Poultry slaughterhouses discharge very high amount of wastewaters and these wastewaters can be treated successfully at a very low cost using anaerobic treatment. in this study, the Static Granular Bed Reactor (SGBR), a newly developed anaerobic process which is fully anaerobic granule, and another Static Granular Bed Reactor containing both anaerobic granular biomass and non-granular biomass were employed for the treatment of poultry slaughterhouse wastewater. The objective of the use of two reactors having different types of anaerobic biomass is to evaluate whether anaerobic sludge could be used effectively instead of anaerobic granule, which is much more difficult to obtain than the other during the start up period. Average COD removal efficiencies were greater than 95% for both of the reactors. Furthermore, Grau second-order and modified Stover-Kincannon models were successfully used to develop a kinetic model of the experimental data with a high correlation coefficient (R(2) > 0.95). (c) 2009 Elsevier Ltd. All rights reserved