Management of reoccurring process disturbances in agricultural digesters through post digestion, total solid adjustment and recirculation

The aim of this study was to elucidate mechanisms underlying perturbation of agricultural waste (AW) digesters by assessing the process response to operational remedies in relation to microbial community dynamics. Two serial continuously stirred tank reactors, namely as main digester (MD) and post digester (PD), simulating the operation of an existing full-scale biogas plant experienced process perturbations, in forms of declined biogas production, pH variations and accumulation of intermediate degradation products. To remedy this, different operational remedies were evaluated including, alternation of feeding intervals, recirculation of the liquid, and whole digestate. Recirculating part of digestate from PD stream to the MD resulted an increased in overall process stability.