Nitrogen Fate and Adaptation of the Microbial Community Responsible for Ammonia Removal in a Biofilter Treating Waste Gas from Livestock Manure Composting

Treating NH 3 -loaded gases is necessary for improved livestock management. Nitrification, the sequential oxidation of NH 3 to NO 3 − via NO 2 − , is an important microbial process for effective long-term NH 3 removal. Denitrification, a microbial respiration process that reduces NO 3 − and NO 2 − to N 2 under anaerobic conditions, can also contribute to nitrogen conversion in biofiltration systems. Understanding these microbial processes is imperative to control NH 3 removal better and achieve nitrogen balance in biofiltration. In this review, we discuss the functions and compositions of the microbial community responsible for nitrification and denitrification in a biofiltration system, along with the relationship between these processes and the nitrogen mass balance. Our results indicate that both nitrification and denitrification could be achieved by a consortium of microbes well adapted to the ecosystem in a full-scale biofilter. Moreover, the microbial community was controlled by substrate availability. Nitrogen removal potential was up to 39% in a laboratory-scale biofilter with intermittent water recirculation, and the unknown nitrogen loss was considered mainly denitrified. Under gradual accumulation of nitrogenous compounds, the gamma proteobacterial group contributes to NH 3 oxidization. These findings will improve our understanding of microbial fluctuations and the complex behavior of nitrifiers and denitrifiers within an NH 3 -loaded biofiltration system.