Effect of Bioaugmentation on Start-Up Phase of Anaerobic Digestion at High Organic Loading Rate: Bioreactor Performance and Microbial Community

Abstract

Propionate-degrading methanogenic cultures were introduced to enhance the start-up of anaerobic digestion (AD) of food waste at a high organic loading rate (OLR) of 3.0 g VS L-1 d-1, and the efficiency of different bioaugmentation strategies were investigated. The results demonstrated that bioaugmentation significantly improved the start-up efficiency and enhanced the methane production. Specifically, higher dosage and frequency of bioaugmentation had a positive effect on the performance of the AD reactors. Among three bioaugmented reactors, the reactor with a bioaugmentation strategy of 0.675 g VS L-1 of bioaugmentation seed added every 5 days during the first hydraulic retention time (HRT) performed the best and remained relatively stable for the next three HRTs without bioaugmentation. The 16S rRNA gene sequencing analysis revealed that Methanothrix predominated in bioaugmented reactors. A large proportion of Methanothrix accompanied by a small proportion of Methanosprillum played a key role in volatile fatty acid degradation and contributed to the successful start-up and long-term stability of AD at a high OLR.

Keywords: High organic loading rate, Anaerobic digestion, bioaugmentation, propionate degradation, Methanothrix