Basic assessment of microbial dynamics in large- and small-scale biofilters

Treating exhaust gas from biogas plants is commonly done using biofilters composed of different filter materials. Immobilized on these filter materials microbes can convert less desirable exhaust gas components into more wanted ones. The evaluation of the performance of those filters based on microbial data is, however, difficult due to a lack in data regarding microbial colonisation of these filter materials. Thus, in the present study microbial abundance and microbial community composition in large- and small-scale biofilters was evaluated using both, cultivation dependent and independent approaches. Large-scale biofilters showed a similar total abundance of bacteria irrespective of the filter material and the water content of the biofilter. In contrast, fungal and yeast abundance was impacted by both, filter material (bark mulch or coconut fibre) and water content. In small scale biofilters (composed of bark mulch) the water content impacted microbial abundance. While a water content of 90% led to a similar development of bacterial and fungal/yeast abundance, 70% water content caused an asynchronous increase in abundance. Analysis of small-scale biofilters revealed an acidotrophic bacterial community including potential methanotrophs.