Comprehensive analysis of microbial dynamics linked with the reduction of odorous compounds in a full-scale swine manure pit recharge system with recirculation of aerobically treated liquid fertilizer.

It is believed that the generation of odorous materials in manure-slurry pits during the storage can be reduced by recirculating aerobically treated liquid fertilizer (ATLF) to a manure-pit recharge system (PRS). However, the biological mechanisms for reduction of those problematic compounds remain poorly understood. In this study, the links between microbial evolution and changes in chemical composition and odorous compounds were analyzed where swine-manure slurry was stored in a full-scale PRS. Some beneficial microorganisms were successfully established in the PRS. This resulted in the accumulation of fewer undesirable chemical components and lower amounts of odorous compounds compared to those in a conventional swine-manure slurry pit (the control). Decrease in the volatile fatty acids (1387-8478 mg/L → 306-1258 mg/L) and NH3 (3387-4300 mg/L → 85-200 mg/L) in the PRS was mainly due to the development of a key community that included a mix of aerobic, anaerobic fermentative, nitrifying (0.1-0.6%) and denitrifying (1.7-3.5%), and methanogenic microorganisms (2.1-4.2%). Meanwhile, the generation of greater amounts of H2S (12-290 mg/L → 61-1754 mg/L) was found in the PRS, which condition was supported by the increased proportion of sulfate-reducing bacteria (0.5-3%). To the authors' best knowledge this is the first study comprehensively analyzing microbial dynamics linked with the reduction of odorous compounds in the full-scale PRS in response to recirculation of ATLF.