Anaerobic digestion optimisation for sanitisation
Efforts toward optimization of anaerobic digestion (AD) have typically focused on biogas yield, yet improvements in pathogen load reduction may potentially negate the need for a costly pasteurization step. Hence, optimization of AD for sanitization as well as improved biogas output is desirable. Triplicate 10-L CSTR bioreactors were fed with a combination of slurry and fats, oils and grease (FOG) for 240 days. The bioreactors were initially operated on a 5-day feeding regime, which was switched on Day 99 to a 3-day feeding regime. All other conditions were maintained. This change resulted in an initial build-up of COD, with sCOD in the digestate increasing to an average of 13±0.4 g L-1 between Days 135 and 150 and tCOD in the digestate averaging 81±2.4 g L-1 during the same period. Additionally, the change in feeding regime resulted in the required reduction in coliform and E. coli numbers to satisfy EU sanitization standards. Hence, DNA was extracted from samples from the three phases for shotgun metagenomics. The results of this work indicate the possibility for manipulation of AD for improved sanitisation and biogas production and highlight the need to better understand the important role of microbial dynamics in AD systems.