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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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Venn of the bacterial communities of R0vs R1, R0vs R4 and R0vs R5 based on OTU (3% distance), and the taxonomic identities of the shared and unique OTUs at the phylum level (Phyla percentages below 1.0% are not shown).R0–U, R1–U, R4–U and R5–U represent the unique R0, R1, R4 and R5 communities, and R0–R1, R0–R4 and R0–R5 refer to shared communities.
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pone-0063059-g004: Venn of the bacterial communities of R0vs R1, R0vs R4 and R0vs R5 based on OTU (3% distance), and the taxonomic identities of the shared and unique OTUs at the phylum level (Phyla percentages below 1.0% are not shown).R0–U, R1–U, R4–U and R5–U represent the unique R0, R1, R4 and R5 communities, and R0–R1, R0–R4 and R0–R5 refer to shared communities.

Mentions: In contrast to the typical heterotrophic environment, a shift of an MBR from a copiotrophic (e.g. R1) to an oligotrophic environment (R0) did not increase the diversity of the community, although nitrification stimulation was observed [21]. However, the microbes present in an MBR could derive energy by switching to a more autotrophic metabolism to resist the environmental stress [25]. The total observed OTUs in the R0 and R1 communities was 2256, with 309 OTUs, or 13.7% of the total, shared by them (Figure 4). Of the 18 identified phyla, Proteobacteria, Bacteroidetes and No_Rank bacteria accounted for the majority of the unique community composition in R0 (55.0%, 15.2% and 11.7%) and R1 (50.4%, 14.9% and 12.6%), respectively. Notably, although the organic matter in the influent of R0 was lower, the heterotrophic bacteria were still dominant over the autotrophic bacteria, as documented previously [31]. Despite the fact that the population composition of R0–U, R0–R1 and R1–U were not significantly different at the 0.05 level (p = 0.99985), a marked decrease in the phototropic bacteria in R0 was observed compared with R1, suggesting more favorable conditions for the growth of the nitrifiers (Figure 4). By contrast, the shared OTUs ratio with R0 was decreased by 27.0% with the influent COD/N-ratio increased from 10.0±4.2 (R1) to 60.5±13.9 (R4). The clearest difference between the unique communities of R0 and R4 was the different distribution of phyla Proteobacteria, Chlorobi, Chloroflexi and Nitrospirae in Z2, Z3 and Z5 in Figure 3. Autotrophic bacteria in phyla Proteobacteria and Nitrospirae may be depleted in R4 under such a copiotrophic environment. Although the influent COD/N ratio was also about 10 in R5, its community structure was quite different from the other MBRs’ (Figure 3). Racz has reported that not only the quantity but also the source of the organic carbon affected the make-up of the heterotroph community as well as AOB in mixed cultures [3]. The phyla Chloroflexi (9.5%), Firmicutes (4.4%) and Planctomycetes (10.5%) referring to polysaccharide degradation [32], anaerobic fermentation [21] and sulfated polymeric carbon utilization in the marine environment [33] were enriched in the R5 community (Figure 4), suggesting a versatile bio-metabolism of the inert component in the leachate.


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)

Venn of the bacterial communities of R0vs R1, R0vs R4 and R0vs R5 based on OTU (3% distance), and the taxonomic identities of the shared and unique OTUs at the phylum level (Phyla percentages below 1.0% are not shown).R0–U, R1–U, R4–U and R5–U represent the unique R0, R1, R4 and R5 communities, and R0–R1, R0–R4 and R0–R5 refer to shared communities.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0063059-g004: Venn of the bacterial communities of R0vs R1, R0vs R4 and R0vs R5 based on OTU (3% distance), and the taxonomic identities of the shared and unique OTUs at the phylum level (Phyla percentages below 1.0% are not shown).R0–U, R1–U, R4–U and R5–U represent the unique R0, R1, R4 and R5 communities, and R0–R1, R0–R4 and R0–R5 refer to shared communities.
Mentions: In contrast to the typical heterotrophic environment, a shift of an MBR from a copiotrophic (e.g. R1) to an oligotrophic environment (R0) did not increase the diversity of the community, although nitrification stimulation was observed [21]. However, the microbes present in an MBR could derive energy by switching to a more autotrophic metabolism to resist the environmental stress [25]. The total observed OTUs in the R0 and R1 communities was 2256, with 309 OTUs, or 13.7% of the total, shared by them (Figure 4). Of the 18 identified phyla, Proteobacteria, Bacteroidetes and No_Rank bacteria accounted for the majority of the unique community composition in R0 (55.0%, 15.2% and 11.7%) and R1 (50.4%, 14.9% and 12.6%), respectively. Notably, although the organic matter in the influent of R0 was lower, the heterotrophic bacteria were still dominant over the autotrophic bacteria, as documented previously [31]. Despite the fact that the population composition of R0–U, R0–R1 and R1–U were not significantly different at the 0.05 level (p = 0.99985), a marked decrease in the phototropic bacteria in R0 was observed compared with R1, suggesting more favorable conditions for the growth of the nitrifiers (Figure 4). By contrast, the shared OTUs ratio with R0 was decreased by 27.0% with the influent COD/N-ratio increased from 10.0±4.2 (R1) to 60.5±13.9 (R4). The clearest difference between the unique communities of R0 and R4 was the different distribution of phyla Proteobacteria, Chlorobi, Chloroflexi and Nitrospirae in Z2, Z3 and Z5 in Figure 3. Autotrophic bacteria in phyla Proteobacteria and Nitrospirae may be depleted in R4 under such a copiotrophic environment. Although the influent COD/N ratio was also about 10 in R5, its community structure was quite different from the other MBRs’ (Figure 3). Racz has reported that not only the quantity but also the source of the organic carbon affected the make-up of the heterotroph community as well as AOB in mixed cultures [3]. The phyla Chloroflexi (9.5%), Firmicutes (4.4%) and Planctomycetes (10.5%) referring to polysaccharide degradation [32], anaerobic fermentation [21] and sulfated polymeric carbon utilization in the marine environment [33] were enriched in the R5 community (Figure 4), suggesting a versatile bio-metabolism of the inert component in the leachate.

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