The goal of the study was to test 3 parameters and to evaluate their importance on the start-up of aerobic granular biofilm reactors. Aerobic granules are bacterial aggregates that have a minimum size of 0.2 mm. They can treat the influent COD, phosphate and nitrogen. The 3 tested parameters were the COD concentration, the Dissolved Oxygen (DO) concentration and the addition of Allylthiourea (ATU). These parameters were tested with a Hadamar matrix of experiment. We made 4 experiments with 4 strategies that combine the parameters in different manners. For each parameter two values had to be defined. The COD influent concentration was either in constant high concentration or in specific concentration. The specific COD concentration adapted the influent to the anaerobic carbon consumption of the biomass. The DO concentration was either with constant high value or with pseudo anoxic phases aeration. The pseudo anoxic phases aeration is a step aeration alternating high and low DO concentrations. ATU was in some strategies added at the begging of the experiment. Only 2 of the 4 experiments reached the wanted criteria in the given period. The criteria were defined related to the COD, P, NH4 and N-total removal as well as the granulation. The analyses of the Hadamar matrix gave the following results. The COD removal was mostly influenced by the COD influent concentrations. The P removal was also principally influenced by the COD concentrations which can influence the growth of Phosphate Accumulating Organisms (PAO). The N removal (NH4 and N total) was favoured by the absence of ATU. Finally, the granulation was also mostly influenced by the COD load. The granulation was obtained in the same time range then all the removal criteria.