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

Abstract

Treating NH3-loaded gases is necessary for improved livestock management. Nitrification, the sequential oxidation of NH3 to NO3− via NO2−, is an important microbial process for effective long-term NH3 removal. Denitrification, a microbial respiration process that reduces NO3− and NO2− to N2 under anaerobic conditions, can also contribute to nitrogen conversion in biofiltration systems. Understanding these microbial processes is imperative to control NH3 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 fullscale 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 NH3 oxidization. These findings will improve our understanding of microbial fluctuations and the complex behavior of nitrifiers and denitrifiers within an NH3-loaded biofiltration system.