Analysis of Bacterial Communities in Partial Nitritation and Conventional Nitrification Systems for Nitrogen Removal

Abstract

This work studied the microbial community in partial nitritation and complete nitrification processes, which were applied to treat the low Carbon Nitrogen ratio wastewater. The phospholipid fatty acid and quantitative PCR analysis showed that the sludge circulating ratio of 75% resulted in a good microbial growth and a higher abundance of ammonia oxidizing bacteria relative to the nitrite oxidizing bacteria. The Betaproteobacteria were observed to compose the most abundant sludge bacterial groups in the two processes, based on phylogenetic analysis. The phylogenetic analysis of both 16S rRNA and amoA gene indicated that the Nitrosomonas sp. were the dominant ammonia oxidizing bacteria in the partial nitritation process. The relative abundance of nitrite oxidizing bacteria, such as Nitrobacter sp. and Nitrospira sp., were significantly lower in the partial nitritation system over the complete nitrification system. The abundance of Planctomycetes was higher in the partial nitritation process, indicating the anammox reaction occurred in the partial nitritation system. These results suggested the nitrite accumulation rate of circulating ratios 75% was the highest, with an average of 92%,and a possibility to treat the low Carbon Nitrogen ratio wastewater using the partial nitritation/anammox process.

Figure 1

The concentrations of phospholipid fatty acids (PLFA) in sludge during the partial nitritation process. The error bars are the standard deviations (n = 3).

Figure 2

The quantity of amoA gene for AOB and NOB in activated sludge in the partial nitritation process. The number of the amoA gene copies was normalized as the Log10 number per 1 gram sludge. The error bars are the standard deviations (n = 3). The columns under different letters (ab, a, b) are significantly different at p < 0.05 (t test).

Figure 3

Rarefaction analysis of 16S rRNA gene clone library. Which the rarefaction using Rarefactwin Version 1.3 software.

Figure 4

The phylogenetic tree of the 16S rRNA sequences in the complete nitrification process. The construction of the phylogenetic tree was based on the Neighbour-joining method. The scale bar indicates two changes per 1000 nucleic acid positions.

Figure 5

The phylogenetic tree of the 16S rRNA sequences in the partial nitritation process. The constrction of the phylogenetic tree was based on the Neighbour-joining method. The scale bar indicates two changes per 1000 nucleic acid positions.

Figure 6

The bacterial community in activated sludge in the partial nitritation process and complete nitrification process.

Figure 7

The phylogenetic tree of amoA gene sequences in the partial nitritation process. The construction of the phylogenetic tree was based on the Neighbour-joining method. The scale bar indicates two changes per 1000 nucleic acid positions.

Figure 8

The schematic drawing of the baffled reactor used in this study.