No abstract

This study aimed to elucidate microbial community changes in response to an overloading of fats, oils, and grease (FOG) during anaerobic codigestion with municipal wastewater sludge. Two semicontinuous digesters, one control and one FOGfed codigester, were operated for over 300 days. Upon establishing a stable function, defined by consistent methane production over several solids retention times (SRT), the FOG codigester was overloaded, resulting in stalled methane production for a duration of approximately three SRTs. An increase in methane production relative to the stalled state characterized recovery following a period of batch operation, and normal function was subsequently maintained over several more SRTs. Time-series long-chain fatty acids (LCFA), volatile fatty acids (VFA), and methane analysis revealed palmitic acid accumulation as a bottleneck during the overloading event. Corresponding time-series metagenomic sequencing revealed changes in microbial community structure and potential function before, during, and after the overloading event and compared to the control digester. Abundance of central metabolism genes and stress response genes varied over time in the codigester compared to the control. Taxonomy and diversity analyses revealed that while the microbial community composition changed over time, the communities before the overloading event and after recovery were more similar to each other than to the community during the overloading event.