Recilence evaluation to overloading feed disturbance in thermophilic anaerobic digestion

Abstract

Anaerobic digestion is a biological process that involves different groups of microorganisms that interact in equilibrium to degrade organic matter. It has been used as effective technology in residual treatment for the recovering energy implied. The stability of process can be disrupted by changes in composition feed, overloading rate, hydraulic retention time, and it is characterize by accumulation of intermediate products as result of overgrowth and inhibition between groups of microbial community. Resilience is known as a recovery process after disturbance and it can has multiple routs. This study aims at knowing the resilience of anaerobic digestion system after receiving overloading feed pulses of different magnitude. Five anaerobic digesters of 10 liters of work volume and 20 days of HRT were used, feeding with poultry litter and located at West Virginia State University. One digester was used as control and the other four were disturbed increasing the feed concentration in terms of chemical oxygen demand (COD). Changes were monitored by volatile acids (VA) accumulation, chemical oxygen demand COD, nitrogen-ammonia, and methane content. Additionally, DNA samples were taken to analyze changes in microbial structure caused by disturbance. For DNA samples analysis, 454-pyro sequencing was used. The results observed were accumulation of VAs, increase of COD, methane showed a stimulus after the stronger pulse. Volatile fatty acids were accumulated as consequence of overloading. Microbial structure change as response to disturbance, Clostridia class was a representative class to increase the percentage when the maximum overloading feed pulse take place. The most representative orders were MBA08, SHA-98, Clostridiales, BSA2B-08 and OPB-54 from Clostridia Class. Followed by Thermotogales, Bacteriodales, and Synergistales.