Efficient control of membrane fouling in low-pressure membrane filtration is still required; however, our current understanding of the fouling mechanism is insufficient, and little is known about the preferential deposition of foulants on membrane surface during filtration. In this study, the strength of attachment of different organics on polyvinylidene fluoride (PVDF) hollow fiber ultrafiltration (UF) membrane was investigated. Sodium alginate (SA), bovine serum albumin (BSA), and humic acid (HA) were examined as foulants representing polysaccharides, proteins, and humic substances, respectively, and their relative degree of fouling was monitored. An increasing amount of cleaning force was applied during a four-step rigorous cleaning protocol to extract foulants from the membrane surface. Liquid chromatography with organic carbon detector (LC-OCD) was applied to better characterize the nature of the extracted foulant layers; so to obtain a more advanced understanding of preferential deposition of fouling material on membrane surface. The results obtained in this study demonstrated that organics, mainly biopolymers and low molecular weight (LMW) neutrals, exhibited the highest affinities with the membrane, and consequently caused irreversible fouling. Furthermore, higher bulk organic concentrations in the feed may not be necessarily responsible for a greater extent of membrane fouling, due to possible foulant-foulant interactions, as demonstrated by this initial assessment through LC-OCD.