acid and super plasticizer as an electron donor from the viewpoint of nitrate utilization with activated sludge as microorganism. Run 2 (shown as black circles and solid line) was carried out with super plasticizer and Run 3–7 (shown as dotted lines) were carried out with humic acids under the conditions shown in the Table 1. Lines are shown to help identify the general trends shown by the data.
Mentions: In series B (Runs 3–7), humic acids were used as electron donors with activated sludge as the microorganism. Ampule tests were carried out in Run 3 and Run 4 with changes in the initial NO3– concentration, while vial tests were carried out in Run 5–7 to investigate temporal changes. The nitrogen balance in Run 3 and 4 (Figure 3) shows that the main reaction is the reduction of NO3– to N2 in the case of the humic acids; as was found for the super plasticizers (Figure 2). Comparison of the NO3– reduction rate in the presence of humic acid with super plasticizers (Figure 4) demonstrates that the amount of NO3– reduced in any of Runs 5–7 was much lower than that of Run 2. Furthermore, there was no dependence of NO3– reduction rate on the initial NO3– concentration (Figure 4).Figure 3

Bottom Line: Among them, reduction by metal compounds and microorganisms seems to be important in the underground repository.Nitrates were reduced almost to N2 gas in the existence of super plasticizer.In the case of humic acids, although nitrates were reduced, the rate was much lower and, in this case, dead organism was used as an electron donor instead of humic acids.

View Article: PubMed Central - PubMed

Affiliation: Kobelco Research Institute Inc, 1-5-5, Takatsuka-dai, Nishi-ku, Kobe, Hyogo, Japan.

ABSTRACT
Some of the low level radioactive wastes from reprocessing of spent nuclear fuels contain nitrates. Nitrates can be present in the form of soluble salts and can be reduced by various reactions. Among them, reduction by metal compounds and microorganisms seems to be important in the underground repository. Reduction by microorganism is more important in near field area than inside the repository because high pH and extremely high salt concentration would prevent microorganism activities. In the near field, pH is more moderate (pH is around 8) and salt concentration is lower. However, the electron donor may be limited there and it might be the control factor for microorganism's denitrification activities. In this study, in-vitro experiments of the nitrate reduction reaction were conducted using model organic materials purported to exist in underground conditions relevant to geological disposal. Two kinds of organic materials were selected. A super plasticizer was selected as being representative of the geological disposal system and humic acid was selected as being representative of pre-existing organic materials in the bedrock. Nitrates were reduced almost to N2 gas in the existence of super plasticizer. In the case of humic acids, although nitrates were reduced, the rate was much lower and, in this case, dead organism was used as an electron donor instead of humic acids. A reaction model was developed based on the in-vitro experiments and verified by running simulations against data obtained from in-situ experiments using actual groundwaters and microorganisms. The simulation showed a good correlation with the experimental data and contributes to the understanding of microbially mediated denitrification in geological disposal systems.

No MeSH data available.


Related in: MedlinePlus