In this study, a quick and robust method using automated image analysis was suggested to analyze the size and the shape of biological granules. To verify this method, 6917 hydrogen (H2)-producing granule samples were scrutinized without any special equipment, and the results were statistically (ANOVA, t-test) interpreted at 95% confidence level to examine the effects of low-strength (LS) ultrasonication and effluent recirculation on the granular size and morphology. The fluctuations of both the size and roundness were identified even under same operating conditions. Both LS ultrasonication and effluent recirculation led to a 14% larger mean granular size. In contrast, LS ultrasonication but not recirculation significantly affected the roundness of H-2-producing granules. The findings of this study successfully demonstrated the feasibility of the proposed methodology, which can be a useful tool to analyze different types of biogranules. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.