Limits...
Analysis of nitrification efficiency and microbial community in a membrane bioreactor fed with low COD/N-ratio wastewater.

Ma J, Wang Z, Zhu C, Liu S, Wang Q, Wu Z - PLoS ONE (2013)

Bottom Line: In this study, an approach using influent COD/N ratio reduction was employed to improve process performance and nitrification efficiency in a membrane bioreactor (MBR).Besides sludge reduction, membrane fouling alleviation was observed during 330 d operation, which was attributed to the decreased production of soluble microbial products (SMP) and efficient carbon metabolism in the autotrophic nitrifying community. 454 high-throughput 16S rRNA gene pyrosequencing revealed that the diversity of microbial sequences was mainly determined by the feed characteristics, and that microbes could derive energy by switching to a more autotrophic metabolism to resist the environmental stress.Further, ammonia oxidation was the rate-limiting step during the full nitrification.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai, PR China.

ABSTRACT
In this study, an approach using influent COD/N ratio reduction was employed to improve process performance and nitrification efficiency in a membrane bioreactor (MBR). Besides sludge reduction, membrane fouling alleviation was observed during 330 d operation, which was attributed to the decreased production of soluble microbial products (SMP) and efficient carbon metabolism in the autotrophic nitrifying community. 454 high-throughput 16S rRNA gene pyrosequencing revealed that the diversity of microbial sequences was mainly determined by the feed characteristics, and that microbes could derive energy by switching to a more autotrophic metabolism to resist the environmental stress. The enrichment of nitrifiers in an MBR with a low COD/N-ratio demonstrated that this condition stimulated nitrification, and that the community distribution of ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) resulted in faster nitrite uptake rates. Further, ammonia oxidation was the rate-limiting step during the full nitrification.

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Variations in rt, biomass concentration, OLR and COD/N ratio during R0 operation.(The inverted open triangle indicates the time point of sludge sampling).
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pone-0063059-g002: Variations in rt, biomass concentration, OLR and COD/N ratio during R0 operation.(The inverted open triangle indicates the time point of sludge sampling).

Mentions: At the beginning of the experimental runs, a period of time intended for biomass acclimation (designated as start-up phase in Phase I) was imposed on R0. The stable biomass concentration of 4.66±0.48 g MLSS/L, 7.09±0.67 g MLSS/L and 14.60±0.59 g MLSS/L was achieved in Phase I, Phase II and Phase III, respectively (Figure 2). Since a large fraction of influent organic carbon was recovered in the upstream process (Table 1), WAS production involved in the treatment of per ton wastewater was decreased by 60–80%. Moreover, with the feeding strategy adopted, in which a low organic loading rate (OLR) was applied to favor the growth of autotrophic microorganisms, it was inferred that a low COD/N ratio would cause a limiting supply of nutrients for microorganism growth, and could result in a low sludge yield. Relevant literature has documented that an autotrophic community could derive energy for growth from the oxidation of ammonium/nitrite [25], resulting in a thinner microcolony structure in bioreactors [7], [13]. In view of this, we calculated the sludge yield coefficient (Y) and decay coefficient (Kd) to evaluate the carbon metabolism in R0. Y and Kd refer to microorganism growth and endogenous respiration. OriginPro 8 (OriginLab Corporation, USA) was applied to process the nonlinear curve fit and the results are shown in Figure S2.


Analysis of nitrification efficiency and microbial community in a membrane bioreactor fed with low COD/N-ratio wastewater.

Ma J, Wang Z, Zhu C, Liu S, Wang Q, Wu Z - PLoS ONE (2013)

Variations in rt, biomass concentration, OLR and COD/N ratio during R0 operation.(The inverted open triangle indicates the time point of sludge sampling).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3646889&req=5

pone-0063059-g002: Variations in rt, biomass concentration, OLR and COD/N ratio during R0 operation.(The inverted open triangle indicates the time point of sludge sampling).
Mentions: At the beginning of the experimental runs, a period of time intended for biomass acclimation (designated as start-up phase in Phase I) was imposed on R0. The stable biomass concentration of 4.66±0.48 g MLSS/L, 7.09±0.67 g MLSS/L and 14.60±0.59 g MLSS/L was achieved in Phase I, Phase II and Phase III, respectively (Figure 2). Since a large fraction of influent organic carbon was recovered in the upstream process (Table 1), WAS production involved in the treatment of per ton wastewater was decreased by 60–80%. Moreover, with the feeding strategy adopted, in which a low organic loading rate (OLR) was applied to favor the growth of autotrophic microorganisms, it was inferred that a low COD/N ratio would cause a limiting supply of nutrients for microorganism growth, and could result in a low sludge yield. Relevant literature has documented that an autotrophic community could derive energy for growth from the oxidation of ammonium/nitrite [25], resulting in a thinner microcolony structure in bioreactors [7], [13]. In view of this, we calculated the sludge yield coefficient (Y) and decay coefficient (Kd) to evaluate the carbon metabolism in R0. Y and Kd refer to microorganism growth and endogenous respiration. OriginPro 8 (OriginLab Corporation, USA) was applied to process the nonlinear curve fit and the results are shown in Figure S2.

Bottom Line: In this study, an approach using influent COD/N ratio reduction was employed to improve process performance and nitrification efficiency in a membrane bioreactor (MBR).Besides sludge reduction, membrane fouling alleviation was observed during 330 d operation, which was attributed to the decreased production of soluble microbial products (SMP) and efficient carbon metabolism in the autotrophic nitrifying community. 454 high-throughput 16S rRNA gene pyrosequencing revealed that the diversity of microbial sequences was mainly determined by the feed characteristics, and that microbes could derive energy by switching to a more autotrophic metabolism to resist the environmental stress.Further, ammonia oxidation was the rate-limiting step during the full nitrification.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai, PR China.

ABSTRACT
In this study, an approach using influent COD/N ratio reduction was employed to improve process performance and nitrification efficiency in a membrane bioreactor (MBR). Besides sludge reduction, membrane fouling alleviation was observed during 330 d operation, which was attributed to the decreased production of soluble microbial products (SMP) and efficient carbon metabolism in the autotrophic nitrifying community. 454 high-throughput 16S rRNA gene pyrosequencing revealed that the diversity of microbial sequences was mainly determined by the feed characteristics, and that microbes could derive energy by switching to a more autotrophic metabolism to resist the environmental stress. The enrichment of nitrifiers in an MBR with a low COD/N-ratio demonstrated that this condition stimulated nitrification, and that the community distribution of ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) resulted in faster nitrite uptake rates. Further, ammonia oxidation was the rate-limiting step during the full nitrification.

Show MeSH
Related in: MedlinePlus