Ceramsite-mediated enrichment of functional bacteria in biofilters: a novel strategy for simultaneous ammonia and hydrogen sulfide removal in livestock odor control.

Livestock farming odors, particularly those caused by ammonia and hydrogen sulfide, pose significant environmental and public health challenges. This study evaluates the performance of a biofilter enhanced with five composite fillers to simultaneously remove ammonia and hydrogen sulfide from chicken manure treatment emissions. Systematic evaluation of different fillers (bark, ceramsite, volcanics, polyurethane pellets, and ceramsite + volcanics) and optimization of the spray rate (24 ∼ 168 L/h) were performed. This study demonstrates that the ceramsite composite filler achieved optimal removal efficiencies of 85 % for ammonia and 58 % for hydrogen sulfide under short empty bed residence time of 15 s. The porous structure and Fe-O functional groups of the ceramsite filler enrich core components of functional bacterial communities, particularly Proteobacteria and Bacillus, which drive nitrogen and sulfur transformations via nitrification-denitrification and sulfide oxidation pathways. The economically optimal spray rate was 120 L/h, balancing removal efficiency (88 % for ammonia; 59 % for hydrogen sulfide) with operational costs. The random forest machine learning model revealed that the core genera, (e.g. Paenibacillus, Bacillus and Nitrospira), covering all 13 functions of the nitrogen and sulfur transformation pathways, are enriched in the biofilter system. We show that low-abundance, but potentially high-activity taxa (e.g., Nitrospira) play important roles in the stable operating periods of biofilters. This study demonstrates that ceramsite composite fillers offer a practical, mechanism-driven solution for enhancing simultaneous ammonia and hydrogen sulfide removal in livestock odor control systems.