Studies on the expansion characteristics of the granular bed present in EGSB bioreactors

Abstract

In this study, the expansion characteristics of an anaerobic granular bed in EGSB reactors based on terminal settling velocity study of the granules and the Richardson-Zaki equation (1954) have been investigated. The settling velocity study shows that the mean settling velocity of the granules is in accordance with the Allen formula because the settling process falls within the intermediate flow regime range (1 <110) rather than in the laminar flow regime range; the bed expansion study based on the above conclusion is found to be similar to that suggested by the Richardson-Zaki equation. The validity of the settling velocity model is verified by using the operating parameters of several full-scale anaerobic reactors with an average relative error of 3.77%, and the bed expansion data obtained from two laboratory-scale reactors are used to test the correlation with an average relative error of 2.64% and 4.57% respectively. Moreover, it could be a theoretical method to propose a suitable value of Vup during different operation periods of an EGSB system.