In this study the evaluation of nitrogen removal in wastewater from a meat products processing company was performed, using a Sequencing Batch Reactor (SBR) at pilot scale. The phases of the SBR operation were: filling, reaction (aeration and intermittent anoxia), sedimentation and discharge. In each of these phases analyses of ammonium (NH(4)(+)), nitrite (NO(2)(-)), nitrate (NO(3)(-)), pH and dissolved oxygen (DO) were carried out to monitor the process of nitrification-denitrification. The results showed that stage IV had the best performance (2.49 g COD(F)/L d and 1.02 g NH(4)(+)-N/L d) with a NH(4)(+)-N removal of 71%. The transformation of much of the NH(4)(+)-N to gaseous nitrogen was confirmed, with the concentration of NO(2)(-)- N and NO(3)(-)-N increasing during the reaction phase but decreasing in the effluent due to its transformation to gaseous nitrogen. (C) 2010 Elsevier Ltd. All rights reserved.