The use of a well-chosen pretreatment system is a key element to avoid fouling in nanofiltration (NF). Among the different possibilities for pretreatment systems, microfiltration (MF) emerges as the most compatible with NF. This article explores the influence of a MF pretreatment by comparing the performance of three NF membranes (UTC-20, Desal 51 HL, and NF-PES-10) with and without MF pretreatment for the purification of two types of wastewaters from the brewery of Westmalle, Belgium. The wastewaters studied were bottle-rinsing water and rinsing water from the fermentation tanks, respectively. The results indicate that MF pretreatment had no influence for UTC-20, a considerable influence for Desal 51 HL, and a dramatic influence for NF-PES-10. No correlation with the membrane roughness, determined by AFM, was found, but the results support the assumption that particle fouling is mainly determined by the hydrophobicity of the membrane. The effect of pretreatment was largest for the hydrophobic NF-PES-10 membrane, smallest for the hydrophilic UTC-20 membrane, and intermediate for Desal 51 HL. The effect of the composition of the feed solution was considerably smaller than the effect of the membrane used, although, small differences where found depending on the size and concentration of the particles.