A Novel Approach of Preserved, Dried Methanogenic Biomass for Bioaugmentation and Standard Laboratory Applications

It would be beneficial if active, freeze-dried methanogenic biomass (FDMB) was available to improve full-scale anaerobic treatment systems or perform standard laboratory tests in the same way aerobic microbes are commercially available to enhance nitrification or as inoculum for BOD testing. In the work reported herein, methanogenically active biomass was freeze-dried using a bench top freeze-dryer. The acetoclastic and hyrogentophic methanogenic activity of FDMB was determined using specific methanogenic activity testing for acetate and hydrogen. The methanogenic community after freeze-drying was analyzed using real-time qPCR for the mcrA gene. FDMB was used to bioaugment upset lab-scale anaerobic digesters and to perform standard anaerobic laboratory tests. Approximately 42 to 65 % of the specific methanogenic activity was preserved after freeze drying which was supported by qPCR results that 60% of the mcrA gene and transcript copies were recovered after freeze drying. Bioaugmented upset anaerobic digesters recovered 1.5 SRTs sooner than non-bioaugemented digesters, and methane production was 17 to 24% higher in bioaugmented digesters. BMP test results using FDMB resulted in a 10-day lag before biogas production started. However, BMP values were identical to those obtained when wet biomass was used as inoculum. Therefore, FDMB biomass could be a feasible option for bioaugmentation and standard laboratory testing.