Bioaugmentation Can Increase Steady-State Methane Production and COD Reduction in Anaerobic Digesters

Bioaugmentation was investigated to improve anaerobic digesters at steady state. Two digester sets (Sets A and B), were seeded with different inocula and operated (HRT = 10 days, OLR = 4 g-COD/LR-day). Bioaugmented digesters received 50 mg-VSS/LR-day of an active culture enriched for H2/CO2 and propionate utilization. The bioaugmented Set-A digesters showed a significant increase in methane production and COD reduction, whereas Set-B digesters did not. The specific methanogenic activity (SMA) of seed used to start Set-A was lower than that used to start Set-B. In addition, initial SMA screening of each inocula mixed with enrichment culture indicated Set-A inoculum would benefit from bioaugmentation, whereas Set-B would not. Therefore, low SMA may indicate that bioaugmentation is beneficial and initial SMA screening can predict bioaugmentation outcomes. In conclusion, bioaugmentation can result in higher methane production and lower effluent COD at steady state; however, success depends on the initial digester methanogenic community.