The conventionally treated oil refinery wastewaters contain about 20 m
g/l total hydrocarbons and 30 mg/l suspended solids sloughed from a bi
ological reactor. The new European standards will require less than 5
mg/l total hydrocarbons and less than 10 mg/l suspended solids. Such s
tandards could be met by an ultrafiltration treatment. The M9 Carbosep
membrane was selected after it proved to be a total barrier for the h
ydrocarbons of a synthetic emulsion while ensuring the higher flux. Th
e importance of the temperature is emphasized as it determines the dro
plet size distribution. The major limiting processes conditioning the
fouling are evidenced and explained by the mean droplet size and the s
ize distribution. The fouling is then quantified and linked to the ope
rational parameters. A relationship for the limiting flux is fitted to
the experimental data.