Suitability of dust and bioaerosols from a pig stable as inoculum for biological air filters

[Abstract] Biofiltration for removing ammonia and odour compounds from ventilation air of pig stables is a promising approach. In order to reduce the time for starting up a well-functioning biofilter a good inoculum suited for the environment is needed. In this study the microbial identity and quantity of dust and bioaerosols coming from a pig stable were analyzed for its suitability as inoculum. Inoculation of biofilters with dust had similar good ammonia removal capabilities as biofilters inoculated with activated sludge, although analysis of the microbial dust community revealed clear differences. The organic fraction of the dust particles seems to be important for mediating biofilm development on the filter material

Primary settling changes the microbial community of influent wastewater to wastewater treatment plants

The continuous immigration of bacteria in influent wastewater strongly impacts the microbial community of activated sludge (AS) in wastewater treatment plants (WWTP), both in terms of species composition and their abundance. Therefore, it is of interest to elucidate the route of immigrating bacteria into the biological tanks, including the effect of primary settlers. These are commonly used pretreatment units that can possibly selectively increase or reduce the relative abundance of certain bacteria. Species-level identification of the microbial composition of influent wastewater before and after primary settling was carried out in four full-scale municipal WWTPs biweekly over one year by 16S rRNA gene amplicon sequencing. Overall, 37–49% of incoming COD was removed in the primary settlers. Most genera and species were present in the wastewater to all four plants and the trend of these were investigated across the primary settlers. Approximately 50% of the genera had the same trend across at least three WWTPs. Few genera significantly increased in relative read abundance (3.7%) after settling, while 22.3% showed a significant reduction in relative abundance. We investigated process-critical species in AS, such as known nitrifiers, polyphosphate-accumulating organisms, and filamentous bacteria. Most taxa were affected similarly in all WWTPs including multiple genera involved in bulking in AS. However, some genera, e.g., important polyphosphate-accumulating bacteria, had inconsistent trends across WWTPs, suggesting that the characteristics of the wastewater are important for the trend of some bacteria through primary settling. In all cases, primary settling changed the microbial community of the influent wastewater, posing an obvious candidate for upstream control to optimize the assembly of the microbial communities in activated sludge.</p