Modeling granule development and reactor performance on anaerobic granular sludge reactors

• A comprehensive dynamic model of anaerobic granular sludge reactors is proposed.
• The model couples the ADM1 with mass-transfer phenomena and hydrodynamic behavior.
• The model simultaneously predicts granule development and reactor performance.
• Model validation with experiences in an expanded granular sludge blanket reactor.
• A dynamic model using a granule size distribution was also proposed.

In this study, a dynamic model for up-flow anaerobic granular sludge reactors capable of simultaneously predicting the granule development (size and composition) and the reactor performance was developed, implemented and validated. The model couples the anaerobic digestion model No.1 (ADM1), slightly adapted, with the reactor hydrodynamics and the mass transfer processes within the granule for soluble and particulate components. Granular development prediction was achieved by considering the kinetic processes and the advective flux for particulate components inside the granular matrix and particulate detachment in the granule surface. The model was implemented in Matlab software. Simulations accurately predicted the methane production rate and the granular size distribution of a bench-scale expanded granular sludge bed (EGSB) reactor treating synthetic sucrose based wastewater. Additionally, the model was successfully implemented, not only considering a mean granule size, but also including a granule size distribution. Results showed that considering the granule size distribution only affected the particulate concentration in the reactor outlet stream at the expense of highly increasing the computational cost for simulation.