Performance of a new suspended filler biofilter for removal of nitrogen oxides under thermophilic conditions and microbial community analysis

Abstract

A suspended biofilter, as a new bioreactor, was constructed for the removal of nitrogen oxides (NOX) from simulated flue gas under thermophilic conditions. The suspended biofilter could be quickly started up by inoculating the thermophilic denitrifying bacterium Chelatococcus daeguensis TAD1. The NO concentration in the inlet stream ranged from 200mg/m(3) to 2000mg/m(3) during the operation, and inlet loading ranged from 8.2-164g/(m(3)·h). The whole operation period was divided into four phases according to the EBRT. The EBRT of phases I, II, III and IV were 88s (9-43d), 44s (44-61d), 66s (62-79d) and 132s (80-97d), respectively. An average NO removal efficiency of 90% was achieved during the whole operation period, and the elimination capacity increased linearly with the increase in NO inlet loading and the maximum elimination capacity reached 146.9g/(m(3)·h). No clogging was observed, although there was a high biomass concentration in the biofilter bed. The remarkable performance in terms of NO removal could be attributed to the rich bacterial communities. The microbial community structure in the biofilm was investigated by high throughput sequencing analysis (16S rRNA MiSeq sequencing). The experimental results showed that the microbial community structure of the biofilm was very rich in diversity, with the most abundant bacterial class of the Alphaproteobacteria, which accounted for 36.5% of the total bacteria, followed by Gammaproteobacteria (30.7%) and Clostridia (27.5%). It was worthwhile to mention that the dominant species in the suspended biofilter biofilm were all common denitrifying bacteria including Rhizobiales (inoculated microbe), Rhodospirillales, Enterobacteriales and Pseudomonadales, which accounted for 19.4%, 17%, 21.6% and 7%, respectively. The inoculated strain TAD1 belonged to Alphaproteobacteria class. Because high-throughput 16S rRNA gene paired-end sequencing has improved resolution of bacterial community analysis, 16S rRNA gene sequencing of these bacteria could provide more functional and phylogenetic information about the bacterial communities.

Keywords: 16S rRNA MiSeq sequencing; NO removal; Suspended biofilter; Thermophilic denitrifying bacterium.