Methanogenic community dynamics in continuous mode of anaerobic digestion treating swine wastewater

Two-stage Continuous Stirred-Tank Reactors treating swine wastewater were operated for more than 540 days, to evaluate the process performance and methanogenic population dynamics. A real-time quantitative PCR (QPCR) was used to detect and quantify the 16S rRNA gene concentrations of three methanogenic orders. Extended intervals of consistently stable wastewater treatment with a wide range of twelve hydraulic retention times (HRTs), from 25 to 3 days, were sustained. Methanomicrobials, Methanosarcinales and Methanobacteriales consecutively took the dominant place in the digester with different HRT ranges (i.e., 25 - 15, 15 - 8 and 8 - 3 days). Canonical Correspondence Analysis (CCA) indicates that the methanogenic reactor influent ammonia flux and propionic acid flux were the major contributors for the methanogenic population dynamics. CCA also exhibit that MMB and MSL have positive relationship with methane production and MPR, however in our analysis, we assume that it was the sustainable abundance of MSL in the reactor that contributes the substantive and rapid methane production rather than the predominant methanogen occurred in certain HRT range.