Characterization of Tobermolite as a Bed Material for Selective Growth of Methanotrophs in Biofiltration

Tobermolite was characterized as a bed material for methanotrophic biofiltration. A lab-scale biofilter packed with tobermolite was operated with different operation times under the identical condition. Three different runs showed a similar acclimation pattern of methane oxidation that methane removal efficiency increased rapidly for the first few days and peaked within three weeks, after which remained stable. The mean methane removal capacities ranged from 766 to 974 g•m-3•d-1 after the acclimation. Pyrosequencing indicated that methanotrophic proportion (methanotroph/bacteria) increased to 71-94% within three weeks, then gradually decreased over time. The type I methanotrophs Methylocaldum and Methylosarcina were dominant at the initial growth period, then Methylocaldum alone dominated the methanotrophic community. Community comparison showed that total bacterial and methanotrophic communities were temporally stable after the initial growth period. Quantitative PCR showed that methanotrophic density increased by the first 3-4 weeks, then leveled off over 120 days. Tobermolite can provide a special habitat for the selective growth of methanotrophs, resulting in a rapid acclimation. It also allows microbial community and methanotrophic density to remain stable, resulting in a stable methane biofiltration.