A 3 m3 pilot UASB reactor was operated with malting wastewater. In order to find the aggregation characteristics, the sludge concentration profile was determined throughout time. Reactor behaviour concerning the physical properties of the sludge can be evaluated using this procedure. Moreover, organic load per VSS can be calculated from this profile. The organic load based per VSS is more accurate as a design parameter than the volumetric load. Under the study conditions imposed the COD removal efficiencies achieved were about 85%. Organic loads of 0.6-0.7 kg COD/(kgVSS.d) were reached. After operating at 30°C, temperatures of 28°C and 15°C were tested, showing no decrease in COD removal efficiency. At week 15 the presence of granules was verified, and after that, sludge concentrations of 30-35 kg VSS/m3 were measured at the bottom of the reactor. The SVI of the granular sludge decreased to values below 20 mL/gVSS. The settlement velocity was 10 m/h, which is much greater than the recommended values for the settlement zone; therefore, no problems are to be expected in the settler regarding the sludge sedimentation. The biomass yield coefficient obtained was 0.10 gVSS/gCOD in agreement with literature values for brewering effluent.

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