An Innovative Approach for Modeling Aerobic Granular Sludge Processes

An innovative biofilm model has been developed that allows modeling of a granular sludge sequencing batch reactor (GSBR) in a single tank without the need for a separate variable volume tank and a recycle stream. The model has a variable volume, supports separate or simultaneous feeding and effluent discharge, predicts the biofilm thickness without being constrained by a maximum thickness, supports non-uniform biofilm geometries, and models the impact of mixing intensity on biofilm detachment. The model has been calibrated and validated using data from lab-scale and pilot-scale reactors respectively and has demonstrated excellent predictive capabilities. Model calibration only required specification of the biofilm surface area within the reactor, the biofilm density, and the biofilm erosion velocity which were determined from the measured characteristics of the granules. This is significant because it enables engineers to use the model in the design of aerobic granular sludge processes which are becoming attractive due to their ability to intensify treatment.