A dimensionless approach was used to model the granule size variation in upflow anaerobic sludge blanket (UASB) reactor under different operating condition like organic loading rate, operating time, gas production rate, volatile suspended solids, suspended solids, upflow velocity, polymer loading, sludge volume index and effluent COD concentrations. Present study examines mathematically the effect of introducing polymers to enhance the granule size development in a UASB reactor especially in treatment of low strength wastewater in UASB reactor. The experimental results of investigators on different operating conditions were collected and subjected to dimensionless and non-linear regression analysis to model the enhancement of granule size in UASB reactor. The results using the dimensionless approach and the non linear regression show that better prediction of granule size variations for the data set based on the statistical estimates, errors and a satisfactory coefficient of determination (R2-values). The dimensionless approach of the present study can be successfully used to predict the granule size variations in UASB reactor
