In order to assess the applicability at industrial-scale of the anaerobic ammonium oxidation (Anaminox) process it is necessary to study the toxic effects on the maximum specific Anammox activity (SAA) of different compounds commonly present in industrial effluents. The present study was focused on the application of batch tests to determine the maximum SAA in different conditions. The batch tests were based on the measurement of nitrogen gas production. The initial conditions for the tests established to obtain the maximum value of the measured SAA were: 30 degrees C, pH 7.8, shaking speed 150 rpm, and biomass concentration 1 g VSS L-1. The accuracy of the method was evaluated by mass balances of the nitrogen compounds and the obtained errors were smaller than 7%. Neither the initial biomass concentrations tested (0.5-2.0 g VSS L-1) nor the S-0/X-0 ratio between 0.018 and 0.140 g NO2--N g VSS-1 had significant influence on the estimated SAA. The addition of a second feeding tended to increase it around 20 +/-10%. The developed method is afterwards applied to the study of the inhibition caused on the Anammox process by different compounds (NH4+, NO2-, NO3-, NaCl, SO42-, S2-, flocculant, etc.). The effects of chloramphenicol (inhibitor of the denitrifying process) and allylthiourea (inhibitor of the nitrifying process) were tested in order to be used to distinguish between the Anammox activity from nitrifying and denitrifying activities. The developed batch experiments were found suitable to establish not only the maximum SAA of certain sludge but also the inhibitory effects of certain tested compounds. (c) 2006 Elsevier Inc. All rights reserved.