This study demonstrates the fundamental differences in fouling development and mechanisms of unfiltered and 0.45 µm pre-filtered water samples on ceramic membranes. Robust characterization of the feed waters was conducted using gravimetric analysis, optical methods and modeling techniques. UV₂₅₄ removal and suspended solids (SS) for the unfiltered samples presented a strong correlation (R² = 0.87). Further, SS exhibited strong correlations with fluorescent fractions (R² = 0.82; 0.81 and 0.74 for C1; C2 and C3, respectively). This observation confirmed the significance of inorganic particles in the development of a combined fouling layer with fluorescent organic components. The fouling development rate for water sampled from Plattenburg Bay (PL) was higher than the rest of the 0.45 µm pre-filtered samples. This was attributed to the low conductivity (175 µS.m^-1) of the water sample, translating to a low ionic strength environment. Samples collected from Hermanus River (HL) and Lepelle River (OL) had similar SS quantity (87.6 mg/L and 88.4 mg/L, respectively), and modified fouling index (MFI) values for raw samples were 6625 and 8060 s/L², respectively, despite a very large difference in the content of organic matter (22.67 mg/L.C and 9.81 mg/L.C). This could be due to organic matter attaching onto the surface of particles and reducing the adsorption of NOM within membrane pores and/or onto the membrane active layer. This study demonstrated the extent of in situ background electrolytes, foulant concentration, foulant-foulant interactions, foulant-membrane interaction and physicochemical properties of feed stream on fouling development and mechanisms.